Using the Q of TOF to Identify the Particles

Time of flight counter (TOF) is one of the main subdetectors of Beijing SpectrometerII (BESII) for identification of charge particles. Time of flight and pulse amplitude are measured from the time of flight counters, when the particle hits on the TOF. Based on Di-mu sample from BESII, the correction of pulse amplitude Q is studied. Using the hadron sample of J/ψ, the relation between the corrected Pulse amplitude and βγ value is analyzed. A conclusion is that it is feasible to use the pulse amplitude Q₀ of TOF to identify the particles. Finally the efficiency and error efficiency is given while the pulse amplitude is used to identify the particles.     

Measurements of the light output functions of plastic scintillator using 9Be(d,n)10B reaction neutron source

The light output functions for protons of ST-401 and BC-408 plastic scintillators were measured using white neutron source produced by the 9Be(d,n)10B reaction at the HI-13 Tandem Accelerator at China Institute of Atomic Energy(CIAE).The LOFs of plastic scintillators for protons in the energy range of 0.516.5 MeV were obtained by the time-of-flight(TOF)technique and an iterative procedure.Two parameters(kB and C)were deduced by fitting the experimental data.     

Relation between Interactive Models and Identification of Primary Cosmic Ray Components at the “Knee”

Monte Carlo simulations of extensive air shower at the “knee” region are carried out by use of four kinds interactive models according to the condition of Tibet Yangbajing ASγ hybrid experiment.The characters of shower for different interactive models are analysed,and the parameters closely related with primary particle mass are given. The BP artificial neural network(ANN)is used to select the proton events from the simulation results,and the relation between the abilith of primary particle identification and interactive models is studied. The results show that the primary proton events can be effectively identified by ANN methed from simulation data of different interactive models with similar identification capabilities.     

Effects of density-and momentum-dependent potentials in Au+Au collisions at intermediate energies

Based on an isospin-dependent transport model, the effects of the density-and momentum-dependent potentials are studied by simulating Au on Au collisions at 90, 120, 150 and 400 MeV/nucleon. It is found that the calculated results overestimate the experimental data on the directed flow and underestimate the data on the elliptic flow for protons. The impact of the density-and momentum-dependent potentials is observed in the mid-rapidity region of the final spectra. At 90 MeV/nucleon, the momentum-dependent potential has a larger impact on the observables than the density-dependent potential, and the elliptic flow has a higher value with the positive effective mass splitting. At 400 MeV/nucleon, however, the opposite is observed. The rapidity dependence of the elliptic flow for protons is sensitive to the symmetry energy. A soft symmetry energy corresponds to a higher value of the proton elliptic flow.     

Portion of muons with a threshold energy above 1 GeV in extensive air showers with ultra-high energies,according to the Yakutsk EAS array data

Characteristics of the muon component in extensive air showers and the fluctuations of muons are considered. In this work, we compare experimental data with computations performed for various models of the hadron interactions of protons and iron nuclei. The aim of this analysis is to obtain information on the mass composition of cosmic rays in an ultra-high energy region.     

J~P assignments of Λ_c~+ baryons

The "good" diquark is employed to study Λ_c~+ baryons within a mass loaded flux tube model. The study indicates that all Λ_c~+ baryons candidates in the 2008 review by the Particle Data Group (PDG) are well described in the mass loaded flux model. The quantum numbers J~P of these Λ_c~+ candidates are assigned. If Λ_c(2765)~+ is an orbitally excited Λ_c~+, it is likely the J~P=3~+/2 one. If Λ_c(2765)~+ is an orbitally excited Σ_c, there ought to be another J~P = 3~+/2 Λ_c~+ with mass ≈ 2770 MeV. In the model, there exists no J~P = 1~+/2 Λ_c~+ (≈ 2700) predicted in existing literature. Λ_c(2940)~+ is very possible the orbitally excited baryon with J~P = 5~-/2.     

QCD sum rule for Λ(1405)

Motivated by the recently constructed interpolation field for S₁₁(1535), we propose a new interpolating field for Λ(1405). Using this current, we calculate the mass of Λ(1405) based on the conventional QCD sum rule analysis. By calculating the Wilson coefficients up to dimension 8 operators and taking into account the mass corrections from s-quark, we find the calculated mass of Λ(1405) to be very close to its experimental value.     

