New articles on High Energy Physics - Experiment


[1] 2603.13592

Measurement of the $t$-channel single top quark cross section in proton-proton collisions at $\sqrt{s}$ = 5.02 TeV

The single top quark $t$-channel production cross section is measured in proton-proton collisions at the CERN LHC at $\sqrt{s}$ = 5.02 TeV, using data recorded with the CMS detector in 2017, corresponding to an integrated luminosity of 302 pb$^{-1}$, and resulting in the first CMS measurement of the process at that energy. Events with one electron or muon and two or more jets, among which at least one is identified as originating from a b quark fragmentation, are analyzed. The combined cross section of single top quark (tq) and single top antiquark ($\mathrm{\bar{t}q}$) production is $\sigma_{\mathrm{tq+\bar{t}q}}$ = 25.4$^{+3.6}_{-3.5}$ (stat) $^{+4.2}_{-3.9}$ (syst) $\pm$ 0.5 (lumi) pb. The individual cross sections are measured to be $\sigma_{\mathrm{tq}}$ = 17.6$^{+2.8}_{-2.7}$ (stat) $^{+2.6}_{-2.4}$ (syst) $\pm$ 0.3 (lumi) pb and $\sigma_{\mathrm{\bar{t}q}}$ = 6.6$^{+2.4}_{-1.6}$ (stat) $^{+2.1}_{-2.5}$ (syst) $\pm$ 0.1 (lumi) pb. Their ratio is measured to be $\mathcal{R}_{\mathrm{t-ch}}$ = 2.7$^{+1.5}_{-0.8}$ (stat) $^{+1.3}_{-0.3}$(syst). The absolute value of the Cabibbo$-$Kobayashi$-$Maskawa matrix element is found to be $\lvert f_{\mathrm{LV}}V_\mathrm{tb}\rvert$ = 0.92 $\pm$ 0.09 (exp) $\pm$ 0.01 (thy). The measurements are in good agreement with the standard model predictions at next-to-next-to-leading order accuracy in quantum chromodynamics.


[2] 2603.13593

Measurements of the electron neutrino-argon differential cross section without pions in the final state in MicroBooNE

We present a new measurement of the electron neutrino charged current cross section on argon without pions in the final state. This measurement uses the full MicroBooNE Booster Neutrino Beam dataset of $1.3\times 10^{21}$ protons on target collected at Fermi National Accelerator Laboratory. Events are considered both with and without protons above the kinetic energy visibility threshold. Differential cross sections are extracted in proton and electron kinematics, including energy and angle relative to the neutrino beam direction. The relationship between the hadronic and leptonic systems is explored through the angle between the proton and electron directions. The resulting cross sections are compared to a variety of available generator predictions using different models of neutrino interactions. We find good agreement with most models in lepton kinematics and some discrepancies in the hadronic system modeling, particularly in proton angle.


[3] 2603.13852

AMD Versal AI-Engines for fixed latency environments

Complex, high-throughput data acquisition and processing systems, such as those used in high-energy physics experiments, are increasingly moving sophisticated pattern recognition and data compression algorithms closer to the sensors themselves. To meet these needs, programmable device manufacturers offer multi-silicon die packages that commonly include dedicated co-processors within the same package. We present a technical study of a new family of such co-processors from AMD Xilinx, the Adaptive Intelligence (AI) Engine, or AIE, as part of the Versal architecture. Specifically, we focus on the deployment capabilities of AIEs in fixed latency environments such as those typically found in colliding beam experiments like those at the Large Hadron Collider. We evaluate the performance of a vectorised implementation of both a Boosted Decision Tree (BDT) and a Convolutional Neural Network (CNN), thereby demonstrating the feasibility of deploying AIEs for ML applications in such environments and their use as possible alternatives to traditional programmable logic-based implementations.


[4] 2603.13965

Dark Matter Search with the DEAP-3600 Detector using the Profile Likelihood Ratio Method

We present here a search for WIMP dark matter using 790.8 live-days of data collected with 3269 kg of liquid argon (1266 kg fiducial) by the DEAP-3600 detector at SNOLAB, using the Profile Likelihood Ratio method. The likelihood model is based on three parameters: estimated energy, pulse-shape discrimination parameter, and reconstructed position within the detector. Using this method, the expected signal sensitivity of DEAP-3600 benefits from an increased fiducial volume and improved event selection acceptance. Alpha-decays from a small number of dust particulates circulating within the liquid argon target are the dominant source of background events and limit the sensitivity of this search. This result provides improved exclusion upper limits on the WIMP-nucleon spin-independent cross section on liquid argon for WIMP masses between 20 GeV/$c^{2}$ and 100 GeV/$c^{2}$. At 100 GeV/$c^{2}$ the observed limit is 3.4 $\times$ 10$^{-45}$ cm$^2$ at 90% confidence level.


