Transverse Momentum Distributions of Charged Particles Produced in Deuteron-Carbon Interactions at 4.2A GeV/c

In this work, the behavior of transverse momentum (p_T) and maximum p_T (p_Tmax) distribution of light-flavored hadrons, produced in deuteron-carbon (dC) interactions at 4.2A GeV/c, is presented. We use the data, provided by the Laboratory of High Energy (LHE) with propane bubble chamber of 2 m of the Joint Institute for Nuclear Research (JINR), Dubna Russia. The results of the experimental data are compared with the predictions of the cascade model, Dubna version. Three regions in terms of the p_T-distributions trend are observed for all types of particles, where p_T ～ 1 and 1.5 GeV/c are the limiting values for pions and protons, respectively, in the region-III, for which the p_T > 0.375 GeV/c. The protons’ contribution to this region is an order of magnitude more than of the mesons and the distribution of the latter decreases faster than of the former. The model cannot predict the experimental results in the region-III, completely, where the number of particles is less than in the experiment.     

Transverse Momentum Distributions of Charged Hadrons Produced in He12C Collisions at 4.2A GeV/c

Physics of Particles and Nuclei Letters - We study the trend of transverse momentum (pT) and maximum transverse momentum (pTmax) distributions of pions and protons in He12C-interactions at 4.2A...     

Evolution of Airy structure in <Superscript>12</Superscript>C(<Superscript>12</Superscript>C, <Superscript>12</Superscript>C)<Superscript>12</Superscript>C between 5 and 10 MeV/A

We investigate the properties of a global optical potential, which describes the ¹²C + ¹²C elastic-scattering data between 70 and 130 MeV, within the nearside/farside and barrier-wave/internal-wave decomposition techniques. Particular emphasis is laid on the discussion of the incomplete absorption features of this system, and especially on the properties of the Airy minima which are observed in the experimental excitation function. The complicated angular and energy evolution of the data is explained in terms of the interference of a small set of scattering subamplitudes with a much simpler behavior.Received: 2 September 2003, Revised: 25 September 2003, Published online: 5 February 2004PACS: 24.10.-i Nuclear reaction models and methods - 24.10.Ht Optical and diffraction models - 25.70.Bc Elastic and quasielastic scattering     

New results from the HAPPEX Experiments at Q<Superscript>2</Superscript> = 0.1GeV/c<Superscript>2</Superscript>

The nucleon's strange electric and magnetic form factors G _E ^s and G _M ^s can be probed via parity-violating electron scattering. The HAPPEX Collaboration has made new measurements of the parity-violating asymmetry A _PV in elastic scattering of 3GeV electrons off hydrogen and ⁴He targets with 〈θ_lab〉 ≈ 6.0^° . For ⁴He the preliminary result is A _PV = (+ 6.43±0.23(stat)±0.22(syst))×10^-6 . For hydrogen the preliminary result is A _PV = (- 1.60±0.12(stat)±0.05(syst))×10^-6 . From these values we extract G ^s _E = 0.004±0.014±0.013 at 〈Q ²〉 = 0.077 GeV/c^2 , and G ^s _E +0.09G ^s _M = 0.004±0.011±0.005 at 〈Q ²〉 = 0.109 GeV/c^2 , both consistent with zero, providing stringent new limits on the role of strange quarks in the vector structure of the nucleon.     

400GeV/c pp碰撞产生粒子的方位角结构

利用不同的方法对400GeV/c pp碰撞多重产生的方位角结构进行了研究.一维和二维标度阶乘矩的分析结果表明两维时的间歇效应较强,这与“喷注形”多粒子产生机制是不矛盾的. 但由其它方法分析结果表明方位角结构似乎具有随机的性质,没有“喷注形”多重产生机制的证据.     

Study of the isobar configurations in the <Superscript>12</Superscript>C and <Superscript>16</Superscript>O ground states

Experimental research on positive-pion photoproduction on the oxygen nucleus in the ¹⁶O(γ, π⁺p) reaction at high recoil momenta of the residual nuclear system was performed. The yield for the ¹⁶O(γ, π⁺p) reaction was analyzed using a model that takes Δ-isobar configurations in nuclei ground states into account, together with the earlier-measured yield of the¹²C(γ, π⁺p) reaction. The estimated number of isobars per nucleon N _Δ = 0.012 ± 0.005 was obtained for the ¹²C nucleus, and ¹⁶O N _Δ = 0.018 ± 0.004 was obtained for the ¹⁶O nucleus.     

4.5AGeV/c 24Mg与核乳胶碰撞中簇射粒子的赝快度分布

报道了4.5AGeV/c ²⁴Mg与核乳胶碰撞中产生的簇射粒子的赝快度分布,结果表明,分布宽度和峰值位置明显依赖于靶核尺寸.用柱模型对赝快度分布进行了分析,MonteCarlo方法计算得到的结果基本符合实验数据的走向,并重现了实验数据中的涨落现象.     

