CCAPP AstroParticle Lunch

Here, members of CCAPP, Physics, and Astronomy get together to discuss papers and recent developments in high-energy astrophysics and astroparticle physics, in an informal setting over lunch. Please check the page for details regarding the next meeting.

Organizers:

Lucas Beaufore -- beaufore.2@osu.eduObada Nairat -- nairat.2@osu.eduPaarmita Pandey -- pandey.176@osu.edu

Fridays from 11:15 am - 12:15 pm (EDT)

Price Place (PRB) & VIA ZOOM

COMING UP:

11:15 am, Friday, March 1

Guest: Prof. Phil Hopkins (Caltech)

Galactic Cosmic-ray Scattering due to Intermittent Structures 

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PAST EVENTS:

11:15 am, Friday, February 23

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11:15 am, Friday, February 16

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11:15 am, Friday, February 9

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11:15 am, Friday, February 2

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Guest: Roshan Mammen Abraham (UC Irvine)


Title: “Neutrino Physics and Dark Matter Searches at the Forward Physics Facility at the LHC”

Abstract: The recent observation of collider neutrinos by the FASER collaboration highlights the potential the forward direction at the LHC has for neutrino physics. In the HL-LHC era, we expect a significant number of neutrinos in the forward direction, opening the way for precision studies using collider neutrinos at the proposed Forward Physics Facility (FPF). In this talk, I will present some phenomenological studies in this direction. i) The electromagnetic properties of neutrinos (magnetic moments, milli-charge, charge radius) have attracted significant interest recently. We make use of the enhanced neutrino flux expected in the HL-LHC era along with the sophisticated detectors at the FPF to constrain these properties, as well as the weak mixing angle. ii) If a new sterile state exists that couple to SM neutrino via the photon through a dipole portal, then it will also leave a signature in these detectors via up-scattering. This allows us to constrain the magnetic dipole moment interaction between SM neutrinos and this new sterile state. Furthermore, these neutrino detectors can also be used to probe some light dark matter models. We present some results in this direction.



11:15 am, Friday, January 26

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11:15 am, Friday, January 19

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11:15 am, Friday, January 11

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11:15 am, Friday, December 8th

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Guest:  Dr. Austin Cummings (Penn State University)

Title: Secondary Lepton Production, Propagation, and Interactions with NuLeptonSim

Abstract: Charged current interactions of neutrinos inside the Earth can result in secondary muons and {\tau} - leptons which are detectable by a large swath of existing and planned neutrino experiments through a wide variety of event topologies. Consideration of such events can improve detector performance and provide unique signatures which help with event reconstruction. In this work, we describe NuLeptonSim, a propagation tool for neutrinos and charged leptons that builds on the fast NuTauSim framework. NuLeptonSim considers energy losses of charged leptons, modelled both continuously for performance or stochastically for accuracy, as well as interaction models for all flavors of neutrinos, including the Glashow resonance. We demonstrate the results from including these effects on the Earth emergence probability of various charged leptons from different flavors of primary neutrino and their corresponding energy distributions. We find that the emergence probability of muons can be higher than that of taus for energies below 100 PeV, whether from a primary muon or {\tau} neutrino, and that the Glashow resonance contributes to a surplus of emerging leptons near the resonant energy. 


11:15 am, Friday, December 1st

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11:15 am, Friday, November 17th

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Two Guests!


Guest: Dr. Bei Zhou (Fermilab)

Paper: First Detailed Calculation of Atmospheric Neutrino Foregrounds to the Diffuse Supernova Neutrino Background in Super-Kamiokande


Guest:  Sayan Saha (graduate student at Indian Institute of Science Education and Research (IISER), Pune, India) 

Title: Optimal Estimators for Cluster Masses using CMB Lensing

Paper: Cluster profiles from beyond-the-QE CMB lensing mass maps

Abstract: Being the largest collapsed structures in the universe, clusters of galaxies offer valuable insights into the nature of cosmic evolution. What we're really curious about is figuring out how many of these clusters exist at different masses and ages (redshifts). But here's the catch: measuring their mass isn't straightforward. So, we use a cosmic 'weighing scale' that uses faint deflections (weak gravitational lensing) of the oldest light in the universe—known as the cosmic microwave background (CMB) —to find out how massive these clusters really are. In this talk, I'll unveil the power of the Maximum-a-posteriori (MAP) method, showcasing its enhanced precision in measuring cluster masses compared to traditional quadratic estimators (QE). I also show how the MAP estimator is able to mitigate the well-known bias in temperature QE, due to the strong non-Gaussianity of the signal at cluster centre, without any scale cut.


11:15 am, Friday, November 3rd

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11:15 am, Friday, October 27th 

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11:15 am, Friday, October 19th 

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Guest: Dr. Andrea Albert (Los Alamos National Laboratory)

Title: Searching for Dark Matter with Wide-field TeV Observatories

Abstract: One of the main ways to probe the particle nature of dark matter is to look for particles from DM interactions in space. TeV cosmic gamma rays are a powerful probe and wide field of view observatories play a key role. The High Altitude Water Cherenkov (HAWC) has been surveying the TeV sky for over 8 years and the next generation Southern Wide-field Gamma-ray Observatory (SWGO) is currently being planned. I will show results from DM searches with HAWC and the expected sensitivity of SWGO.

11:30 am, Friday, October 13th 

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Guest: Prof. Rouzbeh Allahverdi (The University of New Mexico)

Title: Probing GeV-scale Dark Particles by Neutron Stars

Abstract: I start by introducing minimal extensions of the Standard Model that involve new particles with baryon-number-violating coupling to quarks. After a brief review of the existing experimental bounds on these models, I mention some ongoing work that uses neutron star binaries to tightly constrain GeV-scale fermions. 




11:15 am, Friday, October 6t

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11:30 am, Friday, September 22nd

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11:30 am, Friday, September 15th

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11:30 am, Friday, September 8th

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11:30 am, Friday, July 21st

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Guest: Shirley Weishi Li (UC Irvine)

Title: Old Data, New Forensics: The First Second of SN 1987A Neutrino Emission

Abstract: The next Milky Way supernova will be an epochal event in multi-messenger astronomy, critical to tests of supernovae, neutrinos, and new physics. Realizing this potential depends on having realistic simulations of core collapse. We investigate the neutrino predictions of nearly all modern models (1-, 2-, and 3-d) over the first ≃1 s, making the first detailed comparisons of these models to each other and to the SN 1987A neutrino data. Even with different methods and inputs, the models generally agree with each other. However, even considering the low neutrino counts, the models generally disagree with data. What can cause this? We show that neither neutrino oscillations nor diferent progenitor masses appear to be a sufficient solution. We outline urgently needed work.



