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تسجيل مستخدم جديدRescattering effects in the hadronic-light-by-light contribution to the anomalous magnetic moment of the muon
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We present a first model-independent calculation of $pipi$ intermediate states in the hadronic-light-by-light (HLbL) contribution to the anomalous magnetic moment of the muon $(g-2)_mu$ that goes beyond the scalar QED pion loop. To this end we combine a recently developed dispersive description of the HLbL tensor with a partial-wave expansion and demonstrate that the known scalar-QED result is recovered after partial-wave resummation. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, $a_mu^{pitext{-box}}=-15.9(2)times 10^{-11}$. We then construct suitable input for the $gamma^*gamma^*topipi$ helicity partial waves based on a pion-pole left-hand cut and show that for the dominant charged-pion contribution this representation is consistent with the two-loop chiral prediction and the COMPASS measurement for the pion polarizability. This allows us to reliably estimate $S$-wave rescattering effects to the full pion box and leads to our final estimate for the sum of these two contributions: $a_mu^{pitext{-box}} + a_{mu,J=0}^{pipi,pitext{-pole LHC}}=-24(1)times 10^{-11}$.
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