arXiv subjects

Alexander Huss

Publications and source records attributed to Alexander Huss.

53 records · Page 3Linked to original sources

arXiv2018

NNLO QCD Corrections to W+jet Production in NNLOJET

We give an overview of our calculation of the next-to-next-to-leading order (NNLO) QCD corrections to W + jet production in hadronic collisions. Phenomenological results for multiple differential distributions are compared to CMS data for 8 TeV proton-proton collisions. We further discuss the application of the calculation to the transverse momentum spectrum of inclusive W boson production, again accompanied by a comparison to 8 TeV CMS data. In both cases, the inclusion of NNLO QCD effects give an improved agreement between theory and data with considerably reduced scale uncertainties with respect to the next-to-leading order (NLO) results.

hep-ph↗

arXiv2018

NNLO corrections to VBF Higgs boson production

This talk expands on recently published results for the factorising next-to-next-to-leading order (NNLO) QCD corrections to Higgs boson production in the vector boson fusion (VBF) channel. The calculation is fully differential in the kinematics of the Higgs boson and the final state jets and is implemented in the NNLOJET framework for computing higher-order QCD corrections. We find the NNLO corrections to be limited in magnitude to about $\pm 5$\% with a weak kinematical dependence in the transverse momenta and rapidity separation of the two tagging jets.

hep-ph↗

arXiv2018

Jet cross sections at the LHC with NNLOJET

We review the status of NNLO calculations for jet cross sections at the LHC. In particular, we describe how perturbative stability and convergence can be used as criteria to select the most appropriate scales in the theoretical description of di-jet and single jet inclusive production.

hep-ph↗

arXiv2017

NNLO predictions for dijet production in diffractive DIS

Cross sections for inclusive dijet production in diffractive deep-inelastic scattering are calculated for the first time in next-to-next-to-leading order (NNLO) accuracy. These cross sections are compared to several HERA measurements published by the H1 and ZEUS collaborations. We computed the total cross sections, 49 single-differential and five double-differential distributions for six HERA measurements. The NNLO corrections are found to be large and positive. The normalization of the resulting predictions typically exceeds the data, while the kinematical shape of the data is described better at NNLO than at next-to-leading order (NLO). Our results use the currently available NLO diffractive parton distributions, and the discrepancy in normalization highlights the need for a consistent determination of these distributions at NNLO accuracy.

hep-ph↗

arXiv2017

Next-to-leading-order QCD and electroweak corrections to WWW production at proton-proton colliders

Triple-W-boson production in proton-proton collisions allows for a direct access to the triple and quartic gauge couplings and provides a window to the mechanism of electroweak symmetry breaking. It is an important process to test the Standard Model (SM) and might be background to physics beyond the SM. We present a calculation of the next-to-leading order (NLO) electroweak corrections to the production of WWW final states at proton-proton colliders with on-shell W bosons and combine the electroweak with the NLO QCD corrections. We study the impact of the corrections to the integrated cross sections and to kinematic distributions of the W bosons. The electroweak corrections are generically of the size of 5-10% for integrated cross sections and become more pronounced in specific phase-space regions. The real corrections induced by quark-photon scattering turn out to be as important as electroweak loops and photon bremsstrahlung corrections, but can be reduced by phase-space cuts. Considering that prior determinations of the photon parton distribution function (PDF) involve rather large uncertainties, we compare the results obtained with different photon PDFs and discuss the corresponding uncertainties in the NLO predictions. Moreover, we determine the scale and total PDF uncertainties at the LHC and a possible future 100 TeV pp collider.

hep-ph↗

arXiv2017

NNLO QCD corrections to event orientation in e+e- annihilation

We present a new implementation of the NNLO QCD corrections to three-jet final states and related event-shape observables in electron--positron annihilation. Our implementation is based on the antenna subtraction method, and is performed in the NNLOJET framework. The calculation improves upon earlier results by taking into account the full kinematical information on the initial state momenta, thereby allowing the event orientation to be computed to NNLO accuracy. We find the event-orientation distributions at LEP and SLC to be very robust under higher order QCD corrections.

hep-ph↗

arXiv2017

Precise predictions for dijet production at the LHC

We present the calculation of dijet production, doubly-differential in dijet mass, $m_{jj}$ and rapidity difference, $|y^{*}|$, at leading colour in all partonic channels at next-to-next-to-leading order (NNLO) in perturbative QCD. We consider the long-standing problems associated with scale choice for dijet production at next-to-leading order (NLO) and investigate the impact of including the NNLO contribution. We find that the NNLO theory provides reliable predictions, even when using scale choices which display pathological behaviour at NLO. We choose the dijet invariant mass as the theoretical scale on the grounds of perturbative convergence and residual scale variation and compare the predictions to the ATLAS 7 TeV 4.5 fb$^{-1}$ data.

hep-ph↗

arXiv2017

Differential single jet inclusive production at Next-to-Next-to-Leading Order in QCD

