116031505
Impact of stout-link smearing in lattice fermion actions
The impact of stout-link smearing in lattice fermion actions is examined through the consideration of the mass and renormalization functions of the overlap quark propagator over a variety of smeared configurations. Up to six sweeps of stout-link sme aring are investigated. For heavy quark masses, the quark propagator is strongly affected by the smearing procedure. For moderate masses, the effect appears to be negligible. A small effect i s seen for light quark masses, where dynamical mass generation is suppressed through the smearing procedure.
119461087
Scalar Mesons a0(1450) and sigma(600) from Lattice QCD
We study the a0 and sigma mesons with the overlap fermion in the chiral regime with the pion mass as low as 182 MeV in the quenched approximation. After the eta'pi ghost states are separated, we find that the a0 mass with q\bar{q} interpolation field to be almost independent of the quark mass in the region below the strange quark mass. The chirally extrapolated results are consistent with a0(1450) being the u\bar{d} meson and K0*(1430) being the u\bar{s} meson with calculated masses at 1.42+_0.13 GeV and 1.41+_ 0.12 GeV respectively. We also calculate the scalar mesonium with a tetraquark interpolation field. In addition to the two pion scattering states, we find a state at around 550 MeV. Through the study of volume dependence, we confirm that this state is a one-particle state, in contrast to the two-pion scattering states. This suggests that the observed state is a tetraquark mesonium which is quite possibly the sigma(600) meson.
118309222
Locality and Scaling of Quenched Overlap Fermions
The overlap fermion offers the tremendous advantage of exact chiral symmetry on the lattice, but is numerically intensive. This can be made affordable while still providing large lattice volumes, by using coarse lattice spacing, given that good scaling and localization properties are established. Here, using overlap fermions on quenched Iwasaki gauge configurations, we demonstrate directly that the overlap Dirac operator's range is comfortably small in lattice units for each of the lattice spacings 0.20 fm, 0.17 fm, and 0.13 fm (and scales to zero in physical units in the continuum limit). In particular, our direct results contradict recent speculation that an inverse lattice spacing of 1 GeV is too low to have satisfactory localization. Furthermore, hadronic masses (available on the two coarser lattices) scale very well.
119433952
Scaling behavior of the overlap quark propagator in the Landau gauge
The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations are done on three lattices with different lattice spacings and similar physical volumes to explore the approach of the quark propagator toward the continuum limit. We have calculated the nonperturbative momentum-dependent wave-function renormalization function $Z({\ensuremath{\zeta}}^{2};p)$ and the nonperturbative mass function $M(p)$ for a variety of bare quark masses and perform an extrapolation to the chiral limit. We find the behavior of $Z({\ensuremath{\zeta}}^{2};p)$ and $M(p)$ are in reasonable agreement between the two finer lattices in the chiral limit, however the data suggest that an even finer lattice is desirable. The large momentum behavior is examined to determine the quark condensate.
858386
Chiral symmetry, quark mass, and scaling of the overlap fermions
The chiral symmetry relation and scaling of the overlap fermions are studied numerically on the quenched lattices at 3 couplings with about the same physical volume. We find that the generalized Gell-Mann-Oakes-Renner relation is satisfied to better than 1% down to the smallest quark mass at m(0)a = 0.006. We also obtain the quark mass from the PCAC relation and the pseudoscalar masses. The renormalization group invariant quark mass is shown to be fairly independent of scale. The pi and rho masses at a fixed m(pi)/m(rho) ratio indicate small O(a(2)) corrections. It is found that the critical slowing down sets in abruptly at a very small quark mass close to those of the physical u and d quarks.
17425362
FLIC overlap fermions
Abstract The action of the overlap-Dirac operator on a vector is typically implemented indirectly through a multi-shift conjugate gradient solver. The compute-time required depends upon the condition number, κ, of the matrix that is used as the overlap kernel. While the Wilson action is typically used as the overlap kernel, the FLIC (Fat Link Irrelevant Clover) action has an improved condition number and provides up to a factor of two speedup in evaluating the overlap action. We summarize recent progress on the use of FLIC overlap fermions.
119194335
One-loop matching for parton distributions: Nonsinglet case
We derive the one-loop matching condition for nonsinglet quark distributions in the transverse-momentum cutoff scheme, including unpolarized, helicity and transversity distributions. The matching is between the quasidistribution defined by static correlation at finite nucleon momentum and the light-cone distribution measurable in experiments. The result is useful for extracting the latter from the former in a lattice QCD calculation which uses the lattice spacing as the ultraviolet cutoff.
41278561
The silicon matrix for the prototype for the Dark Matter Particle Explorer
In this paper, a silicon matrix detector is described and the results of the cosmic ray test are given. The silicon matrix is composed by the 180 silicon PIN detectors, which covers an area of 32 * 20cm2. The data of whole detectors is read out by the ASIC chips, and suppressed by an FPGA. In the test system, the trigger is given by two plastic scintillators, which are placed above and beneath the silicon matrix. The MIPs energy spectrum is shown in this paper. In further test, a small plastic scintillator is inserted to give a differential cosmic ray counting response.
118608841
Preheating in bubble collisions
In a landscape with metastable minima, the bubbles will inevitably nucleate. We show that when the bubbles collide, due to the dramatic oscillation of the field at the collision region, the energy deposited in the bubble walls can be efficiently released by the explosive production of the particles. In this sense, the collision of bubbles is actually highly inelastic. The cosmological implications of this result are discussed.
118375588
Heavy flavor baryon spectra via QCD sum rules
In this talk, we give a short review of our recent works on studying the singly heavy baryon, doubly heavy baryon, and triply heavy baryon spectra from QCD sum rules.
119213612
Deciphering triply heavy baryons in terms of QCD sum rules
Abstract The mass spectra of ground-state triply heavy baryons are systematically unscrambled and computed in QCD sum rules. With a tentative ( QQ ) – ( Q ′ ) configuration for QQQ ′ , the interpolating currents representing the triply heavy baryons are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion (OPE). The numerical results are presented in comparison with other theoretical predictions.