Probing minimal supergravity in the type-I seesaw mechanism with lepton flavor violation at the CERN LHC

Abstract

The most general supersymmetric seesaw mechanism has too many parameters to be predictive and thus can not be excluded by any measurements of lepton flavour violating (LFV) processes.We focus on the simplest version of the type-I seesaw mechanism assuming minimal supergravity boundary conditions. We compute branching ratios for the LFV scalar tau decays,τ 2 → (e, µ)+χ 0 1 , as well as loop-induced LFV decays at low energy, such as l i → l j + γ and l i → 3l j , exploring their sensitivity to the unknown seesaw parameters. We find some simple, extreme scenarios for the unknown right-handed parameters, where ratios of LFV branching ratios correlate with neutrino oscillation parameters. If the overall mass scale of the left neutrinos and the value of the reactor angle were known, the study of LFV allows, in principle, to extract information about the so far unknown right-handed neutrino parameters.

SPheno 3.1: extensions including flavour, CP-phases and models beyond the MSSM

“…The parameters are set using the blocks MNURIN and YNU0IN, see sections 6.2.2 and 6.2.7, respectively. Using this the results of [8,9] have been obtained.…”

“…The parameters are set using the blocks MNURIN and YNU0IN, see sections 6.2.2 and 6.2.7, respectively. Using this the results of [8,9] have been obtained.• In case of a pair of SU (5) 15-plets a second variant has been implemented using the complete 2-loop RGEs and corresponding threshold corrections at the seesaw scale as described in [14]. Here the blocks Higgs3IN and YTIN have to be used to transfer the data, see sections 6.2.1 and 6.2.9.…”

Probing the supersymmetric type III seesaw: LFV at low-energies and at the LHC

“…Let us begin by noticing that if some components of the seesaw mediators are not singlets under the SM gauge group (which is the case in type II and III seesaws), the latter can leave an imprint on the SUSY spectrum, since they can modify the supersymmetric β-functions governing the evolution of the gauge couplings and soft-SUSY breaking parameters. At the LHC, SUSY seesaws can also give rise to several LFV signals: firstly, one can have sizable widths for LFV decay processes like χ 0 2 → χ 0 1 ℓ ± i ℓ ∓ j [38,[41][42][43][44]; secondly, one can have observable flavoured slepton mass splittings (MS), ∆ml/ml (ẽ L ,μ L ) and possibly ∆ml/ml (μ L ,τ 2 ). These splittings can be identified since, under certain conditions, one can effectively reconstruct slepton masses via observables such as the kinematic end-point of the invariant mass distribution of the leptons coming from the cascade decays χ 0 2 →l ± ℓ ∓ → χ 0 1 ℓ ± ℓ ∓ .…”

Lepton flavour violation: physics potential of a Linear Collider

“…Moreover, cLFV has also been studied in high-energy observables [40][41][42][43][44][45][46][47][48][49][50][51][52], as those that can be probed at the LHC as, for instance, lepton flavour violating neutralino decays and slepton mass splittings. The impact of a type I seesaw on the SUSY Higgs spectrum has been recently discussed in [53].…”

“…Nevertheless, numerous slepton-dedicated studies have been conducted for the LHC, in particular focusing on the case in which sleptons are produced from gaugino decays. Hence, the studies of cLFV observables are necessarily associated with specific decay chains that only occur in (reduced) regions of the SUSY parameter space: in general, cLFV is studied through dilepton mass distributions (m ℓℓ ) of χ 0 2 → ℓ i ℓ j χ 0 1 , via observables such as additional edges in m ℓℓ and slepton mass splittings (see, for example [42,[44][45][46][47][48][49][50]). …”