More Like this

1. Spin-dependent interactions and heavy-quark transport in the quark-gluon plasma

   https://doi.org/10.1103/PhysRevC.108.044906  

   Tang, Zhanduo; Rapp, Ralf (October 2023, Physical Review C)

   We extend a previously constructed T -matrix approach to the quark-gluon plasma (QGP) to include the effects of spin-dependent interactions between partons. Following earlier work within the relativistic quark model, the spin-dependent interactions figure as relativistic corrections to the Cornell potential. When applied to the vacuum spectroscopy of quarkonia, in particular their mass splittings in S- and P-wave states, the issue of the Lorentz structure of the confining potential arises. We confirm that a significant admixture of a vector interaction (to the previously assumed scalar interaction) improves the description of the experimental mass splittings. The temperature corrections to the in-medium potential are constrained by results from thermal lattice quantum chromodynamics for the equation of state and heavy-quark free energy in a self-consistent setup for heavyand light-parton spectral functions in the QGP. We then deploy the refined in-medium heavy-light T matrix to compute the charm-quark transport coefficients in the QGP. The vector component of the confining potential, through its relativistic corrections, enhances the friction coefficient for charm quarks in the QGP over previous calculations by tens of percentages at low momenta and temperatures and more at higher momenta. Our results are promising for improving the current phenomenology of open heavy-flavor observables at Relativistic Heavy Ion Collider and the Large Hadron Collider. 

   more » « less
2. Nonperturbative effects on radiative energy loss of heavy quarks

   https://doi.org/10.1007/JHEP08(2020)168  

   Liu, Shuai Y.F.; Rapp, Ralf (August 2020, Journal of High Energy Physics)

   null (Ed.)

   A bstract The radiative energy loss of fast partons traveling through the quark-gluon plasma (QGP) is commonly studied within perturbative QCD (pQCD). Nonperturbative (NP) effects, which are expected to become important near the critical temperature, have been much less investigated. Here, we utilize a recently developed T -matrix approach to incorporate NP effects for gluon emission off heavy quarks propagating through the QGP. We set up four cases that contain, starting from a Born diagram calculation with color- Coulomb interaction, an increasing level of NP components, by subsequently including (remnants of ) confining interactions, resummation in the heavy-light scattering amplitude, and off-shell spectral functions for both heavy and light partons. For each case we compute the power spectra of the emitted gluons, heavy-quark transport coefficients (drag and transverse-momentum broadening, $$ \hat{q} $$ q ̂ ), and the path-length dependent energy loss within a “QGP brick” at fixed temperature. Investigating the differences in these quantities between the four cases illustrates how NP mechanisms affect gluon radiation processes. While the baseline perturbative processes experience a strong suppression of soft radiation due to thermal masses of the emitted gluons, confining interactions, ladder resummations and broad spectral functions (re-)generate a large enhancement toward low momenta and low temperatures. For example, for a 10 GeV charm quark at 200 MeV temperature, they enhance the transport coefficients by up to a factor of 10, while the results smoothly converge to perturbative results at sufficiently hard scales. 

   more » « less
3. Hydrodynamic description of D meson production in high-energy heavy-ion collisions *

   https://doi.org/10.1088/1674-1137/abf645  

   Ding, Chi; Ke, Wei-Yao; Pang, Long-Gang; Wang, Xin-Nian (July 2021, Chinese Physics C)

   Abstract The large values and constituent-quark-number scaling of the elliptic flow of low- D mesons imply that charm quarks, initially produced through hard processes, might be partially thermalized through strong interactions with quark-gluon plasma (QGP) in high-energy heavy-ion collisions. To quantify the degree of thermalization of low- charm quarks, we compare the meson spectra and elliptic flow from a hydrodynamic model to experimental data as well as transport model simulations. We use an effective charm chemical potential at the freeze-out temperature to account for the initial charm quark production from hard processes and assume that they are thermalized in the local comoving frame of the medium before freeze-out. mesons are sampled statistically from the freeze-out hyper-surface of the expanding QGP as described by the event-by-event (3+1)D viscous hydrodynamic model CLVisc. Both the hydrodynamic and transport models can describe the elliptic flow of mesons at GeV/ c as measured in Au+Au collisions at GeV. Though the experimental data on spectra are consistent with the hydrodynamic result at small GeV/ c , they deviate from the hydrodynamic model at high transverse momentum, GeV/ c . The diffusion and parton energy loss mechanisms in the transport model can describe the measured spectra reasonably well within the theoretical uncertainty. Our comparative study indicates that charm quarks only approach local thermal equilibrium at small , even though they acquire sizable elliptic flow comparable to light-quark hadrons at both small and intermediate . 

   more » « less
4. Analysis of static Wilson line correlators from lattice QCD at finite temperature with T -matrix approach

   https://doi.org/10.1051/epjconf/202429609015  

   Tang, Zhanduo; Mukherjee, Swagato; Petreczky, Peter; Rapp, Ralf (January 2024, EPJ Web of Conferences)

   Bellwied, R; Geurts, F; Rapp, R; Ratti, C; Timmins, A; Vitev, I (Ed.)

   The thermodynamicT-matrix approach is used to study Wilson line correlators (WLCs) for a static quark-antiquark pair in the quark-gluon plasma (QGP). Selfconsistent results that incorporate constraints from the QGP equation of state can approximately reproduce WLCs computed in 2+1-flavor lattice-QCD (lQCD), provided the input potential exhibits less screening than in previous studies. Utilizing the updated potential to calculate pertinent heavylightT-matrices we evaluate thermal relaxation rates of heavy quarks in the QGP. We find a more pronounced temperature dependence for low-momentum quarks than in our previous results (with larger screening), which turns into a weaker temperature dependence of the (temperature-scaled) spatial diffusion coefficient, in fair agreement with the most recent lQCD data. 

   more » « less
5. B- and D-meson leptonic decay constants and quark masses from four-flavor lattice QCD

   TUMQCD and Fermilab Lattice and MILC Collaborations: Bazavov, A.; Bernard, C; Brambilla, N.; Brown, N.; DeTar, C.; El Khadra, A.X.; Gámiz, E.; Gottlieb, S.; Heller, U.M.; Komijani, J.; et al (January 2019, 13th Conference on the Intersections of Particle and Nuclear Physics)

   We describe a recent lattice-QCD calculation of the leptonic decay con- stants of heavy-light pseudoscalar mesons containing charm and bottom quarks and of the masses of the up, down, strange, charm, and bottom quarks. Results for these quantities are of the highest precision to date. Calculations use 24 isospin-symmetric ensembles of gauge-field configura- tions with six different lattice spacings as small as approximately 0.03 fm and several values of the light quark masses down to physical values of the average up- and down-sea-quark masses. We use the highly-improved staggered quark (HISQ) formulation for valence and sea quarks, includ- ing the bottom quark. The analysis employs heavy-quark effective theory (HQET). A novel HQET method is used in the determination of the quark masses. 

   more » « less