Using $B^0_s\to D_s^\mp K^\pm$ Decays as a Portal to New Physics

Abstract

The system of B 0 s → D ∓ s K ± decays offers a theoretically clean determination of the angle γ of the Unitarity Triangle. A corresponding LHCb analysis resulted in a surprisingly large result, which is in tension with other determinations and global analyses of the Unitarity Triangle. Paying special attention to discrete ambiguities, we confirm this picture and resolve a final ambiguity. Moreover, we extract the branching ratios of the underlying B0 s → D + s K − and B0 s → D − s K + modes. Combining them with information from semileptonic B (s) decays, we arrive at another puzzling situation, which we obtain also for other decays with similar dynamics. These patterns could be footprints of New Physics in the b → cūs and b → ucs processes which govern the dynamics of the B0 s → D ∓ s K ± channels. We present a model-independent strategy to reveal such effects. Applying it to the present data, we obtain strongly correlated New-Physics contributions with potentially large CP-violating phases. We find that new contributions sizeably smaller than the Standard Model amplitudes could actually accommodate the current data. This strategy offers an exciting probe for new sources of CP violation at the future high-precision frontier of B physics.

Revealing New Physics in $B^0_s\to D_s^\mp K^\pm$ Decays

“…• ; the solutions modulo 180 • can be excluded as δ s ∼ 180 • would be in huge conflict with factorization predicting δ s ∼ 0 • [9]. Therefore, we find excellent agreement between this transparent picture and the LHCb fit.…”

“…( 1) and its CP conjugate allow a theoretically clean determination of the angle γ of the Unitarity Triangle (UT) of the CKM matrix [1][2][3]. Performing these measurements and assuming certain SM relations, LHCb [4] has reported the result γ = 128 +17 Inspired by the challenge of interpreting this result, we shed more light on the determination of γ and the associated parameters, confirming the LHCb picture and excluding the modulo 180 • ambiguity [9]. We move on to extract the individual B0 s → D + s K − and B 0 s → D + s K − branching ratios and confront them with the SM interpretation, developing a method to minimize dependences on non-perturbative and CKM parameters.…”

“…Using (3) with the measured value of C, we find | ξ| = 0.40 ± 0.13. Introducing the S ± ≡ (S ± S)/2 and A ∆Γ + ≡ (A ∆Γ + A ∆Γ )/2 combinations, we obtain the following relations [2,3,9]:…”

“…Moreover, we have to disentangle the interference effects between the two decay paths that arise from the B 0 s -B0 s oscillations. We obtain for the theoretical branching ratios [9]:…”

Testing the Standard Model with CP-asymmetries in flavour-specific non-leptonic decays

“…[27,45,47], with results revealing that there is a sizable allowed parameter space for new effects, which do not violate any theoretical or experimental bound. More recently such effects have also been investigated for the case of the decay Bs → D + s K − [48,49]. BSM explanations have been considered in [3,50] and challenged by collider bounds in [51].…”