skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: B meson semileptonic form factors from unquenched lattice QCD

Abstract

The semileptonic process, B{yields}{pi}l{nu}, is studied via full QCD lattice simulations. We use unquenched gauge configurations generated by the MILC Collaboration. These include the effect of vacuum polarization from three quark flavors: the s quark and two very light flavors (u/d) of variable mass allowing extrapolations to the physical chiral limit. We employ nonrelativistic QCD to simulate the b quark and a highly improved staggered quark action for the light sea and valence quarks. We calculate the form factors f{sub +}(q{sup 2}) and f{sub 0}(q{sup 2}) in the chiral limit for the range 16 GeV{sup 2}{<=}q{sup 2}<q{sub max}{sup 2} and obtain 16 GeV{sup 2}({integral}(q{sub max}{sup 2}))[d{gamma}/dq{sup 2}]dq{sup 2}/V{sub ub}{sup 2}=1.46(35) ps{sup -1}. Combining this with a preliminary average by the Heavy Flavor Averaging Group (HFAG'05) of recent branching fraction data for exclusive B semileptonic decays from the BABAR, Belle and CLEO Collaborations leads to V{sub ub}=4.22(30)(51)x10{sup -3}.

Authors:
; ;  [1];  [2];  [3];  [4]
  1. Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States)
  2. Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550 (United States)
  3. Department of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)
  4. Laboratory of Elementary Particle Physics, Cornell University, Ithaca, New York 14853 (United States)
Publication Date:
OSTI Identifier:
20782821
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevD.73.074502; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; B MESONS; B QUARKS; BRANCHING RATIO; CESR STORAGE RING; CHIRAL SYMMETRY; CHIRALITY; COMPUTERIZED SIMULATION; EXTRAPOLATION; FLAVOR MODEL; FORM FACTORS; LATTICE FIELD THEORY; MULTIPARTICLE SPECTROMETERS; PARTICLE IDENTIFICATION; QUANTUM CHROMODYNAMICS; REST MASS; S QUARKS; SEMILEPTONIC DECAY; VACUUM POLARIZATION; VALENCE

Citation Formats

Gulez, Emel, Gray, Alan, Shigemitsu, Junko, Wingate, Matthew, Davies, Christine T. H., and Lepage, G. Peter. B meson semileptonic form factors from unquenched lattice QCD. United States: N. p., 2006. Web. doi:10.1103/PHYSREVD.73.074502.
Gulez, Emel, Gray, Alan, Shigemitsu, Junko, Wingate, Matthew, Davies, Christine T. H., & Lepage, G. Peter. B meson semileptonic form factors from unquenched lattice QCD. United States. doi:10.1103/PHYSREVD.73.074502.
Gulez, Emel, Gray, Alan, Shigemitsu, Junko, Wingate, Matthew, Davies, Christine T. H., and Lepage, G. Peter. Sat . "B meson semileptonic form factors from unquenched lattice QCD". United States. doi:10.1103/PHYSREVD.73.074502.
@article{osti_20782821,
title = {B meson semileptonic form factors from unquenched lattice QCD},
author = {Gulez, Emel and Gray, Alan and Shigemitsu, Junko and Wingate, Matthew and Davies, Christine T. H. and Lepage, G. Peter},
abstractNote = {The semileptonic process, B{yields}{pi}l{nu}, is studied via full QCD lattice simulations. We use unquenched gauge configurations generated by the MILC Collaboration. These include the effect of vacuum polarization from three quark flavors: the s quark and two very light flavors (u/d) of variable mass allowing extrapolations to the physical chiral limit. We employ nonrelativistic QCD to simulate the b quark and a highly improved staggered quark action for the light sea and valence quarks. We calculate the form factors f{sub +}(q{sup 2}) and f{sub 0}(q{sup 2}) in the chiral limit for the range 16 GeV{sup 2}{<=}q{sup 2}<q{sub max}{sup 2} and obtain 16 GeV{sup 2}({integral}(q{sub max}{sup 2}))[d{gamma}/dq{sup 2}]dq{sup 2}/V{sub ub}{sup 2}=1.46(35) ps{sup -1}. Combining this with a preliminary average by the Heavy Flavor Averaging Group (HFAG'05) of recent branching fraction data for exclusive B semileptonic decays from the BABAR, Belle and CLEO Collaborations leads to V{sub ub}=4.22(30)(51)x10{sup -3}.},
doi = {10.1103/PHYSREVD.73.074502},
journal = {Physical Review. D, Particles Fields},
number = 7,
volume = 73,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}
  • No abstract prepared.
  • We study the exclusive semileptonic B-meson decays B→K(π)ℓ +-, B→K(π)νν¯, and B→πτν, computing observables in the Standard model using the recent lattice-QCD results for the underlying form factors from the Fermilab Lattice and MILC Collaborations. These processes provide theoretically clean windows into physics beyond the Standard Model because the hadronic uncertainties are now under good control. The resulting partially-integrated branching fractions for B→πμ +μ - and B→Kμ +μ - outside the charmonium resonance region are 1-2σ higher than the LHCb Collaboration's recent measurements, where the theoretical and experimental errors are commensurate. The combined tension is 1.7σ. Combining the Standard-Modelmore » rates with LHCb's measurements yields values for the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |V td|=7.45(69)×10 -3, |V ts|=35.7(1.5)×10 -3, and |V td/V ts|=0.201(20), which are compatible with the values obtained from neutral B (s)-meson oscillations and have competitive uncertainties. Alternatively, taking the CKM matrix elements from unitarity, we constrain new-physics contributions at the electroweak scale. Furthermore, the constraints on the Wilson coefficients Re(C 9) and Re(C 10) from B→πμ +μ - and B→Kμ +μ - are competitive with those from B→K*μ +μ -, and display a 2.0σ tension with the Standard Model. Our predictions for B→K(π)νν¯ and B→πτν are close to the current experimental limits.« less
  • Cited by 24
  • We compute themore » $$B\to\pi\ell\nu$$ semileptonic form factors and update the determination of the CKM matrix element $$|V_{ub}|$$. We use the MILC asqtad ensembles with $$N_f=2+1$$ sea quarks at four different lattice spacings in the range $$a \approx 0.045$$~fm to $0.12$~fm. The lattice form factors are extrapolated to the continuum limit using SU(2) staggered chiral perturbation theory in the hard pion limit, followed by an extrapolation in $q^2$ to the full kinematic range using a functional $z$-parameterization. The extrapolation is combined with the experimental measurements of the partial branching fraction to extract $$|V_{ub}|$$. Our preliminary result is $$|V_{ub}|=(3.72\pm 0.14)\times 10^{-3}$$, where the error reflects both the lattice and experimental uncertainties, which are now on par with each other.« less