Search for a light exotic particle in J/ψ radiative decays

Abstract

Using a data sample containing 1.06×108 ψ ′ events collected with the BESIII detector at the BEPCII electron-positron collider, we search for a light exotic particle X in the process ψ ′→π +π -J/ψ, J/ψ→γX, X→μ +μ -. This light particle X could be a Higgs-like boson A0, a spin-1 U boson, or a pseudoscalar sgoldstino particle. In this analysis, we find no evidence for any μ +μ - mass peak between the mass threshold and 3.0GeV/c2. We set 90%-confidence-level upper limits on the product-branching fractions for J/ψ→γA0, A0→μ +μ - which range from 4×10 -7 to 2.1×10 -5, depending on the mass of A0, for M(A0)<3.0GeV/c2. Only one event is seen in the mass region below 255MeV/c2, and this has a μ +μ - mass of 213.3MeV/c2 and the product-branching-fraction upper limit 5×10 -7. © 2012 American Physical Society.