Multiplicity Of Secondary Particles Research Articles

Dependence of the Multiplicity of Secondary Particles in Relativistic Nucleus–Nucleus Interaction on the Collision Geometry

Dependence of the Multiplicity of Secondary Particles in Relativistic Nucleus–Nucleus Interaction on the Collision Geometry

Fluctuations of Initial State and Event-by-Event Pseudo-Rapidity Correlations in High Energy Nuclear Collisions

The initial state, about which there is usually very little direct experimental information, leads to significant fluctuations in the distribution of secondary particles and fragments. In this paper, to estimate the initial state the fragmentation parameters of interacting nuclei are analyzed. To investigate the correlations, the Hurst method is used. A detailed study of event-by-event pseudo-rapidity correlations in terms of the Hurst index, multiplicity of secondary particles and target dependence has been carried out for heavy (AgBr) and light (HCNO) targets present in the nuclear emulsion (NIKFI BR-2) using Au-197 projectiles at 10.6 A GeV. Evidences of short-range particle correlations and cluster formation in the pseudo-rapidity space are found from our analysis. The total ensemble of events has been divided into four classes depending on the behavior of Hurst index: uncorrelated, with short-range correlations, with long-range correlations and mixed. Events of various types differ significantly in the multiplicity of secondary particles, fragmentation of the projectile nucleus, and have significant differences in the pseudo-rapidity distribution of secondary particles.

Electromagnetic calorimeter for MPD spectrometer at NICA collider

The Multi-Purpose Detector (MPD) is designed to study a hot and dense baryonic matter formed in heavy-ion collisions at √sNN=4–11 GeV at the NICA accelerator complex (Dubna, Russia). A large-sized electromagnetic calorimeter (ECal) of the MPD spectrometer will provide precise spatial and energy measurements for photons and electrons in the central pseudorapidity region of |η| < 1.2. The Shashlyk-type sampling structure of the ECal is optimized for the photons energy range from about 40 MeV to 2–3 GeV . Fine segmentation and projective geometry of the calorimeter allow dealing with a high multiplicity of secondary particles from Au-Au reactions. In this paper, we report on a design, a construction status and expected parameters of the ECal.

Calibration of MPD electromagnetic calorimeter with muons

The shashlyk-type electromagnetic calorimeter (ECal) of the Multi-Purpose Detector at heavy-ion NICA collider is optimized to provide precise spatial and energy measurements for photons and electrons in the energy range from about 40 MeV to 2–3 GeV . To deal with high multiplicity of secondary particles from Au-Au reactions, ECal has a fine segmentation and consists of 38,400 cells (”towers”). Given the big number of “towers” and the time constraint, it is not possible to calibrate every ECal “tower” with beam. In this paper, we describe the strategy of the first-order calibration of ECal with cosmic muons.

Leading cluster approach to simulations of hadron collisions with GHOST generator

The model HDPM of CORSIKA has been updated and developed on the base of the recent measurements by ALICE, CMS, TOTEM, LHCb, LHCf... The new model, GHOST, involving a four-source production reproduces correctly the pseudo-rapidity distributions of charged secondaries and has been tested with the data in the mid and forward rapidity region, especially in the complex case of TOTEM, and also with the recent measurements of CMS, up to $ \sqrt s = 13\,{\rm{TeV}} $ (9.0 1016 eV in laboratory system). Special calculations have been devoted to the semi-inclusive data playing an important role in the cosmic ray simulation (fluctuations in earliest collisions, individual cascades measured at high altitude with high energy emulsion chambers). Taking into account the violation of KNO scaling, the negative binomial distribution (NegBin-expressed in terms of scaled elements) $ z = {n \mathord{\left/ {\vphantom {n {\bar {n}}}} \right. \kern-\nulldelimiterspace} {\bar {n}}} $ (n is the number of charged secondaries) has been used pointing out a possible asymptotic behaviour of total charged multiplicities at primary energies exceeding 40 TeV (8.5 1017 eV). Thus, larger reduction of the energies devoted to the leading cluster and very large multiplicity of secondary particles could suggest for EAS generated by primary protons a larger production of muons and a shower maximum at higher altitude.

