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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,
The CMS Statistical Analysis and Combination Tool: Combine
, Computing and Software for Big Science, Vol: 8, ISSN: 2510-2036<jats:title>Abstract</jats:title><jats:p>This paper describes the <jats:sc>Combine</jats:sc> 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 <jats:sc>Combine</jats:sc> 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 <jats:sc>Combine</jats:sc>. However, the online documentation referenced within this paper provides an up-to-date and complete user guide.</jats:p>
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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.
, Phys Rev Lett, Vol: 133Searches for pair-produced multijet signatures using data corresponding to an integrated luminosity of 128 fb^{-1} of proton-proton collisions at sqrt[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 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, Vol: 110, ISSN: 2470-0010<jats:p>ProtoDUNE 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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>7</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>GeV</a:mi><a:mo>/</a:mo><a:mi>c</a:mi></a:mrow></a:math> beam momentum settings. The flux-weighted average of the extracted inelastic cross section at each beam momentum setting was measured to be <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mn>380</c:mn><c:mo>±</c:mo><c:mn>26</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:mi>mbarns</c:mi></c:mrow></c:math> for the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mn>6</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:mi>GeV</e:mi><e:mo>/</e:mo><e:mi>c</e:mi></e:mrow></e:math> setting and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mn>379</g:mn><g:mo>±</g:mo><g:mn>35</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:mi>mbarns</g:mi></g:mrow></g:math> for the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:mn>7</i:mn><i:mtext> </i:mtext><i:mtext> &l
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>D</mml:mi><mml:mo>*</mml:mo></mml:msup></mml:math> longitudinal polarization in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mn>0</mml:mn></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo><mml:mo>−</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>τ</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msub><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi>τ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> decays
, Physical Review D, Vol: 110, ISSN: 2470-0010<jats:p>The longitudinal polarization fraction of the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mi>D</a:mi><a:mo>*</a:mo></a:msup></a:math> meson is measured in <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msup><c:mi>B</c:mi><c:mn>0</c:mn></c:msup><c:mo stretchy="false">→</c:mo><c:mrow><c:msup><c:mi>D</c:mi><c:mrow><c:mo>*</c:mo><c:mo>−</c:mo></c:mrow></c:msup><c:msup><c:mi>τ</c:mi><c:mo>+</c:mo></c:msup><c:msub><c:mi>ν</c:mi><c:mi>τ</c:mi></c:msub></c:mrow></c:math> decays, where the <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mi>τ</f:mi></f:math> 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 <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mrow><h:mn>5</h:mn><h:mtext> </h:mtext><h:mtext> </h:mtext><h:msup><h:mrow><h:mi>fb</h:mi></h:mrow><h:mrow><h:mo>−</h:mo><h:mn>1</h:mn></h:mrow></h:msup></h:mrow></h:math>. The <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:msup><j:mi>D</j:mi><j:mo>*</j:mo></j:msup></j:math> polarization fraction <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:msubsup>
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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.
, Phys Rev Lett, Vol: 133The first search for soft unclustered energy patterns (SUEPs) is performed using an integrated luminosity of 138 fb^{-1} of proton-proton collision data at sqrt[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 articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Observation of double Formula Presented meson production in Formula Presented collisions at Formula Presented
, Physical Review D, Vol: 110, ISSN: 2470-0010The first observation of the concurrent production of two Formula Presented mesons in proton-nucleus collisions is presented. The analysis is based on a proton-lead (Formula Presented) 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 Formula Presented. The two Formula Presented mesons are reconstructed in their Formula Presented decay channels with transverse momenta Formula Presented and rapidity Formula Presented. Events where one of the Formula Presented mesons is reconstructed in the dielectron channel are also considered in the search. The Formula Presented process is observed with a significance of 5.3 standard deviations. The measured inclusive fiducial cross section, using the four-muon channel alone, is Formula Presented. A fit of the data to the expected rapidity separation for pairs of Formula Presented mesons produced in single (SPS) and double (DPS) parton scatterings yields Formula Presented and Formula Presented, 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 Formula Presented at 95% confidence level.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Measurement of the polarizations of prompt and non-prompt [Formula presented] and ψ(2S) mesons produced in pp collisions at s=13TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 858, ISSN: 0370-2693The polarizations of prompt and non-prompt [Formula presented] and ψ(2S) mesons are measured in proton-proton collisions at s=13 TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to a total integrated luminosity of 103.3fb−1. Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, λϑ, is measured as a function of the transverse momentum, pT, of the charmonium states, in the 25–120 and 20–100 GeV ranges for the [Formula presented] and ψ(2S), respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for pT≳25GeV, the non-prompt [Formula presented] and ψ(2S) are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse polarizations, even for pT exceeding 30 times the [Formula presented] mass, where λϑ tends to an asymptotic value around 0.3. Taken together with previous measurements, by CMS and LHCb at s=7 TeV, the prompt polarizations show a significant variation with pT, at low pT.
