R.H. Giles

Inclusive neutral strange particle production in νp interactions

In a selected sample of 6770 charged current (CC) events of νp interactions with 〈Eν〉 = 43 GeV and 〈W〉 = 4.6 GeV, 359 K0, 180 Λ and 13 Λ have been observed, which corresponds to a corrected production rate at least one neutral strange particle in (17.4±0.8)% of the CC events. The ratio of the inclusive Λ to K0 production cross section is found to be 0.26±0.03. The number of CC events containing at least one K0 increases with increasing Eν and Q2, while the CC events containing at least one Λ remain practically constant. The fractions of the total hadronic energy carried by K0 and Λ are found to be approximately the same in νp as in ep and μp interactions. In the hadronic c.m.s., the K0 are produced mostly forwards, the Λ mostly backwards, with asymmetry parameters of +0.32±0.02 and −0.45±0.06, respectively. The total strange particle production cross section is estimated to be (25±4)% of the cross section for production of CC events with W>1.5 GeV and that for charm production (10±2)% of the CC cross section well above charm threshold (W>3 GeV). The production of the resonances K∗+ (890) and Σ+ (1385) has been observed. The production rate of K∗+ (890) is comparable to that of D∗+ (2009), above the corresponding thresholds.

The SOUDAN 2 detector: The design and construction of the tracking calorimeter modules

SOUDAN 2 is a 960-ton tracking calorimeter which has been constructed to search for nucleon decay and other phenomena. The full detector consists of 224 calorimeter modules each weighing 4.3 tons. The design and construction of the modules are described. The modules consist of finely segmented iron instrumented with 1 m long drift tubes of 15 mm internal diameter. The tubes enable three spatial coordinates and dE/dx to be recorded for charged particles traversing the tubes.

First observation of Cherenkov ring images using hybrid photon detectors

Abstract A ring-imaging Cherenkov detector, equipped with hybrid photon detectors, has been operated in a charged-particle beam. Focussed ring images from various particle types were detected using silica aerogel, air and C 4 F 10 gas radiators. The detector, a prototype for the CERN LHC-B experiment, is described and first observations are reported.

Measurement of the Ratio of Neutral to Charged Current Cross-sections of Neutrino Interactions in Hydrogen

Abstract The ratio R p of the neutral current to charged current cross sections has been measured in the BEBC bubble chamber filled with hydrogen and exposed to the CERN SPS wideband neutrino beam. It is found that an event selection in terms of the transverse momentum of the hadronic system is very effective in reducing backgrounds and enables R p to be determined with an error of less than 10%. Combining the results from hydrrogen and isoscalar targets, the individual values of the coupling constants u L 2 and d L 2 are determined separately to be u L 2 = 0.15 ± 0.06 and d L 2 = 0.17 ± 0.08. The results are compatible with the standard SU (2) × U(1) model. The value of sin 2 θ W determined from this experiment is 0.19 ± 0.04.

Single π+ production in charged current neutrino-hydrogen interactions

Abstract The reaction ν p→ μ − p π + (777 events) is studied at neutrino energies from 5 to 200 GeV. A total of 551 events fit the channel ν p→ μ − Δ ++ (1232) with χ 2 probability greater than 2%. Decay angular distributions of the Δ ++ are investigated and the density matrix elements are studied as functions of Q 2 , the square four-momentum transfer. The total Δ ++ production cross section and the differential cross section d σ /d Q 2 are determined. Using the Schreiner-von Hippel parametrization of the Adler model, the value of the axial mass determined by fitting the total cross sections above 20 GeV is M A = 0.85±0.10 GeV. The model describes the differential cross sections reasonably well above Q 2 ⋍0.2 GeV 2 . Disagreements, however, are found for some values of the density matrix elements of the Δ ++ decay angular distributions and their Q 2 dependence. The (p π + ) mass region above the Δ ++ (1232) contains evidence for the presence of higher mass Δ ++ resonances and, above 2 GeV, for the forward emission of fast π + .

Production of charmed mesons in neutrino interactions in hydrogen

Abstract Production of charmed mesons has been observed in neutrino-hydrogen interactions in 285 000 photographs of BEBC exposed to the CERN wide-band neutrino beam. In ∼ 6000 charged current events, two events have been found each giving a three-constraint kinematical fit with production of only one strange particle, namely a K−, which is identified by its characteristic reaction K−p→Σ−π+. These events are thus examples of ΔS=−ΔQ reactions corresponding to charm production on a valence quark. For both events the effective mass of a (K− + pions) system is equal to the D0(1863) mass while the effective mass of this system plus a π+ is equal to the D∗+(2009) mass. The mass difference ΔM=M( D ∗+ )−M D 0 is 145.2 ± 0.6 MeV. The first event is interpreted as ν p →μ − pD ∗+ and the second as ν p →μ − pD ∗+ π + π − , both with D ∗+ → D 0 π + . The rate of inclusive D∗+ production has been estimated for all events by assuming that each negative track in turn is a K− and using the fact that the error on ΔM is small. It is found that the cross section σ(ν p →μ − D ∗+ + anything ) relative to σ(νp→μ− + anything), above the D∗ threshold, is (4.1 ± 2.4)%.

The observation of underground muons from the direction of Cygnus X-3 during the January 1991 radio flare

Abstract Muons recorded in the Soudan 2 underground nucleon decay detector from January 1989 to February 1991 have been examined for any correlation with the radio flares of Cygnus X-3 observed during this period. On two nearby days during the radio flare of January 1991 a total of 32 muons within 2.0° of the Cygnus X-3 direction were observed when 11.4 were expected.

Performance of a prototype RICH detector using hybrid photo-diodes

A prototype Ring-Imaging Cherenkov detector has been operated in a charged particle test beam. Cherenkov photons are imaged onto a plane of hybrid photo-diode detectors. The geometrical arrangement of the prototype and data-taking conditions are described. An analysis of the detector performance, using silica aerogel, air and C4F10 gas radiators, is presented. The photon yields and observed Cherenkov angle resolutions are found to be in good agreement with Monte Carlo simulation and satisfy the requirements of the RICH 1 detector in the LHCb experiment.

First results from the Soudan 2 proton decay experiment

First results on contained neutrino interactions are presented from the Soudan 2 proton decay experiment. 20 neutrino events have been found in a fiducial exposure of 0.29 kton years.

Investigation of quark-singlet and gluon fragmentation functions in ν p interactions

Abstract Moments of the quark-singlet fragmentation function are determined from measured moments of the u-quark fragmentation functions D ± u ( z , q 2 ) into positive and negative hadrons in the reaction ν p→ μ − + hadrons. The q 2 dependence of these moments is investigated in the framework of leading-order QCD and estimates are given for the moments of the gluon fragmentation function. The results are based on a sample of θ 7800 charged current events from a BEBC neutrino-hydrogen experiment.