The decay is an ideal process in which to study flavor-conserving and violation beyond the Standard Model. We deduce the - and -odd quark operators that contribute to originating from the mass-dimension-six Standard Model effective field theory. The corresponding hadron-level operators that generate a nonvanishing amplitude at order 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 final state. By fitting the KLOE-2 and the most recent BESIII experimental data, we determine the coefficients of the lowest-order and amplitudes and estimate the potential new physics energy scale. We also perform an impact study of the future experiments. Published by the American Physical Society2024
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Deep Exclusive Electroproduction of π0 at High Q2 in the Quark Valence Regime
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A study of and decays to ( ) is performed using collision data collected by the LHCb experiment during LHC Runs 1–2, corresponding to an integrated luminosity of . The branching fractions for these decays are measured using the decay as a control channel. The decays and are observed for the first time. For decay modes with sufficient signal yields, asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for violation in the decay, interpreted as originating primarily from an asymmetric decay amplitude. The measured asymmetries for other decays are compatible with zero. © 2025 CERN, for the LHCb Collaboration2025CERNmore » « less
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