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Journal articleAaij R, Abdelmotteleb ASW, Beteta CA, et al., 2024,
Tracking of charged particles with nanosecond lifetimes at LHCb
, European Physical Journal C, Vol: 84, ISSN: 1434-6044A method is presented to reconstruct charged particles with lifetimes between 10ps and 10ns, which considers a combination of their decay products and the partial tracks created by the initial charged particle. Using the Ξ- baryon as a benchmark, the method is demonstrated with simulated events and proton-proton collision data at s=13TeV, corresponding to an integrated luminosity of 2.0fb-1 collected with the LHCb detector in 2018. Significant improvements in the angular resolution and the signal purity are obtained. The method is implemented as part of the LHCb Run 3 event trigger in a set of requirements to select detached hyperons. This is the first demonstration of the applicability of this approach at the LHC, and the first to show its scaling with instantaneous luminosity.
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Journal articleAbratenko P, Alterkait O, Andrade Aldana D, et al., 2024,
Inclusive cross section measurements in final states with and without protons for charged-current νμ -Ar scattering in MicroBooNE
, Physical Review D, Vol: 110, ISSN: 2470-0010A detailed understanding of inclusive muon neutrino charged-current interactions on argon is crucial to the study of neutrino oscillations in current and future experiments using liquid argon time projection chambers. To that end, we report a comprehensive set of differential cross section measurements for this channel that simultaneously probe the leptonic and hadronic systems by dividing the channel into final states with and without protons. Measurements of the proton kinematics and proton multiplicity of the final state are also presented. For these measurements, we utilize data collected with the MicroBooNE detector from 6.4×1020 protons on target from the Fermilab booster neutrino beam at a mean neutrino energy of approximately 0.8 GeV. We present in detail the cross section extraction procedure, including the unfolding, and model validation that uses data to model comparisons and the conditional constraint formalism to detect mismodeling that may introduce biases to extracted cross sections that are larger than their uncertainties. The validation exposes insufficiencies in the overall model, motivating the inclusion of an additional data-driven reweighting systematic to ensure the accuracy of the unfolding. The extracted results are compared to a number of event generators and their performance is discussed with a focus on the regions of phase space that indicate the greatest need for modeling improvements.
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Journal articleAbratenko P, Alterkait O, Andrade Aldana D, et al., 2024,
First application of a liquid argon time projection chamber for the search for intranuclear neutron-antineutron transitions and annihilation in <sup>40</sup>Ar using the MicroBooNE detector
, Journal of Instrumentation, Vol: 19We present a novel methodology to search for intranuclear neutron-antineutron transition (n → n̄) followed by n̄-nucleon annihilation within an 40Ar nucleus, using the MicroBooNE liquid argon time projection chamber (LArTPC) detector. A discovery of n → n̄ transition or a new best limit on the lifetime of this process would either constitute physics beyond the Standard Model or greatly constrain theories of baryogenesis, respectively. The approach presented in this paper makes use of deep learning methods to select n → n̄ events based on their unique features and differentiate them from cosmogenic backgrounds. The achieved signal and background efficiencies are (70.22 ± 6.04)% and (0.0020 ± 0.0003)%, respectively. A demonstration of a search is performed with a data set corresponding to an exposure of 3.32 × 1026 neutron-years, and where the background rate is constrained through direct measurement, assuming the presence of a negligible signal. With this approach, no excess of events over the background prediction is observed, setting a demonstrative lower bound on the n → n̄ lifetime in 40Ar of τm ≳ 1.1 × 1026 years, and on the free n → n̄ transition time of τn→n̄ ≳ 2.6 × 105 s, each at the 90% confidence level. This analysis represents a first-ever proof-of-principle demonstration of the ability to search for this rare process in LArTPCs with high efficiency and low background.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
