Weekly on Friday 11:30 am - 12:30 pm, at PRB M2005


Fall 2015

11:30 am, Friday, Nov 20th at PRB M2005 (Price Place)

Special Seminar
Time: 11:30- 12:00 
Speaker: Peter Denton (Vanderbilt)

Title:Cosmic Ray Anisotropy with Partial Sky Exposure

Abstract: UHECRs are the highest energy particles in the universe, yet very little is known about them. Their composition, sources, acceleration, and propagation details are all wholly unknown. The first step to addressing this problem is determining the sources, which requires measuring an anisotropy. Above $E\sim55$ EeV, anisotropies are expected to appear due to the GZK horizon, yet no definitive signal has been seen. Here I overview the current experimental status and present a discussion of anisotropy reconstruction techniques, along with their strengths and weaknesses. I use spherical harmonics as a general tool to detect large scale anisotropies in a low statistics environment. I compare the benefits of a full sky experiment such as JEM-EUSO to ground based partial sky experiments such as the Pierre Auger Observatory and Telescope Array. I show that while Auger can reconstruct a quadrupole without a partial sky penalty, partial sky exposure generally leads to a loss of precision beyond that just from lower statistics compared to a full sky experiment.

11:30 am, Friday, Nov 13th at PRB M2005 (Price Place)
  1. Problems and Prospects from a Flood of Extragalactic TeV Neutrinos in IceCube
  2. First combined search for neutrino point-sources in the Southern Hemisphere with the ANTARES and IceCube neutrino telescopes
  3. Flaring of tidally compressed dark-matter clumps
  4. Presupernova neutrinos: realistic emissivities from stellar evolution
  5. Fermi-LAT Observations of High-Energy Gamma-Ray Emission Toward the Galactic Center
  6. Sensitivity to oscillation with a sterile fourth generation neutrino from ultra-low threshold neutrino-nucleus coherent scattering
  7. The IceCube Neutrino Observatory, the Pierre Auger Observatory and the Telescope Array: Joint Contribution to the 34th International Cosmic Ray Conference (ICRC 2015)
  8. Pierre Auger Observatory and Telescope Array: Joint Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)

11:30 am, Friday, Nov 6th at PRB M2005 (Price Place)

Special Seminar
Time: 11:30- 12:00 
Speaker: Tathagata Ghosh (TAMU)

Title: Limits on cascade annihilation models and decaying dark matter lifetime from dwarf galaxies using Fermi-LAT

Abstract: Dwarf spheroidal galaxies are promising targets for the indirect detection of dark matter through gamma-ray emission due to their proximity, lack of astrophysical backgrounds and high dark matter density. They are often used to place restrictive bounds on the dark matter annihilation cross section. Many particle dark matter models predict that the dark matter undergoes cascade annihilations, i.e. the annihilation products are 4-body final states. In the context of model-independent cascade annihilation models, we review the compatibility of the dark matter interpretation of the Fermi-LAT Galactic center gamma-ray emission with null detections from dwarf spheroidal galaxies using six years of Fermi-LAT data. In addition, we present the analysis of data from 20 Dwarf Spheroidal galaxies and derivation from a stacked analysis, robust 95% confidence level upper limits on the dark matter lifetime for several decay channels and dark matter masses between 10 GeV and 10 TeV.

  1. A Tale of Two Pulsars and the Origin of TeV Gamma Rays from the Galactic Center
  2. Gamma Rays, Electrons, Hard X-Rays, and the Central Parsec of the Milky Way
  3. Searches for Relativistic Magnetic Monopoles in IceCube
  4. The Absolute Rate of LGRB Formation
  5. The Relative Rate of LGRB Formation as a Function of Metallicity
  6. Evidence against star-forming galaxies as the dominant source of IceCube neutrinos
  7. Resolving the Extragalactic γ-ray Background above 50 GeV with Fermi-LAT
  8. Search for Gamma-Ray Lines towards Galaxy Clusters with the Fermi-LAT
  9. Neutron capture and the antineutrino yield from nuclear reactors
  10. Measurement of θ13 in Double Chooz using neutron captures on hydrogen with novel background rejection techniques
  11. Global Constraints on a Heavy Neutrino
  12. The origin of IceCube's neutrinos: Cosmic ray accelerators embedded in star forming calorimeters
  13. A Predictive Analytic Model for the Solar Modulation of Cosmic Rays

11:30 am, Friday, Oct 30th at PRB M2005 (Price Place)

Special Seminar
Time: 11:30- 12:00 
Speaker: Gregory Dooley (MIT)

