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Journal articleOishi K, Aoki M, Kuribayashi S, et al., 2026,
Development of the Range Counter for the COMET Phase-α Experiment
, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Vol: 1082, ISSN: 0168-9002 -
Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
First Exclusive Reconstruction of the <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:mrow> <mml:mo>*</mml:mo> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , <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:mrow> <mml:mo>*</mml:mo> <mml:mn>0</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> Mesons and Precise Measurement of Their Masses
, Physical Review Letters, Vol: 136, ISSN: 0031-9007<jats:p> Using proton-proton collision data collected by the CMS experiment at <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:msqrt> <a:mrow> <a:mi>s</a:mi> </a:mrow> </a:msqrt> <a:mo>=</a:mo> <a:mn>13</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>TeV</a:mi> </a:mrow> </a:math> in 2016–2018, corresponding to an integrated luminosity of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mn>140</c:mn> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:msup> <c:mrow> <c:mi>fb</c:mi> </c:mrow> <c:mrow> <c:mo>−</c:mo> <c:mn>1</c:mn> </c:mrow> </c:msup> </c:mrow> </c:math> , the first full reconstruction of the three vector <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>B</e:mi> </e:math>
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Journal articleNakanishi F, Abe K, Abe S, et al., 2026,
First Associated Neutrino Search for a Failed Supernova Candidate with Super-Kamiokande
, The Astrophysical Journal Letters, Vol: 997, Pages: L9-L9, ISSN: 2041-8205<jats:title>Abstract</jats:title> <jats:p> In 2024, a failed supernova (SN) candidate, M31-2014-DS1, was reported in the Andromeda galaxy (M31), located at a distance of approximately 770 kpc. In this Letter, we search for neutrinos from this failed SN using data from Super-Kamiokande (SK). Based on the estimated time of black hole formation inferred from optical and infrared observations, we define a search window for neutrino events in the SK data. Using this window, we develop a dedicated analysis method for failed SNe and apply it to M31-2014-DS1, by conducting a cluster search using the timing and energy information of candidate events. No significant neutrino excess is observed within the search region. Consequently, we place an upper limit on the time-integrated electron antineutrino luminosity from M31-2014-DS1 and discuss its implications for various failed SN models and their neutrino emission characteristics. Despite the 18 MeV threshold adopted to suppress backgrounds, the search remains sufficiently sensitive to constrain the Shen-TM1 equation of state, in a more optimistic emission scenario with progenitor stars of 40 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and relatively high mean electron-antineutrino energies of about 23.2 MeV, yielding a 90% confidence level upper limit of 1.76 × 10 <jats:sup>53</jats:sup> erg on the time-integrated electron antineutrino luminosity, moderately above the expected value of 1.35 × 10 <jats:sup>53</jats:sup> erg. </jats:p>
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>b</mml:mi> </mml:math> -hadron decays to long-lived particles in the CMS endcap muon detectors
, Physical Review D, Vol: 113, ISSN: 2470-0010<jats:p> A search for long-lived particles originating from the decay of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>b</a:mi> </a:math> hadrons produced in proton-proton collisions with a center-of-mass energy of 13 TeV at the LHC is presented. The analysis is performed on a dataset recorded in 2018, corresponding to an integrated luminosity of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mn>41.6</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> . Interactions of the long-lived particles in the CMS endcap muon system would create hadronic or electromagnetic showers, producing clusters of detector hits. Selected events contain at least one such high-multiplicity cluster in the muon endcaps and require the presence of a displaced muon. The most stringent upper limits to date on the branching fraction <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi mathvariant="script">B</e:mi> <e:mo stretchy="false">(</e:mo> <e:mi>B</e:mi> <e:mo stretchy="false">→</e:mo> <e:mi>K</e:mi>
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
Observation of B_{c}^{+}→Dh^{+}h^{-} Decays.
