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Journal articleWalker T, Marchant AL, Bentine E, et al., 2026,
A high-flux source of cold strontium with a loading rate of 4×1010 atoms/s for open release
, Avs Quantum Science, Vol: 8We present a high-flux source of cold strontium atoms based on a two-dimensional magneto-optical trap (2D MOT) and a Zeeman slower. We use the source to load a 3D MOT in a separate science chamber, observing a loading rate of 4 × 10<sup>10</sup> atoms / s—to our knowledge, the highest reported loading flux for strontium. To characterize the vacuum pressure in the science chamber, we load the atoms into a magnetic trap and measure a lifetime of between 8 and 24 s, depending on the oven temperature. Finally, we characterize the atom flux and velocity distributions from the oven and from the 2D MOT source, finding reasonable agreement with models in the free molecular flow regime. Our results show that it is possible to readily produce a cold strontium flux at comparable levels to those of alkali species, at oven temperatures compatible with long-term operation, and at vacuum pressures suitable for state-of-the-art quantum experiments. We make our design available at no cost to benefit researchers in the quantum community.
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Journal articleMorgan K, Azuma T, Baptista G, et al., 2026,
Transition-Edge Sensor Spectrometer for Precision Spectroscopy of Antiprotonic Atoms
, IEEE Transactions on Applied Superconductivity, Vol: 36, ISSN: 1051-8223antiProtonic Atom X-ray (PAX) spectroscopy is an experiment that aims to test strong-field quantum electrodynamics (QED) effects by performing high-precision X-ray spectroscopy of antiprotonic atoms. PAX will use a low-energy antiproton beam provided by the Extra Low ENergy Antiproton (ELENA) ring at the European Organization for Nuclear Research (CERN) to create antiprotonic atoms. A superconducting transition-edge sensor (TES) spectrometer will be used to measure the energy of transitions between circular Rydberg states in these atoms. The energy range of interest for the experiment spans 50 keV to 250 keV, and the desired precision for measuring the centroids of the emission lines is 10^{-5}. The spectrometer for PAX is intended to have four 96-pixel TES arrays and will be read out with a microwave superconducting quantum interference device (SQUID) multiplexer. As a step toward building the full instrument, we built a scaled-down version of the spectrometer that was installed at the TEst Line for Machine And Antimatter eXperiments (TELMAX) facility at ELENA in April 2025. The purpose of this deployment was to make an observation of X-ray emission by antiprotonic atoms and to better understand the effect of the pionic charged particle background due to antiproton annihilation on the performance of the TES array. This pilot spectrometer had an array of 60 TES pixels in a compact adiabatic demagnetization refrigerator cryostat. The sensors were read out with a microwave SQUID multiplexer. Each pixel consisted of a molybdenum/gold bilayer TES with a coplanar gold “landing pad” for a bulk tin absorber that was attached by an epoxy joint. We discuss the design of the TES pixels, the microwave SQUID readout, and the cryogenic platform. Finally, we present calibration data obtained at TELMAX using radioactive sources to assess the performance of the spectrometer in the antiproton beam-off condition.
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Journal articleBelyaev A, Gevorgyan A, Hayrapetyan A, et al., 2026,
System-size dependence of charged-particle suppression in ultrarelativistic nucleus-nucleus collisions
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 880, ISSN: 0370-2693High-energy partons lose energy while propagating through the hot, strongly interacting medium produced in ultrarelativistic nucleus-nucleus collisions, leading to a suppression of particle production at high transverse momentum (p <inf>T</inf>). The dependence of this energy loss on the size of the colliding nuclear system has yet to be firmly established experimentally. This Letter presents a systematic study of charged-particle suppression across four different nucleus-nucleus collision systems using nuclear modification factors (R <inf>AA</inf>) measured by the CMS Collaboration at the CERN LHC. Previous CMS measurements of R <inf>AA</inf> in oxygen-oxygen, xenon-xenon, and lead-lead collisions are recast with identical p <inf>T</inf> intervals and are complemented by the first measurement of the charged-particle R <inf>AA</inf> in neon-neon collisions at [b]s<inf>NN</inf>=5.36TeV. The neon-neon data correspond to an integrated luminosity of 0.76nb<sup>−1</sup>. The R <inf>AA</inf> in all collision systems examined show similar qualitative trends as a function of p <inf>T</inf>, but have a magnitude which is ordered with the nucleon number A . The R <inf>AA</inf> feature a downward slope at low p <inf>T</inf>, a local minimum at around 5–7GeV, and an upward slope with increasing p <inf>T</inf>. The R <inf>AA</inf> are also compared in terms of A <sup>1/3</sup>, which is proportional to the nuclear radius. Models including only initial-state nuclear effects fail to reproduce the observed trends, whereas energy loss models reproduce the trends in the region p<inf>T</inf>'9.6GeV.
