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DOE OSTI2024

Search for the radiative transition χ c 1 ( 3872 ) → γ ψ 2 ( 3823 )

Using 9.0 f b − 1 of e + e − collision data collected at center-of-mass energies from 4.178 to 4.278 GeV with the BESIII detector at the BEPCII collider, we perform the first search for the radiative transition χ c 1 ( 3872 ) → γ ψ 2 ( 3823 ) . No signal is observed and the upper limit on the ratio of branching fractions B ( χ c 1 ( 3872 ) → γ ψ 2 ( 3823 ) , ψ 2 ( 3823 ) → γ χ c 1 ) / B ( χ c 1 ( 3872 ) → π + π − J / ψ ) is set at 0.075 at the 90% confidence level. Our result contradicts theoretical predictions under the assumption that the χ c 1 ( 3872 ) is the pure charmonium state χ c 1 ( 2 P ) . Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Study of the decays χ c J → Λ Λ ¯ ϕ

Based on ( 2712.4 ± 14.3 ) × 10 6 e + e − → ψ ( 3686 ) events collected with the BESIII detector operating at the BEPCII Collider, we report the first evidence of χ c 0 → Λ Λ ¯ ϕ decays and the first observation of χ c 1 , 2 → Λ Λ ¯ ϕ decays, with significances of 4.1 σ , 11.3 σ and 13.0 σ , respectively. The decay branching fractions of χ c 0 , 1 , 2 → Λ Λ ¯ ϕ are measured to be ( 2.99 ± 1.24 ± 0.19 ) × 10 − 5 , ( 6.01 ± 0.90 ± 0.40 ) × 10 − 5 , and ( 7.13 ± 0.81 ± 0.36 ) × 10 − 5 , where the first uncertainties are statistical and the second systematic. No obvious enhancement near the Λ Λ ¯ production threshold or excited Λ state is found in the Λ ϕ (or Λ ¯ ϕ ) system. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for J / ψ weak decays containing a D meson

Using a sample of about 10 billion J / ψ events with the BESIII detector, we search for the weak decays of J / ψ → D ¯ 0 π 0 + c . c . , J / ψ → D ¯ 0 η + c . c . , J / ψ → D ¯ 0 ρ 0 + c . c . , J / ψ → D − π + + c . c . , and J / ψ → D − ρ + + c . c . . Since no significant signal is observed, we set the upper limits of the branching fractions of these decays to be B ( J / ψ → D ¯ 0 π 0 + c . c . ) < 4.7 × 10 − 7 , B ( J / ψ → D ¯ 0 η + c . c . ) < 6.8 × 10 − 7 , B ( J / ψ → D ¯ 0 ρ 0 + c . c . ) < 5.2 × 10 − 7 , B ( J / ψ → D − π + + c . c . ) < 7.0 × 10 − 8 , and B ( J / ψ → D − ρ + + c . c . ) < 6.0 × 10 − 7 at the 90% confidence level. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Study of the decays χ c J → Λ Λ ¯ ω

Using ( 27.12 ± 0.14 ) × 10 8 ψ ( 3686 ) events collected with the BESIII detector, we present the first observation of the decays χ c J → Λ Λ ¯ ω , where J = 0 , 1, 2, with statistical significances of 11.7 σ , 11.2 σ , and 11.8 σ . The branching fractions of these decays are determined to be B ( χ c 0 → Λ Λ ¯ ω ) = ( 2.37 ± 0.22 ± 0.25 ) × 10 − 4 , B ( χ c 1 → Λ Λ ¯ ω ) = ( 1.01 ± 0.10 ± 0.11 ) × 10 − 4 , and B ( χ c 2 → Λ Λ ¯ ω ) = ( 1.40 ± 0.13 ± 0.17 ) × 10 − 4 , where the first uncertainties are statistical and the second are systematic. We observe no clear intermediate structures. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for bottom-type vectorlike quark pair production in dileptonic and fully hadronic final states in proton-proton collisions at s = 13 TeV

