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1. Measurement of Angular Coefficients of $\overline{B}\to D^{*}\ell {\overline{\nu }}_{\ell }$ : Implications for $\left|V_{cb}\right|$ and Tests of Lepton Flavor Universality

   https://doi.org/10.1103/PhysRevLett.133.131801  

   Prim, M T; Bernlochner, F; Metzner, F; Aihara, H; Asner, D M; Aushev, T; Ayad, R; Babu, V; Banerjee, Sw; Behera, P; et al (September 2024, Physical Review Letters)

   We measure the complete set of angular coefficients $J_i$for exclusive $\overline{B}\to D^{*}\ell {\overline{\nu }}_{\ell }$decays ( $\ell =e$, $\mu$). Our analysis uses the full $711{\mathrm{fb}}^{-1}$Belle dataset with hadronic tag-side reconstruction. The results allow us to extract the form factors describing the $\overline{B}\to D^{*}$transition and the Cabibbo-Kobayashi-Maskawa matrix element $\left|V_{\mathrm{cb}}\right|$. Using recent lattice QCD calculations for the hadronic form factors, we find $\left|V_{\mathrm{cb}}\right|=(40.7\pm 0.7)\times {10}^{-3}$using the Boyd-Grinstein-Lebed parametrization, compatible with determinations from inclusive semileptonic decays. We search for lepton flavor universality violation as a function of the hadronic recoil parameter $w$and investigate the differences of the electron and muon angular distributions. We find no deviation from standard model expectations. Published by the American Physical Society2024 

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2. Observation of $t\overline{t}$ Production in Pb+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ with the ATLAS Detector

   https://doi.org/10.1103/PhysRevLett.134.142301  

   Aad, G; Aakvaag, E; Abbott, B; Abdelhameed, S; Abeling, K; Abicht, N J; Abidi, S H; Aboelela, M; Aboulhorma, A; Abramowicz, H; et al (April 2025, Physical Review Letters)

   Top-quark pair production is observed in lead–lead ( $\mathrm{Pb}+\mathrm{Pb}$) collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$at the Large Hadron Collider with the ATLAS detector. The data sample was recorded in 2015 and 2018, amounting to an integrated luminosity of $1.9{\mathrm{nb}}^{-1}$. Events with exactly one electron and one muon and at least two jets are selected. Top-quark pair production is measured with an observed (expected) significance of 5.0 (4.1) standard deviations. The measured top-quark pair production cross section is ${\sigma }_{t\overline{t}}=3.6{}_{-0.9}^{+1.0}\left(\mathrm{stat}\right){}_{-0.5}^{+0.8}\left(\mathrm{syst}\right)\mathrm{\mu }\mathrm{b}$, with a total relative uncertainty of 31%, and is consistent with theoretical predictions using a range of different nuclear parton distribution functions. The observation of this process consolidates the evidence of the existence of all quark flavors in the preequilibrium stage of the quark-gluon plasma at very high energy densities, similar to the conditions present in the early Universe. © 2025 CERN, for the ATLAS Collaboration2025CERN 

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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. 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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5. Search for the baryon number and lepton number violating decays ${\tau }^{-}\to \mathrm{\Lambda }{\pi }^{-}$ and ${\tau }^{-}\to \overline{\mathrm{\Lambda }}{\pi }^{-}$ at Belle II

   https://doi.org/10.1103/PhysRevD.110.112003  

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

   We present a search for the baryon number $B$and lepton number $L$violating decays ${\tau }^{-}\to \mathrm{\Lambda }{\pi }^{-}$and ${\tau }^{-}\to \overline{\mathrm{\Lambda }}{\pi }^{-}$produced from the $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$process, using a $364{\mathrm{fb}}^{-1}$data sample collected by the Belle II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have $\left|\mathrm{\Delta }\right(B-L\left)\right|$equal to 2 and 0, respectively. Upper limits at 90% credibility level on the branching fractions of ${\tau }^{-}\to \mathrm{\Lambda }{\pi }^{-}$and ${\tau }^{-}\to \overline{\mathrm{\Lambda }}{\pi }^{-}$are determined to be $4.7\times {10}^{-8}$and $4.3\times {10}^{-8}$, respectively. Published by the American Physical Society2024 

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