Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session EE: Mini-Symposium on Precision Lattice Gauge Theory II |
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Chair: Kostas Orginos, College of William and Mary Room: Kohala 2 |
Friday, October 16, 2009 9:00AM - 9:30AM |
EE.00001: Equation of State and the finite temperature transition in hot QCD Invited Speaker: This talk will summarize the results obtained by the HotQCD collaboration on the equation of state and the crossover transition in 2+1 flavor QCD. We will present results on bulk thermodynamic quantities - energy density, pressure, entropy density, and the speed of sound over the temperature range $140 < T < 540$ MeV. These results have been obtained on lattices of temporal size $N_\tau = 6$ and $8$ and with two improved staggered fermion actions, asqtad and p4. Our most extensive results are with masses of the two degenerate light quarks set at $m_{ud} = 0.1 m_s$ corresponding to the lightest pion mass $m_\pi$ between $220-260 MeV$. In these simulations, the strange quark mass is tuned to its physical value and defines lines of constant physics. We will also summarize the current state of results on observables sensitive to the chiral and deconfining physics - the light and strange quark number susceptibilities, the chiral condensate and its susceptibility, and the renormalized Polyakov loop. Our results indicate that the deconfinement and chiral symmetry restoration occur in the same narrow temperature interval. [Preview Abstract] |
Friday, October 16, 2009 9:30AM - 9:45AM |
EE.00002: pi-pi, K-pi and K-K interactions from lattice QCD Andre Walker-Loud I will discuss recent lattice calculations of the I=2 pi-pi, I=3/2 K-pi and I=1 K-K scattering processes from the NPLQCD Collaboration. Combined with chiral perturbation theory, these hadron interaction processes can be used to make precise determinations of the corresponding scattering lengths and the Gasser-Leutwyler coefficients which contribute to these interactions. [Preview Abstract] |
Friday, October 16, 2009 9:45AM - 10:00AM |
EE.00003: S-wave $\pi-K$ scattering length from lattice QCD Kiyoshi Sasaki, Naruhito Ishizuka, Takeshi Yamazaki, Makoto Oka We present the S-wave $\pi-K$ scattering lengths for both the isospin 1/2 and 3/2 channels evaluated by using the finite size formula. We utilize the $N_f=2+1$ gauge configurations generated on $32^3 \times 64$ lattice using the Iwasaki gauge action and the $O(a)$-improved Wilson action at $1/a = 2.17$ GeV. The quark masses correspond to $m_\pi$ = 0.30 - 0.70 GeV. For $I=1/2$, to separate the effects from excited states, we construct a $2\times 2$ matrix of the time correlation function and diagonalize it. Here, we adopt the two kinds of operators, $\bar{s}u$ and $\pi-K$. Our preliminary results show signs of the scattering lengths in agreement with experiment, namely attraction in $I=1/2$ and repulsion in $I=3/2$. We investigate the quark-mass dependence of the scattering length and also discuss the limitation of chiral perturbation theory. [Preview Abstract] |
Friday, October 16, 2009 10:00AM - 10:15AM |
EE.00004: Extracting the energies of multi-hadron states in lattice QCD Justin Foley The ability to reliably measure the energy of an excited hadron in lattice QCD simulations hinges on the accurate determination of all lower-lying energies in the same symmetry channel. These include not only single-particle energies, but the energies of multi-hadron states. The same multi-hadron energies measured at a number of lattice volumes may also be used to determine hadron scattering lengths. In this talk, we discuss the determination of multi-hadron energies in lattice QCD. The group-theoretical derivation of lattice interpolating operators which couple optimally to multi-hadron states is described. We briefly outline recent algorithmic developments which allow for the efficient implementation of these operators in software, and present numerical results from the Hadron Spectrum Collaboration. [Preview Abstract] |
Friday, October 16, 2009 10:15AM - 10:30AM |
EE.00005: Charmed-Meson Scattering in lattice QCD Takuya Yagi, Munehisa Ohtani, Osamu Morimatsu, Shoji Hashimoto The interaction of $D_{1}$ and $D*$ mesons is studied in lattice QCD aiming at obtaining some hint on the nature of the $Z$(4430). Our calculation is done using the Wilson fermion on a quenched $24^3\times 48$ lattice. We calculate the correlation functions of $D_{1}$ and $D*$ mesons and obtain the energy in a finite box, from which we extract the scattering length of $D_{1}$ and $D*$ mesons by means of L\"uscher's formula. [Preview Abstract] |
