abstract

The \(B \rightarrow K\tau \ell \) decays (where \(\ell =e,\mu \)) are not allowed in the Standard Model (SM) at the tree level due to lepton flavor violation (LFV). In some New Physics (NP) models, their branching fractions are within the reach of the current experimental sensitivities. The Belle and Belle II experiments provide ideal conditions for their search. We used the basic kinematic constraints of the experiments to reconstruct them. A multivariate classifier score is used to model the signal and background. For the estimation of statistical upper limits (ULs), the Bayesian approach is used. To validate the analysis method, two control channel modes are used.

abstract

An intermediate 48 V to 11 V DC/DC conversion stage, located in Patch Panel 2 (PP2), constitutes a key element of the power delivery chain for the ATLAS Inner Tracker (ITk) Strip detector. The design, based on commercial off-the-shelf components, meets the detector constraints and radiation tolerance requirements. Pre-production DC/DC boards demonstrate efficiencies above 81% across the full load range and low output noise, confirming the robustness of the PP2 system.

abstract

During the summer of 2025, the LHC collided protons with oxygen, oxygen with oxygen, and neon with neon. The ATLAS experiment recorded these data with its Forward Proton detectors (AFP) inserted on both: the proton and ion sides. This allows access to many interesting studies with scattered fragments being tagged. A few analysis ideas are presented followed by preliminary studies of what could be visible in the AFP.

abstract

The anomalous magnetic moment of the muon is one of the promising sectors for probing New Physics. Recent results from \(g-2\) experiments indicate a possible deviation of about \(5\sigma \) from the Standard Model prediction. The MUonE experiment was designed to precisely measure the hadronic contribution to the muon anomalous magnetic moment, which could increase the significance to at least \(7\sigma \) and thereby confirm potential discovery. Several crucial milestones have already been achieved by the MUonE project, and the results of the ongoing 2025 test run analysis will serve as the foundation for the full-scale 40 station proposal to be implemented after the LHC Long Shutdown 3. However, classical event reconstruction will face a significant challenge due to combinatorial scaling in this final configuration. To address these challenges, the use of Graph Neural Networks (GNNs) is proposed for the pattern recognition stage, as they offer the flexibility to process irregular geometries while maintaining the low latency required for a trigger. This allows for robust track reconstruction even in scenarios where detector hits may be missing, ensuring accurate performance under imperfect or incomplete data conditions.

abstract

A successor to the PACIFIC front-end ASIC, currently used in the LHCb Scintillating Fibre (SciFi) Tracker, is being developed for the second foreseen upgrade of the LHCb experiment. The new ASIC, referred to as PACIFIC++, is implemented in 65 nm CMOS technology and extends the architecture of the existing PACIFIC, designed in 130 nm CMOS technology. The new design introduces a 10-bit ADC and a 6-bit TDC measurement in each channel, together with on-chip clustering. The PACIFIC++ is proposed for the readout of the Mighty SciFi Tracker and Magnet Station detectors in the LHCb Upgrade II. An 8-channel prototype version of PACIFIC++, called PACIFIC+8, including all key functionalities, is currently being prepared for submission. This paper discusses the PACIFIC++ architecture and its current state of development.

abstract

An overview of charm-quark hadronisation within the PYTHIA/Angantyr model is provided. The improvements to the junction formation and fragmentation mechanisms in the context of charm-quark hadronisation are discussed. We discuss these changes in the context of the recently developed global colour reconnection mechanism, which is based on the QCD-inspired colour reconnection model. We show the enhancement in \({\mit \Lambda }_c\) baryon yield in \(\pp \) and \(\pPb \) collisions at the LHC at \(\sqrt {s_{NN}} = 5.02\) TeV collision energy using the PYTHIA/Angantyr model.

abstract

Studies of the internal structure of hadrons have been a main focus in particle physics since perturbative Quantum Chromodynamics (p-QCD) was established as the theory of the strong interaction. While the constituent quark model provided a successful framework for the investigation of many hadrons, recent decades have unveiled exotic states that defy simple classification. An example is the \(X(6900)\) resonance, identified in the di-\(J/\psi \) mass spectrum by LHCb, ATLAS, and CMS. As a tetraquark composed of \(c\bar {c}c\bar {c}\), its existence confirms the possibility of such multi-quark states. Its fundamental nature — whether it is a compact diquark–antidiquark entity or a diffuse molecule of two charmonia — remains an open question. We propose a study for the exclusive \(\gamma \gamma \to X(6900)\) process, accessible in ultraperipheral heavy-ion collisions (UPCs), which serves as a clean probe to differentiate between these inner structures. In this work, we calculate the respective two-photon decay width, \({\mit \Gamma }_{\gamma \gamma }\), using a leading-order Non-Relativistic QCD (NRQCD) framework. The long-distance matrix elements are determined from the wave functions at origin obtained in an extended relativized quark model. For the \(X(6900)\) as a radially excited (\(2s\)) compact state, we predict sizable widths of \({\mit \Gamma }_{\gamma \gamma }(2^{++}_{2s}) \approx 0.22\) keV and \({\mit \Gamma }_{\gamma \gamma }(0^{++}_{2s}) \approx 0.15\)–0.69 keV. These values are significantly larger than expected for a molecular state, providing a clear experimental discriminant.

abstract

NA61/SHINE is a multipurpose fixed-target experiment located at the CERN SPS. One of its main goals is to study the onset of deconfinement and the properties of strongly interacting matter. For this purpose, a unique two-dimensional scan in collision energy (\(\sqrt {s_{NN}} = 5.12\)–\(16.8/17.3\) GeV) and system size (from \(p\)+\(p\) to Pb+Pb) was performed. Results on hadron spectra produced in nucleus–nucleus collisions, including the recent data on charged hadrons produced in central Xe+La collisions and baryons in central Ar+Sc collisions, are presented. The kinematic distributions and the measured multiplicities of identified hadrons are compared with NA49 Pb+Pb results and with available world data. The obtained results, particularly the \(K^+/\pi ^+\) ratio, are crucial for understanding the phenomena of the onset of deconfinement, which is one of the main aims of the strong interaction program of the NA61/SHINE Collaboration. Additionally, a comparison of proton rapidity spectra in nucleus–nucleus collisions from NA61/SHINE and NA49 is presented, providing a complete picture of the energy and system-size dependence of the mechanism of transport of baryon number at SPS energies.