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At least 1,441 records · Page 80

Search for e + e − → η ′ ψ ( 2 S ) at center-of-mass energies from 4.66 to 4.95 GeV

Using data samples with an integrated luminosity of 4.67 fb − 1 collected by the BESIII detector operating at the BEPCII Collider, we search for the process e + e − → η ′ ψ ( 2 S ) at center-of-mass energies from 4.66 to 4.95 GeV. No significant signal is observed, and upper limits for the Born cross sections σ B ( e + e − → η ′ ψ ( 2 S ) ) at the 90% confidence level are determined. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

Improved measurement of the semileptonic decay D s + → K 0 e + ν e

Analyzing e + e − collision data corresponding to an integrated luminosity of 7.33 fb − 1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we measure the branching fraction of the semileptonic decay D s + → K 0 e + ν e to be ( 2.98 ± 0.2 3 stat ± 0.1 2 syst ) × 10 − 3 . Based on fit to the partial decay rates in various q 2 intervals, the product value of D s + → K 0 hadronic form factor and Cabibbo-Kobayashi-Maskawa element is measured to be f + K 0 ( 0 ) | V c d | = 0.143 ± 0.01 1 stat ± 0.00 3 syst . With | V c d | = 0.22486 ± 0.00067 as an input, the hadronic form factor is evaluated to be f + K 0 ( 0 ) = 0.636 ± 0.04 9 stat ± 0.01 3 syst . The branching fraction and form factor measurements are factors of 1.6 and 1.7 more precise than the previous world averages, respectively. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

Precision measurement of the Ξ b − baryon lifetime

A sample of p p collision data, corresponding to an integrated luminosity of 5.5 fb − 1 and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the Ξ b − baryon to that of the Λ b 0 baryon, r τ ≡ τ Ξ b − / τ Λ b 0 . The value r τ = 1.076 ± 0.013 ± 0.006 is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain r τ Run 1 , 2 = 1.078 ± 0.012 ± 0.007 . Multiplying by the world-average value of the Λ b 0 lifetime yields τ Ξ b − Run 1 , 2 = 1.578 ± 0.018 ± 0.010 ± 0.011 ps , where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λ b 0 lifetime. This measurement improves the precision of the current world average of the Ξ b − lifetime by about a factor of 2, and is in good agreement with the most recent theoretical predictions. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

Measurements of the branching fractions of semileptonic D s + decays via e + e − → D s * + D s * −

We measure the absolute branching fractions of semileptonic D s + decays via the e + e − → D s * + D s * − process using e + e − collision data corresponding to an integrated luminosity of 10.64 fb − 1 collected by the BESIII detector at center-of-mass energies between 4.237 and 4.699 GeV. The branching fractions are B ( D s + → η e + ν e ) = ( 2.35 ± 0.11 stat ± 0.10 syst ) % , B ( D s + → η ′ e + ν e ) = ( 0.82 ± 0.09 stat ± 0.04 syst ) % , B ( D s + → ϕ e + ν e ) = ( 2.21 ± 0.16 stat ± 0.11 syst ) % , B ( D s + → f 0 ( 980 ) e + ν e , f 0 ( 980 ) → π + π − ) = ( 0.15 ± 0.02 stat ± 0.01 syst ) % , B ( D s + → K 0 e + ν e ) = ( 0.24 ± 0.0 4 stat ± 0.0 1 syst ) % , and B ( D s + → K * 0 e + ν e ) = ( 0.19 ± 0.0 3 stat ± 0.0 1 syst ) % . These results are consistent with those measured via the e + e − → D s * ± D s ∓ process by BESIII and CLEO. Using two-parameter series expansion, the hadronic transition form factors of D s + → η e + ν e , D s + → η ′ e + ν e , and D s + → K 0 e + ν e are determined to be f + η ( 0 ) = 0.442 ± 0.02 2 stat ± 0.01 7 syst , f + η ′ ( 0 ) = 0.557 ± 0.06 2 stat ± 0.02 4 syst , and f + K 0 ( 0 ) = 0.677 ± 0.09 8 stat ± 0.02 3 syst . Published by the American Physical Society 2024

Ablikim, M.↗

Search for D 0 → K − η e + ν e , D + → K S 0 η e + ν e and D + → η η e + ν e decays

