Conveners
Non-zero Temperature: QCD at Non-zero Temperature I
- Harvey B. Meyer (Johannes Gutenberg University Mainz)
Non-zero Temperature: QCD at Non-zero Temperature II
- Owe Philipsen
Non-zero Temperature: QCD at Non-zero Temperature III
- Yasumichi Aoki (RIKEN)
Non-zero Temperature: QCD at Non-zero Temperature IV
- Issaku Kanamori (RIKEN)
Non-zero Temperature: QCD at Non-zero Temperature V
- Sipaz Sharma (Bielefeld University)
Non-zero Temperature: QCD at Non-zero Temperature VI
- Tamas G. Kovacs (Eotvos Lorand University, Budapest)
Recently an approximate SU(4) chiral spin-flavour symmetry was discovered in
multiplet patterns of QCD meson correlation functions, in a temperature range above
the chiral crossover. This symmetry is larger than the full chiral symmetry
of QCD with massless u,d-quarks. It can only arise effectively
when color-electric quark gluon interactions dominate the effective Dirac action
of...
We investigate the phase structure of QCD with three degenerate quark flavors at finite temperature using Mobius domain wall fermions. To locate the critical endpoint and explore the order of phase transition on the diagonal line of the Columbia plot, we performed simulations at temperatures 131 and 196 MeV with lattice spacing $a\sim 0.12$ fm corresponding to temporal lattice extent...
The global center symmetry of quenched QCD at zero baryonic chemical potential is broken spontaneously at a critical temperature $T_c$ leading to a first-order phase transition. Including heavy dynamical quarks breaks the center symmetry explicitly and weakens the first-order phase transition for decreasing quark masses until it turns into a smooth crossover at a $Z_2$-critical point. We...
The so called Columbia Plot summarises the order of the QCD thermal transition as a function of the number of quark flavours and their masses. Recently, it was demonstrated that the first-order chiral transition region, as seen for $N_f=3-6$ on coarse lattices, exhibits tricritical scaling while extrapolating to zero on sufficiently fine lattices. Here we extend these studies to imaginary...
QCD with infinite heavy quark masses exhibits a first-order thermal transition which is driven by the spontaneous breaking of the global $\mathcal{Z}_3$ center symmetry. We analyze the corresponding order parameter, namely the Polyakov loop and its moments, and show, with a rigorous finite size scaling, that in the continuum limit the transition is of first order. We show that the use of a...
The QCD crossover is marked by the rapid change in various observables such as the chiral condensate, the Polyakov loop or the topological susceptibility. We studied the topological properties in pure SU(3) gauge theory where the transition is first order.
Our study focused on the topological susceptibility and the $b_2$ coefficient of the expansion of the free energy density around...
Using the high statistics datasets of the HotQCD Collaboration,
generated with the HISQ (2+1)-flavor action for light and strange quarks,
and treating the charm sector in the quenched approximation, we analyze
the second and fourth order cumulants of charm fluctuations and
the correlations of charm with lighter conserved flavor quantum numbers.
We can make use of a factor 100 larger...
We discuss results about inhomogeneous chiral phases, i.e. phases where in addition to chiral symmetry also translational symmetry is broken, in the $2+1$-dimensional Gross-Neveu model using the mean-field approximation. The phase diagram of the GN model is presented and the existence of inhomogeneous phases is ruled out. The non-existence of inhomogeneous phases will then be shown for a...
The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results about testing the proposal of directly computing the...
We study the Wilson line correlation function in Coulomb gauge on $96^3 \times$ Nt lattices in 2+1 flavor QCD with physical strange quark and light quark masses corresponding to pion mass of 310 MeV, with the aim to determine the complex potential at non-zero temperature. In our calculation we use HISQ action in fixed scale approach with lattice spacing 1/a=7.1 GeV and Nt=56,36,32,28,24,20,...