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Journal articleAaij R, Abdelfatah M, Abdelmotteleb ASW, et al., 2026,
Search for the Lepton-Flavor Violating Decays B^{+}→π^{+}μ^{±}e^{∓}.
, Phys Rev Lett, Vol: 137The first search for the lepton-flavor violating decays B^{+}→π^{+}μ^{±}e^{∓} in proton-proton collisions is presented, using data collected by the LHCb experiment between 2011 and 2018, corresponding to an integrated luminosity of 9 fb^{-1}. No significant signal is observed and an upper limit on the branching fraction is set at B(B^{+}→π^{+}μ^{±}e^{∓})<1.8×10^{-9} at the 90% confidence level, 2 orders of magnitude more restrictive than the most stringent upper limit to date. This is the first constraint on lepton-flavor violating b→d quark transitions at the LHC and also sets the most stringent upper limits to date on b→dμ^{±}e^{∓} transitions. Limits on left-handed and scalar scenarios beyond the standard model are also reported.
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Journal articleAaij R, Abdelfatah M, Abdelmotteleb ASW, et al., 2026,
CP Violation Analysis of Local and Nonlocal Amplitudes in the B[over ¯]^{0}→K[over ¯]^{*0}μ^{+}μ^{-} Decay.
, Phys Rev Lett, Vol: 137A search for CP violation in the B[over ¯]^{0}→K[over ¯]^{*0}μ^{+}μ^{-} decay is performed using proton-proton collision data collected by the LHCb experiment during Run 1 and Run 2, corresponding to an integrated luminosity of 8.4 fb^{-1}. The analysis exploits the full angular distribution of the decay, providing sensitivity to CP-violating effects in both vector and axial-vector contributions to this flavor-changing neutral-current process. The complex Wilson coefficients are determined within the weak effective theory through an unbinned maximum-likelihood fit to the angular observables, incorporating nonlocal hadronic amplitudes across the full dimuon mass spectrum. The precision of the CP-violation observables is improved by an order of magnitude relative to previous measurements, with the imaginary parts of the Wilson coefficients now determined more precisely than the real parts. No significant CP violation is observed, and the results are consistent with the standard model.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for soft unclustered energy patterns produced in association with a W or Z boson in proton-proton collisions at s=13TeV
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 879, ISSN: 0370-2693A search for a Higgs boson produced in association with a W or Z boson and decaying via a soft unclustered energy pattern (SUEP) is presented. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 138fb<sup>−1</sup> collected between 2016 and 2018 at the LHC. Final states with a leptonic W or Z boson decay associated with a high multiplicity of low-momentum charged particles are explored for the first time. The results show no significant excess over the standard model background expectation. Limits are set on the production cross section of a Higgs boson that decays to a SUEP, for a range of parameters of the SUEP model. Material is provided to facilitate further interpretation of the results.
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Journal articleWaiton J, Bateman J, Evans JJ, et al., 2026,
A sterile-neutrino search using data from the MicroBooNE liquid-argon time projection chamber performed in an undergraduate teaching laboratory
, European Journal of Physics, Vol: 47, ISSN: 0143-0807Fundamental particle physics is a key part of an undergraduate physics curriculum, but can be challenging to incorporate into teaching laboratories. We present an undergraduate laboratory experiment that enables students to work with real data from the MicroBooNE liquid-argon time projection chamber to search for the existence of a sterile neutrino: a new, fourth, neutrino state. This search has galvanised physicists for decades, as the existence of sterile neutrinos could play a critical role in understanding fundamental processes in the early Universe, provide viable dark matter candidates, and offer a natural explanation for the origin of neutrino masses. From an experimental point of view, anomalies observed in several neutrino experiments provide tantalising hints of their existence. The analysis presented here, whilst based on real data, has been adapted as a pedagogical tool for an undergraduate teaching laboratory, in which students are asked to develop an understanding of neutrino oscillation theory, analyse a MicroBooNE data sample, and apply statistical methods to search for a potential sterile neutrino. The analysis incorporates machine learning techniques to improve event classification. Students are encouraged to explore these and other methods to optimise their results.
