K.C.T.O. Sumorok

A measurement of the A-dependence of the J/ψ cross section by comparing data on hydrogen and tungsten targets at 39.5 GeV/c

Abstract J/ψ production on hydrogen and tungsten targets has been compared at 39.5 GeV/ c and the variation of the A -dependence of the J/ψ cross section as a function of p t 2 and x F has been measured. The A -dependence parameter, α, rises with increasing p t 2 and falls with increasing x F . Both effects are shown not to be due to the Fermi motion of nucleons in the tungsten nucleus.

Experimental results on J/ψ production by π±, K±, p and p incident on hydrogen at 39.5 GeV/c

Abstract J/ ψ production at 40 GeV/ c by π ± , K ± , p and p incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π − have been measured to be (for x F > 0) σ(π − ) : σ(π + ) : σ( p ) : σ( p ) = 1 : (0.78 ± 0.09) : (0.83 ± 0.35) : (0.07 ± 0.04) . The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. M J 2 / ψ / s =0.13).

Performance of a UA1 Hadron Calorimeter Prototype

The hadron calorimeter for the UA1 experiment at the CERN SPS proton-antiproton collider consists of a lead-scintillator sandwich plus an iron-scintillator sandwich with wavelength shifter readout. We have tested prototype modules in muon and hadron beams in the momentum range from 0.7 to 90 GeV/c. For several angles of incidence, we have studied the uniformity of the response to hadrons as a function of position. This has included regions where there is reduced sensitivity due to mechanical constraints and the presence of the wavelength shifter readout. The response, resolution and degree of shower containment were measured as a function of incident momentum.

Central Hadron Calorimeter of UA1

Abstract An iron—scintillator sampling calorimeter is described, which measures hadronic energy in proton-antiproton interactions at the CERN 540 GeV SPS collider. Construction details are given of the instrumentation of the magnet pieces of the UA1 experiment and of the methods used to measure the calorimeter response and resolution. The system of lasers and quartz fibres, which allows long term monitoring of the calorimeter response, is also described.

Isobar model analysis of the reactions K−n → K−π-p and K−n → 0π-n in the centre-of-mass energy region 1.9 to 2.2 GeV

We have developed a program to perform a general isobar model partial-wave analysis of reactions of the type baryon + meson → baryon + meson + meson. Using this program energy-independent fits to the reactions K − n → 0 π-n and K − n → K − π-p_ have determined the most important partial waves for the quasi-two-body final states *(890)N, Δ(1236), Λ(1520)π and Λ(1815)π in the centre-of-mass energy range 1.9 to 2.2 GeV. Our results show clear evidence for Δ(1236) and Λ(1815)π decay modes of the Σ(2030), but the branching fraction for the decay of 2030) to Λ(1520)π is found to be only 0.06. The complexity of the results for the −K*(890)N partial waves makes it unclear whether there is also a −K*(890)N decay of the Σ (2030).

Data and partial-wave analysis for the reaction K−n → K∗− (890)n

Abstract New data are presented on the reaction K − n → K ∗− (890) n from a deuterium bubble chamber experiment. An energy-dependent partial-wave analysis from threshold to 2170 MeV c.m. energy is described, in which a new decay mode of the Σ(2030) resonance into K ∗ (890) N in the S = 3 2 state is clearly observed. An amplitude at resonance of 0.12 ± 0.02 is obtained, consistent with the assignment of the Σ (2030) to the same SU(3) decuplet as the Δ(1950).

Measurements of the reaction K−n → π−Λ in the C.M.S. energy range 2050 MeV to 2175 MeV and partial-wave analysis of this reaction between 1875 MeV and 2175 MeV

New bubble chamber data on the reaction K−n → π−Λ in the c.m.s. energy range 2050 MeV to 2175 MeV are presented. These new data have been combined with published data on this reaction and on the reaction K−p → π0Λ and a partial-wave analysis has been carried out between 1875 MeV and 2175 MeV. Parameters of the established resonances in this c.m.s. energy region have been determined and further evidence is presented for the existence of a Σ resonance with mass around 2100 MeV/c2 in the P3 partial wave.

An analysis of the Λ (1520) observed in a K− neutron production experiment

Abstract The mass, width and branching fractions of the Λ(1520) into K N, σπ, Λππ and σππ have been determined using a Λ(1520) sample produced in the reaction K − d→ Λ (1520) π − p s at K − -neutron centre-of-mass energies between 1.9 and 2.2 GeV. A Dalitz plot analysis of the Λ 0 π + π − decay mode shows that there is a substantial Σ(1385)π component. The SU(3) octet-singlet mixing angle for the 3 2 − baryons calculated from the partial widths for the s-wave σ(1385)π decay of the Λ(1520) and Λ(1690) is found to be consistent with that obtained from the d-wave decays of the singlet and octet members, within experimental limits.

Energy-dependent cross sections for K− neutron interactions in the cm energy range 1750–2200 MeV from five K− deuterium bubble chamber experiments

Experimental details and channel cross sections are presented for five K− deuterium bubble chamber experiments. Utilising the Fermi motion of the neutron the K−n cross sections are extracted over the c.m. energy range 1750–2200 MeV and where possible results are compared to related channels from other experiments.

New experimental results on the reactions K−n → π− Σ0 and K−n → π0 Σ− and a partial-wave analysis of these data between 1750 and 2200 MeV

Abstract New bubble chamber data on the reactions K − n → π 0 Σ 0 in the c.m. energy range 1750–2200 MeV are presented and are compared with the predictions of the most recent partial-wave analysis of the reaction K N → πΣ . The comparison stresses the need for data involving a single value of isotopic spin in the study of this reaction. An analysis of the new data yields two satisfactory solutions involving only well established resonances.