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D. Zeppenfeld

Publications and source records attributed to D. Zeppenfeld.

At least 19 recordsLinked to original sources

Standard Model Physics at the HL-LHC and HE-LHC

The successful operation of the Large Hadron Collider (LHC) and the excellent performance of the ATLAS, CMS, LHCb and ALICE detectors in Run-1 and Run-2 with $pp$ collisions at center-of-mass energies of 7, 8 and 13 TeV as well as the giant leap in precision calculations and modeling of fundamental interactions at hadron colliders have allowed an extraordinary breadth of physics studies including precision measurements of a variety physics processes. The LHC results have so far confirmed the validity of the Standard Model of particle physics up to unprecedented energy scales and with great precision in the sectors of strong and electroweak interactions as well as flavour physics, for instance in top quark physics. The upgrade of the LHC to a High Luminosity phase (HL-LHC) at 14 TeV center-of-mass energy with 3 ab$^{-1}$ of integrated luminosity will probe the Standard Model with even greater precision and will extend the sensitivity to possible anomalies in the Standard Model, thanks to a ten-fold larger data set, upgraded detectors and expected improvements in the theoretical understanding. This document summarises the physics reach of the HL-LHC in the realm of strong and electroweak interactions and top quark physics, and provides a glimpse of the potential of a possible further upgrade of the LHC to a 27 TeV $pp$ collider, the High-Energy LHC (HE-LHC), assumed to accumulate an integrated luminosity of 15 ab$^{-1}$.

hep-ph

Physics Opportunities for Vector-Boson Scattering at a Future 100 TeV Hadron Collider

Vector-boson scattering (VBS) processes provide particularly promising means for probing the mechanism of electroweak symmetry breaking and to search for new physics in the weak sector. In the environment of a future proton-proton collider operating at a center-of-mass energy of 100 TeV, unprecedented opportunities arise for the investigation of this important class of reactions. We highlight the prominent features of VBS processes in this energy regime and discuss how the VBS signal can be isolated in the presence of a priori large QCD backgrounds. We find excellent opportunities for the analysis of VBS reactions in a kinematic range that is inaccessible to present colliders.

hep-ph

Physics at a 100 TeV pp collider: Standard Model processes

This report summarises the properties of Standard Model processes at the 100 TeV pp collider. We document the production rates and typical distributions for a number of benchmark Standard Model processes, and discuss new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.

hep-ph

Di-boson Production beyond NLO QCD and Anomalous Couplings

In these proceedings, we review results for several di-boson production processes beyond NLO QCD at high transverse momenta using the VBFNLO Monte-Carlo program together with the LOOPSIM method. Additionally, we show for the WZ production process how higher order QCD corrections can resemble anomalous coupling effects.

hep-ph

Parton-shower effects on Higgs boson production via vector-boson fusion in association with three jets

We present an implementation of Higgs boson production via vector-boson fusion in association with three jets at hadron colliders in the POWHEG-BOX, a framework for the matching of NLO-QCD calculations with parton-shower programs. Our work provides the means to precisely describe the properties of extra jet activity in vector-boson fusion reactions that are used for the suppression of QCD backgrounds by central jet veto techniques. For a representative setup at the CERN LHC we verify that uncertainties related to parton-shower effects are mild for distributions related to the third jet, in contrast to what has been observed in calculations based on vector-boson fusion induced Higgs production in association with two jets.

hep-ph

Release Note - VBFNLO 2.7.0

VBFNLO is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), double and triple vector boson (plus jet) production as well as QCD-induced single and double vector boson production plus two jets in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant. Furthermore, Higgs boson plus two jet production via gluon fusion at the one-loop level is included. This note briefly describes the main additional features and processes that have been added in the new release -- VBFNLO Version 2.7.0. At NLO QCD several new processes are available. These are $W^\pmγ$ and $HH$ production in VBF, the QCD-induced single and double vector boson plus two jets processes $W^\pm jj$, $W^\pm Zjj$, $W^\pmγjj$, same-sign $W^\pm W^\pm jj$, and the Higgs-strahlung process $W^\pm H$ (plus jet) production. Anomalous couplings are now available for all VBF, diboson and triboson (plus jet) processes including the new VBF $W^\pmγjj$ implementation, as well as in the Higgs-strahlung (plus jet) process. Semi-leptonic decay modes are supported for the following diboson, triboson and VBF processes: $VV$, $VVV$, $VVγ$ production and $VV$ production via VBF, where $V$ denotes a massive gauge boson, i.e. $W^\pm$ or $Z$. Additionally, the VBF-Higgs production process with decay into $WW$ or $ZZ$ supports semi-leptonic decays of the gauge bosons. All these semi-leptonic processes contain the possibility to include anomalous gauge boson couplings.

