Simulation of neutron production in hadron-nucleus and nucleus-nucleus interactions in Geant4

Studying experimental data obtained at ITEP [1] on neutron production in interactions of protons with various nuclei in the energy range from 747 MeV up to 8.1 GeV, we have found that slow neutron spectra have scaling and asymptotic properties [2]. The spectra weakly depend on the collision energy at momenta of projectile protons larger than 5 - 6 GeV/c. These properties are taken into account in the Geant4 Fritiof (FTF) model. The improved FTF model describes as well as the Geant4 Bertini model the experimental data on neutron production by 1.2 GeV and 1.6 GeV protons on targets (Fe, Pb) [3] and by 3.0 GeV protons on various targets (Al, Fe, Pb) [4]. For neutron production in antiproton-nucleus interactions, it was demonstrated that the FTF results are in a satisfactory agreement with experimental data of the LEAR collaboration [5]. The FTF model gives promising results for neutron production in nucleus - nucleus interactions at projectile energy 1 - 2 GeV per nucleon [6]. The observed properties allow one to predict neutron yields in the nucleus-nucleus interactions at high and very high energies. Predictions for the NICA/MPD experiment at JINR are presented.Comment: 6 pages, 5 figures. Contribution to Proceedings of Baldin ISHEPP XXI

Dynamics of Anti-Proton -- Protons and Anti-Proton -- Nucleus Reactions

A short review of simulation results of anti-proton-proton and anti-proton-nucleus interactions within the framework of Geant4 FTF (Fritiof) model is presented. The model uses the main assumptions of the Quark-Gluon-String Model or Dual Parton Model. The model assumes production and fragmentation of quark-anti-quark and diquark-anti-diquark strings in the mentioned interactions. Key ingredients of the model are cross sections of string creation processes and an usage of the LUND string fragmentation algorithm. They allow one to satisfactory describe a large set of experimental data, especially, a strange particle production, Lambda hyperons and K mesons.Comment: 7 pages, 8 figure

Production of strange particles in hadronic interactions

The NA61/SHINE collaboration has recently published high precision data on production of $\pi^\pm$ and $K^\pm$ mesons, protons, antiprotons and $\Lambda$ hyperons in ${\rm pp}$ interactions at 20, 31, 40, 80 and 158 GeV/c, and in ${\rm pC}$ interactions at 31 GeV/c. The collaboration also presented experimental data on production of particles - $\pi^\pm$, $K^\pm$, $p^\pm$, $\rho^0$, $\omega$ and $K^{*0}$ in $\pi^-{\rm C}$ collisions at 158 and 350 GeV/c. The collaboration has compared these data with various Monte Carlo model calculations: UrQMD, EPOS, GiBUU, and others. All of the models have various problems. The latest version of the FTF (Fritiof) model of Geant4 solves most of these problems. In the FTF model, we have improved the fragmentation of quark-gluon strings with small masses and introduced dependencies of probabilities of strange mesons and baryon-antibaryon pair's creation on string masses. Due to these changes, we describe the data of the NA61/SHINE collaboration on particle production in ${\rm pp, pC}$, and $\pi^-{\rm C}$ interactions. The improved Geant4 FTF model also well reproduces experimental data on inclusive cross sections of $\Lambda, \bar{\Lambda}$ and $K^{0}$ production in antiproton-proton interactions at various energies. The modified FTF model allows one to simulate realistic processes with two particle productions - $\bar{p}p \rightarrow \Lambda \bar{\Lambda}$, $\bar{p}p \rightarrow K^{+} K^{-}$, $\bar{p}p \rightarrow \Lambda \bar{\Sigma}$, and $\bar{p}p \rightarrow\Sigma \bar{\Sigma}$, which will be studied in the future by the PANDA experiment at FAIR (GSI, Germany).Comment: 10 pages, 8 figures, IWNT-37, Rila, 2018, Bulgari

A new development cycle of the Statistical Toolkit

The Statistical Toolkit is an open source system specialized in the statistical comparison of distributions. It addresses requirements common to different experimental domains, such as simulation validation (e.g. comparison of experimental and simulated distributions), regression testing in the course of the software development process, and detector performance monitoring. Various sets of statistical tests have been added to the existing collection to deal with the one sample problem (i.e. the comparison of a data distribution to a function, including tests for normality, categorical analysis and the estimate of randomness). Improved algorithms and software design contribute to the robustness of the results. A simple user layer dealing with primitive data types facilitates the use of the toolkit both in standalone analyses and in large scale experiments.Comment: To be published in the Proc. of CHEP (Computing in High Energy Physics) 201

