NPAC (Nuclear/Particle/Astro/Cosmo) Forum

Host: 
Stefan Westerhoff
Speaker: Kendall Mahn Columbia University

 

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Room and Building: 
4274 Chamberlin

The LHC is expected to shed light on the physics behind the mechanism of electroweak symmetry breaking, associated with the generation of mass of all known elementary particles. There are good reasons to think that the same physics is responsible for the origin of dark matter and, perhaps, of the observable matter-antimatter asymmetry. In this talk I will summarize the arguments that support the above statements and provide a few examples of the interplay between cosmology and collider physics at the LHC.

Host: 
M J Ramsey-Musolf
Speaker: Carlos E M Wagner Argonne National Laboratory & University of Chicago

 

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Room and Building: 
4274 Chamberlin
For a few decades it is clear that astronomy and particle physics share a number of interesting topics. The Large Synoptic Survey Telescope (LSST) is one of the newest proofs that these two significantly different communities can also effectively cooperate within one project. Construction of the unique 8.4-meter LSST telescope started earlier this year. The telescope will be equipped with a huge 3.2 Gigapixel camera and will have a field of view of 10 square degrees. During single 15-second exposures it will capture stars up to 25th magnitude, and the whole accessible sky will be covered every three nights. During 10 years of operation, the LSST will create a "movie of the deep space" - each spot on the sky will be imaged at least 300 times. After its completion in 2014, the LSST will be the most advanced surface tool for the mapping of dark energy and dark matter, and the most sensitive instrument for detection and identification of any transient sources. Thus, the LSST will e.g. collect an unprecedented number of supernovae and will identify the trajectories of most of the so-called Earth Threatening Asteroids. In my talk I will discuss the current status, the technical challenges, and the potential scientific impacts of the LSST project.
Host: 
Stefan Westerhoff
Speaker: Michael Prouza FZU Prague, Czech Republic

 

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Room and Building: 
4274 Chamberlin
Ultra-Cold Neutrons - UCN - (E < 350 neV) can be trapped in material bottles and with magnetic fields. The UCNA collaboration has recently measured the beta-decay electron distribution from polarized neutron decay for the first time using UCN. The use of UCN suppresses a variety of systematic experimental effects compared to previous experiments using cold neutron beams. This allows for precision measurements of some Standard Model electroweak observables as well as searches for new physics. Results from this new experiment will be discussed along with prospects for future measurements.
Host: 
Michael J Ramsey-Musolf
Speaker: Brad Filippone Caltech

 

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Room and Building: 
4274 Chamberlin
Gamma-ray burst (GRB) is one of the cosmic-ray acceleration sites,
and high-energy neutrino emission from GRBs has been expected in
various scenarios. Many predictions for prompt and afterglow emission were done in the pre-Swift era. Recently, Swift has shown several novel phenomena, which allows us to expect new possibilities for cosmic-ray acceleration and associated secondary particle emission. I will discuss cosmic-ray acceleration and neutrino emission in various scenarios of GRBs, motivated by recent observations and theoretical developments. The possible connection between ultra-high-energy cosmic rays (UHECRs) and GRBs will also be discussed.
Host: 
Teresa Montaruli
Speaker: Kohta Murase Kyoto University, Yukawa Institute

 

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Room and Building: 
4274 Chamberlin
Recent cosmic microwave background observations determined that 96 percent of the Universe is "dark" (dark energy and dark matter). Baryons account for only 4 percent of the Universe. However about a half of the baryons still remain to be observed. These are the "missing baryons". Since baryons are rather familiar and even exciting -- stars, galaxies, planets and creatures are all baryons -- it is a shame that we don't understand a large part of them. Simulations of the cosmic large scale structure formation predict that the missing baryons exist as intergalactic gas with a temperature of about one million K, the so-called warm-hot intergalactic medium (WHIM). If the WHIM exists, the highly ionized metals (O, Ne, etc) in the WHIM produce emission and/or absorption lines in the X-ray energy range. The limited sensitivity of the detectors, however, makes WHIM still undetected. We have been searching cluster vicinities for the evidence of the WHIM, where the existence of relatively denser and hotter WHIM is expected, through X-ray spectroscopy (more particularly, O and Ne emission/absorption features). Despite some early positive reports, evidence for the WHIM has not yet been obtained. But the upper limits of the signals we have from recent observations indicate that our sensitivity is reaching the expected signal level. I present the details of our study, mainly those from Suzaku (Japanese X-ray satellite), and then show the future prospects of this field.
Host: 
Dan McCammon
Speaker: Yoh Takei ISAS in Tokyo

