NPAC (Nuclear/Particle/Astro/Cosmo) Forum

I will summarize and discuss the body of evidence which has accumulated in favor of dark matter in the form of approximately 10 GeV particles. This evidence includes the spectrum and angular distribution of gamma rays from the Galactic Center, the synchrotron emission from the Milky Way's radio filaments, the diffuse synchrotron emission from the Inner Galaxy (the "WMAP Haze") and low-energy signals from the direct detection experiments DAMA/LIBRA, CoGeNT and CRESST-II. This collection of observations can be explained by a relatively light dark matter particle with an annihilation cross section consistent with that predicted for a simple thermal relic (sigma v ~ 10^-26 cm^3/s) and with a distribution in the halo of the Milky Way consistent with that predicted from simulations. Astrophysical explanations for the gamma ray and synchrotron signals, in contrast, have not been successful in accommodating these observations. Similarly, the phase of the annual modulation observed by DAMA/LIBRA (and now supported by CoGeNT) is inconsistent with all known or postulated modulating backgrounds, but are in good agreement with expectations for dark matter scattering. This scenario is consistent with all existing indirect and collider constraints, as well as the constraints placed by CDMS. Consistency with xenon-based experiments can be achieved if the response of liquid xenon to very low-energy nuclear recoils is somewhat suppressed relative to previous evaluations, or if the dark matter possesses different couplings to protons and neutrons.
Host: 
Reina Maruyama
Speaker: Dan Hooper Fermilab / University of Chicago

 

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4274 Chamberlin Hall

The RENO experiment has observed the disappearance of reactor electron antineutrinos, consistent with neutrino oscillations, with a significance of 4.9 standard deviations. Antineutrinos from six reactors at Yonggwang Nuclear Power Plant in Korea, are detected by two identical detectors located at 294 m and 1383 m, respectively, from the reactor array center. In the 229 day data-taking period of 11 August 2011 to 26 March 2012, the far (near) detector observed 17102 (154088) electron antineutrino candidate events with a background fraction of 5.5% (2.7%). A ratio of observed to expected number of antineutrinos in the far detector is 0.920+-0.009(stat.)+-0.014(syst.). From the deficit, we find sin^2(2theta_13)=0.113+-0.013(stat.)+-0.019(syst,) based on a rate-only analysis. In this talk, its detailed analysis will be presented.

Host: 
Karsten Heeger
Speaker: Soo-Bong Kim Seoul National University

 

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4274 Chamberlin Hall
The rapid spins and intense magnetic fields (109 - 1014 Gauss) of pulsars accelerate particles to very high energies, both in their magnetospheres and in relativistic winds, powering emission from radio waves to the highest energy gamma-rays. NASA's Fermi Gamma-Ray Space Telescope, launched in 2008, has proved to be a powerful tool for studying these systems. Fermi observations have increased the population of known gamma-ray pulsars from 6 to more than 100. New classes of gamma-ray pulsars, including millisecond and radio-quiet pulsars, have emerged. With its unprecedented sensitivity, Fermi has transformed our understanding of the energetic particle accelerators in our Galaxy and thereby linked observations of the sky at the highest photon energies (1012 eV) with those at the lower end of the electromagnetic spectrum. In my talk I will discuss some of the new and exciting results from Fermi and focus on how these discoveries integrate with the overall picture of pulsars and their nebulae that covers some 20 decades of energy.
Host: 
Halzen
Speaker: Aous Abdo George Mason University

 

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4274 Chamberlin Hall

In one of the planet's most extreme environments, South Pole Station Antarctica, scientists have instrumented more than a cubic kilometer of ice to construct the world's largest neutrino detector to date: the IceCube Neutrino Observatory. Given its enormous size, IceCube is designed to detect the highest energy neutrinos predicted to be produced in the most violent astrophysical processes. The milestone deployment of the last of the observatory's 86 strings of optical detectors, in December 2010, included the completion of two noteworthy additions to the original design: a low-energy neutrino extension (DeepCore) and a prototype direct-detection dark matter detector (DM-Ice). These new detectors establish the first steps towards a precision particle astrophysics program in the Antarctic. The early results from this emerging and potentially game-changing program will be discussed. Also included will be the initial expectations of future detector upgrades in the ice towards large-scale direct detection dark matter searches and multi-megaton neutrino detectors with very low, O(10 MeV), energy thresholds.

Host: 
Halzen
Speaker: Darren Grant University of Alberta

 

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4274 Chamberlin Hall

Cosmic rays are primarily protons and other nuclei, but there is a small flux of electrons and an even smaller flux of positrons. Cosmic-ray positrons can be produced by astrophysical accelerators, by collisions of cosmic-ray protons with interstellar gas, or by dark matter. We used the Fermi Gamma-ray Space Telescope to measure the charge-separated electron and positron energy spectra. Because Fermi does not have an onboard magnet, we used the Earth's magnetic field to distinguish positrons and electrons. We confirmed the PAMELA discovery that the positron fraction is rising with energy between 10 and 100 GeV and measured the positron flux for the first time in the 100-200 GeV range. Explaining the positron excess remains an outstanding question.

