S. A. Zotkin

Intermittency patterns in π+p and K+p collisions at 250 GeV/c

Abstract Intermittent behaviour is observed in π + p and K + p collisions at 250 GeV/ c . It is stronger there than in O 16 emulsion, but weaker than in e + e − collisions. A jet cascading mechanism is, therefore, the most likely interpretation. Presently used fragmentation models do not (fully) reproduce the effect, suggesting that an improvement of the hadronization picture is needed.

Cross sections and charged multiplicity distributions for π+p,K+p andpp interactions at 250 GeV/c

Cross sections and charged multiplicity distributions for π+p,K+p andpp interactions at 250 GeV/c are presented and compared to each other as well as to earlier (for π+p andK+p lower energy) data. Consistently, the meson-proton (M+p) data have narrower multiplicity distributions and higher average multiplicity thanpp data. Up to our energy, generalized KNO functions describe the energy dependence of the shape of the multiplity distribution with one parameter forM+p and one forpp collisions. If interpreted in terms of negative binomials, the parameter 1/k tends to be slightly lower forM+p than forpp data. For both types of hadron-hadron collision, 1/k is larger than fore+e− andlp collisions.

Maximum particle densities in rapidity space of π+ p, K+ p and pp collisions at 250 GeV/c

Abstract In a study of π + p, K + p and pp collisions at √ s =22GeV in the european hybrid spectrometer (EHS), the maximum charged particle density per given rapidity interval is found to rise linearly with charged particle multiplicity, independent of beam particle type and practically independent of energy between 22 and 900 GeV. An anomalous π + p event is found with ten particles within the very narrow rapidity interval Δy =0.098.

Charged particle production inK + p, π p andpp interactions at 250 GeV/c

New results are reported on inclusive charged particle production inK+p,π+p andpp collisions at 250 GeV/c. Inclusive longitudinal and transverse momentum spectra of positively and negatively charged particles are presented. Scaling in the fragmentation regions and scaling violation in the central c.m. region is investigated in detail. The topological pseudo-rapidity densities are shown to scale in the c.m. energy range from 22 to 900 GeV.

Observation of a narrow baryon resonance decaying to pK S 0 in proton-nucleus interactions at 70 GeV/c with the SVD-2 setup

AbstractData from the SVD-2 experiment that were obtained at the IHEP accelerator in 70-GeV/c proton-nucleus interactions are analyzed with the aim of searches for an exotic Θ+ baryon that decays through the pKS0 channel. The reaction pN → pKS0 + X characterized by a bounded multiplicity of charged secondaries is used for this analysis. A resonance of mass M = 1526 ± 3(stat.) ± 3(syst.) MeV/c2 and width Γ < 24 MeV/c2 is observed in the invariant-mass spectrum of the pKS0 system at a statistical significance of 5.6σ. The mass and the width of this resonance correspond to the recently found positive-strangeness Θ+ baryon, which was predicted to be an exotic baryon consisting of five quarks (pentaquark),

Single diffraction dissociation inπ+ andK+p interactions at 250 GeV/c

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Self-affine scaling from non-integer phase-space partition in π+p and K+p collisions at 250 GeV/c

. The total cross section for the production of a Θ+ baryon in pA interactions is estimated at a value within the range 30–120 μb for xF ≥ 0. An analysis of the A dependence of the cross section for Θ+-baryon production does not reveal a significant deviation from the A dependence for inelastic events (∼A0.7).

Direct soft photon production in K+p and pi+p interactions at 250 GeV/c

Taking into account the anisotropy of phase space in multiparticle production, a self-affine analysis of factorial moments was carried out on the NA22 data for