A QCD analysis of the prompt photon away-side jet cross section measured in pp collisions

A QCD analysis of the recently measured double inclusive cross section for pp → γ + away-side jet + X at √s = 63 GeV is presented. It is pointed out that these data are indeed compatible with a gluon distribution in the proton, which is (i) determined from deep inelastic lepton-proton scattering, and (ii) which is required to describe all available data for pN → γX.     

Transverse single spin asymmetry measurements at STAR

Transverse single spin asymmetries A _N are expected to be sensitive to par-ton polarization and orbital angular momentum contributions to the nucleon spin. Significantly large A _N has been observed in different collision systems such as semi-inclusive deep inelastic scattering (SIDIS) and polarized proton-proton (pp) collisions, indicating a dominant contribution of partonic interactions in the non-perturbative regime. Therefore it’s critical to measure A _N in various channels of polarized pp collisions in order to complement SIDIS data and to constrain theoretical models. We report STAR asymmetry measurements on mid-rapidity hadron-jet and di-hadron correlations at √s = 200 GeV and forward rapidity inclusive hadron production at √s = 500 GeV polarized pp collisions.     

A study of the charge-exchange reaction pp → nΔ++(1232) at ISR energies

We report on a study of the charge-exchange reaction pp → nΔ⁺⁺(1232) at the CERN intersecting storage rings (ISR) in the energy range √s = 23 to 53 GeV. From our analysis of the energy dependence of the total cross-section, of the differential cross-section dσ/dt and of the decay angular distributions we find evidence that pion exchange is dominant up to √s = 23 GeV and that (?+A₂) exchange dominates the reaction for √s ? 30 GeV, as described by simple Regge-pole models.     

Double pomeron exchange in the reaction ifpp → ppπ+π− at ISR energies

Using the split field magnet (SFM) of the CERN ISR, we have investigated the main features of the reaction pp → ppπ⁺π^? in the kinematical region where double pomeron exchange (DPE) is supposed to play an important rôle. Using kinematically fitted events at the five standard ISR energies from √s = 23.4 GeV to √s = 63.4 GeV, we have studied different data subsamples as a means of distinguishing DPE from the tail of single diffraction (SD). Our results are compatible with a significant DPE contribution; in particular there is no correlation between the two protons and the s- and t-dependences follow the expected behaviour.     

K1±(890) production in 205 GeV/c pp interactions

Using data obtained from an exposure of the Fermilab 30-inch hydrogen bubble chamber to a 205 GeVc proton beam, we have studied K⁰π^± correlations and the inclusive production of K¹(890). Based on an analysis of the K_S⁰π^± effective mass distribution, we find a 95% confidence level upper limit of 0.22 K^1±(890) per inelastic event. Possible systematic effects in the experimental determination of the ?⁰ production rate due to the Kπ correlation are discussed. Our result for K¹ production at √s = 19.7 GeV is incompatible with that obtained in a recent ISR experiment at √s = 53 GeV.     

Mechanism of elastic and inelastic proton scattering on a 15C nucleus in diffraction theory

The amplitudes for elastic and inelastic proton scattering on the neutron-rich nucleus ¹⁵C (to its J ^?? = 5/2⁺ level in the latter case) in inverse kinematics were calculated within Glauber diffraction theory. First- and second-order terms were taken into account in the multiple-scattering operator. The ¹⁵C wave function in the multiparticle shell model was used. This made it possible to calculate not only respective differential cross sections but also the contribution of proton scattering on nucleons occurring in different shells. The differential cross sections for elastic and inelastic scattering were calculated at the energies of 0.2, 0.6, and 1 GeV per nucleon.     

Analysis of elastic and inelastic hadron scattering on 6,7Li nuclei within diffraction theory

Within Glauber-Sitenko multiple-scattering theory, the differential cross sections for elastic and inelastic proton, positive-pion, and positive-kaon scattering on ^6,7Li nuclei are calculated at incident-hadron energies ranging between 0.143 and 1.0 GeV. The ⁶Li and ⁷Li wave functions are taken in, respectively, the α2N and the αt clustermodel. The resulting cross sections are investigated as functions of the scattered-particle energy, parameters of the model wave functions, and various scattering multiplicities. It is concluded that a partial filling of the diffraction minimum in the cross section is due to the D-wave contribution to the wave function for the ⁶Li target nucleus.     

Production of low transverse energy clusters in pp collisions at √s=0.2–0.9 TeV and their interpretation in terms of QCD jets

The production of transverse energy clusters in minimum bias proton-antiproton collisions at the CERN SPS Collider is studied with the UA1 detector over a new range of centre of mass energies (√s = 0.2−0.9 TeV). This study is intended to investigate how low in transverse momentum perturbative QCD is able to describe the dynamics of hadron collisions. We observe that clusters with transverse energy in excess of a few GeV exhibit properties in agreement with QCD expectations for parton scattering, supporting their interpretation in terms of jet production. We find that the jet-event rate represents a sizeable fraction of the inelastic rate and is increasing with √s over the measured energy range.     

Gluon shadowing and unitarity effects

New data from HERA experiment on deep inelastic scattering have been used to parametrize nucleon and Pomeron structure functions. Within the Gribov theory, the parameterizations were employed to calculate gluon shadowing for various heavy ions. The latter was compared with predictions from other models. Calculations of multiplicity reduction due to gluon shadowing for d+Au collisions at forward rapidities at √s _NN =200 GeV are in good agreement with BRAHMS data on the nuclear modification factor.     

