A search for charmed particles originating from the interactions of 300 GeV/c protons in emulsion nuclei

The associated production of charmed particles by the interactions of 300 GeV/c protons with complex nuclei has been sought using nuclear emulsions. The failure to observe any candidates for this process among some 60,000 interactions investigated implies, provided charmed particles lifetimes are in the range 10^?12 to 10^?14 s, a cross section for their associated production by the interactions of 300 GeV/c protons with nucleons of less than 1.5 microbarns at a 90% confidence level.     

Intermittency of Target Fragments in ^16O-AgBr Collisions at 4.5 A GeV/c

We report the angular distributions of grey and black particles produced in ^16O-AgBr interactions at 4.5 A GeV/c in nuclear emulsion. Intermittency and fractal behaviour are studied for emission spectra of target associated grey and black particles. Intermittent behaviour is observed for both grey and black particles. In both the cases, anomalous dimensions are seen to increase linearly with the order of moments, thereby indicating the association of multifractility with production mechanism of both grey and black particles.     

Polarizations of spin 32 particles and 7Li58Ni interactions

New representations of polarizations of spin $\text{3}\text{2}$ particles are proposed for elastic scattering. They are useful in investigating spin-dependent interactions. The application to ⁷Li⁵⁸Ni scattering gives weak spin-orbit interactions and rather strong tensor ones of ⁷Li.     

Multiplicities of forward-backward particles in16O-emulsion interactions at 4.5 AGeV/c

An exclusive study of the characteristics of interactions accompanied by backward emission (θlab≥ 90°) of shower and grey particles in collisions of a 4.5 AGeV/c 16O beam with emulsion nuclei is carried out. The experimental multiplicity distributions of different particles emitted in the forward (θlab<90°) and backward hemispheres due to the interactions with the two emulsion components (CNO, AgBr) are presented and analyzed. The correlations between the different emitted particles are also investigated. The results indicate that there are signatures for a collective mechanism, which plays a role in the production of particles in the backward hemisphere. Hence, the backward multiplicity distribution of the emitted shower and grey particles at 4.5 AGeV/c incident momentum can be represented by a decay exponential law formula independent of the projectile size. The exponent of the power was found to increase with decreasing target size. The experimental data favor the idea that the backward particles were emitted due to the decay of the system in the latter stages of the reactions.     

Niederenergetische Sekundärteilchen bei Kernwechselwirkungen von 19,8 GeV/c-Protonen

A study of heavy secondary particles generated by 19.8 GeV/c proton interactions is presented. Energy spectra, angular distribution and relative abundances of these particles are determined. Indications are found for a forward motion of the target nucleus and for multiple collision in heavy nuclei.     

Production of large p⊥ single particles and multiparticle systems (JETS) in K−p interactions at 110 GeV/c

Differential cross sections of single particles and multiparticle systems produced in K^?p interactions at 110 GeV/c are presented. At large values of transverse momentum (p_⊥) we find the multiparticle cross section to be an order of magnitude larger than that for single particles. This and other features of our data are consistent with results obtained at 200 GeV/c, that have been interpreted as evidence of a new dynamical mechanism in hadron-hadron interactions. However, similar features are observed in a K^?p experiment at 16 GeV/c.     

Interactions of 10.6 GeV/nucleon gold nuclei in nuclear emulsion

Stacks of nuclear emulsion were exposed at the Brookhaven AGS to a 10.6 GeV/n beam of gold nuclei in the BNL 868 experiment. A preliminary analysis of the main features of the interactions of these nuclei is reported here and compared with those observed previously at lower energies,E<1 GeV/n. The multiplicity and pseudo-rapidity distributions of the singly charged particles emitted both in central and in minimum bias samples of interactions have been analyzed in order to look for any non random effects indicative of the nuclear state during the interactions. The fragmentation characteristics of the gold projectiles appear to be different at 10.6 GeV/n from those at ≦1 GeV/n incident energy. Fission of the gold projectiles, which was relatively frequent at low energy, is almost entirely suppressed. Some of alpha particles from the projectile are emitted with very large transverse momenta. In gold-emulsion interactions the residual target nuclei are significantly smaller than in oxygen and sulfur interactions in emulsion.