By analyzing e + e − annihilation data corresponding to an integrated luminosity of 7.93 fb − 1 , collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we search for the semileptonic decays D 0 → K − η e + ν e , D + → K S 0 η e + ν e and D + → η η e + ν e for the first time. We present evidence for D 0 → K − η e + ν e with a significance of 3.3 σ . The branching fraction of D 0 → K − η e + ν e is measured to be ( 0.8 4 − 0.34 + 0.29 ± 0.22 ) × 10 − 4 . No significant signals are observed for the decays D + → K S 0 η e + ν e and D + → η η e + ν e and we set the upper limits on their branching fractions. Published by the American Physical Society 2024

Ablikim, M.↗

Measurement of the branching fractions of the decays Λ c + → Λ K S 0 K + , Λ c + → Λ K S 0 π + , and Λ c + → Λ K * +

Studies are performed of the Cabibbo-favored decay Λ c + → Λ K S 0 K + and the singly Cabibbo-suppressed decay Λ c + → Λ K S 0 π + , based on a sample of e + e − collision data, corresponding to an integrated luminosity of 4.5 fb − 1 , accumulated at center-of-mass energies between 4599.53 MeV and 4698.82 MeV with the BESIII detector. The decay Λ c + → Λ K S 0 π + is observed for the first time. The branching fractions of Λ c + → Λ K S 0 K + and Λ c + → Λ K S 0 π + are measured to be ( 3.04 ± 0.30 ± 0.16 ) × 10 − 3 and ( 1.73 ± 0.27 ± 0.10 ) × 10 − 3 , respectively, where the first uncertainties are statistical and the second are systematic. These results correspond to the most precise measurement of these quantities for both decays. Evidence of a K * + contribution in the Λ c + → Λ K S 0 π + decay is found with a statistical significance of 4.71 σ . The branching fraction of Λ c + → Λ K * + is calculated under three possible interference scenarios, with the significance increasing to 5.03 σ when interference is taken into account. Published by the American Physical Society 2025

Ablikim, M.↗

Observation of Enhanced Double Parton Scattering in Proton-Lead Collisions at $\sqrt{s_{NN}}$= 8.16 TeV

A study of prompt charm-hadron pair production in proton-lead collisions at $\sqrt{s_{NN}$ = 8.16 TeV is performed using data corresponding to an integrated luminosity of about 30 nb -1 , collected with the LHCb experiment. Production cross sections for different pairs of charm hadrons are measured and kinematic correlations between the two charm hadrons are investigated. This is the first measurement of associated production of two charm hadrons in proton-lead collisions. The results confirm the predicted enhancement of double parton scattering production in proton-lead collisions compared to the single parton scattering production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

First Search for Exclusive Diphoton Production at High Mass with Tagged Protons in Proton-Proton Collisions at $\sqrt{s} = 13$

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$\gamma\gamma$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvert\zeta_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvert\zeta_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Observation of e + e – → ω χ b J ( 1 P ) and Search for X b → ω Υ ( 1 S ) at s near 10.75 GeV

We study the processes $e^{+}e^{–} → ωχ_{bJ}$(1P) (J=0, 1, or 2) using samples at center-of-mass energies $\sqrt{s}$ = 10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb –1 of integrated luminosity, respectively. These data were collected with the Belle II detector during special operations of the SuperKEKB collider above the Υ(4S) resonance. We report the first observation of $ωχ_{bJ}$(1P) signals at $\sqrt{s}$ = 10.745 GeV. By combining Belle II data with Belle results at $\sqrt{s}$ = 10.867 GeV, we find energy dependencies of the Born cross sections for $e^{+}e^{–} → ωχ_{b1,b2}$(1P) to be consistent with the shape of the Υ(10753) state. These data indicate that the internal structures of the Υ(10753) and Υ(10860) states may differ. Including data at $\sqrt{s}$ = 10.653 GeV, we also search for the bottomonium equivalent of the X(3872) state decaying into ωΥ(1S). No significant signal is observed for masses between 10.45 and 10.65 GeV/c 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Evidence of a $J/$$\psi$$K_S^0$ Structure in $B^0$ → $J/$$\psi$$\phi$$K_S^0$

