Simulation studies of the Moliere radius for EM calorimeter materials

The Monte-Carlo calculations of the Moliere radius (RM) for some homogeneous and heterogeneous media used in electromagnetic calorimetry in the energy range from 50 MeV to 10 GeV are presented in detail. The obtained results, the uncertainties in determining RM, estimations of the absorbed energy, methods for approximating the absorbed energy, and the accuracy of the results are discussed as well. Some RM are shown for calorimeter prototypes of the Spin Physics Detector experiment (SPD). A one-parameter function of the Moliere radius dependence on the absorber-scintillator thickness ratio is obtained.Представлені детальні обчислення методом Монте-Карло радіуса Мольєра (RM) для деяких гомогенних і гетерогенних середовищ, що використовуються в електромагнітній калориметрії в діапазоні енергій від 50 МеВ до 10 ГеВ. Обговорюються отримані результати, невизначеності опису RM, оцінки поглиненої енергії, методи апроксимації поглиненої енергії, точність результатів. Наведено RM для прототипів калориметра експерименту SPD. Отримано однопараметричну функцію залежності радіуса Мольєра від співвідношення товщин поглинача та сцинтилятора.Представлены детальные вычисления методом Монте-Карло радиуса Мольера (RM) для некоторых гомогенных и гетерогенных сред, используемых в электромагнитной калориметрии в диапазоне энергий от 50 МэВ до 10 ГэВ. Обсуждаются полученные результаты, неопределенности описания RM, оценки поглощенной энергии, методы аппроксимации поглощенной энергии,точность результатов. Приведены RM для прототипов калориметра эксперимента SPD. Получена однопараметрическая функция зависимости радиуса Мольера от соотношения толщин поглотителя и сцинтиллятора

Effect of energy leakage on the energy resolution of E.M. sampling calorimeters

The electromagnetic sampling calorimeters of the SPD experiment (NICA collider) are being investigated by Monte Carlo method. The simulation is used to study in detail the influence of energy leakages from the module on its energy resolution. The values of the stochastic and constant terms are obtained for the SPD calorimeter prototypes.Розглядаються прототипи ідеального електромагнітного семплінг-калориметра установки SPD колайдера NICA. За допомогою моделювання детально досліджується вплив витоків енергії з модуля на його енергетичну роздільну здатність. Отримано величини стохастичного і константного членів для різних варіантів прототипу калориметра SPD.Рассматриваются прототипы идеального электромагнитного сэмплинг-калориметра установки SPD коллайдера NICA. С помощью моделирования детально исследуется влияние утечек энергии из модуля на его энергетическое разрешение. Получены величины стохастического и константного членов для различных вариантов прототипа калориметра SPD

Effect of energy leakage on the energy resolution of E.M. sampling calorimeters

The electromagnetic sampling calorimeters of the SPD experiment (NICA collider) are being investigated by Monte Carlo method. The simulation is used to study in detail the influence of energy leakages from the module on its energy resolution. The values of the stochastic and constant terms are obtained for the SPD calorimeter prototypes.Розглядаються прототипи ідеального електромагнітного семплінг-калориметра установки SPD колайдера NICA. За допомогою моделювання детально досліджується вплив витоків енергії з модуля на його енергетичну роздільну здатність. Отримано величини стохастичного і константного членів для різних варіантів прототипу калориметра SPD.Рассматриваются прототипы идеального электромагнитного сэмплинг-калориметра установки SPD коллайдера NICA. С помощью моделирования детально исследуется влияние утечек энергии из модуля на его энергетическое разрешение. Получены величины стохастического и константного членов для различных вариантов прототипа калориметра SPD

Charm production nearby threshold in pA-interactions at 70 GeV

The results of the SERP-E-184 experiment at the U-70 accelerator (IHEP, Protvino) are presented. Interactions of the 70 GeV proton beam with C, Si and Pb targets were studied to detect decays of charmed $D^0$, $\overline D^0$, $D^+$, $D^-$ mesons and $\Lambda _c^+$ baryon near their production threshold. Measurements of lifetimes and masses are shown a good agreement with PDG data. The inclusive cross sections of charm production and their A-dependencies were obtained. The yields of these particles are compared with the theoretical predictions and the data of other experiments. The measured cross section of the total open charm production ($\sigma _{\mathrm {tot}}(c\overline c)$ = 7.1 $\pm$ 2.3(stat) $\pm$1.4(syst) $\mu$b/nucleon) at the collision c.m. energy $\sqrt {s}$ = 11.8 GeV is well above the QCD model predictions. The contributions of different species of charmed particles to the total cross section of the open charm production in proton-nucleus interactions vary with energy.Comment: 4 pages, 6 pages, 38th International Conference on High Energy Physics 3-10 August 2016, Chicago, US

Azimuthal Anisotropy of Photon and Charged Particle Emission in Pb+Pb Collisions at 158 A GeV/c

The azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in Pb + Pb collisions at 158 A GeV/c in the WA98 experiment at the CERN SPS. The anisotropy of the azimuthal distributions is characterized using a Fourier analysis. For both the photon and charged particle distributions the first two Fourier coefficients are observed to decrease with increasing centrality. The observed anisotropies of the photon distributions compare well with the expectations from the charged particle measurements for all centralities.Comment: 8 pages and 6 figures. The manuscript has undergone a major revision. The unwanted correlations were enhanced in the random subdivision method used in the earlier version. The present version uses the more established method of division into subevents separated in rapidity to minimise short range correlations. The observed results for charged particles are in agreement with results from the other experiments. The observed anisotropy in photons is explained using flow results of pions and the correlations arising due to the decay of the neutral pion

Interferometry of Direct Photons in Central 280Pb+208Pb Collisions at 158A GeV

Two-particle correlations of direct photons were measured in central 208Pb+208Pb collisions at 158 AGeV. The invariant interferometric radii were extracted for 100<K_T<300 MeV/c and compared to radii extracted from charged pion correlations. The yield of soft direct photons, K_T<300 MeV/c, was extracted from the correlation strength and compared to theoretical calculations.Comment: 5 pages, 4 figure

Suppression of High-p_T Neutral Pion Production in Central Pb+Pb Collisions at sqrt{s_NN} = 17.3 GeV Relative to p+C and p+Pb Collisions

Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at sqrt{s_NN} = 17.4 GeV at mid-rapidity 2.3 < eta_lab < 3.0 over the range 0.7< p_T < 3.5 GeV/c. The spectra are compared to pi0 spectra measured in Pb+Pb collisions at sqrt{s_NN} = 17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N_part < 300) the yield of pi0's with p_T > 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N_coll), while for central Pb+Pb collisions with N_part > 350 the pi0 yield is suppressed.Comment: 5 pages, 4 figure

Pion Freeze-Out Time in Pb+Pb Collisions at 158 A GeV/c Studied via pi-/pi+ and K-/K+ Ratios

The effect of the final state Coulomb interaction on particles produced in Pb+Pb collisions at 158 A GeV/c has been investigated in the WA98 experiment through the study of the pi-/pi+ and K-/K+ ratios measured as a function of transverse mass. While the ratio for kaons shows no significant transverse mass dependence, the pi-/pi+ ratio is enhanced at small transverse mass values with an enhancement that increases with centrality. A silicon pad detector located near the target is used to estimate the contribution of hyperon decays to the pi-/pi+ ratio. The comparison of results with predictions of the RQMD model in which the Coulomb interaction has been incorporated allows to place constraints on the time of the pion freeze-out.Comment: 9 pages, 12 figure