Werner Herr

First results on proton extraction from the CERN SPS with a bent crystal

Abstract The feasibility of extracting protons from the halo of a high energy beam by means of a bent silicon crystal has been investigated. Protons diffusing from a GeV beam circulating in the SPS at CERN have been extracted at an angle of 8.5 mrad. Efficiencies of abour 10 percent, orders of magnitude higher than the values achieved previously, have been measured. The present results are promising in view of beam extraction from future multi-TeV proton accelerators.

Channeling of high-energy particles in bent crystals - Experiments at the CERN SPS

Abstract During the latest decade, experiments have been performed at the CERN SPS to investigate the use of high-energy channeled nuclei in bent crystals for extraction, beam splitting and beam bending. An understanding of channeling in a bent crystal with extraction and deflection efficiencies for different energies, crystal types and ions has been developed. Furthermore, the long-standing question of radiation damage has been addressed with encouraging outcome. This makes extrapolations possible for the construction of, e.g., an extraction device for the LHC at CERN, RHIC at Brookhaven or new splitting elements in high-energy beams.We present the main results obtained and discuss existing and future applications of bent crystals in high-energy physics.

High pT K±π± production in p-p collisions at the ISR; strangeness suppression and gluon effects

Abstract The ratios of high p T charged kaon to pion production cross sections at √ s = 45 and 62 GeV are presented. The values of the K ± π ± ratios are essentially independent of both √ s and x T = 2p T √s and are compatible with a strangeness suppression factor λ = 0.55. By contrast, the K − π − values fall with x T suggesting a gluonic origin of K − . QCD calculations agrees with the measurements.

High efficiency multi-pass proton beam extraction with a bent crystal at the SPS

Recent measurements of 120 GeV proton extraction by means of a bent silicon crystal at the CERN-SPS accelerator are summarized. The existence of multi-pass extraction has been proven by blocking first-pass extraction: using a crystal covered with an amorphous layer, extracted beam with high efficiency was observed, which provides a direct proof for the importance of the multi-pass mechanism. This opens new possibilities in the design and optimization of a bent crystal extraction scheme.

Multiplicity dependence of transverse momentum spectra at ISR energies

Abstract We observe an increase of the average transverse momentum with the multiplicity of the charged particles produced in the central rapidity region of proton-proton collisions at ISR energies. The increase is smaller than that observed at the CERN proton-antiproton collider. The magnitude of the effect is the same for negative and positive particles.

Measurement of the proton-antiproton total cross section at the SppS collider by a luminosity dependent method

Abstract The proton-antiproton total cross section was measured at the center-of-mass energy of s = 541 GeV at the S p pS at CERN using a luminosity dependent method. The result σtot=63.0±2.1 mb is in agreement with the luminosity independent measurement performed earlier by the UA4 Collaboration.

Multiplicity Distributions in

Abstract The multiplicities of charged secondaries from inelastic αp and αα collisions have been measured using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. Corrected multiplicity distributions for αα and αp interactions are compared with those for pp interactions and with theoretical predictions.

\alpha \alpha

AbstractData are presented on Pomeron-Pomeron interactions which produce a centralπ+π− system in proton-proton collisions at

\alpha p

\sqrt s = 62 GeV