Elastic hadron scattering on Li isotopes at intermediate energies

The elastic scattering of hadrons (protons, charged pions, and positively charged kaons) on ^6,7,8Li nuclei is analyzed on the basis of Glauber-Sitenko diffraction theory. A few nuclear-wave-function versions found within two-and three-particle potential cluster models are used in the calculations. It is shown that the application of these wave functions in diffraction theory makes it possible to describe adequately the experimental differential cross sections and analyzing powers in hadron scattering at intermediate energies. In this study, particular attention is given to a comparison of the scattering of different particles on the same target nucleus, as well as to a comparison of scattering of particles of the same sort on different target nuclei.     

Charmed exotics in heavy ion collisions

Based on the color–spin interaction in diquarks, we argue that charmed multiquark hadrons are likely to exist. Because of the appreciable number of charm quarks produced in central nucleus–nucleus collisions at ultrarelativistic energies, the production of charmed multiquark hadrons is expected to be enhanced in these collisions. Using both the quark coalescence model and the statistical hadronization model, we estimate the yield of charmed tetraquark mesons, T_cc, and pentaquark baryons, Θ_cs, in heavy ion collisions at RHIC and LHC. We further discuss the decay modes of these charmed exotic hadrons in order to facilitate their detections in experiments. PACS 25.75.Dw; 14.20.Lq; 14.40.Lb     

Complete destruction of heavy nuclei by hadrons and nuclei

The total disintegration is considered of nuclei with atomic weights ～100 and 200 by high energy hadrons and He⁴, C¹² nuclei with a momentum of 4.5 GeV/c per nucleon. It is shown that mainly nucleons are emitted, and there is no residual nucleus the mass of which is comparable to that of the primary nucleus. The probability of total disintegration is considered as a function of projectile energy and mass. The multiplicity, energy and emission angle of particles are considered as well. It is shown that the density of nuclear matter in the overlap zone of colliding nuclei exceeds the usual one by a factor of ～4. A comparison is made with interaction models. A conclusion is drawn of the collective interaction mechanism (perhaps, of the shock wave type) of particle ejection from the target nucleus at the first stage of interaction and of explosive decay of the residual nucleus at the next one.     

Unusual effects of diffraction dissociation for multiproduction in deep inelastic scattering on nuclei

In hadron-nucleus interactions, the stronger is nuclear shadowing in the total cross section the higher is the multiplicity of secondary hadrons. In deep inelastic scattering nuclear shadowing at smallx is associated with the hadronlike behaviour of photons as contrasted to the pointlike behaviour in the non-shadowing region of largex. In this paper we predict dilution of multiproduction of secondary hadrons, and weaker fragmentation of the target nucleus, in deep inelastic leptoptoproduction on nuclei in the shadowing region of smallx as compared to the non-shadowing region of largex. This paradoxial conclusion has its origin in nuclear enhancement of the coherent diffraction dissociation of photons which affects multiproduction in the shadowing region and does not contribute in the non-shadowing region. We present numerical predictions for multiproduction in theμXe interactions studied by the Fermilab E665 collaboration.     

Pion emission in α-particle interactions with various targets of nuclear emulsion detector

The behavior of relativistic hadron multiplicity for4He-nucleus interactions is investigated. The experiment is carried out at 2.1 A and 3.7 A Ge V(Dubna energy) to search for the incident energy effect on the interactions inside different emulsion target nuclei. Data are presented in terms of the number of emitted relativistic hadrons in both forward and backward angular zones. The dependence on the target size is presented. For this purpose the statistical events are discriminated into groups according to the interactions with H, CNO, Em, and Ag Br target nuclei. The separation of events, into the mentioned groups, is executed based on Glauber's multiple scattering theory approach. Features suggestive of a decay mechanism seem to be a characteristic of the backward emission of relativistic hadrons. The results strongly support the assumption that the relativistic hadrons may already be emitted during the de-excitation of the excited target nucleus, in a behavior like that of compound-nucleus disintegration.Regarding the limiting fragmentation hypothesis beyond 1 A Ge V, the target size is the main parameter affecting the backward production of the relativistic hadron. The incident energy is a principal factor responsible for the forward relativistic hadron production, implying that this system of particle production is a creation system. However, the target size is an effective parameter as well as the projectile size considering the geometrical concept regarded in the nuclear fireball model. The data are analyzed in the framework of the FRITIOF model.     

EMC effect and breaking of additivity of nucleons in the high-energy hadron-nucleus interactions

The EMC effect implies a strong violation of additivity of nucleons in the absorption of virtual photons by atomic nuclei. In this paper we analyze the experimental data on the hadron-nuclei interaction cross sections in search for similar effects in the scattering of hadrons on nuclei. Specifically, we look for deviations from predictions of the multiple scattering theory. We formulate, and make extensive use of the Glauber-Bribov universality of the hadron-nucleus interaction cross sections, which makes it possible to check in a unique way a consistency of the experimental data on the total, inelastic and absorption cross sections for all the incident hadrons. We find evidence for the effective cross section of interaction with bound nucleons being 5–15% larger than with free nucleons. We comment on implications of this observation for models of the EMC effect.     

