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Physics High Energy Physics (Experiment)

hep-ex Watch High Energy Physics (Experiment)

Thursday 27 August

High Energy Physics (Experiment) · Cross-listed from hep-ph

From the November Revolution toward the Millennium

Chris Quigg

The 4th International Symposium on the History of Particle Physics spanned two decades, from approximately 1980 to 2000. In this opening keynote lecture, I survey developments in particle physics from the prehistory of the $J/\psi$ discovery to the early nineteen-eighties. I offer context for the contributions that follow in the symposium program.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Exploring $Z/\gamma$-mediated heavy FCNCs at the FCC-ee

Abhik Sarkar, Subhajit Kala, Amir Subba et al. (+1 more)

The flavor structure of the Standard Model (SM) remains one of the most compelling questions in particle physics, with the third generation being particularly intriguing due to its significantly larger masses and comparatively less precisely measured properties. These features make third-generation flavor transitions particularly interesting in context of search for physics beyond the SM. In this work, we investigate flavor-violating transitions between the third and the first two generations, mediated by the neutral gauge bosons ($Z/\gamma$), within the framework of the SM Effective Field Theory (SMEFT), using dipole and Higgs-current operators. We determine the optimal sensitivities using the optimal observable technique (OOT) at different center-of-mass energies of the upcoming Future Circular Collider in the $e^+e^-$ mode (FCC-ee). We further derive complementary constraints on the relevant SMEFT operators from low-energy flavor-violating observables and heavy fermion decay channels. Our analysis also reveals characteristic interference patterns among the dipole contributions, which depend on the underlying flavor transition and exhibit distinct behavior between the $Z$ pole and higher-energy FCC-ee stages. The FCC-ee provides a complementary and direct probe of flavor-violating interactions at the electroweak scale, with the projections showing improved sensitivity for several interactions and comparable sensitivity to existing flavor constraints for several others. This highlights the importance of a systematic assessment across the different FCC-ee energy stages, which provides a comprehensive picture of its potential to explore flavor-violating phenomena and its complementarity with low-energy flavor experiments.
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All authors Abhik Sarkar, Subhajit Kala, Amir Subba, Yu Shi

High Energy Physics (Experiment)

Search for high-mass resonances in photon-jet final states using 140 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

ATLAS Collaboration

A search for new high-mass phenomena in events with a high-transverse-momentum photon and a jet is performed using data collected by the ATLAS experiment from proton-proton collisions at the LHC, with a centre-of-mass energy of 13 TeV. The analysis is based on a total integrated luminosity of 140 fb$^{-1}$. The $\gamma$$-$jet invariant mass spectrum measured in data is examined for localised excesses above the Standard Model background. No significant deviation from the Standard Model prediction is observed, allowing stringent limits to be set on the production cross sections of specific new physics scenarios. To investigate quark compositeness, excited quark models are studied for different couplings ($f$) and flavours: light $q_{\mathrm{L}}^{*}$ $(u^{*}/d^{*})$ and heavy ($b^{*}$, $c^{*}$). For $f=1$, masses up to 6.0 TeV ($q_{\mathrm{L}}^{*}$), 3.5 TeV ($c^{*}$), and 2.6 TeV ($b^{*}$) are excluded. These results provide the first direct constraints on $c^{*}$ production in the $\gamma$$-$ jet final state at the LHC. Additionally, the analysis excludes quantum black hole mass thresholds up to 5.3 (7.5) TeV in the Randall-Sundrum (Arkani-Hamed-Dimopoulos-Dvali) models at a 95% confidence level, further constraining these theoretical frameworks. Constraints on the visible cross-section are also obtained using generic Gaussian-shaped resonance production.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Simulations and flavour-scheme studies for Higgs-boson production in association with charm quarks

Tiziano Bevilacqua, Christian Biello, Lea Michela Caminada et al. (+5 more)

We present a detailed NLO+PS study of Higgs-boson production in association with charm and bottom quarks, with particular focus on the modelling of the H+c final state. We systematically compare predictions in massive and massless flavour schemes, quantify scale and flavour-scheme uncertainties, and assess the impact of interference and loop-induced contributions. Special emphasis is placed on the Higgs production via charm Yukawa fusion, for which we compare NLO+PS predictions with a NNLO+PS calculation of $c\bar{c}H$ production in the four-flavour scheme at 13.6 TeV. Based on these results, we provide the first practical recommendations for the simulation of $c\bar{c}H$ production in LHC analyses.
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All authors Tiziano Bevilacqua, Christian Biello, Lea Michela Caminada, Clemens Lange, Marino Missiroli, Davide Pagani, Michele Selvaggi, Marco Zaro

