Searcharxiv⌕ Search

arXiv subjects

M. Rogal

Publications and source records attributed to M. Rogal.

13 recordsLinked to original sources
arXiv2009

Parton Distributions

We provide an assessment of the state of the art in various issues related to experimental measurements, phenomenological methods and theoretical results relevant for the determination of parton distribution functions (PDFs) and their uncertainties, with the specific aim of providing benchmarks of different existing approaches and results in view of their application to physics at the LHC. We discuss higher order corrections, we review and compare different approaches to small x resummation, and we assess the possible relevance of parton saturation in the determination of PDFS at HERA and its possible study in LHC processes. We provide various benchmarks of PDF fits, with the specific aim of studying issues of error propagation, non-gaussian uncertainties, choice of functional forms of PDFs, and combination of data from different experiments and different processes. We study the impact of combined HERA (ZEUS-H1) structure function data, their impact on PDF uncertainties, and their implications for the computation of standard candle processes, and we review the recent F_L determination at HERA. Finally, we compare and assess methods for luminosity measurements at the LHC and the impact of PDFs on them.

hep-ph↗
arXiv2008

Heavy quark pair production in gluon fusion at next-to-next-to-leading ${\cal O}(α_s^4)$ order: One-loop squared contributions

We calculate the next-to-next-to-leading order ${\cal O}(α_s^4)$ one-loop squared corrections to the production of heavy-quark pairs in the gluon-gluon fusion process. Together with the previously derived results on the $q \bar{q}$ production channel the results of this paper complete the calculation of the one-loop squared contributions of the next-to-next-to-leading order ${\cal O}(α_s^4)$ radiative QCD corrections to the hadroproduction of heavy flavors. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in dimensional regularization.

hep-ph↗
arXiv2008

Towards the NNLO evolution of polarised parton distributions

We report on the first calculation of the structure function g_1 in polarised deep-inelastic scattering to the third order in massless perturbative QCD. The calculation follows the dispersive approach already used for the corresponding unpolarised cases of F_2,L, but additionally involves higher tensor integrals and the Dirac matrix gamma_5 in D unequal 4 dimensions. Our results confirm all known two-loop expressions including the coefficient functions of Zijlstra and van Neerven not independently verified before. At three loops we extract the helicity-difference next-to-next-to-leading order (NNLO) quark-quark and gluon-quark splitting functions Delta P_qq and Delta P_qg. The results exhibit interesting features concerning sum rules and the momentum-fraction limits x to 1 and x to 0.

hep-ph↗
arXiv2008

Next-to-next-to-leading order ${\cal O}(α_s^4)$ results for heavy quark pair production in quark--antiquark collisions: The one-loop squared contributions

We calculate the next-to-next-to-leading order ${\cal O}(α_s^4)$ one-loop squared corrections to the production of heavy quark pairs in quark-antiquark annihilations. These are part of the next-to-next-to-leading order ${\cal O}(α_s^4)$ radiative QCD corrections to this process. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in the dimensional regularization scheme. We have found very intriguing factorization properties for the finite part of the amplitudes.

hep-ph↗
arXiv2007

CC DIS at alpha_s^3 in Mellin-N and Bjorken-x spaces

Third-order results for the structure functions of charged-current deep-inelastic scattering are discussed. New results for 11'th Mellin moment for F_2,L^(nu P - nubar P) structure functions and 12'th moment for F_3^(nu P - nubar P) are presented as well as corresponding higher Mellin moments of differences between the respective crossing-even and -odd coefficient functions. Approximations in Bjorken-x space for these differences obtained with lowest five moments as well as consistency of new results with these approximations are discussed. The 1/N_c suppression of the differences is shown and the correction to the Paschos-Wolfenstein relation is discussed.

hep-ph↗
arXiv2007

Differences between charged-current coefficient functions

Second- and third-order results are presented for the structure functions of charged-current deep-inelastic scattering in the framework of massless perturbative QCD. We write down the two-loop differences between the corresponding crossing-even and -odd coefficient functions, including those for the longitudinal structure function not covered in the literature so far. At three loops we compute the lowest five moments of these differences for all three structure functions and provide approximate expressions in Bjorken-$x$ space. Also calculated is the related third-order coefficient-function correction to the Gottfried sum rule. We confirm the conjectured suppression of these quantities if the number of colours is large. Finally we derive the second- and third-order QCD contributions to the Paschos-Wolfenstein ratio used for the determination of the weak mixing angle from neutrino-nucleon deep-inelastic scattering. These contributions are found to be small.