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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 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, Pages: P11021-P11021<jats:title>Abstract</jats:title> <jats:p>The 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× 10<jats:sup>34</jats:sup> cm<jats:sup>-2</jats:sup>s<jats:sup>-1</jats:sup>, twice the initial design value, at √(<jats:italic>s</jats:italic>)=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.</jats:p>
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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 articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for production of a single vectorlike quark decaying to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>t</mml:mi><mml:mi>H</mml:mi></mml:math> or <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>t</mml:mi><mml:mi>Z</mml:mi></mml:math> in the all-hadronic final state in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mi>p</mml:mi></mml:math> 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: 110, ISSN: 2470-0010<jats:p>A search for electroweak production of a single vectorlike <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>T</a:mi></a:math> quark in association with a bottom (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>b</c:mi></c:math>) quark in the all-hadronic decay channel is presented. This search uses proton-proton collision data at <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msqrt><e:mi>s</e:mi></e:msqrt><e:mo>=</e:mo><e:mn>13</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:mi>TeV</e:mi></e:math> collected by the CMS experiment at the CERN LHC during 2016–2018, corresponding to an integrated luminosity of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>138</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:msup><g:mi>fb</g:mi><g:mrow><g:mo>−</g:mo><g:mn>1</g:mn></g:mrow></g:msup></g:math>. The <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>T</i:mi></i:math> quark is assumed to have charge <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mn>2</k:mn><k:mo>/</k:mo><k:mn>3</k:mn></k:math> and decay to a top (<m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>t</m:mi></m:math>) quark and a Higgs (<o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>H</o:mi></o:math>) or <q:math xmlns:q=&
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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 sqrt[s]=13 TeV.
, Phys Rev Lett, Vol: 133The 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 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 sqrt[s]=13 TeV.
, Phys Rev Lett, Vol: 133A 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 sqrt[s]=13 TeV, corresponding to an integrated luminosity of 138 fb^{-1}. Jets are reconstructed with the anti-k_{T} algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity |η^{jet}|<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 N_{ch}^{j}≈100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for |Δη^{*}|>2. For low-N_{ch}^{j} jets, the long-range elliptic anisotropic harmonic, v_{2}^{*}, is observed to decrease with N_{ch}^{j}. This trend is well described by Monte Carlo event generators. However, a rising trend for v_{2}^{*} emerges at N_{ch}^{j}≳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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Journal articleFujii Y, Sasaki R, Chadeau N, et al., 2024,
Particle identification using plastic scintillators in the COMET Phase-I experiment
, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 1067, ISSN: 0168-9002The COMET (COherent Muon to Electron Transition) Phase-I experiment aims to search for muon to electron conversion with a single event sensitivity of O (10−15). In COMET, a Cylindrical Trigger Hodoscope (CTH), consisting of segmented plastic scintillators, provides a primary trigger signal and timing measurement while suppressing backgrounds under the high rate environment. This paper studies the particle identification capability of CTH to suppress one of the serious backgrounds induced by cosmic-rays. We demonstrated that a background suppression factor greater than 10 is achievable with a signal efficiency higher than 90%.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Measurement of the production cross section of a Higgs boson with large transverse momentum in its decays to a pair of τ leptons in proton-proton collisions at s=13TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 857, ISSN: 0370-2693A measurement of the production cross section of a Higgs boson with transverse momentum greater than 250 GeV is presented where the Higgs boson decays to a pair of τ leptons. It is based on proton-proton collision data collected by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb−1. Because of the large transverse momentum of the Higgs boson the τ leptons from its decays are boosted and produced spatially close, with their decay products overlapping. Therefore, a dedicated algorithm was developed to reconstruct and identify them. The observed (expected) significance of the measured signal with respect to the standard model background-only hypothesis is 3.5 (2.2) standard deviations. The product of the production cross section and branching fraction is measured to be 1.64−0.54+0.68 times the standard model expectation. The fiducial differential production cross section is also measured as functions of the Higgs boson and leading jet transverse momenta. This measurement extends the probed large-transverse-momentum region in the ττ final state beyond 600 GeV.
