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F. Schwennsen

Publications and source records attributed to F. Schwennsen.

17 recordsLinked to original sources
arXiv2011

The first complete NLL BFKL study of Mueller Navelet jets at LHC

We report on the first next-to-leading BFKL study of the cross section and azimuthal decorrellation of Mueller Navelet jets. This includes 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 and big importance for final magnitude and final behavior of observables, in particular for the LHC kinematics investigated here in detail. The astonishing conclusion of our analysis is that the observables obtained within the complete next-lo-leading order BFKL framework of the present contribution are quite similar to the same observables obtained within next-to-leading logarithm DGLAP type treatment. The only noticeable difference is the ratio the azimuthal angular moments < cos 2 phi> / < cos phi > which still differs in both treatments.

hep-ph↗
arXiv2010

Mueller Navelet jets at LHC - complete NLL 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 logarithm 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.

hep-ph↗
arXiv2010

First complete NLL BFKL calculation of Mueller Navelet jets at LHC

For the first time, a next-to-leading BFKL study of the cross section and azimuthal decorrellation of Mueller Navelet jets is performed, 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 and big importance for final magnitude and final behavior of observables, in particular for the LHC kinematics investigated here in detail. 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 logarithm DGLAP type treatment. The only noticeable difference is the ratio the azimuthal angular moments < cos 2 phi >/ < cos phi > which still differs in both treatments.

hep-ph↗
arXiv2010

A complete NLL BFKL calculation of Mueller Navelet jets at LHC

For the first time, a next-to-leading BFKL study of the cross section and azimuthal decorrellation of Mueller Navelet jets is performed, 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 and big importance for final magnitude and final behavior of observables, in particular for the LHC kinematics investigated here in detail. 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 logarithm 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.

hep-ph↗
arXiv2009

Pomeron Odderon interference in production of two pi+ pi- pairs at LHC and ILC

We propose to look for the Odderon through the production of two pion pairs in photon collisions at high energies. We calculate the corresponding matrix elements in kT-factorization and discuss the possibility to reveal the existence of the perturbative Odderon by charge asymmetries, relying on models for the generalized distribution amplitudes of pi+ pi-. The application of this strategy to ultraperipheral collisions at the LHC suffers from the difficulty to trigger on interesting events and is plagued with severe background problems in p-p mode. Electron - positron colliders like ILC seem to better suit this physics.

hep-ph↗
arXiv2009

Pomeron Odderon interference in production of pi+ pi- pairs at LHC

We discuss the production of two pion pairs in photon collisions at high energies as it can take place in ultraperipheral collisions at hadron colliders such as the LHC. We calculate the according matrix elements in kT factorization and discuss the possibility to reveal the existence of the perturbative Odderon by charge asymmetries.

hep-ph↗
arXiv2008

Hard Pomeron-Odderon interference effects in the production of pi^+pi^- pairs in high energy gamma-gamma collisions at the LHC

We estimate the production of two meson pairs in high energy photon photon collisions produced in ultraperipheral collisions at LHC. We show that the study of charge asymmetries may reveal the existence of the perturbative Odderon and discuss the concrete event rates expected at the LHC. Sizable rates and asymmetries are expected in the case of proton-proton collisions and medium values of gamma-gamma energies \sqrt{s_{γγ}} \approx 20GeV. Proton-proton collisions will benefit from a high rate due to a large effective gamma-gamma luminosity and ion-ion collisions with a somewhat lower rate from the possibility to trigger on ultraperipheral collisions and a reduced background from strong interactions.

hep-ph↗
arXiv2008

Z and W production associated with quark-antiquark pair in k_T-factorization at the LHC

We calculate and analyze Z and W production in association with quark-antiquark pair in k_T-factorization. Numerical calculations are performed using the Monte Carlo generator CASCADE for proton proton collisions at LHC energy. We compare total and differential cross sections calculated in k_T-factorization approach with total differential cross sections obtained in LO and NLO calculations in collinear factorization approach. We provide strong evidence that some of the effects of the NLO and even higher order collinear calculation are already included in the LO k_T-factorization calculation.

hep-ph↗
arXiv2008

Resummation of projectile-target multiple scatterings and parton saturation

In the framework of a toy model which possesses the main features of QCD in the high energy limit, we conduct a numerical study of scattering amplitudes constructed from parton splittings and projectile-target multiple interactions, in a way that unitarizes the amplitudes without however explicit saturation in the wavefunction of the incoming states. This calculation is performed in two different ways. One of these formulations, the closest to field theory, involves the numerical resummation of a factorially divergent series, for which we develop appropriate numerical tools. We accurately compare the properties of the resulting amplitudes with what would be expected if saturation were explicitly included in the evolution of the states. We observe that the amplitudes have similar properties in a small but finite range of rapidity in the beginning of the evolution, as expected. Some of the features of reaction-diffusion processes are already present in that range, even when saturation is left out of the model.

hep-ph↗
arXiv2007

NLO jet production in k_T factorization

We discuss the inclusive production of jets in the central region of rapidity in the context of k_T-factorization at next-to-leading order (NLO). Calculations are performed in the Regge limit making use of the NLO BFKL results. We introduce a jet cone definition and carry out a proper phase--space separation into multi-Regge and quasi-multi-Regge kinematic regions. We discuss two situations: scattering of highly virtual photons, which requires a symmetric energy scale to separate impact factors from the gluon Green's function, and hadron-hadron collisions, where a non-symmetric scale choice is needed.

hep-ph↗
arXiv2006

NLO inclusive jet production in $k_T$--factorization

The inclusive production of jets in the central region of rapidity is studied in $k_T$-factorization at next-to-leading order (NLO) in QCD perturbation theory. Calculations are performed in the Regge limit making use of the NLO BFKL results. A jet cone definition is introduced and a proper phase--space separation into multi-Regge and quasi-multi-Regge kinematic regions is carried out. Two situations are discussed: scattering of highly virtual photons, which requires a symmetric energy scale to separate the impact factors from the gluon Green's function, and hadron-hadron collisions, where a non--symmetric scale choice is needed.

hep-ph↗
arXiv2006

NLO jet production at central rapidities in $k_T$ factorization

In this contribution we discuss the inclusive production of jets in central regions of rapidity in the context of $k_T$-factorization at next-to-leading order (NLO). We work in the Regge limit of QCD and use the NLO BFKL results. A jet cone definition is proposed together with a phase-space separation into multi-Regge and quasi-multi-Regge kinematics. We discuss scattering of highly virtual photons, with a symmetric energy scale to separate the impact factors from the gluon Green's function, and hadron-hadron collisions, with a non-symmetric scale choice.

hep-ph↗
arXiv2006

Azimuthal angle decorrelation of Mueller-Navelet jets at NLO

In this contribution we study azimuthal angle decorrelation in inclusive dijet cross sections taking into account the next-to-leading (NLO) corrections to the BFKL kernel while keeping the jet vertices at leading order. We show how the angular decorrelation for jets with a wide relative separation in rapidity largely decreases when the NLO corrections are included.

hep-ph↗
arXiv2005

Off-Shell Scattering Amplitudes for WW Scattering and the Role of the Photon Pole

We derive analytic expressions for high energy $2 \to 2$ off-shell scattering amplitudes of weak vector bosons. They are obtained from six fermion final states in processes of the type $e^+ e^- \to \barν_e + (WW) + ν_e \to \barν_e + (lν)(lν) + ν_e$. As an application we reconsider the unitarity bounds on the Higgs mass. Particular attention is given to the role of the photon exchange which has not been considered in earlier investigations; we find that the photon weakens the bound of the Higgs mass.

hep-ph↗