35 research outputs found
Eikonal zeros in the momentum transfer space from proton-proton scattering: An empirical analysis
By means of improved empirical fits to the differential cross section data on
elastic scattering at GeV and making use of a
semi-analytical method, we determine the eikonal in the momentum transfer space
(the inverse scattering problem). This method allows the propagation of the
uncertainties from the fit parameters up to the extracted eikonal, providing
statistical evidence that the imaginary part of the eikonal (real part of the
opacity function) presents a zero (change of signal) in the momentum space, at
GeV. We discuss the implication of this change of
signal in the phenomenological context, showing that eikonal models with one
zero provide good descriptions of the differential cross sections in the full
momentum transfer range, but that is not the case for models without zero.
Empirical connections between the extracted eikonal and results from a recent
global analysis on the proton electric form factor are also discussed, in
special the Wu-Yang conjecture. In addition, we present a critical review on
the differential cross section data presently available at high energies.Comment: Two references and some misprints corrected, 22 pages; final version
to be published in Eur.Phys. J. C (2008
A remark on the tau-neutrino mass limit
We point out that the usual experimental upper bounds on the ``tau-neutrino
mass'' do not apply if neutrino mixing is considered. The suppression of the
population of the tau decay spectrum near the end-point, caused by mixing, may
be compensated by an enhancement due to a resonant mechanism of hadronization.
It is necessary therefore to analyse the whole spectrum to infer some limit to
the ``tau-neutrino mass". We argue that, consequently, neutrino mixing evades
the objection to interpret KARMEN anomaly as a heavy sequential neutrino.Comment: 9 pages, RevTeX 3.0 file, 1 figure contained in a postscript file
appended in the end of the documen
Was the GLE on May 17, 2012 linked with the M5.1-class flare the first in the 24th solar cycle?
On May 17, 2012 an M5.1-class flare exploded from the sun. An O-type coronal
mass ejection (CME) was also associated with this flare. There was an instant
increase in proton flux with peak at MeV, leading to S2 solar
radiation storm level. In about 20 minutes after the X-ray emission, the solar
particles reached the Earth.It was the source of the first (since December
2006) ground level enhancement (GLE) of the current solar cycle 24. The GLE was
detected by neutron monitors (NM) and other ground based detectors. Here we
present an observation by the Tupi muon telescopes (Niteroi, Brazil, , , 3 m above sea level) of the enhancement of muons at ground
level associated with this M5.1-class solar flare. The Tupi telescopes
registered a muon excess over background in the 5-min binning time
profile. The Tupi signal is studied in correlation with data obtained by
space-borne detectors (GOES, ACE), ground based neutron monitors (Oulu) and air
shower detectors (the IceTop surface component of the IceCube neutrino
observatory). We also report the observation of the muon signal possibly
associated with the CME/sheath striking the Earth magnetosphere on May 20,
2012. We show that the observed temporal correlation of the muon excess
observed by the Tupi muon telescopes with solar transient events suggests a
real physical connection between them. Our observation indicates that
combination of two factors, the low energy threshold of the Tupi muon
telescopes and the location of the Tupi experiment in the South Atlantic
Anomaly region, can be favorable in the study and detection of the solar
transient events. Our experiment provides new data complementary to other
techniques (space and ground based) in the study of solar physics.Comment: 9 pages, 10 figure