Search for flavor-changing-neutral-current D meson decays

TL;DR

This paper searches for rare flavor-changing-neutral-current decays of D mesons, finding evidence for some decay modes and setting new limits on others, thereby constraining new physics models.

Contribution

It provides the first evidence for D+ to phi pi+ to mu+ mu- decays and sets the most stringent limit on D+ to pi+ mu+ mu- decay branching ratio.

Findings

Evidence for D+ to phi pi+ to mu+ mu- decays with >4 sigma significance.

No evidence for D+ to pi+ mu+ mu- decay, setting an upper limit of 3.9 x 10^-6.

Constrains new physics models affecting c to u mu+ mu- transitions.

Abstract

We study the flavor-changing-neutral-current process c to u mu+ mu- using 1.3 fb^-1 of p p bar collisions at sqrt(s) = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We see clear indications of the Ds+ and D+ to phi pi+ to mu+ mu- pi+ final states with significance greater than four standard deviations above background for the D+ state. We search for the continuum decay of D+ to pi+mu+mu- in the dimuon invariant mass spectrum away from the phi resonance. We see no evidence of signal above background and set a limit of B(D+ to pi+mu+mu-) < 3.9 x 10^-6 at the 90% C.L. This limit places the most stringent constraint on new phenomena in the c to u mu+ mu- transition.