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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Study of Λ_{b}^{0} and Ξ_{b}^{0} Decays to Λh^{+}h^{'-} and Evidence for CP Violation in Λ_{b}^{0}→ΛK^{+}K^{-} Decays.
, Phys Rev Lett, Vol: 134A study of Λ_{b}^{0} and Ξ_{b}^{0} decays to Λh^{+}h^{'-} (h^{(')}=π,K) is performed using pp collision data collected by the LHCb experiment during LHC Runs 1-2, corresponding to an integrated luminosity of 9 fb^{-1}. The branching fractions for these decays are measured using the Λ_{b}^{0}→Λ_{c}^{+}(→Λπ^{+})π^{-} decay as a control channel. The decays Λ_{b}^{0}→Λπ^{+}π^{-} and Ξ_{b}^{0}→ΛK^{-}π^{+} are observed for the first time. For decay modes with sufficient signal yields, CP asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for CP violation in the Λ_{b}^{0}→ΛK^{+}K^{-} decay, interpreted as originating primarily from an asymmetric Λ_{b}^{0}→N^{*+}K^{-} decay amplitude. The measured CP asymmetries for other decays are compatible with zero.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
First Evidence for Direct CP Violation in Beauty to Charmonium Decays.
, Phys Rev Lett, Vol: 134The CP asymmetry and branching fraction of the Cabibbo-Kobayashi-Maskawa-suppressed decay B^{+}→J/ψπ^{+} are precisely measured relative to the favored decay B^{+}→J/ψK^{+} using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.4 fb^{-1} recorded at a center-of-mass energy of 13 TeV during 2016-2018. The results of the CP asymmetry difference and branching fraction ratio are ΔA^{CP}≡A^{CP}(B^{+}→J/ψπ^{+})-A^{CP}(B^{+}→J/ψK^{+})=(1.29±0.49±0.08)×10^{-2}, R_{π/K}≡[B(B^{+}→J/ψπ^{+})/B(B^{+}→J/ψK^{+})]=(3.852±0.022±0.018)×10^{-2}, where the first uncertainties are statistical and the second are systematic. A combination with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012 yields ΔA^{CP}=(1.42±0.43±0.08)×10^{-2} and R_{π/K}=(3.846±0.018±0.018)×10^{-2}. The combined ΔA^{CP} value deviates from zero by 3.2 standard deviations, providing the first evidence for direct CP violation in the amplitudes of beauty decays to charmonium final states.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Observation of the Open-Charm Tetraquark Candidate T_{cs0}^{*}(2870)^{0} in the B^{-}→D^{-}D^{0}K_{S}^{0} Decay.
, Phys Rev Lett, Vol: 134An amplitude analysis of B^{-}→D^{-}D^{0}K_{S}^{0} decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 9 fb^{-1}, collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. A resonant structure of spin-parity 0^{+} is observed in the D^{0}K_{S}^{0} invariant-mass spectrum with a significance of 5.3σ. The mass and width of the state, modeled with a Breit-Wigner line shape, are determined to be 2883±11±8 MeV/c^{2} and 87_{-47}^{+22}±17 MeV, respectively, where the first uncertainties are statistical and the second systematic. These properties and the quark content are consistent with those of the open-charm tetraquark candidate T_{cs0}^{*}(2870)^{0} observed previously in the D^{+}K^{-} final state of the B^{-}→D^{-}D^{+}K^{-} decay. This result confirms the existence of the T_{cs0}^{*}(2870)^{0} state in a new decay mode. The T_{cs1}^{*}(2900)^{0} state, reported in the B^{-}→D^{-}D^{+}K^{-} decay, is also searched for in the D^{0}K_{S}^{0} invariant-mass spectrum of the B^{-}→D^{-}D^{0}K_{S}^{0} decay, without finding evidence for it.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for light long-lived particles decaying to displaced jets in proton-proton collisions at √s = 13.6 TeV
, Reports on Progress in Physics, Vol: 88, ISSN: 0034-4885A search for light long-lived particles (LLPs) decaying to displaced jets is presented, using a data sample of proton-proton collisions at a center-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 34.7 fb−1, collected with the CMS detector at the CERN LHC in 2022. Novel trigger, reconstruction, and machine-learning techniques were developed for and employed in this search. After all selections, the observations are consistent with the background predictions. Limits are presented on the branching fraction of the Higgs boson to LLPs that subsequently decay to quark pairs or tau lepton pairs. An improvement by up to a factor of 10 is achieved over previous limits for models with LLP masses smaller than 60 GeV and proper decay lengths smaller than 1 m. The first constraints are placed on the fraternal twin Higgs (FTH) and folded supersymmetry (FSUSY) models, where the lower bounds on the top quark partner mass reach up to 350 GeV for the FTH model and 250 GeV for the FSUSY model.