Search for charmed hadrons in neutral strange particle events in pp interactions at 19 GeV/c

A search for charmed hadrons has been made in proton-proton interactions at 19 GeV/c using events with one or two observed neutral strange particles. No evidence for charmed particles has been found. Upper limits for their production cross sections are presented.     

Search for collective phenomena in hadron interactions

New results of the search for collective phenomena have been obtained and analyzed in the present report. The experimental studies are carried out on U-70 accelerator of IHEP in Protvino. It is suggested that these phenomena can be discovered at the energy range of 50–70 GeV in the extreme multiplicity region since the high-density matter can form in this very region. The collective behavior of secondary particles is considered to manifest itself in the Bose-Einstein condensation of pions, Vavilov-Cherenkov gluon radiation, excess of soft-photon yield, and other unique phenomena. The perceptible peak in the angular distribution has been revealed. It was interpreted as the gluon radiation and so the parton matter refraction index was determined. The new software was designed for the track reconstruction based on Kalman Filter technique. This algorithm allows one to estimate more precisely the track parameters (especially momentum). The search for Bose-Einstein condensation can be continued by using the selected events with the multiplicity of more than eight charged particles. The gluon dominance model predictions have shown good agreement with the multiplicity distribution at high multiplicity and confirmed the guark-gluon medium formation under these conditions.     

Relatively compact interactions in many particle systems

For many-particle relatively compact interactions the essential spectrum of theN-particle Schrödinger Hamiltonian is shown to consist of a continuum [ _N , + [ whereN is the lowest many-body threshold of the system. This result applies in particular to separable interactions and some spin-orbit couplings. TheN-particle Green's function is studied with the help of the Weinberg equation for many-body forces whose kernel is shown to be compact in the complementary set of [N, + [.Attaché de Recherche au C.N.R.S.     

Backward particle production in neutrino neon interactions

Backward proton and pion production is studied in ν and \(\bar v\) charged current interactions in neon. The results are compared with other experiments and theory. The complete backward proton data is compatible with protons produced by reinteractions in the nucleus. However in events with only one proton, muon variables appear correlated to those for the backward proton, as expected by the two-nucleon correlation model.     

Search for coherent charged pion production in neutrino-carbon interactions

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.     

Pauli-correct separable potentials for composite particle interactions

Experimental totalβ-decay energies for short-lived isotopes of gallium and germanium are presented. The sources were produced as mass-separated fission products at the OSIRIS on-line separator at Studsvik. By applyingβ-γ-coincidence methodsQ _α-values were determined for^80,81Ga and^79,81,82Ge. For these nuclei on or close to the shellN =50 and in the vicinity of ther-process “seed”, the atomic mass excess is derived and compared with predictions from mass formulae.     

Search for supersymmetric particles in photon-electron interactions at high energy

We discuss the production of gauge fermions and scalar electrons in high energy scattering of real photons off electrons. We propose to perform scattering experiments with polarized photons to discriminate between left and right partners of electrons and thus test more stringently the supersymmetry character of these particles.     

Neutral strange particle production in antineutrino-neon charged current interactions

Neutral strange particle production in \(\bar v\) Ne charged current interactions is studied using the bubble chamber BEBC, exposed to the CERN SPS antineutrino wide band beam. From a sample of 1191 neutral strange particles, the inclusive production rates are determined to be (15.7±0.8)% forK ⁰ mesons, (8.2±0.5)% for Λ, (0.4±0.2)% for \(\bar \Lambda \) and (0.6±0.3)% for Σ⁰ hyperons. The inclusive production properties ofK ⁰ mesons and Λ hyperons are investigated. The Λ hyperons are found to be polarized in the production plane.     

The one particle theory of periodic point interactions

We solve explicitly and without approximation the problem of a quantum-mechanical particle inR ³ subjected to point interactions that are periodic inR ³ with periodicity of the typeZ, Z ², andZ ³. In the first case we get a model of an infinite straight polymer, in the second case we get a model of a monomolecular layer and in the third case we get a model of a crystal. In all three cases the unit cell of the Bravais lattice is allowed to contain any finite number of interaction sites (atomes), placed arbitrarily and with arbitrary interaction strength. In the case: one interaction site per unit cell we find explicit formulas for the resonance bands and energy bands and their corresponding wavefunctions.     

A spectropolarimetric study of theH α radiation from ellerman bombs

Polarization data are given for three whiskers recorded with the large solar vacuum telescope at the Baikal Observatory, Institute of Solar-Terrestrial Physics, Russian Academy of Sciences. The observed degree of polarization varies from 2 to 13%. The direction of the polarization plane for the mediumintensity whisker was tangential, while that for the weakest one was radial. The brightest whisker had the polarization plane direction close to radial at the center of the line but tangential at the flanks. It is assumed that the polarization is due to impact excitation of a hydrogen-atom ensemble in the solar chromosphere by an electron beam, and estimates are made of the beam energy. St. Petersburg Fine Mechanics and Optics Institute, St. Petersburg. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 85–89, December 1998.     

Search for dibaryon production in 4Hep interactions at intermediate energies

With the aid of the 2-m liquid-hydrogen bubble chamber constructed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow), ⁴Hep interactions are studied at primary alpha-particle momenta of 2.7 and 5 GeV/c (the respective kinetic energies of primary protons in the ⁴He rest frame are T _p=220 and 620 MeV). The effective-mass spectra of two nucleons from the reactions ⁴Hep → dppn and ⁴Hep → pppnn are analyzed. The effective-mass spectrum of the two-proton system produced in the quasielastic-charge-exchange reaction p ⁴He → n _F(pp)d at T _p=620 MeV (here, n _F stands for the fast neutron in the ⁴He rest frame) shows a narrow peak, which is indicative of the existence of a dibaryon whose mass and width are M _2p =2008±13 MeV and Γ _2p =0±5 MeV, respectively. In the mass spectra of the two-proton system from the reactions p ⁴He → n _F(pp)d and p ⁴He → p _F(pp)(nn), narrow threshold peaks are also found at a mass of M _2p ?1878–1879 MeV.     

Parametrization of the shape of hadron-production spectra in high-energy particle interactions

The transverse-momentum dependence of inclusive differential cross sections measured in various collider experiments for processes involving the production of long-lived charged hadrons was approximated by the sum of an exponential and a power-law function. The dependence of the parameters appearing in these functions on the colliding-particle energy and type was studied, and relationships between these parameters were established. A number of new regularities in the behavior of charged-particle spectra were discovered.     

Neutral strange particle correlations in 360 GeV/cpp interactions

Production properties and correlations forK _s ⁰ K _s ⁰ ,K _s ⁰ Λ,K _s ⁰ ¯Λ and Λ¯Λ systems in 360 GeV/cpp interactions are presented. All rapidity gap distributions are observed to peak at Δy=0 and the azimuthal angular distributions between the two particles are consistent with being flat. Experimental results are compared with the quark fusion and Lund models of particle production.