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Measurement of $C P$ Asymmetries in $B^{0} \to K_{S}^{0} π^{0} γ$ Decays at Belle II

https://doi.org/10.1103/PhysRevLett.134.011802

Adachi, I; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, T; et al (January 2025, Physical Review Letters)

We report measurements of time-dependent $C P$ asymmetries in $B^{0} \to K_{S}^{0} π^{0} γ$ decays based on a data sample of $(388 \pm 6) \times 10^{6} B \bar{B}$ events collected at the $ϒ (4 S)$ resonance with the Belle II detector. The Belle II experiment operates at the SuperKEKB asymmetric-energy $e^{+} e^{-}$ collider. We measure decay-time distributions to determine $C P$ -violating parameters $S$ and $C$ . We determine these parameters for two ranges of $K_{S}^{0} π^{0}$ invariant mass: $m (K_{S}^{0} π^{0}) \in (0.8, 1.0) GeV / c^{2}$ , which is dominated by $B^{0} \to K^{* 0} (\to K_{S}^{0} π^{0}) γ$ decays, and a complementary region $m (K_{S}^{0} π^{0}) \in (0.6, 0.8) \cup (1.0, 1.8) GeV / c^{2}$ . Our results have improved precision as compared to previous measurements and are consistent with theory predictions. Published by the American Physical Society2025
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Measurement of $C P$ asymmetries in $B^{0} \to η^{'} K_{S}^{0}$ decays at Belle II

https://doi.org/10.1103/PhysRevD.110.112002

Adachi, I; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, T; et al (December 2024, Physical Review D)

We describe a measurement of charge-parity ( $C P$ ) violation asymmetries in $B^{0} \to η^{'} K_{S}^{0}$ decays using Belle II data. We consider $η^{'} \to η (\to γ γ) π^{+} π^{-}$ and $η^{'} \to ρ (\to π^{+} π^{-}) γ$ decays. The data were collected at the SuperKEKB asymmetric-energy $e^{+} e^{-}$ collider between the years 2019 and 2022, and contain $(387 \pm 6) \times 10^{6}$ bottom-antibottom meson pairs. We reconstruct $829 \pm 35$ signal decays and extract the $C P$ violating parameters from a fit to the distribution of the proper-decay-time difference between the two $B$ mesons. The measured direct and mixing-induced $C P$ asymmetries are $C_{η^{'} K_{S}^{0}} = - 0.19 \pm 0.08 \pm 0.03$ and $S_{η^{'} K_{S}^{0}} = + 0.67 \pm 0.10 \pm 0.03$ , respectively, where the first uncertainties are statistical and the second are systematic. These results are in agreement with current world averages and standard model predictions. Published by the American Physical Society2024
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Angular analysis of B0 → K*0e+e− decays

https://doi.org/10.1007/JHEP06(2025)140

Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (June 2025, Journal of High Energy Physics)

A<sc>bstract</sc> An angular analysis ofB⁰→ K^*0e⁺e⁻decays is presented using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb⁻¹. The analysis is performed in the region of the dilepton invariant mass squared of 1.1–6.0 GeV²/c⁴. In addition, a test of lepton flavour universality is performed by comparing the obtained angular observables with those measured inB⁰→ K^*0μ⁺μ⁻decays. In general, the angular observables are found to be consistent with the Standard Model expectations as well as with global analyses of otherb → sℓ⁺ℓ⁻processes, whereℓis either a muon or an electron. No sign of lepton-flavour-violating effects is observed.
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Search for the $$ {B}_c^{+} $$ → χc1(3872)π+ decay

https://doi.org/10.1007/JHEP06(2025)013

Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (June 2025, Journal of High Energy Physics)

A<sc>bstract</sc> A search for the decay$$ {B}_c^{+} $$ $B_{c}^{+}$ → χ_c1(3872)π⁺is reported using proton-proton collision data collected with the LHCb detector between 2011 and 2018 at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb⁻¹. No significant signal is observed. Using the decay$$ {B}_c^{+} $$ $B_{c}^{+}$ →ψ(2S)π⁺as a normalisation channel, an upper limit for the ratio of branching fractions$$ {\mathcal{R}}_{\psi (2S)}^{\chi_{c1}(3872)}=\frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c1}(3872){\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to \psi (2S){\pi}^{+}}}\times \frac{{\mathcal{B}}_{\chi_{c1}(3872)\to J/\psi {\pi}^{+}{\pi}^{-}}}{{\mathcal{B}}_{\psi (2S)\to J/\psi {\pi}^{+}{\pi}^{-}}}<0.05(0.06), $$ $R_{ψ (2 S)}^{χ_{c 1} (3872)} = \frac{B_{B_{c}^{+} \to χ_{c 1} (3872) π^{+}}}{B_{B_{c}^{+} \to ψ (2 S) π^{+}}} \times \frac{B_{χ_{c 1} (3872) \to J / ψ π^{+} π^{-}}}{B_{ψ (2 S) \to J / ψ π^{+} π^{-}}} < 0.05 (0.06),$ is set at the 90 (95)% confidence level.
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Study of $D_{s 1} {(2460)}^{+} \to D_{s}^{+} π^{+} π^{-}$ in $B \to {\overline{D}}^{(*)} D_{s}^{+} π^{+} π^{-}$ decays

https://doi.org/10.1016/j.scib.2025.02.025

Aaij, R; Abdelmotteleb, ASW; Beteta, CAbellan; Abudinén, F; Ackernley, T; Adefisoye, AA; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (May 2025, Science Bulletin)

