Antenna subtraction at NNLO with identified hadrons

We extend the antenna subtraction method to include hadron fragmentation processes up to next-to-next-to-leading order (NNLO) in QCD in $e^+e^-$ collisions. To handle collinear singularities associated with the fragmentation process, we introduce fragmentation antenna functions in final-final kinematics with associated phase space mappings. These antenna functions are integrated over the relevant phase spaces, retaining their dependence on the momentum fraction of the fragmenting parton. The integrated antenna functions are cross-checked against the known NNLO coefficient functions for identified hadron production from $\gamma^*/Z^* \to q\bar{q}$ and $H \to gg$ processes.Comment: 33 pages, 2 tables, two ancillary files with the expressions for the NNLO fragmentation antenna functions enclose

Antenna subtraction at NNLO with identified hadrons

We extend the antenna subtraction method to include hadron fragmentation processes up to next-to-next-to-leading order (NNLO) in QCD in e$^{+}$e$^{−}$ collisions. To handle collinear singularities associated with the fragmentation process, we introduce fragmentation antenna functions in final-final kinematics with associated phase space mappings. These antenna functions are integrated over the relevant phase spaces, retaining their dependence on the momentum fraction of the fragmenting parton. The integrated antenna functions are cross-checked against the known NNLO coefficient functions for identified hadron production from $${\gamma}^{\ast }/{Z}^{\ast}\to q\overline{q}$$ and H → gg processes

The muon parton distribution functions

We compute the Parton Distribution Functions (PDFs) of the unpolarised muon for the leptons, the photon, the light quarks, and the gluon. We discuss in detail the issues stemming from the necessity of evaluating the strong coupling constant at scales of the order of the typical hadron mass, and compare our novel approach with those currently available in the literature. While we restrict our phenomenological results to be leading-logarithmic accurate, we set up our formalism in a way that renders it straightforward to achieve next-to-leading logarithmic accuracy in the QED, QCD, and mixed QED$\times$QCD contributions.Comment: 20 pages, 4 figure

Identified hadrons in antenna subtraction at NNLO

Processes with identified hadrons require the introduction of fragmentation functions to describe the hadronisation of a quark or a gluon into the observed hadron particle. Such identified particles in the final state make the treatment of infrared divergences more subtle, because of additional collinear divergences to be handled. We extend the antenna subtraction method to include hadron fragmentation processes up to next-to-next-to-leading order (NNLO) in QCD in e+e− collisions. To this end, we introduce new double-real and real-virtual fragmentation antenna functions in the final-final kinematics, with associated phase space mappings. These antenna functions are integrated over the relevant phase spaces, retaining their dependence on the momentum fraction of the fragmenting parton

A dress of flavour to suit any jet

Identifying the flavour of reconstructed hadronic jets is critical for precision phenomenology and the search for new physics at collider experiments, as it allows to pinpoint specific scattering processes and reject backgrounds. Jet measurements at the LHC are almost universally performed using the anti-$k_T$ algorithm, however no approach exists to define the jet flavour for this algorithm that is infrared and collinear (IRC) safe. We propose a new approach, a flavour dressing algorithm, that is IRC safe to all orders in perturbation theory and can be combined with any definition of a jet. We test the algorithm in $\mathrm{e}^+\mathrm{e}^-$ and $\mathrm{p}\mathrm{p}$ environments, and consider the $\mathrm{p}\mathrm{p} \to \mathrm{Z}+\mathrm{b}\text{-jet}$ process as a practical application.Comment: 6 pages, 2 figures. v2: revision of original algorithm due to infrared and collinear safety issue

Semi-inclusive deep-inelastic scattering at NNLO in QCD

Semi-inclusive hadron production processes in deep-inelastic lepton-nucleon scattering are important probes of the quark flavour structure of the nucleon and of the fragmentation dynamics of quarks into hadrons. We compute the full next-to-next-to-leading order (NNLO) QCD corrections to the coefficient functions for semi-inclusive deep-inelastic scattering (SIDIS) in analytical form. The numerical impact of these corrections for precision physics is illustrated by a detailed comparison with data on single inclusive hadron spectra from the CERN COMPASS experiment.Comment: 6 pages, 3 figures; v2: version to be publishe

Semi-Inclusive Deep-Inelastic Scattering at Next-to-Next-to-Leading Order in QCD

Semi-inclusive hadron production processes in deep-inelastic lepton-nucleon scattering are important probes of the quark flavor structure of the nucleon and of the fragmentation dynamics of quarks into hadrons. We compute the full next-to-next-to-leading order QCD corrections to the coefficient functions for semi-inclusive deep-inelastic scattering in analytical form. The numerical impact of these corrections for precision physics is illustrated by a detailed comparison with data on single inclusive hadron spectra from the CERN COMPASS experiment

Flavor Identification of Reconstructed Hadronic Jets

Identifying the flavor of reconstructed hadronic jets is critical for precision phenomenology and the search for new physics at collider experiments, as it allows one to pinpoint specific scattering processes and reject backgrounds. Jet measurements at the LHC are almost universally performed using the anti-kT algorithm; however, no approach exists to define the jet flavor for this algorithm that is infrared and collinear safe. We propose a new approach, a flavor-dressing algorithm, that is infrared and collinear safe in perturbation theory and can be combined with any definition of a jet. We test the algorithm in an e+e- environment and consider the pp→Z+b-jet process as a practical application at hadron colliders

Heavy Quark Fragmentation in e+e−e^+e^- Collisions to NNLO+NNLL Accuracy in Perturbative QCD

Fragmentation of heavy quarks into heavy-flavoured hadrons receives both perturbative and non-perturbative contributions. We consider perturbative QCD corrections to heavy quark production in $e^+e^-$ collisions to next-to-next-to-leading order accuracy in QCD with next-to-next-to-leading-logarithmic resummation of quasi-collinear and soft emissions. We study multiple matching schemes, and multiple regularisations of the soft resummation, and observe a significant dependence of the perturbative results on these ingredients, suggesting that NNLO+NNLL perturbative accuracy may not lead to real gains unless the interface with non-perturbative physics is properly analysed. We confirm previous evidence that $D^{*+}$ experimental data from CLEO/BELLE and from LEP are not reconcilable with perturbative predictions employing standard DGLAP evolution. We extract non-perturbative contributions from $e^+e^-$ experimental data for both $D$ and $B$ meson fragmentation. Such contributions can be used to predict heavy-quark fragmentation in other processes, e.g. DIS and proton-proton collisions.Comment: 43 pages, 15 figures, 2 tables; v2 matches the published versio

Heavy quark fragmentation in e+e− collisions to NNLO+NNLL accuracy in perturbative QCD

Abstract Fragmentation of heavy quarks into heavy-flavoured hadrons receives both perturbative and non-perturbative contributions. We consider perturbative QCD corrections to heavy quark production in e$^{+}$e$^{−}$ collisions to next-to-next-to-leading order accuracy in QCD with next-to-next-to-leading-logarithmic resummation of quasi-collinear and soft emissions. We study multiple matching schemes, and multiple regularisations of the soft resummation, and observe a significant dependence of the perturbative results on these ingredients, suggesting that NNLO+NNLL perturbative accuracy may not lead to real gains unless the interface with non-perturbative physics is properly analysed. We confirm previous evidence that D$^{*+}$ experimental data from CLEO/BELLE and from LEP are not reconcilable with perturbative predictions employing standard DGLAP evolution. We extract non-perturbative contributions from e$^{+}$e$^{−}$ experimental data for both D and B meson fragmentation. Such contributions can be used to predict heavy-quark fragmentation in other processes, e.g. DIS and proton-proton collisions