Search

The computation of the single-differential top quark-antiquark pair ($\mathrm{t}\overline{\mathrm{t}}$) production cross section at NLO in the fixed-order expansion is examined consistently using the MSR and $\overline{\textrm{MS}}$ short-distance top quark mass schemes. A thorough investigation of the dependence of different regions of the $\mathrm{t}\overline{\mathrm{t}}$ invariant mass spectrum on the renormalization scales $R$ and $\mu_m$ of the MSR mass $m_\mathrm{t}^{\textrm{MSR}}(R)$ and $\overline{\textrm{MS}}$ mass $\overline{m}_\mathrm{t}(\mu_m)$, respectively, is carried out. We demonstrate that a scale choice of $R\sim 80$~GeV is important for the stability of the cross-section predictions for the low $\mathrm{t}\overline{\mathrm{t}}$ invariant mass range, which is important for a reliable extraction of the top quark mass. Furthermore, a choice of semi-dynamical renormalization and factorization scales is preferred. These findings are expected to remain valid once non-relativistic quasi-bound state effects are included in the low invariant mass region., Comment: 21 pages, 6 figures

The evolution kernels that govern the scale dependence of the generalized parton distributions are invariant under transformations of the $\mathrm{SL}(2,\mathrm R)$ collinear subgroup of the conformal group. Beyond one loop the symmetry generators, due to quantum effects, differ from the canonical ones. We construct the transformation which brings the {\it full} symmetry generators back to their canonical form and show that the eigenvalues (anomalous dimensions) of the new, canonically invariant, evolution kernel coincide with the so-called parity respecting anomalous dimensions. We develop an efficient method that allows one to restore an invariant kernel from the corresponding anomalous dimensions. As an example, the explicit expressions for NNLO invariant kernels for the twist two flavor-nonsinglet operators in QCD and for the planar part of the universal anomalous dimension in $ N=4$ SYM are presented.

We have computed the even-$N$ moments $N \leq 20$ of the gluon-to-quark splitting function $P_{\rm qg}$ at the fourth order of perturbative QCD via the renormalization of off-shell operator matrix elements. Our results, derived analytically for a general gauge group, agree with all results obtained for this function so far, in particular with the lowest five moments obtained via physical cross sections. Using our new moments and all available endpoint constraints, we construct approximations for the four-loop $P_{\rm qg}(x)$ that should be sufficient for a wide range of collider-physics applications. The N$^3$LO corrections resulting from these and the corresponding quark-quark splitting functions lead to a marked improvement of the perturbative accuracy for the scale derivative of the singlet quark distribution, with effects of 1% or less at $x \gtrsim 10^{\,-4}$ at a standard reference scale with $\alpha_s = 0.2$.

The evolution kernels that govern the scale dependence of the generalized parton distributions are invariant under transformations of the $\mathrm{SL}(2,\mathrm R)$ collinear subgroup of the conformal group. Beyond one loop the symmetry generators, due to quantum effects, differ from the canonical ones. We construct the transformation which brings the {\it full} symmetry generators back to their canonical form and show that the eigenvalues (anomalous dimensions) of the new, canonically invariant, evolution kernel coincide with the so-called parity respecting anomalous dimensions. We develop an efficient method that allows one to restore an invariant kernel from the corresponding anomalous dimensions. As an example, the explicit expressions for NNLO invariant kernels for the twist two flavor-nonsinglet operators in QCD and for the planar part of the universal anomalous dimension in $ N=4$ SYM are presented., Comment: 12 pages, two figures; The three-loop QCD kernel in electronic form is given in the ancillary file

The computation of the single-differential top quark-antiquark pair ($\mathrm{t}\overline{\mathrm{t}}$) production cross section at NLO in the fixed-order expansion is examined consistently using the MSR and $\overline{\textrm{MS}}$ short-distance top quark mass schemes. A thorough investigation of the dependence of the $\mathrm{t}\overline{\mathrm{t}}$ invariant mass spectrum on the renormalization scales $R$ and $\mu_m$ of the MSR mass $m_\mathrm{t}^{\textrm{MSR}}(R)$ and $\overline{\textrm{MS}}$ mass $\overline{m}_\mathrm{t}(\mu_m)$, respectively, is carried out. We demonstrate that a scale choice of $R\sim 80$~GeV is important for the stability of the cross-section predictions for the low $\mathrm{t}\overline{\mathrm{t}}$ invariant mass range, which is important for a reliable extraction of the top quark mass. Furthermore, a choice of semi-dynamical renormalization and factorization scales is preferred. These findings are expected to remain valid once non-relativistic quasi-bound state effects are included in the low invariant mass region.