[5] 2603.14878

Dressed-State Spectroscopy of Proton Spins in Water Beyond the Rotating-Wave Approximation

The quantum Rabi model provides the framework for describing a two-level system interacting with a strong oscillating field beyond the rotating-wave approximation. We report the first experimental observation of the resulting dressed states of proton spins in water, realized using a Rabi-type setup with a strong off-resonant magnetic dressing field. The measured resonance spectrum exhibits multiple spin-state transitions involving several dressing-field quanta, including higher-order resonances predicted by the quantum Rabi model. The dressed-state energies show excellent agreement with theoretical expectations, extending dressed-state spectroscopy to proton spins and opening new possibilities for precision spin manipulation in nuclear magnetic resonance and related precision measurements.


[6] 2603.15007

Reinterpretation of searches for supersymmetry in models with variable R-parity-violating coupling strength using the full ATLAS Run 2 Dataset

A collection of thirteen ATLAS searches for supersymmetry (SUSY) models, optimized for R-parity-conserving (RPC) and R-parity-violating (RPV) SUSY, are reinterpreted in SUSY models with variable RPV coupling strength, which determines whether the lightest supersymmetric particle decays promptly or is long-lived. The dataset corresponds to an integrated luminosity of 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV collected between 2015 and 2018 by the ATLAS detector at the Large Hadron Collider. Limits are set at 95% confidence level on the mass of pair-produced gluinos decaying to final states enhanced or depleted with top quarks, and on the masses of pair-produced top squarks, tau-sleptons, or charginos and neutralinos. In a model of pair-produced gluinos decaying to final states enhanced with top quarks, a lower limit of 1.8 TeV on the gluino mass is set regardless of the RPV coupling value. In the gluino model with decays to first and second generation quarks, gluino masses are excluded up to 1.6-2.2 (1.6-2.5) TeV for different values of the RPV coupling $\lambda^{'}$ ($\lambda^{''}$). Top-squark masses up to 2.4 TeV are excluded at high values of $\lambda^{''}$, compared to 1.0-1.7 TeV for low and intermediate $\lambda^{''}$. Tau-slepton masses between 180 GeV and 340 GeV are excluded for $\lambda$ couplings smaller than $10^{-4}$. Higgsino masses up to 800 GeV-1.0 TeV are excluded when $\lambda_{i33}$ is larger than $4\times10^{-5}$. This work extends the analyses beyond RPC scenarios to a broad class of RPV frameworks and achieves significantly improved sensitivity to a diverse range of long-lived particle signatures.


[7] 2603.15322

A Simulation-Based Inference Evaluation of Tension Between MicroBooNE and MiniBooNE Results in a 3+1 Sterile Neutrino Global Fit

Compatibility between different datasets in a global fit is essential for determining whether a chosen model adequately describes the data. In a 3+1 sterile neutrino global fit, long-standing tensions between datasets sensitive to $\nu_e$ appearance and $\nu_e/\nu_\mu$ disappearance indicate a failure of the model to explain the observed data, despite an overall $> 5\sigma$ improvement over the $3\nu$ Standard Model (SM) based on a $\chi^2$ fit. Overall, a global preference for the 3+1 sterile-neutrino hypothesis with significant tension between experiments motivates consideration of more complex models, but these are currently computationally prohibitive to evaluate. This paper is the third in a series aimed at reducing computational cost by developing a Simulation-Based Inference (SBI) framework for global fits. Previous papers focused on rapidly fitting the data sets using frequentist (Feldman-Cousins) and Bayesian approaches, while in this work, we formalize a definition of tension within the SBI framework. As an example, we perform a full 3+1 fit to the charged-current quasi-elastic neutrino data from the MiniBooNE experiment and the inclusive neutrino data from the MicroBooNE experiment, located on the same beamline. Using experiment-supplied systematics as is, we find these data sets favor 3+1 at $3.6\sigma$ and $1.8\sigma$ respectively, while the tension between the two is $3.3\sigma$, when fit with the SBI procedure. After correcting for normalization differences between data and Monte Carlo in the MicroBooNE $\nu_\mu$ samples, the tension relaxes to $2.2\sigma$, indicating reduced but non-negligible disagreement. The observed tension may reflect both limitations of the 3+1 model in describing the datasets and the presence of systematic effects that impact the experiments differently.


[8] 2603.15493

LEP Data@EDM4hep: mitigating data loss risks by increasing data FAIRness, with a view on FCC-ee

The LEP data represents the most precise and highest centre-of-mass energy sample of $e^+e^-$ collision data collected to date. Numerous scientific articles have been published since the conclusion of the experiments, underscoring the ongoing relevance of this dataset and the need to secure its long-term availability according to FAIR data preservation principles. These data could also play a crucial new role in the context of the evaluation of the physics potential of FCC-ee, due to the overlapping centre-of-mass energies, offering a valuable benchmark for detector performance and physics analyses. To fulfill this role, the data should be made available in EDM4hep, the standardized event data format currently developed in the context of the common HEP software ecosystem Key4hep. Migrating to EDM4hep would not only beneficial to future studies but also significantly mitigate the risk of data loss, increase accessibility and interoperability, hence facilitate long-term data preservation. A proof of concept workflow to perform the migration has been developed and successfully applied to ALEPH data.


