Events

CHEP-Yerevan-2025 summing up: continue by getting better

On 29 September – 3 October, the International Conference on High Energy Physics (CHEP-Yerevan-2025) was held in Yerevan, Armenia. The event was organized by Yerevan State University (YSU), A. Alikhanyan National Science Laboratory (AANL) ), and the Joint Institute for Nuclear Research (JINR). In addition to MLIT representatives, the Program Committee included scientists from VBLHEP, DLNP, BLTP JINR, and scientific organizations from around the world. This is the second conference in this series; the first took place in 2023 at AANL.

Nearly 80 scientists from Armenia, Belarus, Germany, India, Iran, Mexico, Russia, the USA, and Uzbekistan, as well as JINR and CERN representatives, participated in CHEP-Yerevan-2025. JINR was represented by a large delegation of about 30 specialists from four Laboratories, namely, VBLHEP, DLNP, BLTP, and MLIT. International experts gathered at YSU and AANL to discuss the current state of research in high-energy physics, including physics at the Large Hadron Collider (LHC)), Higgs boson physics, high-energy muon physics, physics beyond the Standard Model, hadron spectroscopy, heavy ion physics, spin physics, as well as advanced computational and analytical tools employed in experiments at the LHC, SPS, NICA, KEK, CEBAF, and other facilities.

YSU Vice-Rector for Scientific Affairs Rafayel Barkhudaryan opened the conference. “It is a great honor for me to welcome all participants at Yerevan University, a place with rich scientific traditions,” Rafayel Barkhudaryan said. “May your discussions be fruitful, your ideas inspiring, and may your professional interaction grow into strong scientific ties. I hope that this conference will give new impetus to our shared efforts to expand the horizons of knowledge.” Rafayel Barkhudaryan pointed out that YSU aimed to engage young people in science, and holding scientific conferences such as CHEP-Yerevan-2025 could serve these goals, as well as enhance the university’s visibility in the global scientific landscape.

Welcoming the participants, AANL Director Gevorg Karyan said: “Two years ago, in 2023, we met for the first time at the first Conference on High Energy Physics in Yerevan. We then decided to continue this series of events, and today we can see that we have kept our word.” Gevorg Karyan introduced the audience to the history of the National Laboratory’s development from the foundation of the Yerevan Physics Institute to the present day and discussed AANL’s current objectives in the field of high-energy physics.

Chairman of the CHEP-Yerevan-2025 Organizing Committee, AANL Lead Researcher, and Head of the YSU Department of Nuclear Physics and Astrophysics Armen Tumasyan also welcomed the participants. “AANL in Armenia occupies a highly strong position in physics at the Large Hadron Collider. We are able to achieve this largely thanks to the active support we receive from the Dubna scientific community,” Armen Tumasyan, who is also the head of the AANL scientific group in the CMS experiment at the LHC, underlined in his commentary.

Director of the JINR Meshcheryakov Laboratory of Information Technologies Sergei Shmatov delivered a speech at the CHEP-Yerevan-2025 opening. “MLIT not only provides computational support for all JINR scientific projects, but also actively participates in the elaboration of methods, models, and scenarios for data processing and analysis. These tasks are impossible to perform without a deep understanding of the state of affairs in experimental projects, what objectives are set, and how research is conducted. I believe the future lies precisely in this kind of synergy between IT specialists and high-energy physics experts. Without this, substantial results cannot be achieved,” he emphasized.

Based on the organizers, the event is designed as an international platform where scientists involved in obtaining and processing experimental data in high-energy and particle physics can meet, present their findings, and discuss plans for future investigations. “We are talking about theoreticians and physicists who perform analysis, as well as specialists who build detectors, develop computational methods, algorithms, and create computing complexes, which plays a crucial role in experimental data processing,” Sergei Shmatov noted. According to MLIT Director, the fact that CHEP-Yerevan-2025 is discussing experiments and facilities that can be included in international projects with JINR’s participation in the future, for example, CEPC in China or SHiP at CERN, is of particular importance.