We calculate the one-loop corrections to the soft anomalous dimension matrices for the production of a top-antitop quark pair in association with a jet at hadron colliders. This is a step forward towards implementing a procedure for the resummation of soft-gluon emission logarithms for the $t\bar{t}j + X$ hadroproduction process, that will enable the improvement of the accuracy of the $t\bar{t} j + X$ cross sections, beyond the current degree of knowledge. The latter, so far, has reached the next-to-leading order (NLO) level, complemented by the accuracy of the Shower Monte Carlo approaches used in matching the NLO computations to parton showers (PS) and by merging with matrix elements with a different number of light jets., 29 pages, 13 figures

We study the impact of the top quark mass renormalized in the MS‾ scheme on the tt¯H production cross-sections as an alternative to theory predictions with the conventionally used pole mass scheme. The differential cross-sections at next-to-leading order in perturbative QCD with stable top quarks show a moderate decrease in scale uncertainties for the MS‾ mass renormalization scheme compared to the on-shell one. The shape of the differential distributions is not affected much, the largest differences being observed in the invariant mass distributions of the tt¯ and the tt¯H systems.

Journal of high energy physics 05(5), 146 (2022). doi:10.1007/JHEP05(2022)146, We present phenomenological results for $ t\overline{t}j $ + X production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the $ t\overline{t}j $ + X process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the $ \mathcal{R} $ distribution, which depends on the invariant mass of the $ t\overline{t}j $-system, we present reference predictions in the on-shell, $ \overline{\mathrm{MS}} $ and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the top-quark mass from cross-section measurements., Published by SISSA, [Trieste]

We present phenomenological results for tt¯ j + X production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the tt¯ j + X process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the R distribution, which depends on the invariant mass of the tt¯ j-system, we present reference predictions in the on-shell, MS¯ and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the top-quark mass from cross-section measurements.

We present phenomenological results for $t\bar{t}j + X$ production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the $t\bar{t}j + X$ process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the ${\cal R}$ distribution, which depends on the invariant mass of the $t\bar{t}j$-system, we present reference predictions in the on-shell, $\overline{\mbox{MS}}$ and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the top-quark mass from cross-section measurements., 64 pages, LaTeX, 38 figures, 14 tables, slightly modified version, as in JHEP

Physics letters / B 841, 137915 (2023). doi:10.1016/j.physletb.2023.137915, We study the influence of theoretical systematic uncertainties due to the quark density on LHC experimental searches for $Z^\prime$-bosons. Using an approach originally proposed in the context of the ABMP16 PDF set for the high-$x$ behaviour of the quark density, we presents results on observables commonly used to study $Z^\prime$ signals in dilepton channels., Published by North-Holland Publ., Amsterdam

(2022)., We present phenomenological results for $t\bar{t}j + X$ production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the $t\bar{t}j + X$ process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the ${\cal R}$ distribution, which depends on the invariant mass of the $t\bar{t}j$-system, we present reference predictions in the on-shell, $\overline{\mbox{MS}}$ and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the top-quark mass from cross-section measurements.

We calculate the one-loop corrections to the soft anomalous dimension matrices for the production of a top-antitop quark pair in association with a jet at hadron colliders. This is a step forward towards implementing a procedure for the resummation of soft-gluon emission logarithms for the $t\bar{t}j + X$ hadroproduction process, that will enable the improvement of the accuracy of the $t\bar{t} j + X$ cross-sections, beyond the current degree of knowledge. The latter, so far, has reached the next-to-leading order (NLO) level, complemented by the accuracy of the Shower Monte Carlo approaches used in matching the NLO computations to parton showers and by merging with samples with a different number of light jets.

