Effect of quark sector minimal flavor violation on neutrinoless double beta decay

Abstract

The question of whether neutrino masses are Dirac or Majorana is one of the most important, and most difficult, questions remaining in the neutrino sector. Searches for neutrinoless double β-decay may help to resolve this question, but are also sensitive to new, higher dimension ∆L = 2 operators. In this paper we place two phenomenological constraints on these operators at dimension d ≤ 11. First, we require that the operators obey the quark flavor symmetries of the Standard Model, with any violation of the symmetries being due to Yukawa interactions, a scheme known as Minimal Flavor Violation (MFV). Second, we require that the operators which generate neutrinoless double β-decay, and any operators related by the flavor symmetries, do not induce neutrino masses above 0.05 eV, the limit implied by the atmospheric neutrino data. We find that these requirements severely constrain the operators which can violate lepton number, such that most can no longer contribute to neutrinoless double β-decay at observable rates. It is noteworthy that quark flavor symmetries can play such a strong role in constraining new leptonic physics, even when that physics is not quark flavor changing. Those few operators that can mimic a Majorana neutrino mass then appear with cutoffs below a TeV, and represent new physics which could be directly probed at the LHC or a future linear collider.