Nucleon-Number Dependence of Inclusive Dihadron Production in Proton-Nucleus Collisions at 400 GeV/c

Abstract

PHYSICAL REVIEW LETTERS 16APRIL1979nals was estimated from single-particle inclusive data in which one arm was used as the trigger, and the other (untriggered) arm recorded the relative frequency of Cherenkov signals. 4 The original configuration of the apparatus is described by Bintinger et al. (Ref. 2), and the rearranged configuration (for which one of the Cherenkov counters was relocated behind the magnet) is described in Ditzler et al. (Ref. 2).Several unexpected results have recently raised interest in hadron production on heavy nuclei. The multiplicity of hadron-nucleus collisions grows with nuclear size much less rapidly than a simple cascade model would predict. 1 On the other hand, the inclusive production of high-/> x particles rises as A a with a significantly greater than l. 2 " 4 Theoretical models which attempt to describe this behavior include multiple scattering, nucleon clusters, and decay of high-mass states. 5 We report here the results of an experiment on the A dependence of dihadron production. 6 Only charged particles were detected, and for the purposes of this paper no distinction is made between 7T, K, and/>. The quantum-number correlations observed in lead and beryllium have been reported separately. 7 This experiment was performed at the Fermi National Accelerator Laboratory in a 400-GeV/c proton beam, with a typical intensity of 4x 10 7 sec" 1 . Other results and a detailed description 5 Our kinematic correlation results are reported in D. A. Finley etal., Phys. Rev. Lett. 42, 1031 (1979) (this issue). 6 M. G. Albrowet al. 9 Phys. Lett. 65B, 295 (1976). 7 R. J. Fisk et al. t Phys" Rev. Lett. 40, 984 (1978). 8 The observation that heavier nuclei reduce quantumnumber correlations as well as kinematic correlations (see Finley et al. t Ref. 2) is consistent with an inelastic multiple-scattering process.of the apparatus have been published previously. 8 The apparatus consisted of two identical magnetic spectrometers placed at 100 mrad on opposite sides of the beam. In the proton-nucleon centerof-mass system, each spectrometer was centered at 6 = 110° and subtended about ± 10° in polar angle, and ± 17° in azimuth. The trigger required each hadron to have£ ±^ 1 GeV/c.Measurements of the A dependence were made with a target of nine 1.3-mm lead segments followed by three 6.1-mm beryllium segments, all 3.8 mm wide. Data were taken on both nuclei simultaneously with targets of equal width in order to eliminate uncertainties arising from beam normalization or changes in experimental conditions. The good spatial resolution of the spectrometer drift chambers allowed unambiguous identification of the target element, as shown in Fig. 1. The acceptance of the spectrometer was uniform over the length of the target. The data were corrected for beam attenuation in the tar-We have measured the nucleon-number (A) dependence of hadron-pair production in 400-GeV/c proton-nucleus collisions, using Pb and Be targets. Charged-hadron pairs were observed near rapidity y Ca mr~ -0.4 with Acp s 180°. The A-dependenc...

A dependence of the inclusive production of hadrons with high transverse momenta

“…3 we plot a for h+h~ pairs (without regard to particle type) versus mass, in comparison to data from Ref. 4,Finley et al, 12 and a recent experiment by Abramov et al u All data shown, with the exception of those from Ref. 12, are consistent with a=l for hadron pairs (summed over net p T ).…”

Does a nucleus act like a gluon filter?

“…We take the nucleus to be a ,t A similar behaviour has been observed in the production of hadron pairs [12,13]. ,2 We should mention that one also observes large Valuesof n for a proton trigger.…”

Nuclear rescattering effects in massive dihadron production

“…In the remainder of this Letter, we describe some of those consequences and their implications for the analysis of experimental data. The issues are of particular importance for dihadron data, because there is a large body of published data [8][9][10][11][12] of high statistical accuracy whose interpretation may become clearer when nuclear kr effects are taken into account in the analyses.…”

“…In the remainder of this Letter, we describe some of those consequences and their implications for the analysis of experimental data. The issues are of particular importance for dihadron data, because there is a large body of published data [8-12] of high statistical accuracy whose interpretation may become clearer when nuclear kr effects are taken into account in the analyses.Several experiments [8][9][10][11][12] have measured the A dependence of a differential cross section for the process pA -• dihadrons for proton beams of momenta > 400 GeV/c. The A dependence is usually parametrized as A a , where a > 1 is called an anomalous nuclear enhancement; a < 1 is called shadowing, and a = 1 would be expected for independent hard scattering from each of the nucleons.…”

“…Several experiments [8][9][10][11][12] have measured the A dependence of a differential cross section for the process pA -• dihadrons for proton beams of momenta > 400 GeV/c. The A dependence is usually parametrized as A a , where a > 1 is called an anomalous nuclear enhancement; a < 1 is called shadowing, and a = 1 would be expected for independent hard scattering from each of the nucleons.…”