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Journal articleMorgan K, Azuma T, Baptista G, et al., 2026,
Transition-Edge Sensor Spectrometer for Precision Spectroscopy of Antiprotonic Atoms
, IEEE Transactions on Applied Superconductivity, Vol: 36, ISSN: 1051-8223antiProtonic Atom X-ray (PAX) spectroscopy is an experiment that aims to test strong-field quantum electrodynamics (QED) effects by performing high-precision X-ray spectroscopy of antiprotonic atoms. PAX will use a low-energy antiproton beam provided by the Extra Low ENergy Antiproton (ELENA) ring at the European Organization for Nuclear Research (CERN) to create antiprotonic atoms. A superconducting transition-edge sensor (TES) spectrometer will be used to measure the energy of transitions between circular Rydberg states in these atoms. The energy range of interest for the experiment spans 50 keV to 250 keV, and the desired precision for measuring the centroids of the emission lines is 10^{-5}. The spectrometer for PAX is intended to have four 96-pixel TES arrays and will be read out with a microwave superconducting quantum interference device (SQUID) multiplexer. As a step toward building the full instrument, we built a scaled-down version of the spectrometer that was installed at the TEst Line for Machine And Antimatter eXperiments (TELMAX) facility at ELENA in April 2025. The purpose of this deployment was to make an observation of X-ray emission by antiprotonic atoms and to better understand the effect of the pionic charged particle background due to antiproton annihilation on the performance of the TES array. This pilot spectrometer had an array of 60 TES pixels in a compact adiabatic demagnetization refrigerator cryostat. The sensors were read out with a microwave SQUID multiplexer. Each pixel consisted of a molybdenum/gold bilayer TES with a coplanar gold “landing pad” for a bulk tin absorber that was attached by an epoxy joint. We discuss the design of the TES pixels, the microwave SQUID readout, and the cryogenic platform. Finally, we present calibration data obtained at TELMAX using radioactive sources to assess the performance of the spectrometer in the antiproton beam-off condition.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for a boosted Higgs boson decaying to bottom quark pairs in association with a W or Z boson in proton-proton collisions at s=13TeV
, Physics Letters B, Vol: 879, Pages: 140534-140534, ISSN: 0370-2693 -
Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for heavy long-lived charged particles with level-1 trigger scouting data from proton-proton collisions at s=13.6TeV
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 878, ISSN: 0370-2693A search for heavy long-lived charged particles at the LHC is presented. Particles traversing the CMS muon detector across several bunch crossings are searched for using a data sample of proton-proton collisions at s=13.6TeV collected with the CMS detector in 2024, corresponding to an integrated luminosity of 3.7 fb<sup>−1</sup>. This is the first search using the novel level-1 trigger scouting data set collected without any trigger selection, allowing correlations between bunch crossings to be analyzed. The results are interpreted as upper limits on the cross sections of several benchmark processes with pair production of heavy long-lived charged particles. Upper limits on the fiducial cross section of a heavy long-lived charged particle with p<inf>T</inf>>500GeV and | η | < 0.83 are also set in different ranges of β=v/c. This analysis is a proof of concept for the level-1 trigger data scouting system and complements existing searches for heavy long-lived charged particles by extending the sensitivity to lower β values.