Title: The effect of Self-Interacting Dark Matter on tidal stripping in satellite galaxies and the galactic halo

Abstract: Observations of low surface brightness galaxies, low mass spiral galaxies, and Miky Way dwarf 
spheroidals indicate that the central density of galaxies is lower than predicted in pure CDM simulations. 
Self-interacting dark matter offers one possible explanation to the formation of low density cores in galactic 
halos. Particles are allowed to elastically scatter, and in the higher density central regions of galaxies, an 
 increased scattering rate tends to drive out mass, transforming cusps into cores. Motivated by the lower 
binding energy of cores vs. cusps, we investigate the effect that SIDM has on the tidal stripping of mass 
in satellite galaxies around a Milky Way analog. Using n-body, dark matter only simulations of four different 
models of SIDM, two of constant cross section and two with a velocity-dependent cross section, we 
demonstrate that while the stripping of total bound dark matter mass is not significantly affected by permitted 
SIDM models, the the stellar mass loss rate is appreciably increased. This implies a depression in the 
satellite luminosity function in halos that pass within 50 kpc of their host. I will also present results that 
 differentiate the models which need further investigation.

11:30 am, Friday, Oct 23rd at PRB M2005 (Price Place)

11:30 am, Friday, Oct 9th at PRB M2005 (Price Place)

Special Seminar 1
Speaker: Basudeb Dasgupta ( Tata Institute of Fundamental Research )

Title: Neutrino Flavor Conversion at Very High Density
We show that the flavor content of a dense gas of neutrinos is 
unstable to small oscillations in time. The tendency is to equilibrate 
the fluxes and and spectra of all flavors. We argue that this can 
happen at very high neutrino and matter densities, i.e., deeper 
in a supernova than previously realized, and may have profound 
consequences for core-collapse supernovae.

Special Seminar 2
Speaker: Rebecca Leane ( University of Melbourne )

Title: Dark Matter at the LHC
In this talk I consider several issues faced by WIMP dark matter searches. 
Firstly, I discuss the popular use of effective field theories (EFTs) to quantify 
LHC bounds on dark matter, and show that some EFT operators considered 
do not respect the weak gauge symmetries of the standard model. These 
operators break down at the electroweak scale, rather than the energy scale 
of new physics, and are invalid at LHC energies. I consider the circumstances 
in which such operators can arise, use the mono-W process to illustrate 
potential issues in their interpretation and application, and discuss the 
phenomenology of a UV complete model that avoids such difficulties. In addition, 
as the WIMP parameter space is becoming increasingly constrained, I discuss 
the phenomenology of a simple leptophilic dark matter model, where the absence 
of tree-level dark matter couplings to quarks can relax the strong limits placed 
by hadron based experiments.

11:30 am, Friday, Oct 2nd at PRB M2005 (Price Place)

11:30 am, Friday, Sept 25th at PRB M2005 (Price Place)

Special Seminar
Time: 11:30- 12:00 
Speaker: Prof. Jure Zupan (University of Cincinnati)

Title: Some thoughts on Higgs portal to dark matter
Abstract: In the talk I will cover two aspects of Higgs portal dark  
matter: the effect of non-standard Higgs Yukawa couplings, and 
the searches for the mediators that need to be present in the 
case of fermionic dark matter.

Papers of interests this week:

11:30 am, Friday, Sept 18th at PRB M2005 (Price Place)

Special Seminar
Time: 11:30- 12:00 
Speaker: Joshua Yao-Yu Lin (National Taiwan University)

Title:  Impact of Gravitational Slingshot of Dark Matter on Galactic Halo Profiles
    We study the impact of gravitational slingshot effect from massive astrophysical 
objects (e.g. stars, black holes) on the distribution of cold dark matter in Milky Way 
sized galaxies and dwarf galaxies. Multiple gravitational encounters of a lower mass 
dark matter particle with massive astrophysical bodies would lead to an average 
energy gain for the dark matter, similar to second order Fermi acceleration. 
We calculate the average energy gain and model the integrated effect on the dark matter profile. 
We find that such slingshot effect due to the intermediate mass black holes in 
dwarf galaxies were significant in certain cases, which changes the dark matter distribution 
at the galactic center and several alleviate small scale problems of cold dark matter.

