Study of deep inelastic inclusive and diffractive scattering with the ZEUS forward plug calorimeter
Nuclear Physics B 713:1-3 (2005) 3-80
Abstract:
Deep inelastic scattering and its diffractive component, ep → e′ γ* p → e′ X N, have been studied at HERA with the ZEUS detector using an integrated luminosity of 4.2 pb-1. The measurement covers a wide range in the γ* p c.m. energy W (37-245 GeV), photon virtuality Q2 (2.2-80 GeV2) and mass MX (0.28-35 GeV). The diffractive cross section for MX > 2 GeV rises strongly with W; the rise is steeper with increasing Q2. The latter observation excludes the description of diffractive deep inelastic scattering in terms of the exchange of a single pomeron. The ratio of diffractive to total cross section is constant as a function of W, in contradiction to the expectation of Regge phenomenology combined with a naive extension of the optical theorem to γ* p scattering. Above MX of 8 GeV, the ratio is flat with Q2, indicating a leading-twist behaviour of the diffractive cross section. The data are also presented in terms of the diffractive structure function, F2D(3)(β, xℙ, Q2), of the proton. For fixed β, the Q2 dependence of xℙF2D(3) changes with xℙ in violation of Regge factorisation. For fixed xℙ, xℙ F2D(3) rises as β → 0, the rise accelerating with increasing Q2. These positive scaling violations suggest substantial contributions of perturbative effects in the diffractive DIS cross section. © 2005 Elsevier B.V. All rights reserved.Search for pentaquarks decaying to Ξπ in deep inelastic scattering at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 610:3-4 (2005) 212-224
Abstract:
A search for pentaquarks decaying to Ξ-π- (Ξ-π+) and corresponding antiparticles has been performed with the ZEUS detector at HERA. The data sample consists of deep inelastic ep scattering events at centre-of-mass energies of 300 and 318 GeV, and corresponds to 121 pb -1 of integrated luminosity. A clear signal for Ξ0(1530) →Ξ-π+ was observed. However, no signal for any new baryonic state was observed at higher masses in either the Ξ-π- or Ξ-π+ channels. The searches in the antiparticle channels were also negative. Upper limits on the ratio of a possible Ξ3/2 - (Ξ3/20) signal to the Ξ0(1530) signal were set in the mass range 1650-2350 MeV. © 2005 Elsevier B.V. All rights reserved.Study of the pion trajectory in the photoproduction of leading neutrons at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 610:3-4 (2005) 199-211
Abstract:
Energetic neutrons produced in ep collisions at HERA have been studied with the ZEUS detector in the photoproduction regime at a mean photon-proton center-of-mass energy of 220 GeV. The neutrons carry a large fraction 0.64A measurement of the τ lifetime
The European Physical Journal C 39:3 (2005) 331-337
Abstract:
We have reconstructed 695 three-track τ decay vertices using a high resolution drift chamber close to the interaction point. From the distribution of decay lengths we measure the lifetime to be (3.06 ±0.20±0.14)×10-13 s. Using this result we find that the ratio of charged weak coupling constant for the τ to that of the μ, G τ/G μ=0.967±0.040 consistent with the concept of lepton universality. © 1988 Springer-Verlag.Detector concepts
LCWS 2005 - 2005 International Linear Collider Workshop (2005)