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Determination of the CKM angle ϕ3 from a combination of Belle and Belle II results

https://doi.org/10.1007/JHEP10(2024)143

Adachi, I; Aggarwal, L; Aihara, H; Akopov, N; Aloisio, A; Al_Said, S; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, V; et al (October 2024, Journal of High Energy Physics)

A<sc>bstract</sc> We report a determination of the CKM angleϕ₃, also known asγ, from a combination of measurements using samples of up to 711 fb⁻¹from the Belle experiment and up to 362 fb⁻¹from the Belle II experiment. We combine results from analyses ofB⁺→ DK⁺,B⁺→ Dπ⁺, andB⁺→ D^*K⁺decays, whereDis an admixture ofD⁰and$$ {\overline{D}}^0 $$ ${\bar{D}}^{0}$ mesons, in a likelihood fit to obtainϕ₃= (75.2±7.6)^°. We also briefly discuss the interpretation of this result.
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Branching fraction measurement of the decay $B^{+} \to ψ (2 S) ϕ (1020) K^{+}$

https://doi.org/10.1103/PhysRevD.111.092008

Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (May 2025, Physical Review D)

The branching fraction of the decay $B^{+} \to ψ (2 S) ϕ (1020) K^{+}$ , relative to the topologically similar decay $B^{+} \to J / ψ ϕ (1020) K^{+}$ , is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of $9 {fb}^{- 1}$ . The ratio is found to be $0.061 \pm 0.004 \pm 0.009$ , where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for $B^{+} \to J / ψ ϕ (1020) K^{+}$ , the branching fraction for the decay $B^{+} \to ψ (2 S) ϕ (1020) K^{+}$ is found to be $(3.0 \pm 0.2 \pm 0.5 \pm 0.2) \times 10^{- 6}$ , where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel. © 2025 CERN, for the LHCb Collaboration2025CERN
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Search for resonance-enhanced $C P$ and angular asymmetries in the $Λ_{c}^{+} \to p μ^{+} μ^{-}$ decay at LHCb

https://doi.org/10.1103/PhysRevD.111.L091102

Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (May 2025, Physical Review D)

The first measurement of the $C P$ asymmetry of the decay rate ( $A_{C P}$ ) and the $C P$ average ( $Σ A_{FB}$ ) and $C P$ asymmetry ( $Δ A_{FB}$ ) of the forward-backward asymmetry in the muon system of $Λ_{c}^{+} \to p μ^{+} μ^{-}$ decays is reported. The measurement is performed using a data sample of proton-proton collisions, recorded by the LHCb experiment from 2016 to 2018 at a center-of-mass energy of 13 TeV, which corresponds to an integrated luminosity of $5.4 {fb}^{- 1}$ . The asymmetries are measured in two regions of dimuon mass near the $ϕ$ -meson mass peak. The dimuon-mass integrated results are $A_{C P} = (- 1.1 \pm 4.0 \pm 0.5) %$ , $Σ A_{FB} = (3.9 \pm 4.0 \pm 0.6) %$ , $Δ A_{FB} = (3.1 \pm 4.0 \pm 0.4) %$ , where the first uncertainty is statistical and the second systematic. The results are consistent with the conservation of $C P$ symmetry and the Standard Model expectations. © 2025 CERN, for the LHCb Collaboration2025CERN
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Measurement of $C P$ asymmetries in $Λ_{b}^{0} \to p h^{-}$ decays

https://doi.org/10.1103/PhysRevD.111.092004

Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (May 2025, Physical Review D)

A search for $C P$ violation in $Λ_{b}^{0} \to p K^{-}$ and $Λ_{b}^{0} \to p π^{-}$ decays is presented using the full Run 1 and Run 2 data samples of $p p$ collisions collected with the LHCb detector, corresponding to an integrated luminosity of $9 {fb}^{- 1}$ at center-of-mass energies of 7, 8, and 13 TeV. For the Run 2 data sample, the $C P$ -violating asymmetries are measured to be $A_{C P}^{p K^{-}} = (- 1.4 \pm 0.7 \pm 0.4) %$ and $A_{C P}^{p π^{-}} = (0.4 \pm 0.9 \pm 0.4) %$ , where the first uncertainty is statistical and the second is systematic. Following significant improvements in the evaluation of systematic uncertainties compared to the previous LHCb measurement, the Run 1 dataset is reanalyzed to update the corresponding results. When combining the Run 2 and updated Run 1 measurements, the final results are found to be $A_{C P}^{p K^{-}} = (- 1.1 \pm 0.7 \pm 0.4) %$ and $A_{C P}^{p π^{-}} = (0.2 \pm 0.8 \pm 0.4) %$ , constituting the most precise measurements of these asymmetries to date. © 2025 CERN, for the LHCb Collaboration2025CERN
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Measurement of the multiplicity dependence of Υ production ratios in pp collisions at $$ \sqrt{s} $$ = 13 TeV

https://doi.org/10.1007/JHEP05(2025)011

Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (May 2025, Journal of High Energy Physics)

A<sc>bstract</sc> TheΥ(2S) andΥ(3S) production cross-sections are measured relative to that of theΥ(1S) meson, as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of 13 TeV. The measurement uses data collected by the LHCb experiment in 2018 corresponding to an integrated luminosity of 2 fb⁻¹. Both theΥ(2S)-to-Υ(1S) andΥ(3S)-to-Υ(1S) cross-section ratios are found to decrease significantly as a function of event multiplicity, with theΥ(3S)-to-Υ(1S) ratio showing a steeper decline towards high multiplicity. This hierarchy is qualitatively consistent with the comover model predictions, indicating that final-state interactions play an important role in bottomonia production in high-multiplicity events.
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