The CHEP-Yerevan-2025 scientific program opened with a report by JINR BLTP Director, RAS Corresponding Member Dmitry Kazakov, who presented a comprehensive overview of the current state of high-energy physics from a theoretician’s perspective. Dmitry Igorevich noted that he had been a regular participant in conferences held by RDMS CMS for many years and views the scientific event in Yerevan as a natural continuation of this series of activities at the intersection of theory and experiment, aimed at physicists involved in the Standard Model’s phenomenology and the experimental search for new physics beyond it.

Dmitry Kazakov formulated a list of unresolved problems and open questions in the standard model of interactions that inevitably lead to the existence of new physics and highlighted the diversity of approaches and research tools for its search. The traditional tools are particle accelerators, the largest of which is the Large Hadron Collider, whose annual news, unfortunately, does not provide any indication of new particles and interactions, but merely sets constraints on the parameters of the theoretical models that predict all of this. The second subject of study at the LHC is the Standard Model itself and its precise testing, and here various indications of deviations from theoretical expectations arise from time to time, but they all eventually disappear. Although sometimes events that are not reducible to avoidable experimental errors do occur, for example, the recent observation of toponium, a bound state of top quarks and antiquarks on the production threshold. In addition to the LHC, news for the scientific community also comes from highly specialized accelerators that operate at significantly lower energies, yet enabling to precisely investigate, for instance, the parameters of the Cabibbo-Kobayashi-Maskawa mixing matrix in the quark sector and closely related issues of CP violation in the early Universe. Such experiments also make it possible to establish precise limits on the rare decays of heavy mesons and baryons to which new physics may contribute.

Another major area is non-particle accelerator-based research: neutrino observatories, experiments searching for axions and anomalous magnetic moments of particles, etc. Important constraints on the properties of neutrinos come from astrophysical experiments, particularly those studying the anisotropy of the cosmic microwave background. The map of microwave background photons encodes a huge amount of information about the early Universe, the particles and the interactions that occurred then, and this indirect method can be employed to obtain estimates of neutrino masses. Another source is the investigation of the accelerating expansion of the Universe using “standard candles”, Type Ia supernovae, from which both the estimate of the total density of the Universe and the upper estimate of the neutrino contribution are taken. The problem of determining the type (Dirac or Majorana) and source of neutrino masses, the hierarchy of neutrino masses of the three generations, direct or inverse, and the parameters of mass matrix mixing are among important unresolved problems. Here, great hopes are placed on the next generation of experiments with reactor, astrophysical, and accelerator neutrinos, although a breakthrough in our knowledge on this issue will have to wait a little longer, as all of them are still in the preparatory stage.

News of experiments dedicated to the search for gravitational waves evokes a lively response from theoreticians and, in general, from people engaged in the search for new physics. Although this area is not directly related to high-energy physics, like astrophysics, it is closely intertwined with it and holds great potential for finding answers to the large and complex questions mentioned above, especially those related to the structure of the early Universe. It would be desirable for JINR physicists to participate more broadly and deeply in this activity, at least in the European part of the joint gravitational project, LIGO-Virgo-KAGRA.

Participation in the NICA project is of great interest to the JINR scientific community. The news is highly encouraging and raises hopes that the accelerator will start operating according to its planned scientific program in the near future. This is especially relevant now, when participation by Russian scientists in international projects is difficult. It is therefore particularly gratifying to hear about the achievements of our own homegrown project at this conference.