Friday, October 16, 2009 10:30AM - 10:45AM |
EE.00006: The effective gluon mass and the gluon propagator form in the Landau gauge in SU(3) lattice QCD Takumi Iritani, Hideo Suganuma, Hideaki Iida We study the gluon propagator in the Landau gauge in SU(3) lattice QCD with $\beta = 5.7, 5.8$ and $6.0$ at the quenched level in the region of $r = 0.1 \sim 1.0$ fm, which is relevant to quark-hadron physics. First, we evaluate the effective gluon mass in lattice QCD, since gluons have been conjectured to acquire large effective mass due to non-perturbative effects of QCD. The effective gluon mass is estimated to be about $400 \sim 600$ MeV in the Landau gauge in an infrared region of $r = 0.5 \sim 1.0$ fm. Next, we investigate the functional form of the gluon propagator in the Landau gauge. As a remarkable fact, the gluon propagator is found to be well reproduced by the simple Yukawa-type function $e^{-mr}/r$ in the whole region of $r = 0.1 \sim 1.0$ fm in the four-dimensional Euclidean space-time. Note that this Yukawa-type propagator in four-dimensional space-time corresponds to a new-type propagator of $(p^2+m^2)^{-3/2}$ in the momentum space. Based on the Yukawa-type gluon propagator obtained from lattice QCD, we also discuss a possible construction of the infrared effective theory such as a Nambu-Jona-Lasinio-type theory from QCD. [Preview Abstract] |
Friday, October 16, 2009 10:45AM - 11:00AM |
EE.00007: Relevant energy scale of color confinement from lattice QCD Arata Yamamoto, Hideo Suganuma We propose a new lattice framework to extract the relevant gluonic energy scale of QCD phenomena which is based on a ``cut'' on link variables in momentum space. This framework is expected to be broadly applicable to all lattice QCD calculations. Using this framework, we quantitatively determine the relevant energy scale of color confinement, through an analysis of the quark-antiquark potential. The relevant energy scale of color confinement is found to be below 1.5 GeV in the Landau gauge. In addition, we analyze meson masses and the flux-tube distribution by this framework. [Preview Abstract] |
Friday, October 16, 2009 11:00AM - 11:15AM |
EE.00008: ABSTRACT WITHDRAWN |
Friday, October 16, 2009 11:15AM - 11:30AM |
EE.00009: Proper Heavy-Quark Potential in a Spectral Decomposition from the Thermal Wilson Loop Alexander Rothkopf, Tetsuo Hatsuda, Shoichi Sasaki Experimental findings of $Q\bar{Q}$ suppression urge for a better understanding of the underlying in-medium effects. To this end we propose a non-perturbative definition of the proper Heavy-Quark potential V(R) from the spectral decomposition of the thermal Wilson loop:${\cal{W}}(\tau,R) \propto_{m\to\infty} \int e^{-\bar{\omega}\tau}\rho(\bar{\omega},R)d\bar{\omega}.$ Re[V(R)] can be extracted using peak positions in $\rho(\bar{\omega},R)$ at different R, and the imaginary part from the width of the envelope. The use of spectral functions allows to connect imaginary- and real-time quantities such as the forward propagator $D^>(t,R)$: $ \int d\bar{\omega} e^{-i\bar{\omega} t} \rho(\bar{\omega},R) d\bar{\omega} =D^>(t,R) {\sim}_{t\to\infty} e^{-itV(R)}.$ This bridges the gap between rigorous results at T=0 and perturbative studies well above the critical temperature. The peak structure of the spectral function also determines when a Schr\"odinger-equation description of the system is possible, in which this proper potential can be used. First results for the real part in SU(3) gauge theory, using a 3-peak model for the spectral function, reveal that well above the critical temperature the string tension of the heavy $Q\bar{Q}$ system still contributes significantly. Thus, Debye screening is not as pronounced as in the case of the Polyakov loop correlator free energies. These hints toward an increased stability of heavy quarkonia up to $2T_C$ as compared to melting within a free energy potential framework are consistent with both experimental data and lattice studies on the $Q\bar{Q}$ spectrum and its wavefunction. [Preview Abstract] |
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