Searcharxiv⌕ Search

arXiv subjects

Dieter Zeppenfeld

Publications and source records attributed to Dieter Zeppenfeld.

At least 55 records · Page 3Linked to original sources
arXiv2006

Next-to-leading order QCD corrections to Z boson pair production via vector-boson fusion

Vector-boson fusion processes are an important tool for the study of electroweak symmetry breaking at hadron colliders, since they allow to distinguish a light Higgs boson scenario from strong weak boson scattering. We here consider the channels WW->ZZ and ZZ->ZZ as part of electroweak Z boson pair production in association with two tagging jets. We present the calculation of the NLO QCD corrections to the cross sections for p p -> e+ e- mu+ mu- + 2 jets and p p -> e+ e- nu_mu nubar_mu + 2 jets via vector-boson fusion at order alpha_s alpha^6, which is performed in the form a NLO parton-level Monte Carlo program. The corrections to the integrated cross sections are found to be modest, while the shapes of some kinematical distributions change appreciably at NLO. Residual scale uncertainties typically are at the few percent level.

hep-ph↗
arXiv2006

Next-to-leading order QCD corrections to W+W- production via vector-boson fusion

Vector-boson fusion processes constitute an important class of reactions at hadron colliders, both for signals and backgrounds of new physics in the electroweak interactions. We consider what is commonly referred to as W+W- production via vector-boson fusion (with subsequent leptonic decay of the Ws), or, more precisely, e+ nu_e mu- nubar_mu + 2 jets production in proton-proton scattering, with all resonant and non-resonant Feynman diagrams and spin correlations of the final-state leptons included, in the phase-space regions which are dominated by t-channel electroweak-boson exchange. We compute the next-to-leading order QCD corrections to this process, at order alpha^6 alpha_s. The QCD corrections are modest, changing total cross sections by less than 10%. Remaining scale uncertainties are below 2%. A fully-flexible next-to-leading order partonic Monte Carlo program allows to demonstrate these features for cross sections within typical vector-boson-fusion acceptance cuts. Modest corrections are also found for distributions.

hep-ph↗
arXiv2004

QCD Corrections to Jet Correlations in Weak Boson Fusion

Higgs boson production via weak boson fusion is sensitive to the tensor structure of the HVV (V=W,Z) couplings, which distinguishes loop induced vertices from SM expectations. At the CERN Large Hadron Collider this information shows up most clearly in the azimuthal angle correlations of the two forward and backward quark jets which are typical for weak boson fusion. We calculate the next-to-leading order QCD corrections to this process, in the presence of anomalous HVV couplings. Gluon emission does not significantly change the azimuthal jet correlations.

hep-ph↗
arXiv2004

QCD corrections to electroweak l nu_l jj and l^+ l^- jj production

The production of W or Z bosons in association with two jets is an important background to the Higgs boson search in vector-boson fusion at the LHC. The purely electroweak component of this background is dominated by vector-boson fusion, which exhibits kinematic distributions very similar to the Higgs boson signal. We consider the next-to-leading order QCD corrections to the electroweak production of l nu_l jj and l^+ l^- jj events at the LHC, within typical vector-boson fusion cuts. We show that the QCD corrections are modest, increasing the total cross sections by about 10%. Remaining scale uncertainties are below 2%. A fully-flexible next-to-leading order partonic Monte Carlo program allows to demonstrate these features for cross sections within typical vector-boson-fusion acceptance cuts. Modest corrections are also found for distributions.

hep-ph↗
arXiv2002

Higgs couplings at the LHC

The observation of a SM-like Higgs boson in multiple channels at the LHC allows the extraction of Higgs couplings to gauge bosons and fermions. The precision achievable at the LHC, for an integrated luminosity of 200 fb^{-1}, is reviewed and updated.

hep-ph↗
arXiv2001

Higgs plus two jet production at LHC and VLHC

We consider gluon-fusion and weak-boson fusion production of Higgs plus two jets in pp collisions at sqrt{s}=14 TeV (LHC) and sqrt{s}=50, 100, 200 TeV (VLHC). We give cross sections for Higgs masses between 115 GeV and 200 GeV, and discuss the experimental cuts that should be applied in order to enhance the weak-boson fusion contribution with respect to the gluon-fusion background.

hep-ph↗
arXiv2000

Run II Jet Physics: Proceedings of the Run II QCD and Weak Boson Physics Workshop

The Run II jet physics group includes the Jet Algorithms, Jet Shape/Energy Flow, and Jet Measurements/Correlations subgroups. The main goal of the jet algorithm subgroup was to explore and define standard Run II jet finding procedures for CDF and DO. The focus of the jet shape/energy flow group was the study of jets as objects and the energy flows around these objects. The jet measurements/correlations subgroup discussed measurements at different beam energies; strong coupling constant measurements; and LO, NLO, NNLO, and threshold jet calculations. As a practical matter the algorithm and shape/energy flow groups merged to concentrate on the development of Run II jet algorithms that are both free of theoretical and experimental difficulties and able to reproduce Run I measurements. Starting from a review of the experience gained during Run I, the group considered a variety of cone algorithms and KT algorithms. The current understanding of both types of algorithms, including calibration issues, are discussed in this report along with some preliminary experimental results. The jet algorithms group recommends that CDF and DO employ the same version of both a cone algorithm and a KT algorithm during Run II. Proposed versions of each type of algorithm are discussed. The group also recommends the use of full 4-vector kinematic variables whenever possible. The recommended algorithms attempt to minimize the impact of seeds in the case of the cone algorithm and preclustering in the case of the KT algorithm. Issues regarding precluster definitions and merge/split criteria require further study.

