NPAC (Nuclear/Particle/Astro/Cosmo) Forum

Due to their outstanding property to be storable and hence observable for long periods of time (several hundreds of seconds) in suitable material or magnetic traps, ultra-cold neutrons (UCN)with energies around 100 neV are an unique tool to study fundamental properties of the free neutron. Their properties and production are described in detail. Selected experiments with ultra-cold neutrons (UCN) - the measurement of its lifetime and the search for an electric dipole moment - performed at the instrument "Physique Fondamentale 2 (PF2)" of the Institut Laue-Langevinn (ILL) are highlighted. For particles to have electric dipole moments, the forces concerned in their structure must be asymmetric with regard to space-parity (P) and time reversal (T). P violation is a well-known intrinsic feature of the weak interaction which is responsible for the beta-decay of the free neutron. T violation turns out to be necessary to explain the survival of matter at the expense of antimatter after the Big Bang. By searching for an EDM of the free neutron hypothetical new channels of T-violation can be investigated. The experiments at the ILL will be compared to competing EDM projects worldwide. The measurement of the lifetime of the free neutron together with the determination of one of the correlation parameters characterizing neutron decay allows tests of the Standard Model. Furthermore, the neutron lifetime plays an important role in Big-Bang Nucleosynthesis cosmology. Up to 180 s after the big-bang nuclei with more than one nucleon are unstable. The neutron lifetime determines how many neutrons have decayed up to this moment and hence the relative helium abundance in the universe. The different methods to measure the lifetime of the free neutron are reviewed and the latest experiments using storage of UCN at the ILL are described in detail. A brief outlook on future projects worldwide will be given.
Host: 
Michael Ramsey-Musolf
Speaker: Peter Geltenbort Institute Laue-Langevin, Grenoble

 

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Room and Building: 
4274 Chamberlin
I will discuss electroweak baryogenesis (EWBG) in supersymmetric
U(1)' models. Unlike the usual wisdom, a spontaneous CP violation
plays a key role in this picture. This makes the EWBG in the U(1)'
models be very different from what happens in the minimal
supersymmetric standard model. I will also show that a successful
EWBG and an acceptable neutralino dark matter relic density can be
simultaneously achieved in our models.
Host: 
Michael Ramsey-Musolf
Speaker: Tao Liu University of Chicago

 

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Room and Building: 
4274 Chamberlin
Host: 
Segev BenZvi
Speaker: Petra Huentemeyer Michigan Technological University

 

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Room and Building: 
4274 Chamberlin
Host: 
Timbie
Speaker: Ted Bunn University of Richmond

 

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Room and Building: 
4274 Chamberlin Hall
Recent cosmic ray data, notably from the Pamela and Fermi satellites, indicate that previously unaccounted-for powerful sources in the Galaxy inject high-energy electrons and positrons. Interestingly, this new source class might be related to new fundamental particle physics, and specifically to pair-annihilation or decay of galactic dark matter. I will
discuss how this exciting scenario is constrained by Fermi gamma-ray observations, and which astrophysical source counterparts could also be responsible for the high-energy electron-positron excess. In particular, I will review the case for nearby mature pulsars, and the impact of newly
discovered radio-quiet pulsars that pulsate in gamma rays. While
high-energy electron-positron measurements sample local (closer than 1 kpc) cosmic rays, diffuse radio and gamma-ray emission informs us about the global galactic cosmic ray population. I will thus offer a few thoughts on recent claims involving the detection of diffuse radio ("WMAP haze") and gamma-ray ("Fermi haze") emissions and on implications for the quest for New Physics
Host: 
Michael Ramsey-Musolf
Speaker: Stefano Profumo U.C. Santa Cruz

 

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Room and Building: 
4274 Chamberlin
Host: 
Baha Balantekin
Speaker: Fedor Simkovic Comenius University

 

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Room and Building: 
4274 Chamberlin
A high energy hadron can be visualized as a Lorentz contracted core of valence partons accompanied by a furry sea of wee partons. The many-body properties of these wee
partons and their evolution with energy can be described by a weak coupling effective field theory called the Color Glass Condensate (CGC). Novel factorization theorems allow us to understand quantitatively the early time
dynamics of heavy-ion collisions when two CGCs shatter forming a classical fluid called the Glasma. We discuss the properties of this Glasma and some of its experimental manifestations in heavy-ion collisions.
If time permits, we shall outline outstanding conceptual issues in understanding the evolution of the Glasma into the Quark-Gluon Plasma.
Host: 
Michael Ramsey-Musolf
Speaker: Raju Venugopalan Brookhaven National Laboratory

 

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Room and Building: 
4274 Chamberlin

I explore the possibility that rotational or translational invariance is violated during the inflationary era but restored at the end of the inflationary era. This possibility is constrained by data on the microwave background anisotropy. Some particular inflationary models are discussed.

Host: 
Pavel Fileviez Perez
Speaker: Mark B. Wise Caltech

 

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Room and Building: 
5280 Chamberlin
Thursday, March 25th, 2010
Host: 
Baha Balantekin
Speaker: David Ernst Vanderbilt University

 

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Room and Building: 
4274 Chamberlin

The assumed isotropy of galactic cosmic rays has been topic of investigation since the seventies, when an O(10^-3 - 10^-4) anisotropy in arrival direction has been observed for the first time. The wide energy range of this observations (from tens of GeV to hundreds of TeV) has raised questions on the origin of this phenomenon. While we can generically claim that the responsible of this anisotropy is to be connected to the structure of the Local Interstellar Medium, and specifically to the Local Interstellar Magnetic Field (within about 0.1-1.0 pc ~ 20,000 - 200,000 AU), we still suffer from the lack of knowledge of the properties of our local environment. Only recently, with the observation of O(10-30 degrees) excess of cosmic rays by MILAGRO and with the first high statistics observation of the southern sky by IceCube, the topic is gaining renewed attention. The possibility that the ~100's TeV galactic cosmic ray anisotropy might be connected to the blast from a nearby supernova, in connection with the anomalies in the observed positron fraction and electron spectrum is very appealing and will be discussed.

Host: 
Michael Ramsey-Musolf
Speaker: Paolo Desiati University of Wisconsin at Madison

 

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Room and Building: 
5310 Chamberlin

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