Search for the Bs0→ μ<sup>+</sup>μ<sup>−</sup>γ decay
, Journal of High Energy Physics, Vol: 2024A search for the fully reconstructed Bs0→ μ+μ−γ decay is performed at the LHCb experiment using proton-proton collisions at s = 13 TeV corresponding to an integrated luminosity of 5.4 fb−1. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set (Formula presented.) at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2mμ, 1.70] GeV/c2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Observation of the Formula Presented decay and studies of the Formula Presented baryon in proton-proton collisions at Formula Presented
, Physical Review D, Vol: 110, ISSN: 2470-0010The first observation of the decay Formula Presented and measurement of the branching ratio of Formula Presented to Formula Presented are presented. The Formula Presented and Formula Presented mesons are reconstructed using their dimuon decay modes. The results are based on proton-proton colliding beam data from the LHC collected by the CMS experiment at Formula Presented in 2016-2018, corresponding to an integrated luminosity of Formula Presented. The branching fraction ratio is measured to be Formula Presented, where the last uncertainty comes from the uncertainties in the branching fractions of the charmonium states. New measurements of the Formula Presented baryon mass and natural width are also presented, using the Formula Presented final state, where the Formula Presented baryon is reconstructed through the decays Formula Presented, Formula Presented, Formula Presented, and Formula Presented. Finally, the fraction of Formula Presented baryons produced from Formula Presented decays is determined.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for long-lived heavy neutral leptons decaying in the CMS muon detectors in proton-proton collisions at Formula Presented
, Physical Review D, Vol: 110, ISSN: 2470-0010A search for heavy neutral leptons (HNLs) decaying in the CMS muon system is presented. A data sample is used corresponding to an integrated luminosity of Formula Presented of proton-proton collisions at Formula Presented, recorded at the CERN LHC in 2016-2018. Decay products of long-lived HNLs could interact with the shielding materials in the CMS muon system and create hadronic and electromagnetic showers detected in the muon chambers. This distinctive signature provides a unique handle to search for HNLs with masses below 4 GeV and proper decay lengths of the order of meters. The signature is sensitive to HNL couplings to all three generations of leptons. Candidate events are required to contain a prompt electron or muon originating from a vertex on the beam axis and a displaced shower in the muon chambers. No significant deviations from the standard model background expectation are observed. In the electron (muon) channel, the most stringent limits to date are set for HNLs in the mass range of 2.1-3.0 (1.9-3.3) GeV, reaching mixing matrix element squared values as low as Formula Presented.
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Journal articleBhattacharya A, Habib MR, Ahmed A, et al., 2024,
Spin-valve-like magnetoresistance and anomalous Hall effect in magnetic Weyl metal Mn2 PdSn
, Physical Review B, Vol: 110, ISSN: 2469-9950Realization of noncentrosymmetric magnetic Weyl metals is expected to exhibit anomalous transport properties stemming from the interplay of unusual bulk electronic topology and magnetism. Here, we present spin-valve-like magnetoresistance at room temperature in ferrimagnetic Weyl metal Mn2PdSn that crystallizes in the inverse Heusler structure. Anomalous magnetoresistance displays dominant asymmetric component attributed to domain wall electron scattering, indicative of spin-valve-like behavior. Ab initio calculations confirm the topologically nontrivial nature of the band structure, with Weyl nodes proximate to Fermi energy, providing deeper insights into the observed intrinsic Berry curvature mediated substantial anomalous Hall conductivity. Our results underscore the inverse Heusler compounds as promising platform to realize magnetic Weyl metals/semimetals and leverage emergent transport properties for electronic functionalities.
