Investigations into the BFKL mechanism with a running QCD coupling

Bo Andersson, Gösta Gustafson, Hamid Kharraziha

Research output: Contribution to journalArticlepeer-review


We present approximations of varying degree of sophistication to the integral equations for the (gluon) structure functions of a hadron ("the partonic flux factor") in a model valid in the leading log approximation with a running coupling constant. The results are all of the BFKL type, i.e., a power in the Bjorken variable x(B)(-lambda) with the parameter lambda determined from the size alpha(0) of the "effective" running coupling <(alpha)over bar>=3 alpha(s)/pi =alpha(0)/ln(k(perpendicular to)(2)) and varying depending upon the treatment of the transverse momentum pole, we also consider the implications for the transverse momentum (k(perpendicular to)) fluctuations along the emission chains and we obtain an exponential falloff in the relevant kappa=ln(k(perpendicular to)(2)) variable, i.e., an inverse power (k(perpendicular to)(2))(-(2+lambda)) with the same parameter lambda. This is different from the BFKL result for a fixed coupling, where the distributions are Gaussian in the kappa variable with a width as in a Brownian motion determined by "the length" of the emission chains, i.e., In(1/x(B)). The results are verified by a realistic Monte Carlo simulation and we provide a simple physics motivation for the change.
Original languageEnglish
Pages (from-to)5543-5554
JournalPhysical Review D (Particles and Fields)
Issue number9
Publication statusPublished - 1998

Subject classification (UKÄ)

  • Subatomic Physics


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