High Energy Physics (Experiment) · Cross-listed from hep-ph

$\mu$DM: a new mechanism for the baryon-dark matter coincidence

Wen Yin

For a relativistically decoupled thermal relic, the dark-matter energy-to-entropy ratio scales as $\rho_{\rm DM}/s\sim 10^{-3}m_{\rm DM}$. This is the familiar hot-dark-matter abundance relation. Immediately after weak-sphaleron freeze-out, the baryon asymmetry can be parametrized as $\rho_{\rm baryon}/s\sim 10^{-4}|\mu_B|$. Here $\mu_B$ is the baryon-number chemical potential. We propose a new class of models, called chemical-potential-matched dark matter ($\mu$DM), in which $|\mu_B|\sim m_{\rm DM}$, thereby providing a new route to the baryon-dark matter coincidence. As a concrete example of $\mu$DM, we consider an Affleck-Dine field whose excitations constitute dark matter. We also briefly discuss spontaneous electroweak baryogenesis associated with axion-like-particle walls. In the absence of entropy dilution, this coincidence mechanism generically points to dark matter in the eV-keV mass range. Its momentum distribution can nevertheless be cold if thermal production is dominated by Bose-enhanced stimulated emission. Alternatively, entropy dilution after both the dark-matter and baryon yields are fixed allows masses up to the MeV scale.
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Wednesday 26 August

High Energy Physics (Experiment) · Cross-listed from hep-ph

Direct and Indirect searches for DM-electron interactions in sub-GeV DM models

Marco Cirelli, Arpan Kar, Antoine Letessier-Selvon et al. (+1 more)

We analyze the complementarity between direct detection (DD) and indirect detection (ID) searches of sub-GeV dark matter (DM) in the context of two realistic models: the vector-portal (dark photon) and scalar-portal (higgs-portal) models. For DD we focus on the latest constraints on the DM-electron scattering from the present DAMIC-M experiment as well as its future projection. For ID we consider several existing X-rays/gamma-rays and cosmic-ray ($e^\pm$) observations as well as the upcoming MeV telescope COSI to obtain the corresponding bounds and projections on the DM annihilation rate, which are then translated in terms of the DM-electron scattering cross-section and compared with the DD bounds/projections. We properly take into account astrophysical and galactic propagation uncertainties. We find that the complementarity between DAMIC-M and ID works best for the vector-portal model, especially for the case where the vector mediator is heavier than the DM particle: in this case, the present DAMIC-M bound becomes comparable to (or better than, for some astrophysical configurations) the combined ID limit for $3\,{\rm MeV} \lesssim m_{\rm DM} \lesssim 20\,{\rm MeV}$. For other cases and mass ranges, the ID is in general more constraining and can also, for some mass ranges, constrain the parameter space below the neutrino floor, which is inaccessible to DD experiments.
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All authors Marco Cirelli, Arpan Kar, Antoine Letessier-Selvon, Harrys Lumengo-Kidimbu

High Energy Physics (Experiment) · Cross-listed from quant-ph

The Role of Geometric Analysis in Interferometer Design and Optimization for Gravitational Quantum Entanglement

Alireza Maleki

The pursuit of a quantum theory of gravity, aiming to unify general relativity and quantum mechanics, remains one of the most enduring challenges in physics. Because of the extreme energy scales associated with the Planck regime, direct experimental evidence for quantum gravity remains elusive. However, recent proposals suggest that quantum entanglement between two massive particles may provide a pathway to probe the quantum nature of gravity. In this study, we examine the interferometer geometries proposed in these works, with particular attention to the commonly used approximation that neglects phase contributions from the vertical segments of the particle trajectories. Our analysis shows that this approximation can lead to incorrect predictions and, in certain parameter regimes, to null results where entanglement would otherwise be expected. We derive exact solutions that incorporate the full particle trajectories and demonstrate that the vertical arms can significantly affect the accumulated phase. Crucially, we identify configurations in which the induced entanglement vanishes entirely, a feature missed by simplified treatments. These findings show that accounting for the full interferometer geometry is not merely a refinement, but is essential for accurately assessing gravity-induced entanglement.
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High Energy Physics (Experiment)

Efficient binned profile likelihood minimization for precision measurements with RABBIT

David Walter, Josh Bendavid and Kenneth Long

Precision measurements at the LHC increasingly rely on binned profile maximum likelihood fits with thousands of bins and nuisance parameters, and the High-Luminosity LHC will push these numbers further. Fast and robust minimization of such likelihoods is crucial for timely analysis development and accurate inference. We present Rabbit (Rapid Automatic Bin-Based Inference Tool), a Python framework that exploits differentiable programming in TensorFlow 2 to perform this task on CPUs and GPUs. Automatic differentiation provides exact gradients and Hessian-vector products for a trust-region minimizer operating in Krylov subspaces, and just-intime compilation yields near-C++ execution speed. Rabbit implements flexible statistical models with analytic treatments where possible, supports symmetrization options that establish Gaussian approximations and a linearized likelihood formulation with deterministic solutions, and focuses on measuring physical observables through differentiable transformations of the model, including unfolded differential cross sections. Benchmarks on synthetic models demonstrate excellent scaling with the number of bins and parameters, outperforming established tools in challenging regimes where these fail to converge within reasonable time.
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High Energy Physics (Experiment) · Cross-listed from astro-ph.CO