XLIV International Conference of Theoretical Physics "Matter To The Deepest 2021", MTTD2021, Katowice, Poland, 15 Sep 2021 - 17 Sep 2021; Acta physica Polonica / B / Proceedings supplement 15(2), 2-A4 (2022). doi:10.5506/APhysPolBSupp.15.2-A4, We introduce a new method for calculating the mixing matrix for non-singlet quark operators including total derivatives, based solely on their renormalization structure in the chiral limit. As input, the method requires the well-known forward anomalous dimensions, which determine the evolution of parton distribution functions, and a calculation of the matrix elements of operators without total derivatives. Assuming a large number of quark flavors $n_f$, we are able to calculate the mixing matrix to fifth order in the strong coupling $\alpha_s$ in the $\overline{\mbox{MS}}$-scheme., Published by Inst. of Physics, Jagellonian Univ., Cracow

Physics letters / B 832, 137195 (2022). doi:10.1016/j.physletb.2022.137195, We study the impact of the top quark mass renormalized in the $\overline{MS}$ scheme on the $t{\bar t}H$ production cross-sections as an alternative to theory predictions with the conventional the pole mass scheme. The differential cross-sections at next-to-leading order in perturbative QCD with stable top quarks show a moderate decrease in scale uncertainties for the $\overline{MS}$ mass renormalization scheme compared to the on-shell one.The shape of the differential distributions is not affected much, the largest differences being observed in the invariant mass distributions of the $t{\bar t}$ and the $t{\bar t}H$ systems., Published by North-Holland Publ., Amsterdam

41st International Conference on High Energy Physics, ICHEP 2022, Bologna, Italy, 6 Jul 2022 - 13 Jul 2022; Proceedings of Science / International School for Advanced Studies (ICHEP2022), 1069 (2022). doi:10.22323/1.414.1069, Single-differential cross section predictions for top quark pair production are presented at next-to-leading order, using running top quark mass renormalization schemes. The evolution of the mass of the top quark is performed in the MSR scheme $m_\mathrm{t}^{\textrm{MSR}}(\mu)$ for renormalization scales $\mu$ below the $\overline{\textrm{MS}}$ top quark mass $\overline{m}_\mathrm{t}(\overline{m}_\mathrm{t})$, and in the $\overline{\textrm{MS}}$ scheme $\overline{m}_\mathrm{t}(\mu)$ for scales above. In particular, the implementation of a mass renormalization scale independent of the strong coupling renormalization scale and factorization scale in quantum chromodynamics allows investigating independent dynamical scale variations. Furthermore, the first theoretically consistent extraction of the top quark MSR mass from experimental data is presented., Published by SISSA, Trieste

The precise measurement of the top-quark mass constitutes one of the main goals of the LHC top-quark physics program. One possibility to extract this parameter uses the $\rho_{\mathrm{s}}$ distribution, which depends on the invariant mass of the $t\bar{t}j$ system. To fully take advantage of the experimental accuracy achievable in measuring top quark production cross sections at the LHC, the theory uncertainties need to be well under control. We present a study of the effect of varying the input parameters of the theoretical calculation on the predicted $\rho_{\mathrm{s}}$ distribution. Thereby we studied the influence of the $R$ parameter in the jet reconstruction procedure, as well as the effect of various renormalization and factorization scale definitions and different PDF sets. A behaviour similar to the one presented here for the $\rho_{\mathrm{s}}$-distribution was also found for other differential distributions., 4 pages, LaTeX, 2 figures, Contribution to the 14th International Workshop on Top Quark Physics (videoconference), 13-17 September 2021

We study the impact of the top quark mass renormalized in the $\overline{\text{MS}}$ scheme on the $\text{t}\bar{\text{t}}\text{H}$ production cross-sections as an alternative to theory predictions with the conventionally used pole mass scheme. The differential cross-sections at next-to-leading order in perturbative QCD with stable top quarks show a moderate decrease in scale uncertainties for the $\overline{\text{MS}}$ mass renormalization scheme compared to the on-shell one. The shape of the differential distributions is not affected much, the largest differences being observed in the invariant mass distributions of the $\text{t}\bar{\text{t}}$ and the $\text{t}\bar{\text{t}}\text{H}$ systems., 22 pages, 7 figures

We present a detailed comparison of the fixed-order predictions computed by four publicly available computer codes for Drell-Yan processes at the LHC and Tevatron colliders. We point out that while there is agreement among the predictions at the next-to-leading order accuracy, the predictions at the next-to-next-to-leading order (NNLO) differ, whose extent depend on the observable. The sizes of the differences in general are at least similar, sometimes larger than the sizes of the NNLO corrections themselves. We demonstrate that the neglected power corrections by the codes that use global slicing methods for the regularization of double real emissions can be the source of the differences. Depending on the fiducial cuts, those power corrections become linear, hence enhanced as compared to quadratic ones that are considered standard.