[9] 2603.15575

Search for the rare decays of $D\to h(h^{(')})e^{+}e^{-}$

We search for 15 rare decays of $D$ mesons to hadrons accompanied by an electron-positron pair $D\to h(h^{(')})e^{+}e^{-}$, based on 20.3 fb$^{-1}$ of $e^+ e^-$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector at BEPCII. No significant signals are observed, and the corresponding upper limits on the branching fractions at the 90\% confidence level are determined. The sensitivities of the results are at the level of $10^{-6}$ $\sim$ $10^{-7}$. The upper limits on the branching fractions for the $D^+\to \rho^{+} e^+ e^-$, $D^+\to K^{*+} e^+ e^-$, $D^0\to K_S^0 K_S^0 e^+ e^-$, $D^0\to \pi^0 \pi^0 e^+ e^-$ and $D^0\to \eta^{\prime} e^+ e^-$ decay channels are measured for the first time. For the $D^0\to \pi^0 e^+ e^-$, $D^0\to \eta e^+ e^-$, $D^0\to \omega e^+ e^-$, $D^0\to K_S^0 e^+ e^-$, $D^+\to \pi^+ \pi^0 e^+ e^-$, $D^+\to K^+ \pi^0 e^+ e^-$, $D^+\to \pi^+ K_S^0 e^+ e^-$ and $D^+\to K^+ K_S^0 e^+ e^-$ decay channels, the upper limits on the branching fractions are determined, with an improvement of at least a factor of four compared to previous searches. The upper limits on the branching fractions for the $D^0\to \rho^{0} e^+ e^-$ and $D^0\to \phi e^+ e^-$ decay channels are set at $0.7 \times 10^{-6}$ and $4.6 \times 10^{-6}$, respectively.


[10] 2603.13409

The ATLAS Trigger System

The ATLAS Trigger system is a key component of the ATLAS experiment at the CERN Large Hadron Collider (LHC), designed to reduce the event rate from the 40 MHz proton-proton bunch crossing frequency to an output suitable for offline storage and analysis. During Run-3 (2022-2026), major upgrades were implemented in both the hardware-based Level-1 (L1) Trigger and the software-based High Level Trigger (HLT), to cope with increased luminosity and pile-up conditions. This paper summarises the main features of the ATLAS Trigger system, its performance in Run-3, and its role in enabling precision measurements and new physics searches.


[11] 2603.13629

Projected Sensitivity of Paleo-Detectors to Dark Matter Effective Interactions with Nuclei

Paleo-detectors are a proposed experimental technique for direct detection (DD) of dark matter (DM) via the read-out of DM-induced nuclear recoil tracks in natural minerals. The large detector mass required for the sensitivity of conventional DD experiments to rare events is replaced by the exposure of paleo-detectors to DM-induced nuclear recoils over geological timescales. In this paper, we extend previous theoretical predictions for canonical spin-independent coherent and spin-dependent scattering (proportional to $A^2$ and the spin of the nucleus, respectively). We estimate the sensitivity of paleo-detectors to interactions between weakly interacting massive particle (WIMP) DM and nuclei within the framework of a Non-Relativistic Effective Field Theory (NREFT), considering isoscalar couplings to nucleons for both elastic and inelastic scattering. Taking into account cosmogenic, astrophysical and radiogenic backgrounds, we project the 90% confidence-level (CL) upper limits on the isoscalar NREFT coupling constants for both scattering types. We consider representative read-out scenarios and examine several target minerals. The projected sensitivities of paleo-detectors are compared with the 90% CL limits from the XENON100, LUX-ZEPLIN, and PandaX-II experiments, as well as with the 95% Bayesian credible region of the 2D marginalized posterior distribution from SuperCDMS. For DM masses from 1 GeV-10 GeV, paleo-detectors are projected to have sensitivity superior to that of conventional experiments for WIMP-nucleus interactions via all NREFT operators, largely independent of read-out scenario or target mineral. For DM masses from 10 GeV-5 TeV, we find that the sensitivity of paleo-detectors is projected to be comparable to or better than that of conventional experiments for WIMP-nucleus interactions via several NREFT operators, depending on the read-out scenario and target mineral.


