Production of like sign dileptons in p-p collisions through composite Majorana neutrinos - art. no. 015013

The production of like-sign dileptons (LSD) in the high-energy lepton-numbe r-violating (Delta L = + 2) reaction pp-->2 jets + l(+) l(+) (l = e,mu,tau) , of interest for experiments to be performed at the forthcoming CERN Large Hadron Collider (LHC), is investigated in detail, taking up a composite mo del scenario in which the exchanged virtual composite neutrino is assumed t o be a Majorana particle that couples to the light leptons via the SU(2) x U(1) gauge bosons through a magnetic type coupling (sigma(mu nu)). A helici ty projection method is used to evaluate exactly the tree-level amplitudes of the contributing parton subprocesses (2-->4), which allows one to take i nto account all exchange diagrams and occurring interferences. Numerical es timates of the corresponding signal cross section that implement kinematica l cuts needed to suppress the standard model background are presented which show that in some regions of the parameter space the total number of LSD e vents is well above the background. Assuming nonobservation of the LSD sign al it is found that LHC would exclude a composite Majorana neutrino up to a pproximate to 900 GeV (if one requires 10 events for discovery). The sensit ivity of LHC experiments to the parameter space is then compared to that of the next generation of neutrinoless double beta decay (beta beta(0 nu)) ex periment, GENIUS, and it is shown that they will provide constraints of the same order of magnitude and will play a complementary role.