Growth of nuclear spin precession frequency of antiprotons (negative hyperons) under deceleration in matter with polarized nuclei

The Coulomb interaction leads to an increase of the real part of the amplitude of scattering of negatively charged particles (antiprotons, hyperons) by nuclei. In consequence, when antiprotons (negative hyperons) are decelerated in a medium with polarized nuclei, their effective energy of interaction with the medium and the nuclear spin precession frequency in a pseudomagnetic field grow as the particles decelerate. As a result, spin rotation of negatively charged particles becomes observable despite their rapid deceleration. This provides information about the spin-dependent part of the amplitude of coherent elastic zero-angle scattering in the range of low energies, where scattering experiments are practically impossible to perform.     

Bremsstrahlung of ultrarelativistic deuterons in the field of the nucleus

We consider the differential cross section for bremsstrahlung of ultrarelativistic deuterons subject to diffraction scattering by nuclei. By comparison of the approximate formulas obtained here with exact numerical calculations, the region of applicability of the approximate formulas is discussed.Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 2, pp. 16–19, February, 1987.     

Diffractional Nuclear Processes Involving Composite Particles

The diffractional picture of nuclear processes at high energies involving composite particles is given. The solution of the Lippmann-Schwinger equation for the problem on scattering in the scattering center systems is considered in the high-energy approximation. The general formulas for the cross section of different diffractional processes with particle transmission are obtained. The effects of multiple scattering and their mutual compensation are discussed. The applicability conditions of the diffractional approach are discussed. The diffractional processes during the interaction of high-energy deuterons with nuclei are considered in detail. Without the assumption of deuteron size smallness compared to nuclear size, the cross sections of different diffractional processes are calculated with nuclear boundary diffusion taken into account. The nonmonotonic dependence of the diffractional disintegration cross section for deuterons on the mass number is shown due to the influence of nuclear boundary diffusion. The role of the diffractional and the Coulomb mechanisms of interaction depending on the nuclear mass number is discussed. The calculated dependences are compared with experimental data. The interference during the multiple scattering and its relationship with the diffractional structure of the angular scattering during the scattering on the composite systems are considered. The comparison the between diffractional approximation and different variations of the impulse approximation is made.     

Sub-barrier interaction between deuterons and 58, 62Ni nuclei

The interaction between deuterons and ^{58, 62}Ni nuclei at energies of E _d = 3.5, 4.5 and 5.16 MeV is investigated. The discrepancy between measured scattering elastic cross section and the Rutherford ones is higher than the value calculated theoretically by considering deuterons polarization and Coulomb breakup. Analysis of measured cross section of ^{58, 62}Ni(d, p) reaction and the results of calculation of Coulomb breakup cross section integrated over neutron emission angles shows that that the dominant mechanism of proton formation is the reaction of neutron transfer to the target nucleus.     

Generation of high-energy photons with large orbital angular momentum by compton backscattering

Usually, photons are described by plane waves with a definite 4-momentum. In addition to plane-wave photons, "twisted photons" have recently entered the field of modern laser optics; these are coherent superpositions of plane waves with a defined projection hm of the orbital angular momentum onto the propagation axis, where m is an integer. In this Letter, we show that it is possible to produce high-energy twisted photons by Compton backscattering of twisted laser photons off ultrarelativistic electrons. Such photons may be of interest for experiments related to the excitation and disintegration of atoms and nuclei, and for studying the photoeffect and pair production off nuclei in previously unexplored experimental regimes.     

7Li quasi-free scattering off the α-cluster in 9Be nucleus

Spectra of coincident charged particles from the reactions induced by a 52 MeV ⁷Li beam incident on a beryllium target were measured. Strong contributions of the ⁷Li quasi-free scattering off the α-cluster in ⁹Be nucleus were observed. This observation supports the conclusions from the study of complete fusion of weakly bound light nuclei at low energies that the “fragility” of the nuclei makes their fusion less probable. Received: 1 June 1998     

Excitation of states of medium-mass nuclei in the region of giant resonances in inelastic deuteron scattering

Results are presented that were obtained by measuring a continuum in the inelastic scattering of 37-MeV deuterons on ¹²C, ⁴⁸Ti, and ^58,64Ni nuclei in the angular range 16° ≤ θ ≤ 61°. Broad excitation maxima are found for deuteron scattering angles in the range θ ≤ 21°. The region of a broad maximum includes giant resonances of target nuclei, whose levels are excited quite readily at E _d = 37 MeV. Summation of the inelastic-scattering cross sections over all final states of the excited| nucleus and the use of completeness of the wave functions for these states make it possible to express the total cross section for inelastic (incoherent) deuteron scattering only in terms of the wave functions for the ground state of the target nucleus. The corresponding quasielastic-scattering amplitude is taken in the diffraction approximation. Nucleon correlations in the target nucleus are disregarded. Upon disregarding a small contribution of multiple quasielastic scattering at small scattering angles, the cross section for incoherent deuteron scattering is represented approximately as the product of known factors—the square of the absolute value of the amplitude for diffractive quasielastic scattering and the effective number of target nucleons scattering deuterons. The results of these calculations agree qualitatively with experimental data.     