[12] 2603.13970

Shapes are not enough: CONSERVAttack and its use for finding vulnerabilities and uncertainties in machine learning applications

In High Energy Physics, as in many other fields of science, the application of machine learning techniques has been crucial in advancing our understanding of fundamental phenomena. Increasingly, deep learning models are applied to analyze both simulated and experimental data. In most experiments, a rigorous regime of testing for physically motivated systematic uncertainties is in place. The numerical evaluation of these tests for differences between the data on the one side and simulations on the other side quantifies the effect of potential sources of mismodelling on the machine learning output. In addition, thorough comparisons of marginal distributions and (linear) feature correlations between data and simulation in "control regions" are applied. However, the guidance by physical motivation, and the need to constrain comparisons to specific regions, does not guarantee that all possible sources of deviations have been accounted for. We therefore propose a new adversarial attack - the CONSERVAttack - designed to exploit the remaining space of hypothetical deviations between simulation and data after the above mentioned tests. The resulting adversarial perturbations are consistent within the uncertainty bounds - evading standard validation checks - while successfully fooling the underlying model. We further propose strategies to mitigate such vulnerabilities and argue that robustness to adversarial effects must be considered when interpreting results from deep learning in particle physics.


[13] 2603.14295

Towards a Reflective PICOSEC detector?

PICOSEC is an ultrafast particle-detector concept, combining a photocathode-coated Cherenkov radiator coupled to a gas-avalanche multiplier. Particle-induced Cherenkov photons create photoelectrons emitted from an ultrathin semitransparent photocathode; they are multiplied and detected in fast gas-avalanche mode. In parallel to the constant progress made in the PICOSEC technique, we propose different detector configurations and operation modes with the aim of enhancing robustness and performance. They incorporate thick reflective photocathodes deposited on the readout electrodes of various types of avalanche multipliers. Some of these Reflective-PICOSEC detectors operate at mbar gas pressures.


[14] 2603.14368

Light double-gluon hybrid states

We investigate light hybrid mesons composed of a light quark-antiquark pair and two gluons within the framework of QCD sum rules. We focus on states with quantum numbers $J^{\mathrm{PC}} = 0^{++}, 0^{+-}, 0^{-+}, 0^{--}$ and $J^{\mathrm{PC}} = 1^{++}, 1^{+-}, 1^{-+}, 1^{--}$. By employing various interpolating currents constructed from valence light quarks and gluon fields, we determine the masses and current couplings of the $\bar{q}GGq$, $\bar{q}GGs$, and $\bar{s}GGs$ hybrid configurations. Nonperturbative effects are incorporated through quark and gluon condensates up to dimension twelve in the operator product expansion, improving the reliability of the numerical predictions. The results presented here may provide useful input for future experimental searches for light hybrid mesons and can also serve as a basis for studies of their decay properties and interactions with other hadronic states.


[15] 2603.14385

Jet peak shapes based on two-particle angular correlations in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

The longitudinal invariance of jet-induced peaks in two-particle correlation functions from relativistic lead-lead collisions is experimentally explored. The data were collected at a center-of-mass energy per nucleon pair of 5.02 TeV in 2018 using the CMS detector. The dataset corresponds to an integrated luminosity of 0.607 nb$^{-1}$. Long- and short-range correlations are studied through two-dimensional distributions of the separations in pseudorapidity and azimuth between particles in an event. Jets manifest as a well-defined peak at small angular separations, and the shape of this peak provides insight into jet medium interactions. This Letter examines the evolution of the jet peak shape, focusing on the dependence of its width and longitudinal asymmetry on the transverse momentum, collision centrality, and pseudorapidity of the associated charged particles. The jet-peak distributions of lower transverse momentum particles broaden in both pseudorapidity and azimuth with increasing collision overlap, with the broadening in pseudorapidity being more pronounced. The longitudinal asymmetry of the peaks is also found to increase as the average pseudorapidity increases. These results are compared to proton-proton collision data that were obtained at the same nucleon-nucleon collision center-of-mass energy with an integrated luminosity of 252 nb$^{-1}$.


[16] 2603.14553

An End-to-end Architecture for Collider Physics and Beyond

We present, to our knowledge, the first language-driven agent system capable of executing end-to-end collider phenomenology tasks, instantiated within a decoupled, domain-agnostic architecture for autonomous High-Energy Physics phenomenology. Guided only by natural-language prompts supplemented with standard physics notation, ColliderAgent carries out workflows from a theoretical Lagrangian to final phenomenological outputs without relying on package-specific code. In this framework, a hierarchical multi-agent reasoning layer is coupled to Magnus, a unified execution backend for phenomenological calculations and simulation toolchains. We validate the system on representative literature reproductions spanning leptoquark and axion-like-particle scenarios, higher-dimensional effective operators, parton-level and detector-level analyses, and large-scale parameter scans leading to exclusion limits. These results point to a route toward more automated, scalable, and reproducible research in collider physics, cosmology, and physics more broadly.


