arXiv subjects
Publications and source records attributed to C. O. Escobar.
We show that the classical stochastic motion of an open bosonic string leads to the same results as the standard first quantization of this system. For this, the diffusion constant governing the process has to be proportional to α', the Regge slope parameter, which is the only constant, along with the velocity of light, needed to describe the motion of a string.
The potentiality of a Giant Shower Array to low energy gamma rays from gamma ray bursts is discussed. Effective areas are calculated for different scenarios and the results are encouraging. If gamma ray bursts have a spectrum which continues in the high energy gamma ray region, the Pierre Auger Observatory will be able to detect it.
We argue that magnetic monopoles can not be associated to the highest energy cosmic rays as recently suggested. Both the observed spectrum and the arrival direction disagree with observation.
We investigate the impact of new physics beyond the Standard Model to the $s \rightarrow d γ$ process, which is responsible for the short-distance contribution to the radiative decay $\Otogamma$. We study three representative extensions of the Standard Model, namely a one-family technicolor model, a two Higgs doublet model and a model containing scalar leptoquarks. When constraints arising from the observed $b \to s γ$ transition and the upper limit on $D^0 - \bar{D}^0$ mixing are taken into account, we find no significant contributions of new physics to the $s \to d γ$ process.
QCD sum rules are used to calculate the contribution of short-distance single-quark transition $s\rightarrow d γ$, to the amplitudes of the hyperon radiative decay, $Ω^-\rightarrow Ξ^-γ$. We re-evaluate the Wilson coefficient of the effective operator responsible for this transition. We obtain a branching ratio which is comparable to the unitarity limit.
We study the constraints on masses and mixing angles imposed by the measured $Z^0$ invisible width, in a model in which a singlet right-handed neutrino mixes with all the Standard Model neutrinos.