QCD Jet Cross Sections Research Articles

Higher Order Corrections in the CoLoRFulNNLO Framework

We discuss the CoLoRFulNNLO method for computing higher order radiative corrections to jet cross sections in perturbative QCD. We apply our method to the calculation of event shapes and jet rates in three-jet production in electron-positron annihilation. We validate our code by comparing our predictions to previous results in the literature and present the jet cone energy fraction distribution at NNLO accuracy. We also present preliminary NNLO results for the three-jet rate using the Durham jet clustering algorithm matched to resummed predictions at NLL accuracy, and a comparison to LEP data.

Jet production in the CoLoRFulNNLO method: Event shapes in electron-positron collisions

We present the CoLoRFulNNLO method to compute higher order radiative corrections to jet cross sections in perturbative QCD. We apply our method to the computation of event shape observables in electron-positron collisions at NNLO accuracy and validate our code by comparing our predictions to previous results in the literature. We also calculate for the first time jet cone energy fraction at NNLO.

Higgs boson decay into b-quarks at NNLO accuracy

We compute the fully differential decay rate of the Standard Model Higgs boson into b-quarks at next-to-next-to-leading order (NNLO) accuracy in alpha_S. We employ a general subtraction scheme developed for the calculation of higher order perturbative corrections to QCD jet cross sections, which is based on the universal infrared factorization properties of QCD squared matrix elements. We show that the subtractions render the various contributions to the NNLO correction finite. In particular, we demonstrate analytically that the sum of integrated subtraction terms correctly reproduces the infrared poles of the two-loop double virtual contribution to this process. We present illustrative differential distributions obtained by implementing the method in a parton level Monte Carlo program. The basic ingredients of our subtraction scheme, used here for the first time to compute a physical observable, are universal and can be employed for the computation of more involved processes.

Fully Differential Decay Rate of a Standard Model Higgs Boson into Two $b$-jets at NNLO

We present a general method for computing QCD jet cross sections at next-to-next-to-leading order accuracy, called CoLoRFulNNLO. We also discuss how to combine the predictions for the production of a Standard Model Higgs boson and its decay into a b-quark pair, both computed at the next-to-next-to-leading order accuracy, to predict precisely the kinematic distributions of b-jets emerging in the process pp→ H +X → bb+X.

A subtraction scheme for computing QCD jet cross sections at NNLO: integrating the doubly unresolved subtraction terms

Abstract We finish the definition of a subtraction scheme for computing NNLO corrections to QCD jet cross sections. In particular, we perform the integration of the soft-type contributions to the doubly unresolved counterterms via the method of Mellin-Barnes representations. With these final ingredients in place, the definition of the scheme is complete and the computation of fully differential rates for electron-positron annihilation into two and three jets at NNLO accuracy becomes feasible.

A subtraction scheme for computing QCD jet cross sections at NNLO: integrating the iterated singly-unresolved subtraction terms

We perform the integration of all iterated singly-unresolved subtraction terms, as defined in ref. [1], over the two-particle factorized phase space. We also sum over the unresolved parton flavours. The final result can be written as a convolution (in colour space) of the Born cross section and an insertion operator. We spell out the insertion operator in terms of 24 basic integrals that are defined explicitly. We compute the coefficients of the Laurent-expansion of these integrals in two different ways, with the method of Mellin-Barnes representations and sector decomposition. Finally, we present the Laurent-expansion of the full insertion operator for the specific examples of electron-positron annihilation into two and three jets.

Subtraction with hadronic initial states at NLO: an NNLO-compatible scheme

We present an NNLO-compatible subtraction scheme for computing QCD jet cross sections of hadron-initiated processes at NLO accuracy. The scheme is constructed specifically with those complications in mind, that emerge when extending the subtraction algorithm to next-to-next-to-leading order. It is therefore possible to embed the present scheme in a full NNLO computation without any modifications.

Subtraction method of computing QCD jet cross sections at NNLO accuracy

We present a general subtraction method for computing radiative corrections to QCD jet cross sections at next-to-next-to-leading order accuracy. The steps needed to set up this subtraction scheme are the same as those used in next-to-leading order computations. However, all steps need non-trivial modifications, which we implement such that that those can be defined at any order in perturbation theory. We give a status report of the implementation of the method to computing jet cross sections in electron-positron annihilation at the next-to-next-to-leading order accuracy.