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Journal articleAad G, Aakvaag E, Abbott B, et al., 2026,
Search for long-lived particles using displaced vertices of oppositely charged leptons in 140fb−1 of pp collisions at s=13 TeV with the ATLAS detector
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 878, ISSN: 0370-2693A search is presented for long-lived particles decaying into an oppositely charged lepton pair, μ<sup>+</sup>μ<sup>−</sup>, e<sup>+</sup>e<sup>−</sup>, or e <sup> ± </sup> μ <sup>∓</sup>, that form a vertex within the inner tracking system of the ATLAS detector at the Large Hadron Collider, displaced from the primary proton–proton interaction region. The analysis uses the 140 fb<sup>−1</sup> of Run-2 data collected at s=13 TeV by the ATLAS experiment in 2015–2018. The results of the analysis are interpreted in the context of three benchmark models covering masses from 0.1 to 2.2 TeV and a range of mean proper lifetimes times the speed of light from 1 to 10 000 mm. The first model is a generic Z ′ boson pair-produced by a new heavy scalar, with the Z ′ decaying into lepton pairs. The remaining two models are R -parity violating supersymmetric models in which the lightest neutralino χ˜<inf>1</inf><sup>0</sup> decays into ℓ<sup>+</sup>ℓ<sup><sup>′</sup><sup>−</sup></sup>ν (ℓ,ℓ<sup>′</sup>=e, μ). The models differ by the mode of production of the χ˜<inf>1</inf><sup>0</sup>, which can be produced via the decay of pairs of gluinos or of pairs of charginos and neutralinos (χ˜<inf>1</inf><sup>±</sup>χ˜<inf>1</inf><sup>0</sup>, χ˜<inf>1</inf><sup>±</sup>χ˜<inf>2</inf><sup>0</sup>, or χ˜<inf>2</inf><sup>0</sup>χ˜<inf>1</inf><sup>0</sup>). Although each benchmark sample includes pair-produced LLPs, only a single vertex is required to be reconstructed. No dilepton displaced v
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Journal articleWaiton J, Bateman J, Evans J, et al., 2026,
A sterile-neutrino search using data from the MicroBooNE liquid-argon time projection chamber performed in an undergraduate teaching laboratory
, European Journal of Physics, ISSN: 0143-0807<jats:title>Abstract</jats:title> <jats:p>Fundamental particle physics is a key part of an undergraduate physics curriculum, but can be challenging to incorporate into teaching laboratories. We present an undergraduate laboratory experiment that enables students to work with real data from the MicroBooNE liquid-argon time projection chamber to search for the existence of a sterile neutrino: a new, fourth, neutrino state. This search has galvanized physicists for decades, as the existence of sterile neutrinos could play a critical role in understanding fundamental processes in the early universe, provide viable dark matter candidates, and offer a natural explanation for the origin of neutrino masses. From an experimental point of view, anomalies observed in several neutrino experiments provide tantalizing hints of their existence. The analysis presented here, whilst based on real data, has been adapted as a pedagogical tool for an undergraduate teaching laboratory, in which students are asked to develop an understanding of neutrino oscillation theory, analyse a MicroBooNE data sample, and apply statistical methods to search for a potential sterile neutrino. The analysis incorporates machine learning techniques to improve event classification. Students are encouraged to explore these and other methods to optimize their results.</jats:p>
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
First Measurement of Time-Dependent CP Violation in the Flavor-Changing Neutral-Current Decay B^{0}→K_{S}^{0}μ^{+}μ^{-}.
, Phys Rev Lett, Vol: 136A flavor-tagged time-dependent analysis of B^{0}→K_{S}^{0}μ^{+}μ^{-} decays is performed across the full dimuon mass range excluding the J/ψ and ψ(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 13 TeV, corresponding to an integrated luminosity of 9 fb^{-1}. The CP violation parameters are determined to be C=-0.13±0.32±0.04, S=+0.82±0.29±0.05, where the first uncertainties are statistical and the second are systematic. The results are consistent with the standard model prediction. This is the first experimental study of time-dependent CP violation in b→sℓ^{+}ℓ^{-} processes.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for pair production of heavy resonances in final states with a photon and large-radius jets in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msqrt> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext> </mml:mtext> <mml:mi>TeV</mml:mi> </mml:mrow> </mml:math>
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> A search for the pair production of heavy spin- <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>1</a:mn> <a:mo>/</a:mo> <a:mn>2</a:mn> </a:math> or spin- <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mn>3</c:mn> <c:mo>/</c:mo> <c:mn>2</c:mn> </c:math> resonances ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msup> <e:mi>t</e:mi> <e:mo>*</e:mo> </e:msup> </e:math> ) in proton-proton collisions at <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:msqrt> <g:mi>s</g:mi> </g:msqrt> <g:mo>=</g:mo> <g:mn>13</g:mn> <g:mtext> </g:mtext> <g:mtext> </g:mtext> <g:mi>TeV</g:mi> </g:math> is presented. Data collected with the CMS detector at the CERN LHC from 2016 to 2018 corresponding to an integrated luminosity of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mn>138</i:mn> <i:mtext
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
Measurement of the Top-Quark Production Cross Section and Charge Asymmetry at LHCb.
