Statistical hadronization and hadronic microcanonical ensemble II

We present a Monte-Carlo calculation of the microcanonical ensemble of the of the ideal hadron-resonance gas including all known states up to a mass of about 1.8 GeV and full quantum statistics. The microcanonical average multiplicities of the various hadron species are found to converge to the canonical ones for moderately low values of the total energy, around 8 GeV, thus bearing out previous analyses of hadronic multiplicities in the canonical ensemble. The main numerical computing method is an importance sampling Monte-Carlo algorithm using the product of Poisson distributions to generate multi-hadronic channels. It is shown that the use of this multi-Poisson distribution allows an efficient and fast computation of averages, which can be further improved in the limit of very large clusters. We have also studied the fitness of a previously proposed computing method, based on the Metropolis Monte-Carlo algorithm, for event generation in the statistical hadronization model. We find that the use of the multi-Poisson distribution as proposal matrix dramatically improves the computation performance. However, due to the correlation of subsequent samples, this method proves to be generally less robust and effective than the importance sampling method.Comment: 23 pages, 21 figures, style files attached. Published version, minor correction

A search for the fourth SM family quarks at Tevatron

It is shown that the fourth standard model (SM) family quarks can be observed at the Fermilab Tevatron if their anomalous interactions with known quarks have sufficient strength.Comment: 7 pages, 2 tables, 4 figure

Double-lepton polarization asymmetries in the (B -> K l^+ l^-) decay beyond the Standard Model

General expressions for the double-lepton polarizations in the (B -> K l^+ l^-) decay are obtained, using model independent effective Hamiltonian, including all possible interactions. Correlations between the averaged double-lepton polarization asymmetries and the branching ratio, as well as, the averaged single-lepton polarization asymmetry are studied. It is observed that, study of the double-lepton polarization asymmetries can serve as a good test for establishing new physics beyond the Standard Model.Comment: 21 pages, 18 figures, LaTeX formatte

Monte Carlo simulation for radiative kaon decays

For high precision measurements of K decays, the presence of radiated photons cannot be neglected. The Monte Carlo simulations must include the radiative corrections in order to compute the correct event counting and efficiency calculations. In this paper we briefly describe a method for simulating such decays.Comment: 11 pages, 1 figur

Flavor changing neutral currents from lepton and B decays in the two Higgs doublet model

Constraints on the whole spectrum of lepton flavor violating vertices are shown in the context of the standard two Higgs doublet model. The vertex involving the $e-\tau$ mixing is much more constrained than the others, and the decays proportional to such vertex are usually very supressed. On the other hand, bounds on the quark sector are obtained from leptonic decays of the $B_{d,s}^{0}$ mesons and from $\Delta M_{B_{d}^{0}}$. We emphasize that although the $B_{d}^{0}-\bar{B}_{d}^{0}$ mixing restricts severely the $$ mixing vertex, the upper bound for this vertex could still give a sizeable contribution to the decay $B_{d}^{0}\to \mu \bar{\mu}$ respect to the standard model contribution, from which we see that such vertex could still play a role in the phenomenology.Comment: 9 pages, 2 figures, LaTeX2e. Minor typos corrected. References added and corrected. Introduction change

Little Higgs models and single top production at the LHC

We investigate the corrections of the littlest Higgs(LH) model and the SU(3) simple group model to single top production at the CERN Large Hardon Collider(LHC). We find that the new gauge bosons $W_{H}^{\pm}$ predicted by the LH model can generate significant contributions to single top production via the s-channel process. The correction terms for the tree-level $Wqq'$ couplings coming from the SU(3) simple group model can give large contributions to the cross sections of the t-channel single top production process. We expect that the effects of the LH model and the SU(3) simple group model on single top production can be detected at the LHC experiments.Comment: 17pages, 5 figures, discussions and references added, typos correcte

Bright solitons and soliton trains in a fermion-fermion mixture

We use a time-dependent dynamical mean-field-hydrodynamic model to predict and study bright solitons in a degenerate fermion-fermion mixture in a quasi-one-dimensional cigar-shaped geometry using variational and numerical methods. Due to a strong Pauli-blocking repulsion among identical spin-polarized fermions at short distances there cannot be bright solitons for repulsive interspecies fermion-fermion interactions. However, stable bright solitons can be formed for a sufficiently attractive interspecies interaction. We perform a numerical stability analysis of these solitons and also demonstrate the formation of soliton trains. These fermionic solitons can be formed and studied in laboratory with present technology.Comment: 5 pages, 7 figure

Muon anomalous magnetic moment and lepton flavor violation in MSSM

We give a thorough analysis of the correlation between the muon anomalous magnetic moment and the radiative lepton flavor violating (LFV) processes within the minimal supersymmetric standard model. We find that in the case when the slepton mass eigenstates are nearly degenerate, $\delta a_\mu$, coming from SUSY contributions, hardly depends on the lepton flavor mixing and, thus, there is no direct relation between $\delta a_\mu$ and the LFV processes. On the contrary, if the first two generations' sleptons are much heavier than the 3rd one, i.e., in the effective SUSY scenario, the two quantities are closely related. In the latter scenario, the SUSY parameter space to account for the experimental $\delta a_\mu$ is quite different from the case of no lepton flavor mixing. Especially, the Higgsino mass parameter $\mu$ can be either positive or negative.Comment: 22 pages, 9 figures; Some discussions are modifie

Non-perturbative Pion Matrix Element of a twist-2 operator from the Lattice

We give a continuum limit value of the lowest moment of a twist-2 operator in pion states from non-perturbative lattice calculations. We find that the non-perturbatively obtained renormalization group invariant matrix element is _{RGI} = 0.179(11), which corresponds to ^{MSbar}(2 GeV) = 0.246(15). In obtaining the renormalization group invariant matrix element, we have controlled important systematic errors that appear in typical lattice simulations, such as non-perturbative renormalization, finite size effects and effects of a non-vanishing lattice spacing. The crucial limitation of our calculation is the use of the quenched approximation. Another question that remains not fully clarified is the chiral extrapolation of the numerical data.Comment: 26 pages, 10 figures, v2: final version, accepted for publication in EPJ

Flavor coupled with chiral oscillations in the presence of an external magnetic field

By reporting to the Dirac wave-packet prescription where it is formally assumed the {\em fermionic} nature of the particles, we shall demonstrate that chiral oscillations implicitly aggregated to the interference between positive and negative frequency components of mass-eigenstate wave-packets introduce some small modifications to the standard neutrino flavor conversion formula. Assuming the correspondent spinorial solutions of a ``modified'' Dirac equation, we are specifically interested in quantifying flavor coupled with chiral oscillations for a {\em fermionic} Dirac-{\em type} particle (neutrino) non-minimally coupling with an external magnetic field {\boldmath$B$}. The viability of the intermediate wave-packet treatment becomes clear when we assume {\boldmath$B$} orthogonal/parallel to the direction of the propagating particle.Comment: 21 page