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for the Higgs boson decays to a ρ<sup>0</sup>, ϕ, or K<sup>⁎0</sup> meson and a photon in proton-proton collisions at s=13TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 862, ISSN: 0370-2693Three rare decay processes of the Higgs boson to a ρ(770)0, ϕ(1020), or K⁎(892)0 meson and a photon are searched for using s=13TeV proton-proton collision data collected by the CMS experiment at the LHC. Events are selected assuming the mesons decay into a pair of charged pions, a pair of charged kaons, or a charged kaon and pion, respectively. Depending on the Higgs boson production mode, different triggering and reconstruction techniques are adopted. The analyzed data sets correspond to integrated luminosities up to 138fb−1, depending on the reconstructed final state. After combining various data sets and categories, no significant excess above the background expectations is observed. Upper limits at 95% confidence level on the Higgs boson branching fractions into ρ(770)0γ, ϕ(1020)γ, and K⁎(892)0γ are determined to be 3.7×10−4, 3.0×10−4, and 3.0×10−4, respectively. In case of the ρ(770)0γ and ϕ(1020)γ channels, these are the most stringent experimental limits to date.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
First Determination of the Spin-Parity of Ξ_{c}(3055)^{+,0} Baryons.
, Phys Rev Lett, Vol: 134The Ξ_{b}^{0(-)}→Ξ_{c}(3055)^{+(0)}(→D^{+(0)}Λ)π^{-} decay chains are observed, and the spin-parity of Ξ_{c}(3055)^{+(0)} baryons is determined for the first time. The measurement is performed using proton-proton collision data at a center-of-mass energy of sqrt[s]=13 TeV, corresponding to an integrated luminosity of 5.4 fb^{-1}, recorded by the LHCb experiment between 2016 and 2018. The spin-parity of the Ξ_{c}(3055)^{+(0)} baryons is determined to be 3/2^{+} with a significance of more than 6.5σ (3.5σ) compared to all other tested hypotheses. The up-down asymmetries of the Ξ_{b}^{0(-)}→Ξ_{c}(3055)^{+(0)}π^{-} transitions are measured to be -0.92±0.10±0.05 (-0.92±0.16±0.22), consistent with maximal parity violation, where the first uncertainty is statistical and the second is systematic. These results support the hypothesis that the Ξ_{c}(3055)^{+(0)} baryons correspond to the first D-wave λ-mode excitation of the Ξ_{c} flavor triplet.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Measurements of inclusive and differential cross sections for top quark production in association with a Z boson in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>Measurements are presented of inclusive and differential cross sections for Z boson associated production of top quark pairs (<jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \textrm{t}\overline{\textrm{t}}\textrm{Z} $$</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:mi>Z</mml:mi> </mml:math> </jats:alternatives> </jats:inline-formula>) and single top quarks (tZq or tWZ). The data were recorded in proton-proton collisions 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>. Events with three or more leptons, electrons or muons, are selected and a multiclass deep neural network is used to separate three event categories, the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \textrm{t}\overline{\textrm{t}}\textrm{Z} $$</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:mi>Z</mml:mi> </mml:math> </jats:alternatives> </jats:inline-formula> and tWZ processes, the tZq process, and the
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Journal articleArmano M, Audley H, Baird J, et al., 2025,
Magnetic-Induced Force Noise in LISA Pathfinder Free-Falling Test Masses.
, Phys Rev Lett, Vol: 134LISA Pathfinder was a mission designed to test key technologies required for gravitational wave detection in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime, which corresponds to the measurement band of interest for future space-borne gravitational wave observatories. Magnetically induced forces couple to the test mass motion, introducing a contribution to the relative acceleration noise between the free-falling test masses. In this Letter we present the first complete estimate of this term of the instrument performance model. Our results set the magnetic-induced acceleration noise during the February 2017 noise run of 0.25_{-0.08}^{+0.15} fm s^{-2}/sqrt[Hz] at 1 mHz and 1.01_{-0.24}^{+0.73} fm s^{-2}/sqrt[Hz] at 0.1 mHz. We also discuss how the nonstationarities of the interplanetary magnetic field can affect these values during extreme space weather conditions.
