NPAC (Nuclear/Particle/Astro/Cosmo) Forum

I shall describe a bottom-up approach to modeling low-energy properties of QCD using holographic duality. Chiral symmetry and its breaking, QCD sum rules as well as asymptotic scaling are simultaneously realized in such models. The simplest model of this type gives a remarkably good fit to many low energy hadronic observables.

Host: 
M J Ramsey-Musolf
Speaker: Misha Stephanov U. Illinois Chicago

 

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Room and Building: 
4274 Chamberlin
Extension of the minimal supersymmetric standard model (MSSM) that include a U(1)' gauge symmetry are motivated by top-down
constructions and offer an elegant solution to the MSSM mu problem.

In this talk I will describe some of the opportunities that such models offer, such as a new mechanism for mediation of supersymmetry breaking, as well as some of the challenges in constructing viable supersymmetric U(1)' models.
Host: 
Michael J. Ramsey-Musolf
Speaker: Gil Paz Institute for Advanced Study, Princeton

 

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Room and Building: 
4274 Chamberlin

Helium-8 (8He) is the most neutron-rich matter to have been synthesized on the Earth: it consists of two protons and six neutrons, and remains stable for an average of 0.2 seconds. It is often viewed as a 4He core with four additional neutrons orbiting at a relatively large distance, forming a halo. Because of its intriguing properties, 8He has the potential to reveal new aspects of the fundamental forces among the constituent nucleons. We have recently succeeded in laser trapping and cooling this exotic helium isotope, and have performed precision laser spectroscopy on individual trapped atoms. Based on the atomic frequency differences measured along the isotope chain 3He - 4He - 6He - 8He, the nuclear charge radius of 8He has now been determined for the first time. Comparing this result with the values predicted by a number of nuclear structure calculations, we test theoretical understanding of the nuclear forces in the extremely neutron-rich environment. Moreover, this method of capturing and probing atoms of rare isotopes is also applied to experiments that test fundamental symmetries and to applications of ultrasensitive trace analysis.

Host: 
Karsten Heeger
Speaker: Zheng-Tian Lu Argonne National Laboratory an University of Chicagod

 

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Room and Building: 
4274 Chamberlin

Baryon acoustic oscillations (BAO) in large galaxy surveys can provide an excellent standard ruler test to measure the cosmological distance scale, such as the angular diameter distance and the Hubble parameter, and therefore dark energy properties. This requires that we understand all of the physical effects that could alter the acoustic feature during the nonlinear evolution of structure. There are two important aspects of the nonlinear effects on BAO. First, the BAO signature is gradually reduced with time and in scale due to nonlinear growth of density fields, redshift distortions, and galaxy bias. Second, the various nonlinear effects may alter the observed BAO scale at low redshift, relative to the linear acoustic scale derived from the CMB, which would result in biased estimation of dark energy parameters. In this talk, I will present effects of such nonlinearities on BAO from N-body results: nonlinear growth and redshift distortions degrade the contrast of BAO while shifting BAO less than ~0.5% at z=0.3. I will show that most of these nonlinear effects can be reversed by a simple reconstruction scheme.I will also discuss the effect of galaxy bias on BAO.

Host: 
Peter Timbie
Speaker: Hee-Jong Seo Fermilab and U. Arizona

 

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Room and Building: 
5310 Chamberlin
Quark matter at high density and low temperature is expected to be a color superconductor, which is a degenerate Fermi gas of quarks with a condensate of Cooper pairs near the Fermi surface. At the highest densities, where the QCD coupling is weak, rigorous calculations are possible, and the ground state is a particularly symmetric state, the color-flavor locked (CFL) phase. At lower densities the CFL phase suffers from flavor-symmetry-breaking stresses, so alternative phases,
some of which break translation and/or rotation invariance, may be favored. I will review the state of our understanding of these phenomena, and discuss the effort to develop signatures of the presence of color superconducting quark matter in neutron stars.
Host: 
Michael J. Ramsey-Musolf
Speaker: Mark Alford Washington University

