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1. Revisiting $C$ and $CP$ violation in $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$ decay

   https://doi.org/10.1103/PhysRevD.110.055039  

   Shi, Jun; Liang, Jian; Gardner, Susan (September 2024, Physical Review D)

   The decay $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$is an ideal process in which to study flavor-conserving $C$and $CP$violation beyond the Standard Model. We deduce the $C$- and $CP$-odd quark operators that contribute to $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$originating from the mass-dimension-six Standard Model effective field theory. The corresponding hadron-level operators that generate a nonvanishing $I=0$amplitude at order $p^6$in the chiral effective theory are presented for the first time, to the best of our knowledge, in addition to the leading-order operators ascribed to the $I=2$final state. By fitting the KLOE-2 and the most recent BESIII experimental data, we determine the coefficients of the lowest-order $I=0$and $I=2$amplitudes and estimate the potential new physics energy scale. We also perform an impact study of the future $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$experiments. Published by the American Physical Society2024 

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2. Measurement of ${\mathrm{\Lambda }}_b^0$ , ${\mathrm{\Lambda }}_c^{+}$ , and $\mathrm{\Lambda }$ Decay Parameters Using ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{h}^{-}$ Decays

   https://doi.org/10.1103/PhysRevLett.133.261804  

   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 (December 2024, Physical Review Letters)

   A comprehensive study of the angular distributions in the bottom-baryon decays ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{h}^{-}(h=\pi ,K)$, followed by ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{h}^{+}$with $\mathrm{\Lambda }\to p{\pi }^{-}$or ${\mathrm{\Lambda }}_c^{+}\to p{K}_{\mathrm{S}}^0$decays, is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The decay parameters and the associated charge-parity ( $CP$) asymmetries are measured, with no significant $CP$violation observed. For the first time, the ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{h}^{-}$decay parameters are measured. The most precise measurements of the decay parameters $\alpha$, $\beta$, and $\gamma$are obtained for ${\mathrm{\Lambda }}_c^{+}$decays and an independent measurement of the decay parameters for the strange-baryon $\mathrm{\Lambda }$decay is provided. The results deepen our understanding of weak decay dynamics in baryon decays. © 2024 CERN, for the LHCb Collaboration2024CERN 

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3. Leptogenesis with dynamical couplings

   https://doi.org/10.1103/PhysRevD.110.115006  

   Huang, Peisi; Xu, Tao (December 2024, Physical Review D)

   We propose a novel leptogenesis mechanism with a temperature-dependent coupling between the right-handed neutrino and Standard Model particles. This coupling experiences suppression at high temperatures and becomes sizable when the lepton asymmetry washout processes are Boltzmann-suppressed. Such a feature ensures that the washout rates remain consistently below the Hubble expansion rate, preserving all lepton asymmetry generated in the decay of right-handed neutrinos. We illustrate the feasibility of this mechanism with two example models and show that the observed baryon asymmetry of the Universe can be successfully obtained for right-handed neutrino masses larger than ${10}^9\mathrm{GeV}$as well as for smaller violation of charge-parity symmetry. Published by the American Physical Society2024 

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4. Search for Baryon Number Violation in Top Quark Production and Decay Using Proton-Proton Collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevLett.132.241802  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; Jeitler, M; et al (June 2024, Physical Review Letters)

   A search is presented for baryon number violating interactions in top quark production and decay. The analysis uses data from proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC with an integrated luminosity of $138{\mathrm{fb}}^{-1}$. Candidate events are selected by requiring two oppositely charged leptons (electrons or muons) and exactly one jet identified as originating from a bottom quark. Multivariate discriminants are used to separate the signal from the background. No significant deviation from the standard model prediction is observed. Upper limits are placed on the strength of baryon number violating couplings. For the first time the production of single top quarks via baryon number violating interactions is studied. This allows the search to set the most stringent constraints to date on the branching fraction of the top quark decay to a lepton, an up-type quark ( $u$or $c$), and a down-type quark ( $d$, $s$, or $b$). The results improve the previous bounds by 3 to 6 orders of magnitude based on the fermion flavor combination of the baryon number violating interactions. © 2024 CERN, for the CMS Collaboration2024CERN 

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5. Measurement of the branching fraction and $CP$ -violating asymmetry of the decay $B^0\to {\pi }^0{\pi }^0$ using 387 million $\mathrm{\Upsilon }\left(4S\right)$ decays in Belle II data

   https://doi.org/10.1103/PhysRevD.111.L071102  

   Adachi, I; Aggarwal, L; Ahmed, H; Aihara, H; Alhakami, M; Aloisio, A; Althubiti, N; Anh_Ky, N; Asner, D M; Atmacan, H; et al (April 2025, Physical Review D)

   We measure the branching fraction and $CP$-violating flavor-dependent rate asymmetry of $B^0\to {\pi }^0{\pi }^0$decays reconstructed using the Belle II detector in an electron-positron collision sample containing $387\times {10}^6\mathrm{\Upsilon }\left(4S\right)$mesons. Using an optimized event selection, we find $125\pm 20$signal decays in a fit to background-discriminating and flavor-sensitive distributions. The resulting branching fraction is $(1.25\pm 0.23)\times {10}^{-6}$and the $CP$-violating asymmetry is $0.03\pm 0.30$. Published by the American Physical Society2025 

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