11:30 am, Friday, July 7th

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Guest: Federica Pompa (University of Valencia)

Title: Galactic cataclysm: Supernova neutronization burst to constraint neutrino mass

Abstract: Supernova (SN) explosions are the most powerful cosmic factories of all flavors, MeV-scale, neutrinos. Their detection is of great importance not only for astrophysics, but also to shed light on neutrino properties. Since the first observation of a SN neutrino signal in the 1987, the international network of SN neutrinos observatories has been greatly expanded, in order to detect the next galactic SN explosion with much higher statistics and accuracy in the neutrino energy-time-flavor space. In this contribution, I will discuss the constraints that we expect to achieve with next-generation neutrino experiments like DUNE and Hyper-Kamiokande, on the absolute value of the neutrino mass, obtained by considering the time delay in the propagation of massive neutrinos from production in the SN environment to their detection. Furthermore, the comparison of sensitivities achieved for the two possible neutrino mass orderings is discussed, as well as the effects due to propagation in the Earth matter.

Guest: Jorge Terol-Calvo (University of Valencia)

Title: Cosmology safe large neutrino masses 

Abstract: Cosmological constraints on the sum of neutrino masses can be relaxed by considering a scenario where the number density of active neutrinos is reduced, while the effective number of neutrino species is maintained by introducing a new component of dark radiation. In this talk, I'll present a UV model based on a U(1) symmetry in the dark sector, which can be either gauged or global, to realize this intriguing concept. The model employs the seesaw mechanism to generate neutrino masses and introduces O(10) generations of massless sterile neutrinos that contribute to the dark radiation component. This framework allows for accommodating active neutrino masses in the range of electron volts (eV), which aligns with the sensitivity range of the KATRIN experiment. We further discuss the phenomenology of the model and identify the parameter space that satisfies the constraints imposed by current observations. Our study sheds light on the interplay between neutrino masses, dark radiation, and the underlying U(1) symmetry in the dark sector, providing insights into the fundamental properties of neutrinos and their cosmological implications. 


11:30 am, Friday, June 30th

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Guest: Anna Suliga (UC Berkeley & UW-Madison)

Title: Distinctive nuclear signatures of low-energy atmospheric neutrinos

Abstract: New probes of neutrino mixing are needed to advance precision studies. One promising direction is via the detection of low-energy atmospheric neutrinos (below a few hundred MeV), to which a variety of near-term experiments will have much-improved sensitivity. Here we focus on probing these neutrinos through distinctive nuclear signatures of exclusive neutrino-carbon interactions -- those that lead to detectable nuclear-decay signals with low backgrounds -- in both neutral-current and charged-current channels. Here the neutral-current signature is a line at 15.11 MeV and the charged-current signatures are two- or three-fold coincidences with delayed decays. We calculate the prospects for identifying such events in the Jiangmen Underground Neutrino Observatory (JUNO), a large-scale liquid-scintillator detector. A five-year exposure would yield about 16 neutral-current events (all flavors) and about 16 charged-current events (mostly from νe+ν¯e, with some from νμ+ν¯μ), and thus roughly 25\% uncertainties on each of their rates. Our results show the potential of JUNO to make the first measurement of sub-100 MeV atmospheric neutrinos. They also a step towards multi-detector studies of low-energy atmospheric neutrinos, including with the goal of identifying additional distinctive nuclear signatures for carbon and other targets.


Guest: Victor Valera-Baca (NBI)

Title: Exploring neutrino--matter interactions at the EeV frontier

Abstract: Neutrino interactions with protons and neutrons probe their deep structure and may reveal new physics. The higher the neutrino energy, the sharper the probe. So far, the neutrino-nucleon (νN) cross section is known across neutrino energies from a few hundred MeV to a few PeV. Soon, ultra-high-energy (UHE) cosmic neutrinos, with energies above 100 PeV, could take us farther. So far, they have evaded discovery, but upcoming UHE neutrino telescopes endeavor to find them. I will present the first detailed measurement forecasts of the UHE νN cross section, geared to IceCube-Gen2, one of the leading detectors under planning. We use state-of-the-art ingredients in every stage of our forecasts: in the UHE neutrino flux predictions, the neutrino propagation inside Earth, the emission of neutrino-induced radio signals in the detector, their propagation and detection, and the treatment of backgrounds.




11:30 am, Friday, June 23rd

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11:30 am, Friday, June 16th

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11:30 am, Friday, June 9th

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11:30 am, Friday, May 26th

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Guest: Toni Bertolez-Martinez (Barcelona U)

Title: IceCube and the origin of ANITA-IV events

Abstract: Recently, the ANITA collaboration announced the detection of new, unsettling Ultra-High-Energy (UHE) events. Understanding their origin is pressing to ensure success of the incoming UHE neutrino program. In this talk, I will discuss the ANITA-IV events in contrast with the lack of observations in the IceCube Neutrino Observatory. I will introduce a general framework to study the compatibility between these two observatories both in the SM and Beyond Standard Model (BSM) scenarios.  Finally, I will discuss the constraints on BSM and highlight the importance of simultaneous observations by high-energy optical neutrino telescopes and new, UHE detectors to uncover cosmogenic neutrinos or discover new physics.


Guest: Stephan Meighen-Berger (U. Melbourne)

Title: Prometheus: An Open-Source Neutrino Telescope Simulation

Abstract: The construction of a worldwide network of gigaton-scale neutrino telescopes aims to address multiple open questions in physics, such as the origin of astrophysical neutrinos and the acceleration mechanism of high-energy cosmic rays. Besides astrophysics, neutrino telescopes probe center-of-mass energies similar to colliders, offering an additional window into high-energy particle interactions. Currently, there are no publicly available simulation tools for these detectors, leading to duplication in effort for each experiment and hindering the testing of theoretical models. While these detectors are built in ice or water at different locations, they operate on the same detection principle: Using multiple optical modules to detect Cherenkov photons emitted by charged particles. Using this, we developed Prometheus, an open-source simulation tool that offers a common simulation chain for all neutrino telescopes. It can inject neutrinos, propagate their interaction products, and model the amount of light reaching the optical modules of a user-defined detector in either ice or water. We will show its runtime performance, highlight successes in reproducing simulation results from multiple ice- and water-based observatories, and discuss simulation sets that we have made publicly available for various detectors.


11:30 am, Friday, May 19th

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Guest: Rasmi Hajjar (IFIC)

Title: Earth tomography with supernova neutrinos at future neutrino detectors

Abstract: Earth neutrino tomography is a realistic possibility with current and future neutrino detectors, complementary to geophysics methods. The two main approaches are based on either partial absorption of the neutrino flux as it propagates through the Earth (at energies about a few TeV) or on coherent Earth matter effects affecting the neutrino oscillations pattern (at energies below a few tens of GeV). In this talk I will focus on the latter approach focusing on supernova neutrinos with tens of MeV. Whereas at GeV energies, Earth matter effects are driven by the atmospheric mass-squared difference, at energies below ∼ 100 MeV, it is the solar mass-squared difference what controls them. Unlike solar neutrinos, which suffer from significant weakening of the contribution to the oscillatory effect from remote structures due to the neutrino energy reconstruction capabilities of detectors, supernova neutrinos can have higher energies and thus, can better probe the Earth’s interior. We revisit this possibility, using the most recent neutrino oscillation parameters and up-to-date supernova neutrino spectra. The capabilities of future neutrino detectors, such as DUNE, Hyper-Kamiokande and JUNO are presented, including the impact of the energy resolution and other factors. Assuming a supernova burst at 10 kpc, we show that the average Earth’s core density could be determined within ∼ 10% at 1σ confidence level, being Hyper-Kamiokande, with its largest mass, the most promising detector to achieve this goal.

