2016-2017 SEMINAR SCHEDULE


Elena Bratkovskaya (FIAS Frankfurt and GSI)
Electromagnetic emissivity of hot and dense matter
Wednesday, July 27, 3:30 PM
Duke Univ., Physics 298
 
The QCD matter produced initially in ultra-relativistic nucleus-nucleus collisions is expected to represent a high temperature plasma, which should be evidenced in its electromagnetic radiation. We analyze the production of real and virtual photons from the strongly-coupled QGP in the initial stages of the collisions as well as the ('corona') radiation from the interacting mesons and baryons after hadronization using the parton-hadron-string dynamics (PHSD) transport model. The description of the bulk evolution in the microscopic PHSD approach is independently controlled by abundances, spectra and flow of final hadrons, which are found to be in agreement with experimental observation. Direct photon production in elementary processes and heavy-ion reactions at RHIC and LHC energies is investigated and the status of the photon v2 puzzle - a large elliptic flow of the direct photons observed in A+A collisions - is addressed. We discuss the roles of hadronic and partonic sources for the photon spectra and the flow coefficients $v_2$ and $v_3$ and also the possibility to subtract the QGP signal from observables. Furthermore, the production of dilepton pairs is addressed from SIS to LHC energies. The low-mass dilepton yield is enhanced due to the in-medium modification of the rho-meson and at the lowest energy also due to a multiple regeneration of Delta-resonances. At intermediate dilepton masses the dominant contributions come from the thermal QGP dileptons and from correlated D-mesons decay which now calculated dynamically within the PHSD model. A signal of the partonic degrees-of-freedom is found to be visible in the intermediate dilepton mass regime (1.2GeV

Lusaka Bhattacharya (Kent State & Ohio State)
Photon production from anisotropic quark-gluon-plasma
Tuesday, Sept. 6, 3:30 PM
Duke Univ., Physics 298
 
We calculate the medium photon production due to Compton and annihilation processes by taking into account the (3+1)-dimensional anisotropic hydrodynamics of the quark gluon plasma (QGP) expected to be formed in relativistic heavy ion collisions. We have taken the momentum-space anisotropy into account in the computation of the photon production rate finally. We present the predictions for high-energy photon yields as a function of transverse momentum and rapidity. We conclude that high energy photon production is extremely sensitive to the assumed level of initial momentum-space anisotropy of the quark-gluon plasma.

JJ Cherry (Virginia Tech)
Reconstructing the Supernova Neutrino Burst
Tuesday, Oct. 11, 3:30 PM
NC State Univ., Riddick 400P
 
The neutrino burst from core collapse supernovae represents a tremendous opportunity to observe physical processes in the heart of an exploding star. The interactions of neutrinos with the matter in and around the proto-neutron star which powers the supernova provides an in-situ probe of the explosion. Details regarding the core compactness, neutron matter equation of state, shock behavior, nucleo-synthetic products, explosion time scale, fundamental neutrino properties and more may be detectable, in principle. However, the neutrino interactions in the envelope of the star can be considerably complicated by macroscopic quantum coherent effects of neutrinos forward scattering on the matter of the envelope as well as one another. I investigate the ability of the next generation of neutrino detectors to observe the presence of, and extract, these signals from realistic models of neutrino emission from supernovae which take account of coherent flavor oscillation effects in a time-dependent and consistent fashion.

Paulo Bedaque (Maryland)
Go with the flow: a solution to the sign problem
Tuesday, Oct. 25, 3:30 PM
NC State Univ., Riddick 400P
 
We discuss a new approach to solve the sign problem arising in the Monte Carlo evaluation of path integrals. It is based on deforming the contour of integration into complex space. We will argue that for conceptual and numeric reason it may be advantageous not to use the steepest descent manifolds (thimbles). We will discuss a variety of algorithms and their application to field theories with a fermionic sign problem and to quantum mechanical models, including real time dynamics.