4,176 research outputs found
Invisible Z decay width bounds on active-sterile neutrino mixing in the (3+1) and (3+2) models
In this work we consider the standard model extended with singlet sterile
neutrinos with mass in the eV range and mixed with the active neutrinos. The
active-sterile neutrino mixing renders new contributions to the invisible Z
decay width which, in the case of light sterile neutrinos, depends on the
active-sterile mixing matrix elements only. We then use the current
experimental value of the invisible Z decay width to obtain bounds on these
mixing matrix elements for both (3+1) and (3+2) models.Comment: 10 pages, 5 figure
Five-Dimensional QED, Muon Pair Production and Correction to the Coulomb Potential
We consider QED in five dimensions in a configuration where matter is
localized on a 3-brane while foton propagates in the bulk. The idea is to
investigate the effects of the Kaluza-Klein modes of the photon in the
relativistic regime, but in low energy, and in the nonrelativistic regime. In
the relativistic regime, we calculate the cross section for the reaction . We compare our theoretical result with a precise
measurement of this cross section at GeV. As result, we
extract a lower bound on the size of the extra dimension. In the
nonrelativistic regime, we derive the contribution for the Coulomb potential
due to the whole tower of the Kaluza-Klein excited modes of the photon. We use
the modified potential to calculate the Rutherford scattering differential
cross section.Comment: minor changes, three new refs. added, to appear in IJMP
Estudo da herança da resistência a brusone em duas cultivares de arroz (Oryza sativa).
O objetivo do presente trabalho foi de identificar o número de alelos envolvidos na expressão da resistência qualitativa à brusone nas folhas nas cultivares Cica-8 e Metica-1.Conpeex 2010
Combining type I and type II seesaw mechanisms in the minimal 3-3-1 model
The minimal 3-3-1 model is perturbative until energies around 4-5TeV, posing
a challenge to generate neutrino masses at eV scale, mainly if one aims to take
advantage of the seesaw mechanism. As a means to circumvent this problem we
propose a modification of the model such that it accommodates the type I and
type II seesaw mechanisms altogether. We show that the conjunction of both
mechanisms yield a neutrino mass expression suppressed by a high power of the
cutoff scale, , in its denominator. With such a suppression term we
naturally obtain neutrino masses at eV scale when is around few TeV. We
also investigate the size of lepton flavor violation through the process .Comment: about 15 pages, no figure
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