The STAR experiment at RHIC has been put into operation more than two decades ago and since then has provided unique data on relativistic heavy-ion collisions. One of the main topics of interest for ...STAR’s experimental program is related to the transition from regular hadronic matter to the quark–gluon plasma state. To shed light on the mechanism of such transition and its exact location on the QCD phase diagram, RHIC has performed two phases of the Beam Energy Scan program lowering collision energy from 200 to 3 GeV. Large-statistics samples obtained during BES-II program at both collider and fixed-target modes allow us to possibly locate the phase boundary and the Critical Point. This report will summarize results obtained from BES-I and new results from some of the BES-II energies. These results can help shape the physics programs of new experiments in the field (MPD@NICA, CBM@FAIR, JPARC).
Particle Identification (PID) is an important part for most of the physics analysis in heavy-ion experiments. The principal challenge for PID is to provide good identification in a wide range of the ...particle momentum. Different approaches are used to combine observations from various detectors to enrich overall PID capabilities. Since PID is a classification task it can be performed using Machine Learning (ML) approach which has a wide range of different models for classification task. Those methods can help to extend PID over the classical methods. This study has performed the optimal multilayer perceptron (MLP) classifier selection for particle identification.
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When interpreting the materials of the multizone satellite survey of Resource-P (Geotone) and Landsat-7 in the central part of the Chukchi Peninsula (Q-1-XV,XVI), structural elements of ...tectonic–volcanogenic genesis are revealed, represented by linear, arc, annular, and zonal-concentric lineaments of various ranks of different ages. The important role of ring structures and their dissecting disjunctiva, mainly of northeastern and submeridional strike, for the localization of gold mineralization is shown. The use of high-resolution satellite imagery allows us to outline the gold-prospective area of Erguveem-1, which is characterized by an increased density of lineaments and subvolcanic intrusions.
Centrality Determination in MPD at NICA Aparin, A.; Nieto-Marín, P. A.
Physics of particles and nuclei letters,
10/2022, Volume:
19, Issue:
5
Journal Article
Peer reviewed
We present a study of centrality classes determination based on number of charged particles registered with the Time Projection Chamber (TPC) in Multi-Purpose Detector (MPD) at NICA complex. Precise ...determination of centrality classes will allow one to select ion collisions within a certain class based on the initial impact parameter in order to study behaviour of variables on the mean energy densities reached in the certain event classes. It is important to study the QCD matter produced in the collisions with respect to the geometric properties of the collision between nuclei, but these properties cannot be directly measured. Therefore, we analyze in this work the centrality classes which are obtained using different sets of selection criteria for centrality calculations, which include the number of hits in the TPC pseudorapidity window and transverse momentum of registered particles in the TPC sub-detector for Bi+Bi collisions at
7.7, 9, and 9.46 GeV generated by the Ultra relativistic Quantum Molecular Dynamics (UrQMD) model.
This work presents results of the first tests of machine learning application using gradient boosting on oblivious decision trees to particle identification problem in Multi Purpose Detector (MPD) ...experiment on Nuclotron based Ion Collider fAcility (NICA) at Joint Institute for Nuclear Research. Categorical boosting (CatBoost) implementation of a gradient boosting on decision trees has been used. Particle identification was based on the information provided by the time projection chamber (TPC) and the time-of-flight (TOF) subdetectors. In the study three various Monte-Carlo datasets of measurements from TPC and TOF were simulated and used within CatBoost classifiers training and testing. The comparison was made with the
-sigma method which is currently used at MPD software. Gradient boosting shows better efficiency in case of small and large momentum values (
GeV
and
GeV
). This demonstrated that machine learning methods are well suited to address the particle identification problem in MPD experiment.