Maximal electromagnetic contribution to pp inelastic cross sections at ISR energies

The maximal electromagnetix contribution to the pp inelastic cross section is estimated. Although this contribution is insufficient in itself to explain all of the recently observed rise at ISR energies if the purely strong cross section is asymptotically constant, it could amount to as much as approximately 3 mb at √s ≈ 53 GeV if the purely strong cross section rises with energy through the range of present accelerator energies like (ln s)² or slower.     

Glauber Monte Carlo program for NICA/MPD and CBM experiments

A program code widely applied at RHIC and LHC for calculations of geometrical properties of nucleus-nucleus interactions is adapted for NICA/MPD and CBM energies. A parameterization of pp elastic scattering amplitude earlier proposed by the authors and valid at √s ≥ 3 GeV is used for a setting of the nucleon-nucleon collision profile. An approach well known in physics of low and intermediate energies is used for a determination of nuclear parameters. The code is enlarged by a possibility to account for the Gribov inelastic screening.     

Return of the volcano: PHENIX azimuthal correlations 62.4 GeV Au+Au

As in previous analyses at √s _NN =200 GeV., correlations in azimuthal angles between inclusive charge particles at intermediate transverse momentum (p _T=1.0?4.0) GeV are studied at √s _NN =62.4 GeV. The di-jet correlations reveal similar modification as in 200 GeV. Specifically large modification, including the “volcano” or “cone” structure, persists in the awayside correlation.     

Collins and sivers effects in p↑p → jet πX: Universality and process dependence

In this paper we briefly review the transverse momentum dependent generalized parton model and its application to the study of azimuthal asymmetries in the distribution of leading hadrons (mainly pions) inside large transverse momentum jets inclusively produced in polarized proton-proton collisions. We put particular emphasis on the phenomenological interest of these observables, in combination with similar asymmetries measured in semi-inclusive deeply inelastic scattering, Drell-Yan processes and e ⁺ e ^? collisions, for the study of the universality properties of the transverse momentum dependent parton distribution and fragmentation functions. We present results for RHIC kinematics at center-of-mass energies √s = 200 and 500 GeV, for central and mainly forward jet rapidities, in particular for the Sivers distribution and the Collins fragmentation function, that are believed to be responsible for many of the largest asymmetries measured in the last years. We also briefly discuss the case of inclusive jet production and recent phenomenological applications of other theoretical approaches, like the colour gauge invariant generalized parton model and the collinear twist-three approach, aiming at clarifying the issues of the universality and process dependence of transverse momentum dependent functions.     

Study of multihadron events with isolated leptons in e+e− annihilation at 50⩽sles;55 GeV

We have studied inclusive lepton production in e⁺e⁻ annihilations into multihadrons in the energy range between √s=50 and 55 GeV using the VENUS detector at TRISTAN, KEK. Though MARK-J and JADE groups at PETRA found an excess of isolated muon events at √s⩾46.3 GeV, we have not observed such an anomaly in muon nor in electron production. The observed rates of isolated leptons are consistent with the production and decay of five known quarks.     

An analysis of prompt lepton emission at ISR energies

The e/π ratios at low p_T observed in pp collisions at √s = 53 GeV are analysed as a function of R, the ratio of the total number of electrons integrated over electron energies to the total number of pions integrated over pion energies. It is found that R is independent of the decay kinematics and very insensitive to the production dynamics of the parent particles. The total parent cross section times the branching ratio into an electron is calculated, and the result is interpreted as either the total inclusive cross section for production of charmed particles, or as the total cross section for single photons in pp collisions.     

Large-angle inclusive production of charged pions at the CERN ISR with transverse moment a less than 1.0 GeV/c

The inclusive production of π^± in proton-proton collisons has been measured for the transverse momentum range 0.15 to 1.0 GeV/c over an angular range of 29° to 89° in the centre-of-mass system and for centre-of-mass energies √_s = 30.6 and 52.8 GeV. For each energy the invariant cross-section foe fixed transverse momentum was found to increase by about 15% as the centre-of-mass rapidity decreases from 1 to 0, i.e. the “central plateau” has not yet been reached.     

Inclusive charged particle cross sections in full phase space from proton proton interactions at ISR energies

Measurements are presented of inclusive charged particle production in proton-proton collisions at √s=31, 44 and 62 GeV at the CERN ISR. The large acceptance of the Split Field Magnet detector allows a single experimental setup to cover almost the full longitudinal phase space up to a transverse momentum of 3 GeV/c.     

Event structure investigation of AuAu interactions from HIJING model using fractal dimensions

This work presents an implementation of fractal geometry methods in the study of event structure for AuAu interactions at collision energies √s _NN = 9.2, 62 and 200 GeV for different interaction dynamics. The events are generated by using the HIJING model. It is shown, that the fractal dimension of events in phase space projections rapidity-transverse momentum (y - p_t) and azimuthal angle-transverse momentum (φ - p_t) are sensitive to the interaction dynamics.     

Large t elastic proton-proton scattering at √s = 53 GeV

New experimental results are presented on proton-proton elastic scattering in the range of momentum transfer 0.8GeV² < ?t < 9 GeV² at a centre-of-mass energy of √s = 53 GeV. The data are obtained sing the Split-Field- Magnet Detector at the CERN Intersecting Storage Rings. The cross section has well-known minimum at ?t = (1.34±0.02) GeV² but no further minimum or change of slope is observed between 2 and 6.5 GeV².     

Evidence for a change of slope in large-t elastic proton-proton scattering at s=53 GeV

New experimental results are presented on proton-proton elastic scattering in the range of momentum transfer 4 GeV² < ?t < 10 GeV² at the centre-of-mass energy of √s = 53 GeV. The data have been obtained using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. We observe another change of slope of the differential cross section near ?t=6.5 GeV².