A
bstract
The transverse momentum distribution of massive neutral vector bosons can be measured to high accuracy at hadron colliders. The transverse momentum is caused by a partonic recoil, and is ...determined by QCD dynamics. We compute the single and double-differential transverse momentum distributions for fully inclusive
Z/γ
∗
production including leptonic decay to next-to-next-to-leading order (NNLO) in perturbative QCD. We also compute the same distributions normalised to the cross sections for inclusive
Z/γ
∗
production, i.e. integrated over the transverse momentum of the lepton pair. We compare our predictions for the fiducial cross sections to the 8 TeV data set from the ATLAS and CMS collaborations, which both observed a tension between data and NLO theory predictions, using the experimental cuts and binning. We find that the inclusion of the NNLO QCD effects does not fully resolve the tension with the data for the unnormalised
p
T
Z
distribution. However, we observe that normalising the NNLO
Z
-boson transverse momentum distribution by the NNLO Drell-Yan cross section substantially improves the agreement between experimental data and theory, and opens the way for precision QCD studies of this observable.
Precise predictions are provided for the production of a Z boson and a b-jet in hadron-hadron collisions within the framework of perturbative QCD, at O(α_{s}^{3}). To obtain these predictions, we ...perform the first calculation of a hadronic scattering process involving the direct production of a flavored jet at next-to-next-to-leading-order accuracy in massless QCD and extend techniques to also account for the impact of finite heavy-quark mass effects. The predictions are compared to CMS data obtained in pp collisions at a center-of-mass energy of 8 TeV, which are the most precise data from run I of the LHC for this process, where a good description of the data is achieved. To allow this comparison, we have performed an unfolding of the data, which overcomes the long-standing issue that the experimental and theoretical definitions of jet flavor are incompatible.
A
bstract
The angular distributions of lepton pairs in the Drell-Yan process can provide rich information on the underlying QCD production mechanisms. These dynamics can be parameterised in terms of ...a set of frame dependent angular coefficients,
A
i=0,…,7
, which depend on the invariant mass, transverse momentum, and rapidity of the lepton pair. Motivated by recent measurements of these coefficients by ATLAS and CMS, and in particular by the apparent violation of the Lam-Tung relation
A
0
−
A
2
= 0, we perform a precision study of the angular coefficients at
O
α
s
3
in perturbative QCD. We make predic-tions relevant for pp collisions at
s
=
8
TeV, and perform comparisons with the available ATLAS and CMS data as well as providing predictions for a prospective measurement at LHCb. To expose the violation of the Lam-Tung relationship we propose a new observable Δ
LT
= 1 −
A
2
/A
0
that is more sensitive to the dynamics in the region where
A
0
and
A
2
are both small. We find that the
O
α
s
3
corrections have an important impact on the
p
T,Z
distributions for several of the angular coefficients, and are essential to provide an adequate description of the data. The compatibility of the available ATLAS and CMS data is reassessed by performing a partial
χ
2
test with respect to the central theoretical prediction which shows that
χ
2
/N
data
is significantly reduced by going from
O
α
s
2
to
O
α
s
3
.
The production of a
W
-boson with a charm quark jet provides a highly sensitive probe of the strange quark distribution in the proton. Employing a novel flavour dressing procedure to define charm ...quark jets, we compute
W
+charm-jet production up to next-to-next-to-leading order (NNLO) in QCD. We study the perturbative stability of production cross sections with same-sign and opposite-sign charge combinations for the
W
boson and the charm jet. A detailed breakdown according to different partonic initial states allows us to identify particularly suitable observables for the study of the quark parton distributions of different flavours.
Final states with a vector boson and a hadronic jet allow one to infer the Born-level kinematics of the underlying hard scattering process, thereby probing the partonic structure of the colliding ...protons. At forward rapidities, the parton collisions are highly asymmetric and resolve the parton distributions at very large or very small momentum fractions, where they are less well constrained by other processes. Using theory predictions accurate to next-to-next-to-leading order (NNLO) in QCD for both
W
±
and
Z
production in association with a jet at large rapidities at the LHC, we perform a detailed phenomenological analysis of recent LHC measurements. The increased theory precision allows us to clearly identify specific kinematical regions where the description of the data is insufficient. By constructing ratios and asymmetries of these cross sections, we aim to identify possible origins of the deviations, and highlight the potential impact of the data on improved determinations of parton distributions.
A
bstract
We present the calculation of next-to-next-to-leading order (NNLO) corrections in perturbative QCD for the production of a Higgs boson decaying into a pair of bottom quarks in association ...with a leptonically decaying weak vector boson:
pp
→
V
H
+
X
→
ℓ
ℓ
¯
b
b
¯
+
X
.
We consider the corrections to both the production and decay sub-processes, retaining a fully differential description of the final state including off-shell propagators of the Higgs and vector boson. The calculation is carried out using the antenna subtraction formalism and is implemented in the NNLOjet framework. Clustering and identification of b-jets is performed with the flavour-k
t
algorithm and results for fiducial cross sections and distributions are presented for the LHC at
s
= 13 TeV. We assess the residual theory uncertainty by varying the production and decay scales independently and provide scale uncertainty bands in our results, yielding percent-level accurate predictions for observables in this Higgs production mode computed at NNLO. Confronting a na¨ıve perturbative expansion of the cross section against the customary re-scaling procedure to a fixed branching ratio reveals that starting from NNLO, the latter could be inadequate in estimating missing higher-order effects through scale variations.
We present the calculation of dijet production, doubly differential in dijet mass m_{jj} and rapidity difference |y^{*}|, at leading color 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 that display pathological behavior 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.
Fast interpolation-grid frameworks facilitate an efficient and flexible evaluation of higher-order predictions for any choice of parton distribution functions or value of the strong coupling
α
s
. ...They constitute an essential tool for the extraction of parton distribution functions and Standard Model parameters, as well as studies of the dependence of cross sections on the renormalisation and factorisation scales. The
APPLfast
project provides a generic interface between the parton-level Monte Carlo generator
and both the
APPLgrid
and the
fastNLO
libraries for the grid interpolation. The extension of the project to include hadron–hadron collider processes at next-to-next-to-leading order in perturbative QCD is presented, together with an application for jet production at the LHC.
The production of lepton pairs at low invariant mass and finite transverse momentum resolves QCD dynamics at the boundary between the perturbative and non-perturbative domains. We investigate the ...impact of NNLO QCD corrections on these observables at energies corresponding to the BNL RHIC collider and to fixed-target experiments. Satisfactory perturbative convergence is observed in both cases. Only the collider data are found to be well-described by perturbative QCD, thus indicating the importance of non-perturbative effects in lepton-pair transverse momentum distributions at fixed target energies.
The transverse momentum spectra of weak gauge bosons and their ratios probe the underlying dynamics and are crucial in testing our understanding of the standard model. They are an essential ...ingredient in precision measurements, such as the W boson mass extraction. To fully exploit the potential of the LHC data, we compute the second-order next-to-next-to-leading-order (NNLO) QCD corrections to the inclusive-p_{T}^{W} spectrum as well as to the ratios of spectra for W^{-}/W^{+} and Z/W. We find that the inclusion of NNLO QCD corrections considerably improves the theoretical description of the experimental CMS data and results in a substantial reduction of the residual scale uncertainties.
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