Comment on isospin mixing in nuclei

The central collisions of 70 GeV/c protons with Ag, Br and Pb nuclei have been studied, with the help of BR-2 photoemulsion and emulsion of the same constitution loaded with Pb nuclei. It is shown that the average multiplicity of produced particles (s-particles) increases slowly with increasing the atomic weight of the target nucleus. The ratio of the average multiplicity for these particles to the average charged particle multiplicity for protonproton interactions equals 3.2 forp-Ag, Br and 3.5 forp-Pb. The average multiplicities of particles from nuclear disintegration with energies for protons from 26 up to 400 MeV (g-particles) are 14.2±0.8 forp-Ag, Br and 23.0±1.0 forp-Pb corresponding to the emission of about half of all nucleons from the nucleus at the first rapid stage of interaction. The difference of thes-particle pseudorapidity distributions forp-Ag, Br, Pb andp-p interactions at pseudorapidities larger than 4.2 can be explained by successive interactions of the incident proton with nucleus nucleons.     

Active polarized target: Measurement of proton spin polarizabilities

The static (electric and magnetic) polarizabilities of the proton are known from measurements of low-energy Compton scattering of real photons. However, no experimental data are so far available about its spin polarizabilities, which describe the response of the proton spin to a varying electromagnetic field. These fundamental structure constants can be obtained in the most model-independent way from measurements of double-polarized Compton scattering at energies below the pion threshold using a polarized photon beam and a polarized proton target. An active polarized target based on polystyrene doped with a scintillator allows recoil protons to be detected directly in the target material, background from the coherent Compton effect on heavier nuclei (¹²C etc.) to be eliminated and precise data on spin polarizabilities to be obtained.     

Angular and energy distributions of grey particles in high-energy hadron-nucleus collisions

The angular and energy distributions of grey particles (mostly protons in the energy range 30–400 MeV) emitted in the interactions of high energy hadrons with nuclei are investigated here. Grey particles “g particles” are assumed to result from the intranuclear cascade initiated by the passage of the incident hadron through the target nucleus. Using the pretested hypothesis that these particles arise only from the first two generations of the cascade, we calculate their angular and energy distributions. Various experimental data are successfully described both in shape and absolute magnitude.     

Quasi-free inclusive processes in the two-particle splitting of tritons by deuterons with an energy of 37 MeV

The d + t → d + d + n reaction was experimentally and theoretically investigated at an incident deuteron energy of 36.9 MeV. The experiment was performed on the U-240 isochronous cyclotron at the Institute for Nuclear Research, National Academy of Sciences of Ukraine. Inclusive spectra of deuterons and their angular distributions in the range of 15° ≤ θ_d ≤ 52° were measured. Experimental spectra and angular distributions of the final deuterons from the d + t → d + d + n reaction are satisfactorily described in a diffraction approximation that considers interaction in the final state and the correct asymptotic of the wave function of colliding nuclei. The scattered deuterons are the main contributors to the cross section (up to 70–90%), while the deuterons from tritons can be seen well only at low and high energies, at the edges of the spectra.     

Interaction between ultra short pulses and a dense scattering medium by Monte Carlo simulation: consideration of particle size effect

With an enough short-pulse incident to an individual particle, elementary scattering modes can be observed: internal or external reflection, refraction and diffraction. Simulation of pulse propagation in dense scattering medium is usually computed for large observation time, so that time delays of pulse interaction with the particles are negligible compared to propagation times between particle. A Monte Carlo method is proposed to compute the propagation of an incident 100 fs laser pulse in dense medium taking into account time-dependent scattering characteristics of particle: observation time of scattered light is less than 5000 fs. Two extreme cases are exemplified: predominance of direct and single-scattered photons appears in a thin time window for small particles (1 μm). On the contrary multiple scattering is always predominant and scrambles the transmitted signal for large particles (100 μm).     

Inelastic interactions with deuterons at very high energies

Cross sections for inelastic reactions of hadrons, photons and leptons with deuterons are derived from the Coherent Tube Model for particle-nucleus collisions. Predictions are compared with recent experimental data. Good agreement between experiments and theory is demonstrated.     

Fast helium nuclei in interactions induced by very heavy nuclei

Fast helium nuclei emitted in interactions between heavy cosmic ray nuclei (12≦Z≦26) and photoemulsion nuclei at energies >1 GeV/nucleon have been studied. Comparisons with interactions where the incident particles are protons, pions or light nuclei reveal some characteristic features of nucleus-nucleus interactions. The frequency of fast target helium nuclei is much larger and the high energy tail of the energy spectrum of these helium nuclei is more pronounced in nucleus-nucleus interactions than in proton-nucleus and pion-nucleus interactions. The number of helium nuclei emitted depends on the size and disintegration of the interacting nuclei. In order to explain our experimental data several possible production mechanisms have to be considered. Some characteristics of the emission of multiply-charged projectile fragments have-also been studied.