, Phys Rev Lett, Vol: 136The first measurements of the top- and antitop-quark differential production cross sections and the top-quark charge asymmetry in the forward region are presented, using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.4 fb^{-1}. The total production cross sections of top and antitop quarks are also determined. Measurements are performed using the μ+b-jet final state within a fiducial region defined by b-jet p_{T,jet}>50 GeV and pseudorapidity 2.2<η_{jet}<4.0, with the muon from the W-boson decay required to have p_{T,μ}>25 GeV and 2.0<η_{μ}<4.5. The muon and b-jet system must satisfy p_{T}(μ+jet)>20 GeV. The measured integrated production cross sections for the top and antitop quarks are σ_{t}=0.95±0.04±0.08±0.02 pb, σ_{t[over ¯]}=0.81±0.03±0.07±0.02 pb, where the first uncertainty is statistical, the second systematic, and the third accounts for the luminosity uncertainty. The top-quark charge asymmetry is measured to be A_{C}^{t}=0.08±0.03±0.01, where the first uncertainty is statistical and the second is systematic. These results are consistent with next-to-leading order Standard Model predictions.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2026,
Measurement of the ratio of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>c</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo stretchy="false">→</mml:mo> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msub> <mml:mi>ν</mml:mi> <mml:mi>τ</mml:mi> </mml:msub> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>c</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo stretchy="false">→</mml:mo> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msub> <mml:mi>ν</mml:mi> <mml:mi>μ</mml:mi> </mml:msub> </mml:math> branching fractions using three-prong <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>τ</mml:mi> </mml:math> lepton decays
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> The ratio between the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:msubsup> <a:mi>B</a:mi> <a:mi>c</a:mi> <a:mo>+</a:mo> </a:msubsup> <a:mo stretchy="false">→</a:mo> <a:mrow> <a:mi>J</a:mi> <a:mo>/</a:mo> <a:mi>ψ</a:mi> </a:mrow> </a:mrow> <a:msup> <a:mi>τ</a:mi> <a:mo>+</a:mo> </a:msup> <a:msub> <a:mi>ν</a:mi> <a:mi>τ</a:mi> </a:msub> </a:math> and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mrow> <d:msubsup> <d:mi>B</d:mi> <d:mi>c</d:mi> <d:mo>+</d:mo> </d:msubsup> <d:mo stretchy="false">→</d:mo> <d:mrow> <d:mi>J</d:mi> <d:mo>/</d:mo> <d:mi>ψ</d:mi> </d:mrow> </d:mrow> <d:msup>
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Journal articleAbbaslu S, Abed Abud A, Acciarri R, et al., 2026,
Measurement of exclusive <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>π</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> -argon interactions using ProtoDUNE-SP
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> We present the measurement of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>π</a:mi> <a:mo>+</a:mo> </a:msup> </a:math> -argon inelastic cross sections using the ProtoDUNE single-phase liquid argon time projection chamber in the incident <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msup> <c:mi>π</c:mi> <c:mo>+</c:mo> </c:msup> </c:math> kinetic energy range of 500–800 MeV in multiple exclusive channels (absorption, charge exchange, and the remaining inelastic interactions). The results of this analysis are important inputs to simulations of liquid argon neutrino experiments such as the Deep Underground Neutrino Experiment and the Short Baseline Neutrino program at Fermi National Accelerator Laboratory. They will be employed to improve the modeling of final state interactions within neutrino event generators used by these experiments, as well as the modeling of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msup> <e:mi>π</e:mi> <e:mo>+</e:mo> </e:msup> </e:math> -argon secondary interactions within the liquid argon. This is the first measurement of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:msup
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Journal articleSchulte JF, Ramhorst B, Sun C, et al., 2026,
hls4ml: A Flexible, Open Source Platform for Deep Learning Acceleration on Reconfigurable Hardware
, ACM Transactions on Reconfigurable Technology and Systems, Vol: 19, ISSN: 1936-7406We present hls4ml, a free and open source platform that translates machine learning (ML) models from modern deep learning frameworks into high-level synthesis (HLS) code that can be integrated into full designs for field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs). With its flexible and modular design, hls4ml supports a large number of deep learning frameworks and can target HLS compilers from several vendors, including Vitis HLS, Intel oneAPI and Catapult HLS. Together with a wider eco-system for software-hardware co-design, hls4ml has enabled the acceleration of ML inference in a wide range of commercial and scientific applications where low latency, resource usage, and power consumption are critical. In this article, we describe the structure and functionality of the hls4ml platform. The overarching design considerations for the generated HLS code are discussed, together with selected performance results.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2026,
Search for dark matter production in association with bottom quarks and a lepton pair in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026A search is performed for dark matter produced in association with bottom quarks and a pair of electrons or muons in data collected with the CMS detector at the LHC, corresponding to 138 fb<sup>−1</sup> of integrated luminosity of proton-proton collisions at a center-of-mass energy of 13 TeV. For the first time at the LHC, the associated production of a bottom quark-antiquark pair and a new heavy neutral Higgs boson (H) that subsequently decays into a leptonically decaying Z boson and a pseudoscalar (a) is explored. The latter acts as a dark matter mediator in the context of the two Higgs doublet model plus a pseudoscalar (2HDM+a). Multivariate techniques that target a wide range of mass configurations for the H and a particles are used. The observations are consistent with the expectations from standard model processes. Upper limits at 95% confidence level are set on the product of cross section and branching fraction of the new particles, ranging from 10<sup>−2</sup> pb for an H mass of 400 GeV to 10<sup>−3</sup> pb for an H mass of 2000 GeV. Constraints on the parameter space of a benchmark 2HDM+a model are derived and compared with expectations in the context of cosmological predictions.