[17] 2603.14921

The Super Fine-Grained Detector for the T2K neutrino oscillation experiment

The magnetised near detector ND280 of the long-baseline neutrino experiment T2K has been upgraded to improve its detection performance and, consequently, enhance our understanding of neutrino-nucleus interactions, reducing the systematic uncertainties in measurements of the neutrino oscillation parameters. A key component of the upgrade is a novel segmented plastic scintillator detector, called the Super Fine-Grained Detector (SuperFGD), made of approximately 2 million optically isolated 1 cm$^3$ cubes read out by three orthogonal wavelength-shifting (WLS) fibres. Scintillation photons are detected by 55,888 Hamamatsu Multi-Pixel Photon Counters (MPPCs). The SuperFGD provides 3D images of neutrino interactions by tracking the final-state charged particles produced isotropically, including protons down to a threshold of around 330 MeV/$c$. The high light yield of SuperFGD greatly improves particle identification and the sub-nanosecond time resolution provides an excellent identification of Michel electrons. The SuperFGD is also able to detect neutrons from neutrino interactions and, for the first time in a neutrino experiment, to reconstruct their kinetic energy using a fine detector segmentation and by measuring the time-of-flight with sub-nanosecond precision. In this article the details of the detector design, construction and performance are described. The detector was installed in ND280 and successfully commissioned with cosmic data in 2023 and, later, with the T2K neutrino beam. The detector response has been characterised with the 2023 and 2024 data and the results are reported in this article.


[18] 2603.15029

$b \to c$ semileptonic sum rule: exploring a sterile neutrino loophole

We investigate the $b\to c$ semileptonic sum rule in the presence of a massive sterile neutrino. Recent measurements of charged-current semitauonic $B$-meson decays exhibit a $\sim4\sigma$ deviation from the Standard Model predictions, whereas no such tension has been reported for the lowest-lying baryonic counterpart, the $\Lambda_b$ decay. Since these decay rates are related through the sum rule, accommodating such a mismatch beyond the level of uncertainties is nontrivial. We revisit this issue by introducing new interactions involving a sterile neutrino. As the differential decay rates are modified by these new contributions, we evaluate the violation of the sum rule in the presence of a massive sterile neutrino. We find that the induced effect remains small compared with the current experimental uncertainties. Therefore, the sum rule provides a useful consistency check for the experimental data.


[19] 2603.15273

Design and operation of a spark chamber for vacuum ultraviolet light production

Noble liquids, notably argon and xenon, are utilised as both detector media and as the detector target for dark matter and neutrino physics experiments. When the noble liquid is excited by particles, it scintillates vacuum ultraviolet light, which sensors then detect. A major focus of the detector development community is on producing precision light sensors for noble liquid detectors. We introduce a flash lamp to test light sensors with light at wavelengths observed at noble liquid detectors. This paper discusses the design and presents results from a spark chamber prototype operated at room temperature.


[20] 2603.15524

Characterization of Passive CMOS Strip Detectors After Proton Irradiation

Strip detectors are populating outer trackers of high-energy particle experiments. They are convenient for covering large areas of sensitive material since they use less power and have fewer readout channels compared to pixels sensors. Nevertheless, they are typically manufactured with a mask set that covers the full wafer, otherwise when using smaller reticles the strip implants have to be stitched. For this project, strip detectors were fabricated in a CMOS commercial foundry using different reticles to be stitched several times, proving the feasibility of this technology. LFoundry produced the passive CMOS strip detector with a production line of 150 nm node technology, using a 150 um thick FZ wafer. Those strip sensors have three different geometries to study different impacts of the CMOS technology. The strips have lengths of 2.1 cm and 4.1 cm, stitching 3 or 5 reticles respectively. This work shows results of 24 GeV proton irradiated passive CMOS strip detectors. The detectors were irradiated at CERN and were tested with different set-ups, not showing any effect from the strips stitching. Proving that this technology is feasible for detecting high-energy particles opens the door to future large productions of passive strip detectors and also to produce active strip sensors in commercial CMOS foundries.


[21] 2508.03454

Search for Charmonium(-like) states decaying into the $Ω^-\barΩ^+$ final states

Recently, the BESIII experiment performed a measurement of the energy-dependent Born cross section and the effective form factor for the $e^+e^-\to\Omega^-\bar\Omega^+$ reaction at center-of-mass energies ranging from 3.4 to 4.7 GeV. A fit to the energy dependence of the dressed cross section is performed. With the assumption of a charmonium (like) resonance [i.e., $\psi(3770)$, $\psi(4040)$, $\psi(4160)$, $Y(4230)$, $Y(4360)$, $\psi(4415)$, or $Y(4660)$] plus a power-law function, the fit is applied to the data from the recent BESIII measurement, which was additionally combined with previous CLEO-c measurement data. No significance is found. The products of the branching fraction and the two electronic partial widths for the assumed charmonium(-like) states decaying into the $\Omega^-\bar\Omega^+$ final states are also provided. In addition, by taking the world average values of the electronic branching fraction, the branching fractions for $\psi(3770)$, $\psi(4040)$, $\psi(4160)$, $\psi(4415)$ decaying into $\Omega^-\bar\Omega^+$ final states at the 90\% confidence level are determined for the first time. These are found to be at least an order of magnitude larger than expected from predictions using a scaling based on the observed electronic widths.