, Phys Rev Lett, Vol: 136Searches are presented for B_{c}^{+}→Dh^{+}h^{-} decays, where D is a charmed meson and h^{±} is a charged pion or kaon, using pp collision data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb^{-1}. The decays B_{c}^{+}→D^{+}K^{+}π^{-}, B_{c}^{+}→D^{*+}K^{+}π^{-}, and B_{c}^{+}→D_{s}^{+}K^{+}K^{-} are observed for the first time. Their branching fractions, expressed as ratios relative to that of the B_{c}^{+}→B_{s}^{0}π^{+} decay, are determined to be R(B_{c}^{+}→D^{+}K^{+}π^{-})=(1.96±0.23±0.08±0.10)×10^{-3}, R(B_{c}^{+}→D^{*+}K^{+}π^{-})=(3.67±0.55±0.24±0.20)×10^{-3}, R(B_{c}^{+}→D_{s}^{+}K^{+}K^{-})=(1.61±0.35±0.13±0.07)×10^{-3}, where the first uncertainty is statistical, the second is systematic, and the third is due to the limited precision on the D-meson branching fractions. The decay channels proceed primarily through excited K^{0} or D^{0} resonances or ϕ mesons, and open a new avenue for studies of charge-parity violation in beauty mesons.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
First Observation of CP Violation and Measurement of Polarization in B^{+}→ρ(770)^{0}K^{*}(892)^{+} Decays.
, Phys Rev Lett, Vol: 136An amplitude analysis of the B^{+}→(π^{+}π^{-})(K_{S}^{0}π^{+}) decay is performed in the mass regions 0.30<m_{π^{+}π^{-}}<1.10 GeV/c^{2} and 0.75<m_{K_{S}^{0}π^{+}}<1.20 GeV/c^{2}, using pp collision data recorded with the LHCb detector corresponding to an integrated luminosity of 9 fb^{-1}. The polarization fractions and CP asymmetries for B^{+}→ρ(770)^{0}K^{*}(892)^{+} decays are measured. Violation of the CP symmetry in the decay B^{+}→ρ(770)^{0}K^{*}(892)^{+} is observed for the first time, with a significance exceeding 9 standard deviations. The CP asymmetry is measured to be A_{CP}=0.507±0.062(stat)±0.024(syst) and the CP-averaged longitudinal polarization fraction of f_{L}=0.720±0.028(stat)±0.009(syst). The measurements help to shed light on the polarization puzzle of B mesons decaying to two vector mesons.
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Journal articleAbubakar S, Acero MA, Acharya B, et al., 2026,
Precision Measurement of Neutrino Oscillation Parameters with 10 Years of Data from the NOvA Experiment
, Physical Review Letters, Vol: 136, ISSN: 0031-9007This Letter reports measurements of muon-neutrino disappearance and electron-neutrino appearance and the corresponding antineutrino processes between the two NOvA detectors in the NuMI neutrino beam. These measurements use a dataset with double the neutrino mode beam exposure that was previously analyzed, along with improved simulation and analysis techniques. A joint fit to these samples in the three-flavor paradigm results in the most precise single-experiment constraint on the atmospheric neutrino mass splitting, Δm322=2.431-0.034+0.036(-2.479-0.036+0.036)×10-3 eV2 if the mass ordering is normal (inverted). In both orderings, a region close to maximal mixing with sin2θ23=0.55-0.06+0.02 is preferred. The NOvA data show a mild preference for the normal mass ordering with a Bayes factor of 2.4 (corresponding to 70% of the posterior probability), indicating that the normal ordering is 2.4 times more probable than the inverted ordering. When incorporating a 2D Δm322-sin22θ13 constraint based on Daya Bay data, this preference strengthens to a Bayes factor of 6.6 (87%).
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Simultaneous Probe of the Charm and Bottom Quark Yukawa Couplings Using tt[over ¯]H Events.
