 | Distributions of the undetected mass M2X for the signal (top) and background (bottom) reference samples, which are selected as described in Sect.~??? in the extended kinematic range Q2>1(GeV/c)2, y>0.05 and |tTOF|>0.08(GeV/c)2. Here, the quantities y and tTOF denote the fractional energy loss of the muon and the squared four-momentum transfer to the recoil proton as measured by the target TOF system, respectively. Simulated data are also shown (see text). Note that events with the topology of exclusive π0 production were removed from the LEPTO sample. Error bars denote statistical uncertainties. |