Large forward-backward asymmetry in B -> K mu(+) mu(-) from new physics tensor operators

Abstract

We study the constraints on possible new physics contributions to the forward-backward asymmetry of muons, A(FB)(q(2)), in B -> K mu(+) mu(-). New physics in the form of vector/axial-vector operators does not contribute to A(FB()q(2)), whereas new physics in the form of scalar/pseudoscalar operators can enhance A(FB)(q(2)) only by a few percent. However, new physics in the form of tensor operators can take the peak value of A(FB)(q(2)) to as high as 40% near the high-q(2) end point. In addition, if both scalar/pseudoscalar and tensor operators are present, then A(FB)(q(2)) can be more than 15% for the entire high-q(2) region q(2) > 15 GeV(2). The observation of significant AFB would imply the presence of new physics tensor operators, whereas its q(2) dependence could further indicate the presence of new scalar/pseudoscalar physics.