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Daniel de Florian

Publications and source records attributed to Daniel de Florian.

86 records · Page 5Linked to original sources
arXiv2007

Global Analysis of Fragmentation Functions for Protons and Charged Hadrons

We present new sets of fragmentation functions for protons and inclusive charged hadrons obtained in combined NLO QCD analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering. These analyses complement previous results for pion and kaon fragmentation functions with charge and flavor discrimination. The Lagrange multiplier technique is used to assess the uncertainties in the extraction of the new sets of fragmentation functions.

hep-ph↗
arXiv2007

Resummed Cross Section for Jet Production at Hadron Colliders

We study the resummation of large logarithmic perturbative corrections to the single-inclusive jet cross section at hadron colliders. The corrections we address arise near the threshold for the partonic reaction, when the incoming partons have just enough energy to produce the high-transverse-momentum final state. The structure of the resulting logarithmic corrections is known to depend crucially on the treatment of the invariant mass of the produced jet at threshold. We allow the jet to have a non-vanishing mass at threshold, which most closely corresponds to the situation in experiment. Matching our results to available semi-analytical next-to-leading-order calculations, we derive resummed results valid to next-to-leading logarithmic accuracy. We present numerical results for the resummation effects at Tevatron and RHIC energies.

hep-ph↗
arXiv2006

The last of the seven-parton tree amplitudes

We compute the four-quark plus three-gluon and six-quark plus one-gluon tree level amplitudes using on-shell recursion relations. They are needed for the calculation of the 5-jet cross-section at the Born level, and constitute an essential ingredient for next-to-leading order 4-jet and next-to-next-to-leading order 3-jet production at hadronic colliders. Very compact expressions for all possible helicity configurations are provided, allowing direct implementation in computer codes. With the results presented in this paper, the full set of seven-parton tree amplitudes becomes available.

hep-ph↗
arXiv2006

Seven parton amplitudes from recursion relations

We present the first calculation of two-quark and five-gluon tree amplitudes using on-shell recursion relations. These amplitudes are needed for tree level 5-jet cross-section and an essential ingredient for next-to-leading order 4-jet and next-to-next-to-leading order 3-jet production at hadronic colliders. Very compact expressions for all possible helicity configurations are provided, allowing for direct implementation in Monte-Carlo codes.

hep-ph↗
arXiv2005

Threshold resummation for the prompt-photon cross section revisited

We study the resummation of large logarithmic perturbative corrections to the partonic cross sections relevant for the process pp->gamma X at high transverse momentum of the photon.These corrections arise near the threshold for the partonic reaction and are associated with soft-gluon emission. We especially focus on the resummation effects for the contribution to the cross section where the photon is produced in jet fragmentation. Previous calculations in perturbation theory at fixed-order have established that this contribution is a subdominant part of the cross section. We find, however, that it is subject to much larger resummation effects than the direct (non-fragmentation) piece and therefore appears to be a significant contribution in the fixed-target regime, not much suppressed with respect to the direct part. Inclusion of threshold resummation for the fragmentation piece leads to some improvement in comparisons between theoretical calculations and experimental data.

hep-ph↗
arXiv2005

Threshold Resummation for the Inclusive-Hadron Cross-Section in pp Collisions

We study the resummation of large logarithmic perturbative corrections to the partonic cross sections relevant for the process pp->h X at high transverse momentum of the hadron h. These corrections arise near the threshold for the partonic reaction and are associated with soft-gluon emission. We perform the resummation to next-to-leading logarithmic accuracy. We present numerical results for the fixed-target regime and find enhancements over the next-to-leading order cross section, which significantly improve the agreement between theoretical predictions and data. We also apply the resummation for RHIC kinematics and find that subleading terms appear to play a rather important role here.

hep-ph↗
arXiv2004

Collinear splitting, parton evolution and the strange-quark asymmetry of the nucleon in NNLO QCD

We consider the collinear limit of QCD amplitudes at one-loop order, and their factorization properties directly in colour space. These results apply to the multiple collinear limit of an arbitrary number of QCD partons, and are a basic ingredient in many higher-order computations. In particular, we discuss the triple collinear limit and its relation to flavour asymmetries in the QCD evolution of parton densities at three loops. As a phenomenological consequence of this new effect, and of the fact that the nucleon has non-vanishing quark valence densities, we study the perturbative generation of a strange--antistrange asymmetry $s(x)-\bar{s}(x)$ in the nucleon's sea.

hep-ph↗
arXiv2004

Perturbative generation of a strange-quark asymmetry in the nucleon

We point out that perturbative evolution in QCD at three loops generates a strange-antistrange asymmetry s(x)-sbar(x) in the nucleon's sea just from the fact that the nucleon has non-vanishing up and down quark valence densities. The recently computed three-loop splitting functions allow for an estimate of this effect. We find that a fairly sizable asymmetry may be generated. Results for analogous asymmetries in the heavy-quark sector are also presented.

hep-ph↗
arXiv2004

The triple collinear limit of one-loop QCD amplitudes

We consider the singular behaviour of one-loop QCD matrix elements when several external partons become simultaneously parallel. We present a new factorization formula that describes the singular collinear behaviour directly in colour space. The collinear singularities are embodied in process-independent splitting matrices that depend on the momenta, flavours, spins and colours of the collinear partons. We give the general structure of the infrared and ultraviolet divergences of the one-loop splitting matrices. We also present explicit one-loop results for the triple collinear splitting, $q \to q {\bar Q} Q$, of a quark and a quark--antiquark pair of different flavours. The one-loop triple collinear splitting is one of the ingredients that can be used to compute the evolution of parton distributions at the next-to-next-to-leading order in QCD perturbation theory.

hep-ph↗
arXiv2002

Next-to-leading order QCD corrections to one hadron-production in polarized pp collisions at RHIC

We calculate the next-to-leading order QCD corrections to the spin-dependent cross section for single-inclusive hadron production in hadronic collisions. This process will be soon studied experimentally at RHIC, providing a tool to unveil the polarized gluon distribution $Δg$. We observe a considerably improvement in the perturbative stability for both unpolarized and polarized cross sections. The NLO corrections are found to be non-trivial, resulting in a reduction of the asymmetry.

hep-ph↗
arXiv1999

Polarized Fragmentation Functions

In this talk I present a review on the theoretical status of polarized fragmentation functions and the prospects for conceivable future semi-inclusive deep-inelastic scattering and proton-proton collision experiments to measure them.

hep-ph↗
arXiv1997

Next to Leading Order Analysis of Semi-Inclusive DIS

We present a combined NLO analysis to data on both inclusive and semi-inclusive polarized asymmetries. We present also the NLO corrections to the direct part of the polarized photoproduction of charged hadrons.

hep-ph↗
arXiv1997

Phenomenology of Forward Hadrons in DIS: Fracture Functions and its $Q^2$ Evolution

We analyse recent data on the production of forward neutrons in deep inelastic scattering at HERA in the framework of a perturbative QCD description for semi-inclusive processes, which includes fracture functions. Using a model estimate for the non-perturbative piece of the fragmentation process, in fairly good agreement with the available data, we analyse the $Q^2$ dependence of the resulting fracture functions, which is driven by non-homogeneous evolution equations. We also propose a measurement of the pion production cross section in the target fragmentation region as a new test of perturbative QCD, which in this case predicts also a different $Q^2$ evolution with respect to the one given by the usual Altarelli-Parisi equations.

hep-ph↗