118999246
Susceptibilities and screening masses in two flavor QCD
We study QCD with two flavors of dynamical staggered quarks at finite temperature, with a bare sea quark mass of about 17 MeV. We report investigations of baryon, isospin, charge and strangeness susceptibilities, as well as screening masses obtained from correlators of local and one-link separated meson operators. These are studied as functions of the valence quark mass at several temperatures. Our results for susceptibilities deviate significantly from ideal gas values, and even more from the weak coupling series. We also report the first measurement of off-diagonal quark number susceptibilities below the transition temperature ${T}_{c},$ where they are the main contribution to charge fluctuations. We present evidence for a close connection between the susceptibilities and the screening masses.
17443615
Lattice QCD for RHIC
I briefly introduce the methods by which lattice QCD predictions for RHIC are obtained. Next I deal with lattice determinations of strangeness production and event-to-event fluctuations of conserved quantities. I also present a new diagrammatic method for computing derivatives with respect to chemical potentials, and conclude with discussions of some tests of thermal perturbation theory which follow.
121387686
Hybrid Monte Carlo simulations of a two-dimensional gauge theory
Through a study of the dynamics of the two-dimensional U(1) pure gauge theory we find exponential slowing down in barrier penetration problems. We verify that the dynamical critical exponent in HMC can be tuned exactly to 1, and that normal and gauge fixed updates have equal cost.
123004962
Flavour degrees of freedom and the transition temperature in QCD
We study the finite temperature transition in QCD with four flavours of dynamical quarks. Our simulation is performed on an 8×16 3 lattice for quarks of mass ma=0.01. At the coupling β c =5.15, we find long-lived metastable states, as well as an abrupt change in the entropy density, suggesting a first order phase transition. Using presently available results from corresponding calculations of the hadron masses and the chiral condensate, this gives us a transition temperature T c ≅100 MeV, which is a factor two lower than the transition temperature found in quenched QCD.
122166973
The phase diagram of QCD: methods and logic of the comparison of experiments and theory
Abstract A small review of the phase diagram of QCD is presented. This is followed by a discussion of the conditions under which experimental data on the fluctuations of conserved quantities in heavy-ion collisions can be treated in the grand canonical ensemble. A robust method for detecting the presence of a nearby critical point in experiments is given. There is a short discussion of the need for non-Gaussian error analysis.
119431013
A precise determination of T_c in QCD from scaling
Existing lattice data on the QCD phase transition are analyzed in renormalized perturbation theory. In quenched QCD it is found that T_c scales for lattices with only 3 time slices, and that T_c/Lambda_msbar=1.15 \pm 0.05. A preliminary estimate in QCD with two flavours of dynamical quarks shows that this ratio depends on the quark mass. For realistic quark masses we estimate T_c/Lambda_msbar=0.49 \pm 0.02. We also investigate the equation of state in quenched QCD at 1-loop order in renormalised perturbation theory.
120756008
Supercooling in viscous hydrodynamics for QCD phase transition
First order quark hadron phase transition is considered in scaling hydrodynamics including the Csernai-Kapusta model of nucleation of hadronic bubbles leading to supercooling. The effect of viscosity on the entropy production is studied in ideal as well as in viscous hydrodynamics with and without supercooling. It is found that the excess entropy produced due to supercooling depends weakly on viscosity.
15301253
R-parity violation in split supersymmetry and neutralino dark matter: to be or not to be
In the recently proposed ‘split supersymmetry’ scenario, the squark and slepton masses are allowed to be at a high scale while the gauginos and Higgsinos are within a TeV. We show that in a theory with broken R-parity, the parameter space of such a scenario allows a situation where the lightest neutralino is still stable on the cosmological scale and can be a dark matter candidate. We also separate the cases where (a) it may be invisible but not a dark matter candidate, or (b) it may decay showing a displaced vertex. It is also emphasized how the constraint on the simultaneous violation of baryon and lepton numbers gets relaxed in this scenario. E-mail: guptask@mri.ernet.in E-mail: konar@mri.ernet.in E-mail: biswarup@mri.ernet.in
123618858
An experimental system for detection of high energy cosmic gamma ray bursts
Abstract While bursts of cosmic gamma rays of energies 0.1–10 MeV can be detected and studied only with satellite-borne detectors, bursts of gamma rays at GeV energies can be detected using sensitive ground-based detectors. An experimental system to detect these high energy gamma ray bursts is being operated at the mountain altitude laboratory at Ootacamund, India. The design features and the experimental details related to this system are described.
124420840
Cosmic Ray Isotope Measurements using the Cherenkov-Rigidity Technique in ISOMAX
The Isotope Magnet Experiment, ISOMAX, which had its first flight in August 1998, is designed to measure the isotopic composition of the light elements using a complement of three major detector systems: a magnetic spectrometer, a time-of-flight (TOF) system, and two Cherenkov detectors. ISOMAX measures mass by combining the velocity measurement with charge and magnetic rigidity (momentum/charge) measurements. In the energy range from 1.1 to 1.7 GeV/nucleon, the velocity measurements are provided by two aerogel Cherenkov counters. The aerogel radiators have a nominal index-of-refraction n = 1.14 corresponding to an energy threshold of 1.08 Ge V /nucleon, which complements and extends the energy range covered by the TOF. Combining the velocity measurement with a measurement of rigidity results in a determination of isotope mass with an expected resolution of ::;: 0.25 amu. We present preliminary isotope data.
199669503
CP Violation in Two Texture Zero Neutrino Mass Matrices
It has been shown that the two texture zero neutrino mass matrices in the charged lepton basis predict non-zero 1-3 mixing and are necessarily CP violating with one possible exception in class C for maximal mixing. There is no CP violation in the leptonic sector of the Standard Model (SM) of fundamental particles and interactions. However, in most extensions of SM, there can be several CP phases. In the simplest three generation scenario, there is a Dirac type CP violating phase in the leptonic mixing matrix. However, for Majorana neutrinos, there could be two additional phases (Majorana phases). It is possible to work in a parameterizations in which all the three CP violating phases are situated in the charged current leptonic mixing matrix. Without any loss of generality, one can work in the flavor basis in which the charged lepton mass matrix is diagonal so that the neutrino mass matrix carries all the information about CP violation. In the flavor basis, the mass matrix for Majorana neutrinos contains nine physical parameters including the three mass eigenvalues, three mixing angles and the three CP-violating phases. The two squared-mass differences (∆m12 and ∆m 2 13) and the two mixing angles (θ12 and θ23) have been measured in solar, atmospheric and reactor experiments. The third mixing angle θ13 and the Dirac-type CP-violating phase δ are expected to be measured in the forthcoming neutrino oscillation experiments. The possible measurement of the effective Majorana mass in neutrinoless double β decay searches will provide an additional constraint on the remaining three neutrino parameters viz. the neutrino mass scale and two Majorana-type CP-violating phases. While the neutrino mass scale will be independently determined by the direct beta decay searches and cosmological observations, the two Majorana phases will not be dev5703@yahoo.com sanjeev3kumar@gmail.com s 7verma@yahoo.co.in shiroberts 1980@yahoo.co.in