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The proposed work is an extension of a program of precise studies of rare pion and muon decays using the PIBETA detector. In the first phase, 1999–2001, the collaboration completed a set of measurements of the π + → π 0 e + ν, π + → e + ν, π + → e + νγ, and µ + → e + ν ¯ νγ decays. Data for all of the decays except π → eνγ (π e2γ) are in excellent agreement(More)
The production of isolated photons in deep-inelastic scattering ep → eγX is measured with the H1 detector at HERA. The measurement is performed in the kinematic range of negative four-momentum transfer squared 4 < Q 2 < 150 GeV 2 and a mass of the hadronic system W X > 50 GeV. The analysis is based on a total integrated luminosity of 227 pb −1. The(More)
We have searched for Theta+(1540) and Xi(--)(1862) pentaquark candidates in proton-induced reactions on C, Ti, and W targets at midrapidity and square root of s = 41.6 GeV. In 2 x 10(8) inelastic events we find no evidence for narrow (sigma approximately 5 MeV) signals in the Theta+ --> pK0(S) and Xi(--) --> Xi- pi- channels; our 95% C.L. upper limits (UL)(More)
Photon-proton (p) interactions with Q 2 < 10 ?2 GeV 2 and deep-inelastic scattering (p) interactions with photon virtualities Q 2 > 5 GeV 2 are studied at the high energy electron-proton collider HERA. The transverse energy ow and relative rates of large rapidity gap events are compared in the two event samples. The observed similarity between p and p(More)
A search for second and third generation scalar and vector leptoquarks produced in ep collisions via the lepton flavour violating processes ep → µX and ep → τ X is performed by the H1 experiment at HERA. The full data sample taken at a centre-of-mass energy √ s = 319 GeV is used for the analysis, corresponding to an integrated luminosity of 245 pb −1 of e +(More)
A thrust analysis of Large-Rapidity-Gap events in deep-inelastic ep collisions is presented , using data taken with the H1 detector at HERA in 1994. The average thrust of the nal states X, which emerge from the dissociation of virtual photons in the range 10 < Q 2 < 100 GeV 2 , grows with hadronic mass M X and implies a dominant 2-jet topology. Thrust is(More)
We have measured the pi+-->e+ nugamma branching ratio over a wide region of phase space, based on a total of 65 460 events acquired using the PIBETA detector. Minimum-chi2 fits to the measured (E(e+), E(gamma) energy distributions result in the weak form factor value of F(A)=0.0119(1) with a fixed value of F(V)=0.0259. An unconstrained fit yields(More)
A search for the lepton flavour violating processes ep → µX and ep → τ X is performed with the H1 experiment at HERA. Final states with a muon or tau and a hadronic jet are searched for in a data sample corresponding to an integrated luminosity of 66.5 pb −1 for e + p collisions and 13.7 pb −1 for e − p collisions at a centre-of-mass energy of 319 GeV. No(More)