EnhancedCPViolation withB→KD0(D¯0)

Abstract

The Gronau-London-Wyler (GLW) method extracts the CKM angle γ by measuring B ± decay rates involving D 0 /D 0 mesons. Since that method necessitates the interference between two amplitudes that are significantly different in magnitude, the resulting asymmetries tend to be small. CP violation can be greatly enhanced for decays to final states that are common to both D 0 and D 0 and that are not CP eigenstates. In particular, large asymmetries are possible for final states f such that D 0 → f is doubly Cabibbo suppressed while D 0 → f is Cabibbo allowed. The measurement of interference effects in two such modes allows the extraction of γ without prior knowledge of, which may be difficult to determine due to backgrounds.One striking implication of the standard model with three families is that it can accommodate CP violation via the Kobayashi-Maskawa mechanism [1]. Intense experimental efforts are now underway in B-physics to test the standard model in this regard through measurements of the unitarity triangle [2]. For this program to succeed it is of crucial importance to be able to deduce each of the angles of this triangle from experiment. In this paper we will focus our attention to one of the three angles, namely γ.We recall that in the standard model, b → cus and b → cus transitions have a relativeCabibbo-Kobayashi-Maskawa (CKM) phase γ. In order to measure CP violation due to this phase, a means must be found to have these seemingly distinct final states interfere. A mechanism whereby this is possible has been proposed and extensively studied [3,4,5,6,7,8].

Universal unitarity triangle and physics beyond the standard model

“…Variants of the latter method which could be more promising experimentally have been proposed in [23,24].…”

LHCb strategies for γ from

“…Atwood, Dunietz and Soni (ADS) [7] suggested a method of determining γ based on the reconstruction of non-CP eigenstates for decays common to both D 0 andD 0 . An example is the hadronic final state Kπ, which may arise from the Cabibbo favoured (CF) decayD 0 → K + π − or the doubly-Cabibbo suppressed (DCS) decay…”

B-Physics at the LHC

“…In the GLW [15,16] strategy, the D 0 decays into a CP eigenstate, and the sensitivity to γ comes from the interference between dominant and doubly colour-suppressed decays. The ADS [17] strategy combines colour-suppressed B decays with colour-favoured D decays (and vice versa), thus increasing the interference effects. The GGSZ [18] strategy uses a Dalitz analysis of D 0 → K S ππ decays to extract γ together with the strong phases in the D 0 decay.…”