ϒ Production in pp¯ Collisions at s=1.8 TeV
Physical Review Letters American Physical Society (APS) 75:24 (1995) 4358-4363
A search for excited fermions in electron-proton collisions at HERA
Zeitschrift für Physik C Particles and Fields 65:4 (1995) 627-647
Abstract:
A search for excited states of the standard model fermions was performed using the ZEUS detector at the HERA electron-proton collider, operating at a centre of mass energy of 296 GeV. In a sample corresponding to an integrated luminosity of 0.55 pb-1, no evidence was found for any resonant state decaying into final states composed of a fermion and a gauge boson. Limits on the coupling strength times branching ratio of excited fermions are presented for masses between 50 GeV and 250 GeV, extending previous search regions significantly. © 1995 Springer-Verlag.Measurement of elastic $\rho^0$ photoproduction at HERA
Zeitschrift f�r Physik C Particles and Fields Springer Science and Business Media LLC 69:1 (1995) 39-54
Measurement of elastic ρ 0 photoproduction at HERA
Zeitschrift für Physik C: Particles and Fields 69:1 (1995) 39-54
Abstract:
Elastic ρ 0 photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from ep interactions were used to measure the reaction γp→ρ 0 p(ρ 0)→π +π-) at photon-proton centre-of-mass energies between 60 and 80 GeV and |t|<0.5 GeV2, where t is the square of the four-momentum transferred at the proton vertex. The differential cross section dσ/d M ππ where M ππ is the invariant mass of the two pions, and the integrated cross section, σγp→ρ{variant}0ρ{variant}, are presented; the latter was measured to be 14.7±0.4 (stat.) ±2.4 (syst.)μb. The differential cross section dσ/dt has an approximately exponential shape; a fit of the type A t ′ exp(-b t ′ |t|+c t ′ t 2) yields a t-slope b t ′ =9.9±1.2 (stat.) ±1.4 (syst.) GeV-2. The results, when compared to low energy data, show a weak energy dependence of both σγp→ρ{variant}0p and of the t-slope. The ρ 0 is produced predominantly with transverse polarisation, demostrating that s-channel helicity conservation holds at these energies. © 1996 Springer-Verlag.Measurement of the diffractive structure function in deep inelastic scattering at HERA
Zeitschrift für Physik C Particles and Fields 68:4 (1995) 569-584