Suppression of Non-photonic Electrons from Enhancement of Charm Baryons in Heavy Ion Collisions

At intermediate transverse momentum (2 < p_T < 6 GeV/c), baryon production in Au+Au collisions is enhanced compared to p+p collisions. Since charm baryon decays produce electrons less frequently than charm meson decays, the non-photonic electron spectrum is sensitive to the Lambda_c/D ratio. In this report we study the dependence of the non-photonic electron spectrum on the baryon-to-meson ratio for charm hadrons. As an example, we take the Lambda_c/D ratio to have the same form as the Lambda/K^0_S ratio. In this case, even if the total charm quark yield in Au+Au collisions scales with the number of binary nucleon-nucleon collisions (N_bin), the electron spectrum at 2 < p_T < 5 GeV/c is suppressed relative to N_bin scaled p+p collisions by as much as 20%.Comment: Added STAR data to figure 1 and made slight text modifications (fixed figure replacement

Scalar Sector in the Minimal Supersymmetric 3-3-1 model

We consider the minimal supersymmetric extension of the 3-3-1 model and we study the mass spectra in the scalar sector of this model without the anti-sextet. We show that all our lighest scalars are in agreement with the experimental limits.Comment: It was included on the introduction of the article the motivation to > study the model, and we moved the sections 4.1 and 4.2 to the appendix. It has 22 pages, 9 figures. It was accepted to be published at International Journal of Modern Physics

Gauge invariance, radiative interferences and properties of vector mesons

We state the implications on the properties of vector mesons due to gauge invariance. In particular, we find that polarized vector mesons exhibit a property in the radiation distribution of order $\omega^{-1}$ in the photon energy, namely it is null when the gyromagnetic ratio becomes $g=2$. Therefore, the generalization of the Burnett-Kroll theorem for polarized vector-meson states is held only if $g=2$. In addition, radiative interferences between the electric charge and any gauge invariant term is found to be parametrized by a common global factor which can be used to extract information of the involved states by a proper choice of the kinematical region, where they could be relevant.Comment: 5 pages, 1 figure. To appear in the Proceedings of the IX Mexican Workshop on Particles and Fields, Colima Mexico. Uses RevTex

Updated Estimate of the Muon Magnetic Moment Using Revised Results from e+e- Annihilation

A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy e+e- annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between e+e- and tau spectral functions in the pi pi channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and 1.0 GeV, so that we refrain from averaging the two data sets. The values found for the lowest-order hadronic vacuum polarization contributions are a_mu[had,LO] = (696.3 +- 6.2[exp] +- 3.6[rad])e-10 (e+e- -based) and a_mu[had,LO] = (711.0 +- 5.0[exp] +- 0.8[rad] +- 2.8[SU2])e-10 (tau-based), where the errors have been separated according to their sources: experimental, missing radiative corrections in e+e- data, and isospin breaking. The corresponding Standard Model predictions for the muon magnetic anomaly read a_mu = (11,659,180.9 +- 7.2[had] +- 3.5[LBL] +- 0.4[QED+EW])e-10 (e+e- -based) and a_mu = (11,659,195.6 +- 5.8[had] +- 3.5[LBL] +- 0.4[QED+EW])e-10 (tau-based), where the errors account for the hadronic, light-by-light (LBL) scattering and electroweak contributions. The deviations from the measurement at BNL are found to be (22.1 +- 7.2 +- 3.5 +- 8.0)e-10 (1.9 sigma) and (7.4 +- 5.8 +- 3.5 +- 8.0)e-10 (0.7 sigma) for the e+e- and tau-based estimates, respectively, where the second error is from the LBL contribution and the third one from the BNL measurement.Comment: 14 pages, 7 figures (to be submitted to Phys Lett B

Two-Loop Heavy-Flavor Contribution to Bhabha Scattering

We evaluate the two-loop QED corrections to the Bhabha scattering cross section which involve the vacuum polarization by heavy fermions of arbitrary mass m_f >> m_e. The results are valid for generic values of the Mandelstam invariants s,t,u >> m_e^2.Comment: 13 pages, 6 figures. Equations in the appendix generalized to the heavy-quark cas