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Journal article, 2026,
Machine-learning techniques for model-independent searches in dijet final states
, Machine Learning: Science and Technology, Vol: 7, Pages: 045008-045008<jats:title>Abstract</jats:title> <jats:p> Anomaly detection methods used in a recent search for new phenomena by CMS at the CERN LHC are presented. The methods use machine learning to detect anomalous jets produced in the decay of new massive particles without depending on a specific theory model. The effectiveness of these approaches in enhancing sensitivity to various simulated signal samples is studied and compared using data collected in proton–proton collisions at a center-of-mass energy of 13 <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:mstyle scriptlevel="0"/> <mml:mtext>TeV</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> </jats:inline-formula> . In an example analysis, the capabilities of anomaly detection methods are further demonstrated by identifying large-radius jets consistent with Lorentz-boosted hadronically decaying top quarks in a model-agnostic framework. </jats:p>
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for a boosted Higgs boson decaying to bottom quark pairs in association with a W or Z boson in proton-proton collisions at s=13TeV
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 879, ISSN: 0370-2693A search is conducted for standard model Higgs bosons with large transverse momentum ( p <inf>T</inf>) decaying to bottom quark pairs and produced in association with a hadronically decaying W or Z boson at the LHC. The result is based on a dataset of proton-proton collisions at a center-of-mass energy of 13 TeVcollected with the CMS detector in 2016–2018, corresponding to an integrated luminosity of 138fb<sup>−1</sup>. Boosted Higgs, W, and Z boson decays are reconstructed using large-radius jets with p <inf>T</inf> > 450 GeV and identified with heavy-flavor classifiers based on a graph convolutional neural network. The observed signal strength relative to the standard model expectation is μ=0.72<inf>−0.71</inf><sup>+0.75</sup> including statistical and systematic uncertainties.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
Evidence for the Rare Decay B^{+}→Λ[over ¯]pμ^{+}μ^{-}.
, Phys Rev Lett, Vol: 137A search for the rare decay B^{+}→Λ[over ¯]pμ^{+}μ^{-} is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of sqrt[s]=13 TeV, corresponding to an integrated luminosity of 5.4 fb^{-1}. An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of m(Λ[over ¯]p)<2.8 GeV/c^{2}. The branching fraction is measured to be B_{low}(B^{+}→Λ[over ¯]pμ^{+}μ^{-})=(1.70_{-0.56}^{+0.65}(stat)±0.17(syst)±0.14(ext))×10^{-8}, where the last uncertainty is due to external inputs on B(B^{+}→J/ψΛ[over ¯]p)×B(J/ψ→μ^{+}μ^{-}). With no significant signal observed in the high m(Λ[over ¯]p) region above 2.8 GeV/c^{2}, an upper limit is set to be B_{high}(B^{+}→Λ[over ¯]pμ^{+}μ^{-})<2.8(3.7)×10^{-9} at the 90% (95%) confidence level.
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Journal articleAaij R, Abdelfatah M, Abdelmotteleb ASW, et al., 2026,
Test of Lepton Flavor Universality with B^{0}→K^{*0}ℓ^{+}ℓ^{-} Decays at Large Dilepton Invariant Mass.
, Phys Rev Lett, Vol: 137Muon-electron universality is tested in B^{0}→K^{*0}ℓ^{+}ℓ^{-} decays, in the dilepton-invariant-mass region above the ψ(2S) resonance. The analysis uses beauty mesons produced in proton-proton collisions recorded by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb^{-1}. The ratio of branching fractions between the muon and electron channels R_{K^{*0}} is measured to be 1.08_{-0.12}^{+0.14}(stat)±0.07(syst) for a dilepton-invariant-mass squared above 14.0 GeV^{2}/c^{4}, consistent with the standard model prediction. This result represents the most precise measurement of R_{K^{*0}} in this region and the first such measurement performed at a hadron collider.