Study of the Involvement of <Superscript>8</Superscript>Be and <Superscript>9</Superscript>B Nuclei in the Dissociation of Relativistic <Superscript>10</Superscript>C, <Superscript>10</Superscript>B,and <Superscript>12</Superscript>C Nuclei

The results obtained by estimating the contribution of 8Be and 9B nuclei to the coherent dissociation of ¹⁰C, ¹⁰B, and ¹²C relativistic nuclei in nuclear track emulsions (“white” stars) are presented. The selection of white stars accompanied by 9B leads to a distinct peak appearing in the distribution of the excitation energy of 2α2p ensembles and having a maximum at 4.1 ± 0.3 MeV. A 8Be nucleus manifests itself in the coherent-dissociation reaction ¹⁰B → ²He + H with a probability of (25 ± 5)%, (14 ± 3)% of it being due to 9B decays. The ratio of the branching fractions of the ⁹B + n and ⁹Be + p mirror channels is estimated at 6 ± 1. An analysis of the relativistic dissociation of ¹²C nuclei in a nuclear track emulsion revealed nine 3α events corresponding to the Hoyle state.     

Analysis of <Superscript>8</Superscript>B Proton Halo Nucleus Scattered from <Superscript>12</Superscript>C and <Superscript>58</Superscript>Ni at Different Energies

Angular distributions in the elastic scattering of ⁸B from ¹²C and ⁵⁸Ni targets at different energies have been analyzed in the framework of the double-folding (DF) optical model. The real central part of the nuclear optical potential is obtained by folding the M3Y effective interaction with the cluster density distribution of the ⁸B nucleus. The experimental angular distributions have been successfully reproduced. This confirms the validity of the cluster structure of the ⁸B nucleus.     

e<Superscript> + </Superscript>e<Superscript>-</Superscript>-pair production in Pb-Au collisions at 158 GeV per nucleon

We present the combined results on electron-pair production in 158 GeV/n Pb-Au ( = 17.2 GeV) collisions taken at the CERN SPS in 1995 and 1996, and give a detailed account of the data analysis. The enhancement over the reference of neutral meson decays amounts to a factor of 2.31 for semi-central collisions (28 ) when yields are integrated over m > 200 MeV/c² in invariant mass. The measured yield, its stronger-than-linear scaling with , and the dominance of low pair p_t strongly suggest an interpretation as thermal radiation from pion annihilation in the hadronic fireball. The shape of the excess centring at 500 MeV/c², however, cannot be described without strong medium modifications of the meson. The results are put into perspective by comparison to predictions from Brown-Rho scaling governed by chiral symmetry restoration, and from the spectral-function many-body treatment in which the approach to the phase boundary is less explicit.Received: 2 March 2005, Published online: 8 June 2005     

Light-charged-particle emission from hot <Superscript>32</Superscript>S<Superscript>*</Superscript>formed in <Superscript>20</Superscript>Ne + <Superscript>12</Superscript>C reaction

Inclusive energy distributions for light charged particles (p , d , t and have been measured in the ²⁰Ne (158, 170, 180, 200 MeV) + ¹²C reactionsintheangularrange$10^°$ - - $50^°$.Exclusivelight-charged-particleenergydistributionmeasurementswerealsodoneforthesamesystemat158 MeVbombardingenergybyin - planelightchargedparticle - - fragmentcoincidence.Pre - equilibriumcomponentshavebeenseparatedoutfromprotonenergyspectrausingthemovingsourcemodelconsideringtwosources.ThedatahavebeencomparedwiththepredictionsofthestatisticalmodelcodeCASCADE.Ithasbeenobservedthatsignificantdeformationeffectswereneededtobeintroducedinthecompoundnucleusinordertoexplaintheshapeoftheevaporated$d$,$t$energyspectra.Forprotons, evaporatedenergyspectrawereratherinsensitivetonucleardeformation, thoughangulardistributionscouldnotbeexplainedwithoutdeformation.Thedecaysequenceofthehot$³²S$nucleushasbeeninvestigatedthroughexclusivelight - - charged - particlemeasurementsusingthe$²⁰Ne$$(158 MeV) + $¹²C reaction. Information on the sequential decay chain has been extracted through a comparison of the experimental data with the predictions of the statistical model. It is observed from the present analysis that exclusive light-charged-particle data may be used as a powerful tool to probe the decay sequence of hot light compound systems.     

