Target dependence of clan model parameter in 84 Kr 36 – Emulsion interactions at 1 GeV per nucleon

This article focusses on the study of clan model parameters and their target dependence in light of void probability scaling for heavy (Ag and Br) and light (C, N and O) groups of targets present in nuclear emulsion detector using ⁸⁴Kr₃₆ at ～1 A GeV. The variation of scaled rapidity-gap (rap–gap) probability with single moment combination has been studied. We found that experimental points lie approximately on the negative binomial distribution (NBD) curve, indicating a scaling behaviour. The increase in average clan multiplicities ( \(\bar {N}\) ) for interactions with the pseudorapidity interval (Δη) was also observed. The values of \(\bar {N}\) for AgBr targets are larger than those for C/N/O target and also average number of particles per clan ( \(\bar {n}_{\mathrm {c}}\) ) increases with increase in pseudorapidity interval. We further observed that for a particular target, the average number of particles per clan ( \(\bar {n}_{\mathrm {c}}\) ) increases with an increase in the size of projectile nucleus.     

Neutron–proton analyzing power at 12 MeV and inconsistencies in parametrizations of nucleon–nucleon data

We present the most accurate and complete data set for the analyzing power Ay(θ)$A_y(\theta )$ in neutron–proton scattering. The experimental data were corrected for the effects of multiple scattering, both in the center detector and in the neutron detectors. The final data at En=12.0 MeV$E_n=12.0\text{MeV}$ deviate considerably from the predictions of nucleon–nucleon phase-shift analyses and potential models. The impact of the new data on the value of the charged pion–nucleon coupling constant is discussed in a model study.     

Pre-equilibrium γ ray emission in different reaction mechanisms at 8 MeV/nucleon

Recent experimental results on particles-γ coincidence measurements on the systems ¹²C +⁶⁴Ni and ³⁵Cl +⁶⁴Ni at about 8 MeV/nucleon are interpreted as due to the effect of a Dipole pre-equilibrium emission produced during the damping of the proton-neutron relative collective motion in very deformed intermediate systems formed in the first instants of the collision. The pre-equilibrium effects are evaluated through semiclassic kinetic theories and through modified statistical approach to include non-stationary effects in Fusion processes, Massive Transfer reactions (in the ¹²C +⁶⁴Ni system) and in Binary Dissipative reactions (in the ³⁵Cl +⁶⁴Ni system). In particular the study performed on the dipole molecular component allows to establish a link between the above phenomenon and the charge and mass transfer process in quasi-peripheral reactions. Received: 15 April 1998 / Revised version: 8 June 1998     

π-He interactions at T=106 MeV

interactions at have been studied by means of a self-shunted streamer chamber filled with helium at atmospheric pressure. This technique allowed reconstruction of the complete kinematics of the nuclear events under analysis, since tracks of slow p, α, tritium and ³He are readily measurable. The study revealed that the ⁴He nucleus behaves as a Planck radiator, emitting a Planck-like spectrum of high energy γs, when hit by a π beam of . A resonant behaviour in the π⁻n invariant mass spectrum has been observed, with and in the neutron knockout reaction: we consider this to be the first experimental evidence for the existence of the Δ⁻. The observed mass shift and width narrowing are compatible with the activation of an isobaric collective resonance in the ⁴He nucleus. The collaboration has also observed a resonant behaviour in the π⁻pp invariant mass spectrum in the pp double-charge-exchange reaction, on nuclear photoemulsion, compatible with the activation of the J^P=0⁻d^′ dibaryonic resonance with a strong p-p final state interaction. A new direct measured upper limit for the ν_μ mass has been derived by measuring a complete decay π-μ-e event recorded at the CERN PS179 experiment (Ne scattering): at a 90% confidence level, .     

Strangeness in the nucleon: neutrino–nucleon and polarized electron–nucleon scattering

After the EMC and subsequent experiments at CERN, SLAC and DESY on the deep inelastic scattering of polarized leptons on polarized nucleons, it is now established that the Q²=0 value of the axial strange form factor of the nucleon, a quantity which is connected with the spin of the proton and is quite relevant from the theoretical point of view, is relatively large.In this review, we consider different methods and observables that allow one to obtain information on the strange axial and vector form factors of the nucleon at different values of Q². These methods are based on the investigation of the neutral current induced effects such as the P-odd asymmetry in the scattering of polarized electrons on protons and nuclei, the elastic neutrino (antineutrino) scattering on protons and the quasi-elastic neutrino (antineutrino) scattering on nuclei. We discuss in detail the phenomenology of these processes and the existing experimental data.     

Ground-state properties of closed-shell nucleus 56Ni with realistic nucleon–nucleon interactions

We have calculated the ground-state energy of the doubly magic nucleus ⁵⁶Ni within the framework of the Green’s function using the CD-Bonn and N³LO nucleon–nucleon potentials. For the sake of comparison, the same calculations are performed using the Brueckner–Hartree–Fock approximation. Both the continuous and conventional choices of single particle energies are used. Additional binding energy is obtained from the inclusion of the hole–hole scattering term within the framework of the Green function approach. In this study, comparison of the calculated ground-state energies, obtained by using the Brueckner–Hartree–Fock approach using continuous choice and different nucleon–nucleon potentials, with the experimental value is accomplished. The results show good agreement between the calculated values and the experimental one for the ⁵⁶Ni nucleus. The sensitivity of our results to the choice of the model space is examined.     