hep-ph↗
arXiv2007

Higher Mellin moments for charged current DIS

We report on our recent results for deep-inelastic neutrino-proton scattering. We have computed the perturbative QCD corrections to three loops for the harged current structure functions F_2, F_L and F_3 for the combination nu P - nubar P. In leading twist approximation we have calculated the first six odd-integer Mellin moments in the case of F_2 and F_L and the first six even-integer moments in the case of F_3. As a new result we have obtained the coefficient functions to O(alpha_s^3) and we have found the corresponding anomalous dimensions to agree with known results in the literature.

hep-ph↗
arXiv2007

Charged current deep-inelastic scattering at three loops

We derive for deep-inelastic neutrino-proton scattering in the combination nu P - nubar P the perturbative QCD corrections to three loops for the charged current structure functions F_2, F_L and F_3. In leading twist approximation we calculate the first five odd-integer Mellin moments in the case of F_2 and F_L and the first five even-integer moments in the case of F_3. As a new result we obtain the coefficient functions to O(alpha_s^3) while the corresponding anomalous dimensions agree with known results in the literature.

hep-ph↗
arXiv2006

Next-to-next-to-leading order ${\cal O}(α^2α_s^2)$ results for top quark pair production in photon--photon collisions: The one-loop squared contributions

We calculate the one-loop squared contributions to the next-to-next-to-leading order ${\cal O}(α^2α_s^2)$ radiative QCD corrections for the production of heavy quark pairs in the collisions of unpolarized on--shell photons. In particular, we present analytical results for the squared matrix elements that correspond to the product of the one--loop amplitudes. All results of the perturbative calculation are given in the dimensional regularization scheme. These results represent the Abelian part of the corresponding gluon--induced next-to-next-to-leading order cross section for heavy quark pair hadroproduction.

hep-ph↗
arXiv2006

Laurent series expansion of a class of massive scalar one-loop integrals up to ${\cal O}(\ep^2)$ in terms of multiple polylogarithms

In a recent paper we have presented results for a set of massive scalar one-loop master integrals needed in the NNLO parton model description of the hadroproduction of heavy flavors. The one--loop integrals were evaluated in $n=4-2\ep$ dimension and the results were presented in terms of a Laurent series expansion up to ${\cal O}(\ep^2)$. We found that some of the $\ep^2$ coefficients contain a new class of functions which we termed the $L$ functions. The $L$ functions are defined in terms of one--dimensional integrals involving products of logarithm and dilogarithm functions. In this paper we derive a complete set of algebraic relations that allow one to convert the $L$ functions of our previous approach to a sum of classical and multiple polylogarithms. Using these results we are now able to present the $\ep^2$ coefficients of the one-loop master integrals in terms of classical and multiple polylogarithms.

hep-ph↗
arXiv2006

One-loop amplitudes for four-point functions with two external massive quarks and two external massless partons up to O(epsilon^2)

We present complete analytical ${\mathcal O}(ε^2)$ results on the one-loop amplitudes relevant for the NNLO quark-parton model description of the hadroproduction of heavy quarks as given by the so-called loop-by-loop contributions. All results of the perturbative calculation are given in the dimensional regularization scheme. These one-loop amplitudes can also be used as input in the determination of the corresponding NNLO cross sections for heavy flavor photoproduction, and in photon-photon reactions.

hep-ph↗
arXiv2005

Laurent series expansion of a class of massive scalar one-loop integrals to ${\cal O}(\ep^2)

We use dimensional regularization to calculate the ${\cal O}(\ep^2)$ expansion of all scalar one-loop one-, two-, three- and four-point integrals that are needed in the calculation of hadronic heavy quark production. The Laurent series up to ${\cal O}(\ep^2)$ is needed as input to that part of the NNLO corrections to heavy flavor production at hadron colliders where the one-loop integrals appear in the loop-by-loop contributions. The four-point integrals are the most complicated. The ${\cal O}(\ep^2)$ expansion of the three- and four-point integrals contains in general polylogarithms up to ${\rm Li}_4$ and functions related to multiple polylogarithms of maximal weight and depth four.

hep-ph↗