Registration Number
0218U001382,
0116U005480
, R & D reports
Title
KIPT participation in the CMS data processing during Run 2 of the Large Hadron Collider and in the research work on the CMS hadron calorimetry upgrades
popup.stage_title
Head
Levchuk Leonid Gennadievich, Кандидат фізико-математичних наук
Registration Date
07-02-2018
Organization
National Science Center "Kharkiv Institute of Physics and Technology
popup.description2
The high transfer rate of the experimental information from the Large Hadron Collider (LHC) during its Run 2 has strengthened the requirements for the distributed system that provides data processing for the CMS experiment. The specialized KIPT computing facility (CF) is an active element of this system. It operates at Tier 2 (T2) of the hierarchic worldwide Grid infrastructure WLCG/CMS and allocates its resources for processing of data accumulated in the experiment and Monte Carlo generation of the CMS events. The KIPT FS was commissioned in the CMS as a T2-center T2_UA_KIPT, and, since then, it has been the only Ukrainian site involved in the computing infrastructure of this experiment. In 2017, a further successful support of the T2_UA_KIPT center was provided. For the last year, more than 1.8 PB of the CMS data has been transferred for processing to the facility. This exceeds the total amount of experimental information transferred to the site for all previous time of its participation in the distributed LHC data processing. (In total, ~3.5 PB of CMS data has been transferred to the T2_UA_KIPT center for processing since the LHC startup.) In spite of the hardware upgrade accomplished in 2017, the KIPT Tier-2 center, by its computing and disk resources, is still well (by factor of ~3 - 3.5) below the CMS requirements. Nevertheless, a high quality of its operation was provided during 2017. By the beginning of December, the T2_UA_KIPT support in 2017 had been already accounted for within the CMS as 5.42 months of EPR ('Experiment Physics Responsibility') obligation fulfillment, what is a quite satisfactory result. In 2017, an intensive work was also completed on the physics analysis of data collected in the CMS experiment. A search of SUSY particles was carried out based of the analysis of the complete event sample (proton-proton collisions at 13 TeV) recorded in 2016. This data sample corresponds to 35.4 fb-1, what is by more than an order of magnitude greater than the sample that we processed in 2016. Events with large missing transverse momentum ETmiss and a reconstructed opposite-sign high transverse momentum lepton pair (ee, e , or ) were selected. Possible processes leading to such a signature include production of opposite-sign slepton or chargino pair in the intermediate state. The event selection criteria were optimized to provide "optimal" conditions for observation of signals been looked for (so-called signal regions). Estimation of the systematic uncertainties was performed through formation of control event samples for each of the background contributions with determination of corresponding control kinematic regions. In case of final states with the same-flavor leptons, a way of the analysis was chosen which is based on formation of a flavor-symmetric background event sample (including, in particular, production of double ( t t) and single (tW) top quarks, as well as pairs WW and WZ, if in the latter case one of the 2 reconstructed leptons is a W decay product). A statistical analysis was carried out with providing elimination of a lot of slepton, chargino and neutralino 01 mass combinations at the confidence level of CL=95%. The work on the CMS detector endcap hadronic calorimeter (HCAL) upgrades was continued. With the aim of searching for promising radiation-resistant scintillation materials for the CMS hadron calorimetry, a study of radiation properties of single-crystal YSO:Ce and YAG:Ce scintillators and composite scintillators based on them was performed. The results confirm that, compared to plastic scintillators presently used in the HCAL, YSO:Ce and YAG:Ce provide a high radiation hardness and considerably greater light yield. However, they are featured with a substantially greater signal decay time, what appears to be essentially restrictive for prospects of their usage in the LHC experiments. A study of the induced radioactivity in the YSO:Ce and YAG:Ce samples has been carried out. A conclusion was made that irradiation of these samples by bremsstrahlung photons results in activation due to production of the 141Ce, 139Ce and 88Y isotopes. These isotopes have sufficiently big decay time to become a source of additional difficulties in particle registration with a detector based on such composite scintillators in case of their usage in places subjected to high irradiation doses. The results obtained within fulfillment of this project were discussed with CMS experts and reported at the corresponding meetings at CERN.
Product Description
popup.authors
Горбенко Євген Степанович
Кліменко Кім Олександрович
Ковальова Людмила Семенівна
Куров Олексій Олександрович
Левчук Леонід Геннадійович
Лук'яненко Сергій Тимофійович
Попов Віктор Пилипович
Приставка Олександр Сергійович
Сорока Дмитро В'ячеславович
popup.nrat_date
2020-04-02