The theoretical focus of the conference continued with a series of talks devoted to issues from the list of unresolved problems and challenges of the Standard Model. The problem of dark matter and its description, the problem of scale hierarchy, perturbation theory computations, the accounting of higher-order corrections that contribute to observability estimates and refine accuracy criteria for new physics processes, and a number of other topics were covered. Viktor Kim (PNPI) presented his own vision of calculating corrections to the Higgs boson mass and the associated criteria for the naturalness of the Standard Model. The topic of dark matter, the most mysterious object in the Universe, about which all that is known is that it exists, and there are many various theories proposing their candidates for this role, but there is not a single fact or experimental result that allows one to prefer one of the theories, was touched upon in two reports. RAS Corresponding Member Dmitry Gorbunov (INR RAS) delivered a talk on calculating contributions from Standard Model strong interactions to possible processes linking ordinary matter (visible sector) with dark matter. New exotic light particles in a mass range suitable for study in specialized accelerator and non-accelerator experiments, such as the SHiP project, were considered as “linkers”, or carriers of interactions between the dark and visible sectors. Furthermore, refining calculations using models of low-energy strong interactions are common to all fixed-target experiments and can be useful both in evaluating the observability of effects at planned facilities and in potentially adjusting the limits on the production of light exotic particles already obtained by experimental collaborations. The report discussed various types of carriers, or portals to dark matter, since there are currently no selection criteria or experimental evidence to support a preference for one model over the others, so all options are valid. In the commentary on the report, it was pointed out that, when talking about dark matter, we basically knew very little, and that was not surprising. The history of particle physics as such is not very long, only about a hundred years old. Furthermore, the visible part of matter described by the Standard Model, i.e., what we know, makes up less than 5 percent of the total composition of the components of the Universe that form its density. It is therefore not surprising that new physics can manifest itself in various forms and in a multitude of ways. “It was very interesting to discuss strong interactions under various kinematic conditions at this conference and compare my own estimates in various experiments with specialists working on them. In terms of the effectiveness of the discussions, this conference is comparable to a very good workshop,” Dmitry Gorbunov underlined. He highlighted new interesting results presented, such as the abovementioned observation of a bound state of toponium at the production threshold, the existence of which was largely unexpected by LHC collaborations, although it had been predicted by Russian theoreticians long ago. The significance of obtaining results and interpreting them for rare processes that may hide new, fascinating physics was also noted.

Maria Savina (BLTP) provided an overview of the situation with dark matter candidates in a slightly different mass range, namely, weakly interacting massive particles (WIMPs). She presented a set of scenarios for the dark sector’s structure that could be tested at the LHC.

Non-standard physics can manifest itself both directly, in the form of processes with new particles and interactions, and indirectly, through the search for deviations from the expectations of the Standard Model. In the second case, the highest possible accuracy in calculating standard processes using perturbation theory is of paramount importance. This topic always has its own unique resonance and was considered at the conference in reports on radiative corrections by JINR BLTP specialists Uliana Voznaya, Vladimir Zykunov, and Leonid Kaptari. In addition, Petr Krachkov (BINP SB RAS) gave a talk on a two-loop computation of electron-positron annihilation with the production of a pair of heavy leptons.

Along with new physics, the study of standard processes in unusual or extreme regimes is also of theoretical interest. In this vein, news on a well-known but still potentially surprising topic was presented by Misak Sargsian (Florida International University, USA) in his report on the spectral-functional approach to calculating the structure of hadrons. The exchange of pomerons and photons for high-speed p-A events at the LHC was the topic of a talk by Dmitry Sosnov (NRC KI). Anatolii Egorov (PNPI) continued this topic with potential applications at future colliders in a report on the results of investigations of high-speed jet pairs for the search for new physics. Andrei Zelenov (NRC KI) spoke about the role of diquarks in the production of large-pT hadrons in pp collisions.

Anna Dembitskaia (NRNU MEPhI) delivered an interesting talk, not related to colliders but to the ideas and methods of astrophysics. The possibility of the formation of an antimatter domain in the early Universe, its chemical evolution, and its persistent existence to this day was discussed.