[22] 2509.03608

Search for low-mass electron-recoil dark matter using a single-charge sensitive SuperCDMS-HVeV Detector

We present constraints on low-mass dark matter electron scattering and absorption interactions using a SuperCDMS high-voltage eV-resolution (HVeV) detector. Data were taken underground in the NEXUS facility located at Fermilab with an overburden of 225 meters of water equivalent. The experiment benefits from the minimizing of luminescence from the printed circuit boards in the detector holder used in all previous HVeV studies. A blind analysis of $6.1\,\mathrm{g\cdot days}$ of exposure produces exclusion limits for dark matter-electron scattering cross sections for masses as low as $1\,\mathrm{MeV}/c^2$, as well as on the photon-dark photon mixing parameter and the coupling constant between axionlike particles and electrons for particles with masses $>1.2\,\mathrm{eV}/c^2$ probed via absorption processes.


[23] 2509.26411

TrackFormers Part 2: Enhanced Transformer-Based Models for High-Energy Physics Track Reconstruction

High-Energy Physics experiments are rapidly escalating in generated data volume, a trend that will intensify with the upcoming High-Luminosity LHC upgrade. This surge in data necessitates critical revisions across the data processing pipeline, with particle track reconstruction being a prime candidate for improvement. In our previous work, we introduced "TrackFormers", a collection of Transformer-based one-shot encoder-only models that effectively associate hits with expected tracks. In this study, we extend our earlier efforts by conducting detailed investigations into more custom Transformer attention mechanisms, a new design combining geometric projection and lightweight clustering, and a joint model conditioning classification on a regressor's predictions. Furthermore, we discuss new datasets that allow the training on hit level for a range of physics processes. These developments collectively aim to boost both the accuracy and potentially the efficiency of our tracking models, offering a robust solution to meet the demands of next-generation high-energy physics experiments.


[24] 2512.24464

Thirty years after the discovery of the top quark: the field enters an age of refinement and subtlety

Thirty years after the first observation of on-shell top quarks the investigation of the heaviest elementary particle remains a thriving field of basic research, as was illustrated by the 18th edition of the annual Workshop on Top-Quark Physics hosted by Hanyang University in Seoul, Korea. Observing new scattering processses involving top quarks, precision measurements of top-quark properties, and the usage of top quarks as a means of exploration remain key elements of research, but are most recently complemented by the observation of even more subtle effects based on the application of refined experimental techniques. Based on the selection made in the experimental summary talk, this article highlights the most striking experimental results presented at the conference.


[25] 2603.13223

First measurement of time-dependent $CP$ violation in the flavor-changing neutral-current decay $B^{0}\rightarrow K_{S}^{0}μ^{+}μ^{-}$

A flavor-tagged time-dependent analysis of $B^{0}\rightarrow K_{S}^{0}\mu^{+}\mu^{-}$ decays is performed across the full dimuon mass range excluding the $J/\psi$ and $\psi(2S)$ resonance regions. The analysis uses proton-proton collision data collected by the LHCb experiment in 2011--2018 at center-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 9$fb^{-1}$. The CP violation parameters are determined to be $C=-0.13 \pm 0.32 \pm 0.04$ and $S= +0.82\pm 0.29 \pm 0.05$, where the first uncertainties are statistical and the second are this http URL results are consistent with the Standard Model prediction. This is the first experimental study of time-dependent CP violation in $b\rightarrow sl^{+}l^{-}$ processes.


[26] 2305.02881

Trainability barriers and opportunities in quantum generative modeling

Quantum generative models provide inherently efficient sampling strategies and thus show promise for achieving an advantage using quantum hardware. In this work, we investigate the barriers to the trainability of quantum generative models posed by barren plateaus and exponential loss concentration. We explore the interplay between explicit and implicit models and losses, and show that using quantum generative models with explicit losses such as the KL divergence leads to a new flavour of barren plateaus. In contrast, the implicit Maximum Mean Discrepancy loss can be viewed as the expectation value of an observable that is either low-bodied and provably trainable, or global and untrainable depending on the choice of kernel. In parallel, we find that solely low-bodied implicit losses cannot in general distinguish high-order correlations in the target data, while some quantum loss estimation strategies can. We validate our findings by comparing different loss functions for modelling data from High-Energy-Physics.


[27] 2411.01258

Beyond the EPICS: comprehensive Python IOC development with QueueIOC

Background and Purpose: Architectural deficiencies in EPICS lead to inefficiency in the development and application of EPICS IOCs. An unintrusive solution is replacing EPICS IOCs with more maintainable and flexible Python IOCs, only reusing the CA protocol of EPICS. While there are libraries like caproto and PCASPy that help to create Python IOCs, they still feel insufficient for more complex requirements. Methods: Noticing caput, caget and camonitor are just specialised combinations of requests/replies and notifications in client-server communication, by combining barebone caproto and event loops like those in server-like programs, the QueueIOC framework for Python IOCs is created, which has the potential to systematically reduce the development and maintenance cost of IOCs. Results: Examples based on QueueIOC are first given for workalikes of StreamDevice and asyn; also given are examples for "sequencer" applications, like those based on seq, include monochromators, motor anti-bumping and motor multiplexing. A QueueIOC-based framework for detector integration is presented in an accompanying paper. Also reported is a simple but expressive architecture for GUIs, as well as software to use with the ~/iocBoot convention which addresses some issues we find with a similar solution based on procServ.


