Light quark masses from quenched lattice QCD simulations with domain wall quarks

Values for the strange quark mass and average up/down mass have been obtained from quenched lattice QCD simulations using the domain wall fermion action. This discretization preserves the properties of flavor and chiral symmetry at nonzero lattice spacing. Results are shown for two values of the lattice spacing. The mass renormalization constant is computed nonperturbatively.Comment: To appear in the proceedings of DPF 2000, Columbus, OH, USA. Work done as part of the RIKEN/BNL/Columbia Collaboration. (3 pages

Thermodynamics of balanced and slightly spin-imbalanced Fermi gases at unitarity

In this paper we present a Monte Carlo calculation of the critical temperature and other thermodynamic quantities for the unitary Fermi gas with a population imbalance (unequal number of fermions in the two spin components). We describe an improved worm type algorithm that is less prone to autocorrelations than the previously available methods and show how this algorithm can be applied to simulate the unitary Fermi gas in presence of a small imbalance. Our data indicates that the critical temperature remains almost constant for small imbalances $h=\Delta\mu/\epsilon_F\lessapprox0.2$. We obtain the continuum result $T_c=0.171(5)\epsilon_F$ in units of Fermi energy and derive a lower bound on the deviation of the critical temperature from the balanced limit, $T_c(h)-T_c(0)>-0.5\epsilon_Fh^2$. Using an additional assumption a tighter lower bound can be obtained. We also calculate the energy per particle and the chemical potential in the balanced and imbalanced cases.Comment: 12 pages, 15 figures; v2: added references, minor corrections, version accepted for publicatio

Light hadronic physics using domain wall fermions in quenched lattice QCD

In the past year domain wall fermion simulations have moved from exploratory stages to the point where systematic effects can be studied with different gauge couplings, volumes, and lengths in the fifth dimension. Results are presented here for the chiral condensate, the light hadron spectrum, and the strange quark mass. We focus especially on the pseudoscalar meson mass and show that, in small volume, the correlators used to compute it can be contaminated to different degrees by topological zero modes. In large volume a nonlinear extrapolation to the chiral limit, e.g. as expected from quenched chiral perturbation theory, is needed in order to have a consistent picture of low energy chiral symmetry breaking effects.Comment: To appear in the proceedings of Lattice 2000 (spectrum), Bangalore, India. Work done as part of the RIKEN/BNL/Columbia Collaboration. (4 pages) - Reference adde

Exploring Lattice Methods for Cold Fermionic Atoms

There has been a surge of experimental effort recently in cooling trapped fermionic atoms to quantum degeneracy. By varying an external magnetic field, interactions between atoms can be made arbitrarily strong. When the S wave scattering length becomes comparable to and larger than the interparticle spacing, standard mean field analysis breaks down. In this case the system exhibits a type of universality, and J-W. Chen and D. B. Kaplan recently showed how this system can be studied from first principles using lattice field theory. This poster presents the first results of exploratory simulations. The existence of a continuum limit is checked and the pairing condensate is studied as a function of the external source strength over a range of temperatures. Preliminary results show simulations can locate the critical temperature.Comment: Poster presented at Lattice2004(non-zero), Fermilab, 21-26 June 2004. 3 page

Lattice QCD calculation of the B(s)→D(s)∗ℓν{{B}_{(s)}\to D_{(s)}^{*}\ell{\nu}} form factors at zero recoil and implications for ∣Vcb∣{|V_{cb}|}

We present results of a lattice QCD calculation of $B\to D^*$ and $B_s\to D_s^*$ axial vector matrix elements with both states at rest. These zero recoil matrix elements provide the normalization necessary to infer a value for the CKM matrix element $|V_{cb}|$ from experimental measurements of $\bar{B}^0\to D^{*+}\ell^-\bar{\nu}$ and $\bar{B}^0_s\to D_s^{*+}\ell^-\bar{\nu}$ decay. Results are derived from correlation functions computed with highly improved staggered quarks (HISQ) for light, strange, and charm quark propagators, and nonrelativistic QCD for the bottom quark propagator. The calculation of correlation functions employs MILC Collaboration ensembles over a range of three lattice spacings. These gauge field configurations include sea quark effects of charm, strange, and equal-mass up and down quarks. We use ensembles with physically light up and down quarks, as well as heavier values. Our main results are $\mathcal{F}^{B\to D^*}(1)= 0.895\pm 0.010_{\mathrm{stat}}\pm{{0.024}_{\mathrm{sys}}}$ and $\mathcal{F}^{B_s\to D_s^*}(1)= 0.883\pm 0.010_{\mathrm{stat}}\pm{0.028_{\mathrm{sys}}}$. We discuss the consequences for $|V_{cb}|$ in light of recent investigations into the extrapolation of experimental data to zero recoil.Comment: 23 pages. v3: Typos corrected. v2: Improved treatment of finite volume effects. Small change to some results (but smaller than the quoted uncertainties). Version accepted for publication in Phys. Rev.