Study of the <Superscript>12</Superscript>C (<Superscript>8</Superscript>B, <Superscript>7</Superscript>Be)<Emphasis Type="Italic">X</Emphasis> knockout reaction at intermediate energies

The breakup reactions of ⁸B on a ¹²C target at 142, 285, 790, and 936MeV/nucleon have been studied. One-proton-removal cross sections, leading to the production of ⁷Be fragments in the ground and first excited states (at 0.429MeV), and the longitudinal momentum distributions of the ⁷Be fragments are obtained in the Eikonal approximation of the Glauber Model. The results of the calculations including the contribution of the ⁷Be to the ground and first excited states of ⁸B are compared with the available experimental data. One-proton-removal cross section for the ¹²C(⁸B, ⁷Be)X knockout reaction at 142, 285, 790, and 936 MeV/nucleon energy has been calculated. ⁸B and ⁷Be cross sections and momentum distribution are in a good agreement with available data.     

Description of elastic scattering in the <Superscript>16</Superscript>O + <Superscript>16</Superscript>O and <Superscript>16</Superscript>O + <Superscript>12</Superscript>C systems

The objective of the present study was to describe more precisely experimental data on elastic scattering in the ¹⁶O + ¹⁶O system at E _lab = 124, 145, 250, 350, and 480 MeV and in the ¹⁶O + ¹²C system at E _lab = 132, 170, 181, 200, 230, 260, and 281 MeV. The role of exchange interaction in the region of backward angles is investigated. The coefficient of incompressibility of nuclear matter is estimated at K = 205 MeV ± 15%.     

Interaction of <Superscript>12</Superscript>C ions with nuclei of enriched tin isotopes at an energy of 2.2 GeV per nucleon

The formation cross sections for about 110 products of interaction between a ¹²C ion beam of energy 2.2 GeV per nucleon and tin targets from the isotopes ^{112,118,120,124}Sn were calculated. Massyield and charge distributions were obtained for ^112,118,124Sn targets. An analysis of these charge distributions reveals that the positions of their maxima, Z _p , are different for targets having different nucleon compositions. The formation cross sections for neutron-rich products originating from neutron-rich targets are found to increase in all product-mass regions considered in our study. Mass distributions are compared for proton-, deuteron- and ion-nucleus reactions.     

Semiclassical description of the <Superscript>6</Superscript>He+<Superscript>12</Superscript>C elastic scattering

The results of the elastic scattering of ⁶He+¹²C systemat E _Lab = 18 MeV by using the barrier and internal wave decomposition of the S-matrix element within the framework of the WKB method are presented. This is the first detailed study for the interaction of the exotic ⁶He nucleus on different stable nuclei by using a semiclassicalmethod. In this paper, we show that in order to obtain the elastic scattering cross section of the ⁶He+¹²C systemat energies close to the Coulomb barrier, it is vitally important to take into account the inner complex turning points in the calculations and the tunneling effects play a crucial role to explain the experimental data. The semiclassical results are compared with the experimental data as well as the quantum-mechanical one.     

<Superscript>6</Superscript>He + <Superscript>6</Superscript>He Clustering of <Superscript>12</Superscript>Be in a Microscopic Algebraic Approach

The norm kernel of the A=12 system composed of two ⁶He clusters, and the L=0 basis functions (in the SU(3) and angular momentum-coupled schemes) are analytically obtained in the Fock-Bargmann space. The norm kernel has a diagonal form in the former basis, but the asymptotic conditions are naturally defined in the latter one. The system is a good illustration for the method of projection of the norm kernel to the basis functions in the presence of SU(3) degeneracy that was proposed by the authors. The coupled-channel problem is considered in the algebraic version of the resonating-group method, with the multiple decay thresholds being properly accounted for. The structure of the ground state of ¹²Be obtained in the approximation of zero-range nuclear force is compared with the shell-model predictions. In the continuum part of the spectrum, the S-matrix is constructed, the asymptotic normalization coefficients are deduced and their energy dependence is analyzed.     

Pseudorapidity Distribution of Shower Particles in 24Mg-Emulsion Collisions at 4.5A GeV/c

The pseudorapidity distribution of shower particles produced in the ²⁴Mg-emulsion collisions at 4.5A GeV/c is reported in this paper. The dependences of the distribution width and the peak position on the target size are observed.The pseudorapidity distribution of shower particles for the events with low target multiplicity (light target) is narrower than that with high target multiplicity (heavy target). The maximum probability pseudorapidity for light target is greater than that for heavy target. The experimental data is analyzed by using the cylinder model suggested by Liu et al. The Monte Carlo results based on Liu's cylinder model are approximately in agreement with the experimental tendency and fluctuation.     

Diffractive scattering of <Superscript>7</Superscript>Be and <Superscript>8</Superscript>B nuclei by <Superscript>12</Superscript>C nuclei

A theory of the diffractive scattering of loosely bound three-cluster nuclei by nuclei was developed with allowance for Coulomb interaction. The differential cross sections for the scattering of projectile exotic nuclei ⁷Be and ⁸B by ¹²C nuclei at an energy of 40 MeV per nucleon were calculated within the proposed formalism. The results describe satisfactorily relevant experimental data.