     

Features of the total disintegration events of heavyemulsion targets caused by 4.5A GeV/c16O

Total disintegration events produced by 4.5\,A GeV/c $^{16}$O--AgBr interactions are analysed to investigate the characteristics of secondary charged particles produced in such collisions. The multiplicity distributions of grey, black, and relativistic charged particles can be well represented by Gaussian distribution. The average multiplicity of grey particles is found to increase with the mass of projectile increasing, while that of black particles is found to decrease with the mass of projectile increasing. This result is in good agreement with the prediction of fireball model. Finally, the linear dependence between grey and black particles is observed, but there is no distinct dependence between the production of relativistic charged particles and the target excitation.     

The production of slow particles in 16O－Em interactions at 4.5 A GeV/c

A sample of 1233 events is used to study the general characteristics of {}^{16}O－Em interactions at 4.5 A GeV/c. Multiplicity and angular distributions of slow particles and correlations among them are discussed. The present data are compared with the corresponding results from the interactions of other projectiles at the same energy and also the same projectile at different energies. The results indicate that black particle production is independent of the energy and mass of the projectile, but for grey particles it is dependent on the mass of projectile.     

On systems of particles with finite-range and/or repulsive interactions

In an arbitrary system of particles with central repulsive interactions, right and left velocities exist at each moment of time, including infinity. An arbitrary system of particles with finite-range interactions splits into independent bounded clusters. The number of collisions in Sinai's billiard is finite.     

Charged and neutral particle multiplicity in π−p and π−n interactions at 40 GeV/c

Data on the multiplicity of charged particles and π⁰ mesons in π^?p and π^?n interactions are presented and compared to various models. The average π⁰ multiplicity tends to increase with increasing number of charged particles.     

Search for charmed hadrons in neutral strange particle events in pp interactions at 19 GeV/c

A search for charmed hadrons has been made in proton-proton interactions at 19 GeV/c using events with one or two observed neutral strange particles. No evidence for charmed particles has been found. Upper limits for their production cross sections are presented.     

Evidence of self-affine multiplicity fluctuation of particle production in 84Kr--emulsion interactions at 1.7 A GeV

Self-affine multiplicity fluctuation is investigated by using the two-dimensional factorial moment methodology and the concept of the Hurst exponent (H). Investigation on the experimental data of compound particles and target fragments emitted in 84 Kr-AgBr interactions at 1.7 A GeV reveals that the best power law behaviours are exhibited at H=0.7 and 0.6 respectively, and the data for shower particles produced in 84 Kr-emulsion interactions at 1.7 A GeV indicate that the best power law behaviour occurs at H=0.6, all of which show the self-affine multiplicity fluctuation patterns. The multifractality and the non-thermal phase transition occurring during producing the compound particles, the target fragments, and the shower particles in the 84 Kr-AgBr interaction and the 84 Kr-emulsion interaction are also discussed. The multifractality is observed during producing compound particles, target fragments, and shower particles. In the target fragment production, an evidence of non-thermal phase transition is observed, but in the shower particle production and the compound particle production, no evidence of non-thermal phase transition is observed.     

Exchange interactions in solid 3He

An outline is given of the extension to ³He of a new method for treating exchange. It is shown that indistinguishable particles can be equivalent to localized distinguishable particles. The exchange interactions do not take the Heisenberg form.     

Charge asymmetry in inelastic π−p interactions at 205 GeV/c for particles with transverse momentum > 1.0 GeVc

In 205 GeV/cπ^?p inelastic interactions, negative particles with transverse momentum greater than 1.0 GeV/c moving forward in the center of mass outnumber similar positive particles by a factor of 3.7 to 1, greatly in excess of the corresponding ratio for small transverse momentum. The asymmetry is reversed in the backward direction. The forward asymmetry is most prominent in 2-, 4-, and 6-prong interactions, but both forward and backward asymmetries are also substantial for higher multiplicity interactions.     

Forward-backward multiplicity correlations 4.5 A GeV/c ^16O-emulsion interactions

A detailed study of the mechanisms of the emissions of pions and protons in the forward and backward hemispheres in 4.5 A GeV/c oxygen-emulsion interactions has been carried out. The correlations between the multiplicities of secondary charged particles in the backward and forward hemispheres are investigated.     

