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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for bottom quark associated production of the standard model Higgs boson in final states with leptons in proton-proton collisions at s=13TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 860, ISSN: 0370-2693This Letter presents the first search for bottom quark associated production of the standard model Higgs boson, in final states with leptons. Higgs boson decays to pairs of tau leptons and pairs of leptonically decaying W bosons are considered. The search is performed using data collected from 2016 to 2018 by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138fb−1. Upper limits at the 95% confidence level are placed on the signal strength for Higgs boson production in association with bottom quarks; the observed (expected) upper limit is 3.7 (6.1) times the standard model prediction.
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Journal articleMazumdar D, Das K, Das I, 2024,
Magnetic exchange coupled composite behavior in the doped manganite nanoparticles: A proposed phenomenological model
, Physica B: Condensed Matter, Vol: 695, ISSN: 0921-4526In this paper, we comprehensively investigate the isothermal magnetization behavior of doped perovskite manganite nanoparticles. The focus is on understanding the impact of variation of particle sizes on the soft and hard magnetic phases with respect to the changes in the coercive field and remanent magnetization, both theoretically and experimentally. The study seeks to correlate experimental findings with the proposed phenomenological model to gain deeper insights into the underlying mechanisms governing exchange coupling and anisotropy effects in the nanocrystalline composites. The proposed phenomenological model beautifully demonstrates how the values of saturation magnetization and coercive field changes with changing the particle size in the nanocrystalline La0.48Ca0.52MnO3 (LCMO48) and La0.46Ca0.54MnO3 (LCMO46) compounds. In addition, the model provide an insights into the limitations of critical radius, size and shape of the nanocrystalline particle. This investigation looks into how the size of particles affects their magnetic properties, specifically coercive field and remanent magnetization.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for CP violation in $${{{\textrm{D}}}^{{0}}} \rightarrow {{\textrm{K}} _{\text {S}}^{{0}}} {{\textrm{K}} _{\text {S}}^{{0}}} $$ decays in proton–proton collisions at $$\sqrt{s} = 13\,\text {Te}\hspace{-.08em}\text {V} $$
, The European Physical Journal C, Vol: 84<jats:title>Abstract</jats:title><jats:p>A search is reported for charge-parity <jats:inline-formula><jats:alternatives><jats:tex-math>$$CP$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>CP</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> violation in <jats:inline-formula><jats:alternatives><jats:tex-math>$${{{\textrm{D}}}^{{0}}} \rightarrow {{\textrm{K}} _{\text {S}}^{{0}}} {{\textrm{K}} _{\text {S}}^{{0}}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mtext>D</mml:mtext> </mml:mrow> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mtext>K</mml:mtext> <mml:mrow> <mml:mtext>S</mml:mtext> </mml:mrow> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msubsup> <mml:mtext>K</mml:mtext> <mml:mrow> <mml:mtext>S</mml:mtext> </mml:mrow> <mml:mn>0</mml:mn> </mml:msubsup> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> decays, using data collected in proton–proton collisions at <jats:inline-formula><jats:alte
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Measurement of boosted Higgs bosons produced via vector boson fusion or gluon fusion in the H → $$ \textrm{b}\overline{\textrm{b}} $$ decay mode using LHC proton-proton collision data at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2024<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A measurement is performed of Higgs bosons produced with high transverse momentum (<jats:italic>p</jats:italic><jats:sub>T</jats:sub>) via vector boson or gluon fusion in proton-proton collisions. The result is based on a data set with a center-of-mass energy of 13 TeV collected in 2016–2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. The decay of a high-<jats:italic>p</jats:italic><jats:sub>T</jats:sub> Higgs boson to a boosted bottom quark-antiquark pair is selected using large-radius jets and employing jet substructure and heavy-flavor taggers based on machine learning techniques. Independent regions targeting the vector boson and gluon fusion mechanisms are defined based on the topology of two quark-initiated jets with large pseudorapidity separation. The signal strengths for both processes are extracted simultaneously by performing a maximum likelihood fit to data in the large-radius jet mass distribution. The observed signal strengths relative to the standard model expectation are <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {4.9}_{-1.6}^{+1.9} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mn>4.9</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.9</mml:mn> </mml:mrow> </mml:msubsup> </mml:
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Journal articleAbbaneo D, Ahmad S, Albanese R, et al., 2024,
An integrated flux-symmetric spectrometer-magnet system for the SND@LHC experiment upgrade
, Journal of Instrumentation, Vol: 19The proposed upgrade of the SND@LHC experiment for the High Luminosity phase of the LHC (HL-LHC) will strongly benefit from the presence of a magnetized region, allowing for muon momentum and charge measurement. In this paper we describe an iron core magnet system that is partly integrated with the calorimeter and that is designed to respect the strict constraints from the available space in the experimental cavern, power consumption, and field requirements. Semi-analytical tools are introduced to explore the parameter space, in order to define the primary design options. A full 3-D analysis is then performed in order to validate the optimal choice, and to propose a conceptual design, including sizing of the components, detector performances and stray fields. Several technical options are also discussed, anticipating the design phase.
