Light top squarks in aU(1)Rlepton number model with a right handed neutrino and the LHC

Abstract

Light top squarks in U (1) R lepton number model with a right handed neutrino and the LHC We investigate the phenomenology of top squarks at the Large Hadron Collider (LHC) in a supersymmetric model where lepton number is identified with an approximate U (1)R symmetry in such a way that one of the left chiral sneutrinos can acquire a large vacuum expectation value (vev) and can play the role of the down-type Higgs. This R-symmetry allows a subset of trilinear R-parity violating interactions, which determine the collider phenomenology of this model in a significant way. The gauginos are Dirac particles and gluinos are relatively heavy in this class of models. The model contains a right handed neutrino superfield, which gives a tree level mass to one of the active neutrinos. An order one neutrino Yukawa coupling also helps enhance the Higgs boson mass at the tree level and results in a very light bino-like neutralino ( χ 0 2 ) with mass around a few hundred MeV, which is a carrier of missing (transverse) energy (✚ ET ). The model can accommodate two rather light top squarks, compatible with the observed mass of the Higgs boson. The lighter top squark ( t1) can decay into t χ 0 2 , and thus the signal would be similar to the signal of top quark pair production at the LHC. In addition, fully visible decays such as t2 → be + can give rise to interesting final states. Such signals at the LHC combined with other features like a heavy gluino could provide a strong evidence for this kind of a model. Our analysis shows that m t 1 < ∼ 575 (750) GeV and m t 2 < ∼ 1.2 (1.4) TeV can be probed with 5σ statistical significance at the 13 TeV LHC with 300 (3000) fb −1 of integrated luminosity. Finally, we observe that in the presence of super-light carriers of ✚ ET , the so-called 'stealth' top squark scenario may naturally appear in our model. I. INTRODUCTIONThe discovery of a Higgs boson at the Large Hadron Collider (LHC) with a mass around 125 GeV [1, 2] is of immense importance in high energy physics and, in particular, in the context of electroweak symmetry breaking. However, in spite of its enormous success over the years, the Standard Model (SM) of particle physics suffers from several drawbacks. From a theoretical perspective, the naturalness problem remains a troublesome issue in the framework of SM. Supersymmetry (SUSY) renders an elegant solution to this problem and has become the most popular choice for physics beyond the standard model (BSM) to date. Nevertheless, searches for superpartners by the LHC collaborations (ATLAS and CMS) in pp collisions at the centre-of-mass energies of √ s = 7 TeV and 8 TeV have shown no significant excess [3,4] over the SM background. This has put stringent lower limits on the superpartner masses in many different SUSY scenarios. Recent experimental analyses within the framework of a simplified phenomenological minimal supersymmetric standard model (pMSSM) have set a lower bound of 1.7 TeV [5] for comparable masses of the gluino and the first two generation squarks.On top of that, find...

Natural emergence of neutrino masses and dark matter from R-symmetry

“…The R-charges are now identified with the lepton number of the SM fields. In general, we have the freedom to cast these charges and one can look into other assignments in [12][13][14][15][16][17][18][19][20]. An outcome of our R-charge assignment is the presence of bilinear and trilinear "R-parity violating" terms in the superpotential which are Rsymmetric.…”

Probing a slepton Higgs on all frontiers

“…For the B = 1/3 or L = 1 cases there are extra terms, but we do not discuss them here. In the case L = 1, the details of which can be found in [19,28].…”

“…and still avoid phenomenological bounds. This intriguing possibility has been discussed in several recent papers: see [16,19,27] for model building, [28] for stop phenomenology, and [29] for a suggested explanation of the recent eejj, eνjj excess [30,31] as well as further discussion on light squark phenomenology. For the purpose of this work we will focus on the possibility that the Higgs doublet is identified with the selectron doublet, though much of our discussion will be more general.…”

Light top squarks in $U(1)_{R}$-lepton number model with a right handed neutrino and the LHC

“…Our preliminary study reveals that the corresponding rate could barely reach an attobarn level at the 13 TeV run of the LHC and thus one needs to wait for a very high integrated luminosity. A detailed analysis in this context is beyond the scope of this paper and we postpone it for a future work [85].…”