Lepton number violation in heavy Higgs boson decays to sneutrinos

Abstract

We study the possibility of observing lepton number violation in the right-handed sneutrino sector of the Next-to-Minimal Supersymmetric Standard Model extended with right-handed neutrinos. The scalar potential introduces a lepton number violating mass term for the right-handed sneutrinos, which generates a phase difference between the sneutrino and antisneutrino. If we have light higgsinos and right-handed sneutrinos, the sneutrino decay width is determined by the tiny Yukawa couplings, which allows the phase difference between the sneutrino and antisneutrino states to accumulate before the sneutrino decay. We investigate the possibilities of producing sneutrino pairs resonantly through a heavy Higgs of such a model and the ability of seeing a lepton number violating signature emerging from sneutrinos at the Large Hadron Collider. We also discuss how a possible future signal of this type could be used to determine the neutrino Yukawa couplings. * S.

Impact of leptonic unitarity and dark matter direct detection experiments on the NMSSM with inverse seesaw mechanism

“…We showed by both analytic formulas and numerical calculations that the resulting theory (abbreviated as ISS-NMSSM hereafter) was one of the most economic framework to generate the neutrino mass and, meanwhile, to reconcile the DM DD experiments naturally [8,14]. We add that, besides us, a lot of authors have showed interest in the sneutrino DM in recent years [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], but none of them considered the same theoretical framework as ours.…”

Extraction of neutrino Yukawa parameters from displaced vertices of sneutrinos

“…The complete cutflow is presented in table 3 displacement requirement rejects almost all of the signal of BP-II. For such a case the prompt signature can still be visible -this is actually BP3 of [21] for which a cut-based analysis gave a ∼ 3σ excess. From table 3 it is interesting to note that even though the cuts C4 and C5 do not reduce the dominant backgrounds, however, they are important to reduce the sub-dominant backgrouds like WZ, ZZ, tW, tZ and ttZ processes where both prompt and displaced leptons can be present.…”

“…If tan β > 1.5, the heavy Higgs state has a stronger coupling to sneutrinos. If λ and λ N are large, RH sneutrinos can be pair produced through the heavy Higgs portal and they can be detected through lepton-number violating signatures [21,22]. The singlet field is essential in achieving this as in the MSSM with RH neutrinos the Higgs-RH sneutrino couplings would not exist.…”

“…As the seesaw mechanism has a source of lepton number violation, we get both opposite-sign and same-sign dileptons, the latter giving better discovery potential due to smaller backgrounds. Remarkably, the aforementioned mass degeneracy may make the sneutrinos long lived, so that the visible tracks of this signature may be displaced, which in turn implies a smaller background with respect to the one affecting similar prompt signatures [21,22]. Here we shall prove that this signature with two DVs can be extracted at the LHC and, moreover, we shall also show how the kinematics of the displaced (visible) tracks could allow for a measurement of the (s)neutrino Yukawa couplings, thereby enabling one to probe the underpinning neutrino mass generation dynamics.…”

Exploring Neutrino Physics through Sneutrinos

“…The importance of this for neutrino physics is that due to supersymmetry, sneutrinos inherit the interactions of neutrinos and hence the observation of a sneutrino signal could give us information about the neutrino mass generation mechanism. Here we construct an explicit example of such a case based on our work [6].…”