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Journal articleArmano M, Audley H, Baird J, et al., 2025,
Precision measurements of the magnetic parameters of LISA Pathfinder test masses
, Physical Review D, Vol: 111, ISSN: 2470-0010A precise characterization of the magnetic properties of LISA Pathfinder free falling test-masses is of special interest for future gravitational wave observatory in space. Magnetic forces have an important impact on the instrument sensitivity in the low frequency regime below the millihertz. In this paper we report on the magnetic injection experiments performed throughout LISA Pathfinder operations. We show how these experiments allowed a high precision estimate of the instrument magnetic parameters. The remanent magnetic moment was found to have a modulus of (0.245±0.081) nAm2, the x-component of the background magnetic field within the test masses position was measured to be (414±74) nT and its gradient had a value of (-7.4±2.1) μT/m. Finally, we also measured the test mass magnetic susceptibility at 5 mHz to be (-3.3723±0.0069)×10-5. All results are in agreement with on-ground estimates.
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Journal articleAkerib DS, Alsum S, Araújo HM, et al., 2025,
Nuclear Recoil Calibration at Sub-keV Energies in LUX and Its Impact on Dark Matter Search Sensitivity.
, Phys Rev Lett, Vol: 134Dual-phase xenon time projection chamber (TPC) detectors offer heightened sensitivities for dark matter detection across a spectrum of particle masses. To broaden their capability to low-mass dark matter interactions, we investigated the light and charge responses of liquid xenon (LXe) to sub-keV nuclear recoils. Using neutron events from a pulsed Adelphi Deuterium-Deuterium neutron generator, an in situ calibration was conducted on the LUX detector. We demonstrate direct measurements of light and charge yields down to 0.45 and 0.27 keV, respectively, both approaching single quanta production, the physical limit of LXe detectors. These results hold significant implications for the future of dual-phase xenon TPCs in detecting low-mass dark matter via nuclear recoils.
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Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Measurement of the Branching Fraction Ratios R(D^{+}) and R(D^{*+}) Using Muonic τ Decays.
, Phys Rev Lett, Vol: 134The branching fraction ratios of B[over ¯]^{0}→D^{+}τ^{-}ν[over ¯]_{τ} and B[over ¯]^{0}→D^{*+}τ^{-}ν[over ¯]_{τ} decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of 2.0 fb^{-1} collected by the LHCb experiment in proton-proton collisions at sqrt[s]=13 TeV. The reconstructed final states are formed by combining D^{+} mesons with τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ} candidates, where the D^{+} is reconstructed via the D^{+}→K^{-}π^{+}π^{+} decay. The results are R(D^{+})=0.249±0.043±0.047, R(D^{*+})=0.402±0.081±0.085, where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of -0.39 and are compatible with the standard model.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Measurement of the $$ \textrm{t}\overline{\textrm{t}}\textrm{H} $$ and tH production rates in the H → $$ \textrm{b}\overline{\textrm{b}} $$ decay channel using proton-proton collision data at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>An analysis of the production of a Higgs boson (H) in association with a top quark-antiquark pair (<jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \textrm{t}\overline{\textrm{t}}\textrm{H} $$</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:mi>H</mml:mi> </mml:math> </jats:alternatives> </jats:inline-formula>) or a single top quark (tH) is presented. The Higgs boson decay into a bottom quark-antiquark pair (H → <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \textrm{b}\overline{\textrm{b}} $$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <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>) is targeted, and three different final states of the top quark decays are considered, defined by the number of leptons (electrons or muons) in the event. The analysis utilises proton-proton collision data collected at the CERN LHC with the CMS experiment at <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \sqrt{s} $$</jats:tex-math> <mml:math xmlns:mml="htt
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for a heavy resonance decaying into a Z and a Higgs boson in events with an energetic jet and two electrons, two muons, or missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>A search is presented for a heavy resonance decaying into a Z boson and a Higgs (H) boson. The analysis is based on data from proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb<jats:sup> <jats:italic>−</jats:italic>1</jats:sup>, recorded with the CMS experiment in the years 2016–2018. Resonance masses between 1.4 and 5 TeV are considered, resulting in large transverse momenta of the Z and H bosons. Final states that result from Z boson decays to pairs of electrons, muons, or neutrinos are considered. The H boson is reconstructed as a single large-radius jet, recoiling against the Z boson. Machine-learning flavour-tagging techniques are employed to identify decays of a Lorentz-boosted H boson into pairs of charm or bottom quarks, or into four quarks via the intermediate H → WW<jats:sup>*</jats:sup> and ZZ<jats:sup>*</jats:sup> decays. The analysis targets H boson decays that were not generally included in previous searches using the H → <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ \textrm{b}\overline{\textrm{b}} $$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <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> channel. Compared with previous analyses, the sensitivity for high resonance masses is improved significantly in the channel where at most one b quark is tagged.</jats:p>