Paleo-Detectors as a Novel Probe of Dark Matter-Nucleus Effective Interactions

Dionysios P. Theodosopoulos

Paleo-detectors are a proposed approach to the direct detection of dark matter (DM) based on the observation of DM-induced nuclear recoils. Rather than relying on large detector masses required for conventional detectors, paleo-detectors exploit extremely long integration times, using small samples of naturally occurring minerals that have resided deep underground and accumulated damage tracks over geological timescales of order a gigayear. In this contribution, we review recent theoretical predictions for the sensitivity of paleo-detectors to WIMP-nucleus interactions within the framework of a Non-Relativistic Effective Field Theory (NREFT). We discuss both elastic and inelastic scattering processes and consider isoscalar couplings, taking into account backgrounds from neutrinos and radiogenic sources. We present projected sensitivities of paleo-detectors for different readout and exposure scenarios and compare the reach of paleo-detectors to that of conventional direct-detection experiments. For DM masses in the range $1\ \mathrm{GeV}/c^2$-$10\ \mathrm{GeV}/c^2$, paleo-detectors are expected to achieve sensitivities exceeding those of conventional experiments for WIMP-nucleus interactions mediated by all NREFT operators, with only a weak dependence on the read-out scenario or target mineral. For larger DM masses, $10\ \mathrm{GeV}/c^2$-$5\ \mathrm{TeV}/c^2$, paleo-detectors are projected to attain sensitivities comparable to or surpassing conventional experiments for interactions mediated by several NREFT operators, depending on the specific read-out scenario and choice of target mineral.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

First-Principles Nuclear Modeling for Light Dark Matter Experiments at the Intensity Frontier

Taylor R. Gray and Alberto Scalesi

Accelerator-based experiments at the intensity frontier, in which a high-energy beam impinges on a nuclear target, serve as powerful probes of the light dark matter paradigm. Such experiments require precise modeling of the target nucleus for reliable signal predictions. We present the application of a many-body ab initio method to calculate light dark matter mediator production signal rates at electron fixed-target experiments, using chiral effective field theory interactions. Considering both elastic and quasi elastic scattering, we compute cross sections using a Monte Carlo event generator implementation informed by ab initio nuclear elastic form factors and spectral functions for three representative nuclei, $^{20}$Ne, $^{34}$Si, and $^{56}$Fe, at varying electron beam energies. We compare our results to a commonly used phenomenological parameterization, finding an increased signal yield by up to two orders of magnitude with our quasi elastic treatment and an agreement for lighter mediators.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Classical and Hybrid Quantum Machine Learning for Trigger-Like Event Selection on CMS Open Data: An Eight-Qubit, PCA-Constrained Benchmark

Tariq Mahmood, Muhammad Awais Rafique, Talab Hussain et al. (+3 more)

Event triggering sits at the heart of high-energy physics, where the rare events of interest must be retained while an overwhelming background is discarded under tight latency and bandwidth budgets. This work compares four classical machine learning models, namely a support vector machine, an artificial neural network, a convolutional network and a long short-term memory network, with four hybrid quantum counterparts, on a trigger-like binary classification task built from CMS open data. The label is defined by an invariant-mass window, and the inputs combine reconstructed kinematics with physics-motivated derived variables: the pseudorapidity difference, the wrapped azimuthal difference, the angular separation and the total transverse momentum. The quantum models run under a fixed resource budget of eight qubits, a principal-component compression to sixteen features and state-vector simulation. Every model shares the same stratified split, the same preprocessing and a common decision threshold, and performance is reported through accuracy, ROC-AUC, F1-score, precision and recall. The strongest classical model is the artificial neural network, at 93.53 percent accuracy and 0.9819 ROC-AUC, while the strongest quantum model is the quantum convolutional network, at 90.89 percent accuracy and 0.9731 ROC-AUC, with the quantum neural network close behind. The quantum-kernel and recurrent quantum approaches trail both, which places the trainable hybrid embeddings ahead within this budget. The study is meant as a controlled reference point rather than a claim of quantum advantage.
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All authors Tariq Mahmood, Muhammad Awais Rafique, Talab Hussain, Juan Pablo Perez Aguilar, Alfredo Raya, Muhammad Ahsan

High Energy Physics (Experiment) · Cross-listed from astro-ph.HE

Finding and using interpretable latents in a neutrino foundation model with sparse autoencoders

Raphaël Bonnet-Guerrini, Johann Ioannou-Nikolaides, Inar Timiryasov et al. (+1 more)

We present a first application of sparse-autoencoder-based mechanistic interpretability to particle physics. Studying a neutrino foundation model pretrained on IceCube data and fine-tuned for direction reconstruction, we identify a validated atlas of physical concepts in the model representation, using a strict validation protocol consisting of held-out tests, matched nuisance controls, and replication across independent dictionary trainings. Causal interventions show that the direction head barely draws on this atlas. Motivated by this underused information, we train an uncertainty head on the same event-level representation to predict the model's angular reconstruction error. Unlike the direction head, it depends causally on quality and brightness features from the atlas. At $20\%$ selection efficiency, this interpretable estimator improves the median angular resolution from $20.2^\circ$ to $3.2^\circ$. These results suggest that mechanistic interpretability can reveal learned latent physics encoded within a model's internal representation and help design downstream tasks that exploit it.
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All authors Raphaël Bonnet-Guerrini, Johann Ioannou-Nikolaides, Inar Timiryasov, Vincenzo Piuri

High Energy Physics (Experiment)

A Weighting Method for Incorporating Mass Resolution Effects in Amplitude Analysis

Benhou Xiang, Wenqian Zheng, Hongxun Yang et al. (+2 more)