We study phase structure and critical point of finite-temperature QCD with heavy quarks applying the hopping parameter expansion (HPE). We first study finite-size effects on the critical point on $N_t=4$ lattices with large spatial volumes taking the LO and NLO effects of the HPE, and find that the critical scaling of the Z(2) universality class expected around the critical point of two-flavor...
We present the latest results from the use of the Backus-Gilbert method for reconstructing the spectra of NRQCD bottomonium mesons using anisotropic FASTSUM ensembles at non-zero temperature. We focus in particular on results from the $\eta_b$, $\Upsilon$ and $\chi_{b1}$ generated from Tikhonov-regularized Backus-Gilbert coefficient sets. We extend previous work on the Laplace shifting theorem...
We report preliminary progress in the calculation of the thermal interquark potential of bottomonium using the HAL QCD method with NRQCD quarks. We exploit the fast Fourier transform algorithm, using a momentum space representation, to efficiently calculate NRQCD correlation functions of non-local mesonic S-wave states, and thus obtain the central potential for various temperatures. This work...
The heavy quark diffusion coefficient is encoded in the spectral functions of the chromo-electric and the chromo-magnetic correlators, of which the latter describes the T/M contribution. We study these correlators at two different temperatures T=1.5Tc and T=10⁴Tc in the deconfined phase of SU(3) gauge theory. We use gradient flow for noise reduction. We perform both continuum and zero flow...
We present a novel approach to nonperturbatively estimate the heavy quark momentum diffusion coefficient, which is a key input for the theoretical description of heavy quarkonium production in heavy ion collisions, and is important for the understanding of the elliptic flow and nuclear suppression factor of heavy flavor hadrons. In the heavy quark limit, this coefficient is encoded in the...
We present full QCD correlator data and corresponding reconstructed spectral functions in the pseudoscalar channel. Correlators are obtained using clover-improved Wilson fermions on $N_f=2+1$ HISQ lattices. We use gradient flow to check whether it reduces cut-off and mixed action effects. Valence quark masses are tuned to their physical values by comparing the mass spectrum obtained from the...
The FASTSUM collaboration has developed a comprehensive research programme in thermal QCD using 2+1 flavour, anisotropic ensembles. In this talk, we summarise our recent results including hadron spectrum calculations using our “Generation 2L” ensembles. We will also report on our progress in obtaining anisotropic lattices with a temporal spacing of 17am, half that of our Generation 2L data,...
Singly, doubly and triply charmed baryons are investigated at multiple temperatures using the anisotropic FASTSUM 'Generation 2L' ensemble. We discuss the temperature dependence of these baryons' spectrum in both parity channels with a focus on the confining phase. To further qualify the behaviour of these states around the pseudocritical temperature, the parity doubling due to the restoration...
We present a strategy to study QCD non-perturbatively on the lattice at very high temperatures. This strategy exploits a non-perturbative, finite-volume, definition of the strong coupling constant to renormalize the theory. As a first application we compute the flavour non-singlet meson screening masses in a wide range of temperature, from $T\sim 1 $ GeV up to $\sim 160 $ GeV with three...
It is known that contrary to expectations, the order parameter of chiral
symmetry breaking, the Dirac spectral density at zero virtuality, does not
vanish above the critical temperature of QCD. Instead, the spectral density
develops a pronounced peak at zero. We show that the spectral density in the
peak has large violations of the expected volume scaling. This anomalous
scaling and the...
The interrelation between quantum anomalies and electromagnetic fields leads to a series of non-dissipative transport effects in QCD. In this work we study anomalous transport phenomena with lattice QCD simulations using improved staggered quarks in the presence of a background magnetic field. In particular, we calculate the conductivities both in the free case and in the interacting case,...
The magnetic fields generated in non-central heavy-ion collisions are among the strongest fields produced in the universe, reaching magnitudes comparable to the scale of strong interactions. Backed by model simulations, we expect the resulting field to be spatially modulated, deviating significantly from the commonly considered uniform profile. In this work, we present the next step to improve...