 

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Room and Building: 
4274 Chamberlin
Octave-spanning, mode locked femtosecond laser frequency combs convert
the most precise instrument available today - the atomic clock - to the frequency domain, providing an equally precise yardstick for wavelength calibration, potentially 1:10^15. Precision at this level enables astronomical radial velocity measurements to 1 cm/sec over decadal time scales. This capability will make it possible to search for earth-like planets orbiting solar type-stars in the habitable zone and to measure the expansion of the universe directly, as well as to explore the local distribution of dark matter and to search for variations of fundamental constants over cosmological time scales. I discuss the techniques, status and potential of this instrumentation as well as ongoing and future observational programs in pursuit of these scientific objectives.
Host: 
Francis Halzen
Speaker: Andrew Szentgyorgyi Harvard CFA

 

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Room and Building: 
4274 Chamberlin
With the installation of the last two lines in May 2008, ANTARES (Astronomy with a Neutrino Telescope and Abyss environmental RESearch) is currently the largest neutrino detector in the Northern Hemisphere. The detector consists of 12 lines, carrying
almost 900 ten-inch photomultipliers (PMTs), placed at a depth of 2500 m in the Mediterranean Sea, about 40 km offshore Toulon in South France. The PMTs detect the Cerenkov light emitted by muons from neutrino charged current interactions in the surrounding seawater and the rock below. The information provided by the number of photons detected and their arrival times is used to infer the neutrino track direction. Thanks to its exceptional angular resolution, better than 0.3◦ above 10 TeV, ANTARES
is especially suited for the search of astrophysical point-like sources. The first data collected with the 5-Line detector, which covers the period from January to December 2007, have been analyzed to look for a possible neutrino excess from a
list of prospective neutrino sources. In this talk, the current status of the ANTARES neutrino telescope, including the first
results obtained from the analysis of the 5-Line data, will be presented.
Host: 
Teresa Montaruli
Speaker: Simona Toscano Valencia

 

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Room and Building: 
4274 Chamberlin
We examine the nature of electroweak Baryogenesis when the Higgs boson's properties are modified by the effects of new physics. We utilize the effective potential to one loop while retaining parametrically enhanced dimension six operators of O(v^2/f^2) in the Higgs sector. These parametrically enhanced operators would be present if the Higgs is a pseudo-goldstone boson of a new physics sector with a characteristic mass scale Lambda ~ a few TeV, a coupling constant (4 pi) > g > 1 and a strong decay constant scale f = Lambda/g. We find that generically the effect of new physics of this form allows a sufficiently first order electro-weak phase transition so that the produced Baryon number can avoid washing out, and has enhanced effects due to new sources CP violation. The conditions we find for pseudo-goldstone baryogenesis to occur are examined in the context of Little Higgs models, and are found to give surprising insights into the nature of some of the viable parameter space for Little Higgs models.
Host: 
S Mantry
Speaker: Mike Trott Perimeter Institute

 

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Room and Building: 
4274 Chamberlin

I will describe the scientific and technical issues concerning building a very large detector at the new Homestake deep underground science and engineering laboratory and a new intense neutrino beam from Fermilab.

Host: 
Albrecht Karle
Speaker: Milind Diwan BNL

 

Available Downloads:

Room and Building: 
4274 Chamberlin
Tolman pointed out that if a cyclic universe model has<br>
to be consistent with the second law of<br>
thermodynamics, the cycles must inevitably shrink to<br>
zero as one goes back in time (cycles). I will provide<br>
a simple cosmological paradigm which avoids this<br>
&quot;super Big Bang&quot;. Moreover we will see that in these<br>
&quot;Emergent cyclic models&quot; new mechanisms for generating<br>
scale-invariant fluctuations can naturally emerge.<br>
<br>
Host: 
Daniel Chung
Speaker: Tirthabir Biswas Pennsylvania State University

 

Available Downloads:

Room and Building: 
5280 Chamberlin

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