A search is described for the production of a pair of bottom-type vectorlike quarks ( B VLQs) with mass greater than 1000 GeV. Each B VLQ decays into a b quark and a Higgs boson, a b quark and a Z boson, or a t quark and a W boson. This analysis considers both fully hadronic final states and those containing a charged lepton pair from a Z boson decay. The products of the H → b b boson decay and of the hadronic Z or W boson decays can be resolved as two distinct jets or merged into a single jet, so the final states are classified by the number of reconstructed jets. The analysis uses data corresponding to an integrated luminosity of 138 fb - 1 collected in proton-proton collisions at s = 13 TeV with the CMS detector at the LHC from 2016 to 2018. No excess over the expected background is observed. Lower limits are set on the B VLQ mass at the 95% confidence level. These depend on the B VLQ branching fractions and are 1570 and 1540 GeV for 100% B → b H and 100% B → b Z , respectively. In most cases, the mass limits obtained exceed previous limits by at least 100 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Search for η c ( 2 S ) → 2 ( π + π − ) and improved measurement of χ c J → 2 ( π + π − )

We search for the hadronic decay η c ( 2 S ) → 2 ( π + π − ) in the ψ ( 3686 ) → γ η c ( 2 S ) radiative decay using ( 27.12 ± 0.14 ) × 10 8 ψ ( 3686 ) events collected by the BESIII detector at the BEPCII collider. No significant signal is found, and the upper limit of B [ ψ ( 3686 ) → γ η c ( 2 S ) ] B [ η c ( 2 S ) → 2 ( π + π − ) ] is determined to be 1.43 × 10 − 6 at the 90% confidence level. Using ψ ( 3686 ) → γ χ c J transitions, we also measure the branching fractions of B [ χ c J ( J = 0 , 1 , 2 ) → 2 ( π + π − ) ] , which are B [ χ c 0 → 2 ( π + π − ) ] = ( 2.127 ± 0.002 ( stat ) ± 0.101 ( syst ) ) % , B [ χ c 1 → 2 ( π + π − ) ] = ( 0.685 ± 0.001 ( stat ) ± 0.031 ( syst ) ) % , and B [ χ c 2 → 2 ( π + π − ) ] = ( 1.153 ± 0.001 ( stat ) ± 0.063 ( syst ) ) % . Published by the American Physical Society 2024

Ablikim, M.↗

DOE OSTI2024

Search for production of a single vectorlike quark decaying to t H or t Z in the all-hadronic final state in p p collisions at s = 13 TeV

A search for electroweak production of a single vectorlike T quark in association with a bottom ( b ) quark in the all-hadronic decay channel is presented. This search uses proton-proton collision data at s = 13 TeV collected by the CMS experiment at the CERN LHC during 2016–2018, corresponding to an integrated luminosity of 138 fb - 1 . The T quark is assumed to have charge 2 / 3 and decay to a top ( t ) quark and a Higgs ( H ) or Z boson. Hadronic decays of the t quark and the H or Z boson are reconstructed from the kinematic properties of jets, including those containing b hadrons. No deviation from the standard model prediction is observed in the reconstructed t H and t Z invariant mass distributions. The 95% confidence level upper limits on the product of the production cross section and branching fraction of a T quark produced in association with a b quark and decaying via t H or t Z range from 1260 to 68 fb for T quark masses of 600–1200 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Search for the lepton-flavor violating decay B s 0 → ϕ μ ± τ ∓

A search for the lepton-flavor violating decays B s 0 → ϕ μ ± τ ∓ is presented, using a sample of proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb − 1 . The τ leptons are selected using decays with three charged pions. No significant excess is observed, and an upper limit on the branching fraction is determined to be B ( B s 0 → ϕ μ ± τ ∓ ) < 1.0 × 10 − 5 at 90% confidence level. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Search for the baryon number and lepton number violating decays τ − → Λ π − and τ − → Λ ¯ π − at Belle II

We present a search for the baryon number B and lepton number L violating decays τ − → Λ π − and τ − → Λ ¯ π − produced from the e + e − → τ + τ − process, using a 364 fb − 1 data sample collected by the Belle II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have | Δ ( B − L ) | equal to 2 and 0, respectively. Upper limits at 90% credibility level on the branching fractions of τ − → Λ π − and τ − → Λ ¯ π − are determined to be 4.7 × 10 − 8 and 4.3 × 10 − 8 , respectively. Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)↗