, Phys Rev Lett, Vol: 136A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H→cc[over ¯], produced in association with a top quark-antiquark pair (tt[over ¯]H) is presented. The search is performed with data from proton-proton collisions at sqrt[s]=13 TeV, corresponding to an integrated luminosity of 138 fb^{-1}. Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed tt[over ¯]H(H→bb[over ¯]) event rate relative to the standard model expectation is 0.91_{-0.22}^{+0.26}. The observed (expected) upper limit on the product of production cross section and branching fraction σ(tt[over ¯]H)B(H→cc[over ¯]) is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for H→cc[over ¯] via associated production with a W or Z boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, κ_{c}, is |κ_{c}|<3.5 (2.7), the most stringent constraint to date.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
A model-independent measurement of the CKM angle γ in the decays B±→ [K+K−π+π−]Dh± and B±→ [π+π−π+π−]Dh± (h = K, π)
, Journal of High Energy Physics, Vol: 2026A model-independent determination of the CKM angle γ is presented, using the B<sup>±</sup> → [K<sup>+</sup>K<sup>−</sup>π<sup>+</sup>π<sup>−</sup>]<inf>D</inf>h<sup>±</sup> and B<sup>±</sup> → [π<sup>+</sup>π<sup>−</sup>π<sup>+</sup>π<sup>−</sup>]<inf>D</inf>h<sup>±</sup> decays, with h = K, π. This measurement is the first phase-space binned study of these decay modes, and uses a sample of proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb<sup>−1</sup>. The phase-space bins are optimised for sensitivity to γ, and in each bin external inputs from the BESIII experiment are used to constrain the charm strong-phase parameters. The result of this binned analysis is γ=53.9−8.9+9.5°, where the uncertainty includes both statistical and systematic contributions. Furthermore, when combining with existing phase-space integrated measurements of the same decay modes, a value of γ=52.6−6.4+8.5° is obtained, which is one of the most precise determinations of γ to date.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2026,
Measurements of the inclusive W and Z boson production cross sections and their ratios in proton-proton collisions at TeV
, Journal of High Energy Physics, Vol: 2026Measurements are presented of the W and Z boson production cross sections in proton-proton collisions at a center-of-mass energy of 13.6 TeV. Data collected in 2022 and corresponding to an integrated luminosity of 5.01 fb<sup>−1</sup> with one or two identified muons in the final state are analyzed. The results for the products of total inclusive cross sections and branching fractions for muonic decays of W and Z bosons are (acceptance) nb for W<sup>+</sup> boson production, (acceptance) nb for W<sup>−</sup> boson production, and (acceptance) nb for the Z boson production in the dimuon mass range of 60–120 GeV, all with negligible statistical uncertainties. Furthermore, the corresponding fiducial cross sections, as well as cross section ratios for both fiducial and total phase space, are provided. The ratios include charge-separated results for W boson production (W<sup>+</sup> and W<sup>−</sup>) and the sum of the two contributions (W<sup>±</sup>), each relative to the measured Z boson production cross section. Additionally, the ratio of the measured cross sections for W<sup>+</sup> and W<sup>−</sup> boson production is reported. All measurements are in agreement with theoretical predictions, calculated at next-to-next-to-leading order accuracy in quantum chromodynamics.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2025,
Observation of Coherent ϕ(1020) Meson Photoproduction in Ultraperipheral PbPb Collisions at sqrt[s_{NN}]=5.36 TeV.
, Phys Rev Lett, Vol: 135The first observation of coherent ϕ(1020) meson photoproduction off heavy nuclei is presented using ultraperipheral lead-lead collisions at a center-of-mass energy per nucleon pair of 5.36 TeV. The data were collected by the CMS experiment and correspond to an integrated luminosity of 1.62 μb^{-1}. The ϕ(1020) meson signals are reconstructed via the K^{+}K^{-} decay channel. The production cross section is presented as a function of the ϕ(1020) meson rapidity in the range 0.3<|y|<1.0, probing gluons that carry a fraction of the nucleon momentum (x) around 10^{-4}. The observed cross section exhibits little dependence on rapidity and is significantly suppressed, by a factor of ∼5, compared to a baseline model that treats a nucleus as a collection of free nucleons. Theoretical models that incorporate the nuclear shadowing effect generally provide a better description of the ϕ(1020) data than those incorporating gluon saturation. This study establishes a powerful new tool for exploring nuclear effects and nuclear gluonic structure in the small-x regime at a unique energy scale bridging the perturbative and nonperturbative quantum chromodynamics domains.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
First Observation of the Charmless Baryonic Decay B^{+}→Λ[over ¯]pp[over ¯]p.
, Phys Rev Lett, Vol: 135A search for the charmless baryonic decay B^{+}→Λ[over ¯]pp[over ¯]p is performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 5.4 fb^{-1}. The branching fraction for this decay is measured for the first time relative to that of the topologically similar decay B^{+}→J/ψK^{+}, with J/ψ→Λ[over ¯]pK^{-}. The branching fraction is measured to be B(B^{+}→Λ[over ¯]pp[over ¯]p)=(2.15±0.35±0.12±0.28)×10^{-7}, where the first uncertainty is statistical, the second is systematic, and the third arises from the uncertainty in the normalization channel branching fraction. The CP asymmetry is measured to be A_{CP}=(5.4±15.6±2.4)%, where the uncertainties are statistical and systematic. The background-subtracted invariant-mass distributions of Λ[over ¯]p and p[over ¯]p pairs exhibit pronounced enhancements at both kinematic thresholds, in contrast to a uniform phase-space distribution.
