Suchergebnisse

We present the calculation of the finite part of the heavy quark impact factor at next-to-leading logarithmic accuracy in a form suitable for phenomenological studies such as the calculation of the cross-section for single bottom quark production at the LHC within the kT-factorization scheme. ; This work has been supported by the Research Executive Agency (REA) of the European Union under the Grant Agreement number PITN-GA-2010-264564 (LHCPhenoNet), by the Spanish Government and EU ERDF funds (grants FPA2007-60323, FPA2011-23778 and CSD2007-00042 Consolider Project CPAN) and by GV (PROMETEUII/2013/007). GC acknowledges support from Marie Curie Actions (PIEF-GA-2011-298582). MD acknowledges support from Juan de la Cierva programme (JCI-2011-11382). ; Peer reviewed

Using Monte Carlo integration techniques, we investigate running coupling effects compatible with the high energy bootstrap condition to all orders in the strong coupling in evolution equations valid at small values of Bjorken x in deep inelastic scattering. A model for the running of the coupling with analytic behavior in the infrared region and compatible with power corrections to jet observables is used. As a difference to the fixed coupling case, where the momentum transfer acts as an effective strong cutoff of the diffusion to infrared scales, in our running coupling study the dependence on the momentum transfer is much milder. ; G. C. thanks the Paul Scherrer Institut, the Department of Theoretical Physics at the Autonoma University of Madrid and the "Instituto de Fisica Teorica UAM/CSIC" for their hospitality. Research partially supported by the Research Executive Agency (REA) of the European Union under Grant Agreement No. PITN-GA-2010-264564 (LHCPhenoNet) and No. PIEF-GA-2011-298582, the Comunidad de Madrid through Proyecto HEPHACOS ESP-1473, and MICINN (FPA-2010-17747, FPA2011-23778, FPA2007-60323 and CSD2007-00042 CPAN) and Spanish MINECOs "Centro de Excelencia Severo Ochoa" Programme under Grant No. SEV-2012-0249. ; Peer reviewed

We evaluate differential cross sections for production of four jets in multi-Regge kinematics at a hadron collider. The main focus lies on the azimuthal angle dependences. As in previous studies, the ratios of correlation functions of products of cosines of azimuthal angle differences among the tagged jets offer us the cleanest quantities to compare with the experimental data. The calculations are based on the jet production from a single BFKL ladder with a convolution of three BFKL Green functions where we always have two forward/backward jets tagged in the final state. We also demand the tagging of two further jets in more central regions of the detectors with a relative separation in rapidity from each other, plus the inclusive production of an arbitrary number of mini-jets. We show that dependences on the transverse momenta and rapidity of the two central jets can be a distinct signal of the onset of BFKL dynamics ; G.C. acknowledges support from the MICINN, Spain, under contract FPA 2013-44773-P. A.S.V. acknowledges support from Spanish Government (MICINN (FPA2010-17747, FPA 201232828)) and, together with F.C. and F.G.C., to the Spanish MINECO Centro de Excelencia Severo Ochoa Programme (SEV-2012-0249)

We determine both real and virtual next-to-leading order corrections to the gluon-induced forward jet vertex from the high energy effective action proposed by Lipatov. For these calculations we employ the same regularization and subtraction formalism developed in our previous work on the quark-initiated vertex. We find agreement with previous results in the literature ; We acknowledge partial support from the European Commission under Contract No. LHCPhenoNet (PITNGA- 2010-264564), the Comunidad de Madrid through Proyecto HEPHACOS ESP-1473, MICINN (FPA2010- 17747), and Spanish MINECO's ''Centro de Excelencia Severo Ochoa'' Programme under Grant No. SEV-2012- 0249. M.H. acknowledges support from the German Academic Exchange Service (DAAD), the U.S. Department of Energy under Contract No. DE-AC02- 98CH10886 and a BNL ''Laboratory Directed Research and Development'' Grant (No. LDRD 12-034). G. C. thanks the partial support of the Research Executive Agency (REA) of the European Union under the Grant Agreement No. PIEF-GA-2011-298582 and MICINN (No. FPA2011-23778, No. FPA2007-60323, and No. CSD2007-00042 CPAN)

We present the derivation of the two-loop gluon Regge trajectory using Lipatov's high energy effective action and a direct evaluation of Feynman diagrams. Using a gauge invariant regularization of high energy divergences by deforming the light-cone vectors of the effective action, we determine the two-loop self-energy of the reggeized gluon, after computing the master integrals involved using the Mellin-Barnes representations technique. The self-energy is further matched to QCD through a recently proposed subtraction prescription. The Regge trajectory of the gluon is then defined through renormalization of the reggeized gluon propagator with respect to high energy divergences. Our result is in agreement with previous computations in the literature, providing a non-trivial test of the effective action and the proposed subtraction and renormalization framework. ; We thank J. Bartels, V. Fadin and L. Lipatov for constant support for many years. We acknowledge partial support by the Research Executive Agency (REA) of the European Union under the Grant Agreement number PITN-GA-2010-264564 (LHCPhenoNet), the Comunidad de Madrid through Proyecto HEPHACOS ESP-1473, by MICINN (FPA2010-17747), by the Spanish Government and EU ERDF Funds (grants FPA2007-60323, FPA2011-23778 and CSD2007-00042 Consolider Project CPAN) and by GV (PROMETEUII/2013/007). G.C. acknowledges support from Marie Curie Actions (PIEF-GA-2011-298582). M.H. acknowledges support from the U.S. Department of Energy under contract number DE-AC02-98CH10886 and a "BNL Laboratory Directed Research and Development" grant (LDRD 12-034). ; Peer reviewed