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Journal articleAbed Abud A, Abi B, Acciarri R, et al., 2024,
DUNE Phase II: scientific opportunities, detector concepts, technological solutions
, Journal of Instrumentation, Vol: 19, Pages: P12005-P12005<jats:title>Abstract</jats:title> <jats:p>The international collaboration designing and constructing the Deep Underground Neutrino Experiment (DUNE) at the Long-Baseline Neutrino Facility (LBNF) has developed a two-phase strategy toward the implementation of this leading-edge, large-scale science project. The 2023 report of the US Particle Physics Project Prioritization Panel (P5) reaffirmed this vision and strongly endorsed DUNE Phase I and Phase II, as did the European Strategy for Particle Physics. While the construction of the DUNE Phase I is well underway, this White Paper focuses on DUNE Phase II planning. DUNE Phase-II consists of a third and fourth far detector (FD) module, an upgraded near detector complex, and an enhanced 2.1 MW beam. The fourth FD module is conceived as a “Module of Opportunity”, aimed at expanding the physics opportunities, in addition to supporting the core DUNE science program, with more advanced technologies. This document highlights the increased science opportunities offered by the DUNE Phase II near and far detectors, including long-baseline neutrino oscillation physics, neutrino astrophysics, and physics beyond the standard model. It describes the DUNE Phase II near and far detector technologies and detector design concepts that are currently under consideration. A summary of key R&D goals and prototyping phases needed to realize the Phase II detector technical designs is also provided. DUNE's Phase II detectors, along with the increased beam power, will complete the full scope of DUNE, enabling a multi-decadal program of groundbreaking science with neutrinos.</jats:p>
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
The CMS statistical analysis and combination tool: COMBINE
, Computing and Software for Big Science, Vol: 8, ISSN: 2510-2036This paper describes the Combine software package used for statistical analyses by the CMS Collaboration. The package, originally designed to perform searches for a Higgs boson and the combined analysis of those searches, has evolved to become the statistical analysis tool presently used in the majority of measurements and searches performed by the CMS Collaboration. It is not specific to the CMS experiment, and this paper is intended to serve as a reference for users outside of the CMS Collaboration, providing an outline of the most salient features and capabilities. Readers are provided with the possibility to run Combine and reproduce examples provided in this paper using a publicly available container image. Since the package is constantly evolving to meet the demands of ever-increasing data sets and analysis sophistication, this paper cannot cover all details of Combine. However, the online documentation referenced within this paper provides an up-to-date and complete user guide.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Portable acceleration of CMS computing workflows with coprocessors as a service
, Computing and Software for Big Science, Vol: 8, ISSN: 2510-2036Computing demands for large scientific experiments, such as the CMS experiment at the CERN LHC, will increase dramatically in the next decades. To complement the future performance increases of software running on central processing units (CPUs), explorations of coprocessor usage in data processing hold great potential and interest. Coprocessors are a class of computer processors that supplement CPUs, often improving the execution of certain functions due to architectural design choices. We explore the approach of Services for Optimized Network Inference on Coprocessors (SONIC) and study the deployment of this as-a-service approach in large-scale data processing. In the studies, we take a data processing workflow of the CMS experiment and run the main workflow on CPUs, while offloading several machine learning (ML) inference tasks onto either remote or local coprocessors, specifically graphics processing units (GPUs). With experiments performed at Google Cloud, the Purdue Tier-2 computing center, and combinations of the two, we demonstrate the acceleration of these ML algorithms individually on coprocessors and the corresponding throughput improvement for the entire workflow. This approach can be easily generalized to different types of coprocessors and deployed on local CPUs without decreasing the throughput performance. We emphasize that the SONIC approach enables high coprocessor usage and enables the portability to run workflows on different types of coprocessors.
