M. Regler

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.

The European Hybrid Spectrometer - a facility to study multihadron events produced in high energy interactions

Abstract The European Hybrid Spectrometer is described in its preliminary version for the NA16 charm experiment. The performance of the small hydrogen bubble chamber LEBC and the detectors of the spectrometer is discussed. In particular the combination of the bubble chamber information with the spectrometer data is described in detail. The track reconstruction efficiency is 90%. The precision with which vertices seen in the bubble chamber are reconstructed is around 10 μm and the two track resolution is 40 μm. Therefore very complex event configurations, in particular charm particle decays, can be reconstructed correctly.

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.

Single γ-ray spectra from proton-proton collisions at centre-of-mass energies from 30 to 50 GeV

Abstract The energy spectra of single γ-rays produced in proton-proton collisions at the CERN Intersecting Storage Rings have been measured at three primary energies and four production angles: E CM = 30.2 GeV , 44.7 GeV and 52.7 GeV, θ CM = 10.2°, 6.4°, 23.5° and 90°.The results are shown to be compatible with the conjecture of limiting distributions. A simple interpolation formula is presented.

TRANSVERSE MOMENTUM DISTRIBUTION OF PHOTONS PRODUCED IN PROTON--PROTON COLLISIONS AT THE INTERSECTING STORAGE RINGS.

Abstract The energy spectrum of γ-rays produced in proton-proton collisions at the CERN Intersecting Storage Rings (ISR) has been measured at 90°. The spectrum is an exponential function of the transverse momentum. Its slope is found to be energy independent from 6.7 GeV to 53 GeV center of mass energy. It is shown that the same result holds for neutral pions.

Topological cross sections and charged particle multiplicities inpp interactions at 360 GeV/c

Using data obtained with EHS equipped with the Rapid Cycling Bubble Chamber (RCBC) exposed to a proton beam of 360 GeV/c, we calculate topological cross sections. We present in great detail the procedure and the techniques used to correct raw data. Finally, we give multiplicity moments and multiplicity correlations and we compare the values obtained in our experiment, together with data at other energies, with different models.

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 .