Single-spin asymmetries for small-angle pion production in high-energy hadron collisions

Within the framework of a simple model, we study single-spin asymmetries for pion production in hadron–hadron collisions at high energies with one hadron polarized. The asymmetries are generated via a mechanism of final- (initial-) state interactions. For peripheral kinematics, we find nonzero asymmetries at the high-energy limit when the pion belongs to the fragmentation region of the polarized proton. Numerical results and comparison with existing experimental data are presented. We also discuss the relationship with Odderon exchange phenomenology. Received: 11 May 1999 / Revised version: 22 July 1999 / Published online: 3 November 1999     

Λ Production and Λ/p Ratio in Relativistic Heavy Ion Collisions

The Λ multiplicity and Λ/p ratio are studied by hadron transportation-string fragmentation model in relativistic heavy ion collisions. Firstly, the dependence of Λ multiplicity and Λ/p ratio on the system size and the collision centrality is studied. It shows that the Λ and p multiplicities go up as the increase of system size and the increase of collision centrality. However, their ratio keeps almost a constant. The effect of Λ annihilation cross section to Λ multiplicity and Λ/p ratio is also studied. It is found that this effect is weak: Λ multiplicity and Λ/p ratio have a little amount of increase by the decrease of Λ annihilation cross section. Even the cross section is down to zero, Λ/p ratio is only 1.2 in 200A GeV AuAu head on collision. The Λ/p ratio is obtained to be 0.28 in pp collision, lying in the range of experimental data:0.2—0.3. It is also obtained that the ratio in AA collisions is 3—5 times of that in pp collision.     

Rapidity distributions of hadrons in the HydHSD hybrid model

A multistage hybrid model intended for describing heavy-ion interactions in the energy region of the NICA collider under construction in Dubna is proposed. The model combines the initial, fast, interaction stage described by the model of hadron string dynamics (HSD) and the subsequent evolution that the expanding system formed at the first stage experiences at the second stage and which one treats on the basis of ideal hydrodynamics; after the completion of the second stage, the particles involved may still undergo rescattering (third interaction stage). The model admits three freeze-out scenarios: isochronous, isothermal, and isoenergetic. Generally, the HydHSD hybrid model developed in the present study provides fairly good agreement with available experimental data on proton rapidity spectra. It is shown that, within this hybrid model, the two-humped structure of proton rapidity distributions can be obtained either by increasing the freeze-out temperature and energy density or by more lately going over to the hydrodynamic stage. Although the proposed hybrid model reproduces rapidity spectra of protons, it is unable to describe rapidity distributions of pions, systematically underestimating their yield. It is necessary to refine the model by including viscosity effects at the hydrodynamic stage of evolution of the system and by considering in more detail the third interaction stage.     

Diquark scattering model for hadron multiplicities in μp interactions

Multiplicities of hadrons produced in μp scattering are analyzed with a diquark scattering model. it is assumed that a proton is composed of a quark and a scaler diquark and that both the quark and the diquark act as partons. A reasonable agreement between the experimental data and the predictions of the model is obtained. In particular, the observed large ratio of the proton to the overall positive hadron yield forx>0.2 is successfully reproduced.     

二维光电位置敏感器件的非线性修正

根据二维光电位置敏感器件 (PSD)的工作原理 ,分析了影响PSD线性度的主要因素 ,提出了一种用神经网络对PSD进行非线性修正的方法。以PSD的输入输出数据对作为样本训练的神经网络 ,利用神经网络所具有地能够以任意精度逼近非线性函数的能力 ,实现PSD的输出与实际光点位置之间的映射 ,在神经网络的输出端得到线性响应。该方法的优点是不需要很大的数据存储量即可得到很好的修正效果。结果表明 ,修正后的PSD能在较宽的位置范围内输出高线性度的信号     

中能重离子碰撞中前平衡核子发射的同位旋效应

利用同位旋相关的输运理论,研究了中能重离子碰撞中丰中子和缺中子碰撞系统在较宽能区范围内前平衡发射核子的同位旋效应.结果表明除低能区外,在100MeV/u以上核子–核子碰撞动力学效应起主要作用的能区,前平衡发射的中子–质子比仍然对介质中核子–核子碰撞截面的同位旋效应不灵敏,然而对于对称势的改变非常灵敏.故从低能量到较高能量的较大能区内,前平衡发射的中子–质子比的理论值与实验值的比较是提取对称势形式和强度的灵敏探针.     