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Journal articleHeidt C, Hanson GG, Coney LR, et al., 2024,
Transverse emittance reduction in muon beams by ionization cooling
, Nature Physics, Vol: 20, Pages: 1558-1563, ISSN: 1745-2473Accelerated muon beams have been considered for the next-generation studies of high-energy lepton–antilepton collisions and neutrino oscillations. However, high-brightness muon beams have not yet been produced. The main challenge for muon acceleration and storage stems from the large phase-space volume occupied by the beam, derived from the production mechanism of muons through the decay of pions. The phase-space volume of the muon beam can be decreased through ionization cooling. Here we show that ionization cooling leads to a reduction in the transverse emittance of muon beams that traverse lithium hydride or liquid hydrogen absorbers in the Muon Ionization Cooling Experiment. Our results represent a substantial advance towards the realization of muon-based facilities that could operate at the energy and intensity frontiers.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Searches for violation of Lorentz invariance in top quark pair production using dilepton events in 13 TeV proton-proton collisions
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 857, ISSN: 0370-2693A search for violation of Lorentz invariance in the production of top quark pairs (tt‾) is presented. The measured normalized differential tt‾ production cross section, as a function of the sidereal time, is examined for potential modulations induced by Lorentz-invariance breaking operators in an effective field theory extension of the standard model (SM). The cross section is measured from collision events collected by the CMS detector at a center-of-mass-energy of 13 TeV, corresponding to an integrated luminosity of 77.8 fb−1, and containing one electron and one muon. The results are found to be compatible with zero, in agreement with the SM, and are used to place upper limits at 68% confidence level on the magnitude of the Lorentz-violating couplings ranging from 1–8×10−3. This is the first precision test of the isotropy in special relativity with top quarks at the LHC, restricting further the bounds on such couplings by up to two orders of magnitude with respect to previous searches conducted at the Tevatron.
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Journal articleTumasyan A, Adam W, Andrejkovic JW, et al., 2024,
K<inf>S</inf><sup>0</sup> and Λ(Λ‾) two-particle femtoscopic correlations in PbPb collisions at s<inf>NN</inf>=5.02TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 857, ISSN: 0370-2693Two-particle correlations are presented for KS0, [Formula presented], and [Formula presented] strange hadrons as a function of relative momentum in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The dataset corresponds to an integrated luminosity of 0.607nb−1 and was collected using the CMS detector at the CERN LHC. These correlations are sensitive to quantum statistics and to final-state interactions between the particles. The source size extracted from the KS0KS0 correlations is found to decrease from 4.6 to 1.6 fm in going from central to peripheral collisions. Strong interaction scattering parameters (i.e., scattering length and effective range) are determined from the [Formula presented] and [Formula presented] (including their charge conjugates) correlations using the Lednický–Lyuboshitz model and are compared to theoretical and other experimental results.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for Higgs boson pair production with one associated vector boson in proton-proton collisions at s = 13 TeV
, Journal of High Energy Physics, Vol: 2024A search for Higgs boson pair (HH) production in association with a vector boson V (W or Z boson) is presented. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb−1. Both hadronic and leptonic decays of V bosons are used. The leptons considered are electrons, muons, and neutrinos. The HH production is searched for in the bb¯bb¯ decay channel. An observed (expected) upper limit at 95% confidence level of VHH production cross section is set at 294 (124) times the standard model prediction. Constraints are also set on the modifiers of the Higgs boson trilinear self-coupling, kλ, assuming k2V = 1, and vice versa on the coupling of two Higgs bosons with two vector bosons, k2V. The observed (expected) 95% confidence intervals of these coupling modifiers are −37.7 < kλ < 37.2 (−30.1 < kλ < 28.9) and −12.2 < k2V < 13.5 (−7.2 < k2V < 8.9), respectively.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
