[en] We report N* masses in the spin 3/2 sector from a highly-improved anisotropic action. States with both positive and negative parity are isolated via a parity projection method. The extent to which spin projection is needed is examined. The gross features of the splittings from the nucleon ground state show a trend consistent with experimental results at the quark masses explored

[en] We present first results from neutron studies of ns to ps relaxations in bovine collagen, comparing data for a minimally cross-linked sample (young calf) with those for a highly cross-linked one (old cow). Proton displacements derived from quasielastic scans (30< T<300 K) as well as time-of-flight spectra (263< T<310 K) in the 0.2-10 meV region show significant differences

No abstract available

[en] A long standing problem in lattice QCD has been the discrepancy between the experimental and calculated values for the axial charge of the nucleon, g_A≡G_A(Q²=0). Though finite volume effects have been shown to be large, it has also been suggested that excited state effects may also play a significant role in suppressing the value of g_A. In this work, we apply a variational method to generate operators that couple predominantly to the ground state, thus systematically removing excited state contamination from the extraction of g_A. The utility and success of this approach is manifest in the early onset of ground state saturation and the early onset of a clear plateau in the correlation function ratio proportional to g_A. Through a comparison with results obtained via traditional methods, we show how excited state effects can suppress g_A by as much as 8% if sources are not properly tuned or source–sink separations are insufficiently large

[en] The lower limits on the neutrinoless and two neutrino ββ-decay of ¹³⁶Xe, obtained with a multi-element proportional chamber, are reported. The sensitivity of the experiment was limited by the level of the background contamination. The experimental apparatus, its performance and the background analysis are discussed in detail. (orig.)

[en] We present the latest results from the UKQCD/RBC collaborations for the K_l3 form factor from simulations with 2 + 1 flavours of dynamical domain wall quarks. Simulations are performed on lattices with two different volumes and four values of the light quark mass, allowing for an extrapolation to the chiral limit. The analysis includes a thorough investigation into the sources of systematic error in our fits. After interpolating to zero momentum transfer, we obtain f₊(0) = 0.964(5) (or δf = -0.013(5)) which, when combined with the latest experimental results for K_l3 decays, leads to |V_us| = 0.2249(14)

[en] We present the first results for the K_l3 form factor from simulations with 2+1 flavors of dynamical domain wall quarks. Combining our result, namely, f₊(0)=0.964(5) with the latest experimental results for K_l3 decays leads to |V_us|=0.2249(14), reducing the uncertaintity in this important parameter. For the O(p⁶) term in the chiral expansion we obtain Δf=-0.013(5)

[en] We have simulated QCD using 2+1 flavors of domain wall quarks and the Iwasaki gauge action on a (2.74 fm)³ volume with an inverse lattice scale of a^-1=1.729(28) GeV. The up and down (light) quarks are degenerate in our calculations and we have used four values for the ratio of light quark masses to the strange (heavy) quark mass in our simulations: 0.217, 0.350, 0.617, and 0.884. We have measured pseudoscalar meson masses and decay constants, the kaon bag parameter B_K, and vector meson couplings. We have used SU(2) chiral perturbation theory, which assumes only the up and down quark masses are small, and SU(3) chiral perturbation theory to extrapolate to the physical values for the light quark masses. While next-to-leading order formulas from both approaches fit our data for light quarks, we find the higher-order corrections for SU(3) very large, making such fits unreliable. We also find that SU(3) does not fit our data when the quark masses are near the physical strange quark mass. Thus, we rely on SU(2) chiral perturbation theory for accurate results. We use the masses of the Ω baryon, and the π and K mesons to set the lattice scale and determine the quark masses. We then find f_π=124.1(3.6)_stat(6.9)_syst MeV, f_K=149.6(3.6)_stat(6.3)_syst MeV, and f_K/f_π=1.205(0.018)_stat(0.062)_syst. Using nonperturbative renormalization to relate lattice regularized quark masses to regularization independent momentum scheme masses, and perturbation theory to relate these to MS, we find m_ud^MS(2 GeV)=3.72(0.16)_stat(0.33)_ren(0.18)_syst MeV, m_s^MS(2 GeV)=107.3(4.4)_stat(9.7)_ren(4.9)_syst MeV, and m-tilde_ud ratio m-tilde_s=1 ratio 28.8(0.4)_stat(1.6)_syst. For the kaon bag parameter, we find B_K^MS(2 GeV)=0.524(0.010)_stat(0.013)_ren(0.025)_syst. Finally, for the ratios of the couplings of the vector mesons to the vector and tensor currents (f_V and f_V^T, respectively) in the MS scheme at 2 GeV we obtain f_ρ^T/f_ρ=0.687(27); f_K*^T/f_K*=0.712(12), and f_φ^T/f_φ=0.750(8).

[en] We present results for the nucleon axial charge g_A at a fixed lattice spacing of 1/a=1.73(3) GeV using 2+1 flavors of domain wall fermions on size 16³x32 and 24³x64 lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The length of the Monte Carlo trajectory at the lightest m_π is 7360 units, including 900 for thermalization. We find finite volume effects are larger than the pion mass dependence at m_π=330 MeV. We also find a scaling with the single variable m_πL which can also be seen in previous two-flavor domain wall and Wilson fermion calculations. Using this scaling to eliminate the finite-volume effect, we obtain g_A=1.20(6)(4) at the physical pion mass, m_π=135 MeV, where the first and second errors are statistical and systematic. The observed finite-volume scaling also appears in similar quenched simulations, but disappear when V≥(2.4 fm)³. We argue this is a dynamical quark effect

[en] We present physical results obtained from simulations using 2+1 flavors of domain wall quarks and the Iwasaki gauge action at two values of the lattice spacing a, [a^-1=1.73(3) GeV and a^-1=2.28(3) GeV]. On the coarser lattice, with 24³x64x16 points (where the 16 corresponds to L_s, the extent of the 5th dimension inherent in the domain wall fermion formulation of QCD), the analysis of C. Allton et al. (RBC-UKQCD Collaboration), Phys. Rev. D 78 is extended to approximately twice the number of configurations. The ensembles on the finer 32³x64x16 lattice are new. We explain in detail how we use lattice data obtained at several values of the lattice spacing and for a range of quark masses in combined continuum-chiral fits in order to obtain results in the continuum limit and at physical quark masses. We implement this procedure for our data at two lattice spacings and with unitary pion masses in the approximate range 290-420 MeV (225-420 MeV for partially quenched pions). We use the masses of the π and K mesons and the Ω baryon to determine the physical quark masses and the values of the lattice spacing. While our data in the mass ranges above are consistent with the predictions of next-to-leading order SU(2) chiral perturbation theory, they are also consistent with a simple analytic ansatz leading to an inherent uncertainty in how best to perform the chiral extrapolation that we are reluctant to reduce with model-dependent assumptions about higher order corrections. In some cases, particularly for f_π, the pion leptonic decay constant, the uncertainty in the chiral extrapolation dominates the systematic error. Our main results include f_π=124(2)_stat(5)_syst MeV, f_K/f_π=1.204(7)(25) where f_K is the kaon decay constant, m_s^MS(2 GeV)=(96.2±2.7) MeV and m_ud^MS(2 GeV)=(3.59±0.21) MeV (m_s/m_ud=26.8±1.4) where m_s and m_ud are the mass of the strange quark and the average of the up and down quark masses, respectively, [Σ^MS(2 GeV)]^1/3=256(6) MeV, where Σ is the chiral condensate, the Sommer scale r₀=0.487(9) fm and r₁=0.333(9) fm.