An amplitude analysis of $B^0$ → $J/$$\psi$$\phi$$K_S^0$ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 9 fb –1 , collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. Evidence with a significance of 4.0 standard deviations of a structure in the $J/$$\psi$$K_S^0$ system, named $T_{ψs1}^{θ}$⁢⁢(4000) 0 , is seen, with its mass and width measured to be 3991$_{–10 –17}^{+12 +9}$ MeV/⁢c 2 and 105$_{–25 –23}^{+29 +17}$ MeV, respectively, where the first uncertainty is statistical and the second systematic. The $T_{ψs1}^{θ}$⁢⁢(4000) 0 state is likely to be the isospin partner of the $T_{ψs1}^{θ}$⁢⁢(4000) + state, previously observed in the $J/ψK^+$ system of the $B^+$→$J/ψ$$\phi$$K^+$ decay. When isospin symmetry for the charged and neutral $T_{ψs1}^{θ}$⁢⁢(4000) states is assumed, the signal significance increases to 5.4 standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Observation of $\tau$ lepton pair production in ultraperipheral lead-lead collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV

We present an observation of photon-photon production of $\tau$ lepton pairs in ultraperipheral lead-lead collisions. The measurement is based on a data sample with an integrated luminosity of 404 $\mu$b$^{-1}$ collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The $\gamma\gamma$$\to$$\tau^+\tau^-$ process is observed for $\tau\tau$ events with a muon and three charged hadrons in the final state. The measured fiducial cross section is $\sigma(\gamma\gamma$$\to$$\tau^+\tau^-)$ = 4.8 $\pm$ 0.6 (stat) $\pm$ 0.5 (syst) $\mu$b, in agreement with leading-order QED predictions. Using $\sigma(\gamma\gamma$$\to$$\tau^+\tau^-)$, we estimate a model-dependent value of the anomalous magnetic moment of the $\tau$ lepton of $a_\tau$ = 0.001 $^{+0.055}_{-0.089}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurement of C P Violation in B 0 → ψ ( → ℓ + ℓ − ) K S 0 ( → π + π − ) Decays

A measurement of time-dependent C P violation in the decays of B 0 and B ¯ 0 mesons to the final states J / ψ ( → μ + μ − ) K S 0 , ψ ( 2 S ) ( → μ + μ − ) K S 0 and J / ψ ( → e + e − ) K S 0 with K S 0 → π + π − is presented. The data correspond to an integrated luminosity of 6 fb − 1 collected at a center-of-mass energy of s = 13 TeV with the LHCb detector. The C P -violation parameters are measured to be S ψ K S 0 = 0.717 ± 0.013 ( stat ) ± 0.008 ( syst ) and C ψ K S 0 = 0.008 ± 0.012 ( stat ) ± 0.003 ( syst ) . This measurement of S ψ K S 0 represents the most precise single measurement of the CKM angle β to date and is more precise than the current world average. In addition, measurements of the C P -violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

Improved Measurement of C P Violation Parameters in B s 0 → J / ψ K + K − Decays in the Vicinity of the ϕ ( 1020 ) Resonance

The decay-time-dependent C P asymmetry in B s 0 → J / ψ ( → μ + μ − ) K + K − 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. Using a sample of approximately 349 000 B s 0 signal decays with an invariant K + K − mass in the vicinity of the ϕ ( 1020 ) resonance, the C P -violating phase ϕ s is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B s 0 − B ¯ s 0 system, Δ Γ s , and the difference of the average B s 0 and B 0 meson decay widths, Γ s − Γ d . The values obtained are ϕ s = − 0.039 ± 0.022 ± 0.006 rad , Δ Γ s = 0.0845 ± 0.0044 ± 0.0024 ps − 1 , and Γ s − Γ d = − 0.005 6 − 0.0015 + 0.0013 ± 0.0014 ps − 1 , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ϕ s is also measured independently for each polarization state of the K + K − system and shows no evidence for polarization dependence. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Study of the f 0 ( 980 ) and f 0 ( 500 ) Scalar Mesons through the Decay D s + → π + π − e + ν e

