Search for A′→μ+μ− decays

Physical Review Letters. 2020. Vol. 124. No. 4. P. 1–12.

Aaij R., Beteta C. A., Borisyak M., Derkach D., Maevskiy A., Kazeev N., Ustyuzhanin A., Hushchyn M., Boldyrev A., Ratnikov F., Arzymatov K., Baranov A., Belavin V., Chekalina V., LHCb c.

Searches are performed for both prompt-like and long-lived dark photons, A′, produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for A′→μ+μ− decays using a data sample corresponding to an integrated luminosity of 5.5/fb collected with the LHCb detector. Neither search finds evidence for a signal, and 90 confidence-level exclusion limits are placed on the γ-A′ kinetic-mixing strength. The prompt-like A′ search explores the mass region from near the dimuon threshold up to 70 GeV, and places the most stringent constraints to date on dark photons with 214<m(A′)≲740 MeV and 10.6<m(A′)≲30 GeV. The search for long-lived A′→μ+μ− decays places world-leading constraints on low-mass dark photons with lifetimes O(1) ps.

Keywords: Experimental High Energy Physics and Elementary Particles Physics

Publication based on the results of: Machine learning to check and improve the quality of data collected at the Large Hadron Collider and other particle physics experiments (2020)