The experimental section of reports devoted to testing the Standard Model and searching for new physics beyond it was extensive and diverse. This topic was started in Sergei Shmatov’s presentation, which reviewed the latest results on the search for physics beyond the Standard Model in the CMS experiment at the LHC. Later, news from the LHC on Higgs physics, observations of Standard Model processes, the search for new Higgs states, the search for dark matter particles, processes forbidden in the Standard Model, etc. were covered on different days of the conference. Soumya Mukherjee (University of California, San Diego, USA) enlarged upon current measurements of the characteristics of the Higgs boson. Artur Apresyan (Fermilab, USA) spoke about the search for the process of pair production of Higgs bosons and the prospects for its observation at the LHC in the high-luminosity mode (HL-LHC). Aliaksei Raspiareza (DESY, Germany) devoted his talk to the search for the heavy neutral Higgs boson. Yasaman Hosseini (Institute for Research in Fundamental Sciences, Iran) demonstrated results on the ttZ production. The theme of the CMS experiment was continued in reports by Alexander Lanyov (VBLHEP) on the investigation of a pair of muons in the final state, by Mojtaba Mohammadi Najafabadi (Institute for Research in Fundamental Sciences, Iran) on the search for neutral currents that change flavor in the decay of top quarks, by Alexandr Sedelnikov (MLIT) on the latest results in heavy quark physics, and by Aram Hayrapetyan (AANL) on the search for long-lived particles

On non-LHC topics, Cynthia Keppel (JLab) gave a talk on the opening day. She outlined the research areas and scientific infrastructure of the Jefferson Laboratory and shared a number of results. Dmitry Peshekhonov (VBLHEP) made an impressive presentation on the final key results of the NA64 experiment at CERN. Hrachya Marukyan (AANL) presented an overview of the latest GlueX results and future plans, and Prokhor Egorov (DLNP) spoke about glueball searches in the BESIII experiment. Ivan Logashenko (Budker Institute of Nuclear Physics) demonstrated the results of the CMD-3 experiment at the VEPP-2000 collider.

The NICA megascience project, JINR’s home experiment, its plans, and prospects were discussed throughout one conference day. The discussion started on the opening day with a report by JINR VBLHEP Acting Director Andrei Butenko, who spoke about NICA, the BM@N, MPD, and SPD experiments, and the current status of the accelerator complex. He underlined that to begin collecting and processing real physics data, physicists needed to prepare all the necessary data models, and his report aimed to provide an understanding of the first direction to move in. As Andrei Butenko explained, the cooling of the collider’s second semicircle will soon start, with work on cooling the Nuclotron ahead. The project team expects to obtain the first beams from the collider in December of this year. “Listening to theoretical talks, it becomes clear in which direction technological progress should move. For example, the report about the Jefferson Laboratory, its science, and its facilities was highly interesting. Conferences like these are essential for cross-checking, when specialists in theory, experimentation, and technology can meet for discussions and explore whether emerging ideas can be implemented. And this can be most effectively accomplished at offsite events, which allow one to immerse themselves in the conference’s work away from their daily routine,” Andrei Butenko emphasized.

On a separate day, a session dedicated to heavy ion physics featured a series of reports on the experiments at the NICA accelerator complex. JINR VBLHEP Chief Researcher and MPD Collaboration Spokesperson Viktor Riabov talked about the current status and physics program of the MPD experiment. JINR VBLHEP scientists also presented reports on the status of the BM@N (Vasilii Plotnikov) and SRC (Maria Patsuk) experiments. Luis Alberto Hernandez Rosas (National Autonomous University of Mexico (UNAM)) discussed the self-consistent efficient modeling of QCD matter under extreme conditions.

Alejandro Ayala (UNAM), a Mexican representative and Chairman of the Council of Institutes participating in the MPD collaboration, investigates the properties of strongly interacting matter. At CHEP-Yerevan-2025, he delivered a talk on the asymmetric emission of μ⁺μ⁻ from Z⁰ decays: a clear magnetometer in relativistic heavy-ion collisions. “This conference is interesting since it enables to become familiar with the current state of research in various fields of high-energy physics and learn about cutting-edge experiments. I was delighted to see a dynamic and vibrant scientific community here. This is a favorable environment for both establishing scientific contacts and working with partners. For example, we are discussing with MLIT Director the possibility of organizing data transmission channels between Dubna and Mexico for MPD experiment’s data processing,” Alejandro Ayala said. He pointed out that cooperation between Mexico and JINR was in the active development stage and, in addition to MPD, focused on joint research at the IBR-2 reactor and its spectrometer complex, as well as on the creation of an ion source in Mexico in collaboration with JINR specialists.