 

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Room and Building: 
4274 Chamberlin

Cold atomic gases are all the rage in physics now. We can apply many-body techniques from nuclear physics, such as the interacting shell model, to cold gases; this way we learn a lot about how such calculations for nuclei are done.

Host: 
Michael J Ramsey-Musolf
Speaker: Calvin Johnson San Diego State University

 

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Room and Building: 
4274 Chamberlin
We propose a simple extension of the Minimal Supersymmetric Standard Model which
gives rise to thermal inflation, baryogenesis and dark matter in a natural and
remarkably consistent way.
We consider the $lambda_phi = 0$ special case of our previous model, which is the
minimal way to incorporate a Peccei-Quinn symmetry.
The axino becomes the lightest supersymmetric particle with $m_{ ilde{a}} sim 1
extrm{ to } 10 GeV$ and is typically over-produced during the flaton decay.
Interestingly though, the dark matter abundance is minimized for $m_{ ilde{a}} sim
1 GeV$, $f_a sim 10^{11} extrm{ to } 10^{12} GeV$ and $|mu| sim 400 GeV
extrm{ to } 1 TeV$ at an abundance coincident with the observed abundance and
with significant amounts of both axions and axinos.
Futhermore, for these values the baryon abundance naturally matches the observed
abundance.
As an observable, thermal inflation which is the key idea of the model produces a
background of gravitational waves.
It is likely to be detected at BBO and DECIGO style direct detection experiments.
Host: 
Dan Chung
Speaker: Wan-Il Park KAIST

 

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Room and Building: 
4274 Chamberlin

Disparate astronomical observations provide compelling evidence for additional, non-luminous matter, or dark matter, in gravitational interactions, but we know little of its nature. To remedy this, the hunt is on to detect dark matter via either direct or indirect means, to determine its mass(es?) as well as couplings to Standard Model particles. I will briefly review the astronomical evidence and summarize current direct and indirect detection efforts before describing a new possibility. That is, a Faraday rotation experiment can set limits on the magnetic moment of a electrically-neutral, dark-matter particle, and the limits increase in stringency as the candidate mass decreases. I shall describe how such could be realized and determine the limits on the magnetic moment as a function of mass which follow given demonstrated experimental capacities.

Host: 
M J Ramsey-Musolf
Speaker: Susan Gardner University of Kentucky

 

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Room and Building: 
5280 Chamberlin
The technique of parity-violating electron scattering, involving measurements of the asymmetry in the scattering of longitudinally polarized electrons off fixed targets, has become increasingly precise and broad in its scope over the past two decades. Such asymmetries are sensitive to weak neutral current interactions (mediated by the Z boson) between electrons and quarks, or between two electrons, and are being used to investigate the strangeness content of the nucleon, the neutron distribution in heavy nuclei and to probe for the limits of the validity of the electroweak theory in a manner complementary to direct searches for new physics at high energy scales at colliders.
In this talk, we focus on the last of the abovementioned topics. We begin by motivating and describing the results of the E158 experiment at the Stanford Linear Accelerator Center. We then discuss an ongoing project and possible future complementary measurements that can be carried out at Jefferson Laboratory. The first experiment will be carried out with a 1 GeV electron beam. With the completion of the 12 GeV upgrade, further precise measurements become feasible, in parity-violating deep inelastic scattering and in electron-electron scattering. In particular, the latter measurement could potentially lead to a measurement of the mixing angle with precision equal to or better than the two best collider measurements. In deep inelastic scattering, apart from testing the electroweak theory, the measurements would provide new precision probes the valence quark structure of the nucleon. Some aspects of the experimental challenges in carrying out this ambitious program will also be discussed.
Speaker: Krishna Kumar UMass

 

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Room and Building: 
5280 Chamberlin

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