Search for Heavy Majorana Neutrinos at LHC using Monte Carlo simulation

Heavy neutrinos can be discovered at LHC. Many extensions for Standard Model predict by existing of new neutrino has a mass at high energies at LHC. B-L model one of them that predict by existence three heavy (right-handed) neutrinos one per generation, new gauge massive boson and new scalar Higgs boson rather than SM Higgs. In this work we search for heavy neutrino in 4 leptons + missing energy final state events produced in proton-proton collisions at LHC using data produced from Monte Carlo simulation for B-L model at different center of mass energies. We predict that the heavy neutrinos pairs can be produced from Z' B-L new gauge neutral massive boson decay and then the heavy neutrino pairs can decay to 4 leptons + missing energy final state which give us an indication for new signatures of new physics beyond Standard Model at higher energies at LHC for B-L extension of Standard Model .


I. INTRODUCTION
Standard Model of elementary particles needs an extension to explain some facts. One of these facts is that the neutrinos are massive. B − L model (baryon number minus lepton number) [1] is a simple extension of the Standard Model which plays an important role in various physics scenarios beyond the Standard Model (SM). Firstly, the gauged U (1) B−L symmetry group is contained in a Grand Unified Theory (GUT) described by a SO(10) group. Secondly, the scale of the B − L symmetry breaking is related to the mass scale of the heavy right-handed Majorana neutrino mass [2][3] terms providing the well-known see-saw mechanism of light neutrino mass generation. Three heavy singlet (righthanded) neutrinos v h are invoked. B − L symmetry breaking has been considered, based on the gauge group. The model under consideration B − L symmetry-breaking is based on the gauge group G B-L =SU(3) C × SU(2) L × U(1) Y × U(1) B-L This model provides a natural explanation for the presence of three right-handed neutrinos [4] and can account for the current experimental results of the light neutrino masses and their mixings. The heavy neutrinos are rather long-lived particles producing distinctive displaced vertices that can be seen in the detectors. Lastly, the simultaneous measurement of both the heavy neutrino mass and decay length enables an estimate of the absolute mass of the parent light neutrino. An attractive feature of the B−L model is that a successful realization of the mechanism of baryogenesis through leptogenesis to explain the observed matter-antimatter asymmetry depends on two main parameters, the mass of L B Z − ′ and the coupling constant g' 1 . Therefore, the model B-L is controlled by two parameters:

A. Branching Ratios of Heavy neutrinos
The heavy neutrino has a small mixing with the light neutrino and so it provide very small couplings to gauge and Higgs bosons which gives all the decay is the highest ratio in comparison with the other decay channels. Also, the ratio of the decay channel BR(v h → H 1 + v) increase with increasing the heavy neutrino mass and the decay channel v h → z + v has a high percent level at heavy neutrino mass of 200GeV . The ratio of v h → H 2 + v decay channel is very small and we can neglect it.

B. Production cross sections
In this section we determine the production cross section of heavy neutrino discovery at LHC for various CM energies, 5,7,10 and 14 TeV using MadGraph5/ MadEvent and PYTHIA8 programs [7-9]. We consider the production channel of heavy neutrino pair production via the Where N is the number of events and L is the total integrated luminosity and s is the production cross section. Also we can deduce from fig. 3 that the production section depends on the L B Z − ′ boson mass and the value of the g' 1 coupling and as we will see later in addition to the LHC CM energy.  The dominant production mode for the heavy neutrinos at the LHC will be through the Drell-Yan mechanism [10] with L B Z − ′ in the s-channel.

C. Heavy neutrino decays
The detection of the signal coming from the pair production of the heavy neutrinos in the B-L model at LHC will be through very clean signal for four charged leptons in the final states and missing energy due to the associated neutrinos .The first heavy neutrino dominant decay is to a W + boson and a charged lepton here is e + and the second heavy neutrino decays to Z boson and a light neutrino. We can have the following final states as our signal (see fig.8

FIG. 8.
Feynman diagram for heavy neutrino pair production and its decay in B-L model. In our simulation for heavy neutrino detection at LHC using MadGraph5/Madevent and PYTHIA8 we will put some kinematics cuts to be taken into account when selecting the final states with four leptons and missing energy (momentum):  Fig.(10) represent the transverse momentum for different leptons (electron and muon) produced for the decay of different heavy neutrino masses and we note that the electron has a higher momentum than muon where the electron comes from primary decay of the heavy neutrino while the muon comes from the Z boson decay which basically comes from one of heavy neutrino pair. The missing P T distribution in Fig. 11 represents the light neutrinos in the final state where one light neutrino come from the primary decay of the heavy neutrino and another one comes from W boson decay and these two light neutrinos act as missing energy from heavy neutrino pair decay.

III. CONCLUSION
In this work we have presented an analysis For LHC discovery potential for the heavy neutrino in TeV scale using B -L extension of the SM. We analyzed the phenomenology using Monte Carlo simulation data produced from MadGraph5/ Madevent, PYTHIA8 and Calchep and we used ROOT data analysis program to produce different curves for the relationship between specific parameters. From our simulation for this process one can search for heavy neutrinos via a very clean signal for four charged leptons and missing energy at LHC.