Helium production from 84Kr-- and 197Au--emulsion interactions at high energies

The properties of the relativistic helium fragments produced in interactions of 84 Kr at 1.8 A GeV and 197 Au at 10.7 A GeV in emulsion are investigated. The experimental results are compared with those obtained from various projectiles with emulsion collisions at different energies. It is found that the multiplicity distribution of helium projectile fragments (HPFs) is well described by the Koba-Nielsen-Olesen (KNO) scaling presentation. The second Mueller moment f 2 of the HPF multiplicity distribution is independent of the projectile energy for the same projectile, but it is dependent on the projectile mass number. The value of f 2 increases with the increase of projectile mass number A p . The negative value of f 2 , when A p < 69, means that the emission of HPFs is anticorrelated, but positive value of f 2 , when A p > 69, refers to that the emission of HPFs is correlated. The non-zero f 2 moment in this experiment implies the strong correlation existing between the HPFs.     

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.     

System size dependence in backward relativistic hadron production in pA and AA collisions

Abstract： In this comprehensive study the multiplicity characteristics of the backward emitted relativistic hadron （shower particle） through hadron-nucleus and nucleus-nucleus are overviewed in three dimensions. These dimensions are the projectile size, target size, and energy. To confirm the universality in this production system, wide ranges of system size and energy （Elab～2.1 A up to 200 A GeV） are used. The multiplicity characteristics of this hadron imply a limiting behavior with respect to the projectile size and energy. The target size is the main effective parameter in this production system. The exponential decay shapes is a characteristic feature of the backward shower particle multiplicity distributions. The decay constant changes with the target size to be nearly 2.02, 1.41, and 1.12 for the interactions with CNO, Era, and AgBr nuclei, respectively, irrespective of the projectile size and energy. While the backward production probability and average multiplicity are constants at different projectile sizes and energies, they can be correlated with the target size in power law relations.     

Electromagnetic dissociation of 3.7 A GeV^16O in nuclear emulsion

The electromagnetic dissociation (ED) of 3.7 A GeV {}^{16}O in nuclear emulsion is investigated with high statistics. It is found that the electromagnetically dissociated cross section increases with increasing beam energy, the charge distribution of projectile fragments is the same as the results at 60 and 200 A GeV, and the production probability of projectile fragments with charge 3≤Z≤5 is less than that of the other projectile fragments. These results can be well explained by use of Weizsacker and Williams method for calculating the ED contributions. The percentile abundance of various decay modes for ED at 3.7 A GeV is close to the result at 60 and 200 A GeV, but it is different from the result at 14.6 A GeV. The ED of 3.7 A GeV is mainly caused by the giant dipole and quadrupole resonance of E1 and E2, which can be qualitatively explained by the multiplicity distribution of projectile proton in ED. The multiplicity distribution of the α fragments in ED and nuclear events have different functional forms. This difference may be a consequence of the different reaction mechanism involved.     

500 AMeV 56Fe诱发乳胶核反应弹核碎裂研究

通过利用日本放射线医学综合研究所( NIRS ) 重离子医用加速器( HIMAC) 产生的束流照射国产的核-4型原子核乳胶,对500 AMeV 56Fe诱发乳胶核反应粒子产生进行了研究。讨论了500 AMeV 56Fe诱发乳胶核反应弹核碎片的多重数分布,并与其他结果进行了比较。结果表明,弹核碎片平均多重数随靶核质量的增加而增加,与入射能量无关。A stack of domestic N-4 nuclear emulsion was exposed to 56Fe ions at 500 AMeV at the HIMAC of NIRS. Particle production was investigated in 56Fe-Em interactions. The multiplicity distribution of projectile fragments was given in this paper and compared with other experimental results of heavy ion induced nuclear reactions in nuclear emulsion. The results show that the multiplicity of projectile fragments increase with the increasing target mass, and thereis no dependence on the projectile energy.     

System size dependence in backward relativistic hadron production in pA and AA collisions

In this comprehensive study the multiplicity characteristics of the backward emitted relativistic hadron(shower particle) through hadron-nucleus and nucleus-nucleus are overviewed in three dimensions. These dimensions are the projectile size, target size, and energy. To confirm the universality in this production system, wide ranges of system size and energy(Elab ～2.1 A up to 200 A GeV) are used. The multiplicity characteristics of this hadron imply a limiting behavior with respect to the projectile size and energy. The target size is the main effective parameter in this production system. The exponential decay shapes is a characteristic feature of the backward shower particle multiplicity distributions. The decay constant changes with the target size to be nearly 2.02, 1.41, and 1.12 for the interactions with CNO, Em, and Ag Br nuclei, respectively, irrespective of the projectile size and energy. While the backward production probability and average multiplicity are constants at different projectile sizes and energies, they can be correlated with the target size in power law relations.     