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Journal articleAalbers J, Akerib DS, Al Musalhi AK, et al., 2024,
Constraints on Covariant Dark-Matter-Nucleon Effective Field Theory Interactions from the First Science Run of the LUX-ZEPLIN Experiment.
, Phys Rev Lett, Vol: 133The LUX-ZEPLIN (LZ) experiment is a dual-phase xenon time project chamber operating in the Sanford Underground Research Facility in South Dakota, USA. We report on the results of a relativistic extension to the nonrelativistic effective field theory (NREFT) from a 5.5 t fiducial mass and 60 live days of exposure. We present constraints on couplings from covariant interactions arising from the coupling of vector, axial currents, and electric dipole moments of the nucleon to the magnetic and electric dipole moments of the weakly interacting massive particle which cannot be described by recasting previous results described by an NREFT. Using a profile-likelihood ratio analysis, in an energy region between 0 keV_{nr} to 270 keV_{nr}, we report 90% confidence level exclusion limits on the coupling strength of five interactions in both the isoscalar and isovector bases.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Searches for pair-produced multijet resonances using data scouting in proton-proton collisions at sqrt[s]=13 TeV
, Physical Review Letters, Vol: 133, ISSN: 0031-9007Searches for pair-produced multijet signatures using data corresponding to an integrated luminosity of 128 fb−1 of proton-proton collisions at √𝑠=13 TeV are presented. A data scouting technique is employed to record events with low jet scalar transverse momentum sum values. The electroweak production of particles predicted in 𝑅-parity violating supersymmetric models is probed for the first time with fully hadronic final states. This is the first search for prompt hadronically decaying mass-degenerate higgsinos, and extends current exclusions on 𝑅-parity violating top squarks and gluinos.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for soft unclustered energy patterns in proton-proton collisions at 13 TeV
, Physical Review Letters, Vol: 133, ISSN: 0031-9007The first search for soft unclustered energy patterns (SUEPs) is performed using an integrated luminosity of 138 fb−1 of proton-proton collision data at √𝑠=13 TeV, collected in 2016–2018 by the CMS detector at the LHC. Such SUEPs are predicted by hidden valley models with a new, confining force with a large ’t Hooft coupling. In events with boosted topologies, selected by high-threshold hadronic triggers, the multiplicity and sphericity of clustered tracks are used to reject the background from standard model quantum chromodynamics. With no observed excess of events over the standard model expectation, limits are set on the cross section for production via gluon fusion of a scalar mediator with SUEP-like decays.
