Navelet Jets Research Articles

The observation of jet azimuthal angular decorrelations at FCC-ep

Higher collision energies at future colliders may eventually lead to the falsification of standard fixed-order perturbation theory and linear evolutions due to nonlinear structure of QCD at small-[Formula: see text]. New physics research works that are strictly based on accurate jet measurements will undoubtedly have this observation known as Balitsky–Fadin–Kuraev–Lipatov (BFKL) effect via angular jet decorrelations taking into account the Mueller–Navelet jets. As one of the frontier colliders, FCC-ep, has a great observation potential on parton densities through asymmetrical collisions. We aim to test the observability of azimuthal angular jet decorrelations with the recent event generators (HERWIG, PYTHIA) at the generator and detector level for FCC-ep center of mass energies [Formula: see text][Formula: see text]TeV in proton–electron collisions. Jets are reconstructed by the anti-[Formula: see text] algorithm ([Formula: see text]), with [Formula: see text][Formula: see text]GeV and selected in the range of [Formula: see text]. Relevant pseudo-rapidity regions have been analyzed with the azimuthal-angle difference between Mueller–Navelet Jets ([Formula: see text]) in the pseudo-rapidity separation ([Formula: see text]) and the distributions of [Formula: see text] are presented in comparison as the result.

Inclusive dijet hadroproduction with a rapidity veto constraint

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.

BFKL azimuthal imprints in inclusive three-jet production at 7 and 13 TeV

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.

Mueller–Navelet jets at 13 TeV LHC: dependence on dynamic constraints in the central rapidity region

We study the production of Mueller-Navelet jets at 13 TeV LHC, within collinear factorization and including the BFKL resummation of energy logarithms in the next-to-leading approximation. We calculate several azimuthal correlations for different values of the rapidity separation $Y$ between the two jets and evaluate the effect of excluding those events where, for a given $Y$, one of the two jets is produced in the central region.

Erratum to: Mueller–Navelet jets in next-to-leading order BFKL: theory versus experiment

We study, within QCD collinear factorization and including BFKL resummation at the next-to-leading order, the production of Mueller-Navelet jets at LHC with center-of-mass energy of 7 TeV. The adopted jet vertices are calculated in the approximation of small aperture of the jet cone in the pseudorapidity-azimuthal angle plane. We consider several representations of the dijet cross section, differing only beyond the next-to-leading order, to calculate a few observables related with this process. We use various methods of optimization to fix the energy scales entering the perturbative calculation and compare thereafter our results with the experimental data from the CMS collaboration.

Mueller–Navelet jets at LHC: BFKL versus high-energy DGLAP

The production of forward jets separated by a large rapidity gap at LHC, the so-called Mueller–Navelet jets, is a fundamental testfield for perturbative QCD in the high-energy limit. Several analyses have already provided us with evidence about the compatibility of theoretical predictions, based on collinear factorization and BFKL resummation of energy logarithms in the next-to-leading approximation, with the CMS experimental data at 7 TeV of center-of-mass energy. However, the question if the same data can be described also by fixed-order perturbative approaches has not yet been fully answered. In this paper we provide numerical evidence that the mere use of partially asymmetric cuts in the transverse momenta of the detected jets allows for a clear separation between BFKL-resummed and fixed-order predictions in some observables related with the Mueller–Navelet jet production process.

Mueller--Navelet Jets at the LHC: Discriminating BFKL from DGLAP by Asymmetric Cuts

Mueller--Navelet Jets at the LHC: Discriminating BFKL from DGLAP by Asymmetric Cuts

Mueller–Navelet jets in next-to-leading order BFKL: theory versus experiment

We study, within QCD collinear factorization and including BFKL resummation at the next-to-leading order, the production of Mueller–Navelet jets at LHC with center-of-mass energy of 7 TeV. The adopted jet vertices are calculated in the approximation of a small aperture of the jet cone in the pseudorapidity-azimuthal angle plane. We consider several representations of the dijet cross section, differing only beyond the next-to-leading order, to calculate a few observables related with this process. We use various methods of optimization to fix the energy scales entering the perturbative calculation and compare our results with the experimental data from the CMS collaboration.

Violation of energy–momentum conservation in Mueller–Navelet jets production

We study effects related to violation of energy–momentum conservation inherent to the BFKL approach, in the particular case of Mueller–Navelet jets production. We argue, based on the comparison of the lowest order non-trivial corrections O(αs3) to the cross section with predictions of an exact calculation, that the inclusion of next-to-leading order BFKL corrections to the jet production vertex significantly reduces the importance of these effects.

Mueller--Navelet Jets at the CMS

Mueller--Navelet Jets at the CMS

Mueller–Navelet small-cone jets at LHC in next-to-leading BFKL

We consider within QCD collinear factorization the process p+p→jet+jet+X, where two forward high-pT jets are produced with a large separation in rapidity Δy (Mueller–Navelet jets). In this case the (calculable) hard part of the reaction receives large higher-order corrections ∼αsn(Δy)n, which can be accounted for in the BFKL approach with next-to-leading logarithmic accuracy, including contributions ∼αsn(Δy)n−1. We calculate several observables related with this process, using the next-to-leading order jet vertices, recently calculated in the approximation of small aperture of the jet cone in the pseudorapidity–azimuthal angle plane.

