122158553
Physics across the phase diagram of QCD
In this talk I present some lattice computations which constrain finite size effects in fireballs resulting from heavy-ion collisions. The results show that early stages of evolution are not constrained by spatial size, whereas freezeout is. The second conclusion is compatible with results of the analysis of fluctuations of conserved quantities, which is a finite-size scaling 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.
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.
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.
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.
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.
17387019
Inhomogeneous nucleation in a quark-hadron phase transition
The effect of subcritical hadron bubbles on a first-order quark-hadron phase transition is studied. These subcritical hadron bubbles are created due to thermal fluctuations, and can introduce a finite amount of phase mixing (quark phase mixed with hadron phase) even at and above the critical temperature. For reasonable choices of surface tension and correlation length, as obtained from the lattice QCD calculations, we show that the amount of phase mixing at the critical temperature remains below the percolation threshold. Thus, as the system cools below the critical temperature, the transition proceeds through the nucleation of critical-size hadron bubbles from a metastable quark-gluon phase (QGP), within an inhomogeneous background populated by an equilibrium distribution of subcritical hadron bubbles. The inhomogeneity of the medium results in a substantial reduction of the nucleation barrier for critical bubbles. Using the corrected nucleation barrier, we estimate the amount of supercooling for different parameters controlling the phase transition, and briefly discuss its implications to cosmology and heavy-ion collisions.
16048302
On free 4D Abelian 2-form and anomalous 2D Abelian 1-form gauge theories
We demonstrate a few striking similarities and some glaring differences between (i) the free four- (3+1)-dimensional (4D) Abelian 2-form gauge theory, and (ii) the anomalous two- (1+1)-dimensional (2D) Abelian 1-form gauge theory, within the framework of Becchi–Rouet–Stora–Tyutin (BRST) formalism. We demonstrate that the Lagrangian densities of the above two theories transform in a similar fashion under a set of symmetry transformations even though they are endowed with a drastically different variety of constraint structures. With the help of our understanding of the 4D Abelian 2-form gauge theory, we prove that the gauge-invariant version of the anomalous 2D Abelian 1-form gauge theory is a new field-theoretic model for the Hodge theory where all the de Rham cohomological operators of differential geometry find their physical realizations in the language of proper symmetry transformations. The corresponding conserved charges obey an algebra that is reminiscent of the algebra of the cohomological operators. We briefly comment on the consistency of the 2D anomalous 1-form gauge theory in the language of restrictions on the harmonic state of the (anti-) BRST and (anti-) co-BRST invariant version of the above 2D theory.
54964643
Studies on Cosmic Ray Sidereal Anisotropy with the Multidirectional Muon Telescope at Ooty
We have developed a multidirectional telescope capable of recording individual muons with angular accuracy of about 5 degrees. This muon telescope consists of ∼ 3000 proportional counters with total area of ∼ 420 m with threshold energy > 1 GeV. The telescope is a component of the GRAPES-3 experiment at Ooty in southern India (N 11.4, E 76.7 and 2200m altitude). The very large muon counting rate ∼ 1.8×108 per hour, achieved due to the very large area of the telescope, gives us great advantage for cosmic ray modulation studies. The analysis of data with such high statistics enables us to have a sensitive measurement of sidereal variation within a single year of observation. Further, since our telescope is located near the Equator, we are able to observe both the Northern and the Southern hemispheres simultaneously. We present here the results on the sidereal variation obtained with this multidirectional muon telescope for the observational period, 2000–2001. We report here on Tail-in and Loss-corn anisotropies through detailed analysis. We also discuss other possible explanations for the present observations.
121535698
Intermittency analysis of fragmenting nuclei with exact conservation laws
We show that the speculative charge bin size dependence of the scaled factorial moments for fragmenting nuclei in recent nuclear emulsion data may be attributed in part to simple conservation laws. Monte Carlo results from both the Thermodynamic Model and an Evaporation Model suggest that in such studies most or all of the effect is due to the fact that there exist constraints owing to conserved quantities.
54200433
Status of the CUTE-FEL Project
We are building a Compact Ultrafast Terahertz FreeElectron Laser (CUTE-FEL) designed to lase at around 80 μm. Here we report on the present status. A 2 μs, 40 keV beam from a DC thermionic electron gun has been accelerated up to 4.5 MeV using a 21 cm long, 4-cell, Plane Wave Transformer (PWT) linac. Current measurements using a Fast Current Transformer (FCT) after a bending magnet energy spectrometer show a peak current of about 10 mA at 4.5 MeV. This beam was transported through a 1.25 m long undulator section. We have also built and tested the 476 MHz pre-buncher for the linac, and are in the midst of assembling the final FEL beamline.