Gluon shadowing in the low x region probed by the LHC

Starting from an unintegrated gluon distribution which satisfies a 'unified' equation which embodies both BFKL and DGLAP behaviour, we compute the shadowing corrections to the integrated gluon in the small x domain that will be accessible at the LHC. The corrections are calculated via the Korchegov equation, which incorporates the leading ln(1/x) triple-Pomeron vertex, and are approximately resummed using a simple Padé technique. We find that the shadowing corrections to xg(x, Q 2) are rather small in the HERA domain, but lead to a factor of 2 suppression in the region x ∼ 10 −6 , Q 2 ∼ 4 GeV 2 accessible to experiments at the LHC. Experiments at HERA and the Tevatron have confirmed the rapid increase of the gluon distribution as x decreases, which is expected both in the pure DGLAP framework and in the BFKL-motivated approach. It is anticipated, however, that at sufficiently small x, this increase will be tamed by shadowing corrections. The first quantitative studies of gluon shadowing were made by Gribov, Levin and Ryskin [1] (GLR) and by Mueller and Qiu [2]. It was found that the shadowing contribution, f shad (Y, k 2), to the gluon distribution f (Y, k 2), unintegrated over the gluon transverse momentum k, is of the form ∂f shad (Y, k 2) ∂Y = −C α 2 S R 2