378 research outputs found
Tau weak dipole moments from azimuthal asymmetries
We show that transverse and normal single- polarization of pairs
produced at unpolarized collisions, at the peak, are sensitive
to weak (magnetic and electric) dipole moments of the . We also show how
these components of the polarization are accessible by measuring
appropriate azimuthal asymmetries in the angular distribution of its decay
products. Sensitivities of the order of , for the
weak-electric dipole moment, and (), for the real
(imaginary) part of the weak-magnetic dipole moment of , may be achieved.
Compatible bounds are also presented from spin-spin correlated asymmetries.Comment: Talk given at the TAU'98 Workshop, September 1998, Santander, Spain.
8 pages, 2 figure
CP violation and electric-dipole-moment at low energy tau-pair production
CP violation at low energy is investigated at the tau electromagnetic vertex.
High statistics at B factories, and on top of the Upsilon resonances, allows a
detailed investigation of CP-odd observables related to the tau-pair
production. The contribution of the tau electric dipole moment is considered in
detail. We perform an analysis independent from the high energy data by means
of correlation and linear spin observables at low energy. We show that
different CP-odd asymmetries, associated to the normal-transverse and
normal-longitudinal correlation terms can be measured at low energy
accelerators, both at resonant and non resonant energies. These observables
allow to put stringent and independent bounds to the tau electric dipole moment
that are competitive with other high or low energy results.Comment: 18 pages, 2 figures, references added, minor changes in section 3 and
5, to be published in Nucl.Phys.
CP violation and electric-dipole-moment at low energy production with polarized electrons
The new proposals for high luminosity B/Flavor factories, near and on top of
the resonances, allow for a detailed investigation of CP-violation
in the -pair production. In particular, bounds on the tau electric dipole
moment can be obtained from genuine CP-odd observables related to the
-pair production. We perform an independent analysis from low energy (10
GeV) data by means of linear spin observables. We show that, for a
longitudinally polarized electron beam, a CP-odd asymmetry, associated to the
normal polarization term, can be measured at these low energy facilities both
at resonant and non resonant energies. In this way, stringent and independent
bounds to the tau electric dipole moment, which are orders of magnitude below
other high or low energy bounds, can be obtained.Comment: 12 pages, 2 figure
Tau EDM at Low Energies
Low energy tau pair production, at B factories and on top of the
resonances, allows for a detailed investigation on the CP violation at the
electromagnetic tau pair production vertex. High statistic available at low
energies offers the opportunity for an independent analysis of CP-violation in
the lepton physics. We show that stringent and independent bounds on the
electric dipole moment, competitive with the high energy measurements,
can be established in low energies experiments.Comment: Talk at the Seventh International Workshop on Tau Lepton Physics
(TAU02), Santa Cruz, Ca, USA, Sept 2002, 5 pages, LaTeX, 1 eps figur
Dynamical zeros in neutrino-electron elastic scattering at leading order
We show the existence of dynamical zeros in the helicity amplitudes for
neutrino-electron elastic scattering at lowest order in the standard theory. In
particular, the non-flip electron helicity amplitude in the
electron antineutrino process vanishes for an incident neutrino energy
and forward electrons (maximum recoil
energy). The rest of helicity amplitudes show kinematical zeros in this
configuration and therefore the cross section vanishes. Prospects to search for
neutrino magnetic moment are discussed.Comment: 9 pg.+ 2 figures (not included available upon request
A Novel Kind of Neutrino Oscillation Experiment
A novel method to look for neutrino oscillations is proposed based on the
elastic scattering process , taking advantage of the dynamical zero present in the differential
cross section for . An
effective tunable experiment between the "appearance" and "disappearance"
limits is made possible. Prospects to exclude the allowed region for
atmospheric neutrino oscillations are given.Comment: 11 pages (+3 figures, available upon request),Standard Latex,
FTUV/94-3
The Capabilities of Monochromatic EC Neutrino Beams with the SPS Upgrade
The goal for future neutrino facilities is the determination of the U(e3)
mixing and CP violation in neutrino oscillations. This will require precision
experiments with a very intense neutrino source and energy control. With this
objective in mind, the creation of monochromatic neutrino beams from the
electron capture decay of boosted ions by the SPS of CERN has been proposed. We
discuss the capabilities of such a facility as a function of the energy of the
boost and the baseline for the detector. We conclude that the SPS upgrade to
1000 GeV is crucial to reach a better sensitivity to CP violation iff it is
accompanied by a longer baseline. We compare the physics potential for two
different configurations: I) and (maximum achievable
at present SPS) to Frejus; II) and (maximum
achievable at upgraded SPS) to Canfranc. The main conclusion is that, whereas
the gain in the determination of U(e3) is rather modest, setup II provides much
better sensitivity to CP violation.Comment: 4 pages, 5 figures, To appear in the proceedings of International
Europhysics Conference on High Energy Physics (EPS-HEP2007), Manchester,
England, 19-25 July 200
Determining the Neutrino Mass Hierarchy and CP Violation in NOvA with a Second Off-Axis Detector
We consider a Super-NOvA-like experimental configuration based on the use of
two detectors in a long-baseline experiment as NOvA. We take the far detector
as in the present NOvA proposal and add a second detector at a shorter
baseline. The location of the second off-axis detector is chosen such that the
ratio L/E is the same for both detectors, being L the baseline and E the
neutrino energy. We consider liquid argon and water-Cherenkov techniques for
the second off-axis detector and study, for different experimental setups, the
detector mass required for the determination of the neutrino mass hierarchy,
for different values of theta13. We also study the capabilities of such an
experimental setup for determining CP violation in the neutrino sector. Our
results show that by adding a second off-axis detector a remarkable enhancement
on the capabilities of the current NOvA experiment could be achieved.Comment: 20 p
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