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Journal articleTumasyan A, Adam W, Andrejkovic JW, et al., 2025,
Differential cross section measurements for the production of top quark pairs and of additional jets using dilepton events from pp collisions at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>Differential cross sections for top quark pair (<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>) production are measured in proton-proton collisions at a center-of-mass energy of 13 TeV using a sample of events containing two oppositely charged leptons. The data were recorded with the CMS detector at the CERN Large Hadron Collider and correspond to an integrated luminosity of 138 fb<jats:sup> <jats:italic>−</jats:italic>1</jats:sup>. The differential cross sections are measured as functions of kinematic observables of 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> system, the top quark and antiquark and their decay products, as well as of the number of additional jets in the event. The results are presented as functions of up to three variables and a
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for dark matter produced in association with a pair of bottom quarks in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>A search for dark matter (DM) particles produced in association with bottom quarks is presented. The analysis uses proton-proton collision data at a center-of-mass energy of <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, corresponding to an integrated luminosity of 138 fb<jats:sup> <jats:italic>−</jats:italic>1</jats:sup>. The search is performed in a final state with large missing transverse momentum and a pair of jets originating from bottom quarks. No significant excess of data is observed with respect to the standard model expectation. Results are interpreted in the context of a type-II two-Higgs-doublet model with an additional light pseudoscalar (2HDM+a). An upper limit is set on the mass of the lighter pseudoscalar, probing masses up to 260 GeV at 95% confidence level. Sensitivity to the parameter space with the ratio of the vacuum expectation values of the two Higgs doublets, tan <jats:italic>β</jats:italic>, greater than 15 is achieved, capitalizing on the enhancement of couplings between pseudoscalars and bottom quarks with high tan <jats:italic>β</jats:italic>.</jats:p>
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Journal articleTumasyan A, Adam W, Andrejkovic JW, et al., 2025,
Search for resonant pair production of Higgs bosons in the $$ \textrm{b}\overline{\textrm{b}}\textrm{b}\overline{\textrm{b}} $$ final state using large-area jets in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>A search is presented for the resonant production of a pair of standard model-like Higgs bosons using data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected by the CMS experiment at the CERN LHC in 2016–2018, corresponding to an integrated luminosity of 138 fb<jats:sup> <jats:italic>−</jats:italic>1</jats:sup>. The final state consists of two b quark-antiquark pairs. The search is conducted in the region of phase space where at least one of the pairs is highly Lorentz-boosted and is reconstructed as a single large-area jet. The other pair may be either similarly merged or resolved, the latter reconstructed using two b-tagged jets. The data are found to be consistent with standard model processes and are interpreted as 95% confidence level upper limits on the product of the cross sections and the branching fractions of the spin-0 radion and the spin-2 bulk graviton that arise in warped extradimensional models. The limits set are in the range 9.74–0.29 fb and 4.94–0.19 fb for a narrow radion and a graviton, respectively, with masses between 1 and 3 TeV. For a radion and for a bulk graviton with widths 10% of their masses, the limits are in the range 12.5–0.35 fb and 8.23–0.23 fb, respectively, for the same masses. These limits result in the exclusion of a narrow-width graviton with a mass below 1.2 TeV, and of narrow and 10%-width radions with masses below 2.6, and 2.9 TeV, respectively.</jats:p>
