Measuring Time Dependent Asymmetries with Radiative Penguin Decays.

Introduction

I want to consider the following two decay channels:

• B⁰®K^*0+g where K^*0®Ks+p⁰ and Ks®p⁺p^-.
• B⁰®r⁰+g

In the Standard Model, the time-dependent asymmetry in such channels is predicted to be very small:

• B⁰®K^*0+g : A(t)~2m_s/m_b sin2bcosDmt
• B⁰®r⁰+g : A(t) ~ 0

However, in other models, the asymmetry may be as large as 50%.

Hence, if we observe a large asymmetry in these channels, this would be clear evidence of physics beyond the Standard Model.

Feasibility Study

How much data do we need to make a meaningful measurement of the time dependent asymmetry in these channels?

By next summer we should have O(100fb^-1) on tape.

B⁰®K^*0+g channel

• Using the reconstruction efficiencies obtained for the branching fraction analysis on run 1 data, we expect ~70 events in the B⁰®K^*0+g channel.
• However, this is probably a lower limit:
• The Ks efficiency should be higher in run 2.
• The analysis was optimized for a branching fraction analysis (meaning it was necessary to have a selection with a well known efficiency).
• Dominant background comes from continuum events.
• Background ~10% level.
• Should make fitting easy as there is basically no background with a finite lifetime.
• CP vertex might be difficult to reconstruct:
• Relies only on the Ks.
• Needs some study.

B⁰®r+g channel

• There should also be about 70 events from this channel.
• Branching fraction analysis is less well advanced.
• Vertex well defined.

Can both channels be fitted together? They have different asymmetries in the Standard Model.

Work in Progress

• Reproducing the B⁰®K^*0+g branching fraction analysis on signal Monte Carlo.
• Interfacing this to tagging package to start studying tagging and vertexing on this sample.
• Have a go at fitting the MC events.