  We report the first measurements of deep inelastic scattering spin-dependent
azimuthal asymmetries in back-to-back dihadron electroproduction, where two
hadrons are produced in opposite hemispheres along the z-axis in the
center-of-mass frame, with the first hadron produced in the
current-fragmentation region and the second in the target-fragmentation region.
The data were taken with longitudinally polarized electron beams of 10.2 and
10.6 GeV incident on an unpolarized liquid-hydrogen target using the CLAS12
spectrometer at Jefferson Lab. Observed non-zero $\sin\Delta\phi$ modulations
in $ep \rightarrow e'p\pi^+X$ events, where $\Delta\phi$ is the difference of
the azimuthal angles of the proton and pion in the virtual photon and target
nucleon center-of-mass frame, indicate that correlations between the spin and
transverse momenta of hadrons produced in the target- and current-fragmentation
regions may be significant. The measured beam-spin asymmetries provide a first
access in dihadron production to a previously unobserved leading-twist spin-
and transverse-momentum-dependent fracture function. The fracture functions
describe the hadronization of the target remnant after the hard scattering of a
virtual photon off a quark in the target particle and provide a new avenue for
studying nucleonic structure and hadronization.
