A search for new massive particles

We have searched for an almost stable, charged particle produced in 400 GeV proton-nucleus collisions. A total of 5 × 10¹⁰ light secondary particles were sampled in a secondary beam of 70 GeV/c momentum. If a 4.5 to 6.0 GeV mass particle is produced with a cross section comparable with the production cross section of the upsilon then this experiment places an upper limit on the lifetime of such a particle of about 5 × 10^?8 s.     

Measurement of the inclusive charged-current cross section for neutrino and antineutrino scattering on isoscalar nucleons

This paper reports on measurements of the total cross section for the inclusive reaction v_μ+N , as a function of incident energy. Neutrinos and antineutrinos with energy in the range 30–300 GeV were produced in the 1982 Fermilab narrow-band neutrino beamline. A total of 35 000 neutrino and 7000 antineutrino interactions were recorded in the CCFR detector located in LabE. The incident neutrino flux was determined by methods similar to those used in previous experiments. The rate of increase with energy of the total cross section (σ/E _v) in the range 30 to 75 GeV was determined to be 0.659±0.005(stat)±0.039(syst)×10^?38 cm²/GeV and 0.307±0.008(stat)±0.020(syst)×10^?38 cm²/GeV for incident neutrinos and antineutrinos, respectively. The 5.9% systematic errors are due primarily to uncertainties in the flux intensity measurement. The energy dependence of the cross section in the regionE _ν=100–300 GeV was found to be linear, as determined by relative normalization techniques. A weighted average of our previous and present measurement for the total ν-N cross section yields: $$\begin{gathered} \sigma (vN) = 0.666 \pm 0.020(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \sigma (\bar vN) = 0.324 \pm 0.014(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \end{gathered} $$ .     

Study of π−π− scattering in π−n interactions at high energies

We have measured the inclusive cross section for the reaction π^?n→pX^?? at 21, 205 and 360 GeV/c in the kinematic region |t_np|<1.0 (GeV/c)². The differential cross sections can be described qualitatively by the reggeized one-pion-exchange amplitude at all momenta studied; however, there is evidence for the contribution of other amplitudes. The extracted π^?π^? total cross section for 4?s_ππ?340 GeV² is of the order of 10–12 mb. The average number of charged particles and dispersion of the charged particle multiplicity distributions for various s_ππ intervals are compatible with results observed in hadron-proton interactions.     

Rise of proton proton total cross section and inclusive spectra

The origin of the rise of p-p total cross section (σ_t(pp)) is investigated by making use of the inclusive sum rule. The contribution to the rise of σ_t(pp) from the development of sharp peak near the kinematical boundary in the process p+p→p+ “anything” is almost completely canceled out by the decrease of the cross section in other x-region between s=45 (GeV/c)² and s=2820 (GeV/c)². Then the net contribution to the rise of σ_t(pp) from the process p+p→p+ “anything” is very likely to be zero. The true origin of the rise of σ_t(pp) is found to be the increase of inclusive cross sections at x ? 0 between PS and ISR energies. The contribution from the process p+p→π+ “anything” at x ? 0 to the rise of σ_t(pp) is estimated to be 3.2 mb, that from the process p+p→K + “anything”, 0.71 mb and that from the process p+p→$\text{p}$ “anything”, 0.62 mb. According to our conclusion we expect that all total cross sections will rise with energy at high energy.     

Measurement of elastic J/ψ photoproduction at HERA

The reaction γ p → J/ψ p has been studied in ep interactions using the ZEUS detector at HERA. The cross section for elastic J/ψ photoproduction has been measured as a function of the photon-proton centre of mass energy W in the range 40 < W < 140 GeV at a median photon virtuality Q ² of 5 × 10^?5 GeV². The photoproduction cross section, σ_{γp→ J/ψp}, is observed to rise steeply with W. A fit to the data presented in this paper to determine the parameter δ in the form σ_{γp→ J/ψp} α W ^δ yields the value δ = 0.92±0.14±0.10. The differential cross section dσ/d ¦t¦is presented over the range ¦t¦< 1.0 GeV² where t is the square of the four-momentum exchanged at the proton vertex. dσ/d ¦t¦falls exponentially with a slope parameter of $4.6pm 0.4_{-0.6}^{+0.4} {? GeV}^{-2}$. The measured decay angular distributions are consistent with s-channel helicity conservation.     

