# 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:

Po-Wen Chang -- chang.1750@osu.eduIván Esteban -- esteban.6@osu.eduKeith McBride -- mcbride.342@osu.edu

## Fridays from 11:45 am - 12:45 pm (EDT)

Price Place (PRB) & VIA ZOOM

### COMING UP:

2022

11:45 am, Friday, Nov 18th

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Guest: Pawan Dhakal

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.

### PAST EVENTS

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)

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

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

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

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

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)

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)

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)

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)

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)

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

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)

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)

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.)

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

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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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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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)

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)

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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Zoom ID: 915 9772 6964

Guest: Mike Pajkos (MSU)

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

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

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Guest: Claire Guépin (UMD)

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

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with the passcode: 55688

Juneteenth holiday: No APL on Jun 18th

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

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with the passcode: 130425

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

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Guest: Ivan Martinez-Soler (Northwestern U)

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

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with the passcode: 379133

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

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with the passcode: 562867

Guest: Daniele Teresi (CERN)

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

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

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Guest: Bei Zhou (Johns Hopkins University)

11:45 am, Friday, Apr 30 via Zoom

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with the passcode: 14212

Guest: Carlos Blanco (Stockholm U., OKC)

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

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with the passcode: 634079

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

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Guest: Andrea Caputo (Weizmann Inst.)

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

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Guest: Anders E. Thomsen (Bern U.)

Abstract:

The Standard Model (SM) is augmented with a U(1)B3Lμgauge symmetry spontaneously brokenabove the TeV scale when an SM-singlet scalar condenses. Scalar leptoquarksS1(3)= (3,1(3),1/3)charged under U(1)B3Lμmediate 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

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with the passcode: 295577

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

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with the passcode: 250931

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

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Guest: Yi-Kuan Chiang

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

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with the passcode: 31415

Guest: Xavier Rodrigues (DESY)

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

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with the passcode: 544989

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

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with the passcode: 111111

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

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

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

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with the passcode: 00000

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

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

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

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with the passcode: 053289

Guest: Edoardo Vitagliano (UCLA)

2020

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

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with the passcode: 983520

Guest: Aneta Wojnar (Tartu University)

11:45 am, Friday, Dec 18th via Zoom

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with the passcode: 352924

Guest: William Luszczak (University of Wisconsin)

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

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with the passcode: 12345

Guest: Yu-Dai Tsai (Fermilab)

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

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with the passcode: 12345

No Lunch on Friday, Nov 27th

Enjoy the Thanksgiving holiday : )

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

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with the passcode: 12345

Guest: Philip Lu (UCLA)

11:45 am, Friday, Nov 13th via Zoom

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with the passcode: 12345

Guest: Pierluca Carenza (Bari U.)

No Lunch on Friday, Nov 6th

Papers of interest:

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

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with the passcode: 515588

Guest: Chengchao Yuan (PSU)

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

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Guest: Jaryd Ulbricht from UCSC

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

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with the passcode: 743046

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

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with the passcode: 489879

11:45 am, Friday, Oct 2nd via Zoom

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

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This week, Professor Basudeb Dasgupta will give a talk about his recent paper, "Fast Flavor Depolarization of Supernova Neutrinos"

11:45 am, Friday, Sept 18th via Zoom

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with the passcode: 797537

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

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

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

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11:45 am, Friday, August 21th via Zoom

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Ningqiang Song, a postdoc at Queen's University, will give a talk about his recent work in collaboration with Aaron Vincent on microscopic black holes at IceCube and FCC (https://arxiv.org/abs/1907.08628, https://arxiv.org/abs/1912.06656).

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

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with the passcode: 037402

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

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

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11:45 am, Friday, July 17th via Zoom

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

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

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

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

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

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

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

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

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

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