Abstract
Anomalies in decays induced by ( ) transitions may imply lepton flavor universality violations, which raises questions on such phenomena in the D decays induced by transitions. Current measurements of the pure leptonic and semi-leptonic D decays agree with the standard model (SM) predictions, and such agreements can be used to constrain the new physics (NP) contributions. In this work, we extend SM by assuming general effective Hamiltonians describing the transitions including the full set of the four-fermion operators. With the latest experimental data, we perform a least fit of the Wilson coefficient corresponding to each operator. The results indicate that the Wilson coefficients of tensor and scalar operators in the muon sector are in the order of while others are in the order of . The lepton flavor universality could be violated by interactions with the scalar operators. We also determine that the pure leptonic decays are significantly sensitive to scalar operators. The effects of NP on the semi-leptonic decays with electron final state are negligible; however, for the decays with the muon final state, the effects of scalar and tensor operators will appear in the forward-backward asymmetries and the muon helicity asymmetries of decays. The future measurements of these decays in the BESIII and Belle II experiments will facilitate the evaluation of NP effects.
Highlights
Despite the discovery of the Higgs boson, the standard model (SM) is still regarded as the low-energy effective theory of a more fundamental one, because SM cannot explain the matterantimatter asymmetry in the universe, it has not a dark matter candidate and it does not explain its own gauge group structure
One of the most important tasks in the particle physics community is searching for the new physics (NP) beyond SM, which can be examined via probing for NP signals directly at the higher energy colliders or testing SM with high precision at high intensity machines indirectly
As for the indirect approaches, the rare processes induced by flavor-changing neutral-current (FCNC) are generally considered to be an ideal plate to search NP, because FCNC only occurs by loops in SM and the branching fractions can be enhanced by new particles
Summary
Despite the discovery of the Higgs boson, the standard model (SM) is still regarded as the low-energy effective theory of a more fundamental one, because SM cannot explain the matterantimatter asymmetry in the universe, it has not a dark matter candidate and it does not explain its own gauge group structure. The SM predictions of the semileptonic decays based on the LQCD [22] are in agreement with the world average experimental measurements [23] with large uncertainties from the CKM matrix elements. Such consistencies can be used to constrain the parameter spaces of NP [24] or testing NP models. Based on the general framework of the four-fermion effective field theory, we will perform a minimum χ2 fit of the Wilson coefficient of each operator to the latest experimental data With these obtained Wilson coefficients, we present the predictions of other observables for testing in the future experiments.
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