Abstract
The first direct observation of time-reversal (T) violation in the $B\bar{B}$ system has been reported by the BaBar collaboration, employing the method of Ba$\tilde {\rm n}\!$uls and Bernab\'eu. Given this, we generalize their analysis of the time-dependent T-violating asymmetry ($A_{T}$) to consider different choices of CP tags for which the dominant amplitudes have the same weak phase. As one application, we find that it is possible to measure departures from the universality of $\sin(2\beta)$ directly. If $\sin(2\beta)$ is universal, as in the Standard Model, the method permits the direct determination of penguin effects in these channels. Our method, although no longer a strict test of T, can yield tests of the $\sin(2\beta)$ universality, or, alternatively, of penguin effects, of much improved precision even with existing data sets.
Highlights
A goal of B-physics is to study the nature of CP violation and to discern, whether sources of CP violation exist beyond that of the Standard Model (SM)
We propose a more accessible way to sharpen these tests by determining effective weak-phase differences through a single asymmetry measurement; an improved test can come from existing data sets
We have described how a broader measurement program of the time-dependent asymmetry AT with generalized CP tags, possible at a B factory, can be used to measure small departures from weak-phase universality
Summary
A goal of B-physics is to study the nature of CP violation and to discern, whether sources of CP violation exist beyond that of the Standard Model (SM) This means the weak phases associated with various decays are measured to test whether they fit the SM pattern or not. We show that with specially chosen “generalized” CP tags the dominant amplitudes cancel in observables associated with AT , yielding a direct test of weak phase universality, or, alternatively, a measurement of differences of penguin pollution in the SM. These differences have been difficult to quantify [5], and our procedure gives direct access to them. We shall start by revisiting the interpretation of AT
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