A two-particle channel in which an unbound nucleus of
8
Be in the ground state (
8
Be
g.s.
) was one of the fragments was selected among events where
12
C nuclei of momentum 4.5 GeV/c per nucleon ...undergo coherent dissociation into three alpha particles. The events in question were detected in a track nuclear photoemulsion containing lead nuclei, which was irradiated at the synchrophasotron of the Laboratory of High Energies at the Joint Institute for Nuclear Research (JINR, Dubna). The average transverse momentum of alpha particles produced upon the decay of
8
Be
g.s.
nuclei was 87±6 MeV/
c
, while that for “single” alpha (α
s
) particles was 123±15 MeV/
c
. The average value of the transverse-momentum transfer in the reaction being considered, Pt(12C), was 223 ± 20 MeV/
c
. The average value of the cross section for this channel involving Ag and Br target nuclei was 13 ± 4 mb, while the cross section for the reaction on the Pb nucleus was 40 ± 15 mb. The Coulomb dissociation contribution evaluated on the basis of the number of events where the momentum
P
t
(
12
C) did not exceed 0.1 GeV/c saturated about 20%. In nine events, the measured total transverse energy of the fragments in the reference frame comoving with the decaying carbon nucleus did not exceed 0.45 MeV, which did not contradict the excitation of the participant
12
C nucleus to the level at 7.65 MeV. The average value of the transverse momentum in those events was 234 ± 25 MeV/
c
.
A two-particle channel in which an unbound nucleus of {sup 8}Be in the ground state ({sup 8}Be{sub g.s.}) was one of the fragments was selected among events where {sup 12}C nuclei of momentum 4.5 ...GeV/c per nucleon undergo coherent dissociation into three alpha particles. The events in question were detected in a track nuclear photoemulsion containing lead nuclei, which was irradiated at the synchrophasotron of the Laboratory of High Energies at the Joint Institute for Nuclear Research (JINR, Dubna). The average transverse momentum of alpha particles produced upon the decay of {sup 8}Be{sub g.s.} nuclei was 87±6 MeV/c, while that for “single” alpha (α{sub s}) particles was 123±15 MeV/c. The average value of the transverse-momentum transfer in the reaction being considered, Pt(12C), was 223 ± 20 MeV/c. The average value of the cross section for this channel involving Ag and Br target nuclei was 13 ± 4 mb, while the cross section for the reaction on the Pb nucleus was 40 ± 15 mb. The Coulomb dissociation contribution evaluated on the basis of the number of events where the momentum P{sub t}({sup 12}C) did not exceed 0.1 GeV/c saturated about 20%. In nine events, the measured total transverse energy of the fragments in the reference frame comoving with the decaying carbon nucleus did not exceed 0.45 MeV, which did not contradict the excitation of the participant {sup 12}C nucleus to the level at 7.65 MeV. The average value of the transverse momentum in those events was 234 ± 25 MeV/c.
Purpose. A phenomenon called MOOC (Massive Open Online Course) plays a special, “revolutionary” role, introducing of online learning for all stages of the educational process. Today there are a lot ...of MOOCs, the largest of them: Coursera, edX, Udacity. In connection with the large amount of resources for additional education, a number of questions arise: “How to choose the suitable course as an additional education, how to use the capabilities of MOOCs to improve the quality of the educational process at the university, how to minimize the time for finding the desired course on different platforms?”The purpose of the work is to create a unified information resource that allows you to integrate relevant information from various MOOCs, to reduce the time for finding an appropriate online course for the user, and to raise awareness about new courses and popular specializations, related to information technology.Materials and methods. Web-service is designed as one of the components of the information-educational environment of the Institute of System Analysis and Management. It is aimed at different groups of users: “motivated” students, “unmotivated” students, and lecturers.The initial data for the service is open information about the current online courses on the MOOCs Coursera, edX and Udacity.Each project has its own API, which allows you to get information about online courses. Since MOOCs do not have a common vocabulary in order to use it for searching, there is the problem of creating such a dictionary. To do this we use the Stack Exchange resource (stackexchange.com). The list of keywords is formed through the Stack Exchange API – we select the most popular tags on sites softwareengineering.stackexchange.com and cs.stackexchange.com.Results. As the first stage of implementation, a web application was developed that allows you to view and filter the lists of courses and to see detailed information about the courses.Conclusion. Today there are alpha-versions of two web-services within the information-educational environment of the Dubna State University. The first one is the web-service for collecting and analyzing data on the vacancies of specialists in the field of information technologies from the most popular Internet resources and the webservice that allows integrating information about online courses from the leading MOOC-sites.
We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of 40 AGeV. The observed pair yield integrated over the range of invariant masses ...0.2<m</=1 GeV/c(2) is enhanced over the expectation from neutral meson decays by a factor of 5.9+/-1.5(stat)+/-1.2(syst data)+/-1.8(syst meson decays), somewhat larger than previously observed at the higher energy of 158 AGeV. The results are discussed with reference to model calculations based on pi(+)pi(-)-->e(+)e(-) annihilation with a modified rho propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the rho are more driven by baryon density than by temperature.
Results are presented of a two-pion interferometry (HBT) analysis in Pb+Au collisions at 40, 80, and 158
A
GeV. A detailed study of the Bertsch–Pratt HBT radius parameters has been performed as ...function of the mean pair transverse momentum
k
t
and in bins of the centrality of the collision. From these results we extract model-dependent information about the space–time evolution of the reaction. An investigation of the effective volume of the pion emitting system provides an important tool to study the properties of thermal pion freeze-out.
Differential triangular flow, v3(pT), of negative pions is measured at sNN=17.3 GeV around midrapidity by the CERES/NA45 experiment at CERN in central PbAu collisions in the range 0–30% with a mean ...centrality of 5.5%. This is the first measurement as a function of transverse momentum of the triangular flow at SPS energies. The pT range extends from about 0.05 GeV/c to more than 2 GeV/c. The triangular flow magnitude, corrected for the HBT effects, is smaller by a factor of about 2 than the one measured by the PHENIX experiment at RHIC and the ALICE experiment at the LHC. Within the analyzed range of central collisions no significant centrality dependence is observed. The data are found to be well described by a viscous hydrodynamic calculation combined with an UrQMD cascade model for the late stages.
We report on results of a measurement of meson production in central Pb-Au collisions at E(lab) = 158A GeV. For the first time in the history of high energy heavy-ion collisions, phi mesons were ...reconstructed both in the K+K- and the dilepton decay channels in the same experiment. This measurement yields rapidity densities near midrapidity, from the two decay channels, of 2.05 +/- 0.14(stat) +/- 0.25(syst) and 2.04 +/- 0.49(stat) +/- 0.32(syst), respectively. The shape of the measured transverse momentum spectrum is also in close agreement in both decay channels. The data rule out a possible enhancement of the phi yield in the leptonic over the hadronic decay channel of a factor 1.6 or larger at the 95% C.L. This rules out the discrepancy reported in the literature between measurements of the hadronic and dimuon decay channels by two different experiments.
The article gives the concept of the Electronic Educational Environment for training in the IT field of study that allows to build individual learning strategies according to fast changes in the ...labor market. The structure of the Electronic Educational Environment includes analytical services allowing to receive a list of the most demanded positions, related information technologies and competences. The strategy of creation of the Electronic Educational Environment on the basis of the Institute for System Analysis in Dubna University is described.
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