Numerical solution of Q2 evolution equations in a brute-force method Original Research Article

We investigate the numerical solution of Q2 evolution equations for structure functions in the nucleon and in nuclei. (Dokshitzer-Gribov-Lipatov-) Altarelli-Parisi and Mueller-Qiu evolution equations are solved in a brute-force method. Spin-independent flavor-nonsinglet and singlet equations with next-to-leading-order αs corrections are studied. Dividing the variables x and Q2 into small steps, we simply solve the integrodifferential equations. Numerical results indicate that accuracy is better than 2% in the region 10−4 < x < 0.8 if more than two-hundred Q2 steps and more than one-thousand x steps are taken. The numerical solution is discussed in detail, and evolution results are compared with Q2 dependent data in CDHSW, SLAC, BCDMS, EMC, NMC, Fermilab-E665, ZEUS, and H1 experiments. We provide a FORTRAN program for Q2 evolution (and “devolution”) of nonsinglet-quark, singlet-quark, qi + q̄i, and gluon distributions (and corresponding structure functions) in the nucleon and in nuclei. This is a very useful program for studying spin-independent structure functions.