119398261
Light hadron spectrum and quark masses from quenched lattice QCD
We present the details of simulations for the light hadron spectrum in quenched QCD carried out on the CP-PACS parallel computer. Simulations are made with the Wilson quark action and the plaquette gauge action on lattices of size ${32}^{3}\ifmmode\times\else\texttimes\fi{}56\char21{}{64}^{3}\ifmmode\times\else\texttimes\fi{}112$ at four values of lattice spacings in the range $a\ensuremath{\approx}0.1\char21{}0.05\mathrm{fm}$ and spatial extent ${L}_{s}a\ensuremath{\approx}3\mathrm{fm}.$ Hadronic observables are calculated at five quark masses corresponding to ${m}_{\mathrm{PS}}{/m}_{V}\ensuremath{\approx}0.75\char21{}0.4,$ assuming the u and d quarks are degenerate, but treating the s quark separately. We find that the presence of quenched chiral singularities is supported from an analysis of the pseudoscalar meson data. The physical values of hadron masses are determined using ${m}_{\ensuremath{\pi}},$ ${m}_{\ensuremath{\rho}},$ and ${m}_{K}$ (or ${m}_{\ensuremath{\varphi}})$ as input to fix the physical scale of lattice spacing and the u, d, and s quark masses. After chiral and continuum extrapolations, the agreement of the calculated mass spectrum with experiment is at a 10% level. In comparison with the statistical accuracy of 1%\char21{}3% and systematic errors of at most 1.7% we have achieved, this demonstrates a failure of the quenched approximation for the hadron spectrum: the hyperfine splitting in the meson sector is too small, and in the baryon sector the octet masses and mass splitting of the decuplet are both smaller than experiment. Light quark masses are calculated using two definitions: the conventional one and the one based on the axial-vector Ward identity. The two results converge toward the continuum limit, yielding ${m}_{\mathrm{ud}}{=4.29(14)}_{\ensuremath{-}0.79}^{+0.51}\mathrm{MeV}$ where the first error is statistical and the second one is systematic due to chiral extrapolation. The s quark mass depends on the strange hadron mass chosen for input: ${m}_{s}{=113.8(2.3)}_{\ensuremath{-}2.9}^{+5.8}\mathrm{MeV}$ from ${m}_{K}$ and ${m}_{s}{=142.3(5.8)}_{\ensuremath{-}0}^{+22.0}\mathrm{MeV}$ from ${m}_{\ensuremath{\varphi}},$ indicating again a failure of the quenched approximation. We obtain the scale of QCD, ${\ensuremath{\Lambda}}_{\overline{\mathrm{MS}}}^{(0)}=219.5(5.4)\mathrm{MeV}$ with ${m}_{\ensuremath{\rho}}$ used as input. An $O(10%)$ deviation from experiment is observed in the pseudoscalar meson decay constants.
14619672
Chiral zero modes on the Domain Wall model in (4+1)-dimensions
We investigate an original domain-wall model in 4+1 dimensions numerically in the presence of U(1) dynamical gauge field only in an extra dimension, corresponding to a weak coupling limit of four-dimensional physical gauge coupling. Using a quenched approximation we carry out a numerical simulation for this model at ${\ensuremath{\beta}}_{s}{(=1/g}_{s}^{2})=$ 0.29 (``symmetric'' phase) and 0.5 (``broken'' phase), where ${g}_{s}$ is the gauge coupling constant of the extra dimension. In the broken phase, we found that there exists a critical value of a domain-wall mass ${m}_{0}^{c}$ which separates a region with a fermionic zero mode on the domain wall from the one without it in the same case of (2+1)-dimensional model. On the other hand, in the symmetric phase, our numerical data suggest that the chiral zero modes disappear in the infinite limit of four-dimensional volume. From these results it seems difficult to construct the U(1) lattice chiral gauge theory via an original domain-wall formulation.
26599771
Sea quark effects on quarkonia
We study the effects of two dynamical sea quarks on the spectrum of heavy quarkonia. Within the non-relativistic approach to Lattice QCD we found sizeable changes to the hyperfine splitting, but we could not observe any changes for the fine structure. We also investigated the scaling behaviour of our results for several different lattice spacings.
119024751
Light Hadron Spectroscopy with Two Flavors of Dynamical Quarks on the Lattice
~CP-PACS Collaboration ! Center for Computational Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582, Japan High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan ~Received 18 May 2001; published 5 February 2002 !
5379081
Scaling test of fermion actions in the Schwinger model
Abstract We discuss the scaling behaviour of different fermion actions in dynamical simulations of the 2-dimensional massive Schwinger model. We have chosen Wilson, hypercube, twisted mass and overlap fermion actions. As physical observables, the pion mass and the scalar condensate are computed for the above mentioned actions at a number of coupling values and fermion masses. We also discuss possibilities to simulate overlap fermions dynamically avoiding problems with low-lying eigenvalues of the overlap kernel.
119329204
Lattice Gross-Neveu model with domain-wall fermions
Abstract We investigate the two-dimensional lattice Gross-Neveu model, using the domain-wall fermion formulation, as a toy model of lattice QCD. We study features of the phase diagram related to the mechanism of chiral symmetry restoration, and find that the parity-broken phase (Aoki phase) exists for finite extent in the extra dimension ( N s ). We also find that O ( a ) scaling violation terms vanishes in the limit of N s → ∞.
14502654
Beam test of novel n-in-p strip sensors for high radiation environment
Abstract Highly radiation tolerant n-in-p strip sensors have been developed for the high-luminosity LHC (HL-LHC). This paper reports the results of measurements with 392 MeV kinetic energy proton beam at RCNP in December 2011. The data was taken with a new DAQ system consisting of an universal read-out board ‘SEABAS’ and beam tracking telescopes whose spacial resolution is better than 5 μ m . The aim of this beam test is to evaluate the new 1 cm×1 cm n-in-p miniature sensors before and after 10 15  n eq  cm −2 irradiation. The median charge of un-irradiated sensor is 6.2 fC at full depletion voltage, while the median charge after 10 15  n eq  cm −2 irradiation of the sensor is 4.2 fC. The novel Punch-Through-Protection (PTP) has been implemented in these sensors. The length of active region of the sensor around PTP is observed to be decreased by 12 μ m in the irradiated sensors at 10 15  n eq  cm −2 .