Nuclear Theory Seminars at Texas A&M: Spring 2016

Location: Cyclotron Conference Room (CYCL-300)

January 25, 4:00pm
      C.Y. Wong (Oak Ridge)
"The Hadron p_T Distribution in High-Energy pp Collisions and its Implications "

Transverse momentum distribution of jets and hadrons provide useful information on the collision mechanisms and their subsequent dynamics. It was found recently that the hadron spectra spanning over 14 decades of magnitude from the lowest of 0.5 GeV/c to the highest $p_T$ of a few hundred GeV/c at central rapidity in pp collisions at LHC can be adequately described by a single Tsallis distribution with only three apparent degrees of freedom [1]. The simplicity of the p_T spectrum suggests that a single mechanism dominates over a large pT domain at central rapidity in these high-energy collisions. As the high-$p_T$ region is known to arise from the relativistic hard-scattering process at high pT, one is led to the suggestion that the hard-scattering process dominates over a very large pT domain in these high-energy pp collisions. We shall explore the implications of the pT distribution on many related topics of the diminishing role of the competing flux-tube fragmentation [2] and the initial conditions for the momentum kick model of the near-side ridge in pp collisions [3].

[1] C.Y.Wong and G.Wilk, Acta Phys. Pol. {B43}, 2047 (2012); C.Y.Wong and G.Wilk, Phys. Rev. {D87},114007 (2013); C. Y. Wong, G. Wilk, L. J. L. Cirto and C. Tsallis, Phys. Rev. {D91}, 114027 (2015).
[2] C.Y.Wong, Phys.Rev. {D92}, 074007 (2015).
[3] C.Y.Wong, Phys.Rev. {C84}, 024901 (2011).

January 27, 11:00am (CYCL-228)
      W.C. Chen (Florida State)
"Relativistic Mean Field Models for Finite Nuclei and Neutron Stars"

Relativistic mean field (RMF) theory provides a natural framework to describe nuclear systems, ranging from finite nuclei, nuclear matter, to neutron stars, in a single unified way. In this talk I will introduce a calibration scheme to build RMF models using only real physical observables; properties of nuclear matter, such as incompressibility and symmetry energy, become genuine model predictions. Moreover, I will demonstrate how a follow-up covariance analysis can extract information content of the models, including theoretical uncertainties and correlations. This calibration scheme has been applied to study the elusive isovector sector and related physics. Comparing with experimental and theoretical constraints, we find that the neutron-skin thickness in 208Pb should be (0.16 ± 0.1) fm, implying a soft symmetry energy with J = ( 30.92 ± 0.47 ) MeV and L = (51.0 ± 1.5) MeV, respectively. The optimal model can also correctly locate the neutron drip line of oxygen at 24O and predicts that of calcium to be at 60Ca. Then, I will turn to discuss the recent tension between dense matter theory and the observation of neutron stars with very small radius (less than 10.6 km). We find that in order to support two-solar-mass neutron stars while preserving causality, the typical stellar radius must be greater than 10.7 km—barely consistent with recent analyses.

February 1, 4:00pm
      S. Cho (Kangwon National University, Korea)
"Reduction of the K* meson abundance and freeze-out conditions in heavy ion collisions"

We discuss the reduction of the K* meson abundance during the hadronic stage in heavy ion collisions. We also investigate the freeze-out conditions of a particle in order to understand the productions of resonances, hadronic molecules and light nuclei in heavy ion collisions. Applying the kinetic freeze-out condition to the daughter particles of K* mesons, we find that the larger suppression of the yield ratio of K*/K at LHC than at RHIC compared to the expectations from the statistical hadronization model reflects the lower kinetic freeze-out temperature at LHC than at RHIC. Furthermore, we argue that for the light nuclei or hadronic molecules that are bound, the yields are affected by the freeze-out condition of the respective particle in the hadronic matter, which leads to the observation that the deuteron production yields are independent of the size of deuteron, and depend only on the number of ground state constituents.

February 3, 4:00pm
      S.H. Lee (Yonsei University, Korea)
"Few recent results on D meson in matter and dibaryons in constituent quark model"

We probe effects of the partial chiral symmetry restoration to the mass of heavy-light mesons in a constituent quark model by changing the constituent quark mass of the light quark. Due to the competing effect between the quark mass and the linearly rising potential, whose contribution to the energy increases as the quark mass decreases, the heavy-light meson mass has a minimum value near the constituent quark mass typically used in the vacuum. Hence, the meson mass increases as one decreases the constituent quark mass consistent with recent QCD sum rule analyses, which show an increasing $D$ meson mass as the chiral order parameter decreases. We will also present some recent result on dibaryons in a constituent quark model.

Previous seminars

Fall 2014
Spring 2014
Spring 2013
Spring 2012
Fall 2011
Spring 2011
Fall 2010
Spring 2010
Fall 2009
Spring 2009
Fall 2008
Spring 2008
Fall 2007
Spring 2007
Fall 2006
Spring 2006
Fall 2005
Spring 2005
Fall 2004
Spring 2004
Fall 2003

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