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Journal articleYankelevich A, Abe K, Asaoka Y, et al., 2026,
Measurement of the solar neutrino interaction rate below 3.49 MeV in Super-Kamiokande-IV
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> Super-Kamiokande (SK) has observed <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mmultiscripts> <a:mrow> <a:mi mathvariant="normal">B</a:mi> </a:mrow> <a:mprescripts/> <a:none/> <a:mrow> <a:mn>8</a:mn> </a:mrow> </a:mmultiscripts> </a:mrow> </a:math> solar neutrino elastic scattering at recoil electron kinetic energies ( <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:msub> <d:mi>E</d:mi> <d:mi>kin</d:mi> </d:msub> </d:math> ) as low as 3.49 MeV to study neutrino flavor conversion within the Sun. At SK-observable energies, these conversions are dominated by the Mikheyev-Smirnov-Wolfenstein effect. An upturn in the electron neutrino survival probability in which vacuum neutrino oscillations become dominant is predicted to occur at lower energies, but radioactive background increases exponentially with decreasing energy. New machine learning approaches provide substantial background reduction below 3.49 MeV such that statistical extraction of solar neutrino interactions becomes feasible. This article presents an analysis of the solar neutrino interaction rate at <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline">
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Journal articleAad G, Aakvaag E, Abbott B, et al., 2026,
Search for Higgs bosons produced in association with a high-energy photon via vector-boson fusion and decaying to a pair of b-quarks in the ATLAS detector
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 877, ISSN: 0370-2693A search for Standard Model Higgs bosons produced in association with a high-energy photon and decaying to bb¯ is performed using 133 fb<sup>−1</sup> of s=13 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider at CERN. The photon requirement reduces the multijet background, and the H→bb¯ decay is the dominant decay mode. Event selection requirements target events produced by vector-boson fusion, the dominant production mode in this channel. Several improvements enhance the search sensitivity compared to previous measurements. These improvements include better background modelling and characterization, the use of a neural-network classifier, and an updated signal extraction strategy adopting a direct binned-likelihood fit to the classifier output. With these improvements, the Higgs boson signal strength is measured to be 0.2 ± 0.7 relative to the Standard Model prediction. This corresponds to an observed significance of 0.3 standard deviations, compared to an expectation of 1.5 standard deviations assuming the Standard Model.
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Journal articleCollaboration TCMS, 2026,
Wasserstein normalized autoencoder for anomaly detection
, Machine Learning: Science and Technology, Vol: 7, Pages: 035030-035030<jats:title>Abstract</jats:title> <jats:p>A novel anomaly detection algorithm is presented. The Wasserstein normalized autoencoder (WNAE) is a normalized probabilistic model that minimizes the Wasserstein distance between the learned probability distribution—a Boltzmann distribution where the energy is the reconstruction error of the autoencoder (AE)—and the distribution of the training data. This algorithm has been developed and applied to the identification of semivisible jets—conical sprays of visible standard model (SM) particles and invisible dark matter states—with the CMS experiment at the CERN LHC. Trained on jets of particles from simulated SM processes, the WNAE is shown to learn the probability distribution of the input data in a fully unsupervised fashion, such that it effectively identifies new physics jets as anomalies. The model exhibits stable, convergent training and recovers strong classification performance for a wide range of signals against the selected background process, for which a standard AE fails because of outlier reconstruction. In addition, the model improves upon standard normalized autoencoders while remaining fully agnostic to the signal. The WNAE directly tackles the problem of outlier reconstruction, a common failure mode of autoencoders in anomaly detection tasks.</jats:p>
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Journal articleBaynham CFA, Hobson R, Buchmüller O, et al., 2026,
A prototype differential atom interferometer for fundamental physics.