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Journal articleAbud AA, Abi B, Acciarri R, et al., 2024,
First measurement of the total inelastic cross section of positively charged kaons on argon at energies between 5.0 and 7.5 GeV
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 110, ISSN: 1550-2368ProtoDUNE Single-Phase (ProtoDUNE-SP) is a 770-ton liquid argon time projection chamber that operated in a hadron test beam at the CERN Neutrino Platform in 2018. We present a measurement of the total inelastic cross section of charged kaons on argon as a function of kaon energy using 6 and 7 GeV/𝑐 beam momentum settings. The flux-weighted average of the extracted inelastic cross section at each beam momentum setting was measured to be 380±26 mbarns for the 6 GeV/𝑐 setting and 379±35 mbarns for the 7 GeV/𝑐 setting.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Observation of double J/ψ meson production inpPb collisions at √sNN = 8.16 TeV
, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 110, ISSN: 1550-2368The first observation of the concurrent production of two 𝐽/𝜓 mesons in proton-nucleus collisions is presented. The analysis is based on a proton-lead (𝑝Pb) data sample recorded at a nucleon-nucleon center-of-mass energy of 8.16 TeV by the CMS experiment at the CERN LHC and corresponding to an integrated luminosity of 174.6 nb−1. The two 𝐽/𝜓 mesons are reconstructed in their 𝜇+𝜇− decay channels with transverse momenta 𝑝T >6.5 GeV and rapidity |𝑦| <2.4. Events where one of the 𝐽/𝜓 mesons is reconstructed in the dielectron channel are also considered in the search. The 𝑝Pb →𝐽/𝜓𝐽/𝜓+𝑋 process is observed with a significance of 5.3 standard deviations. The measured inclusive fiducial cross section, using the four-muon channel alone, is 𝜎(𝑝Pb →𝐽/𝜓𝐽/𝜓 +𝑋) = 22.0 ±8.9(stat) ±1.5(syst) nb. A fit of the data to the expected rapidity separation for pairs of 𝐽/𝜓 mesons produced in single (SPS) and double (DPS) parton scatterings yields 𝜎𝑝Pb→𝐽/𝜓𝐽/𝜓+𝑋SPS=16.5±10.8(stat)±0.1(syst) nb and 𝜎𝑝Pb→𝐽/𝜓𝐽/𝜓+𝑋DPS =5.4 ±6.2(stat) ±0.4(syst) nb, respectively. This latter result can be transformed into a lower bound on the effective DPS cross section, closely related to the squared average interparton transverse separation in the collision, of 𝜎eff >1.0 mb at 95% confidence level.
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Journal articleBeteta A, Aaij R, Abdelmotteleb ASW, et al., 2024,
Measurement of the D<sup>*</sup> longitudinal polarization in B0 →d<sup>*-</sup>τ<sup>+</sup>ν<inf>τ</inf> decays
, Physical Review D, Vol: 110, ISSN: 2470-0010The longitudinal polarization fraction of the D* meson is measured in B0→D*-τ+ντ decays, where the τ lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of 5 fb-1. The D* polarization fraction FLD* is measured in two q2 regions, below and above 7 GeV2/c4, where q2 is defined as the squared invariant mass of the τντ system. The FLD∗ values are measured to be 0.52±0.07±0.04 and 0.34±0.08±0.02 for the lower and higher q2 regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole q2 range is FLD∗=0.41±0.06±0.03. These results are compatible with the Standard Model predictions.
