2021

11:45 am, Friday, Dec 17th

Use this link to access the meeting: ZOOM

11:45 am, Friday, Dec 10th

Use this link to access the meeting: ZOOM

Magnetically Induced Anisotropies in the Arrival Directions of Ultra-high-energy Cosmic Rays from Nearby Radio Galaxies
Standard Self-Confinement and Extrinsic Turbulence Models for Cosmic Ray Transport are Fundamentally Incompatible with Observations
Measuring the Polarization Reconstruction Resolution of the ARIANNA Neutrino Detector with Cosmic Rays
Numerical Study of Cosmic Ray Confinement through Dust Resonant Drag Instabilities
A Model-Independent Radio Telescope Dark Matter Search
Using Evolutionary Algorithms to Design Antennas with Greater Sensitivity to Ultra High Energy Neutrinos
Space applications of GAGG:Ce scintillators: a study of afterglow emission by proton irradiation
Audio Universe Tour of the Solar System: using sound to make the Universe more accessible
Identifying mass composition of ultra-high-energy cosmic rays using deep learning
Improving sensitivity of the ARIANNA detector by rejecting thermal noise with deep learning

11:45 am, Friday, Dec 3rd

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

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

Use this link to access the meeting: ZOOM

with the ID: 994 3702 4737 and password: 102987

11:45 am, Friday, August 7 via Zoom

Use this link to access the meeting: ZOOM

with the ID: 993 1044 3456 and password: 451761

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

Use this link to access the meeting: ZOOM

Zoom ID: 915 9772 6964

with the password: 659271

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

Use this link to access the meeting: ZOOM

with the password: 358863

11:45 am, Friday, July 16th via Zoom

Use this link to access the meeting: ZOOM

11:45 am, Friday, July 9th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 55688

Guest: Claire Guépin (UMD)

Title: Indirect dark matter searches at ultrahigh energy neutrino detectors

Abstract:

High to ultrahigh energy neutrino detectors can uniquely probe the properties of dark matter χ by searching for the secondary products produced through annihilation and/or decay processes. We evaluate the sensitivities to dark matter thermally averaged annihilation cross section <σv> and partial decay width into neutrinos Γχ→νν¯ (in the mass scale 10^7 ≤ mχ/GeV ≤ 10^15) for next generation observatories like POEMMA and GRAND. We show that in the range 10^7 ≤ mχ/GeV ≤ 10^11, space-based Cherenkov detectors like POEMMA have the advantage of full-sky coverage and rapid slewing, enabling an optimized dark matter observation strategy focusing on the Galactic center. We also show that ground-based radio detectors such as GRAND can achieve high sensitivities and high duty cycles in radio quiet areas. We compare the sensitivities of next generation neutrino experiments with existing constraints from IceCube and updated 90% C.L. upper limits on <σv> and Γχ→νν¯ using results from the Pierre Auger Collaboration and ANITA. We show that in the range 10^7 ≤ mχ/GeV ≤ 10^11 POEMMA and GRAND10k will improve the neutrino sensitivity to particle dark matter by factors of 2 to 10 over existing limits, whereas GRAND200k will improve this sensitivity by two orders of magnitude. In the range 10^11 ≤ mχ/GeV ≤ 10^15 , POEMMA’s fluorescence observation mode will achieve an unprecedented sensitivity to dark matter properties. Finally, we highlight the importance of the uncertainties related to the dark matter distribution in the Galactic halo, using the latest fit and estimates of the Galactic parameters.

11:45 am, Friday, Jun 25th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 55688

Juneteenth holiday: No APL on Jun 18th

11:45 am, Friday, Jun 11th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 130425

11:45 am, Friday, Jun 4th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 55688

Guest: Ivan Martinez-Soler (Northwestern U)

Title: SN1987A still shining: A Quest for Pseudo-Dirac Neutrinos

Abstract:

Ever since the discovery of neutrinos, one question has daunted us, are neutrinos their own antiparticles? One remarkable possibility is that neutrinos have a pseudo-Dirac nature, truly Majorana neutrinos which behave, for all practical purposes, as Dirac fermions, only distinguishable by tiny mass-squared differences. Such mass differences would induce oscillations that could only be conspicuous over astrophysical baselines. We analyze the neutrino data from SN1987A in the light of these active sterile oscillations and find a mild preference (∆χ^2 ≈ 3) for a non-zero quadratic mass difference δm^2 = 6.31 × 10^(−20) eV^2 . Notably, the same data is able to exclude δm^2 ~ [2.55, 3.01] × 10^(−20) eV^2 with ∆χ^2 > 9, the tiniest mass differences constrained so far. We further consider the future sensitivity of next-generation experiments like the Deep Underground Neutrino Experiment (DUNE) and Hyper-Kamiokande (HK) and demonstrate that, for a future galactic SN occurring at 10 kpc, mass-squared differences as small as ~ 10^(−20) eV^2 could be explored.