We determine both real and virtual next-to-leading order corrections to the gluon-induced forward jet vertex from the high energy effective action proposed by Lipatov. For these calculations we employ the same regularization and subtraction formalism developed in our previous work on the quark-initiated vertex. We find agreement with previous results in the literature. ; We acknowledge partial support from the European Commission under Contract No. LHCPhenoNet (PITN-GA- 2010-264564), the Comunidad de Madrid through Proyecto HEPHACOS ESP-1473, MICINN (FPA2010-17747), and Spanish MINECO's "Centro de Excelencia Severo Ochoa'' Programme under Grant No. SEV-2012-0249. M. H. acknowledges support from the German Academic Exchange Service (DAAD), the U.S. Department of Energy under Contract No. DE-AC02-98CH10886 and a BNL "Laboratory Directed Research and Development'' Grant (No. LDRD 12-034). G. C. thanks the partial support of the Research Executive Agency (REA) of the European Union under the Grant Agreement No. PIEF-GA-2011-298582 and MICINN (No. FPA2011-23778, No. FPA2007-60323,and No. CSD2007-00042 CPAN). ; Peer reviewed

In the context of evolution nequations and scattering amplitudes in the high energy limit of the N=4 super Yang–Mills theory we investigate in some detail the BFKL gluon Green function at next-to-leading order. In particular, we study its collinear be havi or in term so fan expansion in different angular components. We also perform a Monte Carlo simulation of the different final states contributing to such a Green function and construct the diffusion pattern in to in frared and ultraviolet modes and multiplicity distributions, making emphasis in separating the gluon contributions from those of scalars and gluinos. We find that the combined role of the non-gluonic degree sof freedom is to improve the collinear behavior and reduce the diffusion in to ultraviolet regions while not having any effect ont heaver age multiplicities or diffusion in to the in frared. In terms of growth with energy,the non-zero conformal spin components are mainly driven by the gluon terms in the BFKLkernel. Forze rocon formal spin (Pomeron) the effect the scalar and gluino sectors is to dramatically push the Green function towards higher values ; F.C. thanks the Instituto de Física Teórica UAM/CSIC for the warm hospitality.Weack now ledge partial support from the European Comission under contract LHC PhenoNet (PITN-GA-2010-264564), the Comunidad de Madrid through HEPHACOSS2009/ESP-1473, and MICINN (FPA2010-17747) and Spanish MINECOs Centro de Excelencia Severo Ochoa Programme under grant SEV-2012-0249.TheworkofF.C.was supported by EuropeanCommission, European Social Fund and Calabria Region,that disclaim many lia-bility for the use that can be done of the information provided in this Letter.G.C. thanks the support from the Research Executive Agency(REA)of the European Union under the Grant Agree ment number PIEF-GA-2011-298582 and by MICINN (FPA2011-23778,FPA2007-60323 and CSD2007-00042CPAN)

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. ; This work was supported by the Spanish Research Agency (Agencia Estatal de Investigación) through the grant IFT Centro de Excelencia Severo Ochoa SEV-2016-0597. GC and ASV acknowledge support from the Spanish Government grants FPA2015-65480-P, FPA2016-78022-P. DGG is supported with a fellowship of the international programme 'La Caixa-Severo Ochoa'. FGC acknowledges support from the Italian Foundation "Angelo della Riccia".

In the context of evolution equations and scattering amplitudes in the high energy limit of the N = 4 super Yang-Mills theory we investigate in some detail the BFKL gluon Green function at next-to-leading order. In particular, we study its collinear behavior in terms of an expansion in different angular components. We also perform a Monte Carlo simulation of the different final states contributing to such a Green function and construct the diffusion pattern into infrared and ultraviolet modes and multiplicity distributions, making emphasis in separating the gluon contributions from those of scalars and gluinos. We find that the combined role of the non-gluonic degrees of freedom is to improve the collinear behavior and reduce the diffusion into ultraviolet regions while not having any effect on the average multiplicities or diffusion into the infrared. In terms of growth with energy, the non-zero conformal spin components are mainly driven by the gluon terms in the BFKL kernel. For zero conformal spin (Pomeron) the effect of the scalar and gluino sectors is to dramatically push the Green function towards higher values. ; F.C. thanks the Instituto de Fisica Teorica UAM/CSIC for the warm hospitality. We acknowledge partial support from the European Comission under contract LHCPhenoNet (PITN-GA-2010-264564), the Comunidad de Madrid through HEPHACOS S2009/ESP-1473, and MICINN (FPA2010-17747) and Spanish MINECOs Centro de Excelencia Severo Ochoa Programme under grant SEV-2012-0249. The work of F.C. was supported by European Commission, European Social Fund and Calabria Region, that disclaim any liability for the use that can be done of the information provided in this Letter. G.C. thanks the support from the Research Executive Agency (REA) of the European Union under the Grant Agreement number PIEF-GA-2011-298582 and by MICINN (FPA2011-23778, FPA2007-60323 and C5D2007-00042 CPAN) ; Peer reviewed