hep-ph

Release Note -- Vbfnlo-2.6.0

Vbfnlo is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), double and triple vector boson (plus jet) production in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant, as well as Higgs boson plus two jet production via gluon fusion at the one-loop level. This note briefly describes the main additional features and processes that have been added in the new release -- Vbfnlo Version 2.6.0. At NLO QCD diboson production (Wγ, WZ, ZZ, Zγand γγ), same-sign W pair production via vector boson fusion and the process Wγγj have been implemented (for which one-loop tensor integrals up to six-point functions are included). In addition, gluon induced diboson production can be studied separately at the leading order (one-loop) level. The diboson processes WW, WZ and Wγcan be run with anomalous gauge boson couplings, and anomalous couplings between a Higgs and a pair of gauge bosons is included in WW, ZZ, Zγand γγdiboson production. The code has also been extended to include anomalous gauge boson couplings for single vector boson production via VBF, and a spin-2 model has been implemented for diboson pair production via vector boson fusion.

hep-ph

Next-to-leading order QCD corrections to W+W+jj and W-W-jj production via weak-boson fusion

We present a next-to-leading order QCD calculation for e+ nu_e mu+ nu_mu jj and e- nubar_e mu- nubar_mu jj production via weak boson fusion at a hadron collider in the form of a fully-flexible parton-level Monte Carlo program, which allows for the calculation of experimentally accessible observables within realistic selection cuts. The QCD corrections to the integrated cross sections are found to be modest, while the shapes of some kinematical distributions change appreciably compared to leading order. The residual scale uncertainties of the next-to-leading order results are at the few-percent level.

hep-ph

Precision Multiboson Phenomenology

We present recent results in precision multiboson (+jet) phenomenology at the LHC. Results for diboson + jet, triboson, and also for WAA + jet will be discussed focusing on the impact of the perturbative corrections on the expected phenomenology.

hep-ph

VBFNLO: A parton level Monte Carlo for processes with electroweak bosons -- Manual for Version 3.0

VBFNLO is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), QCD-induced single and double vector boson production plus two jets, and double and triple vector boson production (plus jet) in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant, as well as Higgs boson plus two jet production via gluon fusion at the one-loop level. For the new version -- Version 3.0 -- several major enhancements have been included. An interface according to the Binoth Les Houches Accord (BLHA) has been added for all VBF and di/tri-boson processes including fully leptonic decays. For all dimension-8 operators affecting vector boson scattering (VBS) processes, a modified T-matrix unitarization procedure has been implemented. Several new production processes have been added, namely the VBS $Z\gamma jj$ and $\gamma \gamma jj$ processes at NLO, $\gamma \gamma jj $, $WWj$ and $ZZj$ production at NLO including the loop-induced gluon-fusion contributions and the gluon-fusion one-loop induced $\Phi jjj$ ($\Phi$ is a CP-even or CP-odd scalar boson) process at LO, retaining the full top-mass dependence. Finally, the code has been parallelized using OpenMPI.

hep-ph

Zγγproduction with leptonic decays and triple photon production at NLO QCD

We present a calculation of the O(alpha_s) QCD corrections to the production of a Z boson in association with two photons and to triple photon production at hadron colliders. All final-state photons are taken as real. For the Z boson, we consider the decays both into charged leptons and into neutrinos including all off-shell effects. Numerical results are obtained via a Monte Carlo program based on the structure of the VBFNLO program package. This allows us to implement general cuts and distributions of the final-state particles. We find that the NLO QCD corrections are sizable and significantly exceed the expectations from a scale variation of the leading-order result. In addition, differential distributions of important observables change considerably. The prediction of two-photon-associated Z production with Z decays into neutrinos from the charged-lepton rate works well, once we use an additional cut on the invariant mass of the charged-lepton pair.

