Speaker
Nathan Papapietro
(University of Alabama)
Description
We propose a simple gauged U(1)B−L extension of the minimal supersymmetric Stan-
dard Model (MSSM), where R-parity is conserved as usual in the MSSM. The global B − L (baryon
minus lepton number) symmetry in the MSSM is gauged and three MSSM gauge-singlet chiral
multiplets with a unit B − L charge are introduced, ensuring the model free from gauge and gravi-
tational anomalies. We assign an odd R-parity for two of the new chiral multiplets and hence they
are identified with the right-handed neutrino superfields, while an even R-parity is assigned to the
other one. The scalar component of the R-parity even superfield plays the role of a Higgs field and
the U(1)B−L symmetry is radiatively broken by a negative mass squared of the scalar generated by
the renormalization group running of soft supersymmetry (SUSY) breaking parameters. Therefore,
the scale of the U(1)B−L symmetry breaking is controlled by the SUSY breaking parameters and
naturally be at the TeV scale. Because of our novel R-parity assignment, three light neutrinos
are Dirac particles with one massless state. Since R-parity is conserved, the lightest superpartner
(LSP) neutralino is a prime candidate of the cosmological dark matter. Depending on its mass, the
lighter Majorana mass eigenstate of a mixture of the B − L gaugino and the fermionic component
of the R-parity even superfield appears as a new dark matter candidate. We also discuss collider
phenomenology of our model. In particular, the B − L gauge boson (Z ), once discovered at the
Large Hadron Collider, will be a novel probe of the Dirac nature of the light neutrinos since its
invisible decay processes include the final states with one massless (left-handed) neutrino and two
Dirac neutrinos, in sharp contrast with usual B − L extension of the SM or MSSM, where the
right-handed neutrinos are heavy Majorana particles and decay to the SM leptons.
Primary authors
Nathan Papapietro
(University of Alabama)
Dr
Nobuchika Okada
(University of Alabama)
