Laboratory of Information Technologies

Seminar of the Scientific Department of Computational Physics

Date and Time: Tuesday, 13 May 2025, at 3:00 PM

Venue: room 310, Meshcheryakov Laboratory of Information Technologies

1. Seminar topic: “Analysis of structure of the PTNS vesicles based on small-angle neutron scattering data obtained at the Yellow Submarine Spectrometer”

   Authors: Elena Zemlyanaya, Mikhail Kiselev, Varvara Chausova, László Almásy

   Speaker: Elena Zemlyanaya

   Abstract:
   

   The structure of unilamellar vesicles of the phospholipid transport nanosystem (PTNS) is analysed based on small-angle neutron scattering data (SANS) obtained on the Yellow Submarine Small Angle Spectrometer. SANS measurements were performed on polydispersed populations of PTNS vesicles in heavy water with different PTNS concentrations and with different purity of soybean phospholipids in the PTNS samples. Results of the analysis are compared with the characteristics of PTNS vesicular systems obtained earlier in the analysis of other small-angle scattering data from PTNS samples.




2. Seminar topic: “On the understanding of enhanced production of strange particles in nucleus-nucleus interactions at high energies”

   Authors: Vladimir Uzhinsky, Aida Galoyan (VBLHEP), Nikita Chalyi (Tomsk State University, Russia)

   Speaker: Vladimir Uzhinsky

   Abstract:
   

   Recently, the NA61/SHINE Collaboration published experimental data on the production of π± and K± mesons in central ⁴⁰Ar+⁴⁵Sc interactions at various energies. The collaboration compared its results with calculations of the theoretical Monte Carlo models – EPOS 1.99, PHSD 4.1 and SMASH 2.1.4. It turned out that none of these models reproduces the data in full. All models significantly underestimate the yields of K+ and K− mesons by a factor of ∼2. In this paper, an attempt is made to describe the yields of K+ and K− mesons within the framework of the quark-gluon string model implemented in the DCM (Dubna Cascade Model) program. According to this model, strings formed between the “sea” quarks and antiquarks of colliding nucleons should be dominated in central nucleus-nucleus interactions. To achieve an agreement with the experimental data, it is necessary to assume that strange quarks and antiquarks dominate among the “sea” quarks and antiquarks. The probability of finding a pair of strange quark – strange antiquark is 72%. This value seems unrealistic. It may be related to an incorrect implementation of the quark-gluon string model in the DCM. It is of interest to obtain the corresponding predictions of the modern EPOS and QGSJET models.




3. Seminar topic: “Simulation of neutron and nuclear fragment production in Urqmd 3.4 model supplemented by a clustering model and a multi-fragmentation statistical model”

   Authors: Aida Galoyan (VBLHEP), T. Q. T. Le, Arkady Taranenko (VBLHEP), Vladimir Uzhinsky

   Speaker: Aida Galoyan

   Abstract:
   

   Many experiments in high energy physics use the UrQMD model at the design stage for predictions of experimental data and analysis of the obtained results. Researchers used the new version of the UrQMD 3.4 model to analyse the experimental data of the NA61/SHINE Collaboration. They found that the UrQMD 3.4 model reproduces the data on π±, K-, proton and anti-proton production in ⁴⁰Ar+⁴⁵Sc interactions with the appropriate choice of the impact parameter. They apply the UrQMD 3.4 model to study the spectra of neutrons produced in proton-nucleus interactions. The model well reproduces energetic (En > 40 MeV) neutron spectra in p + Al, Fe, Pb at 3 GeV in the so-called “cascade” mode. Off-shell mass neutrons are dominate at lower neutron energies. The off-shell nucleons have to form residual nuclei at de-excitation of which evaporated nucleons and light nuclei have to be produced. In order to simulate the process, scientists have coupled the UrQMD 3.4 model with the clustering model and Statistical Multi-fragmentation Model (SMM) using “potential” mode of the UrQMD model. Researchers have reached a good description of energy distributions of slow and fast neutrons produced in proton-nucleus and nucleus-nucleus interactions. UrQMD 3.4 +SMM model reproduces sufficiently well the atomic mass and charge distributions of nuclear fragments in nucleus-nucleus interactions. UrQMD 3.4 +SMM can be applied at NICA experiments.




4. Seminar topic: “Calculation of target dependence of the isotope distributions in heavy-ion reactions at energies from 35 to 140 MeV per nucleon in the modified transport-statistical model”

   Authors: Tatiana Mikhaylova, Erdemchimeg Batchuluun (FLNR)

   Speaker: Tatiana Mikhaylova

   Abstract:
   

   In heavy-ion reactions a lot of different isotopes are produced. Different models to predict their cross-sections exist. In this presentation the results of calculations in the modified transport-statistical approach of isotope distributions of forward-moving fragments for reactions with different projectiles from ¹⁸O to ⁶⁴Ni with energies from 35 to 140 MeV per nucleon on two targets are discussed: ¹⁸¹Ta and ⁹Be. The target dependence (the ratios of isotope distributions for two targets) was studied. In previous papers this characteristic for reactions with light projectile 18O was studied. It was shown that the hyperbolic shape of their envelope can be explained by the different range of impact parameters involved in reactions on heavy and light targets. In this work the dependence of target ratio on the mass number of the projectile and its energy is studied. The results can be important for better prediction of isotope distributions in fragmentation reactions.