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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Observation and study of the baryonic B-meson decays B→D (*) pp̄(π)(π)

We present results for B-meson decay modes involving a charm meson, protons, and pions using 455×10⁶ BB¯¯¯ pairs recorded by the BaBar detector at the SLAC PEP-II asymmetric-energy e⁺e⁻ collider. The branching fractions are measured for the following ten decays: B¯¯¯⁰→D⁰pp̄, B¯¯¯⁰→D*⁰pp̄, B¯¯¯⁰→D⁺pp̄π⁻, B¯¯¯⁰→D*⁺pp̄π⁻, B⁻→D⁰pp̄π⁻, B⁻→D*⁰pp̄π⁻, B¯¯¯⁰→D⁰pp̄π⁻π⁺, B¯¯¯⁰→D*⁰pp̄π⁻π⁺, B⁻→D⁺pp̄π⁻π⁻, and B⁻→D*⁺pp̄π⁻π⁻. The four B⁻ and the two five-body B¯¯¯⁰ modes are observed for the first time. The four-body modes are enhanced compared to the three- and the five-body modes. In the three-body modes, the M(pp̄) and M(D(*)⁰p) invariant-mass distributions show enhancements near threshold values. In the four-body mode B¯¯¯⁰→D⁺pp̄π⁻, the M(pπ⁻) distribution shows a narrow structure of unknown origin near 1.5 GeV/c². The distributions for the five-body modes, in contrast to the others, are similar to the expectations from uniform phase-space predictions.

del Amo Sanchez, P.↗
DOE OSTI2012

Search for Bbar to Lambda_c+ X l- nu Decays in Events with a Fully Reconstructed B Meson

We present a search for semileptonic B decays to the charmed baryon {Lambda}{sub c}{sup +} based on 420 fb{sup -1} of data collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II e{sup +}e{sup -} storage rings. By fully reconstructing the recoiling B in a hadronic decay mode, we reduce non-B backgrounds and determine the flavor of the signal B. We statistically correct the flavor for the effect of the B{sup 0} mixing. We obtain a 90% confidence level upper limit of {Beta}({bar B} {yields} {Lambda}{sub c}{sup +} X{ell}{sup -} {bar {nu}}{sub {ell}})/{Beta}({bar B} {yields} {Lambda}{sub c}{sup +} X) < 3.5%.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Observation of Z b ( 10610 ) and Z b ( 10650 ) Decaying to B Mesons

We detail the analysis of the three-body e + e - → B B ¯ π ± , B B ¯ * π ± , and B * B ¯ * π ± processes, including the first observations of the Z b ± ( 10 610 ) → [ B B ¯ * + c . c . ] ± and Z b ± ( 10 650 ) → [ B * B ¯ * ] ± transitions that are found to dominate the corresponding final states. We measure Born cross sections for the three-body production of σ ( e + e - → [ B B ¯ * + c . c . ] ± π ∓ ) = [ 17.4 ± 1.6 ( stat ) ± 1.9 ( syst ) ] pb and σ ( e + e - → [ B * B ¯ * ] ± π ∓ ) = [ 8.75 ± 1.15 ( stat ) ± 1.04 ( syst ) ] pb and set a 90% C.L. upper limit of σ ( e + e - → [ B B ¯ ] ± π ∓ ) < 2.9 pb . The results are based on a 121.4 fb - 1 data sample collected with the Belle detector at a center-of-mass energy near the Υ ( 10 860 ) peak.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the inclusive electron spectrum from B meson decays and determination of | V u b |

Based on the full BABAR data sample of 466.5 million $B\bar{B}$ pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B → X u eν decays from the CKM-favored B → X c eν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B (B → Xeν) = ( 10.34 ± 0.04 stat ± 0.2 6 syst )%, averaged over B ± and B 0 mesons. We determine the spectrum and branching fraction for charmless B → X u eν decays and extract the CKM element | V ub | , by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV / c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |V ub | are presented, with the lower limit on the electron momentum varied from 0.8 GeV / c to the kinematic endpoint. We determine |V ub | using each of these different calculations and find, |V ub | = ( 3.794 ± 0.107 exp $+ 0.292\atop{ - 0.219 SF}$ $+ 0.078 \atop{- 0.068 theory}$ ) × 10 - 3 (De Fazio and Neubert), (4.563 ± 0.126 exp $+ 0.230\atop {- 0.208 SF}$ $+ 0.162\atop{- 0.163 theory}$ ) ×10 -3 (Bosch, Lange, Neubert, and Paz), (3.959 ± 0.104 exp $+ 0.164\atop{- 0.154 SF}$ $+ 0.042\atop{ - 0.079 theory}$ ) × 10 -3 (Gambino, Giordano, Ossola, and Uraltsev), (3.848 ± 0.108 exp $+ 0.084\atop{ - 0.070 theory}$) × 10 -3 (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Light-front holographic distribution amplitudes of pseudoscalar mesons and their application to B -meson decays