Jets constructed via clustering algorithms (e.g., anti-$k_T$, soft-drop) have been proposed for many precision measurements, such as the strong coupling $\alpha_s$ and the nucleon intrinsic dynamics. However, the theoretical accuracy is affected by missing QCD corrections at higher orders for the jet functions in the associated factorization theorems. Their calculation is complicated by the jet clustering procedure. In this work, we propose a method to evaluate jet functions at higher orders in QCD. The calculation involves the phase space sector decomposition with suitable soft subtractions. As a concrete example, we present the quark-jet function using the anti-$k_T$ algorithm with E-scheme recombination at next-to-next-to-leading order.

We review the current status of perturbative corrections in QCD at four loops for scattering processes with space- and time-like kinematics at colliders, with specific focus on deep-inelastic scattering and electron-positron annihilation. The calculations build on the parametric reduction of loop and phase space integrals up to four-loop order using computer algebra programs such as FORM, designed for large scale computations.

We study the impact of the top quark mass renormalized in the $\overline{MS}$ scheme on the $t{\bar t}H$ production cross-sections as an alternative to theory predictions with the conventional the pole mass scheme. The differential cross-sections at next-to-leading order in perturbative QCD with stable top quarks show a moderate decrease in scale uncertainties for the $\overline{MS}$ mass renormalization scheme compared to the on-shell one.The shape of the differential distributions is not affected much, the largest differences being observed in the invariant mass distributions of the $t{\bar t}$ and the $t{\bar t}H$ systems.

The precise measurement of the top quark mass, which is a fundamental SM parameter, constitutes one of the main goals of the LHC top physics program. One approach to measure this quantity uses the $\rho_\mathrm{s}$ distribution, an observable depending on the invariant mass of the $t\bar{t}j$ system. To fully exploit the experimental accuracy achievable in measuring top quark production cross sections at the LHC, the theory uncertainties associated to these measurements need to be well under control. To this end we present a study of the effect of varying the theoretical input parameters in the calculation of differential cross sections of the $t\bar{t}j$ process. Thereby we studied the influence of the jet reconstruction procedure, as well as the effect of various renormalization and factorization scale definitions and different PDF sets. The variation of the $R$ parameter in the jet reconstruction algorithm was found to have negligible influence on the scale variation uncertainty. A strong reduction of scale uncertainties and a better behaviour of the NLO/LO ratios using selected dynamical scales instead of a static one in the high energy tails of differential distributions was observed. This is particularly interesting in the context of the top quark mass measurements through the $\rho_\mathrm{s}$ distribution, in which the perturbative stability can be improved by applying the proposed dynamical scale definition., Comment: 14 pages, LaTeX, 7 figures, Contribution to Matter To The Deepest: Recent Developments In Physics Of Fundamental Interactions XLIV International Conference of Theoretical Physics, 2021

The relationship between Feynman diagrams and hypergeometric functions is discussed. Special attention is devoted to existing techniques for the construction of the $\epsilon$-expansion. As an example, we present a detailed discussion of the construction of the epsilon-expansion of the Appell function $F_3$ around rational values of parameters via an iterative solution of differential equations. As a by-product, we have found that the one-loop massless pentagon diagram in dimension $d=3-2\epsilon$ is not expressible in terms of multiple polylogarithms. Another interesting example is the Puiseux-type solution involving a differential operator generated by a hypergeometric function of three variables. The holonomic properties of the $F_N$ hypergeometric functions are briefly discussed., Comment: Based on the talk given by M.Kalmykov at the workshop "Antidifferentiation and the Calculation of Feynman Amplitudes" Zeuthen, 4.10.2020-9.10.2020; v2: few references added, small style corrections

Using the approach based on conformal symmetry we calculate the two-loop coefficient function for the vector flavor-nonsinglet contribution to deeply-virtual Compton scattering (DVCS). The analytic expression for the coefficient function in momentum fraction space is presented in the $\overline{\text{MS}}$ scheme. The corresponding next-to-next-to-leading order correction to the Compton form factor $\mathcal{H}$ for a simple model of the generalized parton distribution appears to be rather large: a factor two smaller than the next-to-leading order correction, approximately $\sim 10$\% of the tree level result in the bulk of the kinematic range, for $Q^2=4$~GeV$^2$.

