L. Camilleri

Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

Abstract Invariant cross-sections are presented for the inclusive reaction p + p → π o + anything, Measurements of large transverse momentum π o s (2.5 GeV/ c p ⊥ c ) were made near 90° at the CERN ISR at five centre-of-mass energies (√ s = 23.5, 30.6, 44.8, 52.7 and 62.4 GeV. At large p ⊥ , the invariant cross-sections are seem to vary with s and p ⊥ , in good agreement with a fit of the form Ap ⊥ − n F ( p ⊥ /√ s ), with n ≈8 and F ( p ⊥ /√ s )≈ exp (−26 p ⊥ /√ s ).

A Study of Inclusive Spectra and Two Particle Correlations at Large Transverse Momentum

Abstract The inclusive production of π and η mesons at 90° from proton-proton collisions has been measured at the CERN ISR at centre-of-mass energies between 23.5 and 62.4 GeV. The momentum correlation of charged particles emitted together with a large transverse momentum pion has also been studied, using two magnetic spectrometers each centred at 90°.

A measurement of inclusive π0 production at large pT from p-p collisions at the CERN ISR

Abstract The inclusive cross section for larger p T π 0 production near 90° in p-p collisions at the CERN ISR is presented for centre-of-mass energies 30.7, 53.1 and 62.4 GeV. The data are inconsistent with scaling of the form p T − n F ( x T ), with constant n or with n allowed to depend on x T = 2p T / s . For s = 53.1 and 62.4 GeV , the value of n found for 3.5 p T c is n = 8.0 ± 0.5, in agreement with previous experiments. However, for 7.5 p T c the value becomes n = 5.1 ± 0.4.

A Measurement of Inclusive pi0 Production at Large p(T) from p p Collisions at the CERN ISR

Abstract The inclusive cross section for larger p T π 0 production near 90° in p-p collisions at the CERN ISR is presented for centre-of-mass energies 30.7, 53.1 and 62.4 GeV. The data are inconsistent with scaling of the form p T − n F ( x T ), with constant n or with n allowed to depend on x T = 2p T / s . For s = 53.1 and 62.4 GeV , the value of n found for 3.5 p T c is n = 8.0 ± 0.5, in agreement with previous experiments. However, for 7.5 p T c the value becomes n = 5.1 ± 0.4.

Observation of high transverse momentum electrons at the CERN ISR

Abstract A search for high transverse momentum electrons directly produced in proton-proton collisions has been performed at the CERN ISR. The apparatus included a magnetic spectrometer with wire spark chambers, a lead-glass counter array, and a threshold gas Cerenkov counter. At a centre-of-mass energy √ s = 52.7 GeV, a signal has been observed in the range 1.6 T ∗ GeV /c . The signal occurs at a level of approximately 10 −4 of the inclusive pion cross-section.

A measurement of the production of massive e+e− pairs in proton-proton collisions at √s = 62.4 GeV

Abstract An apparatus consisting of a superconducting solenoid magnet, cylindrical drift-chambers, and two arrays of lead-glass Cerenkov counters has been used at the CERN ISR to study the production of e+e− pairs of invariant mass above 6.5 GeV/c2. Cross sections for the continuum and the ϒ family of resonances are presented, as well as the mean transverse momentum 〈pT〉 of the electron-positron pairs in the continuum and resonance region.

A lead-glass cherenkov detector for electrons and photons

Abstract An apparatus for the detection of high-energy electrons and photons is described. Lead-glass Cherenkov counters measure the energies, and charged particle tracks are reconstructed using an array of wire spark chambers. The mode of operation, calibration, and stability of the system are described, and details are given of the ability to discriminate electrons from hadrons.

Search for ! e oscillations in the NOMAD experiment

We present the results of a search for nu_mu → nu_e oscillations in the NOMAD experiment at Cern. The experiment looked for the appearance of nu_e in a predominantly nu_mu wide-band neutrino beam at the CERN SPS. No evidence for oscillations was found. The 90% confidence limits obtained are Delta m^2 ~ 10 eV^2.

Search for direct single-photon production at large pT in photon-proton collisions at √s = 62.4 GeV

Abstract As part of a study of large p T phenomena in photon-proton collisions at the CERN ISR, a search for direct single photon production has been performed. A statistical division of the data sample into the fraction consistent with single photon and the fraction due to multiphoton decays of neutral hadrons is accomplished by measuring the average conversion probability for the sample in a one radiation length thick converter. The fraction of the sample attributable to direct single photon production is 〈 γ /all〉 = 0.074 ± 0.012 for 6 GeV/ c p T 10 GeV/ c , and 〈 γ /all〉 = 0.26 ± 0.04 for p T > 10 GeV/ c , with an additional systematic uncertainty of ±0.05 for both values.

Observation of high mass electron-positron pairs produced in proton-proton collisions at the CERN ISR

Abstract In an experiment performed at the CERN Intersecting Storage Rings (ISR), 11 e+e− pairs of high invariant mass value (> 2.5 GeV/c2) have been observed. Of these events, 9 can be interpreted as arising from the reaction p + p → J (3.1) + anything. the cross-section for this reaction is estimated and compared with the result obtained at lower centre-of-mass energies.