Muon g -2 and searches for a new leptophobic sub-GeV dark boson in a missing-energy experiment at CERN
Abstract
The 3.6 σ discrepancy between the predicted and measured values of the anomalous magnetic moment of positive muons can be explained by the existence of a new dark boson Zμ with a mass in the sub-GeV range, which is coupled predominantly to the second and third lepton generations through the Lμ-Lτ current. After a discussion of the present phenomenological bounds on the Zμ coupling, we show that if the Zμ exists, it could be observed in the reaction μ +Z →μ +Z +Zμ of a muon scattering off nuclei by looking for an excess of events with large missing muon beam energy in a detector due to the prompt bremsstrahlung Zμ decay Zμ→ν ν into a couple of neutrinos. We describe the experimental technique and the preliminary study of the feasibility for the proposed search. We show that this specific signal allows for a search for the Zμ with a sensitivity in the coupling constant αμ≳1 0-11 , which is 3 orders of magnitude higher than the value required to explain the discrepancy. We point out that the availability of high-energy and -intensity muon beams at CERN SPS provides a unique opportunity to either discover or rule out the Zμ in the proposed search in the near future. The experiment is based on the missing-energy approach developed for the searches for invisible decays of dark photons and (pseudo)scalar mesons at CERN and is complementary to these experiments.
- Publication:
-
Physical Review D
- Pub Date:
- May 2015
- DOI:
- 10.1103/PhysRevD.91.095015
- arXiv:
- arXiv:1412.1400
- Bibcode:
- 2015PhRvD..91i5015G
- Keywords:
-
- 14.80.-j;
- 12.60.-i;
- 13.20.Cz;
- 13.35.Hb;
- Other particles;
- Models beyond the standard model;
- Decays of pi mesons;
- Decays of heavy neutrinos;
- High Energy Physics - Phenomenology;
- High Energy Physics - Experiment;
- Physics - Instrumentation and Detectors
- E-Print:
- 13 pages, 9 figures. Version to appear in PRD, refs. and discussions added, title modified in journal