[28] 2506.12889

Studying Maximal Entanglement and Bell Nonlocality at an Electron-Ion Collider

In this paper, we propose to test quantum entanglement and Bell nonlocality at an Electron-Ion Collider (EIC). By computing the spin correlations in quark-antiquark pairs produced via photon-gluon fusion, we find that longitudinally polarized photons produce maximal entanglement at leading order, while transversely polarized photons generate significant entanglement near the threshold and in the ultra-relativistic regime. Compared to hadron colliders, the EIC provides a cleaner experimental environment for measuring entanglement through the $\gamma^\ast g \to q\bar{q}$ channel, offering a strong signal and a promising avenue to verify Bell nonlocality. This study extends entanglement measurements to the EIC, presenting new opportunities to explore the interplay of quantum information phenomena and hadronic physics in the EIC era.


[29] 2507.07173

A Prototype Hybrid Mode Cavity for Heterodyne Axion Detection

In the heterodyne approach to axion detection, axion dark matter induces transitions between two modes of a microwave cavity, resulting in a parametrically enhanced signal power. We describe the fabrication and characterization of a prototype normal conducting cavity specifically optimized for heterodyne detection. Corrugations on the cavity walls support linearly polarized hybrid modes which maximize the signal power while strongly suppressing noise. We demonstrate tuning mechanisms which allow one mode's frequency to be scanned across a 4 MHz range, while suppressing cross-coupling noise by at least 80 dB. A future superconducting cavity with identical geometry to our prototype would have the potential to probe orders of magnitude beyond astrophysical bounds.


[30] 2509.04649

Tribute to Henry Primakoff: Chiral Perturbation Theory Tests via Primakoff Reactions

Consider high energy (GeV) beam particles scattering from the Coulomb field of a target nucleus (Z, A). The Coulomb field acts as a target of $\gamma^*$ virtual photons, with the target density proportional to Z$^2$. Henry Primakoff was the first to propose determining the lifetime of the $\pi^0$ meson by measuring the production cross section for the reaction $\gamma\gamma^* \rightarrow \pi^0$. This process occurs when a high-energy gamma-ray interacts with the Coulomb field. Quasi real exchanged photons ($\gamma^*$) are identified by isolating the sharp Coulomb peak at very low values of the squared four momentum transfer t to the target nucleus. The scattering cross section via one-photon exchange is proportional to the fine-structure constant $\alpha$ and inversely proportional to t$^2$. Since t is inversely related to the squared center-of-mass energy (s), it decreases rapidly as s increases. Consequently, despite the weakness of the electromagnetic interaction, the interaction amplitude can still be significant. We will first discuss Primakoff's scientific career and personal life. Next, we will review the Primakoff scattering experiments that measured the pion polarizability and the $\gamma\rightarrow\pi\pi\pi$ chiral anomaly amplitude at CERN COMPASS and the $\pi^0$ lifetime at Jefferson Laboratory (JLab). The data from these experiments are in good agreement with two-flavor (u, d) Chiral Perturbation Theory (ChPT) predictions. We explain that additional Primakoff measurements with kaons and $\eta$ mesons are needed to test how well three flavor (u, d, s) ChPT captures strange quark effects.


[31] 2509.05046

Tensor-polarized twist-3 parton distribution functions $f_{LT}(x)$ for the spin-1 deuteron by using twist-2 relations

Tensor-polarized twist-3 parton distribution functions (PDFs) $f_{LT}(x)$ are calculated for the spin-1 deuteron by using twist-2 relations, which are similar to the Wandzura-Wilczek relation and the Burkhardt-Cottingham sum rule in the spin-1/2 nucleon, together with tensor-polarized twist-2 PDFs $f_{1LL}(x)$. The PDFs are shown for $f_{LT}(x)$ at $Q^2 =2.5$ GeV$^2$, where the tensor-polarized PDFs $f_{1LL}(x)$ are provided. The $x$-dependence of $f_{LT}(x)$ is similar to $f_{1LL}(x)$, and the magnitude of $f_{LT}(x)$ is roughly of the order of $f_{1LL}(x)$. In experiments at the Thomas Jefferson National Accelerator Facility (JLab), higher-twist effects could be sizable because $Q^2$ values are not very large in comparison with the hadronic scale of 1 GeV$^2$. Therefore, the JLab experiments could provide a good opportunity to investigate the twist-3 distributions $f_{LT}(x)$ in addition to the twist-2 ones $f_{1LL}(x)$. Furthermore, these tensor-polarized PDFs could be investigated at future Electron-Ion Colliders (EICs) and hadron accelerator facilities such as the Fermi National Accelerator Laboratory (Fermilab), the Nuclotron-based Ion Collider fAcility (NICA), and the Large Hadron Collider (LHC).


