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1. Test of lepton flavor universality with a measurement of $R\left(D^{*}\right)$ using hadronic $B$ tagging at the Belle II experiment

   https://doi.org/10.1103/PhysRevD.110.072020  

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

   The ratio of branching fractions $R\left(D^{*}\right)=\mathcal{B}(\overline{B}\to D^{*}{\tau }^{-}{\overline{\nu }}_{\tau })/\mathcal{B}(\overline{B}\to D^{*}{\ell }^{-}{\overline{\nu }}_{\ell })$, where $\ell$is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of $189{\mathrm{fb}}^{-1}$at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$collider. Data is collected at the $\mathrm{\Upsilon }\left(4\mathrm{S}\right)$resonance, and one $B$meson in the $\mathrm{\Upsilon }\left(4\mathrm{S}\right)\to B\overline{B}$decay is fully reconstructed in hadronic decay modes. The accompanying signal $B$meson is reconstructed as $\overline{B}\to D^{*}{\tau }^{-}{\overline{\nu }}_{\tau }$using leptonic $\tau$decays. The normalization decay, $\overline{B}\to D^{*}{\ell }^{-}{\overline{\nu }}_{\ell }$, produces the same observable final-state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields $R\left(D^{*}\right)={0.262}_{-0.039}^{+0.041}\left(\mathrm{stat}{)}_{-0.032}^{+0.035}\right(\mathrm{syst})$. This result is consistent with the current world average and with Standard Model predictions. Published by the American Physical Society2024 

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2. Poles and poltergeists in $e^{+}{e}^{-}\to D\overline{D}$ data

   https://doi.org/10.1103/PhysRevD.109.114010  

   Hüsken, Nils; Lebed, Richard F; Mitchell, Ryan E; Swanson, Eric S; Wang, Ya-Qian; Yuan, Chang-Zheng (June 2024, Physical Review D)

   A recent report of $e^{+}{e}^{-}\to D\overline{D}$events by the BESIII collaboration suggests the presence of a structure $R$at 3900 MeV. We argue that this structure, called $G\left(3900\right)$in the past, is not in fact due to a new $c\overline{c}$resonance but rather naturally emerges due to a combination of interference between nearby resonances and the opening of the $D^{*}\overline{D}$channel. We further find that the appearance of this structure does not require suppression because of a radial node in the $\psi \left(4040\right)$wave function, although a node improves fit quality. The measured $e^{+}{e}^{-}$coupling of $\psi \left(4040\right)$is found to be substantially smaller than previously estimated. In addition, we report new corrections to the measured cross section $\sigma (e^{+}{e}^{-}\to D\overline{D})$at energies near $\psi \left(3770\right)$. Published by the American Physical Society2024 

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3. Measurements of polarization and spin correlation and observation of entanglement in top quark pairs using $\mathrm{lepton}+\text{jets}$ events from proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevD.110.112016  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Benato, L; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; et al (December 2024, Physical Review D)

   Measurements of the polarization and spin correlation in top quark pairs ( $t\overline{t}$) are presented using events with a single electron or muon and jets in the final state. The measurements are based on proton-proton collision data from the LHC at $\sqrt{s}=13\mathrm{TeV}$collected by the CMS experiment, corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$. All coefficients of the polarization vectors and the spin correlation matrix are extracted simultaneously by performing a binned likelihood fit to the data. The measurement is performed inclusively and in bins of additional observables, such as the mass of the $t\overline{t}$system and the top quark scattering angle in the $t\overline{t}$rest frame. The measured polarization and spin correlation are in agreement with the standard model. From the measured spin correlation, conclusions on the $t\overline{t}$spin entanglement are drawn by applying the Peres-Horodecki criterion. The standard model predicts entangled spins for $t\overline{t}$states at the production threshold and at high masses of the $t\overline{t}$system. Entanglement is observed for the first time in events at high $t\overline{t}$mass, where a large fraction of the $t\overline{t}$decays are spacelike separated, with an expected and observed significance of above 5 standard deviations. © 2024 CERN, for the CMS Collaboration2024CERN 

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4. Combination of Searches for Resonant Higgs Boson Pair Production Using $pp$ Collisions at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS Detector

   https://doi.org/10.1103/PhysRevLett.132.231801  

   Aad, G; Aakvaag, E; Abbott, B; Abeling, K; Abicht, N J; Abidi, S H; Aboulhorma, A; Abramowicz, H; Abreu, H; Abulaiti, Y; et al (June 2024, Physical Review Letters)

   A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to $139{\mathrm{fb}}^{-1}$of $pp$collision data at $\sqrt{s}=13\mathrm{TeV}$recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: $b\overline{b}b\overline{b}$, $b\overline{b}{\tau }^{+}{\tau }^{-}$, and $b\overline{b}\gamma \gamma$. 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 Collaboration2024CERN 

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5. Search for Baryon-Number-Violating Processes in $B^{-}$ Decays to the ${\overline{\mathrm{\Xi }}}_c^0{\overline{\mathrm{\Lambda }}}_c^{-}$ Final State

   https://doi.org/10.1103/PhysRevLett.133.071802  

   Gu, T; Savinov, V; Adachi, I; Aihara, H; Asner, D M; Atmacan, H; Aushev, T; Ayad, R; Banerjee, Sw; Belous, K; et al (August 2024, Physical Review Letters)

   We report the results of the first search for $B^{-}$decays to the ${\overline{\mathrm{\Xi }}}_c^0{\overline{\mathrm{\Lambda }}}_c^{-}$final state using $711{\mathrm{fb}}^{-1}$of data collected at the $\mathrm{\Upsilon }\left(4S\right)$resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$collider. The results are interpreted in terms of both direct baryon-number-violating $B^{-}$decay and ${\mathrm{\Xi }}_c^0-{\overline{\mathrm{\Xi }}}_c^0$oscillations which follow the standard model decay $B^{-}\to {\mathrm{\Xi }}_c^0{\overline{\mathrm{\Lambda }}}_c^{-}$. We observe no evidence for baryon number violation and set the 95% confidence-level upper limits on the ratio of baryon-number-violating and standard model branching fractions $\mathcal{B}(B^{-}\to {\overline{\mathrm{\Xi }}}_c^0{\overline{\mathrm{\Lambda }}}_c^{-})/\mathcal{B}(B^{-}\to {\mathrm{\Xi }}_c^0{\overline{\mathrm{\Lambda }}}_c^{-})$to be $<2.7\%$and on the effective angular frequency of mixing $\omega$in ${\mathrm{\Xi }}_c^0-{\overline{\mathrm{\Xi }}}_c^0$oscillations to be $<0.76{\mathrm{ps}}^{-1}$(equivalent to ${\tau }_{\mathrm{mix}}>1.3\mathrm{ps}$). Published by the American Physical Society2024 

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