Measuring Bs Width Difference at the Upsilon(5s) Using Quantum Entanglement

TL;DR

This paper proposes using quantum entanglement of Bs meson pairs produced at the Upsilon(5s) resonance to measure the width difference and CP phase, leveraging decay correlations and asymmetries.

Contribution

It introduces novel methods based on decay correlations and asymmetries to determine Bs meson properties using entangled states at B factories.

Findings

Time ordering asymmetry can effectively determine width difference.

Time ordering-charge asymmetry can constrain the CP mixing phase.

High-luminosity super B factories can enhance phase measurements.

Abstract

About 90% of Bs-bar Bs pairs produced at the Upsilon(5s) resonance are initially Bs*-bar Bs* pairs which decay radiatively to Bs-bar Bs. This implies that the Bs pair will then be in an eigenstate of charge conjugation (i.e. C=-1) and therefore in an entangled state. This allows for a determination of Delta Gamma/Gamma and the CP phase using a number of possible correlations between the decays of the two Bs mesons. In particular, we consider the time integrated correlation; the time ordering asymmetry and the time ordering-charge asymmetry, which in addition to time ordering distinguishes Bs from Bs-bar, for various combinations of final states. With the statistics of about O(10^7-10^8) Upsilon(5s) events available at B factories, we find that the time ordering asymmetry between suitably defined hadronic and flavor specific (tagging) decays offers a promising method for determining the width difference. The corresponding time ordering-charge asymmetry can also bound the mixing phase. Similar observables involving exclusive decays are also considered. At the super B factories with O(50) times greater luminosity time ordering and time ordering-charge asymmetries between inclusive and exclusive modes may also provide additional bounds on the phases in those decays;