New Measurements Using External Photon Conversion at a High Luminosity B Factory

TL;DR

This paper proposes two new methods using external photon conversion at a high-luminosity B factory to measure CP violation and photon polarization, aiming to test the standard model and explore new physics.

Contribution

It introduces novel experimental techniques for measuring CP violation parameters and photon polarization in B decays at high-luminosity B factories.

Findings

Estimated precision of S_{pi^0pi^0} is 0.23 with 50 billion BBbar pairs.

Demonstrated potential to reduce ambiguity in CKM angle phi_2.

Proposed methods to detect right-handed currents beyond the standard model.

Abstract

We propose two novel methods for testing the standard model using external photon conversion at a high-luminosity e^+e^- B factory proposed recently. The first method is to measure the mixing-induced CP-violation parameter S_{pi^0pi^0} in B^0 --> pi^0 pi^0 decays. The precision of S_{pi^0pi^0} is estimated to be 0.23 from a Monte Carlo study for a data sample containing 50 x 10^9 BBbar pairs. We demonstrate that this measurement is crucial for reducing the discrete ambiguity of the Cabibbo-Kobayashi-Maskawa angle phi_2 determined from the isospin analysis with B --> pi pi decays. The second method is to measure photon polarization in B^0 --> K^{*0}(--> K^+ pi^-) gamma decays using the external photon conversion, and combine it with S_{K^{*}gamma} from B^0 --> K^{*0}(--> K^0_S pi^0) gamma decays. This offers a promising way of determining the hypothetical right-handed current amplitude and phase beyond the standard model.