Observation of muonic Dalitz decays of chib mesons and precise spectroscopy of hidden-beauty states
, Journal of High Energy Physics, Vol: 2024The decays of the χb1(1P), χb2(1P), χb1(2P) and χb2(2P) mesons into the Υ(1S)μ+μ− final state are observed with a high significance using proton-proton collision data collected with the LHCb detector and corresponding to an integrated luminosity of 9 fb−1. The newly observed decays together with the Υ(2S) → Υ(1S)π+π− and Υ(3S) → Υ(2S)π+π− decay modes are used for precision measurements of the mass and mass splittings for the hidden-beauty states.
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Journal articleZhang C, Zennamo J, Zamorano B, et al., 2024,
Scintillation light in SBND: simulation, reconstruction, and expected performance of the photon detection system
, European Physical Journal C, Vol: 84, ISSN: 1434-6044SBND is the near detector of the Short-Baseline Neutrino program at Fermilab. Its location near to the Booster Neutrino Beam source and relatively large mass will allow the study of neutrino interactions on argon with unprecedented statistics. This paper describes the expected performance of the SBND photon detection system, using a simulated sample of beam neutrinos and cosmogenic particles. Its design is a dual readout concept combining a system of 120 photomultiplier tubes, used for triggering, with a system of 192 X-ARAPUCA devices, located behind the anode wire planes. Furthermore, covering the cathode plane with highly-reflective panels coated with a wavelength-shifting compound recovers part of the light emitted towards the cathode, where no optical detectors exist. We show how this new design provides a high light yield and a more uniform detection efficiency, an excellent timing resolution and an independent 3D-position reconstruction using only the scintillation light. Finally, the whole reconstruction chain is applied to recover the temporal structure of the beam spill, which is resolved with a resolution on the order of nanoseconds.
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Journal articleMori M, Abe K, Hayato Y, et al., 2024,
Development of a Data Overflow Protection System for Super-Kamiokande to Maximize Data from Nearby Supernovae
, Progress of Theoretical and Experimental Physics, Vol: 2024Neutrinos from very nearby supernovae, such as Betelgeuse, are expected to generate more than ten million events over 10 s in Super-Kamokande (SK). At such large event rates, the buffers of the SK analog-to-digital conversion board (QBEE) will overflow, causing random loss of data that are critical for understanding the dynamics of the supernova explosion mechanism. In order to solve this problem, two new data-acquisition (DAQ) modules were developed to aid in the observation of very nearby supernovae. The first of these, the SN module, is designed to save only the number of hit photomultiplier tubes during a supernova burst and the second, the Veto module, prescales the high-rate neutrino events to prevent the QBEE from overflowing based on information from the SN module. In the event of a very nearby supernova, these modules allow SK to reconstruct the time evolution of the neutrino event rate from beginning to end using both QBEE and SN module data. This paper presents the development and testing of these modules together with an analysis of supernova-like data generated with a flashing laser diode. We demonstrate that the Veto module successfully prevents DAQ overflows for Betelgeuse-like supernovae as well as the long-term stability of the new modules. During normal running the Veto module is found to issue DAQ vetos a few times per month resulting in a total dead-time less than 1 ms, and does not influence ordinary operations. Additionally, using simulation data we find that supernovae closer than 800 pc will trigger the Veto module, resulting in a prescaling of the observed neutrino data.
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