1,886 research outputs found

    Λ(1520)\Lambda(1520) and Σ(1385)\Sigma(1385) in the nuclear medium

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    Recent studies of the Λ(1520)\Lambda(1520) resonance within chiral unitary theory with coupled channels find the resonance as a dynamically generated state from the interaction of the decuplet of baryons and the octet of mesons, essentially a quasibound state of πΣ(1385)\pi \Sigma^*(1385) in this case, although the coupling of the Λ(1520)\Lambda(1520) to the KˉN\bar{K}N and πΣ\pi \Sigma makes this picture only approximate. The πΣ(1385)\pi \Sigma^*(1385) decay channel of the Λ(1520)\Lambda(1520) is forbidden in free space for the nominal mass of the Σ(1385)\Sigma^*(1385), but the coupling of the π\pi to phph components in the nuclear medium opens new decay channels of the Λ(1520)\Lambda(1520) in the nucleus and produces a much larger width. Together with medium modifications of the KˉN\bar{K}N and πΣ\pi \Sigma decay channels, the final width of the Λ(1520)\Lambda(1520) at nuclear matter density is more than five times bigger than the free one. We perform the calculations by dressing simultaneously the Λ(1520)\Lambda(1520) and the Σ(1385)\Sigma^*(1385) resonances, finding moderate changes in the mass but substantial ones in the width of both resonances.Comment: 20 pages, 6 figures; comparison made to data, new references and new (small) decay channel include

    Proton Decay, Fermion Masses and Texture from Extra Dimensions in SUSY GUTs

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    In supersymmetry, there are gauge invariant dimension 5 proton decay operators which must be suppressed by a mass scale much larger than the Planck mass. It is natural to expect that this suppression should be explained by a mechanism that explains the hierarchical structure of the fermion mass matrices. We apply this argument to the case where wave functions of chiral multiplets are localized under a kink background along an extra spatial dimension and the Yukawa couplings as well as the coefficients of the proton decay operators are determined by the overlap of the relevant wave functions. A configuration is found in the context of SU(5) supersymmetric grand unified theory that yields realistic values of quark masses, mixing angles, CP phase and charged lepton masses and sufficiently small genuine dimension 5 proton decay operators. Inclusion of SU(5) breaking effects is essential in order to obtain non-vanishing CP phase as well as correct lepton masses. The resulting mass matrix has a texture structure in which texture zeros are a consequence of extremely small overlap of the wave functions. Our approach requires explicit breaking of supersymmetry in the extra dimension, which can be realized in (de)constructing extra dimension.Comment: 23 pages, 2 figures, comments adde

    Which hadronic decay modes are good for ηb\eta_b searching: double J/ψJ/\psi or something else?

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    It has been controversial whether ηb\eta_b can be discovered in Tevatron Run 2 through the decay ηbJ/ψJ/ψ\eta_b\to J/\psi J/\psi followed by J/ψμ+μJ/\psi\to \mu^+\mu^-. We clear this controversy by an explicit calculation which predicts Br[ηbJ/ψJ/ψ]{\rm Br}[\eta_b\to J/\psi J/\psi] to be of order 10810^{-8}. It is concluded that observing eta_b through this decay mode in Tevatron Run 2 is rather unrealistic. The eta_b may be observed in the forthcoming LHC experiments through the 4-lepton channel, if the background events can be significantly reduced by imposing some kinematical cuts. By some rough but plausible considerations, we find that the analogous decay processes eta_b to VV, D^*\bar{D}^* also have very suppressed branching ratios, nevertheless it may be worth looking for \eta_b at LHC and Super B factory through the decay modes \eta_b \to K_S K^{\pm}\pi^{\mp}, D^*\bar{D}.Comment: v2; 28 pages, 2 figures. References added, presentation improved. Discussion on possible nonperturbative mechanism for eta_b->VV added, analysis for eta_b->VP updated by incoprating the U-spin violation effec

    Mass generation and the dynamical role of the Katoptron Group

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    Heavy mirror fermions along with a new strong gauge interaction capable of breaking the electroweak gauge symmetry dynamically were recently introduced under the name of katoptrons. Their main function is to provide a viable alternative to the Standard-Model Higgs sector. In such a framework, ordinary fermions acquire masses after the breaking of the strong katoptron group which allows mixing with their katoptron partners. The purpose of this paper is to study the elementary-scalars-free mechanism responsible for this breaking and its implications for the fermion mass hierarchies.Comment: 15 LaTeX pages, some comments added, version published in Modern Physics Letters