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Journal articleAprile E, Aalbers J, Abe K, et al., 2026,
Light Dark Matter Search with 7.8 Tonne-Year of Ionization-Only Data in XENONnT
, Physical Review Letters, Vol: 137, ISSN: 0031-9007<jats:p> We report on a blinded search for dark matter (DM) using ionization-only (S2-only) signals in XENONnT with a total exposure of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mn>7.83</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mtext>Tonne-year</a:mtext> </a:mrow> </a:math> over 579 days in three science runs. Dedicated background suppression techniques and the first complete S2-only background model in XENONnT provide sensitivity to nuclear recoils of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mo stretchy="false">[</c:mo> <c:mn>0.5</c:mn> <c:mo>,</c:mo> <c:mn>5.0</c:mn> <c:mo stretchy="false">]</c:mo> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:msub> <c:mrow> <c:mi>keV</c:mi> </c:mrow> <c:mrow> <c:mi>nr</c:mi> </c:mrow> </c:msub> </c:mrow> </c:math> and electronic recoils of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"&
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for heavy resonances decaying into two Higgs bosons in the $${\text {b}}\bar{\textrm{b}}\tau ^{+}\tau ^{-}$$ final state in proton–proton collisions at $$\sqrt{s} = 13\,\text {Te\hspace{-.08em}V}$$
, The European Physical Journal C, Vol: 86<jats:title>Abstract</jats:title> <jats:p> A search is presented for massive narrow-width resonances in the mass range of 1–4.5 <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$\,\text {Te\hspace{-.08em}V}$$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mspace/> <mml:mtext>Te</mml:mtext> <mml:mspace/> <mml:mtext>V</mml:mtext> </mml:mrow> </mml:math> </jats:alternatives> </jats:inline-formula> , decaying into pairs of Higgs bosons (HH). The search uses proton–proton collision data at a center-of-mass energy of 13 <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$\,\text {Te\hspace{-.08em}V}$$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mspace/> <mml:mtext>Te</mml:mtext> <mml:mspace/> <mml:mtext>V</mml:mtext> </mml:mrow> </mml:math> </jats:alternatives> </jats:inline-formula> collected with the CMS detector at the CERN LHC during 2016–2018, corresponding to an integrated luminosity of 138 <jats:inline-formula>
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Journal articleAbbaslu S, Alrahman FA, Abud AA, et al., 2026,
Reconstruction of atmospheric neutrinos in DUNE’s horizontal-drift far-detector module
, The European Physical Journal C, Vol: 86<jats:title>Abstract</jats:title> <jats:p>This paper reports on the capabilities in reconstructing and identifying atmospheric neutrino interactions in one of the Deep Underground Neutrino Experiment’s (DUNE) far detector modules, a liquid argon time projection chamber (LArTPC) with horizontal drift (FD-HD) of ionization electrons. The reconstruction is based upon the workflow developed for DUNE’s long-baseline oscillation analysis, with some necessary machine-learning models’ retraining and the addition of features relevant only to atmospheric neutrinos such as the neutrino direction reconstruction. Where relevant, the impact of the detection of the charged particles of the hadronic system is emphasized, and comparisons are carried out between the case when lepton-only information is considered in the reconstruction (as is the case for many neutrino oscillation experiments), versus when all particles identified in the LArTPC were included. Three neutrino direction reconstruction methods have been developed and studied for the atmospheric analyses: using lepton-only information, using all reconstructed particles, and using only correlations from reconstructed hits. The results indicate that incorporating more than just lepton information significantly improves the resolution of both neutrino direction and energy reconstruction. The angle reconstruction algorithms developed in this work result in no strong dependence on particle direction for reconstruction efficiencies or neutrino flavor identification. This comprehensive review of the reconstruction of atmospheric neutrinos in DUNE’s FD-HD LArTPC is the first step towards developing a first neutrino oscillation sensitivity analysis, which will ready DUNE for its first measurements.</jats:p>
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Journal articleAaij R, Abdelmotteleb ASW, Beteta CA, et al., 2026,
Observation of CP Violation in B^{0}→J/ψρ(770)^{0} Decays.