11:30 am, Friday, May 5th

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11:30 am, Friday, April 28th

Guest: Anupam Ray (UC, Berkeley) 

Title: Going Underground or Listening to the Sky? 

Abstract: Dark Matter (DM) remains mysterious. Despite decades of experimental efforts, its microscopic identity is still unknown. Terrestrial detectors are placing stringent exclusions on various parts of the DM parameter space, however, there exist a few blind-spots. In this talk, I will demonstrate how existing GW detectors can be used to unravel the particle nature of DM. More specifically, by observing low mass black hole mergers, existing GW detectors can provide unprecedented sensitivity to the weakly-interacting heavy dark matter, a blind spot to the terrestrial DM detectors. I will also walk you through how continued existence of a variety of stellar objects can probe strongly-interacting heavy DM, a yet another blind spot. 

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11:30 am, Friday, April 21st

11:30 am, Friday, April 14th

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11:30 am, Friday, April 7th

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11:30 am, Friday, Mar 31st

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11:30 am, Friday, Mar 24th

Guest: Hidetoshi Omiya (Kyoto University)

Title: Impact of multiple modes on the evolution of self-interacting axion condensate around rotating black holes

Abstract: Ultra-light particles, such as axions, form a macroscopic condensate around a highly spinning black hole by the superradiant instability. Due to its macroscopic nature, the condensate opens the possibility of detecting the axion through gravitational wave observations. However, the precise evolution of the condensate must be known for the actual detection. For future observation, we numerically study the influence of the self-interaction, especially interaction between different modes, on the evolution of the condensate in detail. First, we focus on the case when condensate starts with the smallest possible angular quantum number. For this case, we perform the non-linear calculation and show that the dissipation induced by the mode interaction is strong enough to saturate the superradiant instability, even if the secondary cloud starts with quantum fluctuations. Our result indicates that explosive phenomena such as bosenova do not occur in this case. We also show that the condensate settles to a quasi-stationary state mainly composed of two modes, one with the smallest angular quantum number for which the superradiant instability occurs and the other with the adjacent higher angular quantum number. We also study the case when the condensate starts with the dominance of the higher angular quantum number. We show that the dissipation process induced by the mode coupling does not occur for small gravitational coupling. Therefore, bosenova might occur in this case.

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11:30 am, Friday, Mar 10th

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11:30 am, Friday, Mar 3rd

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11:30 am, Friday, Feb 24th

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11:30 am, Friday, Feb 17th

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11:30 am, Friday, Feb 10th

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11:30 am, Friday, Feb 3rd

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11:30 am, Friday, Jan 27th

Guest: Christopher Cappiello (Queen's U)

Title: An Analytic Approach to Light Dark Matter Propagation

Abstract: If dark matter interacts too strongly with nuclei, it could be slowed to undetectable speeds in Earth's crust or atmosphere before ever reaching a detector. For sub-GeV dark matter, analytic approximations appropriate for heavier dark matter fail, necessitating the use of computationally expensive simulations. We present a new method of modeling attenuation of light dark matter in the Earth, based on the approximation that the scattering is isotropic in the lab frame. We show that this approach agrees well with Monte Carlo results, and can be much faster when the number of scatterings becomes large, as the runtime for Monte Carlo methods increases exponentially with cross section. We use this method to model attenuation for sub-dominant dark matter--that is, particles that make up a small fraction of the dark matter density--and show that previous work on sub-dominant dark matter overestimates the sensitivity of direct detection experiments.

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11:30 am, Friday, Jan 20th

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11:30 am, Friday, Jan 13th

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11:45 am, Friday, Dec 16th

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11:45 am, Friday, Dec 9th

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Guest: Alejandro Ramirez

Title: Applying Noble Liquid Particle Detection in Nuclear Imaging: Positron Emission Tomography

Abstract: In the field of astroparticle physics, noble liquids such as Argon and Xenon are widely used in underground particle detectors searching for candidate dark matter particles. They offer a variety of advantages over solid, room temperature scintillators and therefore these liquid scintillators can be utilized in other fields of research such as medical imaging.

Positron Emission Tomography (PET) is used to observe metabolic processes within patients. It works by reconstructing the annihilation origin of incident gamma rays produced by a positron emitting tracer. However, inefficiencies of current PET technology, such photomultiplier tubes, can result in poor imaging. We propose 3Dπ: a full body, Time of Flight (TOF) PET scanner using Silicon Photomultipliers (SiPM) coupled with a xenon-doped Liquid Argon (Lar+Xe) scintillator. We simulated this design using Geant4 while following the National Electrical Manufacturers Association's evaluation tests for performance assessment. We will present results that highlight a 200-fold increase in sensitivity, spatial resolutions comparable to commercial PET scanners and produce PET images from 15-30 second scans faster than traditional 30-35-minute scans. Further studies will involve optimizing the layer thickness of Lar+Xe. With this scintillator and SiPMs, we can use the precise TOF info of gamma rays to improve the localization of individual positron annihilations and provide low-dose PET scans for patients who may be at high risk for exposure to radiation.

11:45 am, Friday, Dec 2nd

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11:45 am, Friday, Nov 18th

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Guest: Pawan Dhakal

Title: New Constraints on Macroscopic Dark Matter Using Radar Meteor Detectors

Abstract: We show that dark-matter candidates with large masses and large nuclear interaction cross sections are detectable with terrestrial radar systems. We develop our results in close comparison to successful radar searches for tiny meteoroids, aggregates of ordinary matter. The path of a meteoroid (or suitable dark-matter particle) through the atmosphere produces ionization deposits that reflect incident radio waves. We calculate the equivalent radar echoing area or `radar cross section' for dark matter. By comparing the expected number of dark-matter-induced echoes with observations, we set new limits in the plane of dark-matter mass and cross section, complementary to pre-existing cosmological limits. Our results are valuable because (A) they open a new detection technique for which the reach can be greatly improved and (B) in case of a detection, the radar technique provides differential sensitivity to the mass and cross section, unlike cosmological probes.

11:45 am, Friday, Nov 4th

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Guest: Joaquim Iguaz (LAPTh, CNRS)

Title: Are PBHs everything everywhere all at once? Astrophysical and cosmological signatures of PBHs

Abstract: In recent years, Primordial Black Holes (PBHs) have been presented as extremely versatile objects providing a unique probe of the early Universe, gravitational phenomena, high energy physics and quantum gravity. Of particular interest is the role of PBHs as a non-particle candidate for the dark matter (DM). Although most of the PBH DM parameter space is tightly constrained, the asteroid mass range is still potentially viable. The lower end is accessible via high-energy astrophysical probes, sensitive to their Hawking evaporation spectrum. In the first part of the talk, I will revisit the constraints on evaporating PBHs from both the isotropic X-ray and soft γ-ray background, and the diffuse soft γ-ray emission towards the inner Galaxy as measured by INTEGRAL, setting the strongest limit on PBH DM for masses up to 4×10^17 g. The interest for PBHs has also been revamped in the light of recent LIGO/Virgo measurements of coalescing black hole binaries with typical masses of tens of M⊙. The best-motivated scenario for a sizable PBH contribution to such events invokes the QCD phase transition, which naturally enhances the probability to form PBH with masses of stellar scale. In the second part of the talk, I will reconsider the expected mass function associated not only to the QCD phase transition proper, but also the following particle antiparticle annihilation processes, and analyse the constraints on this scenario from a number of observations. We find that the scenario is not viable, unless ad hoc features in the power-spectrum are introduced by hand. Despite these negative results, we note that a future detection of coalescing binaries involving sub-solar PBHs has the potential to check the cosmological origin of SMBHs at the e± annihilation epoch, if indeed the PBH mass function is shaped by the changes to the equation of state driven by the thermal history of the universe.