XXVII International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS2018, Torino, Italy, 16 Apr 2018 - 20 Apr 2018; 6 pp. (2019)., We consider the impact of the resummation of large logarithms, which appear in the QCD evolution of the heavy-quark distributions, on the phenomenology of deep-inelastic heavy-quark production. The heavy-quark PDFs are derived using the fixed-order matching conditions as a boundary for the QCD evolution and the result obtained is compared to the distributions defined by the matching conditions at all scales. With such an approach, the effect of heavy-quark PDF evolution is found to be sizable at LO and dramatically reduces at NLO. The NNLO evolved distributions are not very different from the NLO ones at large scales, however, show substantial differences at low virtualities, i.e. where the additional large logarithms are numerically not important, while a mismatch between the NLO accuracy of the matching conditions and the NNLO accuracy in the evolution kernels causes a substantial excess in the heavy-quark distributions. This excess propagates into the variable flavor number (VFN) scheme predictions for the deep-inelastic structure functions and has to be compensated by a decrease in the small-$x$ gluon distribution determined from PDF fits based on the VFN scheme, which should be considered as a theoretical uncertainty in VFN PDF fits and reaches $\sim 30\%$ for the small-$x$ gluon distribution extracted from the data on deep-inelastic charm-quark production.

Journal of high energy physics 2020(3), 116 (2020). doi:10.1007/JHEP03(2020)116, We study the threshold corrections for inclusive deep-inelastic scattering (DIS) and their all-order resummation. Using recent results for the QCD form factor, related anomalous dimensions and Mellin moments of DIS structure functions at four loops we derive the complete soft and collinear contributions to the DIS Wilson coefficients at four loops. For a general SU(n$_{c}$) gauge group the results are exact in the large-n$_{c}$ approximation and for QCD with n$_{c}$ = 3 we present precise approximations. We extend the threshold resummation exponent G$^{N}$ in Mellin-N space to the fifth logarithmic (N$^{4}$LL) order collecting the terms $ {\alpha}_{\mathrm{s}}^3 $(α$_{s}$ ln N)$^{n}$ to all orders in the strong coupling constant α$_{s}$. We study the numerical effect of the N$^{4}$LL corrections using both the fully exponentiated form and the expansion of the coefficient function in towers of logarithms. As a byproduct, we derive a numerical result for the complete pole structure of the QCD form factor in the parameter of dimensional regularization ε at four loops., Published by SISSA, [Trieste]

Journal of high energy physics 1902(02), 191 (2019). doi:10.1007/JHEP02(2019)191, QCD in non-integer $d=4-2\epsilon$ space-time dimensions enjoys conformal invariance at the special fine-tuned value of the coupling. Counterterms for composite operators in minimal subtraction schemes do not depend on $\epsilon$ by construction, and therefore the renormalization group equations for composite operators in physical (integer) dimensions inherit conformal symmetry. This observation can be used to restore the complete evolution kernels that take into account mixing with the operators containing total derivatives from their eigenvalues (anomalous dimensions). Using this approach we calculate the two-loop (NLO) evolution kernels for the leading twist flavor-singlet operators in the position space (light-ray operator) representation. As the main result of phenomenological relevance, in this way we are able to confirm the evolution equations of flavor-singlet generalized hadron parton distributions derived earlier by Belitsky and M\'uller using a different approach., Published by Springer Nature, Berlin [u.a.]

Bartels, Jochen "Strings and High Energy Scattering" in Particles, Strings and the Early Universe : The Structure of Matter and Space-Time / Haller, Johannes, Grefe, Michael (eds.), Verlag Deutsches Elektronen-Synchrotron : 2018; Hamburg : Verlag Deutsches Elektronen-Synchrotron 19-38 (2018). doi:10.3204/PUBDB-2018-00782/A3, While early string theory provided an intriguing explanation for the observed Regge trajectories of meson resonances, it failed to reproduce the correct high energy behavior of scattering amplitudes. This has changed with the AdS/CFT correspondence. In fact, string theory can now produce precision results even in the multi-Regge regime. In this note we review the status of high energy scattering in planar $\mathcal{N} = 4$ super-Yang--Mills theory, at weak, strong and intermediate coupling, with a focus on its integrability and the relation to string theory., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

The European physical journal / C 78(6), 477 (2018). doi:10.1140/epjc/s10052-018-5947-1, We perform a global fit of parton distribution functions (PDFs) together with the strong coupling constant $\alpha_s$ and the quark masses $m_c, m_b$ and $m_t$ at next-to-leading order (NLO) in QCD. The analysis applies the $\overline{MS}$ renormalization scheme for αs and all quark masses. It is performed in the fixed-flavor number scheme for $n_f = 3,4,5$ and uses the same data as the previous ABMP16 fit at next-to-next-to-leading order (NNLO). The new NLO PDFs complement the set of ABMP16 PDFs and are to be used consistently with NLO QCD predictions for hard scattering processes. At NLO we obtain the value $\alpha_s^{(n_f=5)}(M_Z) = 0.1191 \pm 0.0011$ compared to $\alpha_s^{(n_f=5)}(M_Z) = 0.1147 \pm 0.0008$ at NNLO., Published by Springer, Berlin

