  An extended superscaling analysis of quasielastic electron scattering data is
proposed by parametrizing the scaling function as the sum of a symmetric
function corresponding to the emission of a single particle plus a contribution
from the phase space of two-particle emission. The phase space of two-particle
emission (2p2h) is multiplied by a q-dependent parameter that has been fitted
to describe the tail behavior of the scaling function. This approach allows for
an alternative description of the quasielastic electron scattering data,
incorporating the contributions from both single-particle and two-particle
emission processes induced by the one-body current and explaining the asymmetry
of the scaling function. In a factorized schematic model based on the
independent-pair approximation, the 2p2h parameter is related to the
high-momentum distribution of the pair averaged over 2p-2h excitations.
However, in the phenomenological fitting approach undertaken here, this
coefficient includes other contributions such as interference with two-body
currents and effects of the final-state interactions. We present predictions
for the inclusive two-nucleon emission cross section induced by electrons and
neutrinos.