Guest: Christopher Cappiello (Queen's U)

[https://arxiv.org/abs/2210.09448]

Title: Dark Matter from Monogem

Abstract: As a supernova shock expands into space, it may collide with dark matter particles, scattering them up to velocities more than an order of magnitude larger than typical dark matter velocities in the Milky Way. If a supernova remnant is close enough to Earth, and the appropriate age, this flux of high-velocity dark matter could be detectable in direct detection experiments, particularly if the dark matter interacts via a velocity-dependent operator. This could make it easier to detect light dark matter that would otherwise have too little energy to be detected. We show that the Monogem Ring supernova remnant is both close enough and the correct age to produce such a flux, and thus we produce novel direct detection constraints and sensitivities for future experiments.



PAST EVENTS

11:45 am, Friday, Oct 28th

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11:45 am, Friday, Oct 21st 

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11:45 am, Friday, Oct 6th 

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Guest: Gonzalo Herrera (TUM)

Title: Neutrino and gamma-ray attenuation by dark matter spikes    

[https://arxiv.org/abs/2209.06339]

Abstract: 

In this talk, I will discuss the attenuation of high energy neutrinos and photons produced in a blazar when they propagate through the dark matter spike around the central black hole and the halo of the host galaxy. In particular, I will discuss new constraints on the dark matter-neutrino and dark matter-photon scattering cross sections obtained from the observation by IceCube of a few high-energy neutrino events from TXS 0506+056, and their coincident gamma-ray events. I will emphasize the dependence of the constraints with the location where the neutrinos and gamma-rays are produced, and the dependence with the dark matter self-annihilation cross section. The constraints are orders of magnitude more stringent than those derived from considering the attenuation through the intergalactic medium and the Milky Way dark matter halo. When the cross-section increases with energy, the constraints are also stronger than those derived from the CMB and large-scale structure.


Guest: Rostom Mbarek (U Chicago)

Title: High-Energy Neutrino Emission from Espresso-Accelerated Ions in Jets of Active Galactic Nuclei 

[https://arxiv.org/abs/2207.07130]

Abstract: 

We present a bottom-up calculation of the flux of ultra-high energy cosmic rays (UHECRs) and high-energy neutrinos produced by powerful jets of active galactic nuclei (AGNs). By propagating test particles in 3D relativistic magnetohydrodynamic jet simulations, including a Monte Carlo treatment of sub-grid pitch-angle scattering and attenuation losses due to realistic photon fields, we study the spectrum and composition of the accelerated UHECRs and estimate the amount of neutrinos produced in such sources. We find that UHECRs may not be significantly affected by photodisintegration in AGN jets where the espresso mechanism efficiently accelerates particles, consistent with Auger's results that favor a heavy composition at the highest energies. Moreover, we present estimates and upper bounds for the flux of high-energy neutrinos expected from AGN jets. In particular, we find that: i) source neutrinos may account for a sizable fraction, or even dominate, the expected flux of cosmogenic neutrinos; ii) neutrinos from the \beta-decay of secondary neutrons produced in nucleus photodisintegration could in principle contribute to the PeV neutrino flux observed by IceCube, but can hardly account for all of it; iii) UHECRs accelerated via the espresso mechanism lead to nearly isotropic neutrino emission, which suggests that nearby radio galaxies may be more promising as potential sources. We discuss our results in the light of multimessenger astronomy and current/future neutrino experiments.



11:45 am, Friday, Sept 23rd 

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11:45 am, Friday, Sept 16th 

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11:45 am, Friday, Sept 9nd 

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11:45 am, Friday, Sept 2nd 

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11:45 am, Friday, Aug 19th 

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11:45 am, Friday, Aug 5th 

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11:45 am, Friday, July 29th 


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11:45 am, Friday, July 22nd  

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11:45 am, Friday, July 15th   (Pure virtual)

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11:45 am, Friday, July 8th   (Pure virtual)

Guest:  Marc Oncins (ICC-UB)

Title:  Primordial black holes capture by stars and induced collapse to low-mass stellar black holes

[https://arxiv.org/abs/2205.13003]

Abstract:

Primordial black holes in the asteroid-mass window (∼10^(−16) to 10^(−11) M⊙), which might constitute all the dark matter, can be captured by stars when they traverse them at low enough velocity. After being placed on a bound orbit during star formation, they can repeatedly cross the star if the orbit happens to be highly eccentric, slow down by dynamical friction and end up in the stellar core. The rate of these captures is highest in halos of high dark matter density and low velocity dispersion, when the first stars form at redshift z∼20. We compute this capture rate for low-metallicity stars of 0.3 to 1M⊙, and find that a high fraction of these stars formed in the first dwarf galaxies would capture a primordial black hole, which would then grow by accretion up to a mass that may be close to the total star mass. We show the capture rate of primordial black holes does not depend on their mass over this asteroid-mass window, and should not be much affected by external tidal perturbations. These low-mass stellar black holes could be discovered today in low-metallicity, old binary systems in the Milky Way containing a surviving low-mass main-sequence star or a white dwarf, or via gravitational waves emitted in a merger with another compact object. No mechanisms in standard stellar evolution theory are known to form black holes of less than a Chandrasekhar mass, so detecting a low-mass black hole would fundamentally impact our understanding of stellar evolution, dark matter and the early Universe.

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11:45 am, Friday, June 24th

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11:45 am, Friday, June 17th

Guest:  Yu-Dai Tsai (UC, Irvine)

Title:  Planetary Defense and Space Quantum Technologies for Fundamental Physics: Dark Matter, Gravity, and Cosmic Neutrinos 

[https://arxiv.org/abs/2112.07674 & https://arxiv.org/abs/2107.04038]

Abstract:

I will talk about using planetary/asteroidal data and space quantum technologies to study fundamental physics.


I will first show a proposal using space quantum clocks to study solar-halo ultralight dark matter, motivated by the NASA deep space atomic clock (DSAC) and Parker Solar Probe (PSP).

We then discuss new constraints on fifth forces using asteroidal data. We will show preliminary results of the robust constraints by using the NASA JPL program and asteroid tracking data that are used for planetary defense purposes.

We then discuss model-independent constraints on any dark matter models through pure gravity.

