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

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;