Papers of interests this week:

11:30 am, Friday, Sept 11th at PRB M2005 (Price Place)

Special Seminar
Time: 11:30- 12:00 
Speaker: Debtosh Chowdhury (INFN)

Title:  Dark Matter Annihilation to Fermions and a Photon
    We know from recent analyses that the inclusion of electroweak corrections can alter significantly
the energy spectra of Standard Model particles originated from dark matter annihilations. We are
interested in the process where radiation of photon has a significant contribution, in particular, 
where Majorana dark matter particle annihilate into a pair of light fermion. This process is helicity suppressed. 
The inclusion of photon radiation removes the p-wave suppression. We study this effect in detail using 
effective operators responsible for this process. We put bound on the effective operators considered from 
indirect dark matter searches and compare them with the bounds obtained from the direct and collider searches.

Papers of interests this week:

Summer 2015

11:30 am, Friday, Aug 28th at PRB M2005 (Price Place)

11:30 am, Friday, Aug 7th at PRB M2005 (Price Place)
  1. Boosting the Annihilation Boost: Semi-Analytic Model of Tidal Effects on Dark Matter Subhalos
  2. Missing energy and the measurement of the CP-violating phase in neutrino oscillations
  3. Comparison of the calorimetric and kinematic methods of neutrino energy reconstruction in disappearance experiments
  4. Performance of two Askaryan Radio Array stations and first results in the search for ultra-high energy neutrinos
  5. Neutrino detection at a spallation source
  6. Enhanced lines and box-shaped features in the gamma-ray spectrum from annihilating dark matter in the NMSSM
  7. Inflatable Dark Matter
  8. Coincidence charged-current neutrino-induced deuteron disintegration
  9. Cosmological Axion and neutrino mass constraints from Planck 2015 temperature and polarization data
  10. A measurement of the diffuse astrophysical muon neutrino flux using multiple years of IceCube data

11:30 am, Friday, July 10th at PRB M2005 (Price Place)

Special talk by Carsten Rott (Sungkyunkwan University, Korea)

Search for Dark Matter in the Sun
Dark Matter could be detected indirectly through the observation of neutrinos produced in self-annihilations or decays. Searches for such neutrino signals have resulted in the most stringent constraints on the lifetime of superheavy dark matter and world bests limits on spin-dependent scattering with matter. In recent years these searches have made significant progress in sensitivity through new search methodologies, new detection channels, and through the availability of rich datasets, foremost from the IceCube Neutrino Telescope. In this talk I will focus on the detection prospects for dark matter captured in the Sun by current and next-generation neutrino detectors.

11:30 am, Friday, June 19th at PRB M2005 (Price Place)
  1. Identifying the Theory of Dark Matter with Direct Detection
  2. Impact of the Geo-synchronous Orbit Radiation Environment on the Design of Astronomical Observatories
  3. Evidence for Unresolved Gamma-Ray Point Sources in the Inner Galaxy
  4. Strong support for the millisecond pulsar origin of the Galactic center GeV excess
  5. The Galactic Center GeV Excess from a Series of Leptonic Cosmic-Ray Outbursts
  6. Energy and Flux Measurements of Ultra-High Energy Cosmic Rays Observed During the First ANITA Flight
  7. Spectroscopy of geo-neutrinos from 2056 days of Borexino data
  8. Indirect Dark Matter Signatures in the Cosmic Dark Ages I. Generalizing the Bound on s-wave Dark Matter Annihilation from Planck
  9. Indirect Dark Matter Signatures in the Cosmic Dark Ages II. Ionization, Heating and Photon Production from Arbitrary Energy Injections
  10. Modelling the flux distribution function of the extragalactic gamma-ray background from dark matter annihilation
  11. Constraints on dark matter interactions with standard model particles from CMB spectral distortions
  12. A black hole window into p-wave dark matter annihilation

11:30 am, Friday, May 29th at PRB M2015 (the Seminar Room)

Special talk (1) by Yoshiyuki Inoue (ISAS/JAXA)

Probing the nature of AGN coronae through future X-ray and sub-mm observations
While the cosmic X-ray background is likely to originate from individual AGNs, the origin of the cosmic MeV gamma-ray background is not fully understood. We proposed that AGNs having non-thermal electrons in coronae may explain the MeV background. Such non-thermal electrons are expected to exist if a corona is heated by magnetic reconnections. However, the sensitivity of current MeV gamma-ray instrument is not sufficiently good to detect the expected power-law tail in the MeV band from individual AGNs. Furthermore, the heating mechanism of coronae in AGNs is still unknown, although magnetic reconnection heating is one possibility.  In this talk, I would like to introduce how we can probe the origin of the MeV background and the nature of AGN coronae such as magnetic field and non-thermal content through future observations by ASTRO-H and ALMA. 

