Seminar

Seminar program:

1. E. Zemlyanaya, M. Kiselev, V. Chausova, L. Almasy

   Analysis of structure of the PTNS vesicles based on small-angle neutron scattering data obtained at the “Yellow Submarine” spectrometer

   Abstract:

   Structure of unilamellar vesicles of the phospholipid transport nanosystem (PTNS) is analyzed 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. V. Uzhinsky, A. Galoyan, N. Chalyi

   Towards understanding of enhanced production of strange particles in nucleus-nucleus interactions at high energies

   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 program – Dubna Cascade Model. 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. A. Galoyan, T.Q.T. Le, A. Taranenko, V. Uzhinsky

   Simulation of neutron and nuclear fragment production in Urqmd 3.4 model supplemented by a clustering model and a multi-fragmentation statistical model

   Abstract:

   Many experiments in high energy physics use the UrQMD model at the design stage, for predictions of experimental data and also for analysis of the obtained results. We used the new version of the UrQMD 3.4 model to analyze the experimental data of the NA61/SHINE collaboration. We obtained 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. We also apply the UrQMD 3.4 model to study the spectra of neutrons produced in proton-nucleus interactions. The model well reproduces energetic (En > 10 MeV) neutron spectra in p + Al, Fe, Pb at the energy 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, we have coupled the UrQMD 3.4 model with the clustering model and Statistical Multi-fragmentation model (SMM) using "potential" mode of the UrQMD model. We 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 also 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. Т. Mikhaylova, E. Batchuluun

   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

   Abstract:

   In heavy-ion reactions a lot of different isotopes are produced. Different models to predict their cross-sections exist. In this report 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 : ¹⁸¹Ta and ⁹Be, - are discussed. The target dependence (the ratios of isotope distributions for two targets) was studied. In our previous papers we studied this characteristic for reactions with light projectile ¹⁸O. 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 report 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.

Information about the seminar and the link to join are available at Indico.