Motivated by the recent work of Brzemiński, Motyka, Sadzikowski and Stebel in [1], where forward Drell-Yan production is studied in proton-proton collisions at the LHC, we improve their calculation by introducing an unintegrated gluon density obtained in [2] from a fit to combined HERA data at small values of Bjorken x. This gluon density was calculated within the BFKL formalism at next-to-leading order with collinear corrections. We show that it generates a good description of the forward Drell-Yan cross section dependence on the invariant mass of the lepton pair both for LHCb and ATLAS data.

We propose the study of new observables in LHC inclusive events with three tagged jets, one in the forward direction, one in the backward direction and both well-separated in rapidity from the each other (Mueller-Navelet jets), together with a third jet tagged in central regions of rapidity.Since non-tagged associated mini-jet multiplicity is allowed, we argue that projecting the cross sections on azimuthal-angle components can provide several distinct tests of the BFKL dynamics. Realistic LHC kinematical cuts are introduced.

We study ratios of azimuthal-angle distributions in Mueller-Navelet jets after imposing a rapidity veto constraint: the minijet radiation activity is restricted to only allow final-state partons separated at least a distance in rapidity b. It is well-known that the asymptotic growth with the rapidity separation of the two tagged jets of the NLLA BFKL Green's function requires a value of b O(2) in order to avoid unphysical cross sections. We further investigate this point from a phenomenological point of view and work out those values of b which best fit angular distributions measured at the LHC in a realistic set-up where impact factors and parton distribution effects are also taken into account.

Recently, a new family of observables consisting of azimuthal-angle generalised ratios was proposed in a kinematical setup that resembles the usual Mueller-Navelet jets but with an additional tagged jet in the central region of rapidity. Non-tagged minijet activity between the three jets can affect significantly the azimuthal angle orientation of the jets and is accounted for by the introduction of two BFKL gluon Green functions. Here, we calculate the, presumably, most relevant higher order corrections to the observables by now convoluting the three leading-order jet vertices with two gluon Green functions at next-to-leading logarithmic approximation. The corrections appear to be mostly moderate giving us confidence that the recently proposed observables are actually an excellent way to probe the BFKL dynamics at the LHC. Furthermore, we allow for the jets to take values in different rapidity bins in various configurations such that a comparison between our predictions and the experimental data is a straightforward task. * 'La Caixa'-Severo Ochoa Scholar.

Recently, new observables in LHC inclusive events with three tagged jets were proposed. Here, we extend that proposal to events with four tagged jets. The events are characterized by one jet in the forward direction, one in the backward direction with a large rapidity distance Y from the first one and two more jets tagged in more central regions of the detector. In our setup, non-tagged associated mini-jet multiplicity is present and needs to be accounted for by the inclusion of BFKL gluon Green functions. The projection of the cross section on azimuthal-angle components opens up the opportunity for defining new ratios of correlation functions of the azimuthal-angle differences among the tagged jets that can be used as probes of the BFKL dynamics.