J.F. Owens

Impact of new neutrino deep inelastic scattering and Drell-Yan data on large-x parton distributions

New data sets have recently become available for neutrino and antineutrino deep inelastic scattering on nuclear targets and for inclusive dimuon production in pp and pd interactions. These data sets are sensitive to different combinations of parton distribution functions in the large-x region and, therefore, provide different constraints when incorporated into global parton distribution function fits. We compare and contrast the effects of these new data on parton distribution fits, with special emphasis on the effects at large x. The effects of the use of nuclear targets in the neutrino and antineutrino data sets are also investigated.

The role of A1 exchange in the reaction π−p → (π+π−n

Abstract Data have recently become available, at 17.2 GeV/ c , which show strong target polarization effects for the reaction π − p → ( π + π − )n. These data require the presence of an exchange with the quantum numbers of the A 1 . A simple model based on π , A 2 , and A 1 Regge pole exchange together with parametrized n = 0 cuts is found to provide an excellent description of both the polarized and unpolarized data. The resulting structure of the A 1 dominated amplitudes is discussed and the results are compared with earlier models which neglected A 1 exchange effects.

The role of absorptive corrections in a triple-Regge analysis of pp → Δ++ + X

The size and nature of absorptive corrections in the triple-Regge region of inclusive reactions are discussed. A triple-Regge model using π, B, ρ and A2 exchanges, both with and without absorption, is presented and compared with the data for pp → Δ++X. Predictions for the x and p⊥2 dependence of the invariant cross section and the Δ++ density matrix elements are given. The effects of absorption in other π exchange dominated reactions are briefly discussed.

Gamma-Jet Tomography of Quark-Gluon Plasma in High-Energy Nuclear Collisions

Abstract Within the next-to-leading order (NLO) perturbative QCD (pQCD) parton model, suppression of away-side hadron spectra associated with a high p T photon due to parton energy loss is shown to provide a complete tomographic picture of the dense matter formed in high-energy heavy-ion collisions at RHIC. Dictated by the shape of the γ -triggered jet spectrum in NLO pQCD, hadron spectra at large z T = p T h / p T γ ≳ 1 are more susceptible to parton energy loss and therefore are dominated by surface emission of γ -triggered jets, whereas small z T hadrons mainly come from fragmentation of jets with reduced energy from volume emission. These lead to different centrality dependence of the hadron suppression in different regions of z T .

Punch-through jets in A + A collisions at RHIC/LHC

High pT single and dihadron production is studied within a NLO pQCD parton model with jet quenching in high energy A + A collisions at RHIC/LHC energy. A simultaneous χ2-fit to both single and dihadron spectra can be achieved within a narrow range of the energy loss parameter. Punch-through jets are found to result in a dihadron suppression factor slightly more sensitive to medium properties than the single hadron suppression factor at RHIC. Such jets at LHC are found to dominate high pT dihadron production and the resulting dihadron spectra are more sensitive to the initial parton distribution functions than the single hadron spectra.

A NLO analysis on fragility of dihadron tomography in high energy AA collisions

The dihadron spectra in high energy AA collisions are studied within the NLO pQCD parton model with jet quenching taken into account. The high pT dihadron spectra are found to be contributed not only by jet pairs close and tangential to the surface of the dense matter, but also by punching-through jets survived at the centre while the single hadron high pT spectra are only dominated by surface emission. Consequently, the suppression factor of such high-pT hadron pairs is found to be more sensitive to the initial gluon density than the single hadron suppression factor.

LHC Data and its Impact on nCTEQ15 PDFs

The LHC heavy ion data for W/Z production can provide new incisive information on the PDFs. This data is sensitive to the heavier quark flavors (strange and charm) in a high energy kinematic region; this can facilitate the determination of PDFs in the small x region where previous data was limited. At present, the flavor separation of the proton PDFs is dependent on DIS data from nuclear targets. Therefore, improved nuclear corrections can also yield enhanced flavor determination of both the proton and nuclear PDFs.

Gamma-jet tomography of high-energy nuclear collisions in NLO pQCD

Within the NLO pQCD partem model study, suppression of away‐side hadron spectra associated with a high pT photon due to parton energy loss is shown to provide more complete tomographic picture of the dense matter formed in high‐energy heavy‐ion collisions. Hadron spectra at large ZTu2009=u2009PTh/pTλ≳ 1 are more susceptible to parton energy loss and therefore are dominated by surface emission of λ‐correlated jets, whereas small ZT hadrons mainly come from fragmentation of jets with reduced energy which is controlled by the volume emission. These lead to different centrality dependence of the hadron suppression in different region of ZT.