Evidence for coherent effects in large-angle hadron-hadron scattering

Abstract

Marc h 1974 •. sponsor ed by the United States Governmen t. Neither NOTICE This report was prepared as an account of work ' their contractor s, subcontrac tors, or their employee s, the United States nor the United States Atomic Energy Commissi on, nor any of their employee s, nor any of 2 makes any warranty, express or implied, or assumes any ' legal liability or responsib ility for the accuracy, completeness or usefulnes s of any informati on, apparatu s, I product or process disclosed, or represents that its use would not infringe privately owned rights.

Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1 to 5.5 GeV

“…The hadron helicity conservation rule [11], another outcome of the same short-distance pQCD framework, does not agree with data in the same energy and momentum transfer region [12,13]. There are a few anomalies beyond the constituent counting rule in the extensively studied pp scattering process [14][15][16]. Recently, the parton orbital angular momentum has been found to play a non-negligible role in the exclusive reactions, which may explain hadron helicity nonconservation and other polarization measurements [17,18].…”

Hard photo-disintegration of proton pairs in ³He nuclei

“…The pp elastic cross sections are globally consistent over many orders of magnitude with this power law [38,39]. However, it was already noted in 1974 [3] that a more detailed examination of the data indicated significant deviations from scaling. The deviations are known as "oscillations" and were interpreted as resulting from interference between the pQCD amplitude and an additional nonperturbative component.…”

“…In particular, we propose comparative measurements of pp and pn photodisintegration of 3 He at large center of mass angles, with identification of the third low-momentum nucleon as a spectator to the hard reaction. Within this setup we propose to carry out: 2.…”

“…The possibility that the final-state high-p T proton pair is formed due to the hard interaction of the two outgoing protons should produce oscillations in the energy dependence of the invariant cross section, as observed in the pp cross section [3]. The quark counting rule predicts dσ dt ∼ s −10 for high-energy, large-angle pp → pp elastic scattering.…”

“…4.1. The photodisintegration of 3 He has also been measured with the Hall B/CLAS detector [64] at Jefferson Lab, using tagged photons of 0.35 to 1.55 GeV [62]. The large acceptance of the spectrometer allowed detection of the two outgoing protons over a wide range of momentum and angles.…”