, Nature, Vol: 654, Pages: 622-628Gravitational waves and ultralight dark matter are among the most compelling frontiers in fundamental physics, motivating proposals for very-long-baseline atom interferometerssuch as AION1, MAGIS2, AICE3 and AEDGE4 that aim to detect at frequencies at which ground-based5 and space-borne6 laser interferometers lose sensitivity. Very-long-baseline atom interferometers look for signals by comparing the quantum phase evolution of widely separated atomic ensembles interrogated by a common laser. However, their performance depends critically on suppressing noise sources, particularly laser phase noise. The experimental validation of such noise rejection remains an important challenge. Here we demonstrate a prototype differential atom interferometer based on the single-photon clock transition of fermionic 87Sr. Thus, we obtain a gradiometer configuration with a species intrinsically suited to kilometre-scale and space-baseline operation. The instrument operates at the standard quantum limit7 with no excess noise beyond atom shot noise. The differential configuration maintains quantum-limited sensitivity in the presence of several radians of artificially injected laser phase noise per shot, which emulates the conditions expected in a very-long-baseline atom interferometer. We also demonstrate the recovery of coherent oscillatory signals across a broad frequency range under fully phase-randomized conditions, a capability that is inaccessible to a single interferometer operating in the same regime. These results provide an experimental validation of the noise-immune measurement principle underlying very-long-baseline atom interferometers and mark an important step towards next-generation quantum sensors for gravitational-wave detection and searches for ultralight dark matter8,9.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Measurement of the Higgs boson total decay width using the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>H</mml:mi> <mml:mo stretchy="false">→</mml:mo> <mml:mi>W</mml:mi> <mml:mi>W</mml:mi> <mml:mo stretchy="false">→</mml:mo> <mml:mi>e</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>μ</mml:mi> <mml:mi>ν</mml:mi> </mml:mrow> </mml:math> decay channel in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext> </mml:mtext> <mml:mi>TeV</mml:mi> </mml:math>
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> The Higgs boson (H) decay width is determined from the ratio of off- and on-shell production of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>H</a:mi> <a:mo stretchy="false">→</a:mo> <a:mi>W</a:mi> <a:mi>W</a:mi> <a:mo stretchy="false">→</a:mo> <a:mi>e</a:mi> <a:mi>ν</a:mi> <a:mi>μ</a:mi> <a:mi>ν</a:mi> </a:math> using proton–proton collision data corresponding to an integrated luminosity of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mn>138</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:msup> <e:mi>fb</e:mi> <e:mrow> <e:mo>−</e:mo> <e:mn>1</e:mn> </e:mrow> </e:msup> </e:math> collected at <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:msqrt> <g:mi>s</g:mi> </g:msqrt> <g:mo>=</g:mo> <g:mn>13</g:mn> <g:mtext> </g:mtext> <g:mtext>
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for dark matter produced in association with a Higgs boson decaying to bottom quarks in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext> </mml:mtext> <mml:mi>TeV</mml:mi> </mml:math>
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> A search for dark matter particles produced in association with a Higgs boson decaying to a bottom quark-antiquark pair in proton-proton collisions at <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:msqrt> <a:mrow> <a:mi>s</a:mi> </a:mrow> </a:msqrt> <a:mo>=</a:mo> <a:mn>13</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>TeV</a:mi> </a:mrow> </a:math> is presented. The data, collected with the CMS detector at the LHC, correspond to an integrated luminosity of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mn>101</c:mn> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:msup> <c:mrow> <c:mi>fb</c:mi> </c:mrow> <c:mrow> <c:mo>−</c:mo> <c:mn>1</c:mn> </c:mrow> </c:msup> </c:mrow> </c:math> . The analysis is performed in exclusive categories targeting both Lorentz-boosted (merged) and resolved <e:math xmlns
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for Higgsinos in final states with low-momentum lepton-track pairs at 13 TeV
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> We present a search for the pair production of Higgsinos in final states with large missing transverse momentum and either two reconstructed muons or a reconstructed lepton (muon or electron) and an isolated track. The analyzed data correspond to proton-proton collisions with an integrated luminosity of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>137</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:msup> <a:mi>fb</a:mi> <a:mrow> <a:mo>−</a:mo> <a:mn>1</a:mn> </a:mrow> </a:msup> </a:math> , collected by the CMS experiment at <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msqrt> <c:mi>s</c:mi> </c:msqrt> <c:mo>=</c:mo> <c:mn>13</c:mn> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:mi>TeV</c:mi> </c:math> in 2016, 2017, and 2018. The signal scenario assumes four nearly mass degenerate Higgsino mass eigenstates: two neutralino states <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mrow> <e:msubsup> <e:mrow> <e:mover accen
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Journal articleAbratenko P, Andrade Aldana D, Arellano L, et al., 2026,
Inclusive Search for Anomalous Single-Photon Production in MicroBooNE.