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Journal articleCMS Collaboration T, 2024,
Observation of quantum entanglement in top quark pair production in proton–proton collisions at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>13</mml:mn></mml:mrow></mml:math> TeV
, Reports on Progress in Physics, Vol: 87, Pages: 117801-117801, ISSN: 0034-4885<jats:title>Abstract</jats:title><jats:p>Entanglement is an intrinsic property of quantum mechanics and is predicted to be exhibited in the particles produced at the Large Hadron Collider. A measurement of the extent of entanglement in top quark-antiquark (<jats:inline-formula><jats:tex-math/><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mrow><mml:mrow><mml:mi mathvariant="normal">t</mml:mi></mml:mrow><mml:mrow><mml:mover><mml:mrow><mml:mi mathvariant="normal">t</mml:mi></mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mover></mml:mrow></mml:mrow></mml:math></jats:inline-formula>) events produced in proton–proton collisions at a center-of-mass energy of 13 TeV is performed with the data recorded by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 36.3 fb<jats:sup>−1</jats:sup>. The events are selected based on the presence of two leptons with opposite charges and high transverse momentum. An entanglement-sensitive observable<jats:italic>D</jats:italic>is derived from the top quark spin-dependent parts of the<jats:inline-formula><jats:tex-math/><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mrow><mml:mrow><mml:mi mathvariant="normal">t</mml:mi></mml:mrow><mml:mrow><mml:mover><mml:mrow><mml:mi mathvariant="normal">t</mml:mi></mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mover></mml:mrow></mml:mrow></mml:math></jats:inline-formula>production density matrix and measured in the region of the<jats:inline-formula><jats:tex-mat
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Journal articleAbratenko P, Alterkait O, Andrade Aldana D, et al., 2024,
Improving neutrino energy estimation of charged-current interaction events with recurrent neural networks in MicroBooNE
, Physical Review D, Vol: 110, ISSN: 2470-0010We present a deep learning-based method for estimating the neutrino energy of charged-current neutrino-argon interactions. We employ a recurrent neural network (RNN) architecture for neutrino energy estimation in the MicroBooNE experiment, utilizing liquid argon time projection chamber (LArTPC) detector technology. Traditional energy estimation approaches in LArTPCs, which largely rely on reconstructing and summing visible energies, often experience sizable biases and resolution smearing because of the complex nature of neutrino interactions and the detector response. The estimation of neutrino energy can be improved after considering the kinematics information of reconstructed final-state particles. Utilizing kinematic information of reconstructed particles, the deep learning-based approach shows improved resolution and reduced bias for the muon neutrino Monte Carlo simulation sample compared to the traditional approach. In order to address the common concern about the effectiveness of this method on experimental data, the RNN-based energy estimator is further examined and validated with dedicated data-simulation consistency tests using MicroBooNE data. We also assess its potential impact on a neutrino oscillation study after accounting for all statistical and systematic uncertainties and show that it enhances physics sensitivity. This method has good potential to improve the performance of other physics analyses.
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Journal articleAalbers J, Akerib DS, Al Musalhi AK, et al., 2024,
The data acquisition system of the LZ dark matter detector: FADR
, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 1068, ISSN: 0168-9002The Data Acquisition System (DAQ) for the LUX-ZEPLIN (LZ) dark matter detector is described. The signals from 745 PMTs, distributed across three subsystems, are sampled with 100-MHz 32-channel digitizers (DDC-32s). A basic waveform analysis is carried out on the on-board Field Programmable Gate Arrays (FPGAs) to extract information about the observed scintillation and electroluminescence signals. This information is used to determine if the digitized waveforms should be preserved for offline analysis. The system is designed around the Kintex-7 FPGA. In addition to digitizing the PMT signals and providing basic event selection in real time, the flexibility provided by the use of FPGAs allows us to monitor the performance of the detector and the DAQ in parallel to normal data acquisition. The hardware and software/firmware of this FPGA-based Architecture for Data acquisition and Realtime monitoring (FADR) are discussed and performance measurements are described.
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Journal articleAamir M, Adamov G, Adams T, et al., 2024,
Using graph neural networks to reconstruct charged pion showers in the CMS High Granularity Calorimeter
, Journal of Instrumentation, Vol: 19A novel method to reconstruct the energy of hadronic showers in the CMS High Granularity Calorimeter (HGCAL) is presented. The HGCAL is a sampling calorimeter with very fine transverse and longitudinal granularity. The active media are silicon sensors and scintillator tiles readout by SiPMs and the absorbers are a combination of lead and Cu/CuW in the electromagnetic section, and steel in the hadronic section. The shower reconstruction method is based on graph neural networks and it makes use of a dynamic reduction network architecture. It is shown that the algorithm is able to capture and mitigate the main effects that normally hinder the reconstruction of hadronic showers using classical reconstruction methods, by compensating for fluctuations in the multiplicity, energy, and spatial distributions of the shower's constituents. The performance of the algorithm is evaluated using test beam data collected in 2018 prototype of the CMS HGCAL accompanied by a section of the CALICE AHCAL prototype. The capability of the method to mitigate the impact of energy leakage from the calorimeter is also demonstrated.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Measurement of the polarizations of prompt and non-prompt J/ψ and ψ(2S) mesons produced in pp collisions at √𝑠 = 13TeV
, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 858, ISSN: 0370-2693The polarizations of prompt and non-prompt J∕ψ and ψ(2S) mesons are measured in proton-proton collisionsat √𝑠 = 13TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to atotal integrated luminosity of 103.3 fb−1. Based on the analysis of the dimuon decay angular distributions inthe helicity frame, the polar anisotropy, 𝜆𝜗, is measured as a function of the transverse momentum, 𝑝T, of thecharmonium states, in the 25–120 and 20–100 GeV ranges for the J∕ψ and ψ(2S), respectively. The non-promptpolarizations agree with predictions based on the hypothesis that, for 𝑝T ≳ 25GeV, the non-prompt J∕ψ and ψ(2S)are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transversepolarizations, even for 𝑝T exceeding 30 times the J∕ψ mass, where 𝜆𝜗 tends to an asymptotic value around 0.3.Taken together with previous measurements, by CMS and LHCb at √𝑠 = 7TeV, the prompt polarizations show asignificant variation with 𝑝T, at low 𝑝T.
