Direct CP violation in Cabibbo-favored charmed meson decays and ϵ′/ϵ in SU(2)L × SU(2)R × U(1)B−L model

Abstract

Since the standard model contribution is virtually absent, any observation of direct CP violation in the Cabibbo-favored charmed meson decays would be evidence of new physics. In this paper, we conduct a quantitative study on direct CP violation in D 0 → K − π + , D + s → ηπ + and D + s → η π + decays in the SU(2) L ×SU(2) R ×U(1) B−L gauge extension of the standard model. In the model, direct CP violation arises mainly from the interference between the decay amplitude coming from the SM left-left current operators and that from the right-right current operators induced by W + R gauge boson exchange. Interestingly, the strong phase between the two amplitudes is evaluable, since it stems from difference in QCD corrections to the left-left and right-right current operators, which is a short-distance QCD effect given by ∼ (α s (M 2 W L )/4π) log(M 2 W R /M 2 W L ). We assess the maximal direct CP violation in the above decays in the SU(2) L ×SU(2) R ×U(1) B−L model. Additionally, we present a correlation between direct CP violation in these modes and one in K → ππ decay parametrized by , since W + R gauge boson has a sizable impact on the latter.

Isospin-violating contributions to ∈′/∈

“…Large-N C parameters K Z i ) ∞ LECs in Eq. (35).The large-N C predictions for the electroweak LECs (g 8 Z i ) ∞ in Eq (35). are governed by the constants K…”

Anatomy of $$\varepsilon '/\varepsilon $$ ε ′ / ε beyond the standard model

“…2.4. Via CKM rotations, many of the operators in (38) are thus related to S = 1 operators. 13 Note that the signs on the right-hand sides of (36) depend on the sign convention for the covariant derivative.…”

“…In specific NP models one often finds correlations between BSM contributions to ε /ε and rare kaon decays, in particular with K + → π + νν and K L → π 0 νν. In fact in all papers that addressed the ε /ε anomaly listed in the introduction [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] such correlations have been investigated. Such correlations will play an important role in distinguishing various models when the theoretical status of ε /ε improves and the branching ratios for rare kaon decays will be well measured.…”

“…as well as modified Z 0 and W ± couplings. The correlation of ε /ε and CP asymmetries in CF decays D 0 → K − π + , D + s → ηπ + and D + s → η π + has been discussed [38] in the framework of a SU (2) L ⊗ SU (2) R ⊗ U (1) B−L symmetric model. The correlation with CP asymmetries in the SCS decays D 0 → K + K − and D 0 → π + π − has been discussed in a general EFT framework in [98].…”

“…These include in particular tree-level Z exchanges with explicit realization in 331 models [22,23] or models with tree-level Z 0 exchanges [24,25] with explicit realization in models with mixing of heavy vector-like fermions with ordinary fermions [26] and the Littlest Higgs model with T-parity [27]. Also simplified Z scenarios [28,29], the MSSM [30][31][32][33][34], the type-III Two-Higgs Doublet model (2HDM) [35,36], a SU (2) L ⊗ SU (2) R ⊗ U (1) B−L model [37,38] and the one based on SU(8) symmetry [39] are of help here. On the other hand, as demonstrated in [40], it is very unlikely that leptoquarks are responsible for the ε /ε anomaly when the constraints from rare semi-leptonic and leptonic K decays are taken into account.…”