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Francesco Hautmann

Publications and source records attributed to Francesco Hautmann.

28 records · Page 2Linked to original sources
arXiv2018

Constraining PDFs from neutral current Drell-Yan measurements and effects of resummation in slepton pair production

The high statistics that will be collected during the LHC Run-II (and beyond) open the path to precision measurements at the TeV scale, where the PDFs will play a crucial role in BSM searches. In the di-lepton final state accurate measurements of the Forward-Backward Asymmetry (AFB) will be available, particularly in the invariant mass region around the Z peak. We show that this observable displays a statistical error which is competitive with that assigned to the existing PDF sets and which will rapidly become smaller than the latter as the integrated luminosity grows, thereby offering a means of constraining the (anti)quark PDFs over a sizeable $(x,Q^2)$ range. In the context of SUSY searches we consider the effects of employing threshold-improved PDFs in a consistent calculation at NLO+NLL of slepton pair production cross sections. The calculations featuring a consistent resummation procedure both at PDF and partonic matrix element level are accompanied by PDF and scale uncertainties, and they provide a reliable and updated theoretical estimation for experimental data analyses at the LHC Run-II.

hep-ph↗
arXiv2017

Real and virtual photons effects in di-lepton production at the LHC

We show the SM prediction of di-lepton production at the LHC where to the usual Drell-Yan production we add the contribution from Photon-Initiated processes. We discuss the effects of the inclusion of photon interactions in the high invariant mass region (TeV region) and their consequences on BSM heavy Z'-boson searches.

hep-ph↗
arXiv2017

The effect of real and virtual photons in the di-lepton channel at the LHC

We present a study of di-lepton production at the CERN Large Hadron Collider with a particular focus on the contribution resulting from both real and virtual photons in the initial state. We discuss the region of phase space in which the invariant mass of the lepton pair is of the order of several TeV, where searches for new physics phenomena yielding a di-lepton signature are presently carried out. We study both the yield and associated uncertainties for all possible topologies in photon-induced di-lepton production and compare these with what is expected in the standard Drell-Yan channel, where quark-antiquark pairs are responsible for the production of lepton pairs. We analyse the impact of these QED contributions on the expected Standard Model background and on searches for new physics. In this latter case, we use the production of an extra heavy $Z^\prime$-boson predicted by the Sequential Standard Model (SSM) as a benchmark process.

hep-ph↗
arXiv2017

Photon-initiated production of a di-lepton final state at the LHC: cross section versus forward-backward asymmetry studies

We explore the effects of Photon Induced (PI) production of a dilepton final state in the Large Hadron Collider environment. Using QED Parton Distribution Function (PDF) sets we can treat the photons as real partons inside the protons and compare their yield directly to that of the Drell-Yan (DY) process. In particular, we concentrate on an error analysis of the two mechanisms. In order to do so, we use the NNPDF set, which comes with a set of replicas to estimate the systematic PDF error. On the one hand, we find that the PI contribution becomes dominant over DY above a dilepton invariant mass of 3 TeV. On the other hand, the PI predictions are affected by a large error coming from the QED PDFs, well above the one affecting the DY mode. We assess the impact of these uncertainties in the context of resonant and non-resonant searches for a neutral massive vector boson (Z') through the differential cross section and Forward-Backward Asymmetry (AFB) observables as a function of the dilepton invariant mass. While the former is subject to the aforementioned significant residual errors the latter shows the systematic error cancellation expected (recall that AFB is a ratio of cross sections) even in presence of PI contributions, so that the recently emphasized key role played by AFB as a valid tool for both Z' discovery and interpretation in both resonant and non-resonant mode is further consolidated.

hep-ph↗
arXiv2016

Impact of the Photon-Initiated process on Z'-boson searches in di-lepton final states at the LHC

We discuss the effect of the Photon Initiated (PI) process on the dilepton channel at the LHC. Adopting various QED PDF sets, we evaluate the contribution produced by two resolved photons which is not included in the Equivalent Photon Approximation (EPA). We compare the PI central value as predicted by the CTEQ, MRST and NNPDF collaborations. With the NNPDF2.3QED set of replicas we also estimate the PDF uncertainties on the PI central value. We show the effect of the inclusion of the PI contribution and its PDF uncertainties on neutral heavy Z'-boson searches. We explore the two scenarios of narrow and broad resonances, including in the analysis the reconstructed Forward-Backward Asymmetry observable, the latter being less affected by systematics effects.

hep-ph↗
arXiv2010

Higgs production via gluon fusion from kT-factorisation

Theoretical studies of Higgs production via gluon fusion are frequently carried out in the limit where the top quark mass is much larger than the Higgs mass, an approximation which reduces the top quark loop to an effective vertex. We present a numerical analysis of the error thus introduced by performing a Monte Carlo calculation for gg->h in kT-factorisation, using the parton shower generator CASCADE. We proceed to compare CASCADE to the collinear Monte Carlos PYTHIA, MC@NLO and POWHEG. We study the dependence of parton radiation on the resummation of high-energy corrections taken into account by kT-factorisation, and its influence on predictions for the Higgs pT spectrum.

hep-ph↗
arXiv1997

Probing the QCD pomeron in e+ e- collisions

The total cross section for scattering virtual photons at high energy is sensitive to pomeron physics. If the photons are sufficiently virtual, QCD perturbation theory applies, so that the reaction probes the short distance pomeron. We study this reaction for present and future e+/- e- colliders.

hep-ph↗