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  1. Cluster structure of 3 α + p states in N 13

    Clusmore » ter states in N 13 are extremely difficult to measure due to the unavailability of B 9 + α elastic-scattering data. Using β -delayed charged-particle spectroscopy of O 13 , clustered states in N 13 can be populated and measured in the 3 α + p decay channel. One-at-a-time implantation and decay of O 13 was performed with the Texas Active Target Time Projection Chamber. 149 β 3 α p decay events were observed and the excitation function in N 13 reconstructed. Four previously unknown α -decaying excited states were observed in N 13 at an excitation energy of 11.3, 12.4, 13.1, and 13.7 MeV decaying via the 3 α + p channel. These states are seen to have a [ 9 B ( g . s ) α / p + C 12 ( 0 2 + ) ] ,   [ 9 B ( 1 2 + ) α ] ,   [ 9 B ( 5 2 + ) α ] , and [ 9 B ( 5 2 + ) α ] structure, respectively. A previously seen state at 11.8 MeV was also determined to have a [ p + C 12 ( g . s . ) / p + C 12 ( 0 2 + ) ] structure. The overall magnitude of the clustering is not able to be extracted, however, due to the lack of a total width measurement. tered states in N 13 (with unknown magnitude) seem to persist from the addition of a proton to the highly α -clustered C 12 . Evidence of the 1 2 + state in B 9 was also seen to be populated by decays from N 13 . Published by the American Physical Society 2024« less
  2. Testing meson portal dark sector solutions to the MiniBooNE anomaly at the Coherent CAPTAIN Mills experiment

    A solution to the MiniBooNE excess invoking rare three-body decays of the charged pions and kaons to new states in the MeV mass scale was recently proposed as a dark-sector explanation. This class of solution illuminates the fact that, while the charged pions were focused in the target-mode run, their decay products were isotropically suppressed in the beam-dump-mode run in which no excess was observed. This suggests a new physics solution correlated to the mesonic sector. We investigate an extended set of phenomenological models that can explain the MiniBooNE excess as a dark sector solution, utilizing long-lived particles that mightmore » be produced in the three-body decays of the charged mesons and the two-body anomalous decays of the neutral mesons. Over a broad set of interactions with the long-lived particles, we show that these scenarios can be compatible with constraints from LSND, KARMEN, and MicroBooNE, and evaluate the sensitivity of the ongoing and future data taken by the Coherent CAPTAIN Mills experiment to a potential discovery in this parameter space. Published by the American Physical Society 2024« less
  3. Search for a μ + μ resonance in four-muon final states at Belle II

    We repormore » t on a search for a resonance X decaying to a pair of muons in e + e μ + μ X events in the 0.212 9.000 GeV / c 2 mass range, using 178 fb 1 of data collected by the Belle II experiment at the SuperKEKB collider at a center of mass energy of 10.58 GeV. The analysis probes two different models of X beyond the standard model: a Z vector boson in the L μ L τ model and a muonphilic scalar. We observe no evidence for a signal and set exclusion limits at the 90% confidence level on the products of cross section and branching fraction for these processes, ranging from 0.046 fb to 0.97 fb for the L μ L τ model and from 0.055 fb to 1.3 fb for the muonphilic scalar model. For masses below 6 GeV / c 2 , the corresponding constraints on the couplings of these processes to the standard model range from 0.0008 to 0.039 for the L μ L τ model and from 0.0018 to 0.040 for the muonphilic scalar model. These are the first constraints on the muonphilic scalar from a dedicated search. Published by the American Physical Society 2024« less
  4. Search for Baryon Number Violation in Top Quark Production and Decay Using Proton-Proton Collisions at s = 13 TeV

    A semore » arch is presented for baryon number violating interactions in top quark production and decay. The analysis uses data from proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC with an integrated luminosity of 138 fb 1 . Candidate events are selected by requiring two oppositely charged leptons (electrons or muons) and exactly one jet identified as originating from a bottom quark. Multivariate discriminants are used to separate the signal from the background. No significant deviation from the standard model prediction is observed. Upper limits are placed on the strength of baryon number violating couplings. For the first time the production of single top quarks via baryon number violating interactions is studied. This allows the search to set the most stringent constraints to date on the branching fraction of the top quark decay to a lepton, an up-type quark ( u or c ), and a down-type quark ( d , s , or b ). The results improve the previous bounds by 3 to 6 orders of magnitude based on the fermion flavor combination of the baryon number violating interactions. © 2024 CERN, for the CMS Collaboration 2024 CERN« less
  5. Search for pair production of higgsinos in events with two Higgs bosons and missing transverse momentum in s = 13 TeV p p collisions at the ATLAS experiment