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for long-lived heavy neutral leptons in proton-proton collision events with a lepton-jet pair associated with a secondary vertex at $$ \sqrt{s} $$ = 13 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>A search for long-lived heavy neutral leptons (HNLs) using proton-proton collision data corresponding to an integrated luminosity of 138 fb<jats:sup> <jats:italic>−</jats:italic>1</jats:sup> collected 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 with the CMS detector at the CERN LHC is presented. Events are selected with a charged lepton originating from the primary vertex associated with the proton-proton interaction, as well as a second charged lepton and a hadronic jet associated with a secondary vertex that corresponds to the semileptonic decay of a long-lived HNL. No excess of events above the standard model expectation is observed. Exclusion limits at 95% confidence level are evaluated for HNLs that mix with electron and/or muon neutrinos. Limits are presented in the mass range of 1–16.5 GeV, with excluded square mixing parameter values reaching as low as 2 × 10<jats:sup> <jats:italic>−</jats:italic>7</jats:sup>. For masses above 11 GeV, the presented limits exceed all previous results in the semileptonic decay channel, and for some of the considered scenarios are the strongest to date.</jats:p>
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Measurement of inclusive and differential cross sections for W<sup>+</sup>W<sup>−</sup> production in proton-proton collisions at s=13.6 TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 861, ISSN: 0370-2693Measurements at s=13.6TeV of the opposite-sign W boson pair production cross section in proton-proton collisions are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of 34.8fb−1. Events are selected by requiring one electron and one muon of opposite charge. A maximum likelihood fit is performed on signal- and background-enriched data categories defined by the flavor and charge of the leptons, the number of jets, and number of jets originating from b quarks. The overall sensitivity is significantly better than that of previous results with a similar integrated luminosity. The improvement comes from a more refined control of experimental uncertainties and an improved fit strategy. An inclusive W+W− production cross section of 125.7±5.6 pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event. For the first time in proton-proton collisions, WW events with zero, one, and at least two jets are studied simultaneously and compared with recent theoretical predictions.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Constraints on the Higgs boson self-coupling from the combination of single and double Higgs boson production in proton-proton collisions at s=13TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 861, ISSN: 0370-2693The Higgs boson (H) trilinear self-coupling, λ3, is constrained via its measured properties and limits on the HH pair production using the proton-proton collision data collected by the CMS experiment at s=13TeV. The combination of event categories enriched in single-H and HH events is used to measure κλ, defined as the value of λ3 normalized to its standard model prediction, while simultaneously constraining the Higgs boson couplings to fermions and vector bosons. Values of κλ outside the interval −1.2<κλ<7.5 are excluded at 2σ confidence level, which is compatible with the expected range of −2.0<κλ<7.7 under the assumption that all other Higgs boson couplings are equal to their standard model predicted values. Relaxing the assumption on the Higgs couplings to fermions and vector bosons the observed (expected) κλ interval is constrained to be within −1.4<κλ<7.8 (−2.3<κλ<7.8) at 2σ confidence level.
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Journal articleHori M, 2025,
Antihydrogen’s more than fine spectrum: Antimatter
, Nature Physics, Vol: 21, Pages: 179-180, ISSN: 1745-2473Antihydrogen is the simplest atom of pure antimatter. Measurements of a pair of ultraviolet spectral lines with laser spectroscopy provide stringent bounds on the magnitude by which a symmetry between matter and antimatter may be violated.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Girth and groomed radius of jets recoiling against isolated photons in lead-lead and proton-proton collisions at s<inf><inf>NN</inf></inf>=5.02 TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 861, ISSN: 0370-2693This Letter presents the first measurements of the groomed jet radius Rg and the jet girth g in events with an isolated photon recoiling against a jet in lead-lead (PbPb) and proton-proton (pp) collisions at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The observables Rg and g provide a quantitative measure of how narrow or broad a jet is. The analysis uses PbPb and pp data samples with integrated luminosities of 1.7 nb−1 and 301 pb−1, respectively, collected with the CMS experiment in 2018 and 2017. Events are required to have a photon with transverse momentum pTγ>100 GeV and at least one jet back-to-back in azimuth with respect to the photon and with transverse momentum pTjet such that pTjet/pTγ>0.4. The measured Rg and g distributions are unfolded to the particle level, which facilitates the comparison between the PbPb and pp results and with theoretical predictions. It is found that jets with pTjet/pTγ>0.8, i.e., those that closely balance the photon pTγ, are narrower in PbPb than in pp collisions. Relaxing the selection to include jets with pTjet/pTγ>0.4 reduces the narrowing of the angular structure of jets in PbPb relative to the pp reference. This shows that selection bias effects associated with jet energy loss play an important role in the interpretation of jet substructure measurements.