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11:45 am, Friday, June 10th

Guest:  Taylor Murphy (Ohio State)

Title: The many distinctive signals of frustrated dark matter

Abstract:

We study a renormalizable model of Dirac fermion dark matter (DM) that communicates with the Standard Model (SM) through a pair of mediators -- one scalar, one fermion -- in the representation (6,1,43) of the SM gauge group SU(3)c×SU(2)L×U(1)Y. While such assignments preclude direct coupling of the dark matter to the Standard Model at tree level, we examine the many effective operators generated at one-loop order when the mediators are heavy, and find that they are often phenomenologically relevant. We reinterpret dijet and pair-produced resonance and jets+EmissT searches at the Large Hadron Collider (LHC) in order to constrain the mediator sector, and we examine an array of DM constraints ranging from the observed relic density Ωχh2Planck to indirect and direct searches for dark matter. Tree-level annihilation, available for DM masses starting at the TeV scale, is required in order to produce Ωχh2Planck through freeze-out, but loops -- led by the dimension-five DM magnetic dipole moment -- are nonetheless able to produce signals large enough to be constrained, particularly by the XENON1T experiment. We find that the parameter space left open by experiment and compatible with freeze-out is quite small, indicating a potential need for further model-building and/or non-standard cosmologies.

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11:45 am, Friday, June 3rd

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11:45 am, Friday, May 27th

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11:45 am, Friday, May 13th

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Guest:  Jan Heisig (RWTH Aachen)

Title: Lyman-alpha constraints on freeze-in and superWIMPs

Abstract:

Dark matter (DM) from freeze-in or superWIMP production is well known to imprint non-cold DM signatures on cosmological observables. We derive constraints from Lyman-alpha forest observations for both cases, basing ourselves on a reinterpretation of the existing Lyman-alpha limits on thermal warm DM. We exclude DM masses below 15 keV for freeze-in, in good agreement with previous literature, and provide a generic lower mass bound for superWIMPs that depends on the mother particle decay width. Special emphasis is placed on the mixed scenario, where contributions from both freeze-in and superWIMP are similarly important. In this case, the imprint on cosmological observables can deviate significantly from thermal warm DM. Furthermore, we provide a modified version of the Boltzmann code class, analytic expressions for the DM distributions, and fits to the DM transfer functions that account for both mechanisms of production. For illustration, we apply the above generic limits to a coloured t-channel mediator DM model, in which case contributions from both freeze-in through scatterings and decays, as well as superWIMP production can be important. We map out the entire cosmologically viable parameter space, cornered by bounds from Lyman-alpha observations, the LHC, and Big Bang Nucleosynthesis.


11:45 am, Friday, May 6th

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Guest:  Jakob van Santen (DESY)

Title: toise: a framework to describe the performance of high-energy neutrino detectors

Abstract:

Neutrinos offer a unique window to the distant, high-energy universe. Several next-generation instruments are being designed and proposed to characterize the flux of TeV--EeV neutrinos. The projected physics reach of the detectors is often quantified with simulation studies. However, a complete Monte Carlo estimate of detector performance is costly from a computational perspective, restricting the number of detector configurations considered when designing the instruments. In this paper, we present a new Python-based software framework, toise, which forecasts the performance of a high-energy neutrino detector using parameterizations of the detector performance, such as the effective areas, angular and energy resolutions, etc. The framework can be used to forecast performance of a variety of physics analyses, including sensitivities to diffuse fluxes of neutrinos and sensitivity to both transient and steady state point sources. This parameterized approach reduces the need for extensive simulation studies in order to estimate detector performance, and allows the user to study the influence of single performance metrics, like the angular resolution, in isolation. The framework is designed to allow for multiple detector components, each with different responses and exposure times, and supports paramterization of both optical- and radio-Cherenkov (Askaryan) neutrino telescopes. In the paper, we describe the mathematical concepts behind toise and provide detailed instructive examples to introduce the reader to use of the framework.


11:45 am, Friday, April 29th

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11:45 am, Friday, April 22th

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11:45 am, Friday, April 15th

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11:45 am, Friday, April 1st

Guest:  Pedro De la Torre Luque (Stockholm University)

Title: The FLUKA cross sections for cosmic-ray propagation

Abstract:

While the accuracy of current cosmic-ray (CR) data allows us to carry out precise tests of our models of propagation of charged particles in the Galaxy, the precision of cross sections data for the production of secondary particles (secondary CRs, neutrinos, gamma rays) is very poor, considerably limiting these tests. Given that most of the calculations of these cross sections from fundamental models of particle interactions are in disagreement with data, we rely on parameterizations fitted to the very scarce and uncertain experimental data.

In the last years, the FLUKA Monte Carlo nuclear toolkit has been optimized to be used in different kinds of CR studies and has been extensively tested against data. In this talk, we present new sets of spallation cross sections of CR interactions in the Galaxy, both inelastic and inclusive, computed with FLUKA. Furthermore, these cross sections have been implemented in the DRAGON2 code to characterize the spectra of CR nuclei up to Z=26 (Iron) and study the main propagation parameters predicted from the spectra of secondary CRs such as B, Be and Li. These results and their implications will be discussed in the talk.


Guest:  Akaxia Cruz (Washington U., Seattle)

Title: Astrophysical Plasma Instabilities induced by Long-Range Interacting Dark Matter

Abstract:

If dark matter (DM) is millicharged or darkly charged, collective plasma processes may dominate momentum exchange over direct particle collisions. In particular, plasma streaming instabilities can couple the momentum of DM to counter-streaming baryons or other DM and result in the counter-streaming fluids coming to rest with each other, just as happens for baryonic collisionless shocks in astrophysical systems. While electrostatic plasma instabilities (such as the two stream) are highly suppressed by Landau damping in the cosmological situations of interest, electromagnetic instabilities such as the Weibel can couple the momenta. Their growth rates are slower than the prior assumption that they would grow at the plasma frequency of DM. We find that the streaming of DM in the pre-Recombination universe is affected more strongly by direct collisions than collective processes, validating previous constraints. However, when considering unmagnetized instabilities the properties of the Bullet Cluster merger would be substantially altered if [qχ/mχ]≳10−4[q_\chi/m_\chi] \gtrsim 10^{-4}[qχ​/mχ​]≳10−4, where [qχ/mχ][/mχ​]][qχ​/mχ​] is the charge-to-mass ratio of DM relative to that of the proton. When a magnetic field is added consistent with cluster observations, Weibel and Firehose instabilities result in the constraint [qχ/mχ]≳10−12−10−11[/mχ​]] \gtrsim 10^{-12}-10^{-11}[qχ​/mχ​]≳10−12−10−11. The constraints are even stronger in the case of a dark U(1)U(1)U(1) charge, ruling out [qχ/mχ]≳10−14[qχ/mχ​]] \gtrsim 10^{-14}[qχ​/mχ​]≳10−14 in the Bullet Cluster system. The strongest previous limits on millicharged DM arise from considering the spin down of galactic disks. We show that plasma instabilities or tangled background magnetic fields could lead to diffusive propagation of DM, weakening these spin down limits. Thus, our constraints from considering plasma instabilities are the most stringent over much of the millicharged and especially dark-charged parameter space.