hep-ex↗
arXiv1999

b-quark decay in the collinear approximation

The semileptonic decay of a b-quark, b--> c l nu, is considered in the relativistic limit where the decay products are approximately collinear. Analytic results for the double differential lepton energy distributions are given for finite charm-quark mass. Their use for the fast simulation of isolated lepton backgrounds from heavy quark decays is discussed.

hep-ph↗
arXiv1999

Probing the MSSM Higgs Sector via Weak Boson Fusion at the LHC

In the MSSM weak boson fusion produces the two CP even Higgs bosons with a combined strength equivalent to the production of the Standard Model Higgs boson. The tau tau decay mode --- supplemented by gamma gamma --- provides a highly significant signal for at least one of the CP even Higgs bosons at the LHC with reasonable luminosity. The accessible parameter space covers the entire physical range which will be left unexplored by LEP2.

hep-ph↗
arXiv1998

New Interactions in Neutral Current Processes

Measurements of neutral current processes off the $Z$-peak are sensitive probes of new interactions, which may be induced by the exchange of new particles such as leptoquarks or extra $Z$'s. This talk reviews the phenomenology of extra interactions in four-fermion processes and updates a global fit to contact terms in the neutral current sector.

hep-ph↗
arXiv1997

Jet Production in DIS at NLO

Dijet production in DIS is an important laboratory for testing our understanding of perturbative QCD. Flexible NLO Monte Carlo programs allow to investigate general jet definition schemes. For forward jet production at $p_{Tj} \approx Q$ and $x_{jet} >> x$ the NLO predictions fall well below HERA data, thus providing evidence for BFKL dynamics.

hep-ph↗
arXiv1997

Contact Interactions and high $Q^2$ Events at HERA

Effective $eeqq$ contact interactions can enhance event rates in $e^+p$ scattering at HERA at high $Q^2$. Present constraints from atomic parity violation measurements and from Drell Yan events at the Tevatron are discussed.

hep-ph↗
arXiv1996

Jet Production in Deep Inelastic Scattering at Next-to-Leading Order

NLO corrections to jet cross sections in DIS at HERA are studied, with particular emphasis on the two jet final state. High jet transverse momenta are a good criterion for the applicability of fixed order perturbation theory. A ``natural'' scale choice is the average $k_T^B$ of the jets in the Breit frame, which suggest analyzing the data in different $ $ intervalls.

hep-ph↗
arXiv1996

Fixed-Order QCD Backgrounds to BFKL Dynamics in Forward Jet Production

The production of forward jets of transverse momentum $p_T(j)\approx Q$ and large momentum fraction $x_{jet}\gg x$ probes the onset of BFKL dynamics at HERA. A full ${\cal O}(α_s^2)$ calculation of the inclusive forward jet cross section is presented and compared to the expected BFKL cross section.

hep-ph↗
arXiv1996

Forward Jet Production at HERA in the Low $x$ Regime in Next-to-Leading Order

The production of forward jets of transverse momentum $p_T(j)\approx Q$ and large momentum fraction $x_{jet}\gg x$ probes the onset of BFKL dynamics at HERA. A full ${\cal O}(α_s^2)$ calculation of the inclusive forward jet cross section is presented and compared to the expected BFKL cross section. The kinematical region populated by these events and the scale dependence of the fixed order perturbative QCD cross sections are discussed.

hep-ph↗
arXiv1996

NLO Corrections to Jet Cross Sections in DIS

Next-to-leading order corrections to jet cross sections in deep inelastic scattering at HERA are studied. The predicted jet rates allow for a precise determination of $α_s(μ_R)$ at HERA over a wide range of $μ_R$. We argue, that the ``natural'' renormalization and factorization scale is set by the average $k_T^B$ of the jets in the Breit frame and suggest to divide the data in corresponding $ $ intervals. Some implications for the determination of the gluon density and the associated forward jet production in the low $x$ regime at HERA are briefly discussed.

hep-ph↗
arXiv1996

Dijet Production at HERA in Next-to-Leading Order

Two-jet cross sections in deep inelastic scattering at HERA are calculated in next-to-leading order. The QCD corrections are implemented in a new $ep\rightarrow n$ jets event generator, MEPJET, which allows to analyze arbitrary jet definition schemes and general cuts in terms of parton 4-momenta. First results are presented for the JADE, the cone and the $k_T$ schemes. For the $W$-scheme, disagreement with previous results and large radiative corrections and recombination scheme dependencies are traced to a common origin.

hep-ph↗