We present a phase-space weighting method for incorporating detector mass-resolution effects into amplitude analysis in an efficient and flexible way. The method uses fully simulated Monte Carlo samples containing both truth-level and reconstructed kinematics to estimate the local detector response around each observed event. Based on these truth-reconstruction correspondences, event-by-event weights are constructed to map theoretical amplitudes from the true phase space to the smeared observational space. In this way, detector smearing can be included in the likelihood fit without performing an explicit multidimensional convolution or on-the-fly detector simulation. The procedure naturally handles nonuniform resolution across the Dalitz plane and can be extended beyond invariant masses to momentum and angular variables. Applied to the decays $J/\psi \rightarrow \Xi^{-} \bar{\Xi}^{+}\pi^0$ and $J/\psi\rightarrow K^-\Lambda\bar{\Xi}^+$, the method significantly reduces biases in fitted resonance parameters and interference patterns, suppresses artificial structures, and improves the reliability of partial-wave analysis and resonance spectroscopy in high-precision hadron experiments.
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All authors Benhou Xiang, Wenqian Zheng, Hongxun Yang, Xiaolin Kang, Shuangshi Fang

High Energy Physics (Experiment)

A High Performance Partial Wave Analysis Framework for Hadron Spectroscopy

Benhou Xiang, Shuangshi Fang and Beijiang Liu

Partial wave analysis (PWA) is a key method in hadron physics for extracting the properties of hadronic resonances. As experimental statistics grow, conventional implementations face severe difficulties in both memory usage and speed. We present CTPWA, a high performance PWA framework based on covariant tensor formalism. This framework adopts extensive precomputation and caching mechanisms, as well as fully GPU-based likelihood computation and minimization. With these optimization, the fitting speed is accelerated by two orders of magnitude relative to autograd-based GPU PWA programs, rendering high-statistics partial-wave analysis feasible at high-precision experiments like BESIII.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Mixing effects in radiative decays of heavy-strange axial-vector mesons within light-cone QCD sum rules

T. M. Aliev, S. Bilmis and M. Savci

We calculate the radiative decay widths of $D_{s1}(2460)\to D_s\gamma$, $D_{s1}(2536)\to D_s\gamma$, $B_{s1}(5750)\to B_s\gamma$, and $B_{s1}(5830)\to B_s\gamma$ within light-cone QCD sum rules, taking into account the mixing between the $^{1}P_{1}$ and $^{3}P_{1}$ configurations. In the bottom-strange sector, we consider the experimentally established $B_{s1}(5830)$ together with the theoretically expected lower $1^+$ state, denoted $B_{s1}(5750)$. We obtain $\Gamma[D_{s1}(2460)\to D_s\gamma]=45.9^{+10.1}_{-8.5}$ keV, $\Gamma[D_{s1}(2536)\to D_s\gamma]=0.55^{+1.73}_{-0.48}$ keV, $\Gamma[B_{s1}(5750)\to B_s\gamma]=12.0^{+2.9}_{-2.3}$ keV, and $\Gamma[B_{s1}(5830)\to B_s\gamma]=8.9^{+2.4}_{-2.0}$ keV. The $D_{s1}(2460)\to D_s\gamma$ decay width is substantially larger than that of $D_{s1}(2536)\to D_s\gamma$. This difference originates from $^{1}P_{1}$-$^{3}P_{1}$ mixing: the two basis-current contributions interfere constructively for the lower state and destructively for the higher state. In the bottom-strange sector, the two widths are comparable within their uncertainties, although the higher state still exhibits destructive interference. These results show that the radiative decay pattern of strange heavy axial-vector mesons is sensitive to the mixing of the two spin configurations.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Low-$x$ parton densities accounting for absorptive effects and exclusive $J/\psi$ and $\Upsilon$ data from the LHC

V. Bertone, C. A. Flett, A. D. Martin et al. (+1 more)

Based on the combined Deep-Inelastic Scattering (DIS) data from HERA and the exclusive $J/\psi$ and $\Upsilon$ cross sections measured at the LHC, we investigate the role of absorptive corrections on the low-$x$ behaviour of parton distribution functions (PDFs) at low and moderate scales. Using $\texttt{xFitter}$, we study the impact of these data and of non-linear evolution on PDFs at next-to-leading order (NLO) and through the NNLO$^*$ method introduced in a previous work. Finally, we determine the effective size of proton hot spots within this framework and discuss the implications of our results for future global PDF determinations.
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All authors V. Bertone, C. A. Flett, A. D. Martin, M. G. Ryskin

High Energy Physics (Experiment) · Cross-listed from hep-ph

Odderon in the diffractive dip region

E.G.S. Luna, M.G. Ryskin and V.A. Khoze

We examine possible $C$-odd effects in elastic proton-proton and proton-antiproton scattering in the diffractive dip region. Collider data with $\sqrt{s}>500$ GeV are fitted for $0.2<|t|<1~\GeV^2$, using a simple Regge-inspired parametrization of effective $C$-even and $C$-odd amplitudes. The relative phases are not left free, but are fixed by the signature factors of the corresponding even and odd contributions. In this way, the real and imaginary parts of each term are linked by crossing. The $C$-even amplitude is first described by three effective Pomeron-like terms. The $C$-odd sector is then tested with several one-term Odderon-like forms. We find that the fits do not require a stable nonzero $C$-odd term: the odd contribution is either compatible with zero or becomes weakly constrained when we allow extra freedom. We then test whether the conclusion is changed by adding either a fourth Pomeron-like term or a second Odderon-like term. The improvement obtained with the fourth Pomeron-like term is mainly $C$-even, while the second Odderon-like term is not resolved as an independent contribution. These results provide a complementary test of recent determinations of the Odderon amplitude based on scaling and analyticity.
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High Energy Physics (Experiment) · Cross-listed from physics.ins-det