, Phys Rev Lett, Vol: 137The time-dependent CP asymmetry in B^{0}→J/ψρ(770)^{0} decays is measured using proton-proton collision data corresponding to an integrated luminosity of 6 fb^{-1}, collected with the LHCb detector at a center-of-mass energy of 13 TeV during the years 2015-2018. The CP-violation parameters for this process are determined to be 2β_{cc[over ¯]d}^{eff}=0.710±0.084±0.051 rad and |λ|=1.019±0.034±0.024, where the first uncertainty is statistical and the second systematic. This constitutes the first observation of time-dependent CP violation in B^{0}→J/ψρ(770)^{0} decays. Assuming approximate SU(3) flavor symmetry, these results are combined with the previous consistent LHCb measurement to set the most stringent constraint on the penguin contribution, Δϕ_{s}, to the CP-violating phase ϕ_{s} in B_{s}^{0}→J/ψϕ(1020) decays, yielding Δϕ_{s}=5.0±4.6 mrad.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for exotic Higgs boson decays H → 𝒜𝒜 with 𝒜 → γγ in events with a semi-merged topology in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV
, Journal of High Energy Physics, Vol: 2026<jats:title> A <jats:sc>bstract</jats:sc> </jats:title> <jats:p> A search for exotic Higgs boson decays H <jats:italic>→</jats:italic> 𝒜𝒜, with 𝒜 → γγ is presented, using events with a semi-merged topology. One of the hypothetical particles, 𝒜, is assumed to decay promptly into a semi-merged diphoton system reconstructed as a single photon-like object, while the other 𝒜 decays into two resolved photons. The search is performed using proton-proton collision data collected by the CMS experiment at <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \sqrt{s}=13 $$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> </mml:math> </jats:alternatives> </jats:inline-formula> TeV, corresponding to an integrated luminosity of 138 fb <jats:sup> <jats:italic>−</jats:italic> 1 </jats:sup> . The data agree with the standard model background expectation. Upper limits are set on the product of the Higgs boson production cross section and the branching fraction, <jats:italic>σ</jats:italic> (pp <jats:italic>→</jats:italic> H) ℬ(H
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Journal articleAaij R, Abdelfatah M, Abdelmotteleb ASW, et al., 2026,
Observation of the Doubly Charmed Baryon Ξ_{cc}^{+} with the LHCb Run 3 Detector.
, Phys Rev Lett, Vol: 137The first observation of the doubly charmed baryon Ξ_{cc}^{+} is reported through its decay to the Λ_{c}^{+}K^{-}π^{+} final state, with a statistical significance exceeding seven standard deviations. The observation is made using proton-proton collision data collected in 2024 with the LHCb Run 3 detector at a center-of-mass energy of 13.6 TeV, corresponding to a total integrated luminosity of 6.9 fb^{-1}. The Ξ_{cc}^{+} mass is measured to be 3619.97±0.83±0.26_{-1.30}^{+1.90} MeV/c^{2}, where the first uncertainty is statistical, the second is systematic, and the third is due to the unknown Ξ_{cc}^{+} lifetime, which is assumed to lie in the range 15-160 fs with a baseline value of 45 fs. The difference between the masses of the Ξ_{cc}^{+} and Ξ_{cc}^{++} baryons is determined to be -1.77±0.84±0.15_{-1.30}^{+1.90} MeV/c^{2}. This is the first observation of a new particle made with the LHCb Run 3 detector.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
Comprehensive Analysis of the B^{0}→K^{*0}μ^{+}μ^{-} Decay.