Moch, Sven-Olaf "Top-Quark Physics at the LHC" in Particles, Strings and the Early Universe : The Structure of Matter and Space-Time / Haller, Johannes, Grefe, Michael (eds.), Verlag Deutsches Elektronen-Synchrotron : 2018; Hamburg : Verlag Deutsches Elektronen-Synchrotron 255-269 (2018). doi:10.3204/PUBDB-2018-00782/B11, We report on the precision determination of the top-quark mass to next-to-next-to-leading order in QCD in well-defined renormalization schemes using data from the Large Hadron Collider for single-top and top-quark pair production. We also discuss the calibration of the so-called Monte Carlo top-quark mass parameter which is determined from a comparison to events with top-quark decay products. The implications of the measured value of the top-quark mass for conclusions about the stability of the electroweak vacuum state of our Universe are illustrated. At future lepton colliders, we provide for the first time matched exclusive calculations valid both at the top threshold and in the continuum, also fully differentially. In addition, we calculate fully off-shell top-pair production (also with an associated Higgs boson) at next-to-leading order in QCD, which allows to extract the top-Yukawa coupling with an unprecedented precision., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

We present the first threshold and jet radius jointly resummed cross section for single-inclusive hadronic jet production. We work at next-to-leading logarithmic accuracy and our framework allows for a systematic extension beyond the currently achieved precision. Longstanding numerical issues are overcome by performing the resummation directly in momentum space within Soft Collinear Effective Theory. We present the first numerical results for the LHC and observe an improved description of the available data. Our results are of immediate relevance for LHC precision phenomenology including the extraction of parton distribution functions and the QCD strong coupling constant.

The status of the determination of the strong coupling constant $\alpha_s$(M$^2_Z$) from deepinelastic scattering and related hard scattering data is reviewed.

We present an update of the ABM12 PDF analysis including improved constraints due to the final version of the inclusive DIS HERA data, the Tevatron and LHC data on the W- and Z-production and those on heavy-quark production in the electron- and neutrino-induced DIS at HERA and the fixed-target experiments NOMAD and CHORUS. We also check the impact of the Tevatron and LHC top-quark production data on the PDFs and the strong coupling constant. We obtain $\alpha_s(M_Z)=0.1145(9)$ and $0.1147(8)$ with and without the top-quark data included, respectively.

'High-precision as measurements: from LHC to FCC-ee' and 'Determination of the Fundamental Parameters in QCD', Mainz, Germany, 7 Mar 2016 - 11 Mar 2016 ; Modern physics letters / A 31(25), 1630023(2016). doi:10.1142/S0217732316300238, The status of the determination of the strong coupling constant $\alpha_{s}(M_{Z}^{2})$ from deep-inelastic scattering and related hard scattering data is reviewed., Published by World Scientific Publ., Singapur

International audience; The impact of recent measurements of heavy-flavour production in deep inelastic $ep$ scattering and in $pp$ collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions $x$ of the proton momentum, down to $x \sim 5 \times 10^{-6}$. This kinematic range is currently not covered by other experimental data in perturbative QCD fits.

The impact of recent measurements of heavy-flavour production in deep inelastic $ep$ scattering and in $pp$ collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions $x$ of the proton momentum, down to $x \sim 5 \times 10^{-6}$. This kinematic range is currently not covered by other experimental data in perturbative QCD fits.