The holographic bubble chamber experiment and the determination of the effective charmed quark mass and theK-factor for hadronic charm production

In the first holographic bubble chamber experiment — the HOBC experiment — we have accumulated a total of 40000 holograms with particle interactions. We have determined the total charm pair cross section inpN collisions to be 23.3 _?7.7 ⁺¹⁰ μb and 3.6 _?1.7 ^+2.3 μb for 360 and 200 GeV/c incident protons respectively. We have assumed a linear dependence of the cross section on the atomic number of the target. This experiment has demonstrated the feasibility of holographic recording in small bubble chambers. Assuming that the charm cross section can be described by the standard QCD factorized expression with gluon fusion and quark-antiquark annihilation, we have used our measured charm cross sections with other measurements to determine the effective charmed quark mass to be 1.8 _?0.35 ^+0.25 GeV/c². TheK factor, which describes the importance of the higher order corrections, is calculated to be 9.8 _?6.9 ^+12.5 (See noted added in proof.)     

Coherent single pion production by antineutrino charged current interactions and test of PCAC

The cross section for coherent production of a single π^? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10^?40 cm²/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ ² dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV.     

Hadron production in 200 GeV μ-copper and μ-carbon deep inelastic interactions

The measurements of the z and p_T² distribution of hadrons produced in the interactions of 200 GeV muons with copper and carbon nuclei are shown in different x_Bj and virtual photon energy intervals. Effects of the jet scattering are seen at the lowest virtual photon energies while for energies above 70 GeV there is no evidence of these effects. Comparison with a theoretical model indicates that at high jet energies the parton fragmentation distance is greater than the nuclear radius and that the parton absorption cross section is less than 10 mb.     

Analysis of cosmic ray data on nucleon-nucleus collisions and its implication on high energy behaviour of nucleon-nucleon total cross section

From existing cosmic ray measurements of theinelastic collision cross sections of nucleons on nuclei of carbon, iron and lead in the range of energies 10² to 10⁴ GeV as well as the measurements of cross sections on air nuclei in the extensive air shower (EAS) regions (10⁵ to 10⁸ GeV), we conclude that the Glauber multiple scattering theory is adequate to account for the data. Recent suggestion of Maor and Nussinov to parametrize the nucleon-nucleon total cross section with a component growing proportional to ln² E (E is the incident energy) is at variance with the EAS data. However the data are consistent with a nucleon-nucleon total cross section rising no faster than lnE in these energy regions.     

Production of large p⊥ single particles and multiparticle systems (JETS) in K−p interactions at 110 GeV/c

Differential cross sections of single particles and multiparticle systems produced in K^?p interactions at 110 GeV/c are presented. At large values of transverse momentum (p_⊥) we find the multiparticle cross section to be an order of magnitude larger than that for single particles. This and other features of our data are consistent with results obtained at 200 GeV/c, that have been interpreted as evidence of a new dynamical mechanism in hadron-hadron interactions. However, similar features are observed in a K^?p experiment at 16 GeV/c.     

Diffractive proteon fragmentation in 16, 32, and 110 GeV/cK − p interactions and the diffractive production of heavy quarks(s\bar s,c\bar c)

The inclusive proton diffraction dissociation cross sections in 16, 32, and 110 GeV/cK ^? p interactions are determined from the spike nearx=1 in the inclusive negative particle spectra and are compared to those obtained inK?p interactions using other selection methods at various energies. The same procedure is applied to events containing aV ⁰ in order to obtain the cross section for diffractive \(s\bar s\) production. While the total cross section for proton diffraction is found to be approximately constant in the energy range studied here, proton diffraction yielding an \(s\bar s - pair\) is found to increase significantly. In particular it is almost constant at 85 μb forΛ ⁰ and Σ production but for \(NK\bar K\) it rises from zero at 16 GeV.c to about 200 μb at 110 GeV/c. From the result for \(s\bar s\) diffractive production an estimate for the \(c\bar c\) diffractive production cross section of approximately 1–10 μb at 110 GeV/c is obtained.     

Inclusive particle production in π− n interactions at high energies

Results on inclusive particle production in π^? n interactions at 21, 205 and 360 GeV/c are presented. The invariant cross sections in both neutron fragmentation and central regions are found to be equal within errors to the corresponding cross sections for π^? p collisions and exhibit the same energy dependence. A strong energy dependence of the invariant cross section ratios of negative and positive pions is observed. There is also an indication of transverse momentum dependence of these ratios. The η^? correlations in the neutron fragmentation region show little variation with energy and are in agreement with the predictions of the naive quark recombination scheme.     

Measurement of inclusive pion double charge exchange on 16O at T 0 ≥ 0.5 GeV with the SKS spectrometer at KEK

The inclusive cross section for pion double charge exchange on ¹⁶O at T ₀ = 0.5 and 0.75 GeV was measured with the superconducting kaon spectrometer (SKS) at KEK in a joint ITEP/KEK experiment. The result shows a relatively weak energy dependence of the measured cross section, which is in contradiction with its rapid drop predicted within the conventional model of two sequential single charge exchanges. The data of this experiment agree with the results that were obtained previously from similar measurements at ITEP and which are indicative of a significant contribution from the mechanism of inelastic Glauber rescatterings for T ₀ ? 0.6 GeV.     

