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1. Search for $$ {\textrm{B}}_{\textrm{s}}^0 $$ → ℓ∓τ± with the semi-leptonic tagging method at Belle

   https://doi.org/10.1007/JHEP08(2023)178  

   Nayak, L ; Nishida, S ; Giri, A ; Adachi, I ; Aihara, H ; Asner, D M ; Atmacan, H ; Aulchenko, V ; Aushev, T ; Ayad, R ; et al ( August 2023 , Journal of High Energy Physics)

   We present a search for the lepton-flavor-violating decays$$ {B}_s^0 $$$B_s^0$→ℓ^∓τ^±, whereℓ=e, μ, using the full data sample of 121 fb⁻¹collected at the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energye⁺e⁻collider. We use$$ {B}_s^0{\overline{B}}_s^0 $$$B_s^0{\overline{B}}_s^0$events in which one$$ {B}_s^0 $$$B_s^0$meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for$$ {B}_s^0 $$$B_s^0$→ ℓ^∓τ^±decays and set upper limits on their branching fractions at 90% confidence level as$$ \mathcal{B} $$$B$($$ {B}_s^0 $$$B_s^0$→ e^∓τ^±)<14×10⁻⁴and$$ \mathcal{B} $$$B$($$ {B}_s^0 $$$B_s^0$→ μ^∓τ^±)<7.3×10⁻⁴. Our result represents the first upper limit on the$$ {B}_s^0 $$$B_s^0$→ e^∓τ^±decay rate.

    

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2. Search for the $$ {B}_s^0 $$ → μ+μ−γ decay

   https://doi.org/10.1007/JHEP07(2024)101  

   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 ( July 2024 , Journal of High Energy Physics)

   A search for the fully reconstructed$$ {B}_s^0 $$$B_s^0$→ μ⁺μ⁻γdecay is performed at the LHCb experiment using proton-proton collisions at$$ \sqrt{s} $$$\sqrt{s}$= 13 TeV corresponding to an integrated luminosity of 5.4 fb⁻¹. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set$$ {\displaystyle \begin{array}{cc}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left[2{m}_{\mu },1.70\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<7.7\times {10}^{-8},&\ m\left({\mu}^{+}{\mu}^{-}\right)\in \left[\textrm{1.70,2.88}\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left[3.92,{m}_{B_s^0}\right]\textrm{GeV}/{c}^2,\end{array}} $$$\begin{array}{cc}B\left(B_s^0\to {\mu }^{+}{\mu }^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu }^{+}{\mu }^{-}\right)\in \left(2m_{\mu },1.70\right)\mathrm{GeV}/c^2,\\ B\left(B_s^0\to {\mu }^{+}{\mu }^{-}\gamma \right)<7.7\times {10}^{-8},& m\left({\mu }^{+}{\mu }^{-}\right)\in \left(\mathrm{1.70,\; 2.88}\right)\mathrm{GeV}/c^2,\\ B\left(B_s^0\to {\mu }^{+}{\mu }^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu }^{+}{\mu }^{-}\right)\in \left(3.92,m_{B_s^0}\right)\mathrm{GeV}/c^2,\end{array}$

   at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2m_μ,1.70] GeV/c²dimuon mass region excluding the contribution from the intermediateϕ(1020) meson, and in the region combining all dimuon-mass intervals.

    

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3. Measurement of branching-fraction ratios and CP asymmetries in B± → DCP±K± decays at Belle and Belle II

   https://doi.org/10.1007/JHEP05(2024)212  

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

   We report results from a study ofB^±→ DK^±decays followed byDdecaying to theCP-even final stateK⁺K⁻and CP-odd final state$$ {K}_S^0{\pi}^0 $$$K_S^0{\pi }^0$, whereDis an admixture ofD⁰and$$ {\overline{D}}^0 $$${\overline{D}}^0$states. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angleϕ₃. The results are based on a combined analysis of the final data set of 772×10⁶$$ B\overline{B} $$$B\overline{B}$pairs collected by the Belle experiment and a data set of 198×10⁶$$ B\overline{B} $$$B\overline{B}$pairs collected by the Belle II experiment, both in electron-positron collisions at the Υ(4S) resonance. We measure the CP asymmetries to be$$ \mathcal{A} $$$A$_CP+= (+12.5±5.8±1.4)% and$$ \mathcal{A} $$$A$_CP−= (−16.7±5.7±0.6)%, and the ratios of branching fractions to be$$ \mathcal{R} $$$R$_CP+= 1.164±0.081±0.036 and$$ \mathcal{R} $$$R$_CP−= 1.151±0.074±0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries$$ \mathcal{A} $$$A$_CP+and$$ \mathcal{A} $$$A$_CP−have similar magnitudes and opposite signs; their difference corresponds to 3.5 standard deviations. From these values we calculate 68.3% confidence intervals of (8.5^°<ϕ₃< 16.5^°) or (84.5^°<ϕ₃< 95.5^°) or (163.3^°<ϕ₃< 171.5^°) and 0.321 <r_B< 0.465.

