A New Parametrization of Polarized Parton Distribution Functions

Recently there has been renewed interest on polarized parton distributions in the nucleon, largely stimulated by the development of the next-to leading order(NLO) QCD calculations of polarized parton distribution functions and acquisition of high-precision polarized data on various targets. In this work, requiring reasonable physical conditions, (1)the positivity condition and (2) the counting rule for the helicity dependent parton distribution functions, we propose a new parametrization of the polarized parton distribution function which is more reliable and fits better to the data than other parametrizations proposed so far. Based on the positivity condition and counting rule for helicity dependent distributions, we propose the following functional form of the polarized parton distributions at an initial scale Q0, ∆fi(x,Q 2 0) = Ai x αi (1 + γi x i) fi(x,Q 2 0) , (1)