1,886 research outputs found

### $\Lambda(1520)$ and $\Sigma(1385)$ in the nuclear medium

Recent studies of the $\Lambda(1520)$ 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 $\pi \Sigma^*(1385)$ in this case, although the coupling
of the $\Lambda(1520)$ to the $\bar{K}N$ and $\pi \Sigma$ makes this picture
only approximate. The $\pi \Sigma^*(1385)$ decay channel of the $\Lambda(1520)$
is forbidden in free space for the nominal mass of the $\Sigma^*(1385)$, but
the coupling of the $\pi$ to $ph$ components in the nuclear medium opens new
decay channels of the $\Lambda(1520)$ in the nucleus and produces a much larger
width. Together with medium modifications of the $\bar{K}N$ and $\pi \Sigma$
decay channels, the final width of the $\Lambda(1520)$ at nuclear matter
density is more than five times bigger than the free one. We perform the
calculations by dressing simultaneously the $\Lambda(1520)$ and the
$\Sigma^*(1385)$ 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

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 $\eta_b$ searching: double $J/\psi$ or something else?

It has been controversial whether $\eta_b$ can be discovered in Tevatron Run
2 through the decay $\eta_b\to J/\psi J/\psi$ followed by $J/\psi\to
\mu^+\mu^-$. We clear this controversy by an explicit calculation which
predicts ${\rm Br}[\eta_b\to J/\psi J/\psi]$ to be of order $10^{-8}$. 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

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

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 $B^0$ meson asymmetry

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 $B^0$
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 $K^0$ meson physics.Comment: 7 page

### Flavor-Spin Symmetry and the Tensor Charge

Exploiting an approximate phenomenological symmetry of the $J^{PC}=1^{+-}$
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

In the framework of potential models for heavy quarkonium, we compute the
mass spectrum of the bottom-charmed $B_{c}$ 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 $B_{c}^{+}$ and
pseudoscalar $B_{c}$ states as well as the higher states below the threshold
are estimated. Our predicted result for the ground state energy is $%
6253_{-6}^{+15}$ $MeV$ 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

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

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

Based on a semiclassical expansion for quantum chromodynamics in the
instanton liquid background, the correlation function of the $0^{++}$ scalar
glueball current is given, and the properties of the $0^{++}$ 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 $0^{++}$ resonance, in which the scalar glueball fraction is dominant, are
obtained.Comment: 18pages, 9figure

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