, Phys Rev Lett, Vol: 136We present an inclusive search for anomalous production of single-photon events from neutrino interactions in the MicroBooNE experiment. The search and its signal definition are motivated by the previous observation of a low-energy excess of electromagnetic shower events from the MiniBooNE experiment. We use the Wire-Cell reconstruction framework to select a sample of inclusive single-photon final-state interactions with a final efficiency and purity of 7.0% and 40.2%, respectively. We leverage simultaneous measurements of sidebands of charged current ν_{μ} interactions and neutral current interactions producing π^{0} mesons to constrain signal and background predictions and reduce uncertainties. We perform a blind analysis using a dataset collected from February 2016 to July 2018, corresponding to an exposure of 6.34×10^{20} protons on target from the Booster Neutrino Beam at Fermilab. In the full signal region, we observe agreement between the data and the prediction, with a goodness-of-fit p value of 0.11. We then isolate a subsample of these events containing no visible protons, and observe 93±22(stat)±35(syst) data events above prediction, corresponding to just above 2σ local significance, concentrated at shower energies below 600 MeV.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
Searches for B^{0}→K^{+}π^{-}τ^{+}τ^{-} and B_{s}^{0}→K^{+}K^{-}τ^{+}τ^{-} Decays.
, Phys Rev Lett, Vol: 136The first searches for B^{0}→K^{+}π^{-}τ^{+}τ^{-} and B_{s}^{0}→K^{+}K^{-}τ^{+}τ^{-} decays at the LHCb experiment are conducted with pp collision data corresponding to an integrated luminosity of 5.4 fb^{-1}. The tau leptons are reconstructed using the τ^{+}→μ^{+}ν[over ¯]_{τ}ν_{μ} decay and the results are presented in bins of K^{+}π^{-} or K^{+}K^{-} mass. No signal is observed and upper limits are set on the branching fractions. The searches result in the first upper limits for B^{0}→K^{+}π^{-}τ^{+}τ^{-} decays outside the K^{*}(892)^{0} region in K^{+}π^{-} mass and the first limits for B_{s}^{0}→K^{+}K^{-}τ^{+}τ^{-} decays. The searches are recast into limits on the decays B^{0}→K^{*}(892)^{0}τ^{+}τ^{-} and B_{s}^{0}→ϕ(1020)τ^{+}τ^{-}, yielding 2.8×10^{-4} (2.5×10^{-4}) and 4.7×10^{-4} (4.1×10^{-4}) at the 95% (90%) confidence level, respectively. For the decay B^{0}→K^{*}(892)^{0}τ^{+}τ^{-}, this result improves on the current best upper limit by an order of magnitude.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2026,
First Evidence for Mixing-Induced CP Violation in B_{s}^{0}→J/ψϕ(1020) Decays in pp Collisions at sqrt[s]=13 TeV.
, Phys Rev Lett, Vol: 136A novel machine-learning-based flavor-tagging algorithm combining same-side and opposite-side tagging is used to obtain the equivalent of 27 500 tagged B_{s}^{0}→J/ψϕ(1020) decays from pp collisions at sqrt[s]=13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 96.5 fb^{-1}. A time- and flavor-dependent angular analysis of the μ^{+}μ^{-}K^{+}K^{-} final state, consistent with a ϕ(1020)→K^{+}K^{-} decay, is used to measure parameters of the B_{s}^{0}-B[over ¯]_{s}^{0} system. The weak phase is measured to be ϕ_{s}=-73±22(stat)±10(syst) mrad, which, combined with the sqrt[s]=8 TeV CMS result, gives ϕ_{s}=-75±23 mrad. This value differs from zero by 3.2 standard deviations, providing the first evidence for mixing-induced CP violation in B_{s}^{0}→J/ψϕ(1020) decays. All measured physics parameters are found to agree with standard model predictions where available.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for Light Pseudoscalar Bosons, Pair-Produced in Higgs Boson Decays in the Four-Electron Final State in Proton-Proton Collisions at sqrt[s]=13 TeV.
