Antonio Gonzalez-Arroyo

Second-order contributions to the structure functions in deep inelastic scattering (III). The singlet case

Abstract Pointlike QCD predictions for the singlet part of the structure functions are given up to next-to-leading order of perturbation theory. This generalises the result obtained in the first paper of this series, which deals with the non-singlet case. An interesting by-product, here shown, is an exact and simple analytical expression for the anomalous dimension matrix to second non-trivial order in the QCD coupling constant.

Second-order contributions to the structure functions in deep inelastic scattering: (II) Comparison with experiment for the non-singlet contributions to e, μ-nucleon scattering

Quantum chromodynamics predictions for the non-singlet structure functions of ep and μp inclusive scattering are tested against experiment. Target mass corrections and leading and next-to-leading terms αc are taken into account. The fits to experimental data are very good; they improve systematically when including second-order corrections. The preferred value for the invariant parameter Λ entering αc is Λ=0.20 ± 0.06 GeV, when second-order and target mass corrections are taken into account.

Diffractive Production of Strange Mesons at 63-{GeV}

Abstract Nearly 200 000 examples of the diffractive process K − p → K − π − π + p at 63 GeV have been obtained using a two magnet spectrometer equipped with Cerenkov counters for secondary particle identification. In addition some 2000 examples of the process K − p → ω K − p have been obtained. The K ππ data have been subjected to partial-wave analysis. The dominant J P = 1 + system couples to K ∗ π , in both S and D waves, ϱ K, κπ and e K. The data confirm the existence of two J P = 1 + Q mesons and their masses, widths and branching ratios are given. The ifωK data show that the couplings of the Q mesons to ω K are approximately equal to the couplings to ϱ 0 K. The two 1 + nonets expected in the quark model are discussed in the light of this and other recent experiments. There is strong evidence for a broad J P = 0 − resonance at about 1.46 GeV. At higher masses, structure in the J P = 2 − partial waves establishes the existence of at least one J P = 2 − L meson.

Forward particle production in π−p andK−p collisions at 58 GeV/c and comparison with quark models

We present single inclusive π±, π0 andK± spectra in the forward fragmentation region (x>0.2,pT<1.5 GeV/c) as well as correlations between two charged particles. The data were recorded in an unseparated negative hadron beam at the CERN SPS using a large acceptance forward spectrometer. Our maasurements are compared in detail with several models which emphasise the role of the beam valence quarks in this production process. The connection to measurements at largepT is also investigated.

Testing QCD predictions beyond the leading order for non-singlet structure functions in neutrino scattering

Abstract Quantum chromodynamics predictions for the non-singlet pieces of the structure functions in neutrino inclusive scattering are tested against experiment. Next-to-leading QCD terms, and higher-twist contributions are taken into account. After discussing the uncertainties (both experimental and theoretical) inherent to the untempered use of moments, pointwise reconstruction is effected. The ensuing fits to experimental data are excellent in all the x , Q 2 region explored (2 GeV 2 ⪅ Q 2 ⪅ 180 GeV 2 ). The preferred value of Λ (defined in the minimal renormalization scheme) obtained is Λ = 0.17 ± 0.08 GeV, perfectly compatible with one found previously from ep, μp scattering, Λ = 0.20 ± 0.06.

Evidence for the associated production of strange particles and φ mesons

Abstract Results are presented of an experiment studying inclusive ∅-meson production off protons by hadrons of 93 and 63 GeV incident momentum. Evidence is found for an enhanced probability of observing additional strange particles when the final state contains a ∅ meson. This supports the assumption that central production of ∅ mesons proceeds, for a significant part, by the OZI allowed fusion of strange quarks.

Evidence for a non-\(q\bar q\) tensor meson at 1,410 MeV produced in the reaction π−p→K s 0 K s 0 n at 63 GeV

AbstractWe present an analysis of theKs0Ks0 system produced in the reaction π−p→Ks0Ks0n at 63 GeV based on ∼700 events in the kinematical region of |t|<0.5 GeV2. We concentrate on masses between 1,200 and 1,600 MeV where a double maximum structure is observed. Performing an amplitude analysis in this mass interval we find thatS,D0 andD+ waves contribute to the mass spectrum at approximately equal strength. The peaks are attributed to spin 2 waves. However, we failed to explained them by interferingf(1270),A2(1310) andf′(1520) resonances alone. While the first peak can be associated withf(1270)−A2(1310) production, an additional tensor meson is needed with mass of ∼1410 MeV and a narrow width for a description of the second one. The analysis as well as the energy dependence deduced from some publishedKs0Ks0 mass spectra suggests this object to be dominantly produced by a natural parity exchange. Because the 2++

Evidence for a spin-5 boson resonance at 2300 MeV

q\bar q