M. Medinnis

Production of jets and single particles at high p⊥ in 200 GeV hadron-beryllium collisions

Abstract We present results from an experiment studying the production of single particles and jets (groups of particles) with high p ⊥ (transverse momentum) in 200 GeV/ c interactions on a beryllium target. We give a detailed discussion of the ambiguities in the jet definition. The jet and single-particle cross sections have a similar shape but the jet cross section is over two orders of magnitude larger. The events show evidence for the coplanar structure suggested by constituent models, and the momentum distributions of charged particles give strong support to a simple quark-quark scattering model.

Measurements of single diffraction at √s = 630 GeV; Evidence for a non-linear α(t) of the pomeron

Abstract We report measurements of the inclusive differential cross section for the single-diffractive reactions p i + p − → p ƒ + X and p + p − i → X + p − ƒ at √s = 630 GeV , in the momentum transfer range 0.8 0.90. Based on the assumption of factorization, several new features of the pomeron flux factor are determined from simultaneous fits to our UA8 data and lower energy data from the CHLM collaboration at the CERN Intersecting Storage Rings. Prominent among these is that the effective pomeron Regge trajectory requires a term quadratic in τ, with coefficient α″ = 0.079 ± 0.012 GeV−4. We also show that the data require a pomeron-proton cross section that first decreases with increasing diffractive mass (corresponding to the PPR term in the triple-Regge expansion) and then increases at larger mass (the PPP term), similar to real particle total cross sections. We measure the product Kσ0 = 0.72 ± 0.10 mb GeV−2, where K is the normalization constant of the pomeron flux factor in the proton and σ0 is the scale constant in the pomeron-proton total cross section. Finally, we report the occurrence of “beam jets” in the pomeron direction in the rest frame of the diffractive system.

Structure of events in 200 GeV interactions on hydrogen and aluminum targets in both soft and hard collisions

Abstract The qualitative predictions of quantum chromodynamics for high-energy hadron-nucleus scattering are expounded. Inclusive particle distributions from hadron interactions on proton and aluminum targets are compared to the theoretical expectations for both low and high transverse momentum ( p ⊥ ) scattering. In the latter case, we present data on the nuclear effects in the fragmentation of both the beam and scattered partons. At low p ⊥ , we show evidence for short-range correlations between the final particles produced in hadron-aluminum collisions.

A study of inclusive Double–

We report measurements of the inclusive reaction, p pbar -> p X pbar, in events where either or both the beam-like final-state baryons were detected in Roman-pot spectrometers and the central system was detected in the UA2 calorimeter. A Double-Pomeron-Exchange (DPE) analysis of these data and single diffractive data from the same experiment demonstrates that, for central masses of a few GeV, the extracted Pomeron-Pomeron total cross section exhibits an enhancement which exceeds factorization expectations by an order-of-magnitude. This may be a signature for glueball production. The enhancement is shown to be independent of uncertainties connected with possible non-universality of the Pomeron flux factor. Based on our analysis, we present DPE cross section predictions, for unit (1 mb) Pomeron-Pomeron total cross section, at the Tevatron, LHC and the 920 GeV fixed-target experiment, HERA-B.Abstract. We report measurements of the inclusive reaction,

{\cal P}

p bar p to p X bar p

omeron–Exchange in

, in events where either or both the beam-like final-state baryons were detected in Roman-pot spectrometers and the central system was detected in the UA2 calorimeter. A Double-

p \bar{p}{\rightarrow} p X \bar{p}

{cal P}

at

omeron-Exchange (DPE) analysis of these data and single diffractive data from the same experiment demonstrates that, for central masses of a few GeV, the extracted

\sqrt{s} = 630

{cal P}

GeV

omeron-