Participating countries and international organizations:
Armenia, Azerbaijan, Belarus, Bulgaria, Canada, CERN, Czech Republic, France, Georgia, Germany,  Israel, Italy, Netherlands, Russia, Slovakia, Spain, USA.


The problem under study and the main purpose of the research:
Studies of the proton-proton interactions at unprecedented collision energies (up to 14 TeV), in particular, investigation of the nucleon structure, measurements of the Higgs-boson properties, searches for new phenomena beyond the Standard Model, studies of the heavy quarks and multiquark states, precision Standard Model tests, participation in software support of the ATLAS experiment, modelling of the physical processes and upgrade of the detector systems.

 Projects:

Brief annotation and scientific rationale:
The main purpose of the international ATLAS experiment is investigation of  proton-proton interactions at unprecedented energies at the LHC collider (from 7 to 14 TeV center-of-mass energy). These interactions are the source of different (including unknown) physical processes between elementary particles. Study of such processes and their description within a common framework represent the main problem of the modern physical science.

The ATLAS experiment is performing a number of precision tests of the Standard Model, probing the limits of its validity and searching for the answers to the key questions of the modern physics like the nature of the dark matter, existence of additional spacial dimensions, etc.

The ATLAS multipurpose facility is unique and unprecedented w.r.t. its performance and complexity. It combines the most up-to-date advances of science, technology and communication. Participation in such large-scale international project gives access to the cutting-edge technologies of the physical experiment, gaining experience in real data analysis, precision modelling of the physical processes, software and theoretical support of experiment and looks absolutely necessary for such international organisation as JINR.

Expected results upon completion of the project:
Analysis of pp-collisions data at 13.6 TeV as well as High-Luminosity LHC (HL-LHC) data are going to provide the new and unique experimental results. The most important among them are -- investigation of the proton structure, in particular, the transverse momentum density of gluons in proton; studies of the heavy hadron spectra, including beauty mesons and exotic tetraquark and pentaquark states; precision SM tests at LHC energies and searches beyond the SM. High Luminosity regime of LHC will allow studies of the rare processes, e.g., Higgs-boson production in association with single top-quark.

Achieving these goals is impossible without developing new methods of data processing analysis. The active participation of JINR physicists is planned in the trigger software support, developing new methods of detector simulation, application of the machine learning techniques in physics analysis.

The implementation of this Project aimed at solving highly significant scientific problems will yield unique applied results. Among these 'byproduct' results are the experience in operation of remote monitoring systems for technically complicated devices, big data processing and development and practical use of distributed comtputing systems (GRID) and database monitoring applications in long-term large-scale experiments. Applications of this experience if possible in other JINR projects.

Expected results of the project this year:
Study of the resonant Jpsi pairs production, probing of the fully-charmed tetraquark models describing these processes.

Studies of the hidden-charm tatraquark states in B-hardron decays to Jpsi + light hardon tracks.

Analysis of the Higgs boson production in association with single top quark.

Measurements of the heavy beauty meson properties, in particular, Bc-meson excited states.

Predictions and measurements of the gluon transverse momentum density in proton.

Search for quantum black holes in the lepton+jet channel at 13 TeV.

Higgs boson production in association with vector W, Z bozons studies.

Development and support of the ATLAS software.

Development of database monitoring applications.

Simulation studies of the ATLAS colorimeter response.

Participation in the Phase-2 ATLAS Upgrade Project of the muon spectrometer and calorimeters.

Brief annotation and scientific rationale:
The second phase of the ATLAS detector upgrade is aimed at preparing the facility for operation in the conditions of high luminosity of the LHC. During the first phase, which was successfully completed in 2022, the main contribution of the JINR group was participation in the implementation of the project to create a new muon wheel, an important element of the muon spectrometer. The modernization of the muon spectrometer continues in terms of creating RPC cameras. The development, testing and manufacturing of a system for reading signals from a liquid-argon calorimeter (LAr) based on fiber optic technology is underway. With the participation of JINR, a new high-granularity timing detector (HGTD) is being developed.

Expected results upon completion of the project:
Completion of the modernization of the detector systems will ensure stable and efficient operation of the ATLAS facility with the LHC luminosity at a level 5-7 times higher than the design value of about 10³⁴ cm^-2 s^-1, and collecting full statistics at the level of 3000 fb^-1 .

Expected results of the project this year:
Development and prototyping of the RPC cameras. Creation of fiber optic cables for the LAr test bench. Creation of a tooling prototype for HGTD assembly.

Collaboration