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Journal articleAbed Abud A, Abi B, Acciarri R, et al., 2025,
The track-length extension fitting algorithm for energy measurement of interacting particles in liquid argon TPCs and its performance with ProtoDUNE-SP data
, Journal of Instrumentation, Vol: 20, Pages: P02021-P02021<jats:title>Abstract</jats:title> <jats:p>This paper introduces a novel track-length extension fitting algorithm for measuring the kinetic energies of inelastically interacting particles in liquid argon time projection chambers (LArTPCs). The algorithm finds the most probable offset in track length for a track-like object by comparing the measured ionization density as a function of position with a theoretical prediction of the energy loss as a function of the energy, including models of electron recombination and detector response. The algorithm can be used to measure the energies of particles that interact before they stop, such as charged pions that are absorbed by argon nuclei. The algorithm's energy measurement resolutions and fractional biases are presented as functions of particle kinetic energy and number of track hits using samples of stopping secondary charged pions in data collected by the ProtoDUNE-SP detector, and also in a detailed simulation. Additional studies describe the impact of the <jats:italic>dE/dx</jats:italic> model on energy measurement performance. The method described in this paper to characterize the energy measurement performance can be repeated in any LArTPC experiment using stopping secondary charged pions.</jats:p>
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Pseudorapidity distributions of charged hadrons in lead-lead collisions at s<inf><inf>NN</inf></inf>=5.36TeV
, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 861, ISSN: 0370-2693The pseudorapidity (η) distributions of charged hadrons are measured using data collected at the highest ever nucleon-nucleon center-of-mass energy of sNN=5.36TeV for collisions of lead-lead ions. The data were recorded by the CMS experiment at the LHC in 2022 and correspond to an integrated luminosity of 0.30±0.03μb−1. Using the CMS silicon pixel detector, the yields of primary charged hadrons produced in the range |η|<2.6 are reported. The evolution of the midrapidity particle density as a function of collision centrality is also reported. In the 5% most central collisions, the charged-hadron η density in the range |η|<0.5 is found to be 2032±91(syst), with negligible statistical uncertainty. This result is consistent with an extrapolation from nucleus-nucleus collision data at lower center-of-mass energies. Comparisons are made to various Monte Carlo event generators and to previous measurements of lead-lead and xenon-xenon collisions at similar collision energies. These new data detail the dependence of particle production on the collision energy, initial collision geometry, and the size of the colliding nuclei.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Search for New Resonances Decaying to Pairs of Merged Diphotons in Proton-Proton Collisions at sqrt[s]=13 TeV.
, Phys Rev Lett, Vol: 134A search is presented for an extended Higgs sector with two new particles, X and ϕ, in the process X→ϕϕ→(γγ)(γγ). Novel neural networks classify events with diphotons that are merged and determine the diphoton masses. The search uses LHC proton-proton collision data at sqrt[s]=13 TeV collected with the CMS detector, corresponding to an integrated luminosity of 138 fb^{-1}. No evidence of such resonances is seen. Upper limits are set on the production cross section for m_{X} between 300 and 3000 GeV and m_{ϕ}/m_{X} between 0.5% and 2.5%, representing the most sensitive search in this channel.
