Browsing by Author "Detmold, William"

Now showing 1 - 6 of 6

Axial Couplings and Strong Decay Widths of Heavy Hadrons
(2012-04-27)
Detmold, William
;
Lin, C-J. David
;
Meinel, Stefan
;
物理研究所
;
Institute of Physics
We calculate the axial couplings of mesons and baryons containing a heavy quark in the static limit using lattice QCD. These couplings determine the leading interactions in heavy hadron chiral perturbation theory and are central quantities in heavy quark physics, as they control strong decay widths and the light quark mass dependence of heavy hadron observables. Our analysis makes use of lattice data at six different pion masses, 227 MeV < m(pi) < 352 MeV, two lattice spacings, a = 0.085, 0.112 fm, and a volume of (2.7 fm)(3). Our results for the axial couplings are g(1) = 0.449(51), g(2) = 0.84(20), and g(3) = 0.71(13), where g(1) governs the interaction between heavy-light mesons and pions and g(2,3) are similar couplings between heavy-light baryons and pions. Using our lattice result for g(3), and constraining 1/m(Q) corrections in the strong decay widths with experimental data for Sigma((*))(c) decays, we obtain Gamma[Sigma((*))(b) -> Lambda(b)pi(+/-)] = 4.2(1.0), 4.8(1.1), 7.3(1.6), 7.8(1.8) MeV for the Sigma(+)(b), Sigma(-)(b), Sigma(b)*(+), Sigma(b)*(-) initial states, respectively. We also derive upper bounds on the widths of the Xi'(()(b)*()) baryons.
Axial couplings in heavy-hadron chiral perturbation theory at the next-to-leading order
(2011-11-09)
Detmold, William
;
Lin, C. -J. David
;
Meinel, Stefan
;
物理研究所
;
Institute of Physics
We present calculations of axial-current matrix elements between various heavy-meson and heavy-baryon states to the next-to-leading order in heavy-hadron chiral perturbation theory in the p-regime. When compared with data from lattice computations or experiments, these results can be used to determine the axial couplings in the chiral Lagrangian. Our calculation is performed in partially quenched chiral perturbation theory for both SU(4 vertical bar 2) and SU(6 vertical bar 3). We incorporate finite-size effects arising from a single Goldstone meson wrapping around the spatial volume. Results for full QCD with two and three flavors can be obtained straightforwardly by taking the sea-quark masses to be equal to the valence-quark masses. To illustrate the impact of our chiral perturbation theory calculation on lattice computations, we analyze the SU(2) full-QCD results in detail. We also study one-loop contributions relevant to the heavy-hadron strong-decay amplitudes involving final-state Goldstone bosons, and demonstrate that the quark-mass dependence of these amplitudes can be significantly different from that of the axial-current matrix elements containing only single-hadron external states.
Bottom hadron mass splittings in the static limit from 2+1 flavour lattice QCD
(2009-09-01)
Detmold, William
;
Lin, C. -J. David
;
Wingate, Matthew
;
物理研究所
;
Institute of Physics
Dynamical 2 + 1 flavour lattice QCD is used to calculate the splittings between the masses of mesons and baryons containing a single static heavy quark and domain-wall light and strange quarks. Our calculations are based on the dynamical domain-wall gauge field configurations generated by the RBC and UKQCD Collaborations at a spatial Volume of (2.7 fm)(3) and a range of quark masses with a lightest value corresponding to a (partially-quenched) pion mass of 275 MeV. When extrapolated to the physical values of the light quark masses, the results Of Our calculations are generally in good agreement with experimental determinations in the bottom sector. However, the static limit splittings between the Omega(-)(b) baryon and other bottom hadrons tend to slightly underestimate those obtained using the recent D empty set measurement of the Omega(-)(b) (C) 2009 Elsevier B.V. All rights reserved.
Calculation of the heavy-hadron axial couplings g(1), g(2), and g(3) using lattice QCD
(2012-06-18)
Detmold, William
;
Lin, C. -J. David
;
Meinel, Stefan
;
物理研究所
;
Institute of Physics
In a recent letter [Phys. Rev. Lett. 108, 172003 (2012)] we have reported on a lattice QCD calculation of the heavy-hadron axial couplings g(1), g(2), and g(3). These quantities are low-energy constants of heavy-hadron chiral perturbation theory (HH chi PT) and are related to the B*B pi, Sigma(b)*Sigma(b)pi, and Sigma(b)(*)Lambda(b)pi couplings. In the following, we discuss important details of the calculation and give further results. To determine the axial couplings, we explicitly match the matrix elements of the axial current in QCD with the corresponding matrix elements in HH chi PT. We construct the ratios of correlation functions used to calculate the matrix elements in lattice QCD, and study the contributions from excited states. We present the complete numerical results and discuss the data analysis in depth. In particular, we demonstrate the convergence of SU(4 vertical bar 2) HH chi PT for the axial-current matrix elements at pion masses up to about 400 MeV and show the impact of the nonanalytic loop contributions. Finally, we present additional predictions for strong and radiative decay widths of charm and bottom baryons.
Lambda(b) -> Lambda l(+)l(-) form factors and differential branching fraction from lattice QCD
(2013-04-05)
Detmold, William
;
Lin, C. -J. David
;
Meinel, Stefan
;
Wingate, Matthew
;
物理研究所
We present the first lattice QCD determination of the Lambda(b) -> Lambda transition form factors that govern the rare baryonic decays Lambda(b) -> Lambda l(+)l(-) at leading order in heavy-quark effective theory. Our calculations are performed with 2 + 1 flavors of domain-wall fermions, at two lattice spacings and with pion masses down to 227 MeV. Three-point functions with a wide range of source-sink separations are used to extract the ground-state contributions. The form factors are extrapolated to the physical values of the light-quark masses and to the continuum limit. We use our results to calculate the differential branching fractions for Lambda(b) -> Lambda l(+)l(-) with l = e, mu, tau within the standard model. We find agreement with a recent CDF measurement of the Lambda(b) -> Lambda mu(+)mu(-) differential branching fraction. DOI: 10.1103/PhysRevD.87.074502
Lambda(b) -> pl(-)(v)over-bar(l) form factors from lattice QCD with static b quarks
(2013-07-23)
Detmold, William
;
Lin, C-J. David
;
Meinel, Stefan
;
Wingate, Matthew
;
物理研究所
We present a lattice QCD calculation of form factors for the decay Lambda(b) -> p mu(-)(v) over bar (mu), which is a promising channel for determining the Cabibbo- Kobayashi-Maskawa matrix element vertical bar V-ub vertical bar at the Large Hadron Collider. In this initial study we work in the limit of static b quarks, where the number of independent form factors reduces to two. We use dynamical domain-wall fermions for the light quarks, and perform the calculation at two different lattice spacings and at multiple values of the light-quark masses in a single large volume. Using our form factor results, we calculate the Lambda(b) -> p mu-(v) over bar (mu) differential decay rate in the range 14 GeV2 <= q(2) <= q(max)(2), and obtain the integral integral(q2max)(14 GeV2) [d Gamma/dq(2)]dq(2)/vertical bar V-ub vertical bar(2) = 15.3 +/- 4.2 ps(-1). Combined with future experimental data, this will give a novel determination of vertical bar V-ub vertical bar with about 15% theoretical uncertainty. The uncertainty is dominated by the use of the static approximation for the b quark, and can be reduced further by performing the lattice calculation with a more sophisticated heavy-quark action.