DOE OSTI2024

Search for h c → π + π − J / ψ via ψ ( 3686 ) → π 0 h c

Using ( 2712.4 ± 14.3 ) × 10 6 ψ ( 3686 ) events collected with the BESIII detector operating at the BEPCII collider, we search for the hadronic transition h c → π + π − J / ψ via ψ ( 3686 ) → π 0 h c . No significant signal is observed. We set the most stringent upper limits to date on the branching fractions B ( ψ ( 3686 ) → π 0 h c ) × B ( h c → π + π − J / ψ ) and B ( h c → π + π − J / ψ ) at the 90% confidence level, which are determined to be 6.7 × 10 − 7 and 9.4 × 10 − 4 , respectively. Published by the American Physical Society 2024

Ablikim, M.↗

DOE OSTI2024

Observation of χ c 0 → Σ + Σ ¯ − η and evidence for χ c 1 , 2 → Σ + Σ ¯ − η

Using ( 27.12 ± 0.14 ) × 10 8 ψ ( 3686 ) events collected with the BESIII detector, the decay χ c 0 → Σ + Σ ¯ − η is observed for the first time with a signal significance of 7.0 σ , and evidence for χ c 1 → Σ + Σ ¯ − η and χ c 2 → Σ + Σ ¯ − η is found with signal significances of 4.3 σ and 4.6 σ , respectively. The branching fractions are determined to be B ( χ c 0 → Σ + Σ ¯ − η ) = ( 1.26 ± 0.20 ± 0.13 ) × 10 − 4 , B ( χ c 1 → Σ + Σ ¯ − η ) = ( 5.10 ± 1.21 ± 0.67 ) × 10 − 5 , and B ( χ c 2 → Σ + Σ ¯ − η ) = ( 5.46 ± 1.18 ± 0.50 ) × 10 − 5 , where the first uncertainties are statistical, and the second ones are systematic. Published by the American Physical Society 2024

Ablikim, M.↗

DOE OSTI2024

Study of the decay D 0 → ρ ( 770 ) − e + ν e

We present a study of the semileptonic decay D 0 → π − π 0 e + ν e using an e + e − annihilation data sample of 7.93 fb − 1 collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The branching fraction of D 0 → ρ ( 770 ) − e + ν e is measured to be ( 1.439 ± 0.033 ( stat ) ± 0.027 ( syst ) ) × 10 − 3 , which is a factor 1.6 more precise than previous measurements. By performing an amplitude analysis, we measure the hadronic form-factor ratios of D 0 → ρ ( 770 ) − e + ν e at q 2 = 0 assuming the single-pole-dominance parametrization: r V = V ( 0 ) / A 1 ( 0 ) = 1.548 ± 0.079 ( stat ) ± 0.041 ( syst ) and r 2 = A 2 ( 0 ) / A 1 ( 0 ) = 0.823 ± 0.056 ( stat ) ± 0.026 ( syst ) . Published by the American Physical Society 2024

Ablikim, M.↗

DOE OSTI2024

Search for diphoton decays of an axionlike particle in radiative J / ψ decays

We search for the diphoton decay of a light pseudoscalar axionlike particle, a , in radiative J / ψ decays, using 10 10 J / ψ events collected with the BESIII detector. We find no evidence of a signal and set upper limits at the 95% confidence level on the product branching fraction B ( J / ψ → γ a ) × B ( a → γ γ ) and the axionlike particle photon coupling constant g a γ γ in the ranges of ( 3.7 – 48.5 ) × 10 − 8 and ( 2.2 – 101.8 ) × 10 − 4 GeV − 1 , respectively, for 0.18 ≤ m a ≤ 2.85 GeV / c 2 . These are the most stringent limits to date in this mass region. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for two-body B meson decays to Λ 0 and Ω c ( * ) 0