, Phys Rev Lett, Vol: 136A search for pairs of light neutral pseudoscalar bosons (A) resulting from the decay of a Higgs boson is performed. The search is conducted using LHC proton-proton collision data at sqrt[s]=13 TeV, collected with the CMS detector in 2016-2018 and corresponding to an integrated luminosity of 138 fb^{-1}. The A boson decays into a highly collimated electron-positron pair. A novel multivariate algorithm using tracks and calorimeter information is developed to identify these distinctive signatures, and events are selected with two such merged electron-positron pairs. No significant excess above the standard model background predictions is observed. Upper limits on the branching fraction for H→AA→4e are set at 95% confidence level, for masses between 10 and 100 MeV and proper decay lengths below 100 μm, reaching branching fraction sensitivities as low as 10^{-5}. This is the first search for Higgs boson decays to four electrons via light pseudoscalars at the LHC. It significantly improves the experimental sensitivity to axionlike particles with masses below 100 MeV .
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Journal articleSchueler J, Araújo HM, Balashov SN, et al., 2026,
Overlap-aware segmentation for topological reconstruction of obscured objects
, Machine Learning Science and Technology, Vol: 7The separation of overlapping objects presents a significant challenge in scientific imaging. While deep learning segmentation-regression algorithms can predict pixel-wise intensities, they typically treat all regions equally rather than prioritizing overlap regions where attribution is most ambiguous. Recent advances in instance segmentation show that weighting regions of pixel overlap in training can improve segmentation boundary predictions in regions of overlap, but this idea has not yet been extended to segmentation regression. We address this with Overlap-Aware Segmentation Of ImageS (OASIS): a new segmentation-regression framework with a weighted loss function designed to prioritize regions of object-overlap during training, enabling extraction of pixel intensities and topological features from heavily obscured objects. We demonstrate OASIS in the context of the MIGDAL experiment, which aims to directly image the Migdal effect–a rare process where electron emission is induced by nuclear scattering–in a low-pressure optical time projection chamber. This setting poses an extreme test case, as the target for reconstruction is a faint electron recoil track which is often heavily-buried within the order(s)-of-magnitude brighter nuclear recoil track. Compared to unweighted segmentation regression, we demonstrate OASIS’s novel overlap region-targeted loss function weight to be the single most important training weight for improving intensity and topological reconstructions of the low-energy electron tracks that tend to be most dominated by pixel overlap. Averaging over eight training campaigns, we further show the addition of overlap-targeted weights to improve median intensity reconstruction errors from (Formula presented) (Formula presented) to (Formula presented) (Formula presented) for these low-energy electrons. These performance gains demonstrate OASIS as a generalizable methodology for recovering obscured signals in overlap-dominated regions
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2026,
Search for the nonresonant and resonant production of a Higgs boson in association with an additional scalar boson in the γγττ final state in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026The results of a search for the production of two scalar bosons in final states with two photons and two tau leptons are presented. The search considers both nonresonant production of a Higgs boson pair, HH, and resonant production via a new boson X which decays either to HH or to H and a new scalar Y. The analysis uses up to 138 fb<sup>−1</sup> of proton-proton collision data, recorded between 2016 and 2018 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV. No evidence for signal is found in the data. For the nonresonant production, the observed (expected) upper limit at 95% confidence level (CL) on the HH production cross section is set at 930 (740) fb, corresponding to 33 (26) times the standard model prediction. At 95% CL, HH production is observed (expected) to be excluded for values of κ<inf>λ</inf> outside the range between −12 (−9.4) and 17 (15). Observed (expected) upper limits at 95% CL for the X → HH cross section are found to be within 160 to 2200 (200 to 1800) fb, depending on the mass of X. In the X → Y(ττ)H(γγ) search, the observed (expected) upper limits on the product of the production cross section and decay branching fractions vary between 0.059–1.2 fb (0.087–0.68 fb). For the X → Y(γγ)H(ττ) search the observed (expected) upper limits on the product of the production cross section and Y → γγ branching fraction vary between 0.69–15 fb (0.73–8.3 fb) in the low Y mass search, tightening constraints on the next-to-minimal supersymmetric standard model, and between 0.64–10 fb (0.70–7.6 fb) in the high Y mass search.