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11:45 am, Friday, March 25th

Guest: Kayla Leonard (UW–Madison)

Title: Low Energy Event Reconstruction in IceCube DeepCore

Abstract:

The reconstruction of event-level information, such as the direction or energy of a neutrino interacting in IceCube DeepCore, is a crucial ingredient to many physics analyses. Algorithms to extract this high level information from the detector’s raw data have been successfully developed and used for high energy events. In this work, we address unique challenges associated with the reconstruction of lower energy events in the range of a few to hundreds of GeV and present two separate, state-of-the-art algorithms. One algorithm focuses on the fast directional reconstruction of events based on unscattered light. The second algorithm is a likelihood-based multipurpose reconstruction offering superior resolutions, at the expense of larger computational cost.

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11:45 am, Friday, March 11th

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11:45 am, Friday, March 4th

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11:45 am, Friday, Feb 25th

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11:45 am, Friday, Feb 18th

Guest: Andrea Caputo (Weizmann Institute of Science)

Title: Low-Energy Supernovae Severely Constrain Radiative Particle Decays

Abstract:

The hot and dense core formed in the collapse of a massive star is a powerful source of hypothetical feebly-interacting particles such as sterile neutrinos, dark photons, axion-like particles (ALPs), and others. Radiative decays such as a→2γ deposit this energy in the surrounding material if the mean free path is less than the radius of the progenitor star. For the first time, we use a supernova (SN) population with particularly low explosion energies as the most sensitive calorimeters to constrain this possibility. These SNe are observationally identified as low-luminosity events with low ejecta velocities and low masses of ejected 56Ni. Their low energies limit the energy deposition from particle decays to less than about 0.1 B, where 1 B (bethe)=1051 erg. For 1-500 MeV-mass ALPs, this generic argument excludes ALP-photon couplings Gaγγ in the 10−10-10−8 GeV−1 range.

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11:45 am, Friday, Feb 11th

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11:45 am, Friday, Feb 4th

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11:30 am, Friday, Jan 28th

Guest: Kanji Mori (Research Institute of Stellar Explosive Phenomena, Fukuoka University)

Title: Shock Revival in Core-collapse Supernovae Assisted by Heavy Axion-like Particles

Abstract:

Axion-like particles (ALPs) are a class of hypothetical pseudoscalar particles which feebly interact with ordinary matter. The hot plasma of stars and core-collapse supernovae is a possible laboratory to explore physics beyond the standard model including ALPs. Once produced in a supernova, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. We recently calculated the ALP emission in core-collapse supernovae and the backreaction on supernova dynamics consistently. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as $g_{a\gamma}\sim 10^{-9}$ GeV$^{-1}$ and the ALP mass is 40-400 MeV. 

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11:45 am, Friday, Jan 21st

Guest: Anna Suliga (Bohr Inst., UC, Berkeley, Wisconsin U., Madison, and DARK Cosmology Ctr.)

Title: Towards Probing the Diffuse Supernova Neutrino Background in All Flavors

Abstract:

Fully understanding the average core-collapse supernova requires detecting the diffuse supernova neutrino background (DSNB) in all flavors. While the DSNB \bar{νe} flux is near detection, and the DSNB νe flux has a good upper limit and promising prospects for improved sensitivity, the DSNB νx (each of νμ, ντ, \bar{νμ}, \bar{ντ}) flux has a poor limit and heretofore had no clear path for improved sensitivity. We show that a succession of xenon-based dark matter detectors -- XENON1T (completed), XENONnT (under construction), and DARWIN (proposed) -- can dramatically improve sensitivity to DSNB νx the neutrino-nucleus coherent scattering channel. XENON1T could match the present sensitivity of ∼ 10^3 cm^(−2) s^(−1) per νx flavor, XENONnT would have linear improvement of sensitivity with exposure, and a long run of DARWIN could reach a flux sensitivity of ∼ 10 cm^(−2) s^(−1). Together, these would also contribute to greatly improve bounds on non-standard scenarios. Ultimately, to reach the standard flux range of ∼ 1 cm^(−2) s^(−1), even larger exposures will be needed, which we show may be possible with the series of proposed lead-based RES-NOVA detectors.

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11:45 am, Friday, Jan 14th

Guest: Yu-Dai Tsai (UC, Irvine and Fermilab and Chicago U. ,KICP)

Title: SpaceQ -- Direct Detection of Ultralight Dark Matter with Space Quantum Sensors

Abstract:

Recent advances in quantum sensors, including atomic clocks, enable searches for a broad range of dark matter candidates. The question of the dark matter distribution in the Solar system critically affects the reach of dark matter direct detection experiments. Partly motivated by the NASA Deep Space Atomic Clock (DSAC), we show that space quantum sensors present new opportunities for ultralight dark matter searches, especially for dark matter states bound to the Sun. We show that space quantum sensors can probe unexplored parameter space of ultralight dark matter, covering theoretical relaxion targets motivated by naturalness and Higgs mixing. If an atomic clock were able to make measurements on the interior of the solar system, it could probe this highly sensitive region directly and set very strong constraints on the existence of such a bound-state halo in our solar system. We present sensitivity projections for space-based probes of ultralight dark matter which couples to electron, photon, and gluon fields, based on current and future atomic, molecular, and nuclear clocks.

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11:45 am, Friday, Jan 7th

Guest: Federica Bradascio (IRFU, Saclay)

Title: A search for neutrino emission from cores of Active Galactic Nuclei

Abstract:

The sources of the majority of the high-energy astrophysical neutrinos observed with the IceCube neutrino telescope at the South Pole are unknown. So far, only a gamma-ray blazar was compellingly associated with the emission of high-energy neutrinos. In addition, several studies suggest that the neutrino emission from the gamma-ray blazar population only accounts for a small fraction of the total astrophysical neutrino flux. In this work we probe the production of high-energy neutrinos in the cores of Active Galactic Nuclei (AGN), induced by accelerated cosmic rays in the accretion disk region. We present a likelihood analysis based on eight years of IceCube data, searching for a cumulative neutrino signal from three AGN samples created for this work. The neutrino emission is assumed to be proportional to the accretion disk luminosity estimated from the soft X-ray flux. Next to the observed soft X-ray flux, the objects for the three samples have been selected based on their radio emission and infrared color properties. For the largest sample in this search, an excess of high-energy neutrino events with respect to an isotropic background of atmospheric andastrophysical neutrinos is found, corresponding to a post-trial significance of 2.60 sigma. . Assuming a power-law spectrum, the best-fit spectral index is 2.03^{+0.14}_{-0.11}, consistent with expectations from particle acceleration in astrophysical sources. If interpreted as a genuine signal with the assumptions of a proportionality of X-ray and neutrino fluxes and a model for the sub-threshold flux distribution, this observation implies that at 100 TeV, 27% - 100% of the observed neutrinos arise from particle acceleration in the core of AGN.

Guest: Simeon Reusch (DESY)

Title: Neutrinos from tidal disruption and accretion events

Abstract:

The origins of the high-energy cosmic neutrino flux remain largely unknown. Last year, a high-energy neutrino was associated with the tidal disruption event (TDE) AT2019dsg by our group. I will present AT2019fdr, an exceptionally luminous TDE candidate, coincident with another high-energy neutrino detected by IceCube. I will present observations that further support a TDE origin of this flare. These include a bright dust echo and soft late-time X-ray emission. The probability of finding two such bright events in neutrino follow-up by chance is just 0.034%. Furthermore, we have evaluated several models for neutrino production and can show that AT2019fdr is capable of producing the observed high-energy neutrino. I will also present further evidence on accretion events accompanied by luminous dust echoes being connected to high-energy neutrinos, as we have found another event with such a signature coincident with a high-energy neutrino (AT2019aalc). This reinforces the case for TDEs as neutrino sources.