A subtraction scheme for computing QCD jet cross sections at NNLO: integrating the subtraction terms I

In previous articles we outlined a subtraction scheme for regularizing doubly-real emission and real-virtual emission in next-to-next-to-leading order (NNLO) calculations of jet cross sections in electron-positron annihilation. In order to find the NNLO correction these subtraction terms have to be integrated over the factorized unresolved phase space and combined with the two-loop corrections. In this paper we perform the integration of all one-parton unresolved subtraction terms.

A subtraction scheme for computing QCD jet cross sections at NNLO: regularization of doubly-real emissions

We present a subtraction scheme for computing jet cross sections in electron-positron annihilation at next-to-next-to-leading order accuracy in perturbative QCD. In this first part we deal with the regularization of the doubly-real contribution to the NNLO correction.

A subtraction scheme for computing QCD jet cross sections at NNLO: regularization of real-virtual emission

We present a generalization of the dipole subtraction scheme for computing jet cross sections in electron-positron annihilation at next-to-next-to-leading order accuracy in perturbative QCD. In this second part we deal with the regularization of the real-virtual contribution to the NNLO correction.

A general algorithm for calculating jet cross sections in NLO QCD

A general algorithm for calculating jet cross sections in NLO QCD

A general approach to jet cross sections in QCD

I illustrate a general formalism based upon the subtraction method for the calculation of next-to-leading order QCD cross sections for any number of jets in any type of hard collisions. I discuss the implementation of this formalism in a numerical program which generates partonic kinematical configurations with an appropriate weight, thus allowing the definition of arbitrary jet algorithms and cuts matching the experimental setup at the last step of the computation. I present results obtained with computer codes which calculate one-jet and two jet inclusive quantities in photon-hadron and hadron-hadron collisions.

A general algorithm for calculating jet cross sections in NLO QCD

We present a new general algorithm for calculating arbitrary jet cross sections in arbitrary scattering processes to next-to-leading accuracy in perturbative QCD. The algorithm is based on the subtraction method. The key ingredients are new factorization formulae, called dipole formulae, which implement in a Lorentz covariant way both the usual soft and collinear approximations, smoothly interpolating the two. The corresponding dipole phase space obeys exact factorization, so that the dipole contributions to the cross section can be exactly integrated analytically over the whole of phase space. We obtain explicit analytic results for any jet observable in any scattering or fragmentation process in lepton, lepton-hadron or hadron-hadron collisions. All the analytical formulae necessary to construct a numerical program for next-to-leading order QCD calculations are provided. The algorithm is straightforwardly implementable in general purpose Monte Carlo programs.

Calculation of QCD jet cross sections at next-to-leading order

A general method for calculating next-to-leading order cross sections in perturbative QCD is presented. The algorithm is worked out for calculating N -jet cross sections in hadron-hadron collisions. The generalization of the scheme to performing calculations for other QCD processes, such as electron-positron annihilation or deep-inelastic scattering is also straightforward. As an illustration several three jet cross section distributions in electron-positron annihilation, calculated using the algorithm, are presented.

Virtual-sparticle threshold effects on large- ET jet cross sections

We discuss the one-loop virtual-sparticle corrections to QCD jet cross sections at large E T and large dijet invariant masses, with reference to present Tevatron and future LHC collider experiments. We find characteristic peaks and dips in the sparticle threshold region, due to interferences with tree-level QCD diagrams. Their magnitudes may be several per cent of the parton subprocess cross sections, so they might provide a useful search tool that is complementary to the usual missing-energy signature for supersymmetry.

The dipole formalism for the calculation of QCD jet cross sections at next-to-leading order

In order to make quantitative predictions for jet cross sections in perturbative QCD, it is essential to calculate them to next-to-leading accuracy. This has traditionally been an extremely laborious process. Using a new formalism, imaginatively called the dipole formalism, we are able to construct a completely general algorithm for next-to-leading order calculations of arbitrary jet quantities in arbitrary processes. In this paper we present the basic ideas behind the algorithm and illustrate them with a simple example.

Nuclear dependence at large transverse momentum

We treat the anomalous nuclear dependence of high- p T jet and single-particle photoproduction cross sections in perturbative QCD. We show that the A α dependence is associated with multi-parton matrix elements in nuclei. Assuming a natural model for these correlation functions, we derive predictions for the x F, x T and energy dependence of the enhancement. Significant enhancements are found without introducing scales other than Λ QCD. The methods described may be applied to other high- p T nuclear cross sections.