We discuss the QCD phase diagram in the presence of a strong magnetic background field. We provide numerical evidence, based on lattice simulations of QCD with 2+1 flavours and physical quark masses, for a crossover transition at $eB = 4$ GeV$^2$ (with a pseudo-critical temperature $T_c = (98±3)$ MeV) and for a first order phase transition at $eB = 9$ GeV$^2$ (where the measured critical...
The introduction of parallel electric and magnetic fields in the QCD vacuum enhances the weight of topological sectors with a non-zero topological charge. For weak fields, there is a linear response for the topological charge. We study this linear response which can be interpreted as the axion-photon coupling. In this work we use lattice simulations with improved staggered quarks including...
The photon emissivity of the quark-gluon plasma (QGP) is an important input to predict the photon yield in heavy-ion collisions, particularly for transverse momenta in the range of 1 to 2 GeV. Photon production in the QGP can be probed non-perturbatively in lattice QCD via (Euclidean) time-dependent correlators. Analyzing the spatially transverse channel, as well as the difference of the...
Thermal photons from the QGP provide important information about the interaction among the plasma constituents. The photon production rate from a thermally equilibrated plasma is proportional to the transverse spectral function $\rho_T(k_0=|\vec k |,\vec k )$. One can calculate the photon production rate also from the difference between $\rho_T$(transverse) and $\rho_L$(longitudinal)...
We investigate the properties of the pion quasiparticle in the thermal hadronic phase of $(2+1)$-flavor QCD on the lattice at physical quark masses at a temperature $T = 128\,\text{MeV}$. We find that the pion quasiparticle mass $\omega_{\textbf{0}} = 111(3)\,\text{MeV}$ is significantly reduced relative to the zero-temperature pion mass $m_{\pi}(T=0) = 130(1)\,\text{MeV}$, by contrast with...
Investigation of QCD thermodynamics for $N_f=2+1$ along the lines of constant physics with Möbius domain wall fermions is underway. At our coarsest lattice $N_t=12$, reweighting to overlap fermions is not successful. To use domain wall fermions with the residual mass larger than average physical $ud$ quarks, careful treatments of the residual chiral symmetry breaking are necessary. One of the...
We perform finite temperature 2+1-flavor lattice QCD simulation employing
the Möbius domain-wall fermion near the (pseudo-)critical point with Nt=12 and 16. The simulation points are chosen along the lines of constant physics,
where the quark mass is fixed near physical point.
The input quark mass for Möbius domain wall fermion with Ls=12 are tuned
by taking into account the residual...
The relativistic rotation causes a change in QCD critical temperature. Various phenomenological and effective models predict a decrease in the critical temperature in rotating QCD. Nevertheless, it follows from lattice simulations that the critical temperature in gluodynamics increases due to rotation. But in QCD the rotation acts on both gluons and fermions, and combination of these effects...
Polyakov loop effective theories have been shown to successfully describe the thermodynamics of QCD. Furthermore, due to the sign problem, they represent an alternative avenue to investigate the physics at non-zero chemical potential. However, when working with these effective theories, a new set of couplings appear whose expressions in terms of the gauge coupling and $N_{\tau}$ are only known...
For the exploration of the phase diagram of lattice QCD effective Polyakov loop theories provide a valuable tool in the strong coupling and heavy quark mass regime. In practice, the evaluation of these theories is limited by the appearance of long-range and multi-point interaction terms. It is well known that for theories with such kind of interactions mean-field approximations can be expected...
Fluctuations of conserved charges in a grand canonical ensemble
can be computed on the lattice and, thus, provide theoretical
input for freeze-out phenomenology in heavy ion collisions.
Electric charge fluctuations and the corresponding higher order
correlators are extremely difficult, suffering form the most severe
lattice artefacts. We present new simulation data with a...