Scale choice and collinear contributions to Mueller–Navelet jets at LHC energies

We investigate the stability under variation of the renormalization, factorization and energy scales entering the calculation of the cross section, at next-to-leading order in the BFKL formalism, for the production of Mueller–Navelet jets at the Large Hadron Collider, following the experimental cuts on the tagged jets. To find optimal values for the scales involved in this observable it is possible to look for regions of minimal sensitivity to their variation. We show that the scales found with this logic are more natural, in the sense of being more similar to the squared transverse momenta of the tagged jets, when the BFKL kernel is improved with a resummation of collinear contributions than when the treatment is at a purely next-to-leading order. We also discuss the good perturbative convergence of the ratios of azimuthal angle correlations, which are quite insensitive to collinear resummations and well described by the original BFKL framework.

Confronting Mueller-Navelet jets in NLL BFKL with LHC experiments at 7 TeV

AbstractMore than 25 years ago, Mueller Navelet jets were proposed as a decisive test of BFKL dynamics at hadron colliders. We here study this process at NLL BFKL accuracy, taking into account NLL corrections to the Green’s function and to the jet vertices. We present detailed predictions for various observables that can be measured at LHC in ongoing experiments like ATLAS or CMS at$ \sqrt{s}=7 $TeV: the cross-section, the azimuthal correlations and the angular distribution of these jets. For this purpose, we apply realistic kinematical cuts and binning, and study the dependence of our results with respect to several parameters. We then compare our results with those that can be obtained in a fixed order NLO treatment, and propose specific observables which could actually be used as a probe of BFKL dynamics.

Mueller Navelet jets at LHC — complete next-to-leading BFKL calculation

We calculate cross section and azimuthal decorrellation of Mueller Navelet jets at the LHC in the complete next-lo-leading order BFKL framework, i.e. including next-to-leading corrections to the Green’s function as well as next-to-leading corrections to the Mueller Navelet vertices. The obtained results for standard observables proposed for studies of Mueller Navelet jets show that both sources of corrections are of equal, big importance for final magnitude and final behavior of observables. The astonishing conclusion of our analysis is that the observables obtained within the complete next-lo-leading order BFKL framework of the present paper are quite similar to the same observables obtained within next-to-leading DGLAP type treatment. This fact sheds doubts on general belief that the studies of Mueller Navelet jets at the LHC will lead to clear discrimination between the BFKL and the DGLAP dynamics.

Geometric scaling in Mueller–Navelet jets

We argue that the production of Mueller–Navelet jets at the LHC represents a convenient environment to study gluon saturation and high-energy scattering in the presence of unitarity corrections. We show that, in a suitable range of transverse momenta for the produced jets, the cross-section for the partonic subprocess should exhibit geometric scaling. We point out that, in the presence of a running coupling, the cross-section for producing hard jets cannot be fully computed in perturbation theory, not even after taking into account the saturation effects: the non-perturbative physics affects the overall normalization of the cross-section, but not also its geometric scaling behavior.

The azimuthal decorrelation of jets widely separated in rapidity as a test of the BFKL kernel

We study the decorrelation in azimuthal angle of Mueller–Navelet jets at hadron colliders within the BFKL formalism. We introduce NLO terms in the evolution kernel and present a collinearly-improved version of it for all conformal spins. We show how this further resummation has good convergence properties and is closer to the Tevatron data than a simple LO treatment. However, we are still far from a good fit. We offer estimates of these decorrelations for larger rapidity differences which should favor the onset of BFKL effects and encourage experimental studies of this observable at the LHC.

Small-x QCD effects in forward-jet and Mueller–Navelet jet production

We investigate small-x QCD effects in forward-jet production in deep inelastic scattering in the kinematic regime where the virtuality of the photon and the transverse momentum of the jet are two hard scales of about the same magnitude. We show that the data from HERA published by the H1 and ZEUS Collaborations are well described by leading-logarithmic BFKL predictions. Parametrizations containing saturation effects expected to be relevant at higher energies also compare well to the present data. We extend our analysis to Mueller–Navelet jets at the LHC and discuss to what extent this observable could test these small-x effects and help distinguishing between the different descriptions.

A QCD dipole formalism for forward-gluon production

We derive inclusive and diffractive forward-gluon production in the scattering of a q q ¯ dipole off an arbitrary target in the high-energy eikonal approximation, suitable to study the saturation regime. We show how the inclusive cross-section is related to the total cross-section for the scattering of a colorless pair of gluons on the target: the gluon-production cross-section can be expressed as a convolution between this gg dipole total cross-section and a dipole distribution. We then consider as an application the forward-jet production from an incident hadron and describe forward-jet production at HERA and Mueller–Navelet jets at Tevatron or LHC. We show how these measurements are related to the q q ¯ – gg or gg– gg dipole–dipole cross-sections and why they are therefore well-suited for studying high-energy scattering in QCD.

Saturation and forward jets at HERA

We analyse forward-jet production at HERA in the framework of the Golec-Biernat and Wüsthoff saturation models. We obtain a good description of the forward-jet cross-sections measured by the H1 and ZEUS Collaborations in the two-hard-scale region (kT∼Q≫ΛQCD) with two different parametrizations with either significant or weak saturation effects. The weak saturation parametrization gives a scale compatible with the one found for the proton structure function F2. We argue that Mueller–Navelet jets at the Tevatron and the LHC could help distinguishing between both options.

The NLO jet vertex for Mueller-Navelet and forward jets: the gluon part

In this paper we complete our calculation of the NLO jet vertex which is part of the cross section formulae for the production of Mueller Navelet jets at hadron hadron colliders and of forward jets in deep inelastic electron proton scattering.