Ch. Gottfried

Measurements of Elastic Proton Proton Scattering at Large Momentum Transfer at the CERN Intersecting Storage Rings

Abstract Final results of our measurements of elastic proton-proton scattering at the CERN Intersecting Storage Rings (ISR) for c.m. energies √ s from 23 to 63 GeV and momentum transfers | t | from 0.8 to 10 GeV 2 are presented. Absolute differential cross sections have been obtained using the split-field magnet detector facility (SFM) at the five standard energies for integrated luminosities ranging from 0.3 to 4.9 (pb) −1 . The rising total cross section is found to define a scale for diffractive phenomena near the forward peak, including the position of the diffraction minimum near t = −1.4 GeV 2 . The cross section at the minimum is strongly energy dependent, approximately as the ratio of the real to imaginary part of the scattering amplitude in the forward direction. The phase of the scattering amplitude is found to change sign near the minimum. The component of diffraction scattering beyond the second maximum has a much weaker t -dependence than expected in simple eikonal or constituent pictures connecting this region to the forward peak. A further break in slope is observed near t = −6 GeV 2 . There is no evidence for another minimum for t values up to 10 GeV 2 .

Experimental results on large angle elastic pp scattering at the CERN ISR

Abstract New experimental results are presented on proton-proton elastic scattering at centre-of-mass energies s =23 GeV and s =62 GeV . The data are obtained using the Split Field Magnet detector at the CERN Intersecting Storage Rings. The absolute differential cross-sections show an energy-dependent behaviour. The position of the diffraction minimum changes from t=(−1.44±0.02)GeV2 at 23 GeV to (−1.26±0.03)GeV2 at 62 GeV. The cross-section at the second maximum is increasing with s . The connection of these observations with the hypothesis of “geometrical scaling” is discussed.

Rapidity correlations in inclusive two-particle production at storage ring energies

Abstract Inclusive two-particle production in the reaction pp → γ + ch + (anything) has been measured at the CERN ISR for four energies ( ✓s = 23,30.5,45, and 53 GeV ) at two production angles of the charged particles (ch) and the eight production angles of the γ-rays. The rapidity correlation of the two particles is weak and of short range. The peak correlation is σ inel ( d 2 σ γ ch d σ γ d σ ch ) − 1 = 0.62 ± 0.08 , the correlation range 〈yγ − ych〉 = 1.17 ± 0.05, independently of s. The φ correlation extends over a wide gap in rapidity; its strength is increasing with increasing transverse momentum.

Experimental Results on Diffractive One Pion Production at the CERN ISR

New experimental results are reported on diffractive dissociation of protons into (nπ+) in proton-proton collisions at a centre-of-mass energy of s = 45 GeV. The data were obtained using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. We have searched for resonance contributions and found peaks at mass values of 1.5 GeV, 1.65 GeV, and 2.1 GeV. A dip in dσdt is observed at low t and low mass; it is most pronounced for events with neutrons emitted at 90° in the Gottfried-Jackson frame. The correlation between mass and slope depends strongly on θJ. The cross section of the channel pp → pnπ+ is 400 ± 110 μb at s = 45 GeV, giving an energy dependence of s−0.30±0.07 for isospin exchange zero in this channel.

Some features of large multiwire proportional chambers

Abstract This article describes multiwire proportional chambers of about 150 cm × 40 cm designed to operate in a large magnet at the CERN Intersecting Storage Rings. Five chambers with three different orientations of the sensitive wires were built in a modular construction. Measurements on efficiency, noise, and time- and space-resolution are reported.

Large t elastic proton-proton scattering at √s = 53 GeV

New experimental results are presented on proton-proton elastic scattering in the range of momentum transfer 0.8GeV2 < −t < 9 GeV2 at a centre-of-mass energy of √s = 53 GeV. The data are obtained sing the Split-Field- Magnet Detector at the CERN Intersecting Storage Rings. The cross section has well-known minimum at −t = (1.34±0.02) GeV2 but no further minimum or change of slope is observed between 2 and 6.5 GeV2.

Evidence for a change of slope in large

Abstract New experimental results are presented on proton-proton elastic scattering in the range of momentum transfer 4 GeV 2 t 2 at the centre-of-mass energy of √ s = 53 GeV. The data have been obtained using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. We observe another change of slope of the differential cross section near − t =6.5 GeV 2 .

-t

Abstract A multiparticle spectrometer at the CERN Intersecting Storage Rings is equipped with a multiwire proportional chamber detector. In this paper we describe trigger, data acquisition, and monitor system of the detector.

elastic proton-proton scattering at

Abstract Observation of 16 μ + μ − pairs of invariant mass greater than 2.7 GeV/ c 2 in the reaction pp → μ + μ − + anything at s = 52 GeV at the CERN Intersecting Storage Rings (ISR) is reported. These events can be interpreted as originating from J(3.1) decay into μ + μ − . Their p T distribution suggests a hadronic production. The cross section for J production is given and compared to the cross section for single lepton production. We conclude that J(3.1) production cannot fully account for single lepton production.

\sqrt s

Abstract Studying the reaction pp → ppπ+π− at s = 23 GeV and 45 GeV at the CERN ISR we have found an experimental definition of a new class of diffractive events which we attribute to double-Pomeron exchange. The correlation of the quasi-elastically scattered protons, the energy dependence of the cross section, and the angular momentum of the (π+π−) state are analysed and found to be in agreement with theoretical expectations for double-Pomeron exchange.