Initial State Fluctuations and Complete Destruction of the Projectile Nucleus in Interactions of Asymmetric Nuclei at High Energies

A study of characteristics of the events of complete destruction of the projectile nucleus in the interactions between asymmetric nuclei for different initial states of the collision, is performed. In the interactions of the sulfur nuclei with heavy emulsion nuclei at energy 200 AGeV, anomalous high number of events the complete destruction of the projectile nuclei, is observed. The high probability of such events depends on the energy of interaction (it is not detected in the interactions of the sulfur nuclei with emulsion nuclei at energy of 3.7 AGeV), on the degree of asymmetry of the interacting nuclei (it is not detected in interactions of the sulfur nuclei with light emulsion nuclei) and on initial state of interaction (it is not detected in peripheral collisions). These events are characterized by high multiplicity of secondary particles and narrow angular distribution at large angles (they form narrow peak in the region of small values of average pseudorapidity).

Study on initial geometry fluctuations via correlation of finite distributions of secondary particles in nucleus-nucleus interactions

The study of the peculiarities of the distribution of secondary particles depending on the degree of centrality and the degree of asymmetry of the interacting nuclei, is performed. The number of multicharged fragments of the projectile nucleus (Nf) in interactions of sharply asymmetric nuclei depends on the centrality degree of interaction. In the majority of peripheral interactions Nf is equal 1. In the most of the central interactions there are Nf > 1 or Nf=0. At that, the events with Nf =1 are separated clearly in the distribution of the total charge of the fragments of a projectile nucleus (Q) depending on the nature of the correlation of the number of fragments of the target nucleus (Nh) and the multiplicity of secondary particles from interaction area (ns). The peak in the field of the maximum values of Q characterizes peripheral events with various degree of the periphery on a growing branch of average Nh-ns curve. And the peak in the field of small Q characterizes the central events with various degree of centrality on the decreasing branch of average Nh-ns curve.

Proton interactions with high multiplicity

Project Thermalization is aimed to study the proton-proton interaction with high multiplicity of secondary particles. The region of high multiplicity is especially actual at present. We expect the manifestation of the secondary particle collective behavior at this region. The experimentally measured topological cross section was corrected for apparatus acceptance and detection efficiency. These data are in good agreement with gluon dominance model. The comparison with other models is also done and shows no essential deviations. There is evidence that Bose-Einstein condensation can formed at high total multiplicity region.

Measurement of the fragmentation of Carbon nuclei used in hadron-therapy

The increasing use of Carbon nuclei in cancer therapy centres is motivated by their potential advantages as a very precise high LET radiation. The knowledge of the fragmentation of Carbon nuclei when they interact with the human body is important to evaluate the spatial profile of their energy deposition in the tissues, hence the damage to the tissues neighbouring the tumour. We report here a study of the fragmentation with the nuclear emulsion experimental technique. We have designed, built and exposed to a Carbon nuclei beam a chamber made of Lexan plates alternated with nuclear emulsion films. Lexan plates acted as passive material simulating human body tissues while nuclear emulsion films were used as both tracking devices with micrometric accuracy and ionisation detectors. Such a detector allowed the detection of Carbon interactions produced along their path, the identification of the fragments produced and the measurement of their scattering angle. We have measured the Carbon ion survival probability and studied their interactions. We report on the secondary particle multiplicity and the electrical charge distribution. We give results of the scattering angle of final state fragments as well as the range for H and He. Finally we give the total and partial charge-changing cross-sections for Δ z = 1 , 2 , 3 , 4 which are compared with previous results when available. The present work aims at providing data required as input to Monte Carlo simulations of Carbon ion interactions in the human body and ultimately of their therapeutic effectiveness.

Centrality of the collision and random matrix theory

I discuss the results from a study of the central 12CC collisions at 4.2 AGeV/c. The data have been analyzed using a new method based on the Random Matrix Theory. The simulation data coming from the Ultra Relativistic Quantum Molecular Dynamics code were used in the analyses. I found that the behavior of the nearest neighbor spacing distribution for the protons, neutrons and neutral pions depends critically on the multiplicity of secondary particles for simulated data. I conclude that the obtained results offer the possibility of fixing the centrality using the critical values of the multiplicity.

Cosmic ray interaction event generator SIBYLL 2.1

The cosmic ray interaction event generator Sibyll is widely used in extensive air shower simulations. We describe in detail the properties of Sibyll 2.1 and the differences with the original version 1.7. The major structural improvements are the possibility to have multiple soft interactions, introduction of new parton density functions, and an improved treatment of diffraction. Sibyll 2.1 gives better agreement with fixed target and collider data, especially for the inelastic cross sections and multiplicities of secondary particles. Shortcomings and suggestions for future improvements are also discussed.