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Journal articleKashiwagi Y, Abe K, Bronner C, et al., 2024,
Performance of SK-Gd’s Upgraded Real-time Supernova Monitoring System
, Astrophysical Journal, Vol: 970, ISSN: 0004-637XAmong multimessenger observations of the next Galactic core-collapse supernova, Super-Kamiokande (SK) plays a critical role in detecting the emitted supernova neutrinos, determining the direction to the supernova (SN), and notifying the astronomical community of these observations in advance of the optical signal. In 2022, SK has increased the gadolinium dissolved in its water target (SK-Gd) and has achieved a Gd concentration of 0.033%, resulting in enhanced neutron detection capability, which in turn enables more accurate determination of the supernova direction. Accordingly, SK-Gd’s real-time supernova monitoring system has been upgraded. SK_SN Notice, a warning system that works together with this monitoring system, was released on 2021 December 13, and is available through GCN Notices. When the monitoring system detects an SN-like burst of events, SK_SN Notice will automatically distribute an alarm with the reconstructed direction to the supernova candidate within a few minutes. In this paper, we present a systematic study of SK-Gd’s response to a simulated Galactic SN. Assuming a supernova situated at 10 kpc, neutrino fluxes from six supernova models are used to characterize SK-Gd’s pointing accuracy using the same tools as the online monitoring system. The pointing accuracy is found to vary from 3° to 7° depending on the models. However, if the supernova is closer than 10 kpc, SK_SN Notice can issue an alarm with three-degree accuracy, which will benefit follow-up observations by optical telescopes with large fields of view.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for dark QCD with emerging jets in proton-proton collisions at s = 13 TeV
, Journal of High Energy Physics, Vol: 2024A search for “emerging jets” produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed using data collected by the CMS experiment corresponding to an integrated luminosity of 138 fb−1. This search examines a hypothetical dark quantum chromodynamics (QCD) sector that couples to the standard model (SM) through a scalar mediator. The scalar mediator decays into an SM quark and a dark sector quark. As the dark sector quark showers and hadronizes, it produces long-lived dark mesons that subsequently decay into SM particles, resulting in a jet, known as an emerging jet, with multiple displaced vertices. This search looks for pair production of the scalar mediator at the LHC, which yields events with two SM jets and two emerging jets at leading order. The results are interpreted using two dark sector models with different flavor structures, and exclude mediator masses up to 1950 (1950) GeV for an unflavored (flavor-aligned) dark QCD model. The unflavored results surpass a previous search for emerging jets by setting the most stringent mediator mass exclusion limits to date, while the flavor-aligned results provide the first direct mediator mass exclusion limits to date.
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Journal articleTumasyan A, Adam W, Andrejkovic JW, et al., 2024,
Search for a scalar or pseudoscalar dilepton resonance produced in association with a massive vector boson or top quark-antiquark ffiffi pair in multilepton events at ps=13 TeV
, Physical Review D, Vol: 110, ISSN: 2470-0010A search for beyond the standard model spin-0 bosons, ϕ, that decay into pairs of electrons, muons, or tau leptons is presented. The search targets the associated production of such bosons with a W or Z gauge boson, or a top quark-antiquark pair, and uses events with three or four charged leptons, including hadronically decaying tau leptons. The proton-proton collision data set used in the analysis was collected at the LHC from 2016 to 2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of 138 fb−1. The observations are consistent with the predictions from standard model processes. Upper limits are placed on the product of cross sections and branching fractions of such new particles over the mass range of 15 to 350 GeV with scalar, pseudoscalar, or Higgs-boson-like couplings, as well as on the product of coupling parameters and branching fractions. Several model-dependent exclusion limits are also presented. For a Higgs-boson-like ϕ model, limits are set on the mixing angle of the Higgs boson with the ϕ boson. For the associated production of a ϕ boson with a top quark-antiquark pair, limits are set on the coupling to top quarks. Finally, limits are set for the first time on a fermiophilic dilaton-like model with scalar couplings and a fermiophilic axion-like model with pseudoscalar couplings.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
First observation of the Λb0→ D<sup>+</sup>D<sup>−</sup>Λ decay
, Journal of High Energy Physics, Vol: 2024The Λb0 → D+D−Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.3 fb−1. Using the B0 → D+D−KS0 decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be (Formula presented.) where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, BB0→D+D−KS0, and the cross-section ratio, σΛb0/σB0, previously measured by LHCb are used to derive the branching fraction of the Λb0→ D+D−Λ decay (Formula presented.) where the third and fourth contributions are due to uncertainties of BB0→D+D−KS0 and σΛb0/σB0, respectively. Inspection of the D+Λ and D+D− invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λb0 → D*+D−Λ decay is also observed for the first time as a partially reconstructed component in the D+D−Λ invariant mass spectrum.
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Journal articleAcero MA, Acharya B, Adamson P, et al., 2024,
Expanding neutrino oscillation parameter measurements in NOvA using a Bayesian approach
, Physical Review D, Vol: 110, ISSN: 2470-0010NOvA is a long-baseline neutrino oscillation experiment that measures oscillations in charged-current νμ→νμ (disappearance) and νμ→νe (appearance) channels, and their antineutrino counterparts, using neutrinos of energies around 2 GeV over a distance of 810 km. In this work we reanalyze the dataset first examined in our previous paper [Phys. Rev. D 106, 032004 (2022)PRVDAQ2470-001010.1103/PhysRevD.106.032004] using an alternative statistical approach based on Bayesian Markov chain Monte Carlo. We measure oscillation parameters consistent with the previous results. We also extend our inferences to include the first NOvA measurements of the reactor mixing angle θ13, where we find 0.071≤sin22θ13≤0.107, and the Jarlskog invariant, where we observe no significant preference for the CP-conserving value J=0 over values favoring CP violation. We use these results to examine the effects of constraints from short-baseline measurements of θ13 using antineutrinos from nuclear reactors when making NOvA measurements of θ23. Our long-baseline measurement of θ13 is shown to be consistent with the reactor measurements, supporting the general applicability and robustness of the Pontecorvo-Maki-Nakagawa-Sakata framework for neutrino oscillations.
