arXiv subjects

Saumen Datta

Publications and source records attributed to Saumen Datta.

At least 37 records · Page 2Linked to original sources

arXiv2012

An estimate of heavy quark momentum diffusion coefficient in gluon plasma

We calculate the momentum diffusion coefficient for heavy quarks in SU(3) gluon plasma at temperatures 1-2 times the deconfinement temperature. The momentum diffusion coefficient is extracted from a Monte Carlo calculation of the correlation function of color electric fields, in the leading order of expansion in heavy quark mass. Systematics of the calculation are examined, and compared with perturbtion theory and other estimates.

hep-lat↗

arXiv2012

The QCD Critical Point : marching towards continuum

We present results of our simulations of QCD with two light dynamical quarks on a 32^3 X 8 lattice at a current quark mass tuned to have the Goldstone pion mass of about 230 MeV. Employing the Taylor expansion method we proposed earlier, we estimate the radius of convergence of the series for the baryonic susceptibility by using terms up to eighth order. Together with our earlier results, corresponding to the same physical parameters but on coarser lattices at respectively 1.33 times and twice the lattice cut-off (a), we were able to attempt a march towards the continuum limit.

hep-lat↗

arXiv2011

Heavy Quark Momentum Diffusion Coefficient from Lattice QCD

The momentum diffusion coefficient for heavy quarks is studied in a deconfined gluon plasma in the static approximation by investigating a correlation function of the color electric field using Monte Carlo techniques. The diffusion coefficient is extracted from the long distance behavior of such a correlator. For temperatures Tc < T <~ 2 Tc, our nonperturbative estimate of the diffusion coefficient is found to be very different from the leading order perturbation theory, and is in the right ballpark to explain the heavy quark flow seen by PHENIX at RHIC.

hep-lat↗

arXiv2010

Continuum Thermodynamics of the SU(N) Gauge Theory

The thermodynamics of the deconfined phase of the SU(N) gauge theory is studied. Careful study is made of the approach to the continuum limit. The latent heat of the deconfinement transition is studied, for the theories with 3, 4 and 6 colors. Continuum estimates of various thermodynamic quantities are studied, and the approach to conformality investigated. The bulk thermodynamic quantities at different N are compared, to investigate the validity of 't Hooft scaling at these values of N.

hep-lat↗

arXiv2010

Scaling and the continuum limit of gluoN_c plasmas

We investigated the finite temperature (T) phase transition for SU(Nc) gauge theory with Nc=4, 6, 8 and 10 at lattice spacing, a, of 1/(6T) or less. We found that these theories have first order transitions at such small a. In many cases we were able to find the critical couplings with precision as good as a few parts in 10^4. We also investigated the use of two-loop renormalization group equations in extrapolating the lattice results to the continuum, thus fixing the temperature scale in units of the phase transition temperature, Tc. We found that when a \le 1/(8Tc) the two-loop extrapolation was accurate to about 1--2%. However, we found that trading Tc for the QCD scale, Lambda_MSbar, increases uncertainties significantly, to the level of about 5--10%.

hep-lat↗

arXiv2010

Continuum Thermodynamics of the GluoN_c Plasma

We study the thermodynamics of SU(N_c) pure gauge theories for N_c=3, 4 and 6. The continuum and thermodynamic limits of bulk quantities such as the pressure, energy density and the entropy density are taken by using several different lattice spacings and volumes. There is no window of temperature in which a non-trivial conformal theory describes bulk thermodynamics. We extract the latent heat of the first-order deconfinement phase transitions and observe good scaling with N_c. For all quantities that we measure, strong N_c scaling holds, except, possibly, very close to the transition temperature, T_c; however we are unable to find strong evidence for scaling with the 't Hooft coupling in thermal quantities at the small values of N_c which we study.

hep-lat↗

arXiv2010

Mesonic Excitations of QGP: Study with an Effective Model

We study the correlations between quark-antiquark pairs in different quantum number channels in a deconfined plasma by using an effective model of QCD. Using the three flavour PNJL model, the finite temperature spectral functions for different mesonic states are studied at zero and nonzero quark chemical potentials. It is found that in the $η$ channel resonance structures survive above the chiral transition temperature $\tc$, while the kaonic states seem to get washed off just above $\tc$. The sensitivity of the structures to the anomaly term are carefully investigated.

nucl-th↗

arXiv2009

Properties of the SU(Nc) Gluon Plasma

We investigate the deconfinement transition in SU(Nc) gauge theories, and properties of the deconfined phase. A detailed lattice study of SU(4) and SU(6) gauge theories are conducted, and finite volume and cutoff effects on thermodynamic observables are studied. The scaling of the deconfinement transition point with lattice spacing is used to calculate the scale, Lambda_MSbar. The continuum estimates of the thermodynamic quantities are used to study properties of the gluon plasma. In particular, the approach to conformal limit is studied. We do not find any evidence of a strongly coupled, conformal phase in these theories.

hep-lat↗

arXiv2009

Exploring the gluoN_c plasma

We report lattice computations in SU(N_c) pure gauge theory, where N_c is increased beyond the physical value of 3. We demonstrate two-loop scaling of T_c, thus obtaining the variation of T_c/Lambda_MSbar with N_c, and fixing the temperature scale. We study the equation of state of the gluoN_c plasma, the conformal anomaly, and the approach to the weak coupling theory. We find that the weak-coupling prediction is always closer to the lattice data than the conformal field theory is.