Special talk (2) by Irene Tamborra (GRAPPA)

High energy neutrinos from extra-galactic astrophysical sources
The IceCube neutrino telescope recently discovered a flux of astrophysical neutrinos with energies up to few PeV.  In light of the new born high-energy neutrino astronomy era, I will discuss the expected high-energy neutrino emission from extra-galactic astrophysical sources as well as our chances to unveil the physics of the cosmic accelerators by employing neutrinos and their photon counterparts. 

11:30 am, Friday, May 22th at PRB M2005 (Price Place)

Special talk (1) by Scott Adams (OSU)

Not with a Bang, but a Whimper: Evidence for Low-energy Supernovae
I will present new HST and Spitzer late-time imaging of SN 2008S and NGC 300-OT,
the prototypes of a class of stellar transients whose true nature is debated. Both
objects have faded below the luminosity of their progenitors and are now undetected
in both the near and mid-IR, providing strong evidence that these events were
terminal. This, combined with the mass constraints on the progenitors, indicates that
this class of transients likely arise from electron-capture supernovae.

Special talk (2) by Kimberly Boddy (University of Hawaii)

Indirect Detection of Dark Matter Using MeV-Range Gamma-Ray Telescopes
The astrophysics community is considering plans for a variety of gamma-ray telescopes in the energy range 1--100 MeV, which can fill in the so-called "MeV gap" in current sensitivity. We investigate the utility of such detectors for the study of low-mass dark matter annihilation or decay. For annihilating (decaying) dark matter with a mass below about 140 MeV (280 MeV) and couplings to first generation quarks, the final states will be dominated by photons or neutral pions, producing striking signals in gamma-ray telescopes. We determine the sensitivity of future detectors to the kinematically allowed final states. In particular, we find that planned detectors can improve on current sensitivity to this class of models by up to a few orders of magnitude.

11:30 am, Friday, May 15th at PRB M2005 (Price Place)

Special talk by Ilias Cholis (Fermilab)

The Fermi Galactic Center excess
 The possible gamma-ray excess in the inner Galaxy and the Galactic center suggested by Fermi-LAT observations has triggered great interest in the astro-particle physics community. Among its various interpretations have been WIMP dark matter annihilations, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the GC. Given that the galactic diffuse emission is the dominant (by an order of magnitude or more) at any direction greater than 2 degrees from the GC understanding the background systematics has been a vital missing piece in the discussion. I will present the first comprehensive study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission at Galactic latitudes between 2 and 20 degrees and energies 300 MeV to 500 GeV. I will show both theoretical and empirical model systematics, which are deduced from a large range of Galactic diffuse emission models and a principal component analysis of residuals in numerous test regions along the Galactic plane. The hypothesis of an extended spherical excess emission with a uniform energy spectrum is compatible with the Fermi-LAT data in the region of interest at 95% CL.  Assuming that this excess is the extended counterpart of the one seen in the inner few degrees of the Galaxy, a lower limit of 10 degrees (95% CL) can be derived on its extension away from the GC.  In light of the large correlated uncertainties that affect the subtraction of the Galactic diffuse emission in the relevant regions, the energy spectrum of the excess is equally compatible with both a simple broken power-law of break energy 2.1 $\pm$ 0.2 and with spectra predicted by the self-annihilation of dark matter, implying in the case of $\bar{b}b$ final states a dark matter mass of 49$^{+6.4}_{-5.4}$ GeV. 
I will also briefly discuss interpretations of this excess, based on annihilating DM, leptonic CR outburst and a population of millisecond pulsars.

Spring 2015

11:30 am, Friday, May 1st at PRB M2005 (Price Place)
Special talk by Walter Winter (DESY Zeuthen, Germany)

Interpretation of IceCube results in the multi-messenger context
The discovery of high-energetic cosmic neutrinos is one of the recent
major breakthroughs in science. We discuss the concept of the neutrino
production, and interpret recent results taking into account the
information from other messengers (gamma-rays, cosmic rays). For
example, one question is if these neutrinos come from the most powerful
accelerators in the universe, i.e., the ones which can accelerate cosmic
rays to the highest observed energies. We also discuss future
perspectives for neutrino astronomy.

