Collisional lasers at 41.8 nm in a guided regime
J PHYS IV 127 (2005) 33-37
Simulations of recombination lasing in Ar7+ driven by optical field ionization in a capillary discharge waveguide
Optics Communications 249:4-6 (2005) 501-513
Abstract:
We present calculations of the small-signal gain coefficient, gain length, and output energy of a recombination laser in Ar7+ driven by optical field ionization. Simulations are presented for both 400 and 800 nm pump radiation, and for two targets containing mixtures of argon and hydrogen: a gas cell, and a gas-filled capillary discharge waveguide. Extremely high values for the small-signal gain coefficient are calculated for the 4s-3p transition at 23.2 nm using a pump wavelength of 400 nm for both the gas cell and waveguide. Operation in the waveguide is predicted to greatly increase the XUV laser output owing to a large increase of the gain length. The calculations also show that use of the waveguide allows significant single-pass gain to be achieved even with pump radiation of 800 nm wavelength. © 2005 Elsevier B.V. All rights reserved.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