Herwig++ 2.0 Release Note

A new release of the Monte Carlo program Herwig++ (version 2.0) is now available. This is the first version of the program which can be used for hadron-hadron physics and includes the full simulation of both initial- and final-state QCD radiation.Comment: Source code and additional information available at http://hepforge.cedar.ac.uk/herwig

Herwig++1.0: an event generator for e(+)e(-) annihilation

Results from the new Monte Carlo event generator Herwig++ are presented. This first version simulates Hadron Emission Reactions With Interfering Gluons in electron-positron annihilation. The parton shower evolution is carried out using new evolution variables suited to describing radiation from heavy quarks as well as light partons. The partonic final state is fragmented into hadrons by means of an improved cluster hadronization model. The results are compared with a wide variety of data from LEP and SLC

GeantV: Results from the prototype of concurrent vector particle transport simulation in HEP

Full detector simulation was among the largest CPU consumer in all CERN experiment software stacks for the first two runs of the Large Hadron Collider (LHC). In the early 2010's, the projections were that simulation demands would scale linearly with luminosity increase, compensated only partially by an increase of computing resources. The extension of fast simulation approaches to more use cases, covering a larger fraction of the simulation budget, is only part of the solution due to intrinsic precision limitations. The remainder corresponds to speeding-up the simulation software by several factors, which is out of reach using simple optimizations on the current code base. In this context, the GeantV R&D project was launched, aiming to redesign the legacy particle transport codes in order to make them benefit from fine-grained parallelism features such as vectorization, but also from increased code and data locality. This paper presents extensively the results and achievements of this R&D, as well as the conclusions and lessons learnt from the beta prototype.Comment: 34 pages, 26 figures, 24 table

Geant4 FTF model description of the latest data by the NA61/SHINE collaboration on 40Ar+45Sc{\rm ^{40}Ar+{}^{45}Sc} interactions

It is shown that the Geant4 FTF model, which does not include the simulation of the hard parton-parton scattering and the formation of the quark-gluon plasma (QGP), describes well the NA61/SHINE data on $\pi^-$ meson distributions for the interactions at $\sqrt{s_{NN}}=$ 5.2, 6.1, 7.6 and 8.8 GeV. At higher energies, $\sqrt{s_{NN}}=$ 11.9 and 16.8 GeV, the model underestimates the data. This is considered as an indication of the formation of QGP at higher energies in central collisions of light and intermediate nuclei than in collisions of heavy nuclei ($\sqrt{s_{NN}}\sim 6$ GeV).Comment: 5 pages, 2 figure

Pion and proton showers in the CALICE scintillator-steel analogue hadron calorimeter

Showers produced by positive hadrons in the highly granular CALICE scintillator-steel analogue hadron calorimeter were studied. The experimental data were collected at CERN and FNAL for single particles with initial momenta from 10 to 80 GeV/c. The calorimeter response and resolution and spatial characteristics of shower development for proton- and pion-induced showers for test beam data and simulations using Geant4 version 9.6 are compared.Comment: 26 pages, 16 figures, JINST style, changes in the author list, typos corrected, new section added, figures regrouped. Accepted for publication in JINS

Search for the Supersymmetric Partner of the Top-Quark in ppˉp \bar{p} Collisions at s=1.8TeV\sqrt{s} = 1.8 {\rm TeV}

We report on a search for the supersymmetric partner of the top quark (stop) produced in $t \bar{t}$ events using $110 {\rm pb}^{-1}$ of $p \bar{p}$ collisions at $\sqrt{s} = 1.8 {\rm TeV}$ recorded with the Collider Detector at Fermilab. In the case of a light stop squark, the decay of the top quark into stop plus the lightest supersymmetric particle (LSP) could have a significant branching ratio. The observed events are consistent with Standard Model $t \bar{t}$ production and decay. Hence, we set limits on the branching ratio of the top quark decaying into stop plus LSP, excluding branching ratios above 45% for a LSP mass up to 40 {\rm GeV/c}$^{2}$.Comment: 11 pages, 4 figure