Ψ′ and J/Ψ production in p-W,p-U and S-U interactions at 200 GeV/nucleon

Ψ′ and J/Ψ yields are compared in p-W, p-U and S-U interactions at 200 GeV/nucleon. Their ratio decreases from proton-t to sulphur-induced reactions. It also decreases in sulphur-induced reactions from peripheral to central collisions. This result could indicate that the Ψ′ and J/Ψ suppression mechanisms have different origins in p- and S-induced reactions.     

The effect of nonlinearity in relativistic nucleon–nucleon potential

A simple form for nucleon–nucleon (NN) potential is introduced as an alternative to the popular M3Y form using the relativistic mean field theory (RMFT) with the non-linear terms in σ-meson for the first time. In contrast to the M3Y form, the new interaction becomes exactly zero at a finite distance and the expressions are analogous with the M3Y terms. Further, its applicability is examined by the study of proton and cluster radioactivity by folding it with the RMFT-densities of the cluster and daughter nuclei to obtain the optical potential in the region of proton-rich nuclides just above the double magic core¹⁰⁰Sn. The results obtained were found comparable with the widely used M3Y NN interactions.     

Breakup effects of 6,7li on elastic and inelastic scattering from 12C at 18–28 MeV/nucleon

The differential cross sections for elastic scattering of ^6,7Li from ¹²C and inelastic one from the lowest three excited states of ¹²C have been measured at bombarding energies of 18–28 MeV/nucleon. Theoretical analyses of the data have been performed in which consistent treatments of density distributions for the ground and excited states of both projectile and target nuclei are made in the framework of microscopic cluster models for ^6,7Li and ¹²C and projectile-target interactions are generated by the double folding of the M3Y effective nucleon-nucleon interaction. About 25% reduction of the real part of folded potentials is required both in the analyses of elastic scattering with the single-channel calculation and in those of inelastic scattering with the coupled-channel calculation including the excited states of ¹²C. This reduction can be explained as a projectile breakup effect on elastic and inelastic scattering in comparison with a coupled-discretized-continuum-channels (CDCC) calculation and an extended CDCC one which allows mutual excitations of both projectile and target nuclei for ⁶Li case, respectively. It is also seen that an effect due to the target excitation on elastic scattering is of less importance than that of the ^6,7Li projectile breakup processes even fora deformed nucleus like ¹²C. Discrepancy between the extended CDCC calculation and inelastic data for the 0⁺₂ state of ¹²C suggests a strong influence from the ¹²C → 3α breakup channels in the ⁶Li case.     

Study of the charge dependence of the pion–nucleon coupling constant on the basis of data on low-energy nucleon–nucleon interactions

The relation between quantities that characterize the pion–nucleon and nucleon–nucleon interactions is studied with allowance for the fact that, at low energies, nuclear forces in nucleon–nucleon systems are mediated predominantly by one-pion exchange. On the basis of the values currently recommended for the low-energy parameters of the proton–proton interaction, the charged pion–nucleon coupling constant is evaluated at g_π²±/4π = 14.55(13). This value is in perfect agreement with the experimental value of g_π²±/4π = 14.52(26) found by the Uppsala Neutron Research Group. At the same time, the value obtained for the charged pion–nucleon coupling constant differs sizably from the value of the pion–nucleon coupling constant for neutral pions, which is g_π² 0/4π = 13.55(13). This is indicative of a substantial charge dependence of the coupling constant.     

π0-production in12C+12C at 800 and 1000 MeV/u

⁰-production in the system¹²C+¹²C was studied with the two-arm photon spectrometer TAPS at projectile energies of 800 and 1000 MeV/u. The experiments focus on the determination of the cross sections and the correspondingp _t -distributions. The results will extend the existing systematics of ⁰-production in heavy-ion collisions to a system with small mass.Presented at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994.     

A Monte Carlo generator of nucleon configurations in complex nuclei including nucleon–nucleon correlations

We developed a Monte Carlo event generator for production of nucleon configurations in complex nuclei consistently including effects of nucleon–nucleon (NN) correlations. Our approach is based on the Metropolis search for configurations satisfying essential constraints imposed by short- and long-range NN correlations, guided by the findings of realistic calculations of one- and two-body densities for medium-heavy nuclei. The produced event generator can be used for Monte Carlo (MC) studies of pA and AA collisions. We perform several tests of consistency of the code and comparison with previous models, in the case of high energy proton–nucleus scattering on an event-by-event basis, using nucleus configurations produced by our code and Glauber multiple scattering theory both for the uncorrelated and the correlated configurations; fluctuations of the average number of collisions are shown to be affected considerably by the introduction of NN correlations in the target nucleus. We also use the generator to estimate maximal possible gluon nuclear shadowing in a simple geometric model.     