Development and Commissioning of the Cryogenic Target Detectors for the Technical Run of the NUCLEUS Experiment

N. Schermer, H. Abele, G. Angloher et al. (+57 more)

The NUCLEUS experiment aims to study coherent elastic neutrino-nucleus scattering (CE$\nu$NS) of reactor electron antineutrinos at the Chooz nuclear power plant in France. In this work, the cryogenic target-detector module for the NUCLEUS Technical Run was developed and commissioned at the Technical University of Munich. The module comprises four gram-scale CaWO$_4$ detectors, each equipped with two Transition Edge Sensors (TES), providing a total target mass of 6.96 g. We present the design, integration, detector characterization, and X-ray-based energy calibration of these detectors. Across six characterized detectors, a mean baseline resolution of $\overline{\sigma}_{\mathrm{BL}} = (2.79 \pm 0.60)\,\mathrm{eV}$ was achieved. The best-performing detector reached $\sigma_{\mathrm{BL}} = (2.16 \pm 0.02_{\mathrm{stat}})\,\mathrm{eV}$, surpassing the design goal by a factor of two and representing a state-of-the-art result for a cryogenic CaWO$_4$ detector. The target detector module was successfully operated simultaneously with the surrounding Cryogenic Outer Veto, which consists of six kg-scale Ge detectors for background discrimination, showing no measurable cross-talk. These results demonstrate the readiness of the target-detector system for the NUCLEUS Technical Run at Chooz and mark a key milestone in the development of cryogenic detectors for reactor-CE$\nu$NS measurements.
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All authors N. Schermer, H. Abele, G. Angloher, B. Arnold, M. Atzori Corona, A. Bento, E. Bossio, F. Buchsteiner, J. Burkhart, F. Cappella, M. Cappelli, N. Casali, R. Cerulli, A. Cruciani, G. Del Castello, S. Dorer, A. Erhart, M. Friedl, S. Fichtinger, V.M. Ghete, M. Giammei, J. Hakenmüller, D. Hauff, M. Hock, F. Jeanneau, E. Jericha, M. Kaznacheeva, H. Kluck, A. Langenkämper, T. Lasserre, D. Lhuillier, M. Mancuso, B. Mauri, A. Mazzolari, L. McCallin, H. Neyrial, C. Nones, L. Oberauer, L. Peters, F. Petricca, W. Potzel, F. Pröbst, F. Reindl, M. Romagnoni, J. Rothe, J. Schieck, S. Schönert, C. Schwertner, L. Scola, L. Stodolsky, A. Schröder, R. Strauss, R. Thalmeier, C. Tomei, L. Valla, M. Vignati, M. Vivier, A. Wallach, P. Wasser, L. Wienke

High Energy Physics (Experiment)

Measurement of $tZq$ inclusive and differential cross-sections in $pp$ collisions at $\sqrt{s} = 13~\text{TeV}$ with the ATLAS detector

ATLAS Collaboration

The $t$-channel production of a top quark in association with a $Z$ boson, $tZq$, is measured in the trilepton channel. The measured $pp \rightarrow t\ell^+\ell^-q$ process is defined for $m_{\ell\ell} > 30\,\text{GeV}$ and includes both resonant $Z$-boson production and non-resonant dilepton production. The data collected by the ATLAS experiment in 2015 to 2018 in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13\,\text{TeV}$ are used, corresponding to an integrated luminosity of $140\,\text{fb}^{-1}$. Events containing three light leptons ($e$ or $\mu$) and two to four jets, one or two of which are identified as $b$-quark-initiated jets, are selected. The inclusive $pp \rightarrow t \ell\ell q$ cross-section with $m_{\ell\ell} > 30\,\text{GeV}$ is measured, along with the separate cross-sections for top-quark and top-antiquark production and their ratio. The inclusive cross-section is measured to be $95.2\;^{+8.5}_{-7.9}\;\text{(stat.)}\;^{+5.5}_{-5.3}\;\text{(syst.)}\,\text{fb}$ and found to be in agreement with the most advanced Standard Model predictions. Differential cross-section measurements as a function of many kinematic variables are also presented. Both absolute and normalised differential cross-section measurements are made at particle level and parton level in their respective phase spaces. The top-quark spin asymmetry is measured from the unfolded measurement of the top-quark polarisation angle as $A = 0.34 \pm 0.14 \;\text{(stat.)} \pm 0.06\;\text{(syst.)}$, in good agreement with the Standard Model prediction. The differential cross-section measurement results are interpreted in the framework of Standard Model effective field theory and limits are set on dimension-6 operators involving the top quark.
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High Energy Physics (Experiment) · Cross-listed from physics.acc-ph

