A.I. Titov

Large momentum pion production in proton nucleus collisions and the idea of “fluctuons” in nuclei

Abstract It is shown that in proton-nucleus collisions, the production of pions with large momenta can be explained by the assumption of the existence of nuclear density fluctuations (“fluctuons”) at short distances of the nucleon core radius order, with the mass of several nucleons.

Multilayer Scintillator Responses for Mo Observatory of Neutrino Experiment Studied Using a Prototype Detector MOON-1

An ensemble of multi-layer scintillators is discussed as an option of the high-sensitiv ity detector Mo Observatory Of Neutrinos (MOON) fo r spectroscopic measurements of neutrino-less double beta decays. A prototype detector MOON-1, which c onsists of 6 layer plastic-scintillator plates, was built to study the sensitivity of the MOON-type detector. The scintillation photon collection and the ener gy resolution, which are key elements for the high-sensitivity experim ents, are found to be 1835±30 photo-electrons for 976 keV electrons and V = 2.9±0.1 % ( E/E = 6.8±0.3 % i n FWHM) at the QEE ~ 3 MeV region, respectively. The multilayer plastic-scintillator structure with good energy resolution as well as good background suppression of E J rays is crucial for the MOON-type detector to ach ieve the inverted hierar chy neutrino mass sensitivity. PACS: 14.60.Pq; 23.40.-s; 29.40.McAn ensemble of multilayer scintillators is discussed as an option of the high-sensitivity detector MOON (Mo Observatory of Neutrinos) for spectroscopic measurements of neutrinoless double beta decays. A prototype detector MOON-1, which consists of 6-layer plastic scintillator plates, was built to study the photon responses of the MOON-type detector. The photon responses, i.e., the number of scintillation photons collected and the energy resolution, which are key elements for high-sensitivity experiments, are found to be 1835 � 30 photoelectrons for 976 keV electrons and � ¼ 2:9 � 0:1% (� E=E ¼ 6:8 � 0:3% in FWHM) at the Q�� � 3 MeV region, respectively. The multilayer plastic scintillator structure with high energy resolution as well as a good signal for the background suppression of � –� rays is crucial for the MOON-type detector to achieve inverted-hierarchy neutrino-mass sensitivity. It will also be useful for medical and other rare-decay experiments as well.

On a fragmentation mechanism of relativistic heavy ions

Abstract A model is proposed describing main features of a behaviour of the fragmentation cross sections for relativistic ions including their relative yields. The reaction is assumed to proceed in two stages: At the first one the ion is excited by the peripheral collision with a nucleus, at the second one it decays statistically in flight with emitting a fragment. A strong analogy is demonstrated for the process with the corresponding reactions of nonrelativistic ions.

Neutrino studies in 100Mo and MOON - Mo Observatory of neutrinos

Abstract The MOON (Molybdenum Observatory Of Neutrinos) project is a hybrid ββ and solar ν experiment with 100 Mo. It aims at high sensitive studies of ββ decays with a sensitivity of m ν > ∼ 0.03 eV and real-time studies of pp and 7 Be solar νs. The double β rays from 100 Mo are measured in prompt coincidence for the 0νββ studies, and the inverse β rays from solar-ν captures of 100 Mo are measured in delayed coincidence with the subsequent β decay of 100 Tc. Measurements with good position resolution enable one to select true signals by spatial and time correlations.

On the six-quark structure in the deuteron form factor

The charge and quadrupole deuteron form factors are investigated in a wide region of momentum transfer taking into account the deuteron six quark structure. It is shown that the contribution due to the antisymmetrization of the wave function with respect to quark variables is small and the contribution of the “true” six quark admixtures plays the leading role in the region of large momentum transfer.

Spectral caustics in laser assisted Breit–Wheeler process

Abstract Electron–positron pair production by the Breit–Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering.

Hadronic sources of dileptons from heavy ion collisions at intermediate and relativistic energies

Abstract The kinetic model developed previously for soft hadron-nucleus and nucleus-nucleus collisions has been extended to describe low mass dilepton production. A fairly good description of available experimental data on dileptons created in both p+Be collisions from 12 to 1 GeV and Ca+Ca collisions at energies of 2 and 1 GeV/nucleon, is attained taking into account a variety of e + e − sources. Confirming a previous estimate of the ππ annihilation process, it has been found that the ω/ϱ→e + e − decay contributes as much as ππ annihilation does and to the same region of invariant masses, even for Ca+Ca (1 GeV/nucleon) collisions.

Decay anisotropy of e+e− sources from pN and pd collisions

Abstract A full calculation of lepton-pair angular characteristics is carried out for e+e− pairs created in pp, pn and pd collisions at intermediate energies. It is demonstrated that the proposed new observable, the dilepton decay anisotropy, quite sensitively changes for different sources and may be useful for their disentangling. The relevance of the dilepton decay anisotropy is shown in the context of a puzzling energy behaviour for the ratio of the lepton yield from pd to pp reactions as observed at the BEVALAC.

Estimates of dielectron production in pp and pd reactions at 1–2 GeV

Abstract Estimates of elementary cross sections for dielectron production in pN and pd reactions are presented. We use the vector dominance model for all hadron-hadron-photon vertices. A dynamical suppression mechanism (off-shell behavior of the two-body T-matrix, mass dependent Δ production rate) brings the elementary rate near to previous estimates which did not use vector meson dominance. However, near to the ρ mass a characteristic shoulder appears in our approach. We consider Δ, η Dalitz decays and bremsstrahlung at 1–2 GeV as dominant sources of dielectrons. At higher energies the bremsstrahlung contribution is only a subclass of direct vector meson decays. Relying on a realistic deuteron wave function we predict the ratio of dielectron production in pd to pp reactions.

MOON for a next-generation neutrino-less double-beta decay experiment; present status and perspective

The performance of the MOON detector for a next-generation neutrino-less double-beta decay experiment was evaluated by means of the Monte Carlo method. The MOON detector was found to be a feasible solution for the future experiment to search for the Majorana neutrino mass in the range of 100-30 meV.