Production of helium projectile fragments in {16O－emulsion interactions at 4.5 A GeV/c

The measurements of partial production cross sections of the multiple helium projectile fragments emitted at 4.5 A GeV/c {}^{16}O－Em interactions are reported. We have studied the production rate of helium projectile fragments due to fragmentation of {}^{16}O ions and compared it with that obtained from different projectiles at various energies. The dependence of on the mass number of the incident beams is formulated. The multiplicity distributions of the helium fragments produced in {}^{16}O－Em interactions at different energies exhibit Koba－Nielson－Olesen (KNO) scaling. The correlation of helium projectile fragments and target fragments is also investigated and it is found that the average of target fragments is increased with the decrease of the number of helium fragments in peripheral interactions.     

Leading nucleons in nucleon–air collisions

We present in this paper a calculation of the hadronic flux in the atmosphere. Using an iterative leading-particle model in the Glauber framework, we relate the moment of the leading-particle distribution in nucleon–air collisions with its counterpart one in nucleon–proton collisions. Received: 6 April 1999 / Revised version: 14 May 1999 / Published online: 22 October 1999     

Analysis of γ-ray production in neutral-current neutrino-oxygen interactions at energies above 200 MeV

It has long been recognized that the observation of γ rays originating from nuclear deexcitation can be exploited to identify neutral-current neutrino-nucleus interactions in water-Cherenkov detectors. We report the results of a calculation of the neutrino- and antineutrino-induced γ-ray production cross section for the oxygen target. Our analysis is focused on the kinematical region of neutrino energy larger than ～200 MeV, in which a single-nucleon knockout is known to be the dominant reaction mechanism. The numerical results have been obtained using for the first time a realistic model of the target spectral function, extensively tested against electron-nucleus scattering data. We find that at a neutrino energy of 600?MeV the fraction of neutral-current interactions leading to emission of γ?rays of energy larger than 6?MeV is ～41%, and that the contribution of the p_{3/2} state is overwhelming.     

Inclusive φ meson production in neutron–carbon interactions at 20–70 GeV

mesons have been reconstructed from their decay to positive and negative kaons, using the data obtained from interaction of neutrons at 20–70 GeV with a carbon target collected by EXCHARM experiment at the Serpukhov accelerator. The analysis relies on the use of reconstructing trajectories and particle identification. From about 45 million events (19600 ± 350) mesons were found. The meson mass is measured to be (1019.4 ± 0.1)MeV/c ²; the meson width is measured to be (4.9 ± 0.3)MeV/c ². The investigation has been performed at the Joint Institute for Nuclear Research at the Laboratory of Super High Energies.     

A-dependence of inclusive Φ-meson production in neutron-nucleus interactions at 30–70 GeV

The production of -mesons on nuclear targets (carbon, aluminium and copper) by high-energy neutrons has been analysed. The dependence of the -production cross section ratios on the nuclear mass numberA was parametrized by the power lawA with=0.81±0.06. Within the sensitive kinematic rangex _F>0 andp _T<1 GeV/c we have not observed any dependence of the exponent on the longitudinal or transverse momentum. A possible interpretation of the measuredA-dependence is discussed in the Appendix.The authors are grateful to A. M. Baldin, E. I. Maltsev and I. A. Savin for supporting these investigations; E. M. Likhacheva, L. V. Silvestrov, V. E. Simonov, G. G. Takhtamyshev and N. V. Vlasov for their participation in the experiment.     

Cluster ion–solid interactions from meV to MeV energies

The nature of cluster ion–surface interactions changes dramatically with the kinetic energy and mass of the incoming cluster species. In this article we review some recent work on the nature of cluster–surface interactions spanning an energy range from a few tens of meV/atom to several MeV/cluster and cluster sizes in the range of 1–300000 atoms/cluster. We describe five possible distinct outcomes of a single cluster impact event: (i) deposition into a non-epitaxial configuration, (ii) deposition into an epitaxial configuration, (iii) crater formation by liquid flow, (iv) crater formation by hydrostatic pressure, (v) implantation. PACS 65.80.+n; 82.60.Qr; 61.46.Hk; 02.70.Ns     

The temperatures of protons andπ − mesons in central nucleus-nucleus interactions at a momentum of 4.5 GeV/c per incident nucleon

An estimate of the temperature of protons and ^– mesons in central He–Li, He–C, C–C, C–Ne, C–Cu, C–Pb, O–Pb, Mg–Mg interactions is presented. The results indicate an increase of the proton temperature with increasing mass numbers of projectile and target nuclei (A _p ,A _T ) fromT _p =(118±3) MeV for He–Li toT _p =(141±2) MeV for C–Pb. The temperature of ^– mesons does not depend onA _P ,A _T andT 95 MeV. A satisfactory fit for ^– mesons in C–Cu, C–Pb, O–Pb, Mg–Mg collisions can be achieved by using a form involving two temperatures,T ₁ andT ₂. The relative yield of the high temperature component (T ₂) is 24% for C–Cu, C–Pb, and Mg–Mg interactions. The observed results forT _P in C–Ne, C–Cu and C–Pb collisions are consistent with the prediction of the thermodynamic hagedorn model.