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Journal articleAbe K, Abe S, Akutsu R, et al., 2025,
Results from the T2K Experiment on Neutrino Mixing Including a New Far Detector μ-like Sample.
, Phys Rev Lett, Vol: 135We have made improved measurements of three-flavor neutrino mixing with 19.7(16.3)×10^{20} protons on target in (anti-)neutrino-enhanced beam modes. A new sample of muon-neutrino events with tagged pions has been added at the far detector, as well as new proton and photon-tagged samples at the near detector. Significant improvements have been made to the flux and neutrino interaction modeling. T2K data continue to prefer the normal mass ordering and upper octant of sin^{2}θ_{23} with a near-maximal value of the charge-parity violating phase with best-fit values in the normal ordering of δ_{CP}=-2.18_{-0.47}^{+1.22}, sin^{2}θ_{23}=0.559_{-0.078}^{+0.018} and Δm_{32}^{2}=(+2.506_{-0.052}^{+0.039})×10^{-3} eV^{2}.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2025,
General search for supersymmetric particles in scenarios with compressed mass spectra using proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext> </mml:mtext> <mml:mi>TeV</mml:mi> </mml:math>
, Physical Review D, Vol: 112, ISSN: 2470-0010<jats:p> A general search is presented for supersymmetric particles (sparticles) in scenarios featuring compressed mass spectra using proton-proton collisions at a center-of-mass energy of 13 TeV, recorded with the CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>138</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:msup> <a:mi>fb</a:mi> <a:mrow> <a:mo>−</a:mo> <a:mn>1</a:mn> </a:mrow> </a:msup> </a:math> . A wide range of potential sparticle signatures are targeted, including pair production of electroweakinos, sleptons, and top squarks. The search focuses on events with a high transverse momentum system from initial-state-radiation jets recoiling against a potential sparticle system with significant missing transverse momentum. Events are categorized based on their lepton multiplicity, jet multiplicity, number of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>b</c:mi> </c:math> -tagged jets, and kinematic variables sensitive to the sparticle masses and mass splittings. The sensitivity extends to higher parent sparticle masses than previously probed at the LHC for production of pairs of electroweakinos, sleptons, and top squarks with mass spectra featuring small mass splittings (compressed mass spectra). The observed results demonstrate agreemen
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2025,
Search for charged lepton flavor violating <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>Z</mml:mi> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mi>Z</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> boson decays in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext> </mml:mtext> <mml:mi>TeV</mml:mi> </mml:math>
, Physical Review D, Vol: 112, ISSN: 2470-0010<jats:p> A search for flavor violating decays of the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>Z</a:mi> </a:math> boson to charged leptons is performed using data from proton-proton collisions at <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msqrt> <c:mi>s</c:mi> </c:msqrt> <c:mo>=</c:mo> <c:mn>13</c:mn> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:mi>TeV</c:mi> </c:math> collected with the CMS detector at the LHC, corresponding to an integrated luminosity of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mn>138</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:msup> <e:mi>fb</e:mi> <e:mrow> <e:mo>−</e:mo> <e:mn>1</e:mn> </e:mrow> </e:msup> </e:math> . Each of the decays <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>Z</g:mi> <g:mo stretchy="false">→</g:mo> <g:mi>e</g:mi>
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2025,
Measurement of event shapes in minimum-bias events from proton-proton collisions at √s = 13 TeV
, Physical Review D, Vol: 112, ISSN: 2470-0010A measurement of event-shape variables is presented, using a data sample produced in a special run with approximately one inelastic proton-proton collision per bunch crossing. The data were collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 64 μb<sup>−1</sup>. A number of observables related to the overall distribution of charged particles in the collisions are corrected for detector effects and compared with simulations. Inclusive event-shape distributions, as well as differential distributions of event shapes as functions of charged-particle multiplicity, are studied. None of the models investigated are able to satisfactorily describe the data. Moreover, there are significant features common amongst all generator setups studied, particularly showing data being more isotropic than any of the simulations. Multidimensional unfolded distributions are provided, along with their correlations.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for New Physics in Jet Multiplicity Patterns of Multilepton Events at sqrt[s]=13 TeV.