    

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4. Measurement of CP asymmetries and branching-fraction ratios for B± → DK± and Dπ± with D → $$ {K}_{\textrm{S}}^0 $$K±π∓ using Belle and Belle II data

   https://doi.org/10.1007/JHEP09(2023)146  

   Adachi, I ; Aggarwal, L ; Aihara, H ; Akopov, N ; Aloisio, A ; Anh_Ky, N ; Asner, D M ; Aushev, T ; Aushev, V ; Aversano, M ; et al ( September 2023 , Journal of High Energy Physics)

   We measureCPasymmetries and branching-fraction ratios forB^±→ DK^±andDπ^±decays withD →$$ {K}_{\textrm{S}}^0 $$$K_S^0$K^±π^∓, whereDis a superposition ofD⁰and$$ \overline{D} $$$\overline{D}$⁰. We use the full data set of the Belle experiment, containing 772×10⁶$$ B\overline{B} $$$B\overline{B}$pairs, and data from the Belle II experiment, containing 387 × 10⁶$$ B\overline{B} $$$B\overline{B}$pairs, both collected in electron-positron collisions at the Υ(4S) resonance. Our results provide model-independent information on the unitarity triangle angleϕ₃.

    

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5. Charm production and fragmentation fractions at midrapidity in pp collisions at $$ \sqrt{\textrm{s}} $$ = 13 TeV

   https://doi.org/10.1007/JHEP12(2023)086  

   Acharya, S ; Adamová, D ; Aglieri_Rinella, G ; Agnello, M ; Agrawal, N ; Ahammed, Z ; Ahmad, S ; Ahn, S U ; Ahuja, I ; Akindinov, A ; et al ( December 2023 , Journal of High Energy Physics)

   Measurements of the production cross sections of prompt D⁰, D⁺, D^*+,$$ {\textrm{D}}_{\textrm{s}}^{+} $$$D_s^{+}$,$$ {\Lambda}_{\textrm{c}}^{+} $$${\Lambda }_c^{+}$, and$$ {\Xi}_{\textrm{c}}^{+} $$${\Xi }_c^{+}$charm hadrons at midrapidity in proton-proton collisions at$$ \sqrt{s} $$$\sqrt{s}$= 13 TeV with the ALICE detector are presented. The D-meson cross sections as a function of transverse momentum (p_T) are provided with improved precision and granularity. The ratios ofp_T-differential meson production cross sections based on this publication and on measurements at different rapidity and collision energy provide a constraint on gluon parton distribution functions at low values of Bjorken-x(10⁻⁵–10⁻⁴). The measurements of$$ {\Lambda}_{\textrm{c}}^{+} $$${\Lambda }_c^{+}$($$ {\Xi}_{\textrm{c}}^{+} $$${\Xi }_c^{+}$) baryon production extend the measuredp_Tintervals down top_T= 0(3) GeV/c. These measurements are used to determine the charm-quark fragmentation fractions and the$$ \textrm{c}\overline{\textrm{c}} $$$c\overline{c}$production cross section at midrapidity (|y|<0.5) based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons D⁰, D⁺,$$ {\textrm{D}}_{\textrm{s}}^{+} $$$D_s^{+}$,$$ {\Lambda}_{\textrm{c}}^{+} $$${\Lambda }_c^{+}$,$$ {\Xi}_{\textrm{c}}^0 $$${\Xi }_c^0$and, for the first time,$$ {\Xi}_{\textrm{c}}^{+} $$${\Xi }_c^{+}$, and of the strongly-decaying J/ψmesons. The first measurements of$$ {\Xi}_{\textrm{c}}^{+} $$${\Xi }_c^{+}$and$$ {\Sigma}_{\textrm{c}}^{0,++} $$${\Sigma }_c^{0,++}$fragmentation fractions at midrapidity are also reported. A significantly larger fraction of charm quarks hadronising to baryons is found compared to e⁺e⁻and ep collisions. The$$ \textrm{c}\overline{\textrm{c}} $$$c\overline{c}$production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations.

    

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