111268724
A TPC for large solid angle relativistic ion experiments
A TPC (time projection chamber) detector system has been developed to function in the very-high-multiplicity environment of relativistic-heavy-ion experiments. A TPC was chosen because it directly gives three-dimensional points on the tracks, which is a very significant help for track-finding. Of prime importance is a combination of high efficiency, low noise, and two track resolution capability. A significant development is a system of hybridized, high-sensitivity, on-chamber digitizing electronics. A description of the TPC modules, the digitizing electronics, and test results is given. >
120544624
Triggering on high-transverse-momentum jets
We compare the characteristics of events selected by ''global'' and ''two-high'' triggers in large-transverse-energy hadron-hadron collisions. Using a QCD-based Monte Carlo model of Fox and collaborators, we find that the former is effectively a high-multiplicity trigger, the latter a high-planarity trigger favoring unusually clean jet events. Predictions of the model for both triggers are in good qualitative agreement with recent data.
119722876
Measurement of the dijet cross section in 400-GeV pp collisions
The invariant cross section for production of jet pairs in 400-GeV/c pp interactions has been measured as a function of p{tau} in the p{tau} range 4 to 9 GeV/c. The results are in good agreement with predictions of perturbative QCD models. 20 refs., 3 figs., 1 tab.
120365910
Modular TPCs for relativistic heavy-ion experiments☆
Abstract A description is given of a TPC system that operates in a relativistic heavy-ion beam and yields good track reconstruction efficiency in very-high-multiplicity events. The mechanical construction of the chamber is discussed. A set of custom hybrid circuits are used to build a very compact, cost-effective electronics system mounted directly on the chamber. Results from running in test beams and from preliminary experimental runs are given.
198138883
Experimental information on the pion gluon distribution function
An experiment performed at Fermilab used double-arm calorimeter triggers to study di-jet production by 400 GeV protons and 200 GeVπ− mesons incident on liquid hydrogen. The observed ratio of positive to negative leading particles in the jets was compared forpp andπp production using a tree level parton scattering model. The results are moderately sensitive to the form of the pion gluon distribution function and yieldx g(x)⋍(1−x)2.75±0.40±0.75.
125525593
HADRON JETS IN 400-GeV p p COLLISIONS
121161753
Simple structure of charged neutral correlations
Abstract All available high-energy data agree with the assumption that the charged versus neutral pion multiplicities are described by a binomial distribution. This distribution is obtained in a variety of models. One of these is the Mueller model, supplied with the assumption of the absence of exotic contributions. In contrast to this, a binomial distribution cannot be obtained in any neutral cluster model.
121339748
MOMENTUM TRANSFER DEPENDENCE IN DIFFRACTION DISSOCIATION.
Abstract The mechanism of kinematic coupling between momentum transfers in producing a low mass two particle system with double-peripheral dynamics is studied theoretically and model calculations. A method of data analysis which eliminates the effects of this kinematic reflection is presented. The data of the reaction pp → pnπ + at 19 GeV/ c have been analyzed using this method. It is seen that the high production slope of the low mass ηπ + system observed in this process is not a cosequences of double-peripheral dynamics plus kinematics but must be explicitly present in the invariant matrix element.
123478569
Coherent production on nuclei does not measure total cross sections for unstable particles
We calculate diffractive production in nucleon-nucleus collisions using a parton model. We fit the result by the standard optical-model formula, and obtain estimates of 12--30 mb for the cross section of the diffractively produced system on a nucleon. The actual value of that cross section in the model is 65 mb. Estimates for the total cross section of an unstable hadron which are based on the A dependence of coherent production should therefore not be trusted.
120502863
Hadronic Production with a Drell-Yan Trigger
The ratio of cross sections for producing fast ${\ensuremath{\pi}}^{+}'\mathrm{s}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}'\mathrm{s}$ in association with a massive dilepton should be a strongly varying function of the mass of the pair, reducing at small mass to its value in the absence of a pair. For $\frac{{{M}_{\ensuremath{\mu}\ensuremath{\mu}}}^{2}}{s}g0.1$, the $\frac{{\ensuremath{\pi}}^{+}}{{\ensuremath{\pi}}^{\ensuremath{-}}}$ ratio should fall by a factor of 1.7 in the reactions $p+\overline{p}\ensuremath{\rightarrow}\ensuremath{\pi}+({\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})+X$ and $p+{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\pi}+({\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})+X$, rise by a factor of 2.6 in $p+{\ensuremath{\pi}}^{+}\ensuremath{\rightarrow}\ensuremath{\pi}+({\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})+X$, and fall by about 25% in $p+p\ensuremath{\rightarrow}\ensuremath{\pi}+({\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})+X$.
121736887
Diffraction scattering and the parton structure of hadrons
We apply parton-model concepts to the ''soft'' (small-momentum- transfer) processes which make up the majority of the hadronic total cross section. Diffraction is calculated as the shadow of these soft processes. We obtain an attractive picture of the essential features of total, elastic, and diffractive-inelastic scattering. In particular, the rather large cross section for inelastic diffraction, which is observed experimentally, results from fluctuations in the distribution of the wee partons which initiate interactions. These fluctuations lead to diffractive production by the mechanism of Good and Walker. The observed peripheral character of diffraction as a function of impact parameter, the absence of a forward dip in dsigma/dt dm/sup 2/, the correct integrated cross section, and the correct small-t slope of diffraction all follow naturally in our approach.