hep-lat↗

arXiv2008

Thermodynamics and Finite size scaling in Scalar Field Theory

In this work we consider the 1-component real scalar $ϕ^4$ theory in 4 space-time dimensions on the lattice and investigate the finite size scaling of thermodynamic quantities to study whether the thermodynamic limit is attained. The results are obtained for the symmetric phase of the theory.

hep-lat↗

arXiv2008

Zero mode contribution in quarkonium correlators and in-medium properties of heavy quarks

We calculate the low energy contribution to quarkonium correlators in Euclidean time in lattice QCD. This contribution was found to give the dominant source of the temperature dependence of the correlators. We have found that the low energy contribution is well described by a quasi-particle model and have determined the effective temperature dependent heavy quark mass.

hep-lat↗

arXiv2004

Charmonia at finite momenta in a deconfined plasma

Lattice studies of charmonium systems have indicated that in a deconfined gluonic plasma ground state charmonia survive as bound states upto temperatures \~ 2 Tc. After surveying the methodologies used in reaching these results, we examine the behavior of these systems when the bound state is in motion with respect to the heatbath frame. We find that the finite momenta charmonia show medium modifications when the medium is deconfined; in particular, a modification of the energy-momentum dispersion relation is indicated.

hep-lat↗

arXiv2004

Charmonium systems after the deconfinement transition

The behavior of charmonia after the deconfinement transition is investigated on quenched lattices. Analysis of temporal correlators on fine lattices at temperatures upto 3 T_c show that the J/psi and eta_c survive the deconfinement transition with little significant changes, and survive as bound states at least upto 2.25 T_c. The spatially excited chi_c states suffer serious system modifications, maybe dissolution, already a little above T_c.

hep-lat↗

arXiv2003

Behavior of Charmonium Systems after Deconfinement

We present a study of charmonia in hot gluonic plasma, for temperatures upto three times the deconfinement transition temperature Tc. q \bar{q} systems with quark masses close to the charm mass and different spin-parity quantum numbers were studied on very fine isotropic lattices. The analysis of temporal correlators, and spectral functions constructed from them, shows that the J/psi and eta_c survive up to quite high temperatures, with little observable change up to 1.5 Tc, and then gradually weakening and disappearing by 3 Tc. For the scalar and axial vector channels, serious modifications are induced by the hot medium already close to Tc, possibly dissociating the mesons by 1.1 Tc.

hep-lat↗

arXiv2002

A Study of Charmonium Systems across the Deconfinement Transition

We present results from lattice studies of charmonium systems near the deconfinement transition temperature. On quenched isotropic lattices with lattice spacings between 0.02 and 0.05 fm, bar{q} q systems with quark masses close to the charm mass and with different spin-parity quantum numbers are studied in the temperature range 0.9 Tc - 3 Tc. Results for temporal correlators of local operators, and the spectral functions constructed from them, are discussed. For the pseudoscalar and vector channels, the correlators are observed to change very little across the deconfinement transition, unlike in the case of the light quarks.

hep-lat↗

arXiv2002

Does the QCD plasma contain propagating gluons?

Comparison of two appropriately chosen screening masses of colour singlet operators in the pure glue QCD plasma indicates that at sufficiently high temperature it contains a weakly-interacting massive quasi-particle with the quantum numbers of the electric gluon. Still in the deconfined phase, but closer to T_c, the same mass ratio is similar to that at zero temperature, indicating that the propagating modes are more glueball-like, albeit with a lower scale for the masses. We observe a continuity between these two regimes.

hep-lat↗

arXiv2001

The QCD spectrum with three quark flavors

We present results from a lattice hadron spectrum calculation using three flavors of dynamical quarks - two light and one strange, and quenched simulations for comparison. These simulations were done using a one-loop Symanzik improved gauge action and an improved Kogut-Susskind quark action. The lattice spacings, and hence also the physical volumes, were tuned to be the same in all the runs to better expose differences due to flavor number. Lattice spacings were tuned using the static quark potential, so as a byproduct we obtain updated results for the effect of sea quarks on the static quark potential. We find indications that the full QCD meson spectrum is in better agreement with experiment than the quenched spectrum. For the 0++ (a0) meson we see a coupling to two pseudoscalar mesons, or a meson decay on the lattice.

hep-lat↗

arXiv1999

Z2 Monopoles, Vortices, and the Deconfinement Transition in Mixed Action SU(2) Gauge Theory

Adding separate chemical potentials lambda and gamma for Z2 monopoles and vortices respectively in the Villain form of the mixed fundamental-adjoint action for the SU(2) lattice gauge theory, we investigate their role in the interplay between the deconfinement and bulk phase transitions using Monte Carlo techniques. Setting lambda to be nonzero, we find that the line of deconfinement transitions is shifted in the coupling plane but it behaves curiously also like the bulk transition line for large enough adjoint coupling, as for lambda=0. In a narrow range of couplings, however, we find separate deconfinement and bulk phase transitions on the same lattice for nonzero and large lambda, suggesting the two to be indeed coincident in the region where a first order deconfinement phase transition is seen. In the limit of large lambda and gamma, we obtain only lines of second order deconfinement phase transitions, as expected from universality.

hep-lat↗