arXiv subjects

H. -T. Ding

Publications and source records attributed to H. -T. Ding.

47 records · Page 3Linked to original sources

arXiv2012

Charmonium properties in hot quenched lattice QCD

We study the properties of charmonium states at finite temperature in quenched QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above $T_c$. Our analysis suggests that both S wave states ($J/ψ$ and $η_c$) and P wave states ($χ_{c0}$ and $χ_{c1}$) disappear already at about $1.5 T_c$. The charm diffusion coefficient is estimated through the Kubo formula and found to be compatible with zero below $T_c$ and approximately $1/πT$ at $1.5 T_c\lesssim T\lesssim 3 T_c$.

hep-lat↗

arXiv2012

The chiral transition and U(1)_A symmetry restoration from lattice QCD using Domain Wall Fermions

We present results on both the restoration of the spontaneously broken chiral symmetry and the effective restoration of the anomalously broken U(1)_A symmetry in finite temperature QCD at zero chemical potential using lattice QCD. We employ domain wall fermions on lattices with fixed temporal extent N_τ= 8 and spatial extent N_σ= 16 in a temperature range of T = 139 - 195 MeV, corresponding to lattice spacings of a \approx 0.12 - 0.18 fm. In these calculations, we include two degenerate light quarks and a strange quark at fixed pion mass m_π= 200 MeV. The strange quark mass is set near its physical value. We also present results from a second set of finite temperature gauge configurations at the same volume and temporal extent with slightly heavier pion mass. To study chiral symmetry restoration, we calculate the chiral condensate, the disconnected chiral susceptibility, and susceptibilities in several meson channels of different quantum numbers. To study U(1)_A restoration, we calculate spatial correlators in the scalar and pseudo-scalar channels, as well as the corresponding susceptibilities. Furthermore, we also show results for the eigenvalue spectrum of the Dirac operator as a function of temperature, which can be connected to both U(1)_A and chiral symmetry restoration via Banks-Casher relations.

hep-lat↗

arXiv2012

The chiral and deconfinement aspects of the QCD transition

We present results on the chiral and deconfinement properties of the QCD transition at finite temperature. Calculations are performed with 2+1 flavors of quarks using the p4, asqtad and HISQ/tree actions. Lattices with temporal extent N_tau=6, 8 and 12 are used to understand and control discretization errors and to reliably extrapolate estimates obtained at finite lattice spacings to the continuum limit. The chiral transition temperature is defined in terms of the phase transition in a theory with two massless flavors and analyzed using O(N) scaling fits to the chiral condensate and susceptibility. We find consistent estimates from the HISQ/tree and asqtad actions and our main result is T_c=154 +/- 9 MeV.

hep-lat↗

arXiv2011

Exploring phase diagram of $N_f=3$ QCD at $μ=0$ with HISQ fermions

We studied the QCD phase transition as a function of quark mass in the $N_f=3$ QCD at vanishing baryon density. Lattice simulations have been performed using Highly Improved Staggered Quarks on $N_τ=6$ lattices with quark masses that correspond to pion masses in the region $80 \lesssim m_π \lesssim 230 $MeV. We found no evidence of the first order phase transition in the current pion mass window. The pion mass at the critical point where the first order phase transition starts is estimated to be $m^c_π\lesssim 45$ MeV.

hep-lat↗

arXiv2011

Heavy Quark diffusion from lattice QCD spectral functions

We analyze the low frequency part of charmonium spectral functions on large lattices close to the continuum limit in the temperature region $1.5\lesssim T/T_c\lesssim 3$ as well as for $T \simeq 0.75T_c$. We present evidence for the existence of a transport peak above $T_c$ and its absence below $T_c$. The heavy quark diffusion constant is then estimated using the Kubo formula. As part of the calculation we also determine the temperature dependence of the signature for the charmonium bound state in the spectral function and discuss the fate of charmonium states in the hot medium.

nucl-th↗

arXiv2011

Thermal dilepton rate and electrical conductivity: An analysis of vector current correlation functions in quenched lattice QCD