In this article the dynamical spin effects of the light-front holographic wave functions for light pseudoscalar mesons are studied. These improved wave functions are then confronted with a number of hadronic observables: the decay constants of π and K mesons, their ξ -moments, the pion-to-photon transition form factor, and the pure annihilation $\bar{B}_s$ → π + π - and $\bar{B}_d$ → K + K - decays. Taking f π , fK , and their ratio fK / f π as constraints, we perform a χ 2 analysis for the holographic parameters, including the mass scale parameter $\sqrtλ$ and the effective quark masses, and find that the fitted results are quite consistent with the ones obtained from the light-quark hadronic Regge trajectories. In addition, we also show that the end point divergence appearing in the pure annihilation $\bar{B}_s$ → π + π - and $\bar{B}_d$ → K + K - decays can be controlled well by using these improved light-front holographic distribution amplitudes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

B -meson decay constants from 2 + 1 -flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

We calculate the B-meson decay constants f B , f B s , and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ≈ 0.11, 0.086 fm with unitary pion masses as light as M π ≈ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavy-light current through O(α s a). We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain f B 0 = 199.5(12.6) MeV, f B + =195.6(14.9) MeV, f B s =235.4(12.2) MeV, f B s /f B 0 =1.197(50), and f B s /f B + =1.223(71), where the errors are statistical and total systematic added in quadrature. Finally, these results are in good agreement with other published results and provide an important independent cross-check of other three-flavor determinations of B-meson decay constants using staggered light quarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Radiative and Leptonic B-meson Decays from the B-factories

Radiative and leptonic decays of B-mesons represent an excellent laboratory for the search for New Physics. I present here recent results on radiative and leptonic decays from the Belle and BABAR collaborations. Radiative penguin and leptonic B-meson decays are excellent probes for investigating the effects of New Physics. Although current measurements are in agreement with the Standard Model expectations, they are still quite useful for setting bounds on possible NP models. The B {yields} X{sub s}{gamma} and B {yields} {tau}{nu} measurements, for example, put strong constraints on the mass of charged Higgs bosons in Type II two-Higgs double models. The B {yields} X{sub s}{gamma} branching fraction measurements also constrain models with universal extra dimensions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Two-loop radiative jet function for exclusive B-meson and Higgs decays

The rare radiative B -meson decay \( {B}^{-}\to \gamma {\mathrm{\ell}}^{-}\overline{v} \) and the radiative Higgs-boson decay h → γγ mediated by light-quark loops both receive large logarithmic corrections in QCD, which can be resummed using factorization theorems derived in soft-collinear effective theory. In these factorization theorems the same radiative jet function appears, which is a central object in the study of factorization beyond the leading order in scale ratios. We calculate this function at two-loop order both in momentum space and in a dual space, where its renormalization-group evolution takes on a simpler form. We also derive the two-loop anomalous dimension of the jet function and present the exact solution to its evolution equation at two-loop order. Another important outcome of our analysis is the explicit form of the two-loop anomalous dimension of the B -meson light-cone distribution amplitude in momentum space.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Semileptonic B Meson Decays

Semileptonic decays of B mesons play a critical role in the determination of the magnitude of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements V cb and V ub . These two quantities are fundamental parameters of the Standard Model and have to be determined experimentally. Over the past decade, the vast samples of B mesons recorded at the B factories at LEP at Cornell University, KEK at Tsukuba, and SLAC at Stanford University have allowed for detailed studies of semileptonic B decays. These decays proceed via first-order weak interactions; thus, they are expected to be free of non–Standard Model contributions and therefore are well suited for the extraction of the quark-mixing parameters. Differential decay rates are combined with theoretical calculations of hadronization effects, leading to a substantially improved knowledge of |V cb | and |V ub |. The results are used to constrain the parameters of the CKM matrix and to test the Standard Model predictions for CP -violating effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