U. Idschok

Multiplicities, topological cross sections, and single particle inclusive distributions from pp interactions at 12 and 24 GeV/c

Results on multiplicities, topological cross sections, total particle production cross sections, and correlations between charged particle and π0 production are presented for pp interactions at 12 and 24 GeV/c incident laboratory momentum. Inclusive production of π±, Ks0, p, Λ, Σ± andΛ is studied; particle spectra are shown in single and double differential form and are compared, in different kinematic regions, with data obtained at other incident momenta and with other beam particles.

Observation of vector meson production in inclusive pp reactions

Abstract We have measured cross sections, rapidity and transverse momentum distributions, and vector meson polarization for the reactions pp→ ϱ o +anything, pp→ ω +charged particles, and pp → K ∗± + anything at incident laboratory momenta of 12 and 24 GeV/ c . We discuss various consequences of our results as well as possible connections with lepton pair production.

Measurement of the reaction γd → π−pp, and determination of cross sections for the reaction γn → π−p, at photon energies between 0.2 and 2.0 GeV

Abstract The reaction γ d→ π − pp has been measured in a bubble chamber experiment at DESY with a bremsstrahlung beam of E γ max = 5.5 GeV. Total and differential cross sections are presented for the energy region from 0.2 to 2.0 GeV. The extraction of cross sections on the neutron is discussed in detail. The impulse approximation and the closure relation, with corrections for the exclusion principle and the Fermi motion effects, as well as the Chew-Low extrapolation technique are applied. Total cross sections and angular distributions for the reaction γ n→ π − p, deduced by these methods, are presented in graohs and tables. The results are compared with other experiments and with various predictions. No positive evidence for an isotensor electromagnetic current is found. The results disagree with some of the measurements of radiative pion capture, if detailed balance is assumed to connect the two reactions.

Search for Heavy Neutrino Decays in the {BEBC} Beam Dump Experiment

Abstract New limits on lepton mixing parameters are derived from a search for decays of heavy neutrinos in a proton beam dump experiment. The limits | U oi | 2 , | U e i | 2 −6 −10 −7 are obtained for neutrino mass eigenstates v i of mass between 0.5 and 1.75 GeV, which can be produced through mixing in charmed D meson decays. This is the first such limit on | U o i | 2 for neutrino masses greater than 0.5 GeV. For the mass eigenstate v 3 in particular, we obtain the limits | U o 3 | 2 −7 −10 −8 , | U e 3 | 2 −9 −10 −10 for the mass range 150–190 MeV, assuming the v 3 to be produced directly in charmed F meson decays.

Inclusive neutron and lambda production in proton-proton interactions at 12 and 24 GeV/c

Abstract A method for the determination of neutron spectra in a bubble chamber experiment is developed. Double differential cross sections for inclusive neutron and lambda production are presented. The n/Λ particle ratios are determined as functions of x and pT; at pT = 0 GeV/c they are compatible with the ratios measured in pCu interactions at 24 GeV/c. Our neutron spectra are compared with spectra for protons produced near the direction of the incident neutron in pn interactions at FNAL and with neutron spectra measured in pp interactions at the ISR. Exchange mechanisms are studied in the framework of single diffraction dissociation and the triple-Regge model. The scattering of virtual pions and kaons on real protons is investigated.

Rapidity-gap separation and study of single-diffraction dissociation in pp collisions at 12 and 24 GeV/c☆

Abstract An event-by-event separation of the single-diffractive component in the inclusive reaction p + p → p + X is attempted with our 12 and 24 GeV/ c bubble-chamber data, using a method involving largest rapidity gaps. The method yields a (non-strange) single-diffraction cross section of about 7 mb at both energes, dominated by two and four prongs. For the diffractive component the recoil mass distribution d σ /d M X 2 shows a sharp peak near M X 2 = 2 GeV 2 at both energies, with a long tail that broadens significantly with increasing energy. This shape is reasonably well described by the diffractive terms of a triple-Regge fit to the full pp data. The slope parameter of the diffractive t distribution shows a precipitous drop with increasing M X 2 , levelling off abruptly at M X 2 ≈ 3 GeV 2 . The mean charged multiplicity of the diffractive system appears to be linear in log M X 2 and independent of s .

A study of charge distributions in inelastic proton-proton collisions

Abstract Charge distributions for the secondaries from inelastic proton-proton collisions are studied by means of new data from an experiment at 12 and 24 GeV/ c (2 m HBC at CERN). By comparison with π ± p data at 16 GeV/ c , the inclusive charge distributions for the fragments of an incident proton and pion, respectively, are analysed. In addition, the cross sections for charge exchange between cms hemispheres are presented for the various charged-particle multiplicities. For events with no more than one neutral particle, charge and baryon exchange between cms hemispheres are compared to those between clusters. For the inelastic two-prong reactions, the two-dimensional distributions in longitudinal phase space are presented.

Inclusive K∗±(892) production in pp and π+p interactions

A study is presented of the inclusive production cross sections of K∗±(892) vector mesons in pp interactions at 12 and 24 GeV/c and in π+p interactions at 16 GeV/c. The K∗± inclusive cross section is ∼0.9 mb for both pp at 24 GeV/c and π+p interactions at 16 GeV/c. For pp interactions, σ(K∗+) and σ(K∗−) are seen to rise with energy, showing a threshold behaviour. In both pp and π+p interactions, σ(K∗+) largely exceeds σ(K∗−) at these energies and this excess is interpreted as K∗+ production by beam and target fragmentations. The decays of K∗±0 yield ∼30% of the K0 observed in the final states. The pT2 dependence of both K∗+ and K∗− cross sections is described by an exponential with slope of ∼3.3 (GeV/c)−2. The longitudinal momentum spectra for K∗+ in 16 GeV/c π+p and 24 GeV/c pp interactions are similar in shape in the target hemisphere. The K∗− spectra are similar over the whole kinematic region when viewed in the quark c.m.s. and point to a central production mechanism. Comparing K∗+ and ρ0 production, striking similarities are found.

Investigation of the reactions pp→pp+meson resonance at 12 and 24 GeV/c

Abstract The reactions pp→pp+meson, where meson= η , ϱ 0 , ω , and f, have been investigated at P inc = 12 and 24 GeV/ c . Cross section, rapidity distributions, momentum transfer and decay angular distributions are presented. Upper limits on the cross sections for S ∗ (1000) and Φ production are given. An attempt is made to determine the dominating pairs of exchanges in the production of these resonances.

Photoproduction of negative pions on neutrons at photon energies between 0.2 and 2.0 GeV

Abstract Total and differenial cross sections of the reaction γ +n→p+ π − have been determined for photon-energies between 0.2 and 2.0 GGeV. Below 500 MeV the differential cross sections are compared with theoretical predictions derived from fixed-momentum-transfer dispersion relations.