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Journal articleAnfimov N, Branca A, Bürgi J, et al., 2024,
First demonstration of a combined light and charge pixel readout on the anode plane of a LArTPC
, Journal of Instrumentation, Vol: 19, ISSN: 1748-0221The novel SoLAr concept aims to extend sensitivities of liquid-argon neutrino detectors down to the MeV scale for next-generation detectors. SoLAr plans to accomplish this with a liquid-argon time projection chamber that employs an anode plane with dual charge and light readout, which enables precision matching of light and charge signals for data acquisition and reconstruction purposes. We present the results of a first demonstration of the SoLAr detector concept with a small-scale prototype detector integrating a pixel-based charge readout and silicon photomultipliers on a shared printed circuit board. We discuss the design of the prototype, and its operation and performance, highlighting the capability of such a detector design.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Performance of the CMS high-level trigger during LHC Run 2
, Journal of Instrumentation, Vol: 19, ISSN: 1748-0221The CERN LHC provided proton and heavy ion collisions during its Run 2 operation period from 2015 to 2018. Proton-proton collisions reached a peak instantaneous luminosity of 2.1× 1034 cm-2s-1, twice the initial design value, at √(s)=13 TeV. The CMS experiment records a subset of the collisions for further processing as part of its online selection of data for physics analyses, using a two-level trigger system: the Level-1 trigger, implemented in custom-designed electronics, and the high-level trigger, a streamlined version of the offline reconstruction software running on a large computer farm. This paper presents the performance of the CMS high-level trigger system during LHC Run 2 for physics objects, such as leptons, jets, and missing transverse momentum, which meet the broad needs of the CMS physics program and the challenge of the evolving LHC and detector conditions. Sophisticated algorithms that were originally used in offline reconstruction were deployed online. Highlights include a machine-learning b tagging algorithm and a reconstruction algorithm for tau leptons that decay hadronically.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for the 𝑍 boson decay to 𝜏𝜏𝜇𝜇 in proton-proton collisions at √𝑠=13 TeV
, Physical Review Letters, Vol: 133, ISSN: 0031-9007The first search for the 𝑍 boson decay to 𝜏𝜏𝜇𝜇 at the CERN LHC is presented, based on data collected by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb−1. The data are compatible with the predicted background. For the first time, an upper limit at the 95% confidence level of 6.9 times the standard model expectation is placed on the ratio of the 𝑍 →𝜏𝜏𝜇𝜇 to 𝑍 →4𝜇 branching fractions. Limits are also placed on the six flavor-conserving four-lepton effective-field-theory operators involving two muons and two tau leptons, for the first time testing all such operators.
