Applications of the Stochastic LapH Method
University of California, San Diego, CA 92093, U.S.A.E-mail: rickywong@physics.ucsd.eduProgress in computing the hadron spectrum in lattice QCD using stochastic LapH quark propaga-tors is described. The stochastic LapH algorithm is a particular quark smearing algorithm that alsoallows the computation of all-to-all quark propagators. All-to-all quark propagators are requiredin our approach of using a large set of spatially extended hadron operators and explicit multi-particle operators to access excited states. We report on the progress made in the various isospinchannels on 2+1 dynamical, anisotropic lattices generated by the Hadron Spectrum Collaboration.CERN-PH-TH/2013-010The XXX International Symposium on Lattice Field Theory - Lattice2012June 24 - 29, 2012Cairns,

title: The Yang-Mills gradient flow in finite volume
abstract: A bstractThe Yang-Mills gradient flow is considered on the four dimensional torus T4 for SU(N) gauge theory coupled to Nf flavors of massless fermions in arbitrary representations. The small volume dynamics is dominated by the constant gauge fields. The expectation value of the field strength tensor squared TrFμνFμν (t) is calculated for positive flow time t by treating the non-zero gauge modes perturbatively and the zero modes exactly. The finite volume correction to the infinite volume result is found to contain both algebraic and exponential terms. The leading order result is then used to define a one parameter family of running coupling schemes in which the coupling runs with the linear size of the box. The new scheme is tested numerically in SU(3) gauge theory coupled to Nf = 4 flavors of massless fundamental fermions. The calculations are performed at several lattice spacings with a controlled continuum extrapolation. The continuum result agrees with the perturbative prediction for small renormalized coupling as expected.

title: Group-theoretical construction of finite-momentum and multi-particle operators for lattice hadron spectroscopy
abstract: Determining the spectrum of hadronic excitations from Monte Carlo simulations requires the use of interpolating operators that couple to multi-particle states. Recent algorithmic advances have made the inclusion of multi-hadron operators in spectroscopy calculations a practical reality. In this talk, a procedure for constructing a set of multi-hadron interpolators that project onto the states of interest is described. To aid in the interpretation of simulation data, operators are designed to transform irreducibly under the lattice symmetry group. The identification of a set of optimal single-hadron interpolators for states with non-zero momenta is an essential intermediate step in this analysis.

title: Conformal finite size scaling of twelve fermion flavors
abstract: Extended simulation results and their analysis are reported in a strongly coupled gauge theory with twelve fermion flavors in the fundamental SU(3) color representation. The conformality of the model is probed using mass deformed conformal finite size scaling (FSS) theory driven by the fermion mass anomalous dimension. Two independent conformal FSS fitting procedures are used in the analysis. The first one deploys physics motivated scaling functions, complemented by a second fitting procedure with spline based general B-forms for the scaling functions. The results at fixed gauge coupling show unresolved problems with the conformal hypothesis.

title: The ﬁnite volume spectrum of excited states from lattice QCD simulations
abstract: We present results for the spectrum of excited mesons obtained from temporal correlations of spatially-extended single-hadron and multi-hadron operators computed in lattice QCD. The stochastic LapH algorithm is implemented on anisotropic, dynamical lattices for isovectors for pions of mass 390 MeV. A large correlation matrix with single-particle and two-particle probe operators is diagonalized to identify resonances. The masses of excited states in the I = 1,S = 0,T 1u channel as well as the mixing of single and multi-particle probe operators are presented.

title: A novel algorithm for computing quark propagators for lattice hadron spectroscopy
abstract: We report on our progress in computing the excitation spectrum in Lattice QCD. We focus on the isospin 0, 1 and 2 channels using the stochastic LapH algorithm for the quark propagators. For the isospin-0 channel, a new glueball operator constructed from the stochastic LapH operator is included in the variational basis along with the isoscalar meson and pi-pi operators. A representative signal for each channel is presented and the feasibility of extending the calculations to larger lattices is discussed.

title: Parton Momentum Distribution at the Moment of Jet-Parton Collision
abstract: sNN = 200 GeV. The ridge particles are identified as medium partons kicked by the jet near the surface and they carry direct information on the parton momentum distribution at the moment of jet-parton collisions. The extracted parton momentum distribution has a thermal-like transverse momentum distribution but a rapidity plateau structure with a relatively flat rapidity distribution at mid-rapidities with sharp kinematic boundaries at large rapidities that depend on the transverse momentum.

title: Relativistic Hard-Scattering and Tsallis Fits to p T Spectra in pp Collisions at the LHC ∗
abstract: Motivated by the good Tsallis fits to the high-p T spectra in pp collisions at the LHC, we study the relativistic hard-scattering model and obtain an approximate analytical expression for the differential hard-scattering cross section at � � 0. The power-law behavior of the transverse spectra, in the form of d�/dp 2/1/p n, gives a power index n in the range of 4.5-5.5 for jet production as predicted by pQCD, after the dependencies of the structure functions and the running coupling constant are properly taken into account. The power indices for hadron production n are slightly greater than those for jet production.

title: Signals in Single-Event Pion Interferometry for Granular Sources of Quark-Gluon Plasma Droplets
abstract: We investigate two-pion Bose-Einstein correlations of quark-gluon plasma droplet sources in single-event measurements. We find that the distribution of the fluctuation between correlation functions of the single and mixed events provides useful signals to detect the granular structure of the source.

title: Quarkonia and quark drip lines in a quark-gluon plasma
abstract: We extract the Q-Q potential by using the thermodynamic quantities obtained in lattice gauge calculations. The potential is tested and found to give spontaneous dissociation temperatures that agree well with those from lattice gauge spectral function analysis. Using such a Q-Q potential, we examine the quarkonium states in a quark-gluon plasma and determine the "quark drip lines" which separate the region of bound color-singlet Q Q states from the unbound region. The characteristics of the quark drip lines severely limit the region of possible bound Q Q states with light quarks to temperatures close to the phase transition temperature. Bound quarkonia with light quarks may exist very near the phase transition temperature if their effective quark mass is of the order of 300-400 MeV and higher.

title: Heavy quarkonia and quark drip lines in quark–gluon plasma
abstract: Using the potential model and thermodynamical quantities obtained in lattice gauge calculations, we determine the spontaneous dissociation temperatures of colour-singlet quarkonia and the 'quark drip lines' which separate the region of bound quarkonium states from the unbound region. The dissociation temperatures of J/ψ and Χ b in quenched QCD are found to be 1.62T c and 1.18T c respectively, in good agreement with spectral function analyses. The dissociation temperature of J/ψ in full QCD with two flavours is found to be 1.42T c . For possible bound quarkonium states with light quarks, the characteristics of the quark drip lines severely limit the stable region close to the phase transition temperature. Bound colour-singlet quarkonia with light quarks may exist very near the phase transition temperature if their effective quark mass is of the order of 300-400 MeV.