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Journal articleAalbers J, Akerib DS, Al Musalhi AK, et al., 2025,
Two-neutrino double electron capture of <sup>124</sup>Xe in the first LUX-ZEPLIN exposure
, Journal of Physics G: Nuclear and Particle Physics, Vol: 52, ISSN: 0954-3899The broad physics reach of the LUX-ZEPLIN (LZ) experiment covers rare phenomena beyond the direct detection of dark matter. We report precise measurements of the extremely rare decay of 124Xe through the process of two-neutrino double electron capture, utilizing a 1.39 kg × yr isotopic exposure from the first LZ science run. A half-life of T12/n22EC = (1.09 ± 0.14 stat ± 0.05sys ) × 1022 yr is observed with a statistical significance of 8.3σ, in agreement with literature. First empirical measurements of the KK capture fraction relative to other K-shell modes were conducted, and demonstrate consistency with respect to recent signal models at the 1.4σ level.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Measurement of multidifferential cross sections for dijet production in proton–proton collisions at $$\sqrt{s} = 13\,\text {Te}\hspace{-.08em}\text {V} $$
, The European Physical Journal C, Vol: 85<jats:title>Abstract</jats:title> <jats:p>A measurement of the dijet production cross section is reported based on proton–proton collision data collected in 2016 at <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} $$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mspace/> <mml:mi>Te</mml:mi> <mml:mspace/> <mml:mi>V</mml:mi> </mml:mrow> </mml:math> </jats:alternatives> </jats:inline-formula> by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3<jats:inline-formula> <jats:alternatives> <jats:tex-math>$$\,\text {fb}^{-1}$$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mspace/> <mml:msup> <mml:mrow> <mml:mi>fb</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> </jats:alternatives> </jats:inline-formula>. Jets
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Journal articleBarbone M, Tapper A, Luk W, et al., 2025,
Application of computational modelling to particle physics
, Communications in computational physics, ISSN: 1991-7120 -
Journal articleAaij R, Abdelmotteleb ASW, Abellan Beteta C, et al., 2025,
Observation of Exotic J/ψϕ Resonant Structure in Diffractive Processes in Proton-Proton Collisions.
, Phys Rev Lett, Vol: 134The first study of J/ψϕ production in diffractive processes in proton-proton collisions is presented. The study is based on an LHCb dataset recorded at center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 fb^{-1}. The data disfavor a nonresonant J/ψϕ production but are consistent with a resonant model including several resonant states observed previously only in B^{+}→J/ψϕK^{+} decays. The χ_{c0}(4500) state is observed with a significance over 6σ and the χ_{c1}(4274) is confirmed with a significance of more than 4σ.
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Journal articleAhmed A, Bhattacharya A, Das I, 2025,
Anomalous and large topological Hall effects inβ-Mn chiral compound Co6.5Ru1.5Zn8Mn4: electron electron interaction facilitated quantum interference effect.
, J Phys Condens Matter, Vol: 37β-Mn-type chiral cubic CoxZnyMnz(x+y+z= 20) alloys present a intriguing platform for exploring topological magnetic orderings with promising spintronic potential. This study examines the magnetotransport properties of Co6.5Ru1.5Zn8Mn4, a skyrmion-hostingβ-Mn-type chiral compound. The longitudinal resistivity (ρxx) exhibits field-insensitive low-temperature minima due to quantum interference effects, driven byT1/2-dependent electron-electron interactions. We observe a substantial intrinsic anomalous Hall conductivity, unaffected by quantum interference. Additionally, a pronounced topological Hall effect is observed at the metastable skyrmionic state, persisting up toTCand achieving notable magnitudes for stoichiometric compounds. These results position the CoxZnyMnzfamily favourably to leverage the rich pallete of emergent magnetotransport properties for spintronic applications.
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Journal articleHayrapetyan A, Tumasyan A, Adam W, et al., 2025,
Measurement of inclusive and differential cross sections of single top quark production in association with a W boson in proton-proton collisions at $$ \sqrt{s} $$ = 13.6 TeV
, Journal of High Energy Physics, Vol: 2025<jats:title>A<jats:sc>bstract</jats:sc> </jats:title> <jats:p>The first measurement of the inclusive and normalised differential cross sections of single top quark production in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13.6 TeV is presented. The data were recorded with the CMS detector at the LHC in 2022, and correspond to an integrated luminosity of 34.7 fb<jats:sup> <jats:italic>−</jats:italic>1</jats:sup>. The analysed events contain one muon and one electron in the final state. For the inclusive measurement, multivariate discriminants exploiting the kinematic properties of the events are used to separate the signal from the dominant top quark-antiquark production background. A cross section of <jats:inline-formula> <jats:alternatives> <jats:tex-math>$$ 82.3\pm 2.1{\left(\textrm{stat}\right)}_{-9.7}^{+9.9}\left(\textrm{syst}\right)\pm 3.3\left(\textrm{lumi}\right) $$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>82.3</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2.1</mml:mn> <mml:msubsup> <mml:mfenced> <mml:mtext>stat</mml:mtext> </mml:mfenced> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>9.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>9.9</mml:mn> </mml:mrow> </mml:msubsup> <mml:mfenced> <mml:mtext>syst</mml:mtex
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