    Tmore » his paper presents a search for pair production of higgsinos, the supersymmetric partners of the Higgs bosons, in scenarios with gauge-mediated supersymmetry breaking. Each higgsino is assumed to decay into a Higgs boson and a nearly massless gravitino. he search targets events where each Higgs boson decays into b b ¯ , leading to a reconstructed final state with at least three energetic b -jets and missing transverse momentum. wo complementary analysis channels are used, with each channel specifically targeting either low or high values of the higgsino mass. he low-mass (high-mass) channel exploits 126 ( 139 ) fb 1 of s = 13 eV data collected by the ALAS detector during Run 2 of the Large Hadron Collider. No significant excess above the Standard Model prediction is found. At 95% confidence level, masses between 130 GeV and 940 GeV are excluded for higgsinos decaying exclusively into Higgs bosons and gravitinos. Exclusion limits as a function of the higgsino decay branching ratio to a Higgs boson are also reported. © 2024 CERN, for the ALAS Collaboration 2024 CERN« less
  6. Combined search for electroweak production of winos, binos, higgsinos, and sleptons in proton-proton collisions at s = 13 TeV

    A combination of the results of several searches for the electroweak production of the supersymmetric partners of standard model bosons, and of charged leptons, is presented. All searches use proton-proton collision data atmore » $$\sqrt{s}$$ =13 TeV recorded with the CMS detector at the LHC in 2016–2018. The analyzed data correspond to an integrated luminosity of up to 137 fb-1. The results are interpreted in terms of simplified models of supersymmetry. Two new interpretations are added with this combination: a model spectrum with the bino as the lightest supersymmetric particle together with mass-degenerate Higgsinos decaying to the bino and a standard model boson, and the compressed-spectrum region of a previously studied model of slepton pair production. Improved analysis techniques are employed to optimize sensitivity for the compressed spectra in the wino and slepton pair production models. The results are consistent with expectations from the standard model. The combination provides a more comprehensive coverage of the model parameter space than the individual searches, extending the exclusion by up to 125 GeV, and also targets some of the intermediate gaps in the mass coverage.« less
  7. Search for stealth supersymmetry in final states with two photons, jets, and low missing transverse momentum in proton-proton collisions at s = 13 TeV

    The results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (more » $$p^{miss}_T$$), are reported. The study is based on a sample of proton-proton collisions at $$\sqrt{s}$$ = 13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb-1. As LHC results continue to constrain the parameter space of the minimal supersymmetric standard model, the low $$p^{miss}_T$$ regime is increasingly valuable to explore. To estimate the backgrounds due to standard model processes in such events, we apply corrections derived from simulation to an estimate based on a control selection in data. The results are interpreted in the context of simplified stealth supersymmetry models with gluino and squark pair production. The observed data are consistent with the standard model predictions, and gluino (squark) masses of up to 2150 (1850) GeV are excluded at the 95% confidence level.« less
  8. Search for long-lived particles using displaced vertices and missing transverse momentum in proton-proton collisions at s = 13 TeV

    A search for the production of long-lived particles in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC is presented. The search is based on data collected by the CMS experiment in 2016–2018, corresponding to a total integrated luminosity of 137 fb-1. This search is designed to be sensitive to long-lived particles with mean proper decay lengths between 0.1 and 1000 mm, whose decay products produce a final state with at least one displaced vertex and missing transverse momentum. A machine learning algorithm, which improves the background rejection power by more than an order of magnitude,more » is applied to improve the sensitivity. The observation is consistent with the standard model background prediction, and the results are used to constrain split supersymmetry (SUSY) and gauge mediated SUSY breaking models with different gluino mean proper decay lengths and masses. This search is the first CMS search that shows sensitivity to hadronically decaying long-lived particles from signals with mass differences between the gluino and neutralino below 100 GeV. It sets the most stringent limits to date for split-SUSY models and gauge-mediated SUSY breaking models with gluino proper decay length less than 6 mm.« less
  9. Observation of the J / ψ μ + μ μ + μ decay in proton-proton collisions at s = 13 TeV

    Tmore » he J / ψ μ + μ μ + μ decay has been observed with a statistical significance in excess of five standard deviations. he analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 eV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 33.6 fb 1 . Normalizing to the J / ψ μ + μ decay mode leads to a branching fraction of [ 10.1 2.7 + 3.3 ( stat ) ± 0.4 ( syst ) ] × 10 7 , a value that is consistent with the standard model prediction. © 2024 CERN, for the CMS Collaboration 2024 CERN« less
  10. Combination of Searches for Resonant Higgs Boson Pair Production Using p p Collisions at s = 13 TeV with the ATLAS Detector

    A comore » mbination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to 139 fb 1 of p p collision data at s = 13 TeV recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: b b ¯ b b ¯ , b b ¯ τ + τ , and b b ¯ γ γ . No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV–5 TeV. The observed (expected) limits are in the range 0.96–600 fb (1.2–390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches. © 2024 CERN, for the ATLAS Collaboration 2024 CERN« less
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