Cosmic rays studied with a hybrid high school detector array

C rays” is the generic name for different types of particles that hit the Earth’s atmosphere with about the speed of light, varying in energy over a wide range. It was found that with increasing energy the number of cosmic rays arriving at the Earth drops sharply, see the flux-power spectrum in Fig. 1. The cosmic ray (CR) composition consists of protons (86%),αparticles (11%), nuclei of heavier elements (1%), electrons (2%) and neutrinos (<1%) [1]. Most cosmic rays up to Gev energies are thought to be produced in our galaxy by stars and beyond these energies in supernova remnants (SNR); however the origin of the highest energetic particles is still unclear. An upper limit to the energy has been observed around 100 EeV (GZK cutoff [2], [3]). A uniform distribution on the sky strongly indicates that the highest energy CRs are produced in a variety of distant extra-galactic sources. Source candidates are collimated relativistic matter streams (jets) associated with galaxies emitting powerful radio emission (radio galaxies), as well as radio-loud young galaxies called quasi-stellar objects (quasars). Furthermore, bursts of high frequency electromagnetic emission called gamma ray bursts (GRBs) and magnetars, which are very compact stars with strong magnetic fields, are also candidates for the origin of the high energy CRs since they may be capable of the extreme particle acceleration required. In the Earth’s atmosphere these CRs initiate a cascade of particle collisions in which a large multiplicity of secondary particles of all kinds are produced. The creation and annihilation of particles in the cascade establishes a so-called air shower pancake traveling through the atmosphere.Additionally, the charged particles in the pancake mainly the electrons and their counterparts the positrons get deflected in the Earth’s magnetic field and emit beamed coherent radiation called geosynchrotron emission [4]. The number of particles in the air shower and the peak voltage of the radio emission detectable on the ground depend approximately linearly on the energy of the primary particle. The radio emission increases with increasing angle between the cosmic ray trajectory and the Earth’s magnetic field [5].

TeV black hole fragmentation and detectability in extensive air showers

In models with large extra dimensions, particle collisions with center-of-mass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects. Since cosmic rays have been observed with energies above $10^{8}$ TeV, gravitational effects in the TeV energy range can, in principle, be observed by ultrahigh energy cosmic ray detectors. We consider the interaction of ultrahigh energy neutrinos in the atmosphere and compare extensive air showers from TeV black hole formation and fragmentation with standard model processes. Departures from the standard model predictions arise in the interaction cross sections and in the multiplicity of secondary particles. Large theoretical uncertainties in the black hole cross section weaken attempts to constrain TeV gravity based solely on differences between predicted and observed event rates. The large multiplicity of secondaries in black hole fragmentation enhances the detectability of TeV gravity effects. We simulate TeV black hole air showers using PYTHIA and AIRES, and find that black hole-induced air showers are quite distinct from standard model air showers. However, the limited amount of information registered by realistic detectors together with large air shower fluctuations limit in practice the ability to distinguish TeV gravity events from standard model events in a shower by shower case. We discuss possible strategies to optimize the detectability of black hole events and propose a few unique signatures that may allow future high statistics detectors to separate black hole from standard model events.

Features of pC interactions at a momentum of 4.2 GeV/c versus the degree of centrality of collisions between protons and carbon nuclei: Multiplicity of secondary particles

New experimental data obtained for the multiplicities of charged pions and protons from the interaction of 4.2-GeV/c protons with a carbon nucleus by using the 2-m propane bubble chamber installed at the High Energy Laboratory (Joint Institute for Nuclear Research, Dubna) are presented versus the degree of collision centrality. The parameter Q defined for each individual event as the difference of the total multiplicities of positively and negatively charged particles without allowing for the multiplicity of evaporated protons whose momentum is less than 0.3 GeV/c is taken for a criterion of the degree of collision centrality. It is shown that, with increasing Q, the multiplicity of positively charged pions and the multiplicity of participant protons from the target nucleus grow considerably; concurrently, the multiplicity of negatively charged pions remains at nearly the same level, while the mean multiplicity of evaporated protons decreases sharply. Our experimental data are compared with the results of calculations based on the cascade-evaporation model and the modified FRITIOF model. Within the FRITIOF model, nonnucleon degrees of freedom in nuclei (Δ+, Δ0 isobars) are taken into account for the first time, and the resulting description of the features of secondary particles appears to be by and large satisfactory.

