Nucleon resonance decay by theK 0Σ+ channel: Preliminary results

The strange meson production on a proton target in theK ⁰Σ⁺ channel is sensitive to nucleon resonance contributions. TheK ⁰ production on a deuteron target can provide information on the hyperon-nucleon final-state interaction. The experiments γp →K ⁰Σ⁺ andγd → K ⁰Σ⁺n have been carried out at the ELSA facility at Bonn. In this paper, we report the preliminary results of both experiments     

On a possibleK S -sigma mixing and theK L -K S mass difference

A possible mixing between theK _S meson and the sigma bosonσ is treated in the frame of a nonrelativistic and nonhermitean effective Hamiltonian. If parameters for the mass and width of theσ boson from the 2π mass distributions are used the experimental ratio of theK _L -K _S mass differenceδm to theK _S width:δm/Γ _S deviates by less than 33% from the predicted value.     

Leptogenesis and composite heavy neutrinos with gauge-mediated interactions

Leptogenesis is an appealing framework to account for the baryon asymmetry in the universe. To this end physics beyond the standard model is demanded. In this paper we investigate the possibility to attain successful leptogenesis with composite Majorana neutrinos. We work in the framework of effective gauge-mediated and contact interactions without any reference to an underlying compositeness theory. This approach is the one adopted in all current experimental searches for composite fermions at colliders. In the case of gauge-mediated interactions, we calculate the CP asymmetry in heavy composite neutrino decays. Both the direct and the indirect CP asymmetry are derived and resonant leptogenesis is also discussed. We find that the Sakharov conditions can be met and, for some choice of the parameters, the correct order of magnitude of the baryon asymmetry is reproduced.     

Intranuclear cascade in the interactions of neutrinos with neon nuclei

A method is developed for separating νN interactions from interactions involving an intranuclear cascade in νNe scattering at a mean neutrino energy of 145 GeV. The fraction of events featuring a cascade is evaluated by using a sample of νNe charged-current interactions. It is found that the multiplicity of charged particles in the forward direction takes the same value for events with and without a cascade for 4<W ²<550 GeV². In the backward direction, cascade events have the charge multiplicity higher than the multiplicity for cascade-free events by 2.36 units. It is found that particles with momenta less than 2 GeV/c make a dominant contribution to the rescattering process. A depletion of the fastest particles for W ²<50 GeV² is observed, in accord with the formation-time concept. From Yadernaya Fizika, Vol. 63, No. 9, 2000, pp. 1660–1669. Original English Text Copyright ? 2000 by Vataga, Murzin, Aderholz, Ammosov, Asratian, Barth, Bingham, Brucker, Burnstein, Chatterjee, Clayton, Ermolov, Erofeeva, Faulkner, Gapienko, Guy, Hanlon, Harigel, Ivanilov, Jain, G. Jones, M. Jones, Kafka, Kaftanov, Kalelkar, Kohli, Korablev, Kubantsev, Lauko, Lukina, Lys, Lyutov, Marage, Milburn, Mittra, Morrison, Moskalev, Myatt, Naon, Passmore, Peters, Rubin, Sacton, Schneps, J. Singh, S. Singh, Smart, Smirnova, Stamer, Varvell, Venus, Willocq. This article was submitted by the authors in English. Deceased. The author represents the E632 Collaboration     

On leptogenesis with two degenerate right-chiral neutrinos

We analyze the predictions of the most general version of the supersymmetric minimal seesaw model with only two right-chiral neutrinos, which are degenerate in masses at the scale of Grand Unification. We apply the renormalization group technique to the running of the masses of the right-chiral neutrinos and the neutrino Yukawa couplings and find that thermal leptogenesis can account for the observed baryon asymmetry of the Universe even with a low reheating temperature, allowing to overcome the gravitino problem. Presented at the XVI Indian Summer School “Understanding Neutrinos”, Prague, Czech Republic, September 8–13, 2004.     

Contraction of electroweak model can explain the interactions neutrinos with matter

The very rare interactions neutrinos with matter and the dependence of the corresponding cross-section on neutrinos energy are explained as contraction of the gauge group of the Electroweak Model already at the level of classical gauge fields. Small contraction parameter is connected with the universal Fermi constant of weak interactions and neutrino energy as $^2 (s) = \sqrt {G_{F^S } }$ .     

Backward emitted protons in interactions of neutrinos with nuclei in photoemulsion

Backward emitted protons with momentump>0.3 GeV/c in interactions of neutrino in the energy range 10–200 GeV with photoemulsion nuclei were investigated. Energy spectrum slope parameter of backward protons was measured to beT ₀=48.9±7.9 MeV. TheA-dependence power index of relative mean yield of backward protons was found to bea=0.68±0.12. A drop in the mean yield of backward protons at the four momentum squared over ～15 (GeV/c)² (the neutrino energy over ～50 GeV) was observed.     

Observation of the decay psi(2S)-->K0SK0L

The decay psi(2S)-->K(0)(S)K(0)(L) is observed using psi(2S) data collected with the Beijing Spectrometer at the Beijing Electron-Positron Collider; the branching fraction is determined to be B(psi(2S)-->K(0)(S)K(0)(L))=(5.24+/-0.47+/-0.48)x10(-5). Compared with J/psi-->K(0)(S)K(0)(L), the psi(2S) branching fraction is enhanced relative to the prediction of the perturbative QCD "12%" rule. The result, together with the branching fractions of psi(2S) decays to other pseudoscalar meson pairs (pi(+)pi(-) and K+K-), is used to investigate the relative phase between the three-gluon and the one-photon annihilation amplitudes of psi(2S) decays.     

The 0+ → 0+ positron double- β decay with emission of two neutrinos in the nuclei 96Ru, 102Pd, 106Cd and 108Cd

Theoretical results for two neutrinos in the nuclei ⁹⁶Ru, ¹⁰²Pd, ¹⁰⁶Cd and ¹⁰⁸Cd are presented. The study employs the Hartree-Fock-Bogoliubov model to obtain the wave functions of the parent and daughter nuclei, in conjunction with the summation method to estimate the double-beta decay nuclear matrix elements. The reliability of the intrinsic wave functions of ^{96, 102}Ru, ⁹⁶Mo, ^{102, 106, 108}Pd and ^{106, 108}Cd nuclei is tested by comparing the theoretically calculated spectroscopic properties with the available experimental data. The calculated half-lives T_1/2^2ν of ⁹⁶Ru, ¹⁰²Pd, ¹⁰⁶Cd and ¹⁰⁸Cd nuclei for 2ν β⁺β⁺, 2ν β⁺EC and 2ν ECEC modes are presented. The effect of deformation on the nuclear transition matrix element M_2ν is also studied.     

Oscillation of Dirac and Majorana neutrinos from muon decay in the case of a general interaction

We analyse the possibility of distinguishing Dirac and Majorana neutrinos in future neutrino factory experiments in which neutrinos are produced in muon decay when, in addition to a vector type as in the SM, there are also scalar interactions. We check this possibility in an experiment with a near detector, where the observed neutrinos do not oscillate, and in a far detector, after the neutrino oscillations. Neglecting higher-order corrections, even neutrino observation in the near detector does not give a chance to differentiate their character. However, this possibility appears in the leading-order after the neutrino oscillations observed in far detector.     

Weak-interaction observables from nuclear-structure calculations of 0νββ decay transitions

Physics of Atomic Nuclei - The present status of the calculation of the nuclear matrix elements associated with neutrinoless double-beta decay is discussed. The currently available approaches, as...