11:30 am, Friday, April 24th at PRB M2005 (Price Place)
Special talk(~30 mins) by Laura Lopez (CfA, Harvard)

Observational Tests of Cosmic-ray Diffusion in the Magellanic Clouds
Cosmic rays (CRs) play an important role in the interstellar medium: they ionize
dense molecular gas, they are responsible for the light elements in the periodic 
table, and they account for 20% of the ISM energy budget. However, the means
by which CRs are first accelerated and then transported through external
galaxies are not well understood. I will present results from a recent study of the
Magellanic Clouds to constrain CR transport using Fermi gamma-ray 
observations. I will show how we have characterized the spatial distribution of
gamma rays in the LMC and SMC and used the findings, in conjunction with 
available multiwavelength data, to constrain CR transport based on how the 
emission depends on physical parameters, such as gas density, massive star
formation, magnetic field structure, and turbulence properties.

AstroParticle lunch paper list:

12:30 pm, Friday, April 17th at PRB M2005 (Price Place)

  1. Dark matter annihilation and decay profiles for the Reticulum II dwarf spheroidal galaxy
  2. Stellar Kinematics and Metallicities in the Ultra-Faint Dwarf Galaxy Reticulum II
  3. Young Pulsars and the Galactic Center GeV Gamma-ray Excess
  4. Measurement of the Atmospheric νe Spectrum with IceCube
  5. A Combined Limit on the Neutrino Mass from Neutrinoless Double-Beta Decay and Constraints on Sterile Majorana Neutrinos
  6. Halo-Independent Direct Detection Analyses Without Mass Assumptions
  7. The behaviour of dark matter associated with 4 bright cluster galaxies in the 10kpc core of Abell 3827
  8. Improved Limits on Sterile Neutrino Dark Matter using Full-Sky Fermi-GBM Data
  9. AMS-02 antiprotons, at last! Secondary astrophysical component and immediate implications for Dark Matter
  10. On Detecting Millisecond Pulsars at the Galactic Center
  11. What could we learn from a sharply falling positron fraction?
  12. Comment on AMS02 results support the secondary origin of cosmic ray positrons

New AMS results this week!

12:30 pm, Friday, April 10th at PRB M2005 (Price Place)

Special talk!

Sam Stafford (OSU)
Analysis Interferometry of the Antarctic Impulse Transient Antenna (ANITA)

    Ultra-high energy (UHE) neutrinos may facilitate observation of sources in the
remotest parts of the universe.  A flux of UHE (E > 10^18eV) neutrinos is expected
from interaction of UHE cosmic rays with the cosmic microwave background.  
The Antarctic Impulse Transient Antenna (ANITA) campaign is a NASA Long-duration
balloon mission searching for coherent radio emission induced by ultra-high energy
neutrinos interacting in the Antarctic ice, as well as by UHE cosmic ray particle
cascades in the air.  The third ANITA flight began in December 2014 and lasted 
for 22 days.  I give a general description of the ANITA-III payload and flight, and 
present analysis methods to be used in identifying and localizing radio pulse events.

12:30 pm, Friday, March 13th at PRB M2005 (Price Place)

Dwarf papers!
  1. Beasts of the Southern Wild. Discovery of a large number of Ultra Faint satellites in the vicinity of the Magellanic Clouds
  2. Evidence for Gamma-ray Emission from the Newly Discovered Dwarf Galaxy Reticulum 2
  3. Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data
  4. Search for Gamma-Ray Emission from DES Dwarf Spheroidal Galaxy Candidates with Fermi-LAT Data
  5. Searching for Dark Matter Annihilation from Milky Way Dwarf Spheroidal Galaxies with Six Years of Fermi-LAT Data

12:30 pm, Friday, February 13th at PRB M2005 (Price Place)
  1. Evidence for dark matter in the inner Milky Way
  2. Flavor Ratio of Astrophysical Neutrinos above 35 TeV in IceCube
  3. Searching for Dark Matter Annihilation to Monoenergetic Neutrinos with Liquid Scintillation Detectors
  4. CMB Constraints On The Thermal WIMP Annihilation Cross Section
  5. Constraints on decaying dark matter from the extragalactic gamma-ray background
  6. Constraints on an Annihilation Signal from a Core of Constant Dark Matter Density around the Milky Way Center with H.E.S.S
  7. A limit on the ultra-high-energy neutrino flux from lunar observations with the Parkes radio telescope
  8. Signals from dark atom formation in halos
  9. Spectral analysis of the high-energy IceCube neutrinos
  10. The Knee of the Cosmic Hydrogen and Helium Spectrum below 1 PeV Measured by ARGO-YBJ and a Cherenkov Telescope of LHAASO
  11. Effects of axions on Nucleosynthesis in massive stars
  12. Effect of first forbidden decays on the shape of neutrino spectra
  13. Which is the flavor of cosmic neutrinos seen by IceCube?

12:30 pm, Friday, January 16th at PRB M2005 (Price Place)