ATLAS.
.
Upgrade of the ATLAS Detector and Physics Research at the LHC

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:

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), in particular, detailed study of the Standard Model, its application limits, search for answers to the key problems in particle physics and astrophysics, such as the origin of elementary particles masses, nature of the dark matter in the Universe, existence of extra dimensions, are carried out with the ATLAS detector. We participate in software development and in upgrade of the detector’s subsystems.

Brief annotation and scientific rationale:

The main goal of the ATLAS experiment is to study proton-proton interactions at unique LHC energies (7-14 TeV). These interactions are the source of many physical processes (including yet unknown) between elementary particles. Study of these processes and their theoretical description within unified point of view is the general aim of modern physics.

In particular, with the ATLAS detector is already used to scrutinise the current Standard Model of particle physics, investigate the limits of its applicability, and seek answers to the key questions of the present stage of development of physics and astrophysics, such as the nature of dark matter in the Universe, the presence of extra spatial dimensions, etc.

The multi-purpose detector ATLAS (like CMS) operating on the LHC, the most advanced collider in terms of the energy of colliding protons achieved under laboratory conditions, is a unique and unprecedented in its complexity physical device which, on the one hand, accumulates the most advanced achievements of modern science, engineering, technology and communication tools, and on the other hand, guarantees (by virtue of the aforesaid) attaining the main objective of its creation – production of entirely new knowledge about the world around us. Therefore, participation in a such large-scale international project as the ATLAS experiment at the LHC is absolutely necessary for such international organizations as our JINR. This gives access to the state-of-the-art technology and allows us to be involved in production of unique scientific results.

Expected results upon completion of the project:

Absolutely new and unique data will be obtained in multifaceted and comprehensive research of proton-proton scattering processes. The analysis of these data will allow several fundamental physical problems to be solved. Within this Project, JINR scientists will participate in this analysis.

It is expected to obtain new results and make publications on all above-mentioned tasks where JINR scientists have responsibilities. The most important tasks are the studies of the proton structure and hadron state spectrum, probing of the Standard Model at the LHC energies, search for and investigation of supersymmetry, search for the evidence of existence of new particles and new interactions. In addition, JINR intends to obtain new results that will help specify properties of already known elementary particles such as W and Zbosons, top quark, heavy baryons etc.

The implementation of this Project aimed at solving highly significant scientific problems will yield unique applied results which may significantly change the quality of life. Among these 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.

Expected results of the project in the current year:

1. Search for the chiral Z */W * bosons in the two-jet decays and in a process with more complex topology of their associative production including heavy b and t quarks.

2. Search for (supersymmetric) charged Higgs bosons via their specific decay modes (3-lepton, etc).

3. Analyses of associated productions of the SM Higgs boson with the top-antitop pair and search for production with a single top.

4. Search for a valence-like nonperturbative component of heavy quarks in the proton (intrinsic heavy quarks) via specific final state topology in the pp interactions.

5. Search for new hadrons and baryons containing heavy c and b quarks and study of their properties.

6. Measurement of the Drell-Yan triple-differential cross section and the effective leptonic weak mixing angle in the Z-boson decay.

7. New comprehensive study of the gluon structure of the proton, etc.

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

9. Participation in development of the event trigger indexing infrastructure.

10. Development and maintenance of the TDAQ system.

11. Development of database monitoring applications.

12. 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 in the current 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.