The melting and abundance of open charm hadrons

Bazavov, A. (Department of Physics and Astronomy, University of Iowa, Iowa City, IA, 52240, USA) ; Ding, H.-T. (Key Laboratory of Quark & Lepton Physics (MOE), Institute of Particle Physics, Central China Normal University, Wuhan, 430079, China) ; Hegde, P. (Key Laboratory of Quark & Lepton Physics (MOE), Institute of Particle Physics, Central China Normal University, Wuhan, 430079, China) ; Kaczmarek, O. (Fakultät für Physik, Universität Bielefeld, Bielefeld, D-33615, Germany) ; Karsch, F. (Fakultät für Physik, Universität Bielefeld, Bielefeld, D-33615, Germany) (Physics Department, Brookhaven National Laboratory, Upton, NY, 11973, USA) ; Laermann, E. (Fakultät für Physik, Universität Bielefeld, Bielefeld, D-33615, Germany) ; Maezawa, Y. (Fakultät für Physik, Universität Bielefeld, Bielefeld, D-33615, Germany) ; Mukherjee, Swagato (Physics Department, Brookhaven National Laboratory, Upton, NY, 11973, USA) ; Ohno, H. (Physics Department, Brookhaven National Laboratory, Upton, NY, 11973, USA) (Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577, Japan) ; Petreczky, P. (Physics Department, Brookhaven National Laboratory, Upton, NY, 11973, USA) ; Schmidt, C. (Fakultät für Physik, Universität Bielefeld, Bielefeld, D-33615, Germany) ; Sharma, S. (Fakultät für Physik, Universität Bielefeld, Bielefeld, D-33615, Germany) ; Soeldner, W. (Institut für Theoretische Physik, Universität Regensburg, Regensburg, D-93040, Germany) ; Wagner, M. (Physics Department, Indiana University, Bloomington, IN, 47405, USA)

19 August 2014

Abstract: Ratios of cumulants of conserved net charge fluctuations are sensitive to the degrees of freedom that are carriers of the corresponding quantum numbers in different phases of strong interaction matter. Using lattice QCD with 2+1 dynamical flavors and quenched charm quarks we calculate second and fourth order cumulants of net charm fluctuations and their correlations with other conserved charges such as net baryon number, electric charge and strangeness. Analyzing appropriate ratios of these cumulants we probe the nature of charmed degrees of freedom in the vicinity of the QCD chiral crossover region. We show that for temperatures above the chiral crossover transition temperature, charmed degrees of freedom can no longer be described by an uncorrelated gas of hadrons. This suggests that the dissociation of open charm hadrons and the emergence of deconfined charm states sets in just near the chiral crossover transition. Till the crossover region we compare these lattice QCD results with two hadron resonance gas models—including only the experimentally established charmed resonances and also including additional states predicted by quark model and lattice QCD calculations. This comparison provides evidence for so far unobserved charmed hadrons that contribute to the thermodynamics in the crossover region.


Published in: Physics letters B 737 (2014) 210-215
Published by: Elsevier
DOI: 10.1016/j.physletb.2014.08.034
License: CC-BY-3.0



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