Search results for "Heavy quark effective theory"
showing 10 items of 24 documents
Measurement of the ratio ofBc+branching fractions toJ/ψπ+andJ/ψμ+νμfinal states
2014
The first measurement that relates semileptonic and hadronic decay rates of the B-c(+) meson is performed using proton-proton collision data corresponding to 1.0 fb(-1) of integrated luminosity collected with the LHCb detector. The measured value of the ratio of branching fractions, B(B-c(+) -> J/psi pi(+))/B(B-c(+) -> J/psi mu(+)nu(mu)) = 0.0469 +/- 0.0028(stat) +/- 0.0046(syst), is at the lower end of available theoretical predictions.
Density distributions in the $B$ meson
2016
We report on a two-flavor lattice QCD study of the axial, charge and matter distributions of the $B$ meson and its first radial excitation. As our framework is the static limit of Heavy Quark Effective Theory (HQET), taking their Fourier transform gives access to several form factors at the kinematical point $q^2=0$. Moreover they provide some useful information on the nature of an excited state, i.e. a radial excitation of a quark-antiquark bound state or a multihadron state.
Nonperturbative effects in semileptonicBcdecays
2001
We discuss the impact of the soft degrees of freedom inside the B_c meson on its rate in the semi-leptonic decay B_c -> X l nu_l where X denotes light hadrons below the D^0 threshold. In particular we identify contributions involving soft hadrons which are non-vanishing in the limit of massless leptons. These contributions become relevant for a measurement of the purely leptonic B_c decay rate, which due to helicity suppression involves a factor m_l^2 and thus is much smaller than the contributions involving soft hadrons.
Masses and decay constants of D(s)* and B(s)* mesons with Nf=2+1+1 twisted mass fermions
2017
We present a lattice calculation of the masses and decay constants of ${D}_{(s)}^{*}$ and ${B}_{(s)}^{*}$ mesons using the gauge configurations produced by the European Twisted Mass Collaboration (ETMC) with ${N}_{f}=2+1+1$ dynamical quarks at three values of the lattice spacing $a\ensuremath{\sim}(0.06\ensuremath{-}0.09)\text{ }\text{ }\mathrm{fm}$. Pion masses are simulated in the range ${M}_{\ensuremath{\pi}}\ensuremath{\simeq}(210--450)\text{ }\text{ }\mathrm{MeV}$, while the strange and charm sea-quark masses are close to their physical values. We compute the ratios of vector to pseudoscalar masses and decay constants for various values of the heavy-quark mass ${m}_{h}$ in the range $0…
Measurement of theΛb0lifetime in the exclusive decayΛb0→J/ψΛ0inpp¯collisions ats=1.96 TeV
2012
We measure the Lambda_b^0 lifetime in the fully reconstructed decay Lambda_b^0 -> J/psi Lambda^0 using 10.4 fb^-1 of ppbar collisions collected with the D0 detector at sqrt(s)=1.96 TeV. The lifetime of the topologically similar decay channel B^0 -> J/psi K^0_S is also measured. We obtain tau(Lambda_b^0) = 1.303 +- 0.075 (stat.) +- 0.035 (syst.) ps and tau(B^0) = 1.508 +- 0.025 (stat.) +- 0.043 (syst.) ps. Using these measurements, we determine the lifetime ratio of tau(Lambda_b^0)/tau(B^0) = 0.864 +- 0.052 (stat.) +- 0.033 (syst.).
Hidden charm molecules in finite volume
2013
In the present paper we address the interaction of pairs of charmed mesons with hidden charm in a finite box. We use the interaction from a recent model based on heavy-quark spin symmetry that predicts molecules of hidden charm in the infinite volume. The energy levels in the box are generated within this model, and from them some synthetic data are generated. These data are then employed to study the inverse problem of getting the energies of the bound states and phase shifts for D (D) over bar or D*(D) over bar*. Different strategies are investigated using the lowest two levels for different values of the box size, and the errors produced are studied. Starting from the upper level, fits t…
Axial resonances in the open and hidden charm sectors
2007
13 pages, 2 figures.-- PACS nrs.: 11.10.St, 11.80.Gw, 12.39.Hg, 12.39.Fe.-- ISI Article Identifier: 000249271600001.-- ArXiv pre-print available at: http://arxiv.org/abs/0704.2314
Polarization effects in exclusive semi-leptonic Λc and Λb charm and bottom baryon decays
1992
Abstract We discuss polarization effects in semi-leptonic decays of polarized and unpolarized heavy Λ-type baryons into heavy and into light Λ-type baryons. We use the non-leptonic decay of the daughter baryon and the leptonic decay of the Woff-shell into a lepton pair as polarization analyzers to analyze the polarization of the daughter baryon and the Woff-shell. Technically this is done by writing down joint angular decay distributions. We calculate the values of the various asymmetry parameters that characterize the angular dependence of the angular decay distributions where we use the predictions of the heavy quark effective theory (HQET) supplemented by simple ansatze for the q2-depend…
Measurement of theΛb0Lifetime inΛb0→Λc+π−Decays inpp¯Collisions ats=1.96 TeV
2007
We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions. This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foundation; the A.P. Sloan Foundation; the Bundesministerium fur Bildung und Forschung, Germany; the World Class University Program, the National Research Foundation of Korea; the Science and Technology Facilities Co…
Quenched and first unquenched lattice HQET determination of the B-s-meson width difference
2001
We present recent results for the prediction of the Bs lifetime difference from lattice Heavy Quark Effective Theory simulations. In order to get a next-to-leading order result we have calculated the matching between QCD and HQET and the two-loop anomalous dimensions in the HQET for all the \Delta B=2 operators, in particular for the operators which enter the width difference. We present results from quenched and, for the first time, from unquenched simulations. We obtain for the Bs lifetime difference, (\Delta\Gamma_Bs/\Gamma_Bs)^{(que.)}=(5.1+/- 1.9+/- 1.7)10^(-2) and (\Delta\Gamma_Bs/\Gamma_Bs)^{(unq.)}=(4.3+/- 2.0+/- 1.9)10^(-2) from the quenched and unquenched simulations respectively