, Phys Rev Lett, Vol: 137An analysis of the B^{0}→K^{*0}(→K^{+}π^{-})μ^{+}μ^{-} decay is presented using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 8.4 fb^{-1}. The full set of CP-averaged and CP-asymmetric angular observables is determined in bins of the invariant mass squared of the dimuon system, as well as the branching fraction relative to the B^{0}→J/ψ(→μ^{+}μ^{-})K^{+}π^{-} decay. For the first time, the full set of observables pertaining to the K^{+}π^{-} S-wave contribution to the final state are presented and consideration is given to effects arising from the mass of the muons. The extracted CP-asymmetry observables show no significant deviations from zero. The measurements of the CP-averaged observables and the branching fractions continue to exhibit the pattern of tensions with the standard model predictions that have been seen in previous analyses that use part of the dataset considered in this Letter.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Measurement of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>B</mml:mi> </mml:math> meson production fraction ratios in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msqrt> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </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:mrow> </mml:math> using open-charm and charmonium decays
, Physical Review D, Vol: 114, ISSN: 2470-0010<jats:p> Production fraction ratios of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>B</a:mi> <a:mo>+</a:mo> </a:msup> </a:math> , <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:math> , and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msubsup> <e:mi>B</e:mi> <e:mi>s</e:mi> <e:mn>0</e:mn> </e:msubsup> </e:math> mesons are measured in proton-proton collisions at <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mrow> <g:msqrt> <g:mrow> <g:mi>s</g:mi> </g:mrow> </g:msqrt> <g:mo>=</g:mo> <g:mn>13</g:mn> <g:mtext> </g:mtext> <g:mtext> </g:mtext> <g:mi>TeV</g:mi> </g:mrow> </g:math> using a special dataset recorded in 2018 with high-rate
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2026,
Improved branching-fraction measurements of Bs0→KS0h+h′− decays and first observation of Bs0→KS0K+K−
, Journal of High Energy Physics, Vol: 2026This paper presents a study of the charmless three-body decays Bs0→KS0h+h′− (where h<sup>(</sup>′<sup>)</sup> = π, K), using a sample of pp collision data collected by the LHCb experiment during Runs 1 and 2 of the LHC, corresponding to an integrated luminosity of 9 fb<sup>−1</sup>. The decay Bs0→KS0K+K− is observed for the first time, and the following ratios of branching fractions are measured: (Formula presented.) where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the Bs0 and B<sup>0</sup> mesons, respectively.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for the pair production of long-lived supersymmetric partners of the tau lepton in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026Gauge-mediated supersymmetry-breaking models provide a strong motivation to search for a supersymmetric partner of the tau lepton (stau) with a macroscopic lifetime. Long-lived stau decays produce tau leptons that are displaced from the primary proton-proton interaction vertex, leading to an unconventional signature. This paper presents a search for the direct production of long-lived staus decaying within the CMS tracker volume in proton-proton collisions at s=13 TeV, performed for the first time with an identification algorithm based on a graph neural network dedicated to displaced tau leptons. The data sample, corresponding to an integrated luminosity of 138 fb<sup>−1</sup>, was recorded with the CMS experiment at the CERN LHC between 2016 and 2018. This search excludes, at 95% confidence level, stau masses, mτ~, in the 126–260 (90–425) GeV range for a proper decay length of 50 mm in the maximally mixed (mass-degenerate) scenario, while for mτ~=200 GeV, stau proper decay lengths are excluded in the range 21–94 (6–333) mm. These results improve the exclusion limits compared to previous searches, and extend the parameter space explored in the context of supersymmetry.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Measurement of the Υ(1S), Υ(2S), and Υ(3S) differential cross sections in pp collisions at s=13.6 TeV
, Journal of High Energy Physics, Vol: 2026The production cross sections of the Υ(1S), Υ(2S), and Υ(3S) mesons are measured in proton-proton collisions at s=13.6 TeV, using a data sample collected in 2022 by the CMS experiment and corresponding to an integrated luminosity of 37.4 fb<sup>−1</sup>. The measurement is performed in the μ<sup>+</sup>μ<sup>−</sup> decay channels, differentially as a function of transverse momentum in the 20–200 GeV range, in the |y| < 0.6 and 0.6 < |y| < 1.2 rapidity intervals.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Measurement of the jet mass in hadronic decays of boosted W bosons at 13 TeV and extraction of the W boson mass
