5. Theoretical Physics (CSN4)

Nondecoupling supersymmetry and an Lμ − Lτ gauge boson at Belle-II

by Heerak Banerjee (School of Physical Sciences, Ass.Cultivation Science)

Aula Seminari (LNF)

Aula Seminari


Via Enrico Fermi, 40 00044 Frascati (Roma)

The presence of kinetic mixing is an essential feature of any model that augments the Standard Model gauge symmetry with an additional U(1) symmetry . We look at the signal process, e+eγZγ+E/ at Belle-II, which is an outcome of this ubiquitous feature. We propose that the γ+E/ signal at the Belle-II detector will be a smoking gun for supersymmetry (SUSY) in the presence of a gauged U(1)LμLτ symmetry. A striking consequence of breaking the enhanced symmetry appearing in the limit of degenerate (s)leptons is the nondecoupling of the radiative contribution of heavy charged sleptons to the γ Z kinetic mixing. We take into account the severe constraints on gauged U(1)LμLτ models by several low-energy observables (like the muon (g 2), data from the CCFR and BaBar collaborations, etc.) and show that any significant excess in all but the highest photon energy bin would be an undeniable signature of such heavy scalar fields in SUSY coupling to the Zgauge boson. The number of signal events depends crucially on the logarithm of the ratio of stau to smuon mass in the presence of SUSY. In addition, the number is also inversely proportional to the e+ ecollision energy, making a low-energy, high-luminosity collider like Belle-II an ideal testing ground for this channel. This process can probe large swathes of the slepton mass ratio vs the additional gauge coupling (gX ) parameter space. More importantly, it can explore the narrow slice of MZgX parameter space still allowed in gauged U(1)LμLτ models for superheavy sparticles.