Professor Amanda Cooper-Sarkar

Abstract:

Using the ZEUS detector at the HERA electronproton collider, we have searched for lepton flavor violation in ep collisions at a center—of—mass energy ($sqrt S$) of 300 GeV. Events of the type e + p → ℓ + X with a final—state lepton of high transverse momentum, ℓ = μ or τ, were sought. No evidence was found for lepton flavor violation in the combined 1993 and 1994 data samples, for which the integrated luminosities were 0.84 pb{−1}for e{∼p collisions and 2.94 pb{−1} for e+p collisions. Limits on coupling vs. mass are provided for leptoquarks and R—parity violating squarks. For flavor violating couplings of electromagnetic strength, we set 95% confidence level lower limits on leptoquark masses between 207 GeV and 272 GeV, depending on the leptoquark species and final—state lepton. For leptoquark masses larger than 300 GeV, limits on flavor—changing couplings are determined, many of which supersede prior limits from rare decay processes.

Abstract:

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of x and Q² using the ZEUS detector. The evolution of the scaled momentum, xp, with Q², in the range 10 to 1280 GeV², has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of Q². © 1997 Elsevier Science B.V.