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2021

11:45 am, Friday, Dec 17th

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11:45 am, Friday, Dec 10th

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11:45 am, Friday, Dec 3rd

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Guest: Payel Mukhopadhyay (Stanford)

Title: Supernova outflows - From Hydrodynamics to Nucleosynthesis

Abstract:

Neutrino driven outflow hydrodynamics in core-collapse supernovae can have a profound impact on the detectable neutrino oscillation signatures. Additionally, the hydrodynamics of these outflows impact the yields of p-nuclides such as Molybdenum and Ruthenium whose abundance in solar system is a mystery. In this talk, I show that neutrino driven outflows possess a special property known as near-criticality which, in turn impacts the observed neutrino signals in DUNE. Additionally, I show that a self-consistent treatment of outflow hydrodynamics also makes core-collapse supernovae an attractive candidate for the so called nu p- process, proving clue to the origin of isotopes like 92,94 Mo and 96,98 Ru in the Solar System. 


11:45 am, Friday, Nov 19th

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Guest: Anupam Ray (Tata Institute Of Fundamental Research)

Title: Unravelling the Mystery of Dark Matter with Black Holes

Abstract:

Primordial black holes (PBHs), possibly formed via gravitational collapse of large density perturbations in the very early universe, are one of the earliest proposed and viable dark matter (DM) candidates. PBHs can make up a large or even entirety of DM over a wide range of masses. Ultralight PBHs in the mass range of 10^{15} - 10^{17} g, emit particles via Hawking radiation, act as a decaying DM, and can be probed via observations of those emitted particles in various space as well as ground based detectors. In this talk, I will discuss how diffuse supernova neutrino background searches at the Super-Kamiokande neutrino observatory, measurement of the 511 keV gamma-ray line by INTEGRAL telescope, observations of low energy Galactic Center photons by the imminent soft gamma-ray telescope AMEGO, and EDGES measurement of the global 21-cm signal can set robust, world-leading exclusions on the fraction of DM composed of ultralight PBHs. Finally, I will also discuss a novel formation mechanism of low mass transmuted black holes which can be a viable non-primordial solution to sub-Chandrasekhar mass, pointing out several avenues to test the transmuted origin of low mass black holes.


Guest: Yuanhong Qu (University of Nevada, Las Vegas)

Title: Neutrino emission from FRB-emitting magnetars

Abstract:

The detection of FRB 200428 in association with a hard X-ray burst from the Galactic magnetar SGR 1935+2154 suggests that magnetars can make FRBs.We study possible neutrino emission from FRB-emitting magnetars by developing a general theoretical framework. We consider three different sites for proton acceleration and neutrino emission, i.e. within the magnetosphere, in the current sheet region beyond the light cylinder, and in relativistic shocks far away from the magnetosphere. All three scenarios can allow protons to be accelerated to high enough energies to interact with 10 − 200 keV X-ray photons to produce neutrinos. Different cooling processes for protons and pions are considered to calculate the neutrino emission suppression factor within each scenario. We find that the flux of the neutrino emission decreases with increasing radius from the magnetar due to the decrease of the target photon number density. We calculate the neutrino flux from FRB 200428 and its associated X-ray burst. The flux of the most optimistic case invoking magnetospheric proton acceleration is still ∼ 4 orders of magnitude below the IceCube sensitivity. We also estimate the diffuse neutrino background from all FRB-emitting magnetars in the universe. The total neutrino flux of magnetars during their FRB emission phases is a negligible fraction of observed diffuse emission even under the most optimistic magnetospheric scenario for neutrino emission. However, if one assumes that many more X-ray bursts without FRB associations can also produce neutrinos with similar mechanisms, magnetars can contribute up to 10^(−8) GeV s^(−1) sr^(−1) cm^(−2) diffuse neutrino background flux in the GeV to multi-TeV range. Future detection or non-detection of neutrinos from bright Galactic magnetar-associated FRBs may provide a diagnosis on the particle acceleration site in FRB-emitting magnetars.


For suggestions of cool papers on arXiv, email me: esteban.6(-@-)osu.edu


11:45 am, Friday, Nov 12th

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Guest: Rostom Mbarek (University of Chicago)

Title: Ultra-High-Energy Cosmic Rays and Neutrinos from relativistic jets of Active Galactic Nuclei 

Abstract:

In Mbarek & Caprioli (2019), we laid the groundwork for studying the espresso paradigm Caprioli (2015), a reacceleration mechanism to boost galactic cosmic rays (CRs) to Ultra-High-Energy CR (UHECR) levels. Our bottom-up approach uses realistic 3D MHD simulations of relativistic AGN jets and accounts for all of the crucial ingredients of a universal acceleration theory: injection, acceleration, and escape in realistic environments. Our results are consistent with the main features of UHECR spectra, i.e., power-law slopes, chemical composition, and anisotropy. In Mbarek & Caprioli (2021), we refine our model by including sub-grid particle scattering to model small-scale magnetic turbulence that cannot be resolved by MHD simulations, constraining for the first time one crucial but hard-to-model ingredient, and allowing us to establish the relative importance of espresso and stochastic shear acceleration in relativistic jets. Here, we analyze high-energy neutrinos produced from our accelerated UHECRs considering the effects of external photon fields, and incorporate nucleus photodisintegration. We find that UHECRs are not significantly affected by photodisintegration in AGN jets, which is consistent with Auger's detection of heavy elements at the highest energies. We also note that the source neutrino flux at E>1e17 eV is comparable to that of cosmogenic neutrinos, and that the steady neutrino emission from AGN jets cannot solely account for IceCube's signal.


11:45 am, Friday, Nov 5th

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11:45 am, Friday, Oct 29th via Zoom

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Guest: Pedro Machado (Fermilab)

Title: Atmospheric neutrinos at DUNE

Abstract:

In this talk I will discuss how DUNE can leverage its liquid argon time projection chamber (LArTPC) technology to study atmospheric neutrinos. Because of the event reconstruction in LArTPCs, DUNE can use the large atmospheric neutrino flux below 1 GeV to do several physics analysis, including CP violation and Earth tomography.

Guest: Javier Acevedo (Queen's U)

Title: Detecting Composite Dark Matter with Bremsstrahlung and the Migdal Effect

Abstract:

An intriguing possibility for dark matter is that it formed bound states in the early Universe, much like the Standard Model fundamental particles formed nucleons, nuclei, and atoms, in a scenario called “composite” dark matter. One of the simplest composite dark matter models consists of dark matter fermions bound together by a real scalar field. Composite states that are massive enough source a scalar field so intense that nuclei, when coupled to this binding field, accelerate upon contact to energies capable of various collisional processes, including ionization, thermal bremsstrahlung, and even nuclear fusion. Such observable effects occur even when the coupling between nuclei and the binding field is vanishingly small, and have implications for the detection of dark matter through experiments as well as astrophysical observations. In this talk, I will discuss the detection prospects for these composite states by considering the Migdal effect at dark matter direct detection experiments, and thermal bremsstrahlung at large neutrino observatories.


