P. Kyberd

Spin dependence of the inclusive reaction p + p (polarized) → π0 + X at 24 GeV/c for high-pT π0 produced in the central region

Abstract The spin dependence of π 0 inclusive production by 24 GeV/ c protons has been measured using a polarized target for Fhe Feynman x near 0 in the transverse momentum range 1.0 p T c . The results indicate a negative updown asymmetry growing strongly with p T and greater than 50% in absolute value for p T greater than 2 GeV/ c .

Measurement of Deep Inelastic Compton Scattering of High-energy Photons

Abstract We present the first results on inclusive photo-production of prompt photons at high transverse momenta. The data were taken in an open spectrometer at CERN using a high intensity photon beam energy between 50 and 150 GeV. After subtracting the yield of photons from indirect sources, a clear excess is observed for transverse momenta above 2.5 GeV c Deep inelastic Compton scattering with appropriate QCD corrections account for this excess. The data disfavour the gauge integer charge quark models so far proposed.

Measurement of the polarization parameter in 24 GeV/c proton-proton elastic scattering at small momentum transfers

Abstract A measurement of the polarization parameter P0 in pp elastic scattering has been made at 24 GeV/c over the range |t| = 0.1 to 0.9 (GeV/c)2, positive, falling to zero around |t| = 0.8 (GeV/c)2. For the range 0.1 ⪕ |t| ⪕ 0.4 GeV /c) 2 , P0 is constant at about 0.03.

Measurement of the polarization parameter in 24|GeV/c pp elastic scattering at large momentum transfers

A measurement of the polarization parameter Po in pp elastic scattering has been made at 24 GeV/c over the four momentum transfer range .7 ≤ |t| ≤ 5.0 (GeV/c)2. The structure of Po has changed compared to typical lower energy data. The second peak is suppressed and a dip has appeared at |t| ≅ 3.6 (geV/c)2

Measurement and prediction of the drift-distance/drift-time relationship of a small jet chamber operated with carbon dioxide/isobutane

Abstract As part of the preliminary studies for the vertex jet chamber of OPAL a small prototype chamber has been operated using carbon dioxide/isobutane and argon/ethane. A nitrogen laser has been used to produce an ionizing track in the chamber at a distance to the sense-wire plane that could be varied by means of a quartz pentaprism attached to a micrometer. This has enabled the drift-distance/drift-time relationship to be measured with an accuracy of 5–10 μm. The drift-distance/drift-time relationship has also been predicted from calculations of the electric field configuration inside the chamber and of the electron drift-velocity as a function of electric field. Measurement and predictions agree to the level of ∼ 10 μ m, thus demonstrating the feasibility of drift-distance/drift-time predictions for the final vertex jet chamber of OPAL, for which detailed laser measurements will not be possible. Corrections to the drift-distance/drift-time relationship for small variations in pressure, temperature and gas composition have also been predicted and shown to be in agreement with experimental measurements. An an alternative to the separate measurement of pressure, temperature and gas composition, it has been demonstrated that a direct measurement of the drift-velocity at one point in the chamber enabled the corrections to the drift-distance/drift-time relationship over the entire chamber volume to be calculated to the ∼10 μ m level.

Polarization in p-n elastic scattering at 24 GeV/C

Data are presented on the analyzing power A for p‐n elastic scattering at 24 GeV/c in the range 0.1?−t?0.8 (GeV/c)2.

Measurement of the polarization parameter in 24 GeV/c proton-neutron elastic scattering

The polarization parameter in pn elastic scattering has been measured at 24 GeV/c over the range of four-momentum transfer squared 0.1 < |t| < 1.25 (GeV/c)2, and found to be negative except for a zero at |t| = 0.65 (GeV/c)2.

Spin Dependence of the Inclusive Reaction pp↑ → π0 + X at 24 GeV for High pt π0 Produced at XF = 0

The spin dependence of inclusive π0 production by 24 GeV/c protons has been measured using a transversely polarized proton target at 90° CM in the transverse momentum range 1 ≤ pt ≤ 2.5 GeV/c. The results indicate a negative up-down asymmetry growing strongly with pt (A = (-56 ± 32)%) at pt = 2. GeV/c.