When decoding space sensing materials of the eastern part of the Chukchi Peninsula on a scale of 1 : 50 000, structural elements of tectonic–volcanogenic genesis are identified, represented by ...linear, arc, ring, zonal–concentric structural elements of various ranks. Ring structures up to 2 km in diameter and the faults cutting them, predominantly of northeastern and submeridional strike, control the localization of gold mineralization in the Pepenveemskii ore–placer zone. Based on the computer processing of ASTER IR space surveys in the Pepenveemskii zone, areas of development of hydrothermally altered rocks (berezites, secondary quartzites, and sericite–hydromica–quartz metasomatites) genetically associated with mineralization are identified. The use of high-resolution satellite imaging in combination with geophysical data has made it possible, on a scale of 1 : 10 000, to identify gold-prospective areas associated with volcano–dome structures, which are characterized by an increased density of lineaments and are associated with the formation of subvolcanic rhyolites.
To assess the capabilities of high-resolution multispectral satellite imagery in prospecting for coastal placers and deposits of hydrocarbons in the northern seas of Russia, the data from the Russian
...KFA-1000
and
Resurs-P
(geotone) spacecraft are used. This satellite imagery with a terrain resolution of 5 : 1 m makes it possible to carry out research on a scale of 1 : 25 000 to 1 : 5000 and opens up new opportunities for mineral exploration in the coastal zone, since it allows identifying structural units that control the location of coastal placers and hydrocarbon deposits.
Exploration of the hot and dense nuclear matter produced in collisions of heavy ions is one of the main goals of modern high energy nuclear physics. The Relativistic Heavy Ion Collider (RHIC) ...provides a unique opportunity to map the QCD phase diagram by colliding different nucleus species and varying the energy of collisions. RHIC has already begun the second phase of the Beam Energy Scan (BES) program, which will allow us to cover energy range for gold-gold collisions
GeV. The Fixed-target Program (FXT) will extend collision energy range available for the analysis down to
GeV. BES-II along with FXT will dramatically enhance our understanding of the QCD phase diagram in the broad range of baryon chemical potential,
, up to 720 MeV. Recent detector upgrades increase STAR’s acceptance both in rapidity and low transverse momentum, and extend its particle identification capabilities. With new detectors STAR can explore phase diagram with even higher precision hopefully reaching both the onset of deconfinement as well as the critical point. In this talk, we present the most recent results and future plans from the STAR experiment.
Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions ...and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean (M), variance (σ2), skewness (S), and kurtosis (κ) for net-kaon multiplicity distributions as well as the ratio σ2/M and the products Sσ and κσ2 are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.
In this letter, measurements of the shared momentum fraction (zg) and the groomed jet radius (Rg), as defined in the SoftDrop algorithm, are reported in p+p collisions at s=200 GeV collected by the ...STAR experiment. These substructure observables are differentially measured for jets of varying resolution parameters from R=0.2−0.6 in the transverse momentum range 15<pT,jet<60 GeV/c. These studies show that, in the pT,jet range accessible at s=200 GeV and with increasing jet resolution parameter and jet transverse momentum, the zg distribution asymptotically converges to the DGLAP splitting kernel for a quark radiating a gluon. The groomed jet radius measurements reflect a momentum-dependent narrowing of the jet structure for jets of a given resolution parameter, i.e., the larger the pT,jet, the narrower the first splitting. For the first time, these fully corrected measurements are compared to Monte Carlo generators with leading order QCD matrix elements and leading log in the parton shower, and to state-of-the-art theoretical calculations at next-to-leading-log accuracy. We observe that PYTHIA 6 with parameters tuned to reproduce RHIC measurements is able to quantitatively describe data, whereas PYTHIA 8 and HERWIG 7, tuned to reproduce LHC data, are unable to provide a simultaneous description of both zg and Rg, resulting in opportunities for fine parameter tuning of these models for p+p collisions at RHIC energies. We also find that the theoretical calculations without non-perturbative corrections are able to qualitatively describe the trend in data for jets of large resolution parameters at high pT,jet, but fail at small jet resolution parameters and low jet transverse momenta.
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