Shell Evolution Study for New Magic Number N =32 via Isochronous Mass Spectrometry

Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed.     

Prompt neutron multiplicity distribution for ~（235）U（n,f） at incident energies up to 20 MeV

For the n+²³⁵U fission reaction, the total excitation energy partition of the fission fragments, the average neutron kinetic energy <ε>(A) and the total average energies E_γ(A) removed by γ rays as a function of fission fragment mass are given at incident energies up to 20 MeV. The prompt neutron multiplicity as a function of the fragment mass, ν(A), for neutron-induced fission of ²³⁵U at different incident neutron energies is calculated. The calculated results are checked with the total average prompt neutron multiplicities ν and compared with the experimental and evaluated data. Some prompt neutron and γ emission mechanisms are discussed.     

Inclusive Photoproduction of Υ(1s) and J/ψ in Ultra-peripheral p-Pb Collisions at s~(1/2) = 5.5 TeV

With a photon spectrum of high energy charged partons, both differential and total cross sections of J/ψ√andΥ(1s) inclusive photoproduction in ultra-peripheral p-Pb Collisions (UPCs) at s=5.5 Te V are given. A direct photon process and a resolved photon process including fragment and non-fragment contributions are considered. The total cross section is compared to the inelastic production results in coherent p-Pb collisions at the same center-of-mass energy. Our results seem non-negligible.     

Solvent effects on the S0→S2 absorption spectra of β-carotene

Absorption spectra of β-carotene in 31 solvents are measured in ambient conditions. Solvent effects on the 0-0 band energy, the bandwidth, and the transition moment of the S 0 → S 2 transition are analysed. The discrepancies between published results of the solvent effects on the 0-0 band energy are explained by taking into account microscopic solute-solvent interactions. The contributions of polarity and polarizability of solvents to 0-0 band energy and bandwidth are quantitatively distinguished. The 0-0 transition energy of the S 2 state at the gas phase is predicted to locate between 23000 and 23600 cm-1 .     

Projectile spectator proton production in 84Kr- emulsion interactions at 1.7 A GeV

The multiplicity distribution of projectile protons and multiplicity correlations between black particles, grey particles, shower particles, compound particles, heavily ionized track particles, projectile helium fragments and projectile spectator protons in ⁸⁴Kr-emulsion collisions at 1.7 A GeV are investigated. It is found that the projectile spectator proton multiplicity distribution becomes broader with increasing target mass. The average multiplicity of shower particles and compound particles strongly depends on the number of projectile spectator protons, but the average multiplicity of black particles, grey particles and heavily ionized track particles weakly depends on the number of projectile spectator protons. The average multiplicity of projectile helium fragments increases linearly with increasing numbers of projectile spectator protons. Finally, the multiplicity distribution of projectile spectator protons obeys a KNO type of scaling law.     

Intermediate Mass Dileptons from the Passage of Jets and High Energy Photons through Quark-Gluon Plasma

The production of the intermediate mass dileptons originating from the annihilation and Compton scattering of the jets and high energy photons （resolved photons） passing through the quark-gluon plasma is calculated. The contribution of the dilepton yield due to the jet-plasma and high energy photon-plasma interaction is pronounced compared to the thermal and Drell-Yan dilepton spectrum at intermediate mass. The ordinary spectrum of thermal and Drell-Yan processes is enhanced by the jet and photon-plasma mechanism. The numerical results match to the PHENIX data accurately in the intermediate mass region for Au-Au 200 GeV/A collisions at RHIC.     

290 AMeV 12C诱发乳胶核反应末态粒子多重数关联

对290 AMeV 12C诱发乳胶核反应末态粒子间的多重数关联进行了研究。实验结果表明:黑径迹粒子、灰径迹粒子、重电离粒子多重数之间存在较强的关联,而且黑径迹粒子和重电离粒子多重数有饱和的趋势,这些特征与高能区实验结果一致;簇射粒子与其他粒子间的关联性较弱,这一特征与高能区实验结果不同,主要归因于弹核能量较低、簇射粒子产额较小;黑径迹粒子、灰径迹粒子在前后半球的平均多重数随靶核的增大而增加;实验结果可用基于碰撞几何的旁观体-反应体模型及级联蒸发模型来解释。We have investigated the multiplicity correlation of particles produced in 12C-emulsion interactions at 290 AMeV. It is found that there is a strong correlation between black track particle, grey track particle and heavily ionized track particle, and finally black track particles and heavily ionized track particles tend to saturation, which is the same as the experimental results observed at high energies. The multiplicity correlation between shower particle and other particles is weaker, which is different from the experimental results observed at high energies. This discriminating character can be explained by the lower energy of projectile. The productivity of shower particle is lower at intermediate energies compared to that at high energies. The forward-backward averaged multiplicity of black track particle and grey track particle increases with the increasing target size.     