Feasibility demonstration of a high-momentum, high-purity muon beamline at the J-PARC Hadron Experimental Facility

Kotaro Shirotori, Takaya Akaishi, Kazuya Aoki et al. (+16 more)

We have established and characterized a novel high-purity muon beam delivery scheme, designated as $\mu$20, at the high-momentum hadron beamline (B-line) of the J-PARC Hadron Experimental Facility. This scheme delivers tertiary muons produced via the in-flight backward decays of secondary pions in the straight section of the beamline, inherently suppressing parent hadron contamination. In a systematic performance evaluation, the muon beam achieved a standalone intensity of $1.7\times10{^3}$ particles/spill with a spatial spread (standard deviation, $\sigma$) of approximately 15 mm at the downstream detector position. A systematic attenuation analysis utilizing an iron absorber verified a high muon purity of 98.0$\pm$0.6% for the 3 GeV/$c$ muon beam mode. Crucially, this work marks the first successful feasibility study of a high-momentum and high-purity muon beamline operation at an experimental facility in Japan.
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All authors Kotaro Shirotori, Takaya Akaishi, Kazuya Aoki, Wen-Chen Chang, Ryotaro Honda, Yusuke Hori, Takatsugu Ishikawa, Nobuyuki Kobayashi, Ruri Kurasaki, Che-Sheng Lin, Yuhei Morino, Megumi Naruki, Hiroyuki Noumi, Kyoichiro Ozawa, Shinya Sawada, Ken Suzuki, Hitoshi Takahashi, Taiga Toda, Natsuki Tomida

High Energy Physics (Experiment)

Operation of Unshielded Kinetic-Inductance Traveling-Wave Parametric Amplifiers in Multi-Tesla Fields

Christian Boutan, Erik Lentz, Corwin Shiu et al. (+12 more)

Cryogenic parametric amplifiers are used to amplify radio-frequency signals for a range of applications in basic and applied science. Both Josephson Parametric Amplifiers and Josephson Traveling-Wave Parametric Amplifiers have been used as first-stage amplifiers enabling readout chains operating within a few quanta of the quantum limit. However, these devices are highly sensitive to magnetic fields, having critical current suppressed by the Fraunhofer effect, requiring substantial field-free zones. In a dark matter axion search experiment, axions convert to detectable microwave photons in the presence of a strong magnetic field, necessitating amplifiers that can reliably operate close to these environments. Kinetic-inductance Traveling-Wave Parametric Amplifiers (KTWPAs) may be the ideal candidate for this type of application having high critical magnetic field of the materials used throughout their construction. In this letter we demonstrate that KTWPAs can provide high gain (>20dB) over a multi-GHz bandwidth in spite of from multiple exposures to multi-Tesla fields. Further, we explore operational characteristics of these devices under harsh conditions as a function of overall field strength, device orientation within the field, applied bias current, and pump power & frequency. In so doing, we find KTWPA gain vanishes in devices oriented perpendicularly to a field of 0.02T, but gain values >10dB are achievable in fields over 1T when oriented near~parallel to the device plane, with peak gain achieved with an applied 0.25T to 0.5T field. It is our expectation that KTWPAs will expand the accessibility of quantum-limited RF measurements in the presence of Tesla-scale fields.
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All authors Christian Boutan, Erik Lentz, Corwin Shiu, Deniz Erdag, Stephen Jones, Joseph Van Vlack, Logan Howe, Andrea Giachero, Paul Szypryt, Michael Vissers, Jason Austermann, Johannes Hubmayr, Stefan Knirck, Douglas Bennett, Joel Ullom

High Energy Physics (Experiment) · Cross-listed from physics.optics

Nanophotonic control of spatial information in scintillation detectors

Joshua Chen, Simo Pajovic, Seou Choi et al. (+9 more)

X-rays enable non-invasive imaging across medicine, security, materials science, and beyond, yet modern systems remain constrained by the need to resolve finer structures at lower radiation dose. Scintillators are the dominant materials for detecting X-rays, but face a longstanding compromise: thick scintillators absorb X-rays effectively, whereas optical photons generated throughout their volume spread before detection, degrading spatial information. Existing scintillator architectures largely try to preserve resolution by physically confining light using pixels, columnar crystals, or microstructured channels. Here, we show that high-resolution detection does not require the volumetric confinement of scintillation light. A metalens integrated directly with a bulk scintillator uses nanophotonic wavefront control to preferentially transfer high-spatial-frequency information from volumetrically generated scintillation light to the detector, while retaining the X-ray absorption of a thick scintillator. We experimentally recover fine spatial detail in X-ray images of inorganic and biological specimens. In a detector geometry relevant to computed tomography (CT), the experimentally validated model predicts a fivefold reduction in required X-ray dose and a 25-fold increase in resolution bandwidth relative to a state-of-the-art pixelated scintillator. These results establish wavefront engineering as a route to separating efficient X-ray absorption from optical image formation, with the potential for substantially higher-resolution, lower-dose CT.
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All authors Joshua Chen, Simo Pajovic, Seou Choi, Sachin Vaidya, William Michaels, Louis Martin-Monier, Christina M. Spägele, Steven E. Kooi, Juejun Hu, Rajiv Gupta, Charles Roques-Carmes, Marin Soljačić

