Excitation of High-Energy Protons into Low-Mass States inp−dInteractions

Abstract

We have measured p-d inelastic scattering at small momentum transfer by detecting the slow-recoil deuterons from a deuteri^m-gas-jet target. The coherent diffraction dissociation of protons on deuterons was sl^udied in the region 0.03 <\t\ < 0.07 (GeV/c) 2 , IA<M X 2 < 4 GeV 2 , and for energies from 50 to 275 GeV. In this region, the diffractive cross section exhibits structure and is dominated by an enhancement at M x~ 1.9 GeV 2 .In an experiment performed at the Fermi National Accelerator Laboratory we studied the coherent inclusive reactionat small momentum transfer. 1 Here we report results in the range m/<M JC 2 <4 GeV 2 which covers several of the known resonant states of the proton. Data were obtained at incident energies of 50, 180, and 275 GeV. Excitation to states of higher mass is reported in the following Letter. 2 The target consisted of a deuterium gas jet 3 placed in the internal beam of the accelerator. The slow-recoil deuterons were detected by stacks of two silicon solid-state detectors (surface barrier) of thickness typically 200 /xm for the front and 1500 \±m for the rear detector. Only recoils stopping in the rear detector were accepted, and deuterons were unambiguously identified by the energy deposited in each detector. This technique limits the four-momentum transfer that could be measured to the range 4 0.03^ \t\ % 0.07 (GeV/c) 2 . The detectors were mounted near 90° with respect to the beam direction on a movable carriage at a distance of 2.5 m from the target and each stack subtended a solid angle AO ~ 16x 10" 6 sr.The detection technique of slow recoils from high-energy collisions has been previously used for the measurement oip-p elastic 5 and inelastic 6 scattering as well as for p-d elastic scattering. 7

Measurement ofp¯psingle diffraction dissociation at √s=546 and 1800 GeV

“…V I E ) . 16.98 GeV-2 at the two energies, whereas at lower (fixed target) energies the low mass diffractive slopes were found to be larger than the elastic ones [15,16].…”

Diffraction of Hadronic Waves

“…Proton-diffraction dissociation on deuterons has been recently studied in a very elegan� experiment by the Fermilab-Dubna-Rockefeller-Rochester collaboration working on the circulating proton beam of the 400 GeY/c Fermilab synchrotron (44,45). The technique, using a gas jet of hydrogen (or deuterium) as a target for protons circulating in the machine during the acceleration cycle, has been dis cussed in detail by Melissinos & Olsen (46).…”

“…For the other nonexotic elastic channels the energy should be even higher. Equation 44 has often been used the other way around, i.e. to extract the inelastic overlap integral from the knowledge off(t).…”

“…Proton-diffraction dissociation ondeuteronsat small momentum transfers(44)(45)(46). (A) Differential cross sections plotted versus t ' = t -lonln for various masses M of the produced system.…”

Diffractive Interaction and Scaling Violation in pp-pizero Interaction and GeV Excess in Galactic Diffuse Gamma-Ray Spectrum of EGRET

“…A class of inelastic interaction where the projectile proton and/or the target proton transition to excited states (discrete nucleon resonances and conituum) became known by early 1970's (Alberi & Goggi 1981). This new class of interaction, the diffractive interaction, has been found to grow in cross-section with the incident proton energy (Albrow et al 1974a(Albrow et al ,b, 1976Akimov et al 1975aAkimov et al ,b, 1976. When only one proton transitions to an excited state, the process is called the single diffractive interaction: otherwise the double diffractive interaction.…”