Ultra-high energy neutrino-nucleon and neutrino-electron cross-sections in the standard model,in supersymmetric and superstring models

The neutrino-nucleon cross-section is calculated for energies up to 10¹⁵ GeV in the framework of the standard model assuming that the nucleon structure functionF ₂(x, Q ²) goes like ln²(a/x) asx→0. The cross-sections forv _μ e ^?(v _e e ^?)-interactions rise linearly with energy up toE _ν～10⁷ GeV and amount at this energy to ～10% of the neutrino-nucleon cross-section. The νN-cross-sections with production of supersymmetric particles in the framework of a supersymmetric model with minimal particle content are estimated. Photino-nucleon and photino-electron interactions are considered for masses of the squarks and sleptons in the range of 80–300 GeV. In superstring inspired unified models an estimation is made of the νN-interaction with an exchange of light leptoquarks.     

Experimental cross section for dimuon production and the Drell-Yan model

We have measured the absolute cross section for dimuon production in hadron collisions at 200 GeV/c in the continuum region M = 4–8.5 GeV. In all the channels studied (pN, $\text{p}$N, π^±N and π^?H₂) the experimental cross section is significantly larger by a factor of 2.3 ± 0.5 than expected from the Drell-Yan model. Furthermore, our proton-nucleon data allow a determination of the nucleon valence structure function which agrees with the deep inelastic lepton scattering data.     

Production of vector and tensor mesons in proton-proton collisions at\sqrt s = 52.5 GeV

Inclusive production of ?⁰,f, andg ⁰ mesons and ofK _s ⁰ ,K ^*0 (892), ? andK ^*0(1430)mesons has been measured at <y>～2.6 and <p _T >～1.1 GeV/c in proton-proton interactions at \(\sqrt s = 52.5\) GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andp _T dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.     

The energy dependence of nuclear reaction cross sections

The reaction cross section σ_R^pA(E) for proton-nucleus collisions varies with energy as the total cross section σ_t^pN(E) does for proton-nucleon scattering in the energy regime 100 MeV ? E ?400 GeV. We propose several empirical relations, and test them by a χ² analysis of various data. Within the framework of Glauber theory, the parameters in the relations can be linked to the cross section for a single inelastic collision.     

Maximal electromagnetic contribution to pp inelastic cross sections at ISR energies

The maximal electromagnetix contribution to the pp inelastic cross section is estimated. Although this contribution is insufficient in itself to explain all of the recently observed rise at ISR energies if the purely strong cross section is asymptotically constant, it could amount to as much as approximately 3 mb at √s ≈ 53 GeV if the purely strong cross section rises with energy through the range of present accelerator energies like (ln s)² or slower.     

Neutrino–nucleon cross section at intermediate energy from KM3 neutrino telescopes

The capability of a KM³ neutrino telescope to bounds the neutrino–nucleon cross section in the intermediate energy range (10⁵ GeV<E<10⁷ GeV) is studied. We use an observable which only makes use of the upward-going neutrino flux, so that the Earth filters the atmospheric muons, and it is only weakly dependent on the initial astrophysical flux uncertainties and experimental systematic. In order to study the sensitivity to departures from the standard model we have considered a cross section which is a version perturbed of the standard model one, dependent of two parameters. We present the results as regions for the allowed values for both, the parameters space and the cross section.     

Two-photon exchange in p⊆)p→ℓ+ℓ−X and a comparison with QCD

A thorough study of lepton-pair production from two-photon annihilation in p?)p collisions is presented. The differential cross section is calculated over a large range of energies (27?√s?800 GeV as a function of the dilepton mass M as well as the dilepton transverse momentum Q_T and the Feynman variable x_F. No kinematical approximations (such as the equivalent photon approximation) are made. For Q_T ≈ 0 the two-photon mechanism represents an important fraction of the pp→e⁺e^?X cross section already at ISR energies, whereas at ISABELLE energies it dramatically dominates in the interval 0?Q_T?1 GeV. At ISR energies these conclusions follow from a direct comparison of the two-photon contribution with pp→e⁺e^?X data. For the ISABELLE energy range the expected O(α_s) QCD contribution to pp→?⁺?^?X, corrected for soft gluon radiation to all orders (in leading bilogarithmic approximation), was taken as a reference. At larger Q_T and ISR energies the γγ contribution is negligible, whereas at √s = 800 GeV γγ/QCD? 10–20% almost everywhere. Furthermore, two-photon candidate events from the ISR are shown to be in reasonable agreement with theory. A decomposition of the γγ cross section into contributions from both proton vertices being elastic, inelastic and of mixed configuration is given. The results provide important clues for a future isolation of the two-photon mechanism.