Host: 
Halzen
Speaker: Justin Vandenbroucke SLAC

 

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5280 Chamberlin Hall
Lorentz violation is a predicted signal from Planck scale physics. Since neutrino oscillation experiments are natural interferometers, they may be sensitive to small space-time effect, such as Lorentz violation through their sidereal time dependence. The sensitivity is comparable to precision optical measurements (10E-19 GeV). Thus, neutrino oscillations may be the first place where we see Lorentz and CPT violation.<br>
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Recently the MiniBooNE neutrino oscillation experiment published electron and anti-electron neutrino appearance oscillation results that cannot be understood within the accepted three-massive-neutrinos oscillation model. In this talk, I will introduce Lorentz violation and Lorentz violating neutrino oscillations. Then, I examine whether the MiniBooNE data may be explained through a Lorentz violation model. Finally, I discuss how these results and other Lorentz violation tests address the &quot;superluminal neutrino observation&quot; from OPERA experiment.<br>
Host: 
Halzen
Speaker: Teppei Katori MIT

 

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The discovery of neutrino oscillation, which leads to a non-zero neutrino mass, creates a host of interesting questions with relevance to particle physics, astrophysics, cosmology and beyond. After a brief review, I will cover some of the major oscillation topics and how the DeepCore sub-array, a low-energy extension of the IceCube neutrino observatory, offers new opportunities for neutrino oscillation physics in the tens of GeV energy region. Possible future extensions designed to drive the energy reach down to ~1 GeV in an initial stage (PINGU) and tens of MeV in a second stage (MICA) will conclude the talk.<br>
Host: 
Halzen
Speaker: David Jason Koskinen Penn State

 

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5280 Chamberlin Hall

A century after the discovery of cosmic rays, the nature and origin of the highest energy particles in the Universe, the Ultra-High Energy Cosmic Rays (UHECR), remain enigmatic. Thanks to experiments dedicated to probing the extreme end of the energy spectrum, exciting progress is being made in solving these puzzles.The Pierre Auger Observatory is currently the World`s largest detector for UHECR. The goal is to measure the cosmic ray energy spectrum, arrival directions, and the properties of the extensive air showers induced by the UHECRs in the atmosphere with the objective of unveiling cosmic ray elemental composition, origins and propagation effects. The observatory has now collected more data than all previous experiments combined, and employs multiple detection (hybrid) detection techniques allowing for a large exposure and excellent control of systematic uncertainties. The original design, optimized for the energy range from 1018 eV to the end of the spectrum, has recently been enhanced to cover energies down to almost 1017 eV, allowing us to view additional interesting features of the spectrum. I will give an overview of the latest results with a focus on the current status of the search for ultra-high energy neutrinos and photons and the promising prospect to use cosmic rays to study hadronic interactions at energies beyond the reach of the LHC.

Host: 
Halzen
Speaker: Ines Valino Rielo University of Santiago de Compostela

 

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4274 Chamberlin Hall

The High Altitude Water Cherenkov (HAWC) experiment, under construction at Sierra Negra, Mexico, consists of a 22500 square meter area of water tanks instrumented with light-sensitive photo-multiplier tubes. The experiment detects energetic secondary particles reaching the ground when a high-energy cosmic ray or gamma ray interacts in the atmosphere above the experiment. High-energy gamma ray astronomy provides a probe of some of the most gravitationally and electromagnetically extreme regions in the universe, from neutron stars and supernova remnants to active galactic nuclei and gamma-ray bursts. High-energy gamma ray are also key to understanding the origin of galactic cosmic radiation. I will describe the design of the HAWC instrument, scheduled to be completed in 2014, and discuss the motivation and scientific return the experiment will bring.

Host: 
Halzen
Speaker: John Pretz Los Alamos National Lab

 

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Room and Building: 
5280 Chamberlin Hall
This talk will describe the possibility of probing scalar and tensor interactions
arising from new physics at the TeV scale at the two experiments, UCNb
and UCNB, being developed at the ultra-cold neutron source at Los Alamos.
I will show that the largest uncertainty is connecting theory to experiments
(with measurements at the 10^{-3} level), comes from estimates of the
scalar and tensor charges of a nucleon. I will then discuss the status of our lattice
QCD calculations of these matrix elements and plans for the future. As summary, a
discussion of current bounds on these novel interactions will be presented.
Speaker: Rajan Gupta Los Alamos National Laboratory

 

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