hep-ph

Wγγproduction with leptonic decays at NLO QCD

The computation of the NLO-QCD corrections to the cross sections for W γγproduction in hadronic collisions is presented. We consider the case of real photons in the final state, but include full leptonic decays of the W. Numerical results for the LHC and the Tevatron are obtained through a parton level Monte Carlo based on the structure of the VBFNLO program, allowing an easy implementation of general cuts and distributions. We show the dependence on scale variations of the integrated cross sections and provide evidence of the fact that NLO QCD corrections strongly modify the LO predictions for observables at the LHC both in magnitude and in shape.

hep-ph

NLO QCD corrections to $W^\pm Zγ$ production with leptonic decays

We present a computation of the O(alpha_s) QCD corrections to W^\pm Z γproduction at the Large Hadron Collider. The photon is considered as real, and we include full leptonic decays for the W and Z bosons. Based on the structure of the VBFNLO program package, we obtain numerical results through a fully flexible Monte Carlo program, which allows to implement general cuts and distributions of the final-state particles. The NLO QCD corrections are sizable and strongly exceed the theory error obtained by a scale variation of the leading-order result. Also, the shapes of relevant observables are significantly altered.

hep-ph

NLO QCD corrections to WZ+jet production with leptonic decays

We compute the next-to-leading order QCD corrections to WZ+jet production at the Tevatron and the LHC, including decays of the electroweak bosons to light leptons with all off-shell effects taken into account. The corrections are sizable and have significant impact on the differential distributions.

hep-ph

Weak boson scattering at the Large Hadron Collider

Weak boson scattering processes provide particularly promising means for gaining insight into the mechanism of electroweak symmetry breaking at hadron colliders. Being very sensitive to interactions in the weak gauge boson sector, they will help to distinguish the Standard Model from various new physics scenarios such as extra-dimensional Higgsless models. To unambiguously identify signatures of new physics, precise predictions for experimentally accessible observables within realistic selection cuts are crucial, including next-to-leading order QCD corrections. Here, we review how flexible Monte-Carlo methods can be employed for precision analyses of weak boson scattering reactions within the Standard Model and beyond.

hep-ph

The Hunt for New Physics at the Large Hadron Collider

The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Additionally, the LHC will be a top factory and accurate measurements of the properties of the top and its rare decays will provide a window to new physics. Further, the LHC could shed light on the origin of neutralino masses if the new physics associated with their generation lies in the TeV region. Finally, the LHC is also a laboratory to test the hypothesis of TeV scale strings and D-brane models. An overview of these possibilities is presented in the spirit that it will serve as a companion to the Technical Design Reports (TDRs) by the particle detector groups ATLAS and CMS to facilitate the test of the new theoretical ideas at the LHC. Which of these ideas stands the test of the LHC data will govern the course of particle physics in the subsequent decades.

hep-ph

NLO-QCD corrections to $Wγj$ production

We calculate the $W^\pmγj + X$-production cross sections at next-to-leading order QCD for Tevatron and LHC collisions. We include leptonic decays of the $W$ to light leptons, with all off-shell effects taken into account. The corrections are sizable and have significant impact on the differential distributions.

hep-ph

NLO QCD corrections to W+W- gamma and Z Z gamma production with leptonic decays

The computation of the NLO QCD corrections to the cross sections for W+W- gamma and ZZgamma production in hadronic collisions is presented. We consider the case of a real photon in the final state, but include full leptonic decays of the W and Z bosons. Numerical results for the LHC and the Tevatron are obtained through a fully flexible parton level Monte Carlo based on the structure of the VBFNLO program, allowing an easy implementation of arbitrary cuts and distributions. We show the dependence on scale variations of the integrated cross sections and provide evidence that NLO QCD corrections strongly modify the LO predictions for observables at the LHC both in magnitude and in shape.

hep-ph