6,261 research outputs found
Tau-Mu Flavor Violation and the Scale of New Physics
Motivated by the strong experimental evidence of large nu_mu - nu_tau
neutrino oscillations, we study existing constraints for related mu - tau
flavor violation. Using a general bottom-up approach, we construct dimension-6
effective fermionic operators whose coefficients encode the scale of new
physics associated with mu - tau flavor violation, which is a piece in the
puzzle of the origin of neutrino oscillations. We survey existing experimental
bounds on this scale, which arise mostly from tau and B decays. In many cases
the new physics scale is constrained to be above a few TeV. We also discuss the
operators which are either weakly constrained or, at present, subject to no
experimental bounds.Comment: Proceedings for MRST 2003, Joe Schechter Fest, Syracuse University,
New York, May 2003. 8 pages, 2 figure
An improved study of the kappa resonance and the non-exotic wave scatterings up to GeV of LASS data
We point out that the dispersion relation for the left hand cut integral
presented in one of our previous paper (Nucl. Phys. {\bf A}733(2004)235) is
actually free of subtraction constant, even for unequal mass elastic
scatterings. A new fit to the LASS data~\cite{Aston} is performed and firm
evidence for the existence of pole is found. The correct use of
analyticity also put strong constraints on threshold parameters -- which are
found to be in good agreement with those obtained from chiral theories. We also
determined the pole parameters of on the second sheet, and
reconfirm the existence of on the third sheet. We stress that the
LASS data do not require them to have the twin pole structure of a typical
Breit--Wigner resonance.Comment: 14 pages + 4 postscript figures; discussions largely expanded;
references added; version to appear in NPA; title changed in the journa
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