Within the heavy ion session, the following researchers presented their reports: Khusnuddin Olimov (Physical-Technical Institute of the Academy of Sciences of Uzbekistan) “Centrality and energy dependencies of kinetic freeze-out parameters in high-energy p+Pb, Xe+Xe, and Pb+P collisions at the LHC”; Amaresh Kumar Jaiswal (Jaiswal National Institute of Science Education and Research, Bhubaneswar) “Spin polarization relativistic heavy ion collisions”; Petr Parfenov (VBLHEP) “Feasibility study of anisotropic flow measurements in the fixed-target configuration of the MPD experiment”; Mikhail Mamaev (VBLHEP) “Directed flow of protons in Xe+CsI collisions at the beam energy of 3.8 A GeV with BM@N”; Khachik Abraamyan (VBLHEP) “Observation of structures at ∼ 17 and ∼ 38 MeV/c² in the γγ and e+e- invariant mass spectra in dCu collisions at a momentum of 3.8 GeV/c per nucleon”.

JINR MLIT staff members delivered talks on advanced computational and analytical tools. MLIT Deputy Director Nikolay Voytishin spoke about data processing methods and algorithms in high-energy physics. Danila Oleynik demonstrated the software and computing project for the SPD experiment, and Artem Petrosyan enlarged upon the management of Monte Carlo simulation in a distributed environment for the SPD experiment. Alexander Ayriyan discussed the application of machine learning for particle identification in the MPD and BM@N experiments.

Commenting on CHEP-Yerevan-2025, JINR MLIT Director Sergei Shmatov highlighted that participation in conferences of this level was an excellent opportunity for young scientists to showcase their scientific work. “Here, young specialists have the opportunity to interact with senior colleagues and better define their research interests,” Sergei Shmatov underlined. He also said that, starting this year, the traditional internship of young Armenian scientists at JINR had been expanded. Eight young physicists from the JINR Laboratories are currently interning at AANL. They are actively participating in CHEP-Yerevan-2025 not only as speakers but also by assisting in organizing the conference. The internship participants presented a number of reports on the CMS experiment. Ivan Migunov spoke about measuring the Higgs boson production in the VBF process and its decay into b-quarks in proton collisions at an energy of 13 TeV. Vladislav Shalaev (VBLHEP) reviewed the results of electroweak interaction emission at the LHC. Iurii Korsakov demonstrated approaches to searching for dark matter in invisible Higgs boson h125 decays. Kirill Slizhevskiireported on the dark matter particle production in extended 2HDM models. Ilia Zhizhin enlarged upon methods for modeling events and backgrounds using Monte Carlo at the LHC. Dmitry Budkovski’s talk focused on measuring the fraction of gluon jets in pp collisions at 13 TeV. Dmitrii Kozlov shared the results of an investigation of the operation of cathode-strip chambers under high background conditions. Aram Hayrapetyan (AANL), along with young scientists from other scientific organizations, discussed the search for long-lived particles in CMS. Multiparticle correlations in pp interactions at 13 TeV were considered by Artashes Chinaryan. Savelii Omelianchuk spoke on the topic of the experiments at NICA, presenting a graph neural network with an attention mechanism for clustering particle tracks by events in the SPD experiment.

Summing up, AANL Lead Researcher and Member of the JINR Scientific Council Armen Nersessian said: “The Yerevan Conference on High Energy Physics was held for the second time, but its level is clearly enhancing. This is confirmed by the fact that the number of participants in the hall did not decrease from the second day onward, as often happens. The conference hall was overflowing. I am confident that the conference will continue to develop and only get better.

Within the conference’s social program, the participants visited the Hovhannavank Monastery and the Saint Mesrop Mashtots Church.

The next CHEP-Yerevan conference is scheduled for 2027.