Artificial neural network (ANN) approach for modeling and formulation of phenol adsorption onto activated carbon

In this study, a three-layer feed-forward back propagation network with Levenberg-Marquardt (LM) learning algorithm was applied to predict adsorption of phenol onto activated carbon (AC). Batch experiments were carried out to obtain experimental data. The neural network was trained considering the amount of adsorbent, initial concentration of phenol, temperature, contact time and pH as input parameters and the final concentration of phenol as a desired parameter. Different transfer functions for hidden and output layers and different number of neurons in a hidden layer were tested to optimize the network structure. An empirical equation for final concentration of phenol was developed by using the weights of optimized network. Accuracy of the developed ANN model was also measured using statistical parameters, such as mean absolute error (MAE), mean square error (MSE), root mean square error (RMSE) and correlation coefficient (R²). Results showed that MAE, MSE, RMSE, and R² values of the ANN model were 0.1540, 0.0565, 0.2378, and 0.9998, respectively, which indicate high accuracy of the ANN model. In the equilibrium study, predicted results of the ANN model were also compared with experimental data and the results of other conventional isotherm models.     

PROTON DECAY RATE AND THE PROTON WAVEFUNCTION

The pionic two body decay process of the proton is discussed in the SU(5) grand unification theory by using the field-current relation of the composite particle and the soft pion approximations. We connect the proton decay process with the J/ψ→pp decay amplitude and determine the wavefunction at the origin from the experimental value of the decay rate J/ψ→pp, hence we can obtain the value of the proton decay lifetime. In order to estimate the uncertainty of the proton decay lifetime due to the proton wavefunction at the origin, the lower bound of it is analysed by using an interesting model. If taking Λ_MS=200 MeV, it will be a serious test for the minimal SU(5) grand unified gauge theory. It should be noted that this method which connect the proton decay process with other relavant processes will be very useful to determine the proton decay lifetime.     

A one-parameter formula for estimating the Λ well depth

A one parameter, semi-empirical formula for Λ-binding energy of heavy hypernuclei in the inverse powers of core mass number (A _c) has been developed in the framework of the folding model. Unlike similar calculations reported by other authors (Deloff 1971; Daskaloyanniset al 1985), we are able to take into account the effect arising from the difference in the number of protons and neutrons of the core nuclei having same mass number. The radius and diffuseness are parametrized using the experimentally known charge density data of a fairly large number of medium and heavy nuclei. The well depth parameter (i.e. Λ-binding energy in infinite nuclear matter) in the formula is obtained from a fit to theB _Λ data of _Λ ²⁸ Si, _Λ ⁴⁰ Ca, _Λ ⁵¹ V and _Λ ³⁹ Y. Using the original Λ-nucleus potential, theB _Λ of ground and the experimentally known excited states of these hypernuclei have also been calculated by solving numerically the two-body Schrödinger equation. The agreement with the experimental data is satisfactory.     

Regarding the Distribution of Glue in the Pion

Understanding why the scale of emergent hadron mass is obvious in the proton but hidden in the pion may rest on mapping the distribution functions(DFs) of all partons within the pion and comparing them with those in the proton;and since glue provides binding in quantum chromodynamics,the glue DF could play a special role.Producing reliable predictions for the proton’s DFs is difficult because the proton is a three-valence-body bound-state problem.As sketched herein,the situation for the pion,a t...     

Estimation of The Cosmic Ray Mass Composition at Energy Above 10 17 eV According to Scintillation Detectors of the Yakutsk Array

The lateral distribution of cascade particles was studied in extensive air showers initiated by cosmic rays with energies above 1017 eV. The study is based on experimental data of ground-based and ground-shielded (with ∼1-GeV energy threshold) scintillation detectors of the Yakutsk EAS array collected during the continuous observational period from 1977 to 2017. Particle density measured in experiment is compared to the results of simulations performed with the use of several ultra-high energy hadron interaction models. The best agreement between theory and experiment was obtained for qgsjet01 and qgsjet ii-04 models. Interpretation of our data has indicated that within the energy range (1–30) × 1017 eV the cosmic ray mass composition changes from nuclei of intermediate group towards protons.     

Photon-exchange processes at hadron colliders as a probe of the dynamics of diffraction

The rich structure of photon-exchange processes at hadron colliders is studied. We discuss central vector meson production , W production and production. Each process has distinct, and large, soft pp rescattering effects, which can be directly observed by detecting the outgoing protons. This allows a probe of the optical density of the proton, which plays a crucial role in the evaluation of the rapidity gap survival probabilities in diffractive-like processes at hadron colliders. We note that an alternative mechanism for production is odderon, instead of photon, exchange; and that the ratio of odderon to photon contributions is enhanced (suppressed) for vector meson production. Received: 1 February 2002 / Revised version: 4 April 2002 / Published online: 22 May 2002