The effect of S-wave interference on the B0→k*0l+l- angular observables

The rare decay B-0 -> k(*0)l+l(-) is a avour changing neutral current decay with a high sensitivity to physics beyond the Standard Model. Nearly all theoretical predictions and all experimental measurements so far have assumed a K*(0) P- wave that decays into the K+ fi nal state. In this paper the addition of an S- wave within the K+pi- system of B-0 -> k(*0)l+l(-) and the subsequent impact of this on the angular distribution of the fi nal state particles is explored. The inclusion of the S- wave causes a distinction between the values of the angular observables obtained from counting experiments and those obtained from fi ts to the angular distribution. The e ff ect of a non- zero S- wave on an angular analysis of B-0 -> k(*0)l+l(-) is assessed as a function of dataset size and the relative size of the Swave amplitude. An S- wave contribution, equivalent to what is measured in B-0 -> J/psi K*(0) at BaBar, leads to a signi fi cant bias on the angular observables for datasets of above 200 signal decays. Any future experimental analysis of the K+pi(-)l(+)l(-) fi nal state will have to take the S- wave contribution into account.