Probing hidden leptonic scalar portals using the NA64 experiment at CERN

Area of Science:

• Particle Physics
• Experimental Physics
• High-Energy Physics

Background:

• The Standard Model of particle physics has limitations, motivating searches for New Physics beyond it.
• Lepton flavor anomalies, such as the muon g-2 anomaly, suggest the existence of new particles or interactions.
• Dark Sector models propose new particles and forces that interact weakly with Standard Model particles.

Purpose of the Study:

• To investigate the potential of the NA64 experiment at CERN Super Proton Synchrotron (SPS) for searching for New Physics.
• To utilize a benchmark process involving a new Dark Sector leptonic portal and a scalar boson $$ produced via lepton-flavor-changing bremsstrahlung.
• To assess the sensitivity of the NA64 experiment to probe parameter space relevant to the muon g-2 anomaly and Dark Matter relic predictions.

Main Methods:

• Development of a realistic Monte Carlo simulation of the NA64 experimental setup.
• Implementation of differential and total production cross-sections computed at exact tree-level.
• Application of the Weiszäcker-Williams phase space approximation for simulating the process $$ .

Main Results:

• The study successfully simulated the NA64 experimental setup for searching for New Physics.
• Analysis of background sources and calculation of the experiment's expected sensitivity were performed.
• Results indicate that NA64 can probe significant parameter space for a new Dark Sector leptonic portal with $$ electron-on-target (EOT).

Conclusions:

• The NA64 experiment at CERN SPS demonstrates strong potential for discovering New Physics via lepton-flavor-changing transitions.
• With minor setup optimization, NA64 can explore parameter regions consistent with the muon g-2 anomaly and Dark Matter relic density.
• This research paves the way for future explorations of lepton-flavor-changing interactions at NA64.