, Phys Rev Lett, Vol: 135A first search for beyond the standard model physics in jet multiplicity patterns of multilepton events is presented, using a data sample corresponding to an integrated luminosity of 138 fb^{-1} of 13 TeV proton-proton collisions recorded by the CMS detector at the LHC. The search uses observed jet multiplicity distributions in one-, two-, and four-lepton events to explore possible enhancements in jet production rate in three-lepton events with and without bottom quarks. The data are found to be consistent with the standard model expectation. The results are interpreted in terms of supersymmetric production of electroweak chargino-neutralino superpartners with cascade decays terminating in prompt hadronic R-parity violating interactions.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Observation of Orbitally Excited B_{c}^{+} States.
, Phys Rev Lett, Vol: 135The observation of a wide peaking structure in the B_{c}^{+}γ mass spectrum is reported using proton-proton collision data collected by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb^{-1}. The statistical significance over the background-only hypothesis exceeds seven standard deviations. The width of the observed structure is larger than the expectation from a single-peak hypothesis, and is well described by an effective minimal model consisting of two narrow peaks located at 6704.8±5.5±2.8±0.3 MeV/c^{2} and 6752.4±9.5±3.1±0.3 MeV/c^{2}. The uncertainty terms are statistical, systematic, and associated to the knowledge of the B_{c}^{+} mass, respectively. The measured peak locations are in line with theoretical predictions for lowest excited P-wave B_{c}^{+} states, marking the first observation of orbitally excited beauty-charm mesons and providing important insights into the internal dynamics of hadrons containing two heavy quarks.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Determination of the spin and parity of all-charm tetraquarks
, NATURE, Vol: 648, Pages: 58-+, ISSN: 0028-0836 -
Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Search for the decay B0→ ϕϕ
, Journal of High Energy Physics, Vol: 2025A search for the decay B<sup>0</sup>→ ϕϕ is made using pp collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb<sup>−1</sup>. No significant signal is observed, and an upper limit on the branching fraction of 1.3 (1.4) × 10<sup>−8</sup> at 90 (95)% confidence level is set. This result supersedes the previous LHCb study and improves the upper limit by a factor of two.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2025,
Search for a new scalar resonance decaying to a Higgs boson and another new scalar particle in the final state with two bottom quarks and two photons in proton-proton collisions at TeV
, Journal of High Energy Physics, Vol: 2025A search is presented for a new scalar resonance, X, decaying to a standard model Higgs boson and another new scalar particle, Y, in the final state where the Higgs boson decays to a pair, while the Y particle decays to a pair of photons. The search is performed in the mass range 240–1000 GeV for the resonance X, and in the mass range 70–800 GeV for the particle Y, using proton-proton collision data collected by the CMS experiment at TeV, corresponding to an integrated luminosity of 132 fb<sup>-1</sup>. In general, the data are found to be compatible with the standard model expectation. Observed (expected) upper limits at 95% confidence level on the product of the production cross section and the relevant branching fraction are extracted for the X ? YH process, and are found to be within the range of 0.05–2.69 (0.08–1.94) fb, depending on m<inf>X</inf> and m<inf>Y</inf>. The most significant deviation from the background-only hypothesis is observed for X and Y masses of 300 and 77 GeV, respectively, with a local (global) significance of 3.33 (0.65) standard deviations.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2025,
Identification of tau leptons using a convolutional neural network with domain adaptation
, Journal of Instrumentation, Vol: 20, Pages: P12032-P12032<jats:title>Abstract</jats:title> <jats:p> A tau lepton identification algorithm, <jats:sc>DeepTau</jats:sc> , based on convolutional neural network techniques, has been developed in the CMS experiment to discriminate reconstructed hadronic decays of tau leptons (τ <jats:sub>h</jats:sub> ) from quark or gluon jets and electrons and muons that are misreconstructed as τ <jats:sub>h</jats:sub> candidates. The latest version of this algorithm, v2.5, includes domain adaptation by backpropagation, a technique that reduces discrepancies between collision data and simulation in the region with the highest purity of genuine τ <jats:sub>h</jats:sub> candidates. Additionally, a refined training workflow improves classification performance with respect to the previous version of the algorithm, with a reduction of 30–50% in the probability for quark and gluon jets to be misidentified as τ <jats:sub>h</jats:sub> candidates for given reconstruction and identification efficiencies. This paper presents the novel improvements introduced in the <jats:sc>DeepTau</jats:sc> algorithm and evaluates its performance in LHC proton-proton collision data at √( <jats:italic>s</jats:italic> ) = 13 and 13.6 TeV collected in 2018 and 2022 with integrated luminosities of 60 and 35 fb <jats:sup>-1</jats:sup> , respectively. Techniques to calibrate the performance of the τ <jats:sub>h</jats:sub> identification algorithm in simulation with respect
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Journal articleZsoldos S, Zito M, Zimmerman ED, et al., 2025,
Testing T2K’s Bayesian constraints with priors in alternate parameterisations
, European Physical Journal C, Vol: 85, ISSN: 1434-6044Bayesian analysis results require a choice of prior distribution. In long-baseline neutrino oscillation physics, the usual parameterisation of the mixing matrix induces a prior that privileges certain neutrino mass and flavour state symmetries. Here we study the effect of privileging alternate symmetries on the results of the T2K experiment. We find that constraints on the level of CP violation (as given by the Jarlskog invariant) are robust under the choices of prior considered in the analysis. On the other hand, the degree of octant preference for the atmospheric angle depends on which symmetry has been privileged.