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Conference paperKitagawa H, Tada T, Abe K, et al., 2024,
Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector
, ISSN: 2470-0010We present the results of the charge ratio (R) and polarization (P0μ) measurements using decay electron events collected between September 2008 and June 2022 with the Super-Kamiokande detector. Because of its underground location and long operation, we are able to perform high-precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be R=1.32±0.02(stat+syst) at EμcosθZenith=0.7-0.2+0.3 TeV, where Eμ is the muon energy and θZenith is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while indicating a tension with the πK model of 1.9σ. We also measured the muon polarization at the production location to be P0μ=0.52±0.02 (stat+syst) at the muon momentum of 0.9-0.1+0.6 TeV/c at the surface of the mountain; this also suggests a tension with the Honda flux model of 1.5σ. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near 1 TeV/c. These measurement results are useful to improve atmospheric neutrino simulations.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Observation of the Λ b 0 → J / ψ Ξ - K + decay
, European Physical Journal C: Particles and Fields, Vol: 84, ISSN: 1124-1861<jats:title>Abstract</jats:title><jats:p>Using proton–proton collision data corresponding to an integrated luminosity of <jats:inline-formula><jats:alternatives><jats:tex-math>$$140\hbox { fb}^{-1}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>140</mml:mn> <mml:mspace/> <mml:msup> <mml:mtext>fb</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> collected by the CMS experiment at <jats:inline-formula><jats:alternatives><jats:tex-math>$$\sqrt{s}= 13\,\text {Te}\hspace{-.08em}\text {V} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mspace/> <mml:mtext>Te</mml:mtext> <mml:mspace/> <mml:mtext>V</mml:mtext> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, the <jats:inline-formula><jats:alternatives><jats:tex-math>$${{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{\text {J}/\uppsi }} {{{\Xi }} ^{{-}}} {{\text {K}} ^{{+}}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math
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Journal articleChatterjee S, Halder S, Das K, et al., 2024,
Magnetization reversal in nanocrystalline Gd0.5Sr0.5MnO3
, Physical Review B, Vol: 110, ISSN: 2469-9950Negative magnetization phenomenon is an unusual magnetic behavior where magnetic ordering temperature of two or more types of constituent magnetic moments are believed to be different. This magnetization crossover from positive to negative at low temperatures has triggered interest due to its futuristic potential applications in spintronics. In the present article, our experimental and theoretical results manifest the magnetization reversal in nanocrystalline Gd0.5Sr0.5MnO3 compounds, while this intrinsic effect of negative magnetization is absent in the bulk form. We argue that the antiferromagnetic interactions between Gd sublattice and Mn sublattices increases with decreasing particle size of the Gd0.5Sr0.5MnO3 compound as we go from bulk to nanocrystalline compounds and hence exhibits the negative magnetization in nanocrystalline compounds at low temperatures. We implement Monte Carlo simulation based on classical Heisenberg model supplemented by magnetocrystalline anisotropy to emphasize the key role of this antiferromagnetic interaction among Gd and Mn sublattices by systematically studying negative magnetization.