Multiplicity of secondary particles and fragmentation in nuclear interactions of 22 Ne and 32 S nuclei with emulsion at (4.1–4.5) A GeV/ c

The interactions of 4.1AGeV/c 22Ne and 4.5AGeV/c 32S nuclei with emulsion have been studied and the dependence of the average multiplicities of the emitted secondary charged particles and the interacting projectile nucleons on the impact parameters have been investigated. The behavior of the Koba-Neilsen-Olesen (KNO) scaling formula of the multiplicity distributions produced due to the interactions of22Ne and32S at the energies mentioned above is satisfied by all target protons. The multiplicity distributions of the emitted4He fragments and the fragmentation cross-section relative to the inelastic cross-section have been investigated and give a4He-fragments yield which is always ten times greater than the yield of any other fragments. The dependence of the normalized mean multiplicity and the reduced multiplicity on the mass of the projectile and target nucleus can be described by a power law.

Angular characteristics of charged shower particles in 4.5A GeV12C-nucleus interactions

A study of angular characteristics of charged shower particles in terms of pseudorapidity, η, has been carried out by analyzing the experimental data obtained in 4.5 A GeV12C-emulsion interactions. It is observed that the maxima of rapidity width,R(η), distribution shifts towards the smaller values ofR(η) with decreasing impact parameter. It is observed that the average pseudorapidity, and the dispersion,D(η) decrease with an increase in the value of different multiplicities of secondary particles. It is also found that andD(η) strongly depend on the impact parameter. The results also reveal that the values of andD(η) remain almost the same beyond grey particle multiplicity, Ng > 11 and heavy ionizing particles, Nh > 28.

Diagnostics of superdense matter in ultrarelativistic nuclear collisions

This review presents an overview of the methods of detecting and determining the main parameters of superdense hadronic matter created in ultrarelativistic nuclear collisions. Questions related to the quark–hadron phase transition and the conditions under which it is realized are discussed, and various approaches to describing the evolution of nucleus–nucleus collisions are analyzed: microscopic Monte Carlo generators and hydrodynamical models. The basic tests proposed for the experimental study of the properties of nuclear matter under extreme conditions are studied. Possible interpretations are given of the features observed in experiments on relativistic nuclear collisions at existing accelerators (AGS, SPS), compared with the corresponding hadron–hadron collisions: broadening of the hadron momentum spectra, increased yield of low-mass dileptons, enhanced strange-particle production, suppression of the Ψ-resonance yield, and so on. The prospects for future experiments at the RHIC and LHC colliders are discussed. Special attention is paid to hard probes, which give information about the early stages of evolution of the hot, strongly interacting matter. Model representations are used to analyze the effects expected as a result of the passage of hard jets of color-charged partons through the dense matter, and the matter parameters primarily affecting the jet characteristics and their experimental identification are determined. The question of identifying hard QCD jets in heavy-ion collisions on the background of large statistical fluctuations of the transverse energy flow due to the large secondary-particle multiplicity is also discussed.

High rate multiplicity detector for relativistic heavy-ion collisions

We have constructed and operated a detector to measure the multiplicity of secondary particles produced in nucleus-nucleus collisions in the E878 experiment at the Brookhaven National Laboratory AGS facility. We describe the operation and performance of the detector in a high rate Au beam environment, and interpret the multiplicity data in terms of the impact parameters of the nucleus-nucleus collisions.

Dependence of the multiplicities of secondary particles on the impact parameter in collisions of high-energy neon and iron nuclei with photoemulsion nuclei

A method is proposed for finding the dependence of mean multiplicities of secondaries on the nucleus-collision impact parameter from the data on the total interaction ensemble. The impact parameter has been shown to completely define the mean characteristics of an individual interaction event. A difference has been found between experimental results and the data calculated in terms of the cascade-evaporation model at impact-parameter values below 3 fm.

Primary energy estimation in proton–nucleon and proton-nucleus interactions at 800 GeV

The validity of various available methods for the estimation of the primary energy in proton–nucleon and proton–nucleus interactions has been examined by using the data of the highest available machine energy for fixed targets, i.e., 800 GeV. To test the different methods for primary-energy determination for various subsamples, the data was divided into different secondary-particle multiplicity groups. It was found that Castagnoli's method (C. Castagnoli, G. Cortini, C. Franzinetti, A. Mannfredini, and A. Moreno. Nuovo Cimento, 10, 1539 (1953)). yields the best results for energy estimation for proton–nucleon collisions while the method of Gibbs et al. (R. E. Gibbs, J. R. Florian, L. D. Kirkpatrick, J. J. Lord, and J. W. Martin. Phys. Rev. D, (10, 783 (1974)). yields the best results for proton–nucleus collisions.