Leptonium

The LHC constraints on exotic stable massive charged particles seem to further shrink the allowed range for the hypercharge down to Y#95;#123;#92;ell#125;#92;approx 8-8.9, with the caveat that the relation between the leptonium mass and the mass of the constituent leptons in our calculations is plagued with a large theoretical uncertainty for large Y#95;#123;#92;ell#125;.