11:45 am, Friday, Oct 22nd via Zoom

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Guest: Tarak Nath Maity (Indian Institute of Science)

Title: A search for dark matter using sub- PeV γ-rays observed by Tibet ASγ

Abstract:

The discovery of diffuse sub-PeV gamma-rays by the Tibet ASγ collaboration promises to revolutionize our understanding of the high-energy astrophysical universe. It has been shown that this data broadly agrees with prior theoretical expectations. In this talk, we will explore the impact of this discovery on a well-motivated new physics scenario: PeV-scale decaying dark matter (DM). Considering a wide range of final states in DM decay, a number of DM density profiles, and numerous astrophysical background models, we find that this data provides the most stringent limit on DM lifetime for various Standard Model final states. In particular, we find that the strongest constraints are derived for DM masses in between a few PeV to few tens of PeV.


11:45 am, Friday, Oct 8th via Zoom

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Guest:  Julia Gehrlein (BNL)

Title: Connecting the Extremes: A Story of Supermassive Black Holes and Ultralight Dark Matter

Abstract:

The formation of ultra rare supermassive black holes (SMBHs), with masses of O(10^9 M⊙), in the first billion years of the Universe remains an open question in astrophysics. At the same time, ultralight dark matter (DM) with mass in the vicinity of O(10^(−20) eV) has been motivated by small scale DM distributions. Though this type of DM is constrained by various astrophysical considerations, certain observations could be pointing to modest evidence for it. We present a model with a confining first order phase transition at ∼ 10 keV temperatures, facilitating production of O(10^9 M⊙) primordial SMBHs. Such a phase transition can also naturally lead to the implied mass for a motivated ultralight axion DM candidate, suggesting that SMBHs and ultralight DM may be two sides of the same cosmic coin. We consider constraints and avenues to discovery from superradiance and a modification to Neff . On general grounds, we also expect primordial gravitational waves – from the assumed first order phase transition – characterized by frequencies of O(10^(−12) − 10^(−9) Hz). This frequency regime is largely uncharted, but could be accessible to pulsar timing arrays if the primordial gravitational waves are at the higher end of this frequency range, as could be the case in our assumed confining phase transition.



11:45 am, Friday, Oct 1st via Zoom

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11:45 am, Friday, Sep 24th via Zoom

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Guest:  Nirmal Raj (TRIUMF)

Title: Dark Matter Direct Detection in an Inter-Clump Void

Abstract:

On sub-kiloparsec scales dark matter could cluster and form compact subhalos, in which the majority of Galactic dark matter could reside. Null results in direct detection experiments since their advent four decades ago could then be the result of extremely rare encounters between the Earth and these subhalos. I present alternative and promising means to identify subhalo dark matter interacting with Standard Model particles: (1) subhalo collisions with old neutron stars can transfer kinetic energy and brighten the latter to luminosities within the reach of imminent infrared, optical, and ultraviolet telescopes; this already sets bounds on self-interacting dark matter in subhalos from the coldest known neutron star, (2) subhalo dark matter scattering with cosmic rays results in detectable effects, (3) historic Earth-subhalo encounters can leave dark matter tracks in paleolithic minerals deep underground. These searches, which are highly complementary to microlensing surveys, could discover dark matter subhalos over vast parametric ranges, between the masses of a typical lake and a typical star, with corresponding dark matter cross sections and masses spanning tens of orders of magnitude.



For suggestions of cool papers on arXiv, email me: esteban.6(-@-)osu.edu


11:45 am, Friday, Sep 10th via Zoom

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11:45 am, Friday, Sep 10th via Zoom

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11:45 am, Friday, Sep 3rd via Zoom

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Guest:  Daichi Tsuna (Tokyo U)

Title: Observing the Traces of Black Hole Formation

Abstract:

Failed explosion of massive stars is considered to be the main channel to form stellar-mass black holes seen in electromagnetic and gravitational waves. Though we likely cannot see these events as spectacular supernovae, mass ejection can still occur due to weakening of gravity when the central core emits neutrinos. In this talk I will discuss our recent predictions on the observational consequence of these events, focusing on emission when the ejected material sweeps up the surrounding matter.

11:45 am, Friday, Aug 27th via Zoom

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Guest:  Jose Carpio (PSU)

Title: High-energy cosmic neutrinos as a probe of the vector mediator scenario in light of the muon g − 2 anomaly and Hubble tension

Abstract:

In light of the recent Muon g − 2 experiment data from Fermilab, we investigate the implications of a gauged Lµ − Lτ model for high energy neutrino telescopes. It has been suggested that a new gauge boson at the MeV scale can both account for the Muon g −2 data and alleviate the tension in the Hubble parameter measurements. It also strikes signals at IceCube from the predicted resonance scattering between high-energy neutrinos and the cosmic neutrino background. We revisit this model based on the latest IceCube shower data, and perform a four-parameter fit to find a preferred region. While the data are consistent with the absence of resonant signatures from secret interactions, we find the preferred region consistent with the muon g − 2 anomaly and Hubble tension. We demonstrate that future neutrino telescopes such as IceCube-Gen2 can probe this unique parameter space, and point out that successful measurements would infer the neutrino mass with 0.05 eV <~ Σmν <~ 0.3 eV.

11:45 am, Friday, Aug 20th via Zoom

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    with the passcode: 984288

Guest:  Anirban Das (SLAC)

Title:    'Direct Detection' of Dark Asteroids

Abstract:

Macroscopic dark matter is mostly unconstrained over a wide asteroid-mass range, where it could scatter on visible matter with geometric cross section. In this talk, I shall describe when such a 'dark asteroid' travels through a star, it produces shock waves which reach the stellar surface, and gives out distinctive transient optical, UV and X-ray emission. This signature can be searched for on a variety of stellar types and locations. In a dense globular cluster, such events occur far more often than stellar flares. An existing UV telescope, such as the Hubble Telescope, could probe orders of magnitude in dark asteroid mass in one week of dedicated observation.

11:45 am, Friday, August 13 via Zoom

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    with the ID:  994 3702 4737 and password:  102987

11:45 am, Friday, August 7 via Zoom

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    with the ID:  993 1044 3456 and password: 451761

11:45 am, Friday, July 30th via Zoom

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Guest:  Mike Pajkos (MSU)

Title:    Interpreting Core-collapse Multimessenger Signals Using Supernova Simulations

Abstract:

As some of the most energetic events in the universe, core-collapse supernovae (CCSNe) act as effective laboratories for many areas of physics that occur on a variety of length scales.  With electromagnetic and multimessenger observatories constantly improving sensitivities, astronomers stand poised to constrain the physics within these high energy laboratories using a variety of signals.  This talk reviews results from high-fidelity multiphysics simulations, connecting the expected gravitational waves produced in a core-collapse event to the internal supernova physics.  Likewise, it highlights relationships between the neutrino production and the CCSN evolution.  Lastly, this talk outlines additions to the FLASH multiphysics code that improve the predictive power of numerical models for supernova multimessenger signals.

11:45 am, Friday, July 23th via Zoom

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    with the password: 358863