The single-logarithmic enhancement of the physical kernel for Higgs production by gluon-gluon fusion in the heavy top-quark limit is employed to derive the leading so far unknown contributions, ln^{5,4,3}(1-z), to the N^3LO coefficient function in the threshold expansion. Also using knowledge from Higgs-exchange DIS to estimate the remaining terms not vanishing for z = m_H^2/s^hat -> 1, these results are combined with the recently completed soft + virtual contributions to provide an uncertainty band for the complete N^3LO correction. For the 2008 MSTW parton distributions these N^3LO contributions increase the cross section at 14 TeV by (10 +- 2)% and (3 +- 2.5)% for the standard choices mu_R = m_H and mu_R = m_H/2 of the renormalization scale. The remaining uncertainty arising from the hard-scattering cross sections can be quantified as no more than 5%, which is smaller than that due to the strong coupling and the parton distributions.The single-logarithmic enhancement of the physical kernel for Higgs production by gluon-gluon fusion in the heavy top-quark limit is employed to derive the leading so far unknown contributions, ln$^{5, 4, 3}$(1−z), to the N$^{3}$LO coefficient function in the threshold expansion. Also using knowledge from Higgs-exchange DIS to estimate the remaining terms not vanishing for z = m$_{H}^{2}$ /ŝ → 1, these results are combined with the recently completed soft + virtual contributions to provide an uncertainty band for the complete N$^{3}$LO correction. For the 2008 MSTW parton distributions these N$^{3}$LO contributions increase the cross section at 14 TeV by (10 ±2)% and (3 ±2.5)% for the standard choices μ$_{R}$ = m$_{H}$ and μ$_{R}$ = m$_{H}$ /2 of the renormalization scale. The remaining uncertainty arising from the hard-scattering cross sections can be quantified as no more than 5%, which is smaller than that due to the strong coupling and the parton distributions.

HYPERDIRE is a project devoted to the creation of a set of Mathematica based programs for the differential reduction of hypergeometric functions. The current version includes two parts: the first one, FdFunction, for manipulations with Appell hypergeometric functions $F_D$ of $r$ variables; and the second one, FsFunction, for manipulations with Lauricella-Saran hypergeometric functions $F_S$ of three variables. Both functions are related with one-loop Feynman diagrams. The published version includes also Chapter 5 with two theorems about structure of coefficients of epsilon-expansion of the Horn-type hypergeometric functions. As illustration, the first three coefficients of epsilon-expansion for the Appell hypergeometric function FD of r-variables are explicitly evaluated., v3=v2: A new section 5 is added; published version

Nuclear physics / B 889, 351 - 400 (2014). doi:10.1016/j.nuclphysb.2014.10.016, We present the next-to-next-to-leading order (NNLO) contributions to the main splitting functions for the evolution of longitudinally polarized parton densities of hadrons in perturbative QCD. The quark-quark and gluon-quark splitting functions have been obtained by extending our previous all Mellin-N calculations to the structure function g_1 in electromagnetic deep-inelastic scattering (DIS). Their quark-gluon and gluon-gluon counterparts have been derived using third-order fixed-N calculations of structure functions in graviton-exchange DIS, relations to the unpolarized case and mathematical tools for systems of Diophantine equations. The NNLO corrections to the splitting functions are small outside the region of small momentum fractions x where they exhibit a large double-logarithmic enhancement, yet the corrections to the evolution of the parton densities can be unproblematic down to at least x about 10^{-4}.We present the next-to-next-to-leading order (NNLO) contributions to the main splitting functions for the evolution of longitudinally polarized parton densities of hadrons in perturbative QCD. The quark–quark and gluon–quark splitting functions have been obtained by extending our previous all Mellin- N calculations to the structure function g1 in electromagnetic deep-inelastic scattering (DIS). Their quark–gluon and gluon–gluon counterparts have been derived using third-order fixed- N calculations of structure functions in graviton-exchange DIS, relations to the unpolarized case and mathematical tools for systems of Diophantine equations. The NNLO corrections to the splitting functions are small outside the region of small momentum fractions x where they exhibit a large double-logarithmic enhancement, yet the corrections to the evolution of the parton densities can be unproblematic down to at least x≈10−4 ., Published by North-Holland Publ. Co., Amsterdam

