Comparative analysis of the characteristics of charged pions in p12C and n12C collisions at 4.2GeV/c

The new experimental data on various characteristics of the secondary charged pions produced in [Formula: see text]C collisions at 4.2[Formula: see text]GeV/c are presented. A comparative analysis of the average multiplicities and various kinematic characteristics of the charged pions produced in [Formula: see text]C and [Formula: see text]C collisions at 4.2[Formula: see text]GeV/c is made. The experimental data are compared systematically with the predictions of the modified FRITIOF model.

About Transverse Momentum Distributions of Negative Pions in p12C and π–12C Collisions at High Energies

Collision centrality dependences of the transverse momentum distributions of negative pions produced in p12C and p−12C collisions at 9.9 and 40 GeV/c, respectively, are investigated. The shapes and widths of the normalized transverse momentum distributions, as well as the average values of the transverse momentum of the negative pions, do not depend within the uncertainties on the collision centrality in p12C and п−12C collisions at 9.9 and 40 GeV/c in experiment, which is confirmed by the modified FRITIOF model calculations and minimum X2 fits of the experimental spectra with the two- and three-temperature Hagedorn model functions. Modified FRITIOF model calculations underestimate the average values of transverse momenta of the negative pions in experiment and do not reproduce the tail of the experimental transverse momentum distributions of the negative pions in both collision types. It is obtained that the transverse momentum distributions of the negative pions exhibit two temperature (two-slope) shapes in peripheral and central p12C collisions at 9.9 GeV/c in agreement with the early works on nucleus-nucleus collisions at incident energies of the order of a few GeV/c. However, the transverse momentum distributions of the negative pions in peripheral and central p−12C collisions at 40 GeV/c can be described well assuming the three temperature (three-slope) shapes of these spectra.

The Angantyr Model for Heavy-Ion Physics in PYTHIA8 †‡

We have formulated a new model for collisions with nuclei, called Angantyr, which is now included in PYTHIA8 event generator. The model is inspired by the old Fritiof model, but also includes effects of hard partonic interactions. It uses a Glauber model to calculate the number of wounded nucleons, but includes fluctuations in the nucleon-nucleon(NN) interaction to separate non-diffractively and diffractively wounded nucleons. The MC simulates final states without assuming a thermalised plasma. In this manner we are providing an event generator to be used to simulate events from pp to AA with the same underlying physics approach. Collective effects due to high string density are not included in the present version, but will be added in future work.

Centrality Dependences of Characteristics of Negative Pions in π− +12C Interactions at 40 GeV/c

The collision centrality dependences of the mean multiplicities and kinematical characteristics of negative pions produced in п−+12C collisions at 40 GeV/с are investigated. It is obtained that the average values of the partial inelasticity coefficients of negative pions (without “leading” pions) do not depend on the п−+12C collision centrality. It is shown that the normalized transverse momentum distributions, as well as the average values of the transverse momentum of negative pions, do not depend within the uncertainties on the п−+12C collision centrality. The average value of the emission angle of the negative pions was found to increase with the п−+12C collision centrality. The comparison of the normalized emission angle distributions of the negative pions in the peripheral and central п−+12C collisions at 40 GeV/с supported the assumption that such an increase in the average emission angle is likely due to an increase in the number of binary collisions and multiple rescatterings with the п−+12C collision centrality. The obtained experimental findings are reproduced qualitatively well by the Modified FRITIOF model calculations.

Modelling pp, pA and AA in Pythia8

We present a new model for generating complete exclusive hadronic final states in high energy collisions involving heavy ions. The model is called Angantyr and is inspired by the old Fritiof model, building on the concept of wounded nucleons.

Multisource Evidence for Final State Hadrons in 3.7A GeV 16O–Nucleus Interactions

In 3.7A GeV 16O interactions with emulsion nuclei, the shower particle multiplicity characteristics are investigated. Data are presented in terms of the number of emitted particles in both forward and backward angular zones. The dependence on the target size and emission direction is presented. The target separation of events depends on Glauber's multiple scattering theory approaches. A decay mechanism seems to be a characteristic of the backward production. This production may be during the de–excitation of the excited target nucleus, regarding the nuclear limiting fragmentation hypothesis. The forward emitted particle is due to a creation system. The target size is an effective parameter as well as the projectile size in this system, considering the geometrical concept regarded in the nuclear fireball concept. The data are simulated in the framework of the modified FRITIOF model. The multisource thermal model can predict source numbers responsible for particle production.

Features about pion production in 2.1A and 3.7AGeV 4He–nucleus interactions up to and out of kinematical limit

The shower particle multiplicity characteristics are studied in 2.1A and 3.7A GeV 4He interactions with emulsion nuclei. The dependencies on emission direction, energy, target size, and centrality are examined. The data are compared with the simulation of the modified FRITIOF model. The forward emitted pion multiplicity distributions exhibit KNO scaling. The decay or peaking shaped curves characterize the pion multiplicity distributions. The decay shape is suggested to be due to a single source contribution and the peaking one results from a multisource superposition. The forward emitted pion is created from fireball or hadronic matter. The target nucleus is the origin of the backward one, regarding the nuclear limiting fragmentation hypothesis.

Average characteristics of π−-mesons in HeC and CC interactions at high energies

The study of average characteristics of [Formula: see text]-mesons in Helium–Carbon and Carbon–Carbon interactions at 4.2[Formula: see text]A GeV/c is presented. The average values of multiplicity, momentum and transverse momentum of [Formula: see text]-mesons are analyzed as a function of the number of identified protons in an event. The latter is used to fix the centrality of collisions. The results are compared with Cascade model and modified Fritiof model. Some deviations of experimental data are observed than the models, which could be connected to collective interaction of inner nucleus nucleons.

RAPIDITY AND ANGULAR DEPENDENCES OF SPECTRAL TEMPERATURES OF NEGATIVE PIONS PRODUCED IN 12C12C COLLISIONS AT 4.2A GeV/c

The average spectral temperatures of negative pions in 12 C 12 C collisions at 4.2A GeV/c were extracted from transverse momentum as well as scaled center-of-mass kinetic energy distributions for different intervals of rapidity and emission angle of π- in the center-of-mass system (cms) of 12 C 12 C collisions. The temperatures extracted from experimental spectra of negative pions were compared systematically with the corresponding temperatures deduced from spectra of π- calculated using Modified FRITIOF model. The dependence of the average spectral temperatures of negative pions on the rapidity and emission angle of π- in the cms of 12 C 12 C collisions at 4.2A GeV/c was analyzed.

Forward backward studies of 22Ne(28Si)-emulsion interactions at (4.1-4.5) AGeV/c

The characteristics of nucleus–nucleus collisions at high energies are investigated for the interaction of 22Ne and 28Si with emulsion nuclei . The multiplicity and correlations of the forward (θ < 90°) and backward (θ ≥ 90°) secondary particles emitted are calculated according to the modified cascade and modified Fritiof models. The predictions of the two models are compared with experimental data at an incident momentum of (4.1–4.5) GeV/c per nucleon. Both models depend on the Monte Carlo techniques where the modified cascade model implies the superposition of nucleon–nucleon interactions, and the modified Fritiof model utilizes the Regge theory for the description of the cascading process. Comparison with data shows no clear preference of one model over the other. However, the modified Fritiof model seems to be nearer to the experimental data than the modified cascade model.PACS No.: 13.85.–t