E. Gamiz

Publications (28)7.37 Total impact

• Source

  Available from: ArXiv

  Article: Precision $B_c$ and $B_s$ mass calculations

  E. B. Gregory, C. T. H. Davies, K. Y. Wong, E. Follana, E. Gamiz, G. P. Lepage, J. Shigemitsu
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  ABSTRACT: We give improved results for B meson masses using NRQCD $b$ quarks and HISQ light valence quarks for a range of lattice spacings and sea quark masses enabling controlled extrapolation to the physical point. Comment: 6 pages, 3 figures, poster presented at the XXVI International Symposium on Lattice Field Theory, July 14-19, 2008, Williamsburg, Virginia, USA
  10/2008;
• Source

  Available from: ArXiv

  Article: The B -> D* l nu form factor at zero recoil from three-flavor lattice QCD: A model independent determination of |V_cb|

  C. Bernard, C. DeTar, M. Di Pierro, A. X. El-Khadra, R. T. Evans, E. D. Freeland, E. Gamiz, Steven Gottlieb, U. M. Heller, J. E. Hetrick, A. S. Kronfeld, J. Laiho, L. Levkova, P. B. Mackenzie, M. Okamoto, J. Simone, R. Sugar, D. Toussaint, R. S. Van de Water
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  ABSTRACT: We present the first lattice QCD calculation of the form factor for B-> D* l nu with three flavors of sea quarks. We use an improved staggered action for the light valence and sea quarks (the MILC configurations), and the Fermilab action for the heavy quarks. The form factor is computed at zero recoil using a new double ratio method that yields the form factor more directly than the previous Fermilab method. Other improvements over the previous calculation include the use of much lighter light quark masses, and the use of lattice (staggered) chiral perturbation theory in order to control the light quark discretization errors and chiral extrapolation. We obtain for the form factor, F_{B-> D*}(1)=0.921(13)(20), where the first error is statistical and the second is the sum of all systematic errors in quadrature. Applying a 0.7% electromagnetic correction and taking the latest PDG average for F_{B-> D*}(1)|V_cb| leads to |V_cb|=(38.7 +/- 0.9_exp +/- 1.0_theo) x 10^-3.
  09/2008;
• Source

  Available from: arxiv.org

  Article: Unquenched determination of the kaon parameter B_K from improved staggered fermions

  E. Gamiz, S. Collins, C. T. H. Davies, G. P. Lepage, J. Shigemitsu, M. Wingate
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  ABSTRACT: The use of improved staggered actions (HYP, Asqtad) has been proved to reduce the scaling corrections that affected previous calculations of B_K with unimproved (standard) staggered fermions in the quenched approximation. This improved behaviour allows us to perform a reliable calculation of B_K including quark vacuum polarization effects, using the MILC configurations with n_f=2+1 flavours of sea fermions. We perform such a calculation for a single lattice spacing, a=0.125 fm, and with kaons made up of degenerate quarks with m_s/2. The valence strange quark mass m_s is fixed to its physical value and we use two different values of the light sea quark masses. After a chiral extrapolation of the results to the physical value of the sea quark masses, we find \hat B_K = 0.83+-0.18, where the error is dominated by the uncertainty in the lattice to continuum matching at O(\alpha_s^2). The matching will need to be improved to get the precision needed to make full use of the experimental data on \epsilon_K to constrain the unitarity triangle.
  04/2006;
• Source

  Available from: arxiv.org

  Article: Dynamical determination of B_K from improved staggered quarks

  E. Gamiz, S. Collins, C. T. H. Davies, J. Shigemitsu, M. Wingate
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  ABSTRACT: The scaling corrections that affected previous staggered calculations of B_K have been proved to be reduced by using improved actions (HYP, Asqtad) in the quenched approximation. This improved behaviour allows us to perform a reliable dynamical calculation of B_K including quark vacuum polarization effects using the MILC (2+1) flavour dynamical configurations. We report here on the results from such dynamical calculation. We also discuss the renormalization effects with the Asqtad action. Comment: 6 pages, 2 figures. Talk presented at Lattice 2005 (Dublin). To appear in Proceedings of Science
  09/2005;
• Source

  Available from: ArXiv

  Article: B_K from improved staggered quarks

  E. Gamiz, S. Collins, C. T. H. Davies, J. Shigemitsu, M. Wingate
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  ABSTRACT: We compare calculations of B_K with improved staggered quarks (HYP, Asqtad) and demonstrate the improved scaling behaviour that this gives rise to over previous calculations with unimproved staggered quarks. This enables us to perform the calculation of B_K on the MILC dynamical configurations (n_f=2+1), for which we give preliminary results. Comment: 3 pages, 3 figures. Talk presented at Lattice 2004(weak), Fermilab, June 21-26, 2004
  09/2004;
• Source

  Available from: arxiv.org

  Article: Semileptonic B Decays with Nf=2+1 Dynamical Quarks

  J. Shigemitsu, C. T. H. Davies, A. Dougall, K. Foley, E. Gamiz, A. Gray, E. Gulez, G. P. Lepage, M. Wingate
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  ABSTRACT: Semileptonic, B --> pi l,nu, decays are studied on the MILC dynamical configurations using NRQCD heavy and Asqtad light quarks. We work with light valence quark masses ranging between m_s and m_s/8. Preliminary simple linear chiral extrapolations have been carried out for form factors f_para and f_perp at fixed E_pi. The chirally extrapolated results for the form factors f_+(q^2) and f_0(q^2) are then fit to the Becirevic-Kaidalov (BK) ansatz. Preliminary estimates of the CKM matrix element |V_{ub}| are presented based on the recently published branching fractions for B exclusive semileptonic decays by the CLEO collaboration. Comment: 3 pages, 1 figure. Contribution to Lattice'04 (heavy quarks)
  08/2004;
• Article: Neutral B meson mixing in unquenched lattice QCD

  E. Gamiz, CTH Davies, GP Lepage, J. Shigemitsu, M. Wingate
• Article: Semileptonic B Decays with Nf=2+1 Dynamical Quarks

  J. Shigemitsu, C.T.H. Davies, A. Dougall, K. Foley, E. Gamiz, A. Gray, E. Gulez, G.P. Lepage, M. Wintage
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  ABSTRACT: Semileptonic, , decays are studied on the MILC dynamical configuration using NRQCD heavy and Asqtad light quarks. We work with light valence quark masses ranging between ms and ms/8. Preliminary simple linear chiral extrapolations have been carried out for form factors f‖ and f⊥ at fixed Eπ. The chirally extrapolated results for the form factors f+(q2) and f0(q2) are then fit to the Becirevic–Kaidalov (BK) ansatz. Preliminary estimates of the CKM matrix element |Vub| are presented on recently published branching fractions for B0→π−l+ν exclusive decays by the CLEO collaboration.
  Nuclear Physics B - Proceedings Supplements.