11:45 am, Friday, May 28th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 379133

11:45 am, Friday, May 21st via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 562867

Guest: Daniele Teresi (CERN)

11:45 am, Friday, May 14th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 55688

11:45 am, Friday, May 7th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 841892

Guest: Bei Zhou (Johns Hopkins University)

11:45 am, Friday, Apr 30 via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 14212

Guest: Carlos Blanco (Stockholm U., OKC)

Title: Gamma-Rays from Star Forming Activity Appear to Outshine Misaligned Active Galactic Nuclei

11:45 am, Friday, Apr 23rd via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 634079

11:45 am, Friday, Apr 16th not via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 55688

Guest: Andrea Caputo (Weizmann Inst.)

Title: Searching for Sterile Neutrino with X-ray Intensity Mapping

Abstract:

The cosmological X-ray emission associated to the possible radiative decay of sterile neutrinos is composed by a collection of lines at different energies. For a given mass, each line corresponds to a given redshift. In this work, we cross correlate such line emission with catalogs of galaxies tracing the dark matter distribution at different redshifts. We derive observational prospects by correlating the X-ray sky that will be probed by the eROSITA and Athena missions with current and near future photometric and spectroscopic galaxy surveys. A relevant and unexplored fraction of the parameter space of sterile neutrinos can be probed by this technique.

11:45 am, Friday, Apr 9th not via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 55688

Guest: Anders E. Thomsen (Bern U.)

Title: A Model of Muon Anomalies

Abstract:

The Standard Model (SM) is augmented with a U(1)B−3Lμgauge symmetry spontaneously brokenabove the TeV scale when an SM-singlet scalar condenses. Scalar leptoquarksS1(3)= (3,1(3),1/3)charged under U(1)B−3Lμmediate the intriguing effects observed in muon (g−2),RK(∗)andb→sμ+μ−, while generically evading all other phenomenological constraints. The fermionic sectoris minimally extended with three right-handed neutrinos, and a successful type-I seesaw mechanismis realized. Charged lepton flavor violation and proton decay—common predictions of leptoquarks—are postponed to the dimension-6 effective Lagrangian. Unavoidable radiative corrections in theHiggs mass and muon Yukawa favor leptoquark masses interesting for collider searches. The param-eters of the model are radiatively stable and can be evolved by the renormalization group to thePlanck scale without inconsistencies. Alternative models based on a U(1)Lμ−Lτgauge symmetryare proposed for comparison.

11:45 am, Friday, April 1.5th not via Zoom

11:45 am, Friday, Mar 26th via Zoom

Guest: Timon Emken (Chalmers Uni)

Use this link to access the meeting: ZOOM

with the passcode: 295577

11:45 am, Friday, Mar 19th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 250931

11:45 am, Friday, Mar 12th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 12345

Guest: Yi-Kuan Chiang

11:45 am, Friday, Mar 5th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 31415

Guest: Xavier Rodrigues (DESY)

Title: AGN jets as the origin of UHECRs and perspectives for the detection of EeV astrophysical neutrinos

Abstract:

We demonstrate that a population of Active Galactic Nuclei (AGN) can describe the observed spectrum of ultra-high-energy cosmic rays (UHECRs) at and above the ankle, and that the dominant contribution comes from low-luminosity BL Lacs. Such an AGN-only scenario is in tension with UHECR composition observations above 10 EeV. However, a sub-dominant contribution from high-luminosity AGN reduces this tension and leads simultaneously to a substantial neutrino flux that peaks at EeV energies. The same emission also extends down to PeV energies, and is therefore constrained by current IceCube limits. We also show that the flux of neutrinos emitted from within the sources should outshine the cosmogenic neutrinos produced during the propagation of UHECRs. This result has profound implications for ultra-high-energy (∼EeV) neutrino experiments, since additional search strategies can be used for source neutrinos compared to cosmogenic neutrinos, such as stacking searches, flare analyses, and multi-messenger follow-ups.

11:45 am, Friday, Feb 26th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 544989

11:45 am, Friday, Feb 19th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 111111

11:45 am, Friday, Feb 12th via Zoom

Guest: Payel Mukhopadhyay (Stanford U)

Use this link to access the meeting: ZOOM

with the passcode: 111111

11:45 am, Friday, Feb 5th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 111111

11:45 am, Friday, Jan 29nd via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 00000

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

Use this link to access the meeting: ZOOM

with the passcode: 00000

Guest: Francesco Capozzi (Virginia Tech), Linda Xu (Harvard)

11:45 am, Friday, Jan 15th via Zoom

Use this link to access the meeting: ZOOM

with the passcode: 053289

Guest: Edoardo Vitagliano (UCLA)

2020

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

Use this link to access the meeting: ZOOM

with the passcode: 983520

Guest: Aneta Wojnar (Tartu University)

Page updated

Google Sites

Report abuse