Tuesday 25 August

High Energy Physics (Experiment) · Cross-listed from quant-ph

Femtoscopic Correlation Functions in Density Operator Representation

Hao-Nan Liu, Duo-Lun Ge, Zhi-Wei Liu et al. (+2 more)

Femtoscopic correlation functions (CFs) have been increasingly used to extract strong interactions between pairs of unstable particles, but their physical soundness has recently been questioned. To answer this, we formulate CFs at the operator level, with the observed subsystem described by a reduced density operator and subsequent dynamics absorbed into an effective measurement operator. The Koonin-Pratt form is recovered under four well-motivated reductions. The formulation makes explicit that the source-side and interaction-side representations must be consistently matched, and motivates an operational convention in which a measured reference correlation establishes a compatible source–interaction pairing that can be extended to other pairs for CF-to-CF predictions.
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All authors Hao-Nan Liu, Duo-Lun Ge, Zhi-Wei Liu, Jun-Xu Lu, Li-Sheng Geng

High Energy Physics (Experiment)

ADoNIS: A Differentiable generatOr of Neutrino Interaction Samples

César Jesús-Valls

Neutrino interaction generators are central to precision oscillation analyses, but conventional implementations do not directly provide derivatives of their predictions with respect to physics parameters, leaving analyses to obtain this dependence through reweighting, finite differences or external response models. We present ADoNIS, a fully differentiable neutrino interaction event generator that makes event reweighting and its gradients directly available, propagating exact derivatives through the nuclear ground state, hard-scattering amplitudes and stochastic intranuclear cascade. Following the physics choices of ACHILLES, we demonstrate agreement with its predictions across neutrino, electron and hadron probes, showing that differentiability is achieved without loss of physical fidelity. We then show how the resulting Jacobian exposes which measurements and regions of phase space constrain each parameter and how different probes break degeneracies, providing a quantitative tool for fit design, model tuning, measurement design and experiment design. The same differentiable predictions can be used directly in frequentist and Bayesian inference and carried through detector response to reconstructed observables for unfolding, while also yielding computational gains. In sum, ADoNIS provides a practical recipe for constructing differentiable neutrino event generators, applicable beyond the particular physics models implemented here, and this paper demonstrates their use across a wide range of tasks relevant to both theory and experiment.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

NuGlass: A Fast and Interactive 3D Visualization of Neutrino Oscillations

Chao Zhang

Neutrino oscillation phenomenology is usually communicated through two-dimensional projections (probability curves, oscillograms, and bi-probability plots), each of which flattens a function of many parameters (baseline, energy, matter density, mass ordering, and the CP-violating phase) onto a single static figure. We present NuGlass, an open-source, web-based application that renders six complementary, fully interactive 3D views of the same underlying three-flavor evolution: an oscillogram surface, a bi-probability trajectory extruded along energy, a Bloch-sphere projection of the quantum flavor state, a matter-eigenstate phasor decomposition of the oscillation amplitude, a flavor-composition tube along the propagation baseline, and a worldline view that plots the probabilities against L/E and makes the matter-induced breaking of the vacuum degeneracy visible. An oscillation channel switcher, experiment presets, and customizable animation controls are provided. NuGlass can be used both as a research exploration tool and as a public-engagement exhibit. The application runs entirely client-side and is deployed at https://czczc.github.io/nuglass/ .
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Resonant Induced Orbital Electron Capture: Novel method for low-energy $\bar{\nu}_e$ detection

Evgeny Akhmedov, Thierry Lasserre and Leonardo Maturi

We propose a novel approach to detecting low-energy electron antineutrinos based on the induced capture of orbital electrons by nuclei. This process is resonant, requiring the antineutrino energy to precisely match the energy difference between the final and initial atomic systems. For continuous-spectrum sources, the resonance conditions can be satisfied without fine-tuning, and the effective cross sections depend on the spectral intensity of the $\bar{\nu}_e$ flux at the resonance rather than on the neutrino energy itself. This opens the possibility of detecting neutrinos of never previously probed low energies. We identify a number of candidate nuclides that allow transitions to excited states of the daughter nuclei corresponding to resonant $\bar{\nu}_e$ energies below the inverse $\beta$ decay threshold of 1.8 MeV, and we consider a distinctive atomic-nuclear coincidence signature for background rejection. We discuss implications of the proposed method for detecting low-energy reactor neutrinos, geoneutrinos, and keV-scale thermal solar neutrinos. Applications to neutrino oscillation experiments and to reactor monitoring are also briefly discussed.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Probing sub-GeV dark matter through dark matter-electron scattering in the superheated $C_2H_2F_4$ target of the InDEx experiment