    Evaluation of a laboratory test model annular momentum control device

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    A 4068 Nm Sec laboratory test model annular momentum control device (AMCD) was described and static and dynamic test results were presented. An AMCD is a spinning annular rim suspended by noncontacting magnetic bearings and powered by a noncontacting linear electromagnetic motor. Test results include spin motor torque characteristics and spin motor and magnetic bearing drag losses. Limitations of some of the design approaches taken was also discussed

    Theoretical correction to the neutral B0B^0 meson asymmetry

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    Certain types of asymmetries in neutral meson physics have not been treated properly, ignoring the difference of normalization factors with an assumption of the equality of total decay width. Since the corrected asymmetries in B0B^0 meson are different from known asymmetries by a shift in the first order of CP- and CPT-violation parameters, experimental data should be analyzed with the consideration of this effect as in K0K^0 meson physics.Comment: 7 page

    Flavor-Spin Symmetry and the Tensor Charge

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    Exploiting an approximate phenomenological symmetry of the JPC=1+J^{PC}=1^{+-} light axial vector mesons and using pole dominance, we calculate the flavor contributions to the nucleon tensor charge. The result depends on the decay constants of the axial vector mesons and their couplings to the nucleons.Comment: Talk given at 3rd Circum-Pan-Pacific Symposium on High Energy Spin Physics (SPIN 2001), Beijing, China, 8-13 Oct 200

    B_c meson spectrum and hyperfine splittings in theshifted large-N-expansion technique

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    In the framework of potential models for heavy quarkonium, we compute the mass spectrum of the bottom-charmed BcB_{c} meson system and spin-dependent splittings from the Schr\"{o}dinger equation using the shifted-large-N expansion technique. The masses of the lightest vector Bc+B_{c}^{+} and pseudoscalar BcB_{c} states as well as the higher states below the threshold are estimated. Our predicted result for the ground state energy is 62536+15% 6253_{-6}^{+15} MeVMeV and are generally in exact agreement with earlier calculations. Calculations of the Schr\"{o}dinger energy eigenvalues are carried out up to third order of the energy series. The parameters of each potential are adjusted to obtain best agreement with the experimental spin-averaged data (SAD). Our findings are compared with the observed data and with the numerical results obtained by other numerical methods.Comment: 28 pages, Late

    Neutrinos from the Propagation of a Relativistic Jet Through a Star

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    We discuss the neutrino signature of a relativistic jet propagating through a stellar envelope, a scenario realized in the collapsar model for Gamma Ray Bursts (GRBs). It is shown that the dramatic slowing of the jet deep within the star is accompanied by inelastic neutron-nucleon collisions and the conversion of a substantial fraction of the jet kinetic energy to neutrinos. These neutrinos have observed energies in the range two to tens of GeV and an estimated detection rate comparable to or larger than the detection rate of GeV neutrinos from other GRB-related processes. The time delay between the arrival of these neutrinos and the GRB photons is tens of seconds. An observation of this delay would provide an indication that the GRB jet originated in a massive star.Comment: To appear in Ap

    0++0^{++} scalar glueball in finite-width Gaussian sum rules

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    Based on a semiclassical expansion for quantum chromodynamics in the instanton liquid background, the correlation function of the 0++0^{++} scalar glueball current is given, and the properties of the 0++0^{++} scalar glueball are studied in the framework of Gaussian sum rules. Besides the pure classical and quantum contributions, the contributions arising from the interactions between the classical instanton fields and quantum gluons are come into play. Instead of the usual zero-width approximation for the resonance, the Breit-Wigner form for the spectral function of the finite-width resonance is adopted. The family of the Gaussian sum rules for the scalar glueball in quantum chromodynamics with and without light quarks is studied. A consistency between the subtracted and unsubtracted sum rules is very well justified, and the values of the decay width and the coupling to the corresponding current for the 0++0^{++} resonance, in which the scalar glueball fraction is dominant, are obtained.Comment: 18pages, 9figure
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