, Journal of High Energy Physics, Vol: 2026The jet mass of W bosons decaying to a quark-antiquark pair is measured in W+jets events from proton-proton collisions at a center-of-mass energy of 13 TeV. The data used were collected by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 138 fb<sup>−1</sup>. Hadronic decays of W bosons with high momenta produce strongly collimated decay products due to the large Lorentz boost, and are reconstructed as single large-radius jets. These jets have a characteristic substructure that is exploited to distinguish them from the large background of quark- and gluon-initiated jets. The jet mass is computed using the soft-drop algorithm, which suppresses soft wide-angle radiation that leads to a broadening of the jet mass distribution. For the first time, unfolded measurements are presented of the double-differential W+jets cross section as a function of the jet transverse momentum and soft-drop mass. From these distributions, the W boson mass is obtained, with a value of 80.83 ± 0.55 GeV in a scheme with mass-dependent width, achieving the smallest uncertainty available today from an all-jets final state at a hadron collider.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for single production of a vector-like T quark decaying to a top quark and a neutral scalar boson in the lepton+jets final state in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026A search for single production of a vector-like T quark with charge 2e/3, decaying to a top quark and a neutral scalar boson is presented. The boson can be a standard model Higgs boson (H) or a new scalar boson (ϕ). In the first case, a branching fraction of 25% is assumed for the decay T → tH, while in the second case the T quark is assumed to decay exclusively to tϕ. The top quark is identified via its lepton+jets decay, and the neutral boson via its decay into a bottom quark-antiquark pair. Final states with Lorentz-boosted topologies are considered and machine-learning techniques are exploited for optimal event classification. The analysis uses data collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb<sup>−1</sup> recorded at the CERN LHC in 2016–2018. Upper limits at 95% confidence level are set on the product of cross section and branching fraction for a T quark in a narrow-width approximation. They vary between 14.7 and 0.1 fb, for T quark masses in the range 1.3–3.0 TeV and ϕ boson masses in the range 25–250 GeV. These are the first exclusion limits set on the production of a single T quark decaying into a top quark and a new neutral scalar boson. For the decay channel into a top quark and a standard model Higgs boson, the results provide the best limits on production cross sections to date, for T quark masses above 2 TeV.
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Journal articleChekhovsky V, Hayrapetyan A, Makarenko V, et al., 2026,
Search for a new neutral gauge boson produced in association with one or two b jets and decaying into a pair of muons in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026A search for a new neutral gauge boson, Z′, produced in association with one or two jets, including at least one b jet, and decaying into a pair of muons is presented. The analysis uses proton-proton collision data collected with the CMS detector at s=13 TeV, corresponding to an integrated luminosity of 138 fb<sup>−1</sup>. No significant deviation from background expectations is observed. Upper limits at 95% confidence level on the product of cross section, branching fraction to dimuons, acceptance, and efficiency, from 0.2 to 2 fb, are set for Z′ boson masses between 125 and 350 GeV. Process-dependent products of acceptance and efficiency, and model-independent limits on the signal yield are provided. These are the only results to date in the 125–200 GeV mass range and the most stringent for b quark fusion production modes in the 200–350 GeV range, complementing inclusive Z′ boson searches.
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Journal articleAbe K, Abe S, Asaoka Y, et al., 2026,
Search for Diffuse Supernova Neutrino Background with 956.2 Days of Super-Kamiokande Gadolinium Dataset
, Astrophysical Journal, Vol: 1005, ISSN: 0004-637XWe report the search result for the Diffuse Supernova Neutrino Background (DSNB) in neutrino energies beyond 9.3 MeV in the gadolinium-loaded Super-Kamiokande (SK) detector with a 22,500 × 956.2 m<sup>3</sup> day exposure. Starting in the summer of 2020, SK introduced 0.01% gadolinium (Gd) by mass into its ultrapure water to enhance the neutron capture signal, termed the SK-VI phase. This was followed by a 0.03% Gd-loading in 2022, a phase referred to as SK-VII. We then conducted a DSNB search using 552.2 days of SK-VI data and 404.0 days of SK-VII data through 2023 September. This analysis includes several new features, such as two new machine learning neutron detection algorithms with Gd, an improved atmospheric background-reduction technique, and two parallel statistical approaches. No significant excess over background predictions was found in a DSNB spectrum-independent analysis, and 90% confidence level (C.L.) upper limits on the astrophysical electron antineutrino flux were set. Additionally, a spectral fitting result exhibited a ∼1.2σ disagreement with a null DSNB hypothesis, comparable to a previous result from 5823 days of all SK pure-water phases.