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Journal articleZunica G, Zuliani D, Zou Q, et al., 2026,
Amplitude analysis of B0→ηc(1S)K+π- decays
, European Physical Journal C, Vol: 86, ISSN: 1434-6044An amplitude analysis of the B0→ηc(1S)K+π- decays with ηc(1S)→pp¯ is performed using a sample corresponding to an integrated luminosity of 9fb-1 of pp collision data collected by the LHCb detector at centre-of-mass energies of s = 7, 8 and 13TeV. The data are described with a model including only intermediate contributions from known K∗0 resonances. Evidence for an exotic resonance in the ηc(1S)π- system, reported in a previous analysis of this decay channel, is not confirmed. The inclusive branching fraction of the B0→ηc(1S)K+π- decays is measured to be (Formula presented.) where the first uncertainty is statistical, the second systematic, and the third arises from the limited knowledge of external branching fractions.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for long-lived particles using displaced vertices with low-momentum tracks in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026A search for long-lived particles using final states including a displaced vertex with low-momentum tracks, large missing transverse momentum, and a jet from initial-state radiation is presented. This search uses proton-proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC in 2017 and 2018, with a total integrated luminosity of 100 fb<sup>−1</sup>. This analysis adopts specific supersymmetric (SUSY) coannihilation scenarios as benchmark signal models, characterized by a next-to-lightest SUSY particle (NLSP) with a mass difference of less than 25 GeV relative to the lightest SUSY particle, assumed to be a bino-like neutralino. In the top squark t~ NLSP model, the NLSP is a long-lived t~, while in the bino-wino NLSP scenario, the mass-degenerate NLSPs are a wino-like long-lived neutralino and a short-lived chargino. The search excludes top squarks with masses less than 400–1100 GeV and wino-like neutralinos with masses less than 220–550 GeV, depending on the signal parameters, including the mass difference, mass, and lifetime of the long-lived particle. It sets the most stringent limits to date for the t~ and bino-wino NLSP models.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2026,
Exploring small-angle emissions in charm quark jets in proton-proton collisions at s=5.02 TeV
, Journal of High Energy Physics, Vol: 2026A measurement of the angular structure of inclusive jets and those containing a prompt D<sup>0</sup> meson in proton-proton collisions at the LHC at a center-of-mass energy of 5.02 TeV is presented. The data corresponding to an integrated luminosity of 301 pb<sup>−1</sup> were collected by the CMS experiment in 2017. Two jet grooming algorithms, late-k<inf>T</inf> and soft drop, are used to study the intrajet radiation pattern using iterative Cambridge-Aachen declustering. The splitting-angle distributions of jets with transverse momentum (p<inf>T</inf>) of around 100 GeV, obtained with these two algorithms, show that there is a shift of the distribution for jets containing a prompt D<sup>0</sup> meson with respect to inclusive jets. The suppression of emissions at small angles observed in the late-k<inf>T</inf> grooming approach is consistent with the dead-cone effect, whereas the similar suppression for splittings selected with the soft-drop algorithm appears to be induced by gluon splitting to charm quark-antiquark pairs at large angles. The measured distributions are corrected to the particle level and can be used to constrain model predictions for the substructure of high-p<inf>T</inf> charm quark jets.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2026,
Measurement of the dineutrino system kinematic variables in dileptonic top quark pair production in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026Differential top quark pair production cross sections are measured in the dilepton final states e<sup>+</sup>e<sup>−</sup>, μ<sup>+</sup>μ<sup>−</sup>, and e<sup>±</sup>μ<sup>∓</sup>, as a function of kinematic variables of the two-neutrino system: the transverse momentum pTνν of the dineutrino system, the minimum distance in azimuthal angle between p→Tνν and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at s=13 TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb<sup>−1</sup>. The measured cross sections are unfolded to the particle level using an unregularized least squares method. Results are compared with predictions by the standard model of particle physics, and found to be in agreement with theoretical calculations as well as Monte Carlo simulations.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Measurements of electroweak production of a photon in association with two jets in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026The first observation of electroweak production of a photon in association with two forward jets in proton-proton collisions is presented. The measurement uses data recorded by the CMS experiment at the LHC during 2016–2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb<sup>−1</sup>. The analysis is performed in a region enriched in photon production via vector boson fusion, with a requirement on the transverse momentum of the photon to exceed 200 GeV. The cross section is measured to be 202−32+36 fb, at a significance with respect to the null hypothesis that exceeds five standard deviations. This is in agreement with the standard model prediction of 177−12+13 fb. Differential cross sections are measured as a function of various observables. Limits are set on dimension-6 effective field theory operators that contribute to the WWγ interaction. The observed 95% confidence intervals for the corresponding Warsaw basis Wilson coefficients c<inf>W</inf> and c<inf>HWB</inf> are [−0.11, 0.16] and [−1.6, 1.5], respectively.
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