The Pierre Auger Observatory, the world’s largest observatory of ultra-high-energy cosmic rays (UHECR), offers a unique insight into the properties of hadronic interactions occurring in air showers at energies well above those reached at human-made accelerators. The key probe into the hadronic interactions has, for a long time, been the number of muons arriving at the ground, which can be directly measured at Auger for energies up to 10 TeV using dedicated underground muon detectors or estimated through the observation of highly inclined showers using the surface detector of the Observatory. Further information can be obtained using the hybrid character of the Observatory, which allows the simultaneous observation of the longitudinal development of the shower with the fluorescence (and lately also radio) detector and the ground signal with the surface detector. Several different analyses using hybrid data show a discrepancy between the predictions of simulations based on the latest hadronic interaction models and data. This discrepancy has been long interpreted as a deficit in the number of muons predicted by the simulations with respect to the data. A new analysis using a global fit of the data on selected hybrid showers has shown that the disagreement between models and data is more complex and also involves the predictions for the depths of the maxima of the longitudinal shower development. At the same time, measurements of shower-to-shower fluctuations using inclined hybrid events show good agreement with the predictions, suggesting that the observed muon discrepancy is rather the result of a gradual accumulation of small changes during the shower development than of a major change in the properties of the first interaction. Recently, the Observatory has undergone an upgrade, which includes several components aimed at a significant improvement in the measurement of the muon content of the air showers.

A dip-bump structure in the squared four-momentum transfer (t) distribution of proton’s single and double diffractive distributions is predicted around t ≈ −4 GeV2 for single diffractive distribution at LHC energies.

Light-by-light scattering is a relatively new area in experimental physics. Our recent, theoretical research shows that studying two photon measurements in regions with lower transverse momentum (pt,γ) and invariant mass (Mγγ) allows us to observe not only the main contribution of photon scattering, known as fermionic loops, but also mechanisms like the VDM–Regge. In addition, examining diphoton measurements in low invariant mass regions is crucial for researching light meson resonances in γγ → γγ scattering. We also focus on the interference between different contributions. For future experiments with the ALICE FoCal and ALICE 3 detectors, we have calculated background estimates and explored possibilities to minimize their impact.

New Trends in High-Energy Physics is a series of conferences initiated by the Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine in 1992. It is focused on topical problems in experiment, phenomenology and theory of particle, nuclear and astroparticle physics. The conferences were held yearly or biannually at various sites in Ukraine and abroad, namely in Kyiv, Alushta, Yalta, Novy Svit, Odesa (Ukraine), Sukhumi (Georgia), Budva/Beˇci´ci (Montenegro), and Natal (Brazil).

We investigate the high-energy behavior of the elastic scattering amplitude using the eikonal and U -matrix unitarization schemes. This work extends the analysis in [1] by exploring the sensitivity of the Pomeron and Odderon parameters to the inclusion of differential cross section data over an extended range of |t|.

The sPHENIX experiment is a new experiment and its new detector of Relativistic Heavy Ion Collider (RHIC) in the Brookhaven National Laboratory. It is an upgrade of the PHENIX experiment. The sPHENIX is to complete the scientific mission of RHIC in the study of QGP and the spin structure of the proton. The sPHENIX detector provides precision vertexing, tracking and electromagnetic and hadronic calorimetry in the central pseudorapidity region |η| ≤ 1.1, with full azimuth coverage, at the full RHIC collision rate, delivering unprecedented data sets for hard probe tomography measurement at RHIC. The sPHENIX was commissioned using Au + Au collision in 2023, and took physics data with transversely polarized proton + proton collisions at the center-of-mass energy of √S = 200 GeV in 2024. The status of detector commissioning and achieved physics targets of the proton spin program using the sPHENIX detector will be discussed.

Ultraperipheral collisions (UPCs) of heavy ions are a useful probe to study nuclear parton distribution functions (nPDFs) and, in particular, to characterize nuclear matter at Bjorken x < 10−3 and low squared momentum transfer Q2 (shadowing/saturation regime). In order to fully exploit these collisions, dedicated triggers on such event topologies were developed for the heavy ion data-taking period in 2023 by the CMS experiment. These triggers relied on the possibility of using the Zero Degree Calorimeter (ZDC) as a level-1 (L1) trigger detector for the first time. As a result, they allowed for an improved selection performance in addition to existing UPC triggers (as well as minimum-bias hadronic triggers), and enabled the study of hard processes (jets and heavy flavor hadrons) in photon-photon (γγ) and photon-nucleus (γN) scatterings [1].

After a brief introduction of the odderon, we will describe its experimental discovery by the D0 and TOTEM collaborations by comparing pp and pp- elastic scattering data and by combining it with the ρ and total cross section measurements by the TOTEM collaboration.

We recall a resummation procedure in QED to extract the zero momentum mode in soft photon emission and present an ansatz about a possible mechanism for the forward peak characterizing elastic proton proton scattering.

In recent years, certain experimental results from small collision systems (e.g. p-p, d-Au, p-Pb) at the RHIC and LHC have been reinterpreted as evidence for the formation, therein, of a dense flowing medium (QGP) despite small collision volumes. Systems that had been assigned as simple references (e.g., cold nuclear matter) for larger A-A collisions would then no longer play that role. This article examines conventional interpretations of certain data features in the context of a two-component (soft + hard) collision model. Specific topics include centrality determination for p-Pb collisions, interpretation (or not) of nuclear modification factors, significance of claims for strangeness enhancement, and interpretation of the “ridge” in p-p collisions. For p-p and p-Pb data analysis results indicate that p-Pb collisions are simple linear superpositions of p-N collisions, and N–N collisions within small systems generally follow simple and consistent rules. However, there is more to be learned about “basic” QCD in small systems with improved analysis methods.