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Journal articleHori M, 2024,
Status of laser spectroscopy measurements of long-lived antiprotonic and pionic helium atoms at CERN and PSI
, International Journal of Modern Physics A, Vol: 39, ISSN: 0217-751XThe results of laser spectroscopy experiments of antiprotonic helium atoms carried out at the Antiproton Decelerator of CERN, and pionic helium atoms measured at the 590MeV ring cyclotron facility of the Paul Scherrer Institute are reviewed. The former experiment determined the antiproton-to-electron mass ratio as Mp¯/me=1836.1526734(15). In the latter, a resonant transition (n,ℓ)=(17,16)→(17,15) of pionic helium at a frequency of ν≈183760GHz was detected. Some future perspectives are briefly described.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Observation of enhanced long-range elliptic anisotropies inside high-multiplicity jets in pp collisions at √s = 13 TeV
, Physical Review Letters, Vol: 133, ISSN: 0031-9007A search for collective effects inside jets produced in proton-proton collisions is performed via correlation measurements of charged particles using the CMS detector at the CERN LHC. The analysis uses data collected at a center-of-mass energy of √𝑠 =13 TeV, corresponding to an integrated luminosity of 138 fb−1. Jets are reconstructed with the anti-𝑘T algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity |𝜂jet|<1.6. Two-particle correlations among the charged particles within the jets are studied as functions of the particles’ azimuthal angle and pseudorapidity separations (Δ𝜙* and Δ𝜂*) in a jet coordinate basis, where particles’ 𝜂*, 𝜙* are defined relative to the direction of the jet. The correlation functions are studied in classes of in-jet charged-particle multiplicity up to 𝑁jch ≈100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for |Δ𝜂*| >2. For low-𝑁jch jets, the long-range elliptic anisotropic harmonic, 𝑣*2, is observed to decrease with 𝑁jch. This trend is well described by Monte Carlo event generators. However, a rising trend for 𝑣*2 emerges at 𝑁jch ≳80, hinting at a possible onset of collective behavior, which is not reproduced by the models tested. This observation yields new insights into the dynamics of jet evolution in the vacuum.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
Precision measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi mathvariant="normal">Ξ</mml:mi><mml:mi>b</mml:mi><mml:mo>−</mml:mo></mml:msubsup></mml:math> baryon lifetime
, Physical Review D, Vol: 110, ISSN: 2470-0010<jats:p>A sample of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>p</a:mi><a:mi>p</a:mi></a:math> collision data, corresponding to an integrated luminosity of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mn>5.5</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:msup><c:mi>fb</c:mi><c:mrow><c:mo>−</c:mo><c:mn>1</c:mn></c:mrow></c:msup></c:math> and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msubsup><e:mi mathvariant="normal">Ξ</e:mi><e:mi>b</e:mi><e:mo>−</e:mo></e:msubsup></e:math> baryon to that of the <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:msubsup><h:mi mathvariant="normal">Λ</h:mi><h:mi>b</h:mi><h:mn>0</h:mn></h:msubsup></h:math> baryon, <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>r</k:mi><k:mi>τ</k:mi></k:msub><k:mo>≡</k:mo><k:msub><k:mi>τ</k:mi><k:msubsup><k:mi mathvariant="normal">Ξ</k:mi><k:mi>b</k:mi><k:mo>−</k:mo></k:msubsup></k:msub><k:mo>/</k:mo><k:msub><k:mi>τ</k:mi><k:msubsup><k:mi mathvariant="normal">Λ</k:mi><k:mi>b</k:mi><k:mn>0</k:mn></k:msubsup></k:msub></k:math>. The value <o:math xmlns:o="http://www
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Measurement of differential ZZ + jets production cross sections in pp collisions at s = 13 TeV
, Journal of High Energy Physics, Vol: 2024Diboson production in association with jets is studied in the fully leptonic final states, pp → (Z/γ*)(Z/γ*) + jets → 2ℓ2ℓ′ + jets, (ℓ, ℓ′ = e or μ) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb−1 collected with the CMS detector at the LHC. Differential distributions and normalized differential cross sections are measured as a function of jet multiplicity, transverse momentum pT, pseudorapidity η, invariant mass and ∆η of the highest-pT and second-highest-pT jets, and as a function of invariant mass of the four-lepton system for events with various jet multiplicities. These differential cross sections are compared with theoretical predictions that mostly agree with the experimental data. However, in a few regions we observe discrepancies between the predicted and measured values. Further improvement of the predictions is required to describe the ZZ+jets production in the whole phase space.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Measurement of the Bs0→J/ψKS0 effective lifetime from proton-proton collisions at s = 13 TeV
, Journal of High Energy Physics, Vol: 2024The effective lifetime of the Bs0 meson in the decay Bs0→J/ψKS0 is measured using data collected during 2016–2018 with the CMS detector in s = 13 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 140 fb−1. The effective lifetime is determined by performing a two-dimensional unbinned maximum likelihood fit to the Bs0 meson invariant mass and proper decay time distributions. The resulting value of 1.59 ± 0.07(stat) ± 0.03(syst) ps is the most precise measurement to date and is in good agreement with the expected value.
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