In this talk we present the recent calculation in all partonic channels of the fully differential single jet inclusive cross section at Next-to-Next-to-Leading Order in QCD. We discuss the size and shape of the perturbative corrections as a function of the functional form of the renormalisation and factorisation scales and compare the predictions at NLO and NNLO to the available ATLAS 7 TeV data. We find significant effects at low-$p_T$ due to changes in the functional form of the scale choice whereas at high-$p_T$ the two most common scale choices in the literature give identical results and the perturbative corrections lead to a substantial reduction in the scale dependence of the theoretical prediction at NNLO.

hep-ph↗

arXiv2017

Single jet inclusive production for the individual jet $p_{T}$ scale choice at the LHC

We study the single jet inclusive cross section up to next-to-next-to leading order in perturbative QCD, implemented in the parton-level event generator NNLOJET . Our results are fully differential in the jet transverse momentum and rapidity and we apply fiducial cuts for comparison with the available ATLAS 7 TeV 4.5 fb$^{-1}$ data for jet radius $R=0.4$. For the theoretical calculation we employ the antenna subtraction method to reliably cancel all infrared divergences present at intermediate stages of the calculation. We present all results using the individual jet transverse momentum $μ_{R}=μ_{F}\sim p_{T}$ as the renormalization and factorization scale for each jet's contribution to the single jet inclusive cross section. Finally, we consider the differences between our predictions using this scale choice to those for the leading jet transverse momentum scale choice, $μ_{R}=μ_{F}\sim p_{T_{1}}$, used in [14], with reference to the ATLAS data.

hep-ph↗

arXiv2016

Dominant $\mathcal{O}(α_sα)$ corrections to Drell-Yan processes in the resonance region

Apart from the well-known NNLO QCD and NLO electroweak corrections to W- and Z-boson production at hadron colliders, the most important fixed-order corrections are given by the mixed QCD-electroweak corrections of $\mathcal{O}(α_sα)$. The knowledge of these corrections is of particular importance to control the theoretical uncertainties in the upcoming high-precision measurements of the W-boson mass and the effective weak mixing angle at the LHC. Since these observables are dominated by the phase-space regions of resonant W/Z bosons, we address the $\mathcal{O}(α_sα)$ corrections in the framework of an expansion about the W/Z poles. Retaining only the leading, resonant contribution in the so-called pole approximation, the corrections can be classified into factorizable and non-factorizable contributions. In this article we review our calculation of the numerically dominant corrections which arise from factorizable corrections of "initial-final" type, i.e. they combine the QCD corrections to the production with the large electroweak corrections to the decay of the W/Z boson. Moreover, we compare our results to simpler approximate combinations of electroweak and QCD corrections based on naive products of NLO QCD and electroweak correction factors and using leading-logarithmic approximations for QED final-state radiation. Finally, we estimate the shift in the W-boson mass that results from the $\mathcal{O}(α_sα)$ corrections to the transverse-mass distribution.

hep-ph↗

arXiv2015

Dominant mixed QCD-electroweak $\mathcal{O}(α_sα)$ corrections to Drell-Yan processes in the resonance region

A precise theoretical description of W- and Z-boson production in the resonance region is essential for the correct interpretation of high-precision measurements of the W-boson mass and the effective weak mixing angle. Currently, the largest unknown fixed-order contribution is given by the mixed QCD-electroweak corrections of $\mathcal{O}(α_sα)$. We argue, using the framework of the pole expansion for the NNLO QCD-electroweak corrections established in a previous paper, that the numerically dominant corrections arise from the combination of large QCD corrections to the production with the large electroweak corrections to the decay of the W/Z boson. We calculate these so-called factorizable corrections of "initial-final" type and estimate the impact on the W-boson mass extraction. We compare our results to simpler approximate combinations of electroweak and QCD corrections in terms of naive products of NLO QCD and electroweak correction factors and using leading-logarithmic approximations for QED final-state radiation as provided by the structure-function approach or QED parton-shower programs. We also compute corrections of "final-final" type, which are given by finite counterterms to the leptonic vectorboson decays and are found to be numerically negligible.

hep-ph↗

arXiv2015

Techniques for the treatment of IR divergences in decay processes at NLO and application to the top-quark decay

We present the extension of two general algorithms for the treatment of infrared singularities arising in electroweak corrections to decay processes at next-to-leading order: the dipole subtraction formalism and the one-cutoff slicing method. The former is extended to the case of decay kinematics which has not been considered in the literature so far. The latter is generalized to production and decay processes with more than two charged particles, where new "surface" terms arise. Arbitrary patterns of massive and massless external particles are considered, including the treatment of infrared singularities in dimensional or mass regularization. As an application of the two techniques we present the calculation of the next-to-leading-order QCD and electroweak corrections to the top-quark decay width including all off-shell and decay effects of intermediate W bosons. The result, e.g., represents a building block of a future calculation of NLO electroweak effects to off-shell top-quark pair (WWbb) production. Moreover, this calculation can serve as the first step towards an event generator for top-quark decays at next-to-leading order accuracy, which can be used to attach top-quark decays to complicated many-particle top-quark processes, such as for tt+H or tt+jets.