质子与金属布线层核反应对微纳级静态随机存储器单粒子效应的影响分析

金属布线层对微纳级静态随机存储器(static random access memory, SRAM) 质子单粒子效应敏感性的影响值得关注. 利用Geant4针对不同能量(30 MeV, 100 MeV, 200 MeV和500 MeV)的质子与微纳级SRAM器件的核反应过程开展计算, 研究了核反应次级粒子的种类、线性能量传输值(linear energy transfer, LET)及射程情况, 尤其对高LET 值的核反应次级粒子及其射程开展了详细分析. 研究表明, 金属布线层的存在和质子能量的增大为原子序数大于或等于30的重核次级粒子的产生创造了条件, 器件体硅区中原子序数大于60的重核离子来源于质子与钨材料的核反应, 核反应过程中的特殊作用机理会生成原子序数在30至50之间的次级粒子, 且质子能量的增大有助于这种作用机理的发生, 原子序数在30至50之间的次级粒子在器件体硅区的LET值最大约为37 MeV·cm²/mg, 相应射程可达到几微米, 对于阱深在微米量级的微纳级SRAM器件而言, 有引发单粒子闩锁的可能. 研究结果为空间辐射环境中宇航器件的质子单粒子效应研究提供理论支撑.     

Surface diffusion of k-mers in one-dimensional systems

The surface diffusion of interacting k-mers is studied both through analytical and Monte Carlo simulation methods in one-dimensional systems. Adsorption isotherms, jump diffusion coefficients and collective diffusion coefficients are obtained for attractive and repulsive k-mers, showing a variety of behaviors as a function of the size of particles, k. The following main results are found: (a) diffusion coefficients increase with k for non-interacting particles; (b) for fixed k, diffusion coefficients increase as the interaction energy increases from negative (attractive) to positive (repulsive) values; (c) for attractive interactions diffusion coefficients increase with k in the whole range of coverage; (d) for repulsive interactions diffusion coefficients decrease with k up to moderately high coverage and increase with k at high coverage. Results are rationalized in terms of the behavior of the vacancy probability distribution.     

Comparative study for nucleus-nucleus interactions and modified cascade evaporation model at (4.1 – 4.5) AGeV/c

The characteristics of the nucleus-nucleus collisions at high energy for the interactions of ¹H, ⁴He, ¹²C, ¹⁶O, ²²Ne, ²⁸Si and ³²S with emulsion at momentum (4.1 – 4.5) AGeV/c have been investigated. It has been found that the multiplicity distributions of the different emitted particles and their average values can be described by the modified cascade evaporation model. The model reproduces satisfactorily the multiplicity distributions of the shower, grey and black particles and the correlations between their multiplicities. It has been seen that the number of the produced shower particles increases with the increase of the projectile mass number. From the correlation between the average multiplicity of the evaporation particles and the number of the produced particles, it was found that a phase transition in the target system may occur. The calculated pseudo-rapidity distributions of the produced shower particles are typically Gaussian shaped in the mid-rapidity region and agree well with the experimental data. Also, the angular distributions of the grey and black particles have been investigated. The angular distributions of the grey particles show a universal shape independent of the type of projectile. The angular distributions of the black particles are nearly isotropic with a small asymmetry in the forward direction. The modified cascade evaporation model, reproduces the general characteristics of the nucleus-nucleus interactions and gives an explanation for the multiparticle production process.     

Asymptotic freedom,light quarks and the origin of the ΔT = 12 rule in the non-leptonic decays of strange particles

A dynamical mechanism for the $\text{ΔT =}\text{1}\text{2}$ rule in the non-leptonic decays of strange particles is considered. The weak interactions are described within the Weinberg-Salam model while the strong interactions are assumed to be mediated by the exchange of an octet of colour vector gluons. It is shown that the effect of the strong interactions gives rise to new operators in the effective Hamiltonian of weak interactions which contain both left- and right-handed fermions. These operators satisfy the $\text{ΔT =}\text{1}\text{2}$ rule, and estimates within the relativistic quark model indicate that their contribution dominates the physical amplitudes of the K → 2π, 3π decays.