We calculate the vector current correlation function for light valence quarks in the deconfined phase of QCD. The calculations have been performed in quenched lattice QCD at T=1.45 Tc for four values of the lattice cut-off on lattices up to size 128^3x48. This allows to perform a continuum extrapolation of the correlation function in the Euclidean time interval tau*T -in [0.2, 0.5], which extends to the largest temporal separations possible at finite temperature, to better than 1% accuracy. In this interval, at the value of the temperature investigated, we find that the vector correlation function never deviates from the free correlator for massless quarks by more than 9%. We also determine the first two non-vanishing thermal moments of the vector meson spectral function. The second thermal moment deviates by less than 7% from the free value. With these constraints, we then proceed to extract information on the spectral representation of the vector correlator and discuss resulting consequences for the electrical conductivity and the thermal dilepton rate in the plasma phase.

hep-lat↗

arXiv2010

Charmonium correlation and spectral functions at finite temperature

We study the properties of charmonium states at finite temperature in quenched QCD on isotropic lattices. We measured charmonium correlators using non-perturbatively $\cO(a)$ improved clover fermions on fine ($a=0.01$ fm) lattices with a relatively large size of $128^{3}\times 96$, $128^3\times48$, $128^3\times32$ and $128^3\times24$ at $0.73~T_c$, $1.46~T_c$, $2.20~T_c$ and $2.93~T_c$, respectively. Our analysis suggests that $\Jpsi$ is melted already at $1.46~T_c$ and $η_c$ starts to dissolve at $1.46~T_c$ and does not exist at higher temperatures. We also identify the heavy quark transport contribution at the spectral function level for the first time.

hep-lat↗

arXiv2009

Charmonium correlators and spectral functions at finite temperature

We study charmonium correlators and spectral functions in quenched QCD, using Clover improved Wilson fermions on very fine (0.015 fm) isotropic lattices at 0.75 Tc and 1.5 Tc. We use a new approach to distinguish the zero mode contribution from the other contributions. Once this is removed, we find that the ratios of correlators to reconstructed correlators remain almost unity at all distances. The ground state peaks of spectral functions obtained at 0.75 Tc are reliable and robust. The present accuracy and limited number of points in the temporal direction at 1.5 Tc do not allow for a reliable conclusion about a possible melting of charmonium states in the QGP.

hep-lat↗

arXiv2009

Charmonium correlators and spectral functions at finite temperature

We present an operational approach to address the in-medium behavior of charmonium and analyze the reliability of maximum entropy method (MEM). We study the dependences of the ratio of correlators to the reconstructed one and the free one on the resonance's width and the continuum's threshold. Furthermore, we discuss the issue of the default model dependence of the spectral function obtained from MEM.

hep-lat↗

arXiv2008

Effect of heavy-quark energy loss on the muon differential production cross section in Pb-Pb collisions at \sqrtsNN=5.5 TeV

We study the nuclear modification factors RAA and RCP of the high transverse momentum 5<pt<60 GeV/c distribution of muons in Pb--Pb collisions at LHC energies. We consider two pseudo-rapidity ranges covered by the LHC experiments: $|η|<2.5$ and $2.5<η<4$. Muons from semi-leptonic decays of heavy quarks (c and b) and from leptonic decays of weak gauge bosons (W and Z) are the main contributions to the muon pt distribution above a few GeV/c. We compute the heavy quark contributions using available pQCD-based programs. We include the nuclear shadowing modification of the parton distribution functions and the in-medium radiative energy loss for heavy quarks, using the mass-dependent BDMPS quenching weights. Muons from W and Z leptonic decays, that dominate the yield at high pt, can be used as a medium-blind reference to observe the medium-induced suppression of beauty quarks.

hep-ph↗

arXiv2007

Studying the energy loss of heavy quarks via single muon production in PbPb collisions at $\sqrt{s_\mathrm{NN}}$=5.5 TeV

The effects of heavy quarks energy loss on the transverse momentum spectra of single muons are studied. The energy loss of heavy quarks when traversing the medium formed in PbPb collisions at $\sqrt{s_\mathrm{NN}}$=5.5 TeV is calculated by implementing the collision geometry and the quenching weights. The medium density is assumed to decrease at forward pseudo-rapidity and to be proportional with pseudo-rapidity multiplicity $dN/dη$. Muons from W decays can be used as a medium-blind reference to quantify the effect of heavy quarks energy loss on the single muon production.

hep-ph↗