hep-ph↗

arXiv2014

O(α_sα) corrections to Drell-Yan processes in the resonance region

Drell-Yan-like W-boson and Z-boson production in the resonance region allows for some high-precision measurements that are crucial to carry experimental tests of the Standard Model to the extremes, such as the determinations of the W-boson mass and the effective weak mixing angle. We describe how the Standard Model prediction can be successfully performed in terms of a consistent expansion about the resonance pole, which classifies the corrections in terms of factorizable and non-factorizable contributions. The former can be attributed to the W/Z production and decay subprocesses individually, while the latter link production and decay by soft-photon exchange. At next-to-leading order we compare the full electroweak corrections with the pole-expanded approximations, confirming the validity of the approximation. At O(α_sα), we describe the concept of the expansion and report on results on the non-factorizable contributions, which turn out to be phenomenologically negligible. Moreover, we present first (preliminary) results on the dominant factorizable O(α_sα) corrections, which originate from the interplay of initial-state QCD and final-state electroweak corrections. Numerically those corrections significantly differ from a mere product of the two next-to-leading-order correction factors.

hep-ph↗

arXiv2014

Mixed QCD-electroweak O(α_sα) corrections to Drell-Yan processes in the resonance region: pole approximation and non-factorizable corrections

Drell-Yan-like W-boson and Z-boson production in the resonance region allows for high-precision measurements that are crucial to carry experimental tests of the Standard Model to the extremes, such as the determination of the W-boson mass and the effective weak mixing angle. In this article, we establish a framework for the calculation of the mixed QCD-electroweak O(α_sα) corrections to Drell-Yan processes in the resonance region, which are one of the main remaining theoretical uncertainties. We describe how the Standard Model prediction can be successfully performed in terms of a consistent expansion about the resonance poles, which classifies the corrections in terms of factorizable and non-factorizable contributions. The former can be attributed to the W/Z production and decay subprocesses individually, while the latter link production and decay by soft-photon exchange. At next-to-leading order we compare the full electroweak corrections with the pole-expanded approximations, confirming the validity of the approximation. At O(α_sα), we describe the concept of the expansion and explicitly give results on the non-factorizable contributions, which turn out to be phenomenologically negligible. Our results, thus, demonstrate that for phenomenological purposes the O(α_sα) corrections can be factorized into terms associated with initial-state and/or final-state corrections. Moreover, we argue that the factorization properties of the non-factorizable corrections at O(α_sα) from lower-order O(α_s) graphs generalize to any order in O(α_s^nα).

hep-ph↗

arXiv2013

Electroweak Corrections at High Energies

We present a survey of the most abundant processes at the LHC for sensitivity to electroweak corrections at \sqrt{s} = 8, 14, 33, and 100 TeV proton-proton collision energies. The processes studied are pp -> dijet, inclusive W and Z, W/Z+jets, and WW. In each case we compare the experimental uncertainty in the highest kinematic regions of interest with the relative magnitude of electroweak corrections and fixed-order α_S calculations.

hep-ph↗

arXiv2013

Weak radiative corrections to dijet production at the LHC

We summarize the calculation of the weak corrections to dijet production at hadron colliders, comprising tree-level effects of O(α_sα,α^2) and loop corrections of O(α_s^2α). Although suppressed by the small value of the coupling constant α, the weak radiative corrections can become large in the high-energy domain due to the appearance of Sudakov-type and other high-energy logarithms. Generally the corrections to the transverse-momentum distributions are larger by approximately a factor of two compared to the corresponding reach in the invariant-mass distributions, because the invariant-mass distributions are not, unlike the k_T distributions, dominated by the Sudakov regime at high scales. The electroweak tree-level contributions are found to be of the same generic size as the loop corrections.

hep-ph↗

arXiv2012

Weak radiative corrections to dijet production at hadron colliders

We present the calculation of the most important electroweak corrections to dijet production at the LHC and the Tevatron, comprising tree-level effects of O(α_sα,α^2) and weak loop corrections of O(α_s^2α). Although negligible for integrated cross sections, these corrections can reach 10-20% in the TeV range for transverse jet momenta k_T. Our detailed discussion of numerical results comprises distributions in the dijet invariant mass and in the transverse momenta of the leading and subleading jets. We find that the weak loop corrections amount to about -12% and -10% for leading jets with k_T~3TeV at the 14TeV LHC and k_T~800GeV at the Tevatron, respectively. The electroweak tree-level contributions are of the same generic size and typically positive at the LHC and negative at the Tevatron at high energy scales. Generally the corrections to the dijet invariant mass distributions are smaller by at least a factor of two as compared to the corresponding reach in the k_T distributions, because unlike the k_T spectra the invariant-mass distributions are not dominated by the Sudakov regime at high energy scales.

hep-ph↗