Search for the dark photon in B-0 -> A ' A ', A ' -> e(+)e(-), mu(+)mu(-), and pi(+)pi(-) decays at Belle
Abstrakt
We present a search for the dark photon A in the B-0 -> A ' A ' decays, where A ' subsequently decays to e(+)e(-), mu (+)mu (-), and pi (+)pi (-). The search is performed by analyzing 772 x 10(6)BB events collected by the Belle detector at the KEKB e(+)e(-) energy-asymmetric collider at the Upsilon (4S) resonance.
No signal is found in the dark photon mass range 0.01 GeV/c(2) A ' A ' at the 90% confidence level. The products of branching fractions, BB0 -> A ' A 'xBA ' -> e+e-2 and BB0 -> A ' A 'xBA ' -> mu+mu-2, have limits of the order of 10(-8) depending on the A ' mass.
Furthermore, considering A ' decay rate to each pair of charged particles, the upper limits of BB0 -> A ' A ' are of the order of 10(-8)-10(-5). From the upper limits of BB0 -> A ' A ', we obtain the Higgs portal coupling for each assumed dark photon and dark Higgs mass.
The Higgs portal couplings are of the order of 10(-2)-10(-1) at mh ' similar or equal to mB0 +/- 40 MeV/c(2) and 10(-1)-1 at mh ' similar or equal to mB0 +/- 3 GeV/c(2).</graphic