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Journal articleAad G, Aakvaag E, Abbott B, et al., 2026,
Search for long-lived particles using displaced vertices of oppositely charged leptons in 140fb−1 of pp collisions at s=13 TeV with the ATLAS detector
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 878, ISSN: 0370-2693A search is presented for long-lived particles decaying into an oppositely charged lepton pair, μ<sup>+</sup>μ<sup>−</sup>, e<sup>+</sup>e<sup>−</sup>, or e <sup> ± </sup> μ <sup>∓</sup>, that form a vertex within the inner tracking system of the ATLAS detector at the Large Hadron Collider, displaced from the primary proton–proton interaction region. The analysis uses the 140 fb<sup>−1</sup> of Run-2 data collected at s=13 TeV by the ATLAS experiment in 2015–2018. The results of the analysis are interpreted in the context of three benchmark models covering masses from 0.1 to 2.2 TeV and a range of mean proper lifetimes times the speed of light from 1 to 10 000 mm. The first model is a generic Z ′ boson pair-produced by a new heavy scalar, with the Z ′ decaying into lepton pairs. The remaining two models are R -parity violating supersymmetric models in which the lightest neutralino χ˜<inf>1</inf><sup>0</sup> decays into ℓ<sup>+</sup>ℓ<sup><sup>′</sup><sup>−</sup></sup>ν (ℓ,ℓ<sup>′</sup>=e, μ). The models differ by the mode of production of the χ˜<inf>1</inf><sup>0</sup>, which can be produced via the decay of pairs of gluinos or of pairs of charginos and neutralinos (χ˜<inf>1</inf><sup>±</sup>χ˜<inf>1</inf><sup>0</sup>, χ˜<inf>1</inf><sup>±</sup>χ˜<inf>2</inf><sup>0</sup>, or χ˜<inf>2</inf><sup>0</sup>χ˜<inf>1</inf><sup>0</sup>). Although each benchmark sample includes pair-produced LLPs, only a single vertex is required to be reconstructed. No dilepton displaced v
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Search for heavy long-lived charged particles with level-1 trigger scouting data from proton-proton collisions at s=13.6TeV
, Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Vol: 878, ISSN: 0370-2693A search for heavy long-lived charged particles at the LHC is presented. Particles traversing the CMS muon detector across several bunch crossings are searched for using a data sample of proton-proton collisions at s=13.6TeV collected with the CMS detector in 2024, corresponding to an integrated luminosity of 3.7 fb<sup>−1</sup>. This is the first search using the novel level-1 trigger scouting data set collected without any trigger selection, allowing correlations between bunch crossings to be analyzed. The results are interpreted as upper limits on the cross sections of several benchmark processes with pair production of heavy long-lived charged particles. Upper limits on the fiducial cross section of a heavy long-lived charged particle with p<inf>T</inf>>500GeV and | η | < 0.83 are also set in different ranges of β=v/c. This analysis is a proof of concept for the level-1 trigger data scouting system and complements existing searches for heavy long-lived charged particles by extending the sensitivity to lower β values.
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Journal articleBenedikt M, Zimmermann F, Auchmann B, et al., 2026,
Correction to: Future Circular Collider Feasibility Study Report: Volume 1 Physics, Experiments, Detectors (The European Physical Journal C, (2025), 85, 12, (1468), 10.1140/epjc/s10052-025-15077-x)
, European Physical Journal C, Vol: 86, ISSN: 1434-6044The published article has been revised. The name of the author Pramod Sharma was previously incorrect and appeared as Pramond Sharma. The original article has been corrected.
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Journal articleHayrapetyan A, Makarenko V, Tumasyan A, et al., 2026,
Combination of searches for heavy vector boson resonances in proton-proton collisions at s=13 TeV
, Journal of High Energy Physics, Vol: 2026A combined statistical analysis of searches for heavy vector boson resonances decaying into pairs of W, Z, or Higgs bosons, as well as into quark pairs qq¯bb¯tt¯tb¯ or lepton pairs ℓ+ℓ−ℓν¯, with ℓ = e, μ, τ, is presented. The results are based on proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb<sup>−1</sup>, collected by the CMS experiment from 2016 to 2018. No significant deviation from the expectations of the standard model is observed. The results are interpreted in the simplified heavy vector triplet (HVT) framework, setting 95% confidence level upper limits on the production cross sections and on the coupling strengths of the HVT bosons to standard model particles. The results exclude HVT resonances with masses below 5.5 TeV in a weakly coupled scenario, below 4.8 TeV in a strongly coupled scenario, and up to 2.0 TeV in the case of production via vector boson fusion. The combination provides the most stringent constraints to date on new phenomena predicted by the HVT model.
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