arXiv subjects
Publications and source records attributed to H. P. Shanahan.
We report on a study of B mesons on N_f = 2 full QCD configurations using an RG-improved gauge action, NRQCD heavy quark action and tadpole-improved clover light quark action. Results on the heavy-light spectrum and the decay constants from 16^3x32 lattices at a^{-1} ~ 1.5 GeV are presented, and compared with quenched results obtained with the same action combination at matching lattice spacings.
We report on recent results for the spectrum of heavy quarkonia. Using coarse and anisotropic lattices we achieved an unprecedented control over statistical and systematic errors for higher excited states such as exotic hybrid states. In a parallel study on isotropic lattices we also investigate the effect of two dynamical flavours on the spin structure of charmonium and bottomonium for several symmetric lattices.
We present results on an analysis of the decay constants fB and fBs with two flavours of sea quark. The calculation has been carried out on 3 different bare gauge couplings and 4 sea quark masses at each gauge coupling, with m_pi/m_rho ranging from 0.8 to 0.6. We employ the Fermilab formalism to perform calculations with heavy quarks whose mass is in the range of the b-quark. A comparison with a quenched calculation using the same action is made to elucidate the effects due to the sea quarks.
We study finite-temperature phase transition and equation of state for two-flavor QCD at $N_t=4$ using an RG-improved gauge action and a meanfield-improved clover quark action. The pressure is computed using the integral method. The O(4) scaling of chiral order parameter is also examined.
We present updated results of the CP-PACS calculation of the light hadron spectrum in $N_{\rm f}=2$ full QCD. Simulations are made with an RG-improved gauge action and a tadpole-improved clover quark action for sea quark masses corresponding to $m_{\rm PS}/m_{\rm V} \approx 0.8$--0.6 and the lattice spacing $a=0.22$--0.09 fm. A comparison of the full QCD spectrum with new quenched results, obtained with the same improved action, shows clearly the existence of sea quark effects in vector meson masses. Results for light quark masses in $N_{\rm f}=2$ QCD are also presented.
We present results on an analysis of the decay constants f_B and f_Bs with two flavours of sea quark. The calculation has been carried out on 3 different bare gauge couplings and 4 sea quark masses at each gauge coupling, with m_pi/m_rho ranging from 0.8 to 0.6. We employ the Fermilab formalism to perform calculations with heavy quarks whose mass is in the range of the b-quark. A detailed comparison with a quenched calculation using the same action is made to elucidate the effects due to the sea quarks.
We investigate the existence of chiral zero modes at a^{-1} \simeq 1 GeV in quenched domain-wall QCD. Simulations are carried out for the plaquette and an RG-improved gauge actions on a 12^3x24xN_s lattice with N_s=10-50. We find that the pion mass in the chiral limit remains non-vanishing as N_s\to\infty for both gauge actions. Possible origins of this non-vanishing pion mass are discussed.
We present results for the mass of the flavor singlet meson calculated on two-flavor full QCD configurations generated by the CP-PACS full QCD project. We also investigate topological charge fluctuations and their dependence on the sea quark mass.
We report on a study of heavy hybrid states using the NRQCD approach on coarse and asymmetric lattices, where we discard vacuum polarisation effects and neglect all spin-correction terms. We find a clear hybrid signal on all our lattices ($a_s= 0.15 ... 0.47$ fm). We have studied in detail the lattice spacing artefacts, finite volume effects and mass dependence. Within the above approximations we predict the hybrid excitation in Charmonium to be 1.323(13) GeV above its ground state. The bottomonium hybrid was found to be 1.542(8) GeV above its ground state.
We present results of a large-scale simulation for the flavor non-singlet light hadron spectrum in quenched lattice QCD with the Wilson quark action. Hadron masses are calculated at four values of lattice spacing in the range $a \approx$ 0.1 - 0.05 fm on lattices with a physical extent of 3 fm at five quark masses corresponding to $m_π/m_ρ\approx 0.75$ - 0.4. The calculated spectrum in the continuum limit shows a systematic deviation from experiment, though the magnitude of deviation is contained within 11%. Results for decay constants and light quark masses are also reported.
We present a calculation of the mass of the 1S0 pseudoscalar anti-b c (Bc) state using a non-perturbative measurement from quenched lattice QCD. We find M_Bc = 6.386(9)(98)(15) GeV where the first error is statistical, the second systematic due to the quark mass ambiguities and quenching and the third the systematic error due to the estimation of mass of the eta_b.
We report results on the static quark potential in two-flavor full QCD. The calculation is performed for three values of lattice spacing $a^{-1}\approx 0.9, 1.3$ and 2.5 GeV on $12^3{\times}24, 16^3{\times}32$ and $24^3{\times}48$ lattices respectively, at sea quark masses corresponding to $m_π/m_ρ\approx 0.8-0.6$. An RG-improved gauge action and a tadpole-improved SW clover quark action are employed. We discuss scaling of $m_ρ/\sqrtσ$ and effects of dynamical quarks on the potential.
We present preliminary results for the Upsilon spectrum on an anisotropic lattice using the improved O(mv^6) NRQCD Hamiltonian. We find accurate results can be obtained in moderate computer times and that they agree with earlier results on an isotropic lattice.
We report the final results of the CP-PACS calculation for the quenched light hadron spectrum with the Wilson quark action. Our data support the presence of quenched chiral singularities, and this motivates us to use mass formulae based on quenched chiral perturbation theory in order to extrapolate hadron masses to the physical point. Hadron masses and decay constants in the continuum limit show unambiguous systematic deviations from experiment. We also report the results for light quark masses.
We report on an on-going two-flavor full QCD study on CP-PACS using an RG-improved gauge action and a tadpole-improved SW quark action. Runs are made for three lattice spacings $a^{-1}\approx 0.9$, 1.3, and 2.5 GeV on $12^3\times24$, $16^3\times32$, and $24^3\times48$ lattices. Four sea quark masses having $m_{\rm PS}/m_{\rm V} \approx 0.8$--0.6 are simulated, for each of which hadron masses are evaluated for valence quark masses corresponding to $m_{\rm PS}/m_{\rm V} \approx 0.8$--0.5. Results for hadron and light quark masses are presented and compared with those obtained in quenched QCD.
The classical transitions between topologically distinct vacua in a SU(2)-Higgs model, using a Higgs field of mass approximately 120 GeV, is examined to probe the crossover region between the symmetric and broken phase. Assuming the Higgs mass is constant, we find the width of this crossover region is approximately 20% of the average temperature. We suggest that this observable is a better parameter to explore this region of phase space than equal-time correlation functions.
We present a quenched lattice calculation for the lowest lying $b \bar b g$-hybrid states in the framework of NRQCD using the leading order Hamiltonian up to ${\cal O}(mv^2)$. We demonstrate the existence of a nearly degenerate rotational band of states with an excitation energy approximately 1.6 GeV above the $Υ$ ground state. This lies around the $B \bar B_J^*$-threshold but well above the $B \bar B$-threshold. Therefore a heavy hybrid signal may well be detected if the centre-of-mass energy in B-factories is raised a few hundred MeV to coincide with other resonances above the 4S state. Our prediction is consistent with most phenomenological models and lattice calculations carried out in the static limit.
We present an analysis of the mass spectrum of heavy quarkonia with non-degenerate quark masses. The heavier (bottom) valence quark is treated in a non-relativistic fashion and the other (charm) is a relativistic Wilson-like quark using the improved SW action. Such states provide and interesting probe between the relativistic B meson states and the non-relativistic bottomonium states.