Measurements of the cross section for exclusive virtual-photoproduction of ρ mesons from hydrogen are reported. The data were collected by the HERMES experiment using 27.5 GeV positrons incident on a hydrogen gas target in the HERA storage ring. The invariant mass W of the photon-nucleon system ranges from 4.0 to 6.0 GeV, while the negative squared four-momentum Q of the virtual photon varies f...

0168-583X/$ see front matter 2010 Elsevier B.V. doi:10.1016/j.nimb.2010.12.035 ⇑ Corresponding author. E-mail address: [email protected] (H. Yan). We report measurements of the energy dependence of the total neutron scattering cross-section of CH4 both in bulk and confined in aerogel glass for neutron energies between 0:3 and 200 meV. Solid CH4 in phase II is an effective slow neutron moderat...

We point out that high-mass thresholds in the evolution of the strong-interaction coupling parameter s , due to gluinos, squarks and possible new heavy quarks, could introduce appreciable corrections to the transverse momentum dependence of jet production at the Tevatron. If the new thresholds were near scale = 200 GeV, then within the limits of asymptotic freedom they could introduce up to 11%...

We analyse power corrections to longitudinal and transverse fragmentation processes in ee annihilation, based on the assumption of ultraviolet dominance of power corrections. Under this assumption, we determine the dependence of power corrections on the scaling variable x from the infrared renormalon asymptotics of leading power coefficient functions. Our results suggest that the longitudinal a...

We present new predictions for the total cross section of squark pair-production at Tevatron and LHC through next-to-next-to-leading order within the Minimal Supersymmetric Standard Model. The results are based on the numerically dominant soft corrections. They are exact in all logarithmically enhanced terms near threshold, include the Coulomb corrections at two loops and exact scale dependence...

We study the production of W bosons at large transverse momentum in pp collisions at the Large Hadron Collider (LHC). We calculate the complete next-to-leading order (NLO) corrections to the differential cross section. We find that the NLO corrections provide a large increase to the cross section but, surprisingly, do not reduce the scale dependence relative to leading order (LO). We also calcu...

We present results for the pp → ppω reaction studied by considering two different scenarios: with and without the inclusion of nucleon resonance excitations. The recently measured angular distribution by the COSY-TOF Collaboration at an excess energy of Q = 173 MeV and the energy dependence of the total cross section data for π−p → ωn are used to calibrate the model parameters. The inclusion of...

A phenomenological calculation from threshold to 800 MeV of the initial proton beam energy is presented to describe recent data on the reaction pp → (pp)S−waveπ with a low energy cut on the final state diproton excitation energy. A strong forward dip is obtained in the differential cross section as in the data from COSY at 800 MeV, although the absolute value of the forward cross section is too...

We study the factorization scheme dependence of the next-to-leading order inclusive one jet cross section dσ/dET . The scheme is varied parametrically along the direction that transforms the MS scheme to the DIS scheme: we introduce a parameter λ such that λ = 0 is MS and λ = 1 is DIS. The factorization scale μ is also varied. We observe a change of ±9% in the cross section for ET = 50 GeV when...

In this paper we consider the production of top quark pairs close to threshold and compute the dependence on the Higgs boson mass to order αα s. This requires the evaluation of the matching coefficient of the vector current to two-loop level and the inclusion of Higgs mass dependent operators in the non-relativistic effective theory. For Higgs boson masses below 200 GeV moderate contributions t...