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Journal articleTumasyan A, Adam W, Andrejkovic JW, et al., 2024,
Search for high-mass exclusive diphoton production with tagged protons in proton-proton collisions at Formula Presented
, Physical Review D, Vol: 110, ISSN: 2470-0010A search is presented for high-mass exclusive diphoton production via photon-photon fusion in proton-proton collisions at Formula Presented in events where both protons survive the interaction. The analysis utilizes data corresponding to an integrated luminosity of Formula Presented collected in 2016-2018 with the central CMS detector and the CMS and TOTEM precision proton spectrometer (PPS). Events that have two photons with high transverse momenta (Formula Presented), back-to-back in azimuth, and with a large diphoton invariant mass (Formula Presented) are selected. To remove the dominant inclusive diphoton backgrounds, the kinematic properties of the protons detected in PPS are required to match those of the central diphoton system. Only events having opposite-side forward protons detected with a fractional momentum loss between 0.035 and 0.15 (0.18) for the detectors on the negative (positive) side of CMS are considered. One exclusive diphoton candidate is observed for an expected background of 1.1 events. Limits at 95% confidence level are derived for the four-photon anomalous coupling parameters Formula Presented and Formula Presented, using an effective field theory. Additionally, upper limits are placed on the production of axionlike particles with coupling strength to photons Formula Presented that varies from Formula Presented to Formula Presented over the mass range from 500 to 2000 GeV.
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Journal articleCMS Collaboration, 2024,
Search for ZZ and ZH production in the bbb¯ b final state using ¯proton-proton collisions at √s = 13 TeV
, European Physical Journal C: Particles and Fields, Vol: 84, ISSN: 1434-6052A search for ZZ and ZH production in the bbb¯ b¯final state is presented, where H is the standard model (SM)Higgs boson. The search uses an event sample of proton-proton collisions corresponding to an integrated luminosityof 133 fb−1 collected at a center-of-mass energy of 13 TeVwith the CMS detector at the CERN LHC. The analysis introduces several novel techniques for deriving and validating amulti-dimensional background model based on control samples in data. A multiclass multivariate classifier customizedfor the bbb¯ b final state is developed to derive the background ¯model and extract the signal. The data are found to be consistent, within uncertainties, with the SM predictions. Theobserved (expected) upper limits at 95% confidence level arefound to be 3.8 (3.8) and 5.0 (2.9) times the SM predictionfor the ZZ and ZH production cross sections, respectively.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Combination of Measurements of the Top Quark Mass from Data Collected by the ATLAS and CMS Experiments at sqrt[s]=7 and 8 TeV.
, Phys Rev Lett, Vol: 132A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The datasets used correspond to an integrated luminosity of up to 5 and 20 fb^{-1} of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak t channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is m_{t}=172.52±0.14(stat)±0.30(syst) GeV, with a total uncertainty of 0.33 GeV.