Using e + e − collision data corresponding to an integrated luminosity of 7.33 fb − 1 recorded by the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, we present an analysis of the decay D s + → π + π − e + ν e , where the D s + is produced via the process e + e − → D s * ± D s ∓ . We observe the f 0 ( 980 ) in the π + π − system and the branching fraction of the decay D s + → f 0 ( 980 ) e + ν e with f 0 ( 980 ) → π + π − measured to be ( 1.72 ± 0.1 3 stat ± 0.1 0 syst ) × 10 − 3 , where the uncertainties are statistical and systematic, respectively. The dynamics of the D s + → f 0 ( 980 ) e + ν e decay are studied with the simple pole parametrization of the hadronic form factor and the Flatté formula describing the f 0 ( 980 ) in the differential decay rate, and the product of the form factor f + f 0 ( 0 ) and the c → s Cabibbo-Kobayashi-Maskawa matrix element | V c s | is determined for the first time to be f + f 0 ( 0 ) | V c s | = 0.504 ± 0.01 7 stat ± 0.03 5 syst . Furthermore, the decay D s + → f 0 ( 500 ) e + ν e is searched for the first time but no signal is found. The upper limit on the branching fraction of D s + → f 0 ( 500 ) e + ν e , f 0 ( 500 ) → π + π − decay is set to be 3.3 × 10 − 4 at 90% confidence level. Published by the American Physical Society 2024

Ablikim, M.↗

Search for Narrow Trijet Resonances in Proton-Proton Collisions at s = 13 TeV

The first search for singly produced narrow resonances decaying to three well-separated hadronic jets is presented. The search uses proton-proton collision data corresponding to an integrated luminosity of 138 fb − 1 at s = 13 TeV , collected at the CERN LHC. No significant deviations from the background predictions are observed between 1.75 and 9.00 TeV. The results provide the first mass limits on a right-handed boson Z R decaying to three gluons and on an excited quark decaying via a vector boson to three quarks, as well as updated limits on a Kaluza-Klein gluon decaying via a radion to three gluons. © 2024 CERN, for the CMS Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurement of C P Violation Observables in D + → K − K + π + Decays

A search for violation of the charge-parity ( C P ) symmetry in the D + → K − K + π + decay is presented, with proton-proton collision data corresponding to an integrated luminosity of 5.4 fb − 1 , collected at a center-of-mass energy of 13 TeV with the LHCb detector. A novel model-independent technique is used to compare the D + and D − phase-space distributions, with instrumental asymmetries subtracted using the D s + → K − K + π + decay as a control channel. The p value for the hypothesis of C P conservation is 8.1%. The C P asymmetry observables A C P | S ϕ π + = ( 0.95 ± 0.4 3 stat ± 0.2 6 syst ) × 10 − 3 and A C P | S K ¯ * 0 K + = ( − 0.26 ± 0.5 6 stat ± 0.1 8 syst ) × 10 − 3 are also measured. These results show no evidence of C P violation and represent the most sensitive search performed through the phase space of a multibody decay. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

Observation of the Open-Charm Tetraquark Candidate T c s 0 * ( 2870 ) 0 in the B − → D − D 0 K S 0 Decay

An 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 5.3 σ . 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 c s 0 * ( 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 c s 0 * ( 2870 ) 0 state in a new decay mode. The T c s 1 * ( 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. © 2025 CERN, for the LHCb Collaboration 2025 CERN

Aaij, R. (ORCID:0000000305331952)↗

Evidence for Two Excited Ω − Hyperons

Using e + e − collision data corresponding to an integrated luminosity of 19 fb − 1 collected by the BESIII detector at center-of-mass energies ranging from 4.13 to 4.70 GeV, we report the first evidence for a new excited Ω − hyperon, the Ω ( 2109 ) − , through the process e + e − → Ω ( 2109 ) − Ω ¯ + + c . c . with a significance of 4.1 σ . The mass and width of Ω ( 2109 ) − are measured to be 2108.5 ± 5.2 stat ± 0.9 syst MeV / c 2 and 18.3 ± 16.4 stat ± 5.7 syst MeV , respectively. We also present evidence for a new production mechanism for the previously identified Ω ( 2012 ) − via the process e + e − → Ω ( 2012 ) − Ω ¯ + + c . c . with a significance of 3.5 σ . Published by the American Physical Society 2025

Ablikim, M.↗