Journal of high energy physics 1410(10), 176 (2014). doi:10.1007/JHEP10(2014)176, The single-logarithmic enhancement of the physical kernel for Higgs production by gluon-gluon fusion in the heavy top-quark limit is employed to derive the leading so far unknown contributions, ln^{5,4,3}(1-z), to the N^3LO coefficient function in the threshold expansion. Also using knowledge from Higgs-exchange DIS to estimate the remaining terms not vanishing for z = m_H^2/s^hat -> 1, these results are combined with the recently completed soft + virtual contributions to provide an uncertainty band for the complete N^3LO correction. For the 2008 MSTW parton distributions these N^3LO contributions increase the cross section at 14 TeV by (10 +- 2)% and (3 +- 2.5)% for the standard choices mu_R = m_H and mu_R = m_H/2 of the renormalization scale. The remaining uncertainty arising from the hard-scattering cross sections can be quantified as no more than 5%, which is smaller than that due to the strong coupling and the parton distributions.The single-logarithmic enhancement of the physical kernel for Higgs production by gluon-gluon fusion in the heavy top-quark limit is employed to derive the leading so far unknown contributions, ln$^{5, 4, 3}$(1−z), to the N$^{3}$LO coefficient function in the threshold expansion. Also using knowledge from Higgs-exchange DIS to estimate the remaining terms not vanishing for z = m$_{H}^{2}$ /ŝ → 1, these results are combined with the recently completed soft + virtual contributions to provide an uncertainty band for the complete N$^{3}$LO correction. For the 2008 MSTW parton distributions these N$^{3}$LO contributions increase the cross section at 14 TeV by (10 ±2)% and (3 ±2.5)% for the standard choices μ$_{R}$ = m$_{H}$ and μ$_{R}$ = m$_{H}$ /2 of the renormalization scale. The remaining uncertainty arising from the hard-scattering cross sections can be quantified as no more than 5%, which is smaller than that due to the strong coupling and the parton distributions., Published by Springer, Berlin

We study one-jet inclusive hadro-production and compute the QCD threshold corrections for large transverse momentum of the jet in the soft-gluon resummation formalism at next-to-leading logarithmic accuracy. We use the resummed result to generate approximate QCD corrections at next-to-next-to leading order, compare with results in the literature and present rapidity integrated distributions of the jet's transverse momentum for Tevatron and LHC. For the threshold approximation we investigate its kinematical range of validity as well as its dependence on the jet's cone size and kinematics.

We take a look at how the differential distributions for top-quark production are affected by changing to the running mass scheme. Specifically we consider the transverse momentum, rapidity and pair-invariant mass distributions at NLO for the top-quark mass in the MSbar scheme. It is found that, similar to the total cross section, the perturbative expansion converges faster and the scale dependence improves using the mass in the MSbar scheme as opposed to the on-shell scheme. We also update the analysis for the total cross section using the now available full NNLO contribution.

We report on progress in the determination of the unpolarised nucleon PDFs within the ABM global fit framework. The data used in the ABM analysis are updated including the charm-production and the high-Q2 neutral-current samples obtained at the HERA collider, as well as the LHC data on the differential Drell-Yan cross-sections. An updated set of the PDFs with improved experimental and theoretical accuracy at small x is presented. We find minimal impact of the t-quark production cross section measured at the Tevatron and the LHC on the gluon distribution and the value of the strong coupling constant \alpha_s determined from the ABM fit in the case of the t-quark running-mass definition. In particular, the value of \alpha_s(M_Z)=0.1133(8) is obtained from the variant of the ABM12 fit with the Tevatron and CMS t-quark production cross-section data included and the MSbar value of m_t(m_t)=162 GeV., Comment: Contribution to the proceedings of the XXI international workshop on Deep-Inelastic Scattering and Related Subjects (DIS2013), Marseille, 22-26 April 2013

We present heavy-flavor production in association with one jet in hadronic collisions matched to parton shower Monte Carlo predictions at next-to-leading order QCD with account of top-quark decays and spin correlations. We use the \POWHEGBOX{} for the interface to the parton shower programs \PYTHIA{} or \HERWIG{}. Phenomenological studies for the LHC and the Tevatron are presented with particular emphasis on the inclusion of spin-correlation effects in top decay and the impact of the parton shower on the top-quark charge asymmetries. As a novel application of the present calculation the measurement of the top-quark mass is discussed., Proc. of DIS 2012, 865 - 868; DESY-PROC-2012-02; ISSN 1435-8077

Weak vector boson fusion provides a unique channel to directly probe the mechanism of electroweak symmetry breaking at hadron colliders. We present a method that allows to calculate total cross sections to next-to-next-to-leading order (NNLO) in QCD for an arbitrary V* V* -> X process, the so-called structure function approach. By discussing the case of Higgs production in detail, we estimate several classes of previously neglected contributions and we argue that such method is accurate at a precision level well above the typical residual scale and PDF uncertainties at NNLO. Predictions for cross sections at the Tevatron and the LHC are presented for a variety of cases: the Standard Model Higgs (including anomalous couplings), neutral and charged scalars in extended Higgs sectors and (fermiophobic) vector resonance production. Further results can be easily obtained through the public use of the VBF@NNLO code., 56 pages