118446008
The QCD Critical Point: Marching towards continuum
Abstract We present results of our simulations of QCD with two light dynamical quarks on a 32 3 × 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.
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.
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.
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.
13571448
Apparent and Actual Shifts in Mass and Width of ϕ Mesons Produced in Heavy-Ion Collisions
We present a method of analyzing invariant-mass spectra of kaon pairs resulting from decay of ϕ mesons produced in high-energy heavy-ion collisions. It can be used to extract the shifts in the mass and the width (ΔM and ΔΓ) of the ϕ mesons when they are inside the dense matter formed in these collisions. We illustrate our method with the help of available preliminary data. Extracted values of ΔM and ΔΓ are significantly larger than those obtained with an earlier method. Our results are consistent with the experimentally observed pT dependence of the mass shift. Finally, we present a phenomenological relation between ΔM and ΔΓ. It provides a useful constraint on theories which predict the values of these two quantities.
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
122156675
Relativistic Hadron Model with Intrinsic Mass Splittings
A simple mechanism for the $\mathrm{SU}(3)$-symmetry breaking in strong interactions is introduced by using the formalism of the multispinor field equations, which avoids the use of physical quarks but has resemblance to the quark model. The resulting treatment leads to the Gell-Mann-Okubo mass formula for baryons, but not for mesons. It yields approximate values of -19.5\ifmmode^\circ\else\textdegree\fi{} and 33\ifmmode^\circ\else\textdegree\fi{} for the $\ensuremath{\eta}\ensuremath{-}{\ensuremath{\eta}}^{\ensuremath{'}}$ and $\ensuremath{\varphi}\ensuremath{-}\ensuremath{\omega}$ mixing angles, respectively, and also provides a reasonable explanation for the intermultiplet meson mass formula $m_{K}^{}{}_{}{}^{2}\ensuremath{-}m_{\ensuremath{\pi}}^{}{}_{}{}^{2}=m_{{K}^{*}}^{}{}_{}{}^{2}\ensuremath{-}m_{\ensuremath{\rho}}^{}{}_{}{}^{2}$.
118402302
Superfield approach to nilpotent symmetries in 3D Jackiw-Pi model of massive non-Abelian theory
In the available literature, only the Becchi-Rouet-Stora-Tyutin (BRST) symmetries are known for the Jackiw-Pi model of the three (2 + 1)-dimensional (3D) massive non-Abelian gauge theory. We derive the off-shell nilpotent (s_{(a)b}^2 = 0) and absolutely anticommuting (s_b \,s_{ab} + s_{ab}\, s_b = 0) (anti-)BRST transformations s_{(a)b} corresponding to the usual Yang-Mills gauge transformations of this model by exploiting the "augmented" superfield formalism where the horizontality condition and gauge invariant restrictions blend together in a meaningful manner. There is a non-Yang-Mills (NYM) symmetry in this theory, too. However, we do not touch the NYM symmetry in our present endeavor. This superfield formalism leads to the derivation of an (anti-)BRST invariant Curci-Ferrari restriction which plays a key role in the proof of absolute anticommutativity of s_{(a)b}. The derivation of the proper anti-BRST symmetry transformations is important from the point of view of geometrical objects called gerbes. A novel feature of our present investigation is the derivation of the (anti-)BRST transformations for the auxiliary field \rho from our superfield formalism which is neither generated by the (anti-)BRST charges nor obtained from the requirements of nilpotency and/or absolute anticommutativity of the (anti-)BRST symmetries for our present 3D non-Abelian 1-form gauge theory.
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