56 research outputs found
Quark-Antiquark Potential and Generalized Borel Transform
The heavy quark potential and particularly the one proposed by Richardson to
incorporate both asymptotic freedom and linear confinement is analyzed in terms
of a generalized Borel Transform recently proposed. We were able to obtain, in
the range of physical interest, an approximate analytical expression for the
potential in coordinate space valid even for intermediate distances. The
deviation between our approximate potential and the numerical evaluation of the
Richardson's one is much smaller than of QCD. The
and quarkonia energy levels agree reasonably well with
experimental data for and masses in good agreement with the values
obtained from experiments.Comment: 9 pages, 3 Tabl
On Charge Quantization and Abelian Gauge Horizontal Symmetries
Under the assumption that there exists a local gauge horizontal symmetry
wich allows only for a top quark mass at tree level, we look for the
constraints that charge quatization and the family structure of the standard
model imposes on that symmetry.Comment: 13 pages, LaTeX, Acepted in Physics Letters
Next to Leading Order Semi-inclusive Spin Asymmetries
We have computed semi-inclusive spin asymmetries for proton and deuteron
targets including next to leading order (NLO) QCD corrections and contributions
coming from the target fragmentation region. These corrections have been
estimated using NLO fragmentation functions, parton distributions and also a
model for spin dependent fracture functions which is proposed here. We have
found that NLO corrections are small but non-negligible in a scheme where
gluons are polarised and that our estimate for target fragmentation effects
does not modify significantly charged asymmetries but affects the so called
difference asymmetries.Comment: Latex, 14 pages, 6 figures in 4 Postcript file
Looking for magnetic monopoles at LHC with diphoton events
Magnetic monopoles have been a subject of interest since Dirac established
the relation between the existence of monopoles and charge quantization. The
intense experimental search carried thus far has not met with success. The
Large Hadron Collider is reaching energies never achieved before allowing the
search for exotic particles in the TeV mass range. In a continuing effort to
discover these rare particles we propose here other ways to detect them. We
study the observability of monopoles and monopolium, a monopole-antimonopole
bound state, at the Large Hadron Collider in the channel for
monopole masses in the range 500-1000 GeV. We conclude that LHC is an ideal
machine to discover monopoles with masses below 1 TeV at present running
energies and with 5 fb of integrated luminosity.Comment: This manuscript contains information appeared in Looking for magnetic
monopoles at LHC, arXiv:1104.0218 [hep-ph] and Monopolium detection at the
LHC.,arXiv:1107.3684 [hep-ph] by the same authors, rewritten for joint
publication in The European Physica Journal Plus. 26 pages, 22 figure
A Method to Determine the Tau Neutrino Helicity Using Polarized Taus
A method is presented to extract the tau neutrino helicity, or equivalently,
the chirality parameter , independent of any tau
polarization which may be present. The method is thus well-suited to
measurements using taus produced from the and is complementary to
analyses using tau correlations since it provides the sign of the chirality
parameter which is otherwise unavailable without recourse to lower energy
experiments where taus are unpolarized. Results of Monte Carlo studies and
comments regarding the use of the technique in experiments are also included.Comment: 13 pages, uuencoded postscript fil
SimProp: a Simulation Code for Ultra High Energy Cosmic Ray Propagation
A new Monte Carlo simulation code for the propagation of Ultra High Energy
Cosmic Rays is presented. The results of this simulation scheme are tested by
comparison with results of another Monte Carlo computation as well as with the
results obtained by directly solving the kinetic equation for the propagation
of Ultra High Energy Cosmic Rays. A short comparison with the latest flux
published by the Pierre Auger collaboration is also presented.Comment: 19 pages, 12 eps figures, version accepted for publication in JCA
Monopolium production from photon fusion at the Large Hadron Collider
Magnetic monopoles have attracted the attention of physicists since the founding of the electromagnetic theory. Their search has been a constant endeavor which was intensified when Dirac established the relation between the existence of monopoles and charge quantization. However, these searches have been unsuccessful. We have recently proposed that monopolium, a monopole-antimonopole bound state, so strongly bound that it has a relatively small mass, could be easier to find and become an indirect but clear signature for the existence of magnetic monopoles. In here we extend our previous analysis for its production to two photon fusion at LHC energies
Extragalactic Sources for Ultra High Energy Cosmic Ray Nuclei
In this article we examine the hypothesis that the highest energy cosmic rays
are complex nuclei from extragalactic sources. Under reasonable physical
assumptions, we show that the nearby metally rich starburst galaxies (M82 and
NGC 253) can produce all the events observed above the ankle. This requires
diffusion of particles below eV in extragalactic magnetic fields nG. Above eV, the model predicts the presence of
significant fluxes of medium mass and heavy nuclei with small rate of change of
composition. Notwithstanding, the most salient feature of the
starburst-hypothesis is a slight anisotropy induced by iron debris just before
the spectrum-cutoff.Comment: To appear in Phys. Rev. D, reference adde
Scaling anomaly in cosmic string background
We show that the classical scale symmetry of a particle moving in cosmic
string background is broken upon inequivalent quantization of the classical
system, leading to anomaly. The consequence of this anomaly is the formation of
single bound state in the coupling interval \gamma\in(-1,1). The inequivalent
quantization is characterized by a 1-parameter family of self-adjoint extension
parameter \omega. It has been conjectured that the formation of loosely bound
state in cosmic string background may lead to the so called anomalous
scattering cross section for the particles, which is usually seen in molecular
physics.Comment: 4 pages,1 figur
Anisotropy at the end of the cosmic ray spectrum?
The starburst galaxies M82 and NGC253 have been proposed as the primary
sources of cosmic rays with energies above eV. For energies \agt
10^{20.3} eV the model predicts strong anisotropies. We calculate the
probabilities that the latter can be due to chance occurrence. For the highest
energy cosmic ray events in this energy region, we find that the observed
directionality has less than 1% probability of occurring due to random
fluctuations. Moreover, during the first 5 years of operation at Auger, the
observation of even half the predicted anisotropy has a probability of less
than to occur by chance fluctuation. Thus, this model can be subject
to test at very small cost to the Auger priors budget and, whatever the outcome
of that test, valuable information on the Galactic magnetic field will be
obtained.Comment: Final version to be published in Physical Review
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