We report the results of the first search for Standard Model and baryon-number-violating two-body decays of the neutral B mesons to Λ 0 and Ω c ( * ) 0 using 711 fb − 1 of data collected at the ϒ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. We observe no evidence of signal from any such decays and set 95% confidence-level upper limits on the products of B 0 and B ¯ 0 branching fractions for these two-body decays with B ( Ω c 0 → π + Ω − ) in the range between 9.5 × 10 − 8 and 31.2 × 10 − 8 . Published by the American Physical Society 2024

Savinov, V. (ORCID:0000000291842830)↗

DOE OSTI2024

Search for the e + e − → ϕ χ c 1 ( 3872 ) process at BESIII

Based on 368.5 p b − 1 of e + e − collision data collected at center-of-mass energies 4.914 and 4.946 GeV by the BESIII detector, the e + e − → ϕ χ c 1 ( 3872 ) process is searched for the first time. No significant signal is observed and the upper limits at the 90% confidence level on the product of the Born cross section σ ( e + e − → ϕ χ c 1 ( 3872 ) ) and the branching fraction B [ χ c 1 ( 3872 ) → π + π − J / ψ ] at 4.914 and 4.946 GeV are set to be 0.85 and 0.96 pb, respectively. These measurements provide useful information for the production of the χ c 1 ( 3872 ) at e + e − colliders and deepen our understanding about the nature of this particle. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for the decay B 0 → γ γ using Belle and Belle II data

We report the result of a search for the rare decay B 0 → γ γ using a combined dataset of 753 × 10 6 B B ¯ pairs collected by the Belle experiment and 387 × 10 6 B B ¯ pairs collected by the Belle II experiment from decays of the ϒ ( 4 S ) resonance produced in e + e − collisions. A simultaneous fit to the Belle and Belle II data sets yields 11.0 − 5.5 + 6.5 signal events, corresponding to a 2.5 σ significance. We determine the branching fraction B ( B 0 → γ γ ) = ( 3.7 − 1.8 + 2.2 ( stat ) ± 0.5 ( syst ) ) × 10 − 8 and set a 90% credibility level upper limit of B ( B 0 → γ γ ) < 6.4 × 10 − 8 . Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)↗

DOE OSTI2025

Search for charged-lepton flavor violation in the production and decay of top quarks using trilepton final states in proton-proton collisions at $\sqrt{s}$ =13 TeV

A search is performed for charged-lepton flavor violating processes in top quark (𝑡) production and decay. The data were collected by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 138 fb −1 . The selected events are required to contain one opposite-sign electron-muon pair, a third charged lepton (electron or muon), and at least one jet of which no more than one is associated with a bottom quark. Boosted decision trees are used to distinguish signal from background, exploiting differences in the kinematics of the final states particles. The data are consistent with the standard model expectation. Upper limits at 95% confidence level are placed in the context of effective field theory on the Wilson coefficients, which range between 0.024–0.424 TeV −2 depending on the flavor of the associated light quark and the Lorentz structure of the interaction. These limits are converted to upper limits on branching fractions involving up (charm) quarks, 𝑡 → 𝑒⁢𝜇⁢𝑢 (𝑡 → 𝑒⁢𝜇⁢𝑐), of 0.032⁢(0.498) × 10 −6 , 0.022⁢(0.369) × 10 −6 , and 0.012⁢(0.216) × 10 −6 for tensorlike, vectorlike, and scalarlike interactions, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Search for charged Higgs bosons produced in top-quark decays or in association with top quarks and decaying via H±→τ±ντ in 13 TeV pp collisions with the ATLAS detector

Charged Higgs bosons produced either in top-quark decays or in association with a top quark, subsequently decaying via , are searched for in of proton-proton collision data at recorded with the ATLAS detector. Depending on whether the top quark is produced together with the decays hadronically or semileptonically, the search targets or final states, in both cases with a -lepton decaying into a neutrino and hadrons. No significant excess over the Standard Model background expectation is observed. For the mass range of , upper limits at 95% confidence level are set on the production cross section of the charged Higgs boson times the branching fraction in the range 4.5 pb–0.4 fb. In the mass range 80–160 GeV, assuming the Standard Model cross section for production, this corresponds to upper limits between 0.27% and 0.02% on .

Aad, G↗