Direct reconstruction of pp elastic scattering amplitudes from experimental data between 0.83 and 2.7 GeV

Abstract

2014 La reconstruction directe des amplitudes de diffusion pp élastique est effectuée à partir des données expérimentales entre 0,83 et 2,7 GeV. La reconstruction utilise des ensembles complets d'observables dépendant du spin, mesurés lors du programme expérimental nucléonnucléon auprès de Saturne II. Les amplitudes invariantes a, b, c, d et e ont été déduites par un lissage des données expérimentales utilisant la méthode des moindres carrés. Une recherche de solutions à partir de valeurs initiales aléatoires a été effectuée pour déterminer différents ensembles possibles d'amplitudes. Les valeurs absolues des amplitudes ont le même comportement à toutes les énergies et pour toutes les solutions. Les phases présentent des ambiguités discrètes en particulier aux plus hautes énergies. Une des solutions à 2,1 GeV serait compatible avec l'existence d'une résonance dibaryonique ayant une masse proche de 2,73 GeV et une demilargeur à mi-hauteur inférieure à 50 MeV.

New results in nucleon-nucleon scattering at intermediate energies

“…Several different spin observables and reactions suggest energy dependent structure near fi = 2.7 GeV or Tlab N 2100 MeV in pp elastic scattering; see between 1800, 2100, and 2400 MeV was observed in a model independent amplitude reconstruction [17]. Additional data were collected at the first two beam energies to clarify these results.…”

“…7. For example, the pp total cross section data indicate a bump [51], polarization measurements at the 4momentum transfer squared u=O in the pp -+ .Ird reaction exhibit large changes [62,63], and the Saclay pp amplitude determinations [17] show a sizeable variation at Tlab = 2100 MeV, compared to 1800 and 2400 MeV. from Saclay 164,651 and the ZGS [66] are shown in Fig.…”

“…Thus, if a siiiglet wave becomes quite strong or resonates, A,,,, would decrease. At this time it is unclear whether the changes seen in the direct amplitude reconstruction [17] or in the polarization for pp + 7rd [62,63] are related to the behavior of spin singlet wave(s). However, an increase in the strength of such waves at 8 , = 0" would appear as a peak in A a~( p p ) , as is suggested by the data in [67,68].…”

“…Two recent runs at Saclay by the N-N collaboration were devoted to rechecking the earlier results in [69] and to extending them in energy. The runs in November and December, 1993 measured a variety of two and three spin observables at Tlab = 1800 and 2100 MeV to clarify the behavior of the pp amplitudes reported earlier in [17]. Included were new data for P and CNN at these energies and at 1850 and 2040 MeV.…”

The calculation of the differential cross section of hadron elastic scattering by transferred four-momentum within the perturbation theory

“…В експериментi справдi спостерiгався зростаючий внесок у диференцiальний перерiз [41][42][43]. Проте, на основi цих експериментiв неможливо стверджувати, що цей внесок пов'язаний саме зi змiною сумарної спiральностi.…”