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Journal articleCollaboration TCMS, 2025,
Search for heavy pseudoscalar and scalar bosons decaying to a top quark pair 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:mstyle/> <mml:mtext>TeV</mml:mtext> </mml:mrow> </mml:math>
, Reports on Progress in Physics, Vol: 88, Pages: 127801-127801, ISSN: 0034-4885<jats:title>Abstract</jats:title> <jats:p> A search for pseudoscalar or scalar bosons decaying to a top quark pair ( <jats:inline-formula> <jats:tex-math> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mtext>t</mml:mtext> </mml:mrow> <mml:mrow> <mml:mover> <mml:mtext>t</mml:mtext> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> </mml:mrow> </mml:math> </jats:inline-formula> ) in final states with one or two charged leptons is presented. The analyzed proton–proton collision data was recorded at <jats:inline-formula> <jats:tex-math> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mtext>TeV</mml:mtext> </mml:mrow
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2025,
Search for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>γ</mml:mi> <mml:mi>H</mml:mi> </mml:math> production and constraints on the Yukawa couplings of light quarks to the Higgs boson
, Physical Review D, Vol: 112, ISSN: 2470-0010<jats:p> A search for <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>γ</a:mi> <a:mi>H</a:mi> </a:math> production is performed with data from the CMS experiment at the LHC corresponding to an integrated luminosity of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mn>138</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> at a proton-proton center-of-mass collision energy of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mrow> <e:mn>13</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:mi>TeV</e:mi> </e:mrow> </e:math> . The analysis focuses on the topology of a boosted Higgs boson recoiling against a high-energy photon. The final states of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>H</g:mi> <g:mo stretchy="false">→</g:mo>
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Study of charm mixing and CP violation with D0→ K±π∓π±π∓ decays
, Journal of High Energy Physics, Vol: 2025A study of charm mixing and CP violation in D<sup>0</sup> → K<sup>±</sup>π<sup>∓</sup>π<sup>±</sup>π<sup>∓</sup> decays is performed using data collected by the LHCb experiment in proton-proton collisions from 2015 to 2018, corresponding to an integrated luminosity of 6 fb<sup>−1</sup>. The ratio of promptly produced D<sup>0</sup> → K<sup>+</sup>π<sup>−</sup>π<sup>+</sup>π<sup>−</sup> to D<sup>0</sup> → K<sup>−</sup>π<sup>+</sup>π<sup>−</sup>π<sup>+</sup> decay rates is measured as a function of D<sup>0</sup> decay time, both inclusive over phase space and in bins of phase space. Taking external inputs for the D0−D¯0 mixing parameters x and y allows constraints to be obtained on the hadronic parameters of the charm decay. When combined with previous measurements from charm-threshold experiments and at LHCb, improved knowledge is obtained for these parameters, which is valuable for studies of the angle γ of the Unitarity Triangle. An alternative analysis is also performed, in which external inputs are taken for the hadronic parameters, and the mixing parameters are determined, including ∆x and ∆y, which are nonzero in the presence of CP violation. It is found that x=0.85−0.24+0.15%, y=0.21−0.27+0.29%, ∆x = (−0.02 ± 0.04) % and Δy=0.02−0.03+0.04%. These results are consistent with previous measurements and the hypothesis of CP conservation.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Measurement of the B0→ ρ(770)0γ branching fraction
, Journal of High Energy Physics, Vol: 2025The ratio between the branching fractions of the B<sup>0</sup> → ρ(770)<sup>0</sup>γ and B<sup>0</sup> → K<sup>*</sup>(892)<sup>0</sup>γ decays is measured with proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb<sup>−1</sup>. The measured value is (Formula presented.) where the first uncertainty is statistical and the second systematic. The branching fraction for B<sup>0</sup>→ ρ(770)<sup>0</sup>γ decays is hence obtained as (Formula presented.) where the last uncertainty is due to the branching fraction of the normalisation mode. This result assumes that both the ρ(770)<sup>0</sup> and K<sup>*</sup>(892)<sup>0</sup> decays saturate the dihadron mass spectra considered in the analysis. It is consistent with the current world-average value and by far the most precise measurement to date.
