P.S.L. Booth

Production spectra of π±, K±, p± at large angles in proton-proton collisions in the CERN intersecting storage rings

Abstract Results are given on the inclusive production of charged pions, kaons, and nucleons, in proton-proton collisions at c.m. energies from √ s = 23 to 63 GeV at large angles and for the transverse momentum range 0.1 p T c . The dependence of the production spectra on the collision energy √ s , the transverse momentum p T , and the longitudinal rapidity is discussed.

The Production of Charged Particles with High Transverse Momentum in Proton-Proton Collisions at the CERN ISR

Results are given on the inclusive production of charged pions, kaons and nucleons in high-energy proton-proton collisions in the centre-of-mass rapidity range |ycm| < 1 and for transverse momenta up to 4.8 GeV/c. The dependence of the composition of produced particles on ycm, the total energy s, and transverse momentum pT is discussed.

The DELPHI Microvertex detector

The DELPHI Microvertex detector, which has been in operation since the start of the 1990 LEP run, consists of three layers of silicon microstrip detectors at average radii of 6.3, 9.0 and 11.0 cm. The 73728 readout strips, oriented along the beam, have a total active area of 0.42 m2. The strip pitch is 25 μm and every other strip is read out by low power charge amplifiers, giving a signal to noise ratio of 15:1 for minimum ionizing particles. On-line zero suppression results in an average data size of 4 kbyte for Z0 events. After a mechanical survey and an alignment with tracks, the impact parameter uncertainty as determined from hadronic Z0 decays is well described by (69pt)2 + 242 μm, with pt in GeV/c. For the 45 GeV/c tracks from Z0 → μ− decays we find an uncertainty of 21 μm for the impact parameter, which corresponds to a precision of 8 μm per point. The stability during the run is monitored using light spots and capacitive probes. An analysis of tracks through sector overlaps provides an additional check of the stability. The same analysis also results in a value of 6 μm for the intrinsic precision of the detector.

The DELPHI silicon strip microvertex detector with double sided readout

The silicon strip microvertex detector of the DELPHI experiment at the CERN LEP collider has been recently upgraded from two coordinates (RΦ only) to three coordinates reconstruction (RΦ and z). The new Microvertex detector consists of 125 952 readout channels, and uses novel techniques to obtain the third coordinate. These include the use of AC coupled double sided silicon detectors with strips orthogonal to each other on opposite sides of the detector wafer. The routing of signals from the z strips to the end of the detector modules is done with a second metal layer on the detector surface, thus keeping the material in the sensitive area to a minimum. Pairs of wafers are daisy chained, with the wafers within each pair flipped with respect to each other in order to minimize the load capacitance on the readout amplifiers. The design of the detector and its various components are described. Results on the performance of the new detector are presented, with special emphasis on alignment, intrinsic precision and impact parameter resolution. The new detector has been taking data since spring of 1994, performing up to design specifications.

POLARIZED TARGET ASYMMETRY FOR PI-ZERO PHOTOPRODUCTION AT 4 GeV.

Abstract The polarized target asymmetry parameter has been measured for single πo photoproduction from hydrogen at 4 GeV and values of four-momentum transfer squared between −0.15 (GeV/c)2 and −1.8 (GeV/c)2.

Radiation tolerance of single-sided silicon microstrips

Abstract The RD20 collaboration is investigating the design and operation of an LHC inner tracking detector based on silicon microstrips. Measurements have been made on prototype detectors after irradiation with electrons, neutrons, photons, and protons for doses up to 5 Mrad and fluences up to 10 15 particles/cm 2 . The annealing of effective doping changes caused by high neutron fluences, one of the major limits to detector lifetime at the LHC, is shown to be strongly inhibited by cooling below room temperature. Detailed results are presented on the critical issue of microstrip capacitance. We have also investigated bulk damage caused by high-energy protons, interstrip isolation after neutron irradiation, and MOS capacitors irradiated with electrons and photons.

Production of high transverse momentum prompt photons and neutral pions in proton-proton interactions at 280 GeV/c

The inclusive cross sections for production of prompt photons and π0s by 280 GeV/c protons incident on a liquid hydrogen target, have been measured forpT in the range 4.0 to 6.5 GeV/c and for |xF|<0.45. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed. Phenomenological fits to the π0 and prompt photon cross sections are given.

Studies of proton-proton collisions at the CERN ISR with an identified charged hadron of high transverse momentum at 90°: (II) On the distribution of charged particles in the central region

Abstract Results are reported from an investigation of proton-proton collisions at a c.m. energy of 52.6 GeV, in which a charged hadron with large transverse momentum is produced near 90° in the c.m.s. We have studied the momentum and charge correlations between identified high- p T trigger particles and other charged particles in the central region (rapidity | y | p T particles with charge opposite to that of the trigger particle in a small solid angle around the trigger particle. The sum of the momenta of charged particles inside | y | c per GeV/ c increase of the trigger momentum. Opposite in azimuth to the trigger particle we observe close pairs of high- p T particles in both neutral and doubly charged combinations. In this region we see an indication of scaling in the x E variable for trigger momenta exceeding 3 GeV/ c . The distribution of charge is strongly correlated with the charge of the trigger particle. Otherwise the type of trigger particle does not affect strongly the observed event structure, but for trigger momenta above 3 GeV/ c , K − and p triggers are observed to have fewer negative high- p T recoil particles within | y |

Large angle production of stable particles heavier than the proton and a search for quarks at the CERN intersecting storage rings

Abstract Measurements have been performed on production of particles with mass 1.5 GeV/c2 and charge ⩾ 2 3 for θlab = 62.5° and s = 53 GeV . At pT = 0.7 GeV/c the relative rate of production of antideuterons to π− is (5 ± 1) × 10−5. The deuteron to antideuteron ratio is 3.7 ± 1.2. No new stable particle has been amongst 0.7 × 108 charged particles entering our detector.

Large-angle inclusive production of charged pions at the CERN ISR with transverse moment a less than 1.0 GeV/c

Abstract The inclusive production of π ± in proton-proton collisons has been measured for the transverse momentum range 0.15 to 1.0 GeV/ c over an angular range of 29° to 89° in the centre-of-mass system and for centre-of-mass energies √ s = 30.6 and 52.8 GeV. For each energy the invariant cross-section foe fixed transverse momentum was found to increase by about 15% as the centre-of-mass rapidity decreases from 1 to 0, i.e. the “central plateau” has not yet been reached.