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Journal articleTumasyan A, Adam W, Andrejkovic JW, et al., 2024,
Search for central exclusive production of top quark pairs in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV with tagged protons
, Journal of High Energy Physics, Vol: 2024<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A search for the central exclusive production of top quark-antiquark pairs (<jats:inline-formula><jats:alternatives><jats:tex-math>$$ \textrm{t}\overline{\textrm{t}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>t</mml:mi> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>) is performed for the first time using proton-tagged events in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 29.4 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. The <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \textrm{t}\overline{\textrm{t}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>t</mml:mi> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula> decay products are reconstructed using the central CMS detector, while forward protons are measured in the CMS-TOTEM precision proton spectrometer. An observed (expected) upper bound on the production cross section of 0.59 (1.14) pb is set at 95% confidence level, for collisions of protons with fractional momentum losses between 2 and 20%.</jats:p>
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for long-lived heavy neutrinos in the decays of B mesons produced in proton-proton collisions 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 search for long-lived heavy neutrinos (N) in the decays of B mesons produced in proton-proton collisions at <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 13 TeV is presented. The data sample corresponds to an integrated luminosity of 41.6 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup> collected in 2018 by the CMS experiment at the CERN LHC, using a dedicated data stream that enhances the number of recorded events containing B mesons. The search probes heavy neutrinos with masses in the range 1 < <jats:italic>m</jats:italic><jats:sub>N</jats:sub> < 3 GeV and decay lengths in the range 10<jats:sup><jats:italic>−</jats:italic>2</jats:sup> < <jats:italic>c</jats:italic>τ<jats:sub>N</jats:sub> < 10<jats:sup>4</jats:sup> mm, where τ<jats:sub>N</jats:sub> is the N proper mean lifetime. Signal events are defined by the signature B → <jats:italic>ℓ</jats:italic><jats:sub>B</jats:sub>NX; N → <jats:italic>ℓ</jats:italic><jats:sup><jats:italic>±</jats:italic></jats:sup>π<jats:sup>∓</jats:sup>, where the leptons <jats:italic>ℓ</jats:italic><jats:sub>B</jats:sub> and <jats:italic>ℓ</jats:italic> can be either a muon or an electron, provided that at least one of them is a muon. The hadronic recoil system, X, is treated inclusively an
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Journal articleChatterjee S, Das I, 2024,
Structural, magnetic, magnetocaloric behavior and magneto-transport, electrical polarization study in 3d based bulk and nano-crystalline multiferroic double perovskite Dy2MnCoO6.
, J Phys Condens Matter, Vol: 36In this paper, we report a detailed investigation of the crystal structure, magnetic, magnetocaloric, magneto-transport and electrical polarization properties of a new multiferroic material in the polycrystalline and nanocrystalline form of the Dy2MnCoO6double perovskite. Both compounds crystallized in the monoclinic structure with P21/n space group. The magnetic properties of both systems are mainly dominant ferromagnetic (FM) and weak antiferromagnetic (AFM). The FM/AFM coupling is related by the competing and combining functions of the radius and the magnetic moments of rare earth ions (i.e. 3d-4f exchange interactions). The reduction of the saturation magnetization in the isothermal magnetization curves can be explained by the existence of anti-phase boundaries and local anti-site defects in the system. Moreover, these materials hold reasonable values of magnetocaloric parameters and the absence of hysteresis makes the system a potential candidate for magnetic refrigeration. These compounds revealed two magnetic phase transitions, according to the appearance of two peaks in the temperature dependence of magnetic entropy change curves. The temperature dependent resistivity data for both the systems display semiconductor nature near room temperature and insulating like behavior at low temperature regime. The variable-range hopping conduction mechanism is used to best understand their transport mechanism. In addition, the electrical polarization loop at low temperature confirms the presence of ferroelectricity for both the studied systems. The decreases polarization under an external magnetic field evidence the weak magnetoelectric coupling. The coexistence of FM ordering with insulating behavior and ferroelectricity at low temperature promises new opportunities and improvements in next generation applications for information storage, spintronic, and sensors.
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Journal article, 2024,
Extracting the speed of sound in quark-gluon plasma with ultrarelativistic lead-lead collisions at the LHC.
, Rep Prog Phys, Vol: 87Ultrarelativistic nuclear collisions create a strongly interacting state of hot and dense quark-gluon matter that exhibits a remarkable collective flow behavior with minimal viscous dissipation. To gain deeper insights into its intrinsic nature and fundamental degrees of freedom, we determine the speed of sound in an extended volume of quark-gluon plasma using lead-lead (PbPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data were recorded by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 0.607 nb-1. The measurement is performed by studying the multiplicity dependence of the average transverse momentum of charged particles emitted in head-on PbPb collisions. Our findings reveal that the speed of sound in this matter is nearly half the speed of light, with a squared value of0.241±0.002(stat)±0.016(syst)in natural units. The effective medium temperature, estimated using the mean transverse momentum, is219±8(syst)MeV. The measured squared speed of sound at this temperature aligns precisely with predictions from lattice quantum chromodynamic (QCD) calculations. This result provides a stringent constraint on the equation of state of the created medium and direct evidence for a deconfined QCD phase being attained in relativistic nuclear collisions.
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Journal articleHayrapetyan AA, Tumasyan A, Adam W, et al., 2024,
Search for heavy neutral leptons in final states with electrons, muons, and hadronically decaying tau leptons in proton-proton collisions 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 search for heavy neutral leptons (HNLs) of Majorana or Dirac type using proton-proton collision data at <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 13 TeV is presented. The data were collected by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 138 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. Events with three charged leptons (electrons, muons, and hadronically decaying tau leptons) are selected, corresponding to HNL production in association with a charged lepton and decay of the HNL to two charged leptons and a standard model (SM) neutrino. The search is performed for HNL masses between 10 GeV and 1.5 TeV. No evidence for an HNL signal is observed in data. Upper limits at 95% confidence level are found for the squared coupling strength of the HNL to SM neutrinos, considering exclusive coupling of the HNL to a single SM neutrino generation, for both Majorana and Dirac HNLs. The limits exceed previously achieved experimental constraints for a wide range of HNL masses, and the limits on tau neutrino coupling scenarios with HNL masses above the W boson mass are presented for the first time.</jats:p>
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Journal articleAbe K, Bronner C, Hayato Y, et al., 2024,
Search for Periodic Time Variations of the Solar ^{8}B Neutrino Flux between 1996 and 2018 in Super-Kamiokande.
, Phys Rev Lett, Vol: 132We report a search for time variations of the solar ^{8}B neutrino flux using 5804 live days of Super-Kamiokande data collected between May 31, 1996, and May 30, 2018. Super-Kamiokande measured the precise time of each solar neutrino interaction over 22 calendar years to search for solar neutrino flux modulations with unprecedented precision. Periodic modulations are searched for in a dataset comprising five-day interval solar neutrino flux measurements with a maximum likelihood method. We also applied the Lomb-Scargle method to this dataset to compare it with previous reports. The only significant modulation found is due to the elliptic orbit of the Earth around the Sun. The observed modulation is consistent with astronomical data: we measured an eccentricity of (1.53±0.35)%, and a perihelion shift of (-1.5±13.5) days.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for Baryon Number Violation in Top Quark Production and Decay Using Proton-Proton Collisions at sqrt[s]=13 TeV.
, Phys Rev Lett, Vol: 132A search is presented for baryon number violating interactions in top quark production and decay. The analysis uses data from proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC with an integrated luminosity of 138 fb^{-1}. Candidate events are selected by requiring two oppositely charged leptons (electrons or muons) and exactly one jet identified as originating from a bottom quark. Multivariate discriminants are used to separate the signal from the background. No significant deviation from the standard model prediction is observed. Upper limits are placed on the strength of baryon number violating couplings. For the first time the production of single top quarks via baryon number violating interactions is studied. This allows the search to set the most stringent constraints to date on the branching fraction of the top quark decay to a lepton, an up-type quark (u or c), and a down-type quark (d, s, or b). The results improve the previous bounds by 3 to 6 orders of magnitude based on the fermion flavor combination of the baryon number violating interactions.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2024,
Search for the decay of the Higgs boson to a pair of light pseudoscalar bosons in the final state with four bottom quarks in proton-proton collisions at $$ \sqrt{\textrm{s}} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2024<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A search is presented for the decay of the 125 GeV Higgs boson (H) to a pair of new light pseudoscalar bosons (a), followed by the prompt decay of each a boson to a bottom quark-antiquark pair, <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \textrm{H}\to \textrm{aa}\to \textrm{b}\overline{\textrm{b}}\textrm{b}\overline{\textrm{b}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>H</mml:mi> <mml:mo>→</mml:mo> <mml:mi>aa</mml:mi> <mml:mo>→</mml:mo> <mml:mi>b</mml:mi> <mml:mover> <mml:mi>b</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>b</mml:mi> <mml:mover> <mml:mi>b</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>. The analysis is performed using a data sample of proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. To reduce the background from standard model processes, the search requires the Higgs boson to be produced in association with a leptonically decaying W or Z boson. The analysis probes the production of new light bosons in a 15 < <jats:italic>m</jats:italic><jats:sub>a</jats:sub> < 60 GeV mass range. Assuming the standard model predictions for the Higgs boson production cr
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2024,
Modification of χ_{c1}(3872) and ψ(2S) Production in pPb Collisions at sqrt[s_{NN}]=8.16 TeV.
, Phys Rev Lett, Vol: 132The LHCb Collaboration measures production of the exotic hadron χ_{c1}(3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state ψ(2S) suggests that the exotic χ_{c1}(3872) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify χ_{c1}(3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron.
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Journal articleAbratenko P, Alterkait O, Andrade Aldana D, et al., 2024,
First Search for Dark-Trident Processes Using the MicroBooNE Detector.
, Phys Rev Lett, Vol: 132We present a first search for dark-trident scattering in a neutrino beam using a dataset corresponding to 7.2×10^{20} protons on target taken with the MicroBooNE detector at Fermilab. Proton interactions in the neutrino target at the main injector produce π^{0} and η mesons, which could decay into dark-matter (DM) particles mediated via a dark photon A^{'}. A convolutional neural network is trained to identify interactions of the DM particles in the liquid-argon time projection chamber (LArTPC) exploiting its imagelike reconstruction capability. In the absence of a DM signal, we provide limits at the 90% confidence level on the squared kinematic mixing parameter ϵ^{2} as a function of the dark-photon mass in the range 10≤M_{A^{'}}≤400 MeV. The limits cover previously unconstrained parameter space for the production of fermion or scalar DM particles χ for two benchmark models with mass ratios M_{χ}/M_{A^{'}}=0.6 and 2 and for dark fine-structure constants 0.1≤α_{D}≤1.
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Journal articleMandal AK, Sarkar S, Chandra M, et al., 2024,
Navigating the magnetic contribution of the commonly used single-crystal substrates SrTiO<inf>3</inf> (100) and LaAlO<inf>3</inf> (100) in weak magnetic thin films
, Journal of Physics D: Applied Physics, Vol: 57, ISSN: 0022-3727In recent years, thin films of weak ferromagnetic materials have been in huge demand; however, probing their magnetic characteristics has been difficult due to contributions from underlying substrates. In the present study, we have analyzed the magnetic properties of the commonly used single-crystal SrTiO3 (100) and LaAlO3 (100) substrates and performed a time-dependent annealing protocol in vacuum and ambient oxygen pressure to mitigate the intrinsic weak ferromagnetic contributions from these substrates arising due to the presence of disorder or defects such as vacancies in the pristine substrates. It is shown that after proper air annealing, the substrate magnetic background becomes diamagnetic. When such air-annealed diamagnetic substrates are used for the deposition of low-thickness films carrying low magnetic moments such as SrRuO3 and SrMnO3 thin films, their magnetic transitions are explicitly observed. The proposed annealing protocols help to improve the signal from weak magnetic samples. This allows us to analyze the film’s magnetic properties without worrying about the contribution from the substrate.
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Journal articleAhmed A, Das K, Das I, 2024,
Large magnetocaloric effect and giant magnetoresistance in rare earth based intermetallic compound ErAl3: construction of magnetic phase diagram.
, J Phys Condens Matter, Vol: 36This study explores the magnetic and magnetotransport behavior of polycrystalline ErAl3compound. The polycrystalline compound adopts HoAl3-type structures with the R-3m space group, No. 166-2 and hR60 configurations. Multiple magnetic orderings and two field-induced metamagnetic transitions are observed. ErAl3exhibits a significant magnetocaloric effect (MCE),-ΔSM= 15.25 J kg-1K-1and high relative cooling power of 383 J kg-1with applied magnetic field change (ΔH) of 70 kOe near the paramagnetic to ferromagnetic transition, showcasing its potential for magnetic refrigeration technology. The compound also demonstrates metallic behavior, with a notable magnetoresistance of 48.5%at 2 K due to the suppression of antiferromagnetism. The magnetic phase diagram reveals four distinct phases influenced by temperature and magnetic field, identified through the study of the MCE.
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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: 6This 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 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 Formula Presented
, Physical Review D, Vol: 109, ISSN: 2470-0010A 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 Formula Presented. 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 Formula Presented
, Physical Review D, Vol: 109, ISSN: 2470-0010A 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 Formula Presented recorded with the CMS detector at the LHC in 2016-2018. The analyzed data correspond to an integrated luminosity of up to Formula Presented. 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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