Approximate calculation of electronic energy levels of axially symmetric quantum dot and quantum ring by using energy dependent effective mass

Calculations of electronic structures about the semiconductor quantum dot and the semiconductor quantum ring are presented in this paper. To reduce the calculation costs, for the quantum dot and the quantum ring, their simplified axially symmetric shapes are utilized in our analysis. The energy dependent effective mass is taken into account in solving the Schr?dinger equations in the single band effective mass approximation. The calculated results show that the energy dependent effective mass should be considered only for relatively small volume quantum dots or small quantum rings. For large size quantum materials, both the energy dependent effective mass and the parabolic effective mass can give the same results. The energy states and the effective masses of the quantum dot and the quantum ring as a function of geometric parameters are also discussed in detail.     

Systematic Study on System Size Dependence of Global Stopping: Role of Momentum-Dependent Interactions and Symmetry Energy

Using the isospin-dependent quantum molecular dynamical model, we systematically study the role of symme- try energy with and without momentum-dependent interactions on the global nuclear stopping. We simulate the reactions by varying the total mass of the system from 80 to 394 at different beam energies from 30 to 1000 Me V/nucleon over central and semi-central geometries. The nuclear stopping is found to be sensitive towards the momentum-dependent interactions and symmetry energy at low incident energies. The momentum-dependent interactions are found to weaken the finite size effects in nuclear stopping.     

Projectile fragment emission in the fragmentation of 56Fe on C,Al and CH2 targets at 471 A MeV

The emission angle and the transverse momentum distributions of projectile fragments produced in the fragmentation of 56Fe on CHs, C and A1 targets at 471 A MeV are measured. It is found that for the same target, the average value and width of the angular distribution decrease with an increase of the projectile fragment charge; for the same projectile fragment, the average value of the distribution increases and the width of the distribution decreases with increasing the target charge number. The transverse momentum distribution of a projectile fragment can be explained by a single Gaussian distribution and the averaged transverse momentum per nucleon decreases with the increase of the charge of projectile fragment. The cumulated squared transverse momentum distribution of a projectile fragment can be explained well by a single Rayleigh distribution. The temperature parameter of the emission source of the projectile fragment, calculated from the cumulated squared transverse momentum distribution, decreases with the increase of the size of the projectile fragment.     

Solvent effects on the S0→S2 absorption spectra of β-carotene

Absorption spectra of β -carotene in 31 solvents are measured in ambient conditions. Solvent effects on the 0--0 band energy, the bandwidth, and the transition moment of the S₀ → S₂ transition are analysed. The discrepancies between published results of the solvent effects on the 0--0 band energy are explained by taking into account microscopic solute-solvent interactions. The contributions of polarity and polarizability of solvents to 0--0 band energy and bandwidth are quantitatively distinguished. The 0--0 transition energy of the S₂ state at the gas phase is predicted to locate between 23000 and 23600~cm^-1.     

Correlation effects on the energy spectra of quantum dot electrons with harmonic model interactions

The low lying excitation energy spectra of two, three and five quantum dot electrons with harmonic model interactions in a large magnetic field are calculated by the Hartree Fock(HF) methods. Correlation effects on the energy level structures are investigated by comparing the HF results with the exact ones. It is found that the pure collective excitations(center of mass mode quanta) existing in the exact energy spectra do not appear in the HF energy spectra. The degeneracies of energy levels are also re...     

Multiparticle azimuthal correlations in central nucleus-nucleus collisions at high energy

Multiparticle azimuthal correlations in central nucleus-nucleus collisions at high energy are described by a simple formula. The calculated results are in agreement with the experimental data of carbon and oxygen induced interactions at Dubna energy. The comparison between the calculated results and experimental data shows that particles are emitted isotropically in the rest frame of the emission sources, and the emission sources have movements in momentum space.     

The direct ionization processes in the collisions of partially stripped carbon and oxygen ions with helium atoms at low-to-intermediate energies

The values of direct double- to-single ionization ratio R of helium atoms induced by C^q＋, O^q＋ （q = 1 -4） ions at incident energies from 0.2 to 8.5MeV are measured. Based on the existing model （Shao J X, Chen X M and Ding B W 2007 Phys. Rev. A 75 012701） the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms. The results calculated from our ＂effective charge＂ model are in good agreement with the experimental data, and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively.