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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Nonresonant central exclusive production of charged-hadron pairs in proton-proton collisions at √𝑠 =13 TeV
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 109, ISSN: 1550-2368The central exclusive production of charged-hadron pairs in 𝑝𝑝 collisions at a center-of-mass energy of 13 TeV is examined, based on data collected in a special high-𝛽* run of the LHC. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, 𝑚𝜋+𝜋− <0.7 or 𝑚𝜋+𝜋− >1.8 GeV. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared exchanged four-momenta, and 𝑚𝜋+𝜋− are measured in a wide region of scattered proton transverse momenta, between 0.2 and 0.8 GeV, and for pion rapidities |𝑦| <2. A rich structure of interactions related to double-pomeron exchange is observed. A parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be interpreted as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities are determined that are related to the pomeron cross section, proton-pomeron and meson-pomeron form factors, pomeron trajectory and intercept, and coefficients of diffractive eigenstates of the proton.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
Amplitude analysis of the Λb0→pK−γ decay
, Journal of High Energy Physics, Vol: 2024The resonant structure of the radiative decay Λb0→pK−γ in the region of proton-kaon invariant-mass up to 2.5 GeV/c2 is studied using proton-proton collision data recorded at centre-of-mass energies of 7, 8, and 13 TeV collected with the LHCb detector, corresponding to a total integrated luminosity of 9 fb−1. Results are given in terms of fit and interference fractions between the different components contributing to this final state. Only Λ resonances decaying to pK− are found to be relevant, where the largest contributions stem from the Λ(1520), Λ(1600), Λ(1800), and Λ(1890) states.
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Journal articleAalbers J, Akerib DS, Al Musalhi AK, et al., 2024,
New constraints on ultraheavy dark matter from the LZ experiment
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 109, ISSN: 1550-2368Searches for dark matter with liquid xenon time projection chamber experiments have traditionally focused on the region of the parameter space that is characteristic of weakly interacting massive particles, ranging from a few GeV/𝑐2 to a few TeV/𝑐2. Models of dark matter with a mass much heavier than this are well motivated by early production mechanisms different from the standard thermal freeze-out, but they have generally been less explored experimentally. In this work, we present a reanalysis of the first science run of the LZ experiment, with an exposure of 0.9 tonne×yr, to search for ultraheavy particle dark matter. The signal topology consists of multiple energy deposits in the active region of the detector forming a straight line, from which the velocity of the incoming particle can be reconstructed on an event-by-event basis. Zero events with this topology were observed after applying the data selection calibrated on a simulated sample of signal-like events. New experimental constraints are derived, which rule out previously unexplored regions of the dark matter parameter space of spin-independent interactions beyond a mass of 1017 GeV/𝑐2.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for long-lived particles using displaced vertices and missing transverse momentum in proton-proton collisions at √𝑠 =13 TeV
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 109, ISSN: 1550-2368A search for the production of long-lived particles in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC is presented. The search is based on data collected by the CMS experiment in 2016–2018, corresponding to a total integrated luminosity of 137 fb−1. This search is designed to be sensitive to long-lived particles with mean proper decay lengths between 0.1 and 1000 mm, whose decay products produce a final state with at least one displaced vertex and missing transverse momentum. A machine learning algorithm, which improves the background rejection power by more than an order of magnitude, is applied to improve the sensitivity. The observation is consistent with the standard model background prediction, and the results are used to constrain split supersymmetry (SUSY) and gauge-mediated SUSY breaking models with different gluino mean proper decay lengths and masses. This search is the first CMS search that shows sensitivity to hadronically decaying long-lived particles from signals with mass differences between the gluino and neutralino below 100 GeV. It sets the most stringent limits to date for split-SUSY models and gauge-mediated SUSY breaking models with gluino proper decay length less than 6 mm.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Combined search for electroweak production of winos, binos, higgsinos, and sleptons in proton-proton collisions at √𝑠 =13 TeV
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 109, ISSN: 1550-2368A combination of the results of several searches for the electroweak production of the supersymmetric partners of standard model bosons, and of charged leptons, is presented. All searches use proton-proton collision data at √𝑠 =13 TeV recorded with the CMS detector at the LHC in 2016–2018. The analyzed data correspond to an integrated luminosity of up to 137 fb−1. The results are interpreted in terms of simplified models of supersymmetry. Two new interpretations are added with this combination: a model spectrum with the bino as the lightest supersymmetric particle together with mass-degenerate Higgsinos decaying to the bino and a standard model boson, and the compressed-spectrum region of a previously studied model of slepton pair production. Improved analysis techniques are employed to optimize sensitivity for the compressed spectra in the wino and slepton pair production models. The results are consistent with expectations from the standard model. The combination provides a more comprehensive coverage of the model parameter space than the individual searches, extending the exclusion by up to 125 GeV, and also targets some of the intermediate gaps in the mass coverage.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for stealth supersymmetry in final states with two photons, jets, and low missing transverse momentum in proton-proton collisions at √s=13 TeV
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 109, ISSN: 1550-2368he results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (𝑝missT), are reported. The study is based on a sample of proton-proton collisions at √𝑠=13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb−1. As LHC results continue to constrain the parameter space of the minimal supersymmetric standard model, the low 𝑝missT regime is increasingly valuable to explore. To estimate the backgrounds due to standard model processes in such events, we apply corrections derived from simulation to an estimate based on a control selection in data. The results are interpreted in the context of simplified stealth supersymmetry models with gluino and squark pair production. The observed data are consistent with the standard model predictions, and gluino (squark) masses of up to 2150 (1850) GeV are excluded at the 95% confidence level.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Observation of the 𝐽/𝜓 →𝜇+𝜇−𝜇+𝜇− decay in proton-proton collisions at √𝑠 =13 TeV
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 109, ISSN: 1550-2368The 𝐽/𝜓 →𝜇+𝜇−𝜇+𝜇− decay has been observed with a statistical significance in excess of five standard deviations. The analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 33.6 fb−1. Normalizing to the 𝐽/𝜓 →𝜇+𝜇− decay mode leads to a branching fraction of [10.1+3.3−2.7(stat) ±0.4(syst)] ×10−7, a value that is consistent with the standard model prediction.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for the lepton flavor violating τ → 3μ decay in proton-proton collisions at √s=13 TeV
, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 853, ISSN: 0370-2693A search for the lepton flavor violating τ → 3μ decay is performed using proton-proton collision events at acenter-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2017–2018, corresponding to anintegrated luminosity of 97.7 fb−1. Tau leptons produced in both heavy-flavor hadron and W boson decays areexploited in the analysis. No evidence for the decay is observed. The results of this search are combined withan earlier null result based on data collected in 2016 to obtain a total integrated luminosity of 131 fb−1. Theobserved (expected) upper limits on the branching fraction (τ → 3μ) at confidence levels of 90 and 95% are2.9 × 10−8 (2.4 × 10−8) and 3.6 × 10−8 (3.0 × 10−8), respectively
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Journal articleAbend S, Allard B, Alonso I, et al., 2024,
Terrestrial very-long-baseline atom interferometry: workshop summary
, AVS Quantum Science, Vol: 6, ISSN: 2639-0213This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more kilometer--scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions.
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Journal articleAbbaneo D, Ahmad S, Albanese R, et al., 2024,
Results and Perspectives from the First Two Years of Neutrino Physics at the LHC by the SND@LHC Experiment
, SYMMETRY-BASEL, Vol: 16 -
Journal articleBrown C, Spannowsky M, Tapper A, et al., 2024,
Quantum pathways for charged track finding in high-energy collisions
, Frontiers in Artificial Intelligence, Vol: 7, ISSN: 2624-8212In high-energy particle collisions, charged track finding is a complex yet crucial endeavor. We propose a quantum algorithm, specifically quantum template matching, to enhance the accuracy and efficiency of track finding. Abstracting the Quantum Amplitude Amplification routine by introducing a data register, and utilizing a novel oracle construction, allows data to be parsed to the circuit and matched with a hit-pattern template, without prior knowledge of the input data. Furthermore, we address the challenges posed by missing hit data, demonstrating the ability of the quantum template matching algorithm to successfully identify charged-particle tracks from hit patterns with missing hits. Our findings therefore propose quantum methodologies tailored for real-world applications and underline the potential of quantum computing in collider physics.
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Journal articleTumasyan A, Adam W, Andrejkovic JW, et al., 2024,
Search for a new resonance decaying into two spin-0 bosons in a final state with two photons and two bottom quarks in proton-proton collisions at √<i>s</i>=13 TeV
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for a third-generation leptoquark coupled to a τ lepton and a b quark through single, pair, and nonresonant production in proton-proton collisions at √<i>s</i>=13 TeV
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleAaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024,
Measurements of the branching fraction ratio <i>B</i>(φ → μ<SUP>+</SUP>μ<SUP>-</SUP>)/<i>B</i>(φ → e<SUP>+</SUP>e<SUP>-</SUP>) with charm meson decays
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
Measurement of associated Jψ-ψ(2S) production cross-section in pp collisions at √s=13 TeV
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleAaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024,
A measurement of ΔΓ<sub>s</sub>
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleArmano M, Audley H, Baird J, et al., 2024,
Nano-Newton electrostatic force actuators for femto-Newton-sensitive measurements: System performance test in the LISA Pathfinder mission
, PHYSICAL REVIEW D, Vol: 109, ISSN: 2470-0010 -
Journal articleHenry S, Su H, Akhter S, et al., 2024,
Measurement of electron neutrino and antineutrino cross sections at low momentum transfer
, PHYSICAL REVIEW D, Vol: 109, ISSN: 2470-0010 -
Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Measurement of the primary Lund jet plane density in proton-proton collisions at √s=13 TeV
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleAalbers J, Akerib DS, Al Musalhi AK, et al., 2024,
First constraints on WIMP-nucleon effective field theory couplings in an extended energy region from LUX-ZEPLIN
, PHYSICAL REVIEW D, Vol: 109, ISSN: 2470-0010 -
Conference paperBarbone M, Brown C, Radburn-Smith B, et al., 2024,
Deployment of ML in changing environments
, 26th International Conference on Computing in High Energy and Nuclear Physics (CHEP 2023), Publisher: EDP Sciences, ISSN: 2100-014XThe High-Luminosity LHC upgrade of the CMS experiment will utilise a large number of Machine Learning (ML) based algorithms in its hardware-based trigger. These ML algorithms will facilitate the selection of potentially interesting events for storage and offline analysis. Strict latency and resource requirements limit the size and complexity of these models due to their use in a high-speed trigger setting and deployment on FPGA hardware. It is envisaged that these ML models will be trained on large, carefully tuned, Monte Carlo datasets and subsequently deployed in a real-world detector environment. Not only is there a potentially large difference between the MC training data and real-world conditions but these detector conditions could change over time leading to a shift in model output which could degrade trigger performance. The studies presented explore different techniques to reduce the impact of this effect, using the CMS track finding and vertex trigger algorithms as a test case. The studies compare a baseline retraining and redeployment of the model and episodic training of a model as new data arrives in a continual learning context. The results show that a continually learning algorithm outperforms a simple retrained model when degradation in detector performance is applied to the training data and is a viable option for maintaining performance in an evolving environment such as the High-Luminosity LHC.
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Conference paperBarbone M, Brown C, Gaydadjiev G, et al., 2024,
Embedded continual learning for high-energy physics
, 26th International Conference on Computing in High Energy and Nuclear Physics (CHEP 2023), Publisher: EDP Sciences, ISSN: 2100-014XNeural Networks (NN) are often trained offline on large datasets and deployed on specialised hardware for inference, with a strict separation between training and inference. However, in many realistic applications the training environment differs from the real world, or data arrives in a streaming fashion and is continuously changing. In these scenarios, the ability to continuously train and update NN models is desirable. Continual learning (CL) algorithms allow training of models on a stream of data. CL algorithms are often designed to work in constrained settings, such as limited memory and computational power, or limitations on the ability to store past data (e.g, due to privacy concerns or memory requirements). High-energy physics experiments are developing intelligent detectors, with algorithms running on computer systems located close to the detector to meet the challenges of increased data rates and occupancies. The use of NN algorithms in this context is limited by changing detector conditions, such as degradation over time or failure of an input signal which might cause the NNs to lose accuracy leading, in the worst case to the loss of interesting events. CL has the potential to solve this issue, using large amounts of continuously streaming data to allow the network to recognise changes, and to learn and adapt to detector conditions. It has the potential to outperform traditional NN training techniques as not all possible scenarios can be predicted and modelled in static training data samples. However, NN training is computationally expensive and when combined with the strict timing requirements of embedded processors deployed close to the detector, current state-of-the-art offline approaches cannot be directly applied to the real-time systems. Alternatives to typical backpropagation-based training that can be deployed on FPGAs for real-time data processing are presented, and their computational and accuracy characteristics are discussed in the context of
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Conference paperBarbone M, Gaydadjiev G, Howard A, et al., 2024,
Fast, high-quality pseudo random number generators for heterogeneous computing
, 26th International Conference on Computing in High Energy and Nuclear Physics (CHEP 2023), Publisher: EDP Sciences, ISSN: 2100-014XRandom number generation is key to many applications in a wide variety of disciplines. Depending on the application, the quality of the random numbers from a particular generator can directly impact both computational performance and critically the outcome of the calculation. High-energy physics applications use Monte Carlo simulations and machine learning widely, which both require high-quality random numbers. In recent years, to meet increasing performance requirements, many high-energy physics workloads leverage GPU acceleration. While on a CPU, there exist a wide variety of generators with different performance and quality characteristics, the same cannot be stated for GPU and FPGA accelerators. On GPUs, the most common implementation is provided by cuRAND - an NVIDIA library that is not open source or peer reviewed by the scientific community. The highest-quality generator implemented in cuRAND is a version of the Mersenne Twister. Given the availability of better and faster random number generators, high-energy physics moved away from Mersenne Twister several years ago and nowadays MIXMAX is the standard generator in Geant4 via CLHEP. The MIXMAX original design supports parallel streams with a seeding algorithm that makes it especially suited for GPU and FPGA where extreme parallelism is a key factor. In this study we implement the MIXMAX generator on both architectures and analyze its suitability and applicability for accelerator implementations. We evaluated the results against “Mersenne Twister for a Graphic Processor” (MTGP32) on GPUs which resulted in 5, 13 and 14 times higher throughput when a 240, 17 and 8 sized vector space was used respectively. The MIXMAX generator coded in VHDL and implemented on Xilinx Ultrascale+ FPGAs, requires 50% fewer total Look Up Tables (LUTs) compared to a 32-bit Mersenne Twister (MT-19337), or 75% fewer LUTs per output bit. In summary, the state-of-the art MIXMAX pseudo random number generator has been implemen
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Conference paperOurida T, Luk W, Tapper A, et al., 2024,
Acceleration of a Deep Neural Network for the compact muon solenoid
, 26th International Conference on Computing in High Energy and Nuclear Physics, Publisher: EDP Sciences, ISSN: 2100-014XThere are ongoing efforts to investigate theories that aim to explain the current shortcomings of the Standard Model of particle physics. One such effort is the Long-Lived Particle Jet Tagging Algorithm, based on a DNN (Deep Neural Network), which is used to search for exotic new particles. This paper describes two novel optimisations in the design of this DNN, suitable for implementation on an FPGA-based accelerator. The first involves the adoption of cyclic random access memories and the reuse of multiply-accumulate operations. The second involves storing matrices distributed over many RAM memories with elements grouped by index. An evaluation of the proposed methods and hardware architectures is also included. The proposed optimisations can yield performance enhancements by more than an order of magnitude compared to software implementations. The innovations can also lead to smaller FPGA footprints and accordingly reduce power consumption, allowing for instance duplication of compute units to achieve increases in effective throughput.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Inclusive and diferential cross section measurements of t(t)over-barb(b)over-bar production in the lepton plus jets channel at √s=13 TeV
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for W' bosons decaying to a top and a bottom quark in leptonic final states in proton-proton collisions at √<i>s</i>=13 TeV
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for long-lived particles decaying to final states with a pair of muons in proton-proton collisions at √s=13.6 TeV
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleAaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024,
Study of CP violation in B<SUP>0</SUP> → DK*(892)<SUP>0</SUP> decays with D → Kπ(ππ), ππ(ππ), and KK final states
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleAaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024,
Measurement of the Λ<sub>c</sub><SUP>+</SUP> to D<SUP>0</SUP> production ratio in peripheral PbPb collisions at √s<sub>NN</sub> = 5.02 TeV (vol 2024, 21, 2024)
, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479 -
Journal articleAbe K, Bronner C, Hayato Y, et al., 2024,
Solar neutrino measurements using the full data period of Super-Kamiokande-IV
, PHYSICAL REVIEW D, Vol: 109, ISSN: 2470-0010
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