High Pt hadron-hadron correlations

We propose the formulation of a dihadron fragmentation function in terms of
parton matrix elements. Under the collinear factorization approximation and
facilitated by the cut-vertex technique, the two hadron inclusive cross
section at leading order (LO) in e+ e- annihilation is shown to factorize
into a short distance parton cross section and the long distance dihadron
fragmentation function. We also derive the DGLAP evolution equation of this
function at leading log. The evolution equation for the non-singlet and
singlet quark fragmentation function and the gluon fragmentation function
are solved numerically with the initial condition taken from event
generators. Modifications to the dihadron fragmentation function from higher
twist corrections in DIS off nuclei are computed. Results are presented for
cases of physical interest.