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Journal articleZwalinski L, Zou W, Zormpa O, et al., 2025,
Estimation of backgrounds from jets misidentified as τ-leptons using the Universal Fake Factor method with the ATLAS detector
, European Physical Journal C, Vol: 85, ISSN: 1434-6044Processes with τ-leptons in the final state are important for Standard Model measurements and searches for physics beyond the Standard Model. The ATLAS experiment at the Large Hadron Collider observes τ-leptons produced in proton–proton collisions only through their decay products. Data analyses involving hadronically decaying τ-leptons face challenges due to backgrounds from jets misidentified as τ-leptons that are not modelled reliably by Monte Carlo simulations. Data-driven methods such as the fake-factor method allow such misidentified backgrounds to be predicted by measuring transfer factors, known as fake factors, in data from dedicated regions. This paper describes a refined technique for determining the fake factors, the Universal Fake Factor method. It evaluates the fake factors for a signal region by using fake factors from samples enriched in different sources of jets misidentified as τ-leptons (light-quark, gluon, b-quark, and pile-up jets). Each fake factor is calculated as a linear combination of fake factors measured in these different enriched samples. For the full Run 2 data set, the systematic uncertainty of the calculated fake factors, evaluated using W(μν) enriched event sample, ranges from 15 to 35% depending on the τ-lepton’s transverse momentum and charged-particle decay multiplicity.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for t-channel scalar and vector leptoquark exchange in the high-mass dimuon and dielectron spectra in proton-proton collisions at TeV
, Journal of High Energy Physics, Vol: 2025A search for t-channel exchange of leptoquarks (LQs) is performed in dimuon and dielectron spectra using proton-proton collision data collected at TeV with the CMS detector at the CERN LHC. The data correspond to an integrated luminosity of 138 fb<sup>−1</sup>. Eight scenarios are considered, in which up or down quarks couple to muons or electrons via a scalar or vector LQ exchange, for dilepton invariant masses above 500 GeV. The LQ masses are probed up to 5 TeV, beyond a regime probed by previous pair-production and single-production searches. The differential distributions of dilepton events are fit to templates that model the nonresonant LQ exchange and various standard model background processes. Limits are set on LQ-fermion coupling strengths for scalar and vector LQ masses in the 1–5 TeV range at 95% confidence level, establishing stringent limits on first- and second-generation LQs.
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Journal articleZwalinski L, Zou W, Zormpa O, et al., 2025,
Total Cost of Ownership and Evaluation of Google Cloud Resources for the ATLAS Experiment at the LHC
, Computing and Software for Big Science, Vol: 9The ATLAS Google Project was established as part of an ongoing evaluation of the use of commercial clouds by the ATLAS Collaboration, in anticipation of the potential future adoption of such resources by WLCG grid sites to fulfil or complement their computing pledges. Seamless integration of Google cloud resources into the worldwide ATLAS distributed computing infrastructure was achieved at large scale and for an extended period of time, and hence cloud resources are shown to be an effective mechanism to provide additional, flexible computing capacity to ATLAS. For the first time a total cost of ownership analysis has been performed, to identify the dominant cost drivers and explore effective mechanisms for cost control. Network usage significantly impacts the costs of certain ATLAS workflows, underscoring the importance of implementing such mechanisms. Resource bursting has been successfully demonstrated, whilst exposing the true cost of this type of activity. A follow-up to the project is underway to investigate methods for improving the integration of cloud resources in data-intensive distributed computing environments and reducing costs related to network connectivity, which represents the primary expense when extensively utilising cloud resources.
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