Utkarsh Patel, Astitva Kathait and Mala Das

The Indian Dark Matter Search Experiment (InDEx) operates superheated droplet detectors with tetrafluoroethane ($\mathrm{C_2H_2F_4}$) as the active target at the Jaduguda Underground Science Laboratory (JUSL), and has so far probed dark matter (DM) through nuclear recoils at operating temperatures at which the target is insensitive to electron recoils. In this work, we consider six operating temperatures, $T=45$–$70\,^\circ\mathrm{C}$ in steps of $5\,^\circ\mathrm{C}$; the corresponding Seitz thresholds range from $0.61\,\mathrm{keV}$ down to $26.8\,\mathrm{eV}$. The ionization response of the $\mathrm{C_2H_2F_4}$ target is computed in the isolated-atom approximation from Roothaan–Hartree–Fock wavefunctions. The projected $90\%$ confidence-level upper limits on the DM–electron scattering cross section are derived for a dark-photon-type mediator in both the heavy- and light-mediator limits, for a benchmark exposure of $10^3\,\mathrm{kg\,days}$ under the zero-background assumption. For the lowest threshold, $E_{\rm th}=26.8\,\mathrm{eV}$ at $T=70\,^\circ\mathrm{C}$, the search probes DM masses down to $\sim 12\,\mathrm{MeV}$, with the $90\%$ confidence-level limit reaching $2.7\times10^{-41}\,\mathrm{cm}^2$ near $m_\chi\simeq100\,\mathrm{MeV}$ for the contact interaction and $3.0\times10^{-37}\,\mathrm{cm}^2$ near $m_\chi\simeq83\,\mathrm{MeV}$ for the long-range interaction. The electron channel thus extends the reach of InDEx to sub-GeV DM masses, down to $\mathcal{O}(10\,\mathrm{MeV})$, providing a complementary probe of low-mass dark matter alongside its nuclear-recoil program and enhancing sensitivity to DM candidates coupling predominantly to leptons.
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High Energy Physics (Experiment)

Binary Hypothesis Testing: A Robust Framework Against the Look Elsewhere Effect

Han Zhang, Xue-feng Ding, Yu-Feng Li et al. (+3 more)

In particle physics, discovery claims conventionally require an observed significance exceeding $5\sigma$. However, the interpretation of a $5\sigma$ result depends critically on the testing procedure, namely whether the hypothesis is tested at a single pre-specified point in parameter space or by scanning over a range of possible signal locations. This distinction gives rise to the look-elsewhere effect, a concept that is widely used but often interpreted as a simple penalty for scanning. In this work, we reinterpret the look-elsewhere effect as a correction for procedural inconsistency arising when the null distribution is generated under one procedure while the test statistic is evaluated under another. Within the framework of hypothesis testing, we examine its implications and clarify the distinct roles of the look-elsewhere effect in binary and peak-search scenarios. In particular, we show that binary test is robust against the look-elsewhere effect, whereas peak searches require an explicit correction for the search over signal locations. Using a moderate trial factor of approximately 26, calibrated from the ATLAS Higgs search, we show that a $3\sigma$ global significance of peak search can correspond to approximately $4\sigma$ significance of the binary test for the same value of the observed test statistic. This reformulation provides a clearer statistical interpretation of the look-elsewhere effect and offers a more coherent framework for understanding significance claims in particle physics.
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All authors Han Zhang, Xue-feng Ding, Yu-Feng Li, Yi-fang Wang, Liang-jian Wen, Liang Zhan

High Energy Physics (Experiment) · Cross-listed from hep-ph

Probing Dirac Dark Matter in Composite Higgs Models with Xenon and Argon targets

M. G. Belyakova and R. Nevzorov

Recent advancements in direct detection (DD) experiments stimulate the investigation of the interactions of dark matter (DM) with nucleons and nuclei. In the framework of Composite Higgs Models (CHMs) the lightest Dirac composite particle (LDCP) can be stable composing a significant fraction \xi of the observed DM relic abundance. We consider the elastic scattering of the LDCP on nucleons as well as on xenon (Xe) and argon (Ar) nuclei within the CHMs in which the LDCP magnetic moment, its mass and its coupling to the Higgs doublet are suppressed by an approximate U(1) symmetry. The LDCP with non-zero magnetic dipole moment can result in a substantial enhancement of the differential event rate in the DD experiments at low recoil energies of nuclei. Assuming \xi\ge 0.1, we identify the region of the parameter space where such enhancement may be potentially observable. In addition we specify some observables that can be useful in discriminating between the DM fermions with non-zero magnetic moment and other types of dark matter particles which don't have similar electromagnetic properties.
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High Energy Physics (Experiment)

Expected performance of a water Cherenkov detector for reactor antineutrino–electron scattering

Sunhong Kim, Sunwoo Gwon, Youngju Ko et al. (+4 more)

We evaluate the expected performance of a 170-ton water Cherenkov detector for reactor antineutrino–electron elastic scattering at the RENO near-detector site. The reactor-spectrum normalization is extracted from the reconstructed recoil-electron directional distribution using a constrained profile-likelihood fit for an exposure of 365.25 days. For the minimum prompt-hit multiplicity $N_{\mathrm{prompt}}\geq8$ scenario, which neglects PMT radioactivity, the total uncertainty on the reactor-spectrum normalization is ${}^{+1.08\%}_{-1.07\%}$. For the more restrictive $N_{\mathrm{prompt}}\geq20$ scenario, which includes the simulated PMT-radioactivity components, the total uncertainty is ${}^{+1.49\%}_{-1.47\%}$. These results demonstrate that directional information from a water Cherenkov detector can provide percent-level sensitivity to the reactor elastic-scattering normalization.
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All authors Sunhong Kim, Sunwoo Gwon, Youngju Ko, Hokyeong Nam, Juseong Park, Yujin Park, Kim Siyeon