89 research outputs found

    Spin Content of Lambda in QCD Sum Rules

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    We calculate the isoscalar axial-vector coupling constants of the Lambda hyperon using the method of QCD sum rules. A determination of these coupling constants reveals the individual contributions of the u, d and the s quarks to the spin content of Lambda. Our results for the light-quark contributions are in agreement with those from experiment assuming flavor SU(3). We also find that the flavor-SU(3)-breaking effects are small and the contributions from the u and the d quarks to the Lambda polarization are negatively polarized as in the flavor-SU(3) limit.Comment: 6 pages, 2 figure

    QCD Sum Rules study of meson-baryon sigma terms

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    The pion-baryon sigma terms and the strange-quark condensates of the octet and the decuplet baryons are calculated by employing the method of quantum chromodynamics (QCD) sum rules. We evaluate the vacuum-to-vacuum transition matrix elements of two baryon interpolating fields in an external isoscalar-scalar field and use a Monte Carlo-based approach to systematically analyze the sum rules and the uncertainties in the results. We extract the ratios of the sigma terms, which have rather high accuracy and minimal dependence on QCD parameters. We discuss the sources of uncertainties and comment on possible strangeness content of the nucleon and the Delta.Comment: 17 pages, 10 figures, to be published in Phys. Rev.

    Axial Charges of Octet Baryons in Two-flavor Lattice QCD

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    We evaluate the strangeness-conserving NNN N, ΣΣ\Sigma\Sigma, ΞΞ\Xi\Xi, ΛΣ\Lambda\Sigma and the strangeness-changing ΛN\Lambda N, ΣN\Sigma N, ΛΞ\Lambda\Xi, ΣΞ\Sigma\Xi axial charges in lattice QCD with two flavors of dynamical quarks and extend our previous work on pseudoscalar-meson-octet-baryon coupling constants so as to include πΞΞ\pi\Xi\Xi, KΛΞK\Lambda\Xi and KΣΞK\Sigma\Xi coupling constants. We find that the axial charges have rather weak quark-mass dependence and the breaking in SU(3)-flavor symmetry is small at each quark-mass point we consider.Comment: 6 pages, 6 figures. Added discussions and a figure; version to appear in Physics Letters

    Study of FCNC mediated rare B_s decays in a single universal extra dimension scenario

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    We study the rare semileptonic and radiative leptonic B_s decays in the universal extra dimension model. In this scenario, with a single extra dimension, there exists only one new parameter beyond those of the standard model, which is the inverse of the compactification radius R. We find that with the additional contributions due to the KK modes the branching ratios of the rare B_s decays are enhanced from their corresponding standard model values and the zero point of the forward backward asymmetries are shifted towards the left.Comment: 19 pages, 7 figures, version to appear in Phys. Rev.

    Axial Charges of Octet Baryons in Two-flavor Lattice QCD

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    We evaluate the strangeness-conserving NNN N, ΣΣ\Sigma\Sigma, ΞΞ\Xi\Xi, ΛΣ\Lambda\Sigma and the strangeness-changing ΛN\Lambda N, ΣN\Sigma N, ΛΞ\Lambda\Xi, ΣΞ\Sigma\Xi axial charges in lattice QCD with two flavors of dynamical quarks and extend our previous work on pseudoscalar-meson-octet-baryon coupling constants so as to include πΞΞ\pi\Xi\Xi, KΛΞK\Lambda\Xi and KΣΞK\Sigma\Xi coupling constants. We find that the axial charges have rather weak quark-mass dependence and the breaking in SU(3)-flavor symmetry is small at each quark-mass point we consider.Comment: 6 pages, 6 figures. Added discussions and a figure; version to appear in Physics Letters

    Ωcγ→Ωc∗\Omega_c \gamma \rightarrow\Omega_c^\ast transition in lattice QCD

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    We study the electromagnetic Ωcγ→Ωc∗\Omega_c \gamma \rightarrow\Omega_c^\ast transition in 2+1 flavor lattice QCD, which gives access to the dominant decay mode of Ωc∗\Omega_c^\ast baryon. The magnetic dipole and the electric quadrupole transition form factors are computed. The magnetic dipole form factor is found to be mainly determined by the strange quark and the electric quadrupole form factor to be negligibly small, in consistency with the quark model. We also evaluate the helicity amplitudes and the decay rate.Comment: 8 pages, 1 figure. Added references and discussio

    A look inside charmed-strange baryons from lattice QCD

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    The electromagnetic form factors of the spin-3/2 Ω\Omega baryons, namely Ω\Omega, Ωc∗\Omega_c^\ast, Ωcc∗\Omega_{cc}^\ast and Ωccc\Omega_{ccc}, are calculated in full QCD on 323×6432^3\times 64 PACS-CS lattices with a pion mass of 156(9) MeV. The electric charge radii and magnetic moments from the E0E0 and M1M1 multipole form factors are extracted. Results for the electric quadrupole form factors, E2E2, are also given. Quark sector contributions are computed individually for each observable and then combined to obtain the baryon properties. We find that the charm quark contributions are systematically smaller than the strange-quark contributions in the case of the charge radii and magnetic moments. E2E2 moments of the Ωcc∗\Omega_{cc}^\ast and Ωccc\Omega_{ccc} provide a statistically significant data to conclude that their electric charge distributions are deformed to an oblate shape. Properties of the spin-1/2 Ωc\Omega_c and Ωcc\Omega_{cc} baryons are also computed and a thorough comparison is given. This complete study gives valuable hints about the heavy-quark dynamics in charmed hadrons.Comment: 14 pages, 14 figures. Includes a subsection on the systematic effect

    CP violation in polarized B-> pi ell+ ell- and B-> rho ell+ ell- decays

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    We study the decay rate and the CP violating asymmetry of the exclusive B-> pi ell+ ell- and B-> rho ell+ ell- decays in the case where one of the final leptons is polarized. We calculate the contributions coming from the individual polarization states in order to identify a so-called wrong sign decay, which is a decay with a given polarization, whose width and CP asymmetry are smaller as compared to the unpolarized one. The results are presented for electron and tau leptons. We observe that in particular decay channels, one can identify a wrong sign decay which is more sensitive to new physics beyond the Standard Model.Comment: 24 pages, 10 figures; minor errors and misprints corrected, references added, version to be published in EPJ

    Electromagnetic properties of doubly charmed baryons in Lattice QCD

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    We compute the electromagnetic properties of \Xi_cc baryons in 2+1 flavor Lattice QCD. By measuring the electric charge and magnetic form factors of \Xi_cc baryons, we extract the magnetic moments, charge and magnetic radii as well as the \Xi_cc \Xi_cc \rho coupling constant, which provide important information to understand the size, shape and couplings of the doubly charmed baryons. We find that the two heavy charm quarks drive the charge radii and the magnetic moment of \Xi_cc to smaller values as compared to those of, e.g., the proton.Comment: 15 pages, 5 figures; added discussions and references, version accepted by PL

    Vector and axial-vector couplings of D and D* mesons in 2+1 flavor Lattice QCD

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    Using the axial-vector coupling and the electromagnetic form factors of the D and D* mesons in 2+1 flavor Lattice QCD, we compute the D*D\pi, DD\rho and D*D*\rho coupling constants, which play an important role in describing the charm hadron interactions in terms of meson-exchange models. We also extract the charge radii of D and D* mesons and determine the contributions of the light and charm quarks separately.Comment: 19 pages, 3 figures; added references and comments, published versio
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