[32] 2510.15913

Response of wavelength-shifting and scintillating-wavelength-shifting fibers to ionizing radiation

We report results of characterizing the response and light transport of wavelength-shifting (WLS) and scintillating-wavelength-shifting (Sci-WLS) fibers under irradiation by radioactive $\alpha$, $\beta$, and $\gamma$ sources. Light yield and light transmission were measured for the WLS fiber BCF-91A from Saint-Gobain and for a new Sci-WLS fiber EJ-160 from Eljen Technology. The two variants with different fluor mixtures, EJ-160I and EJ-160II, exhibited approximately five and seven times higher light yield than BCF-91A, respectively, while their attenuation lengths were 3.80\,m for BCF-91A, 4.00\,m for EJ-160I, and 2.50\,m for EJ-160II.


[33] 2512.22359

Orbital angular momentum in the pion and kaon: rest-frame and light-front

Orbital angular momentum (OAM) is not a Poincaré invariant quantity; so, its value is observer dependent. Notwithstanding that, in quantum chromodynamics, a Poincaré-invariant theory, OAM is part of every hadron wave function. Using continuum Schwinger function methods, we elucidate both the subjective character of in-hadron OAM and expose some of its impacts on pion and kaon structure and observables. For instance, working with light-front projections of their Bethe-Salpeter wave functions, it is found that the pion is a roughly 50/50 mix of light-front OAM zero and one components and the kaon is a 60/40 system. The overall picture is that (near) Nambu-Goldstone modes are complex bound states, each with significant intrinsic OAM, independent of the observer's reference frame. This feature must be accounted for in the calculation of observables. Inductively, the same is true for all hadrons.


[34] 2512.22837

Bell nonlocality and entanglement in $χ_{cJ}$ decays into baryon pair

We present a systematic analysis of Bell nonlocality and entanglement in $\chi_{cJ}$($J=0,1,2$) decays into baryon pair($B\bar{B}$), with particular emphasis on their production via the process $e^+e^- \to \psi(2S) \to \gamma \chi_{cJ}$ at BESIII. From the baryon-antibaryon spin density matrix, we construct measurable Bell observables and concurrence, revealing a striking hierarchy of quantum correlations: $\chi_{c0}$ decays exhibit maximal violation and entanglement; $\chi_{c1}$ decays violate Bell inequalities for $\theta_1 \in (0, \pi)$ with angle-modulated strength; we find that the $B\bar{B}$ pair in $\chi_{c2}$ decays is in a separable state, and no indication of Bell inequality violation is observed. We provide complete analytical results for $J=0,1$ and quantitative, uncertainty-aware estimations for $J=2$ based on experimental inputs from BESIII. These results establish the $\chi_{cJ}$ system produced via this radiative transition as a novel and promising platform for testing quantum entanglement and Bell nonlocality in high-energy collisions.


[35] 2601.16762

Thermodynamic geometry in hadron resonance gas model at real and imaginary baryon chemical potential and a simple sufficient condition for quark deconfinement

The thermodynamic geometry of the hadron resonance gas model with (without) excluded volume effects (EVE) of baryons is investigated. The case with imaginary mu, where mu is the baryon chemical potential, is investigated as well as the one with real mu. We calculate the scalar curvature R and use the R=0 criterion to investigate the phase structure in the mu^2-T plane where T is the temperature. The curve on which R=0 continues analytically from the imaginary mu region, where the lattice QCD is feasible, to the real mu one. In the presence of EVE, there are rich phase structures in the large real mu region as well as the Roberge-Weiss like region where mu is imaginary and a singularity appears, while there is no phase structure in the large real $\mu$ region in the absence of EVE. The limitation temperature of the baryon gas is also obtained by using the baryon number fluctuation. The LQCD predicted critical point locates almost on the curve of the limitation temperature we determined. A simple empiric sufficient condition, n_B>1/(2v_B)$, is obtained for the quark deconfinement in the large real mu region, where n_B and v_B are the net baryon number density and the volume of a baryon, respectively.


[36] 2603.03631

Flavor in Ninths and a Discrete Gauge Origin of the QCD Axion

Quark and lepton hierarchies are organized by rational powers of a single parameter in units of one ninth. We show that this ``flavor in ninths'' structure points to a discrete $\Z_{18}$ gauge origin of Froggatt--Nielsen symmetry, whose $\mathbb{Z}_9$ subgroup controls the flavor lattice. Identifying the flavon with the Peccei--Quinn field, the same symmetry stabilizes the QCD axion, enforces domain-wall number $N_{\rm DW}=1$, and predicts the axion--photon coupling through the anomaly ratio $E/N=8/3$ (or $2$ with light higgsinos). The lowest Planck-suppressed operator appears at dimension eighteen, naturally solving the axion quality problem. For $\f_a\sim(5$--$8)\times10^{11}$ GeV the axion accounts for dark matter and lies within near-term haloscope reach.