Search

We compute the next-to-leading-order (NLO) QCD corrections to the Higgs pT distribution in Higgs production in association with a jet via gluon fusion at the LHC, with exact dependence on the mass of the quark circulating in the heavy-quark loops. The NLO corrections are presented including the top-quark mass, and for the first time, the bottom-quark mass as well. Further, besides the on-shell mass scheme, we consider for the first time a running mass renormalisation scheme. The computation is based on amplitudes which are valid for arbitrary heavy-quark masses., Physics Letters B, 843, ISSN:0370-2693, ISSN:0031-9163, ISSN:1873-2445

In this proceedings we discuss a prescription to extract the QCD strong coupling constant at $N^{3}LO$ precision in perturbative QCD using a combination of ${\cal{O}}(��_{S}^{3})$ calculations in pQCD and estimations of the ${\cal{O}}(��_{S}^{4})$ corrections from the data. The method is applied to a set of event shape averages measured in experiments at the LEP, PETRA, PEP and TRISTAN colliders. In our analysis we account for hadronization effects with models from modern Monte Carlo event generators and analytic hadronization models. We conclude that the precision of the $��_{S}$ extraction cannot be improved significantly only with pQCD predictions of higher orders, and further progress in these studies requires a significant advances in the studies and modeling of hadronization process., Proceedings of 50th International Symposium on Multiparticle Dynamics

A summary of the main points of discussion raised during the talks and their follow-up questions, as well as in the round table of the last day of the αs(2019) workshop, is presented. The discussions not only focused on particular issues affecting each one of the individual αs extractions, but also on the current PDG categorization of αs measurements and on the methods used to average them into a single αs(mZ) value. Most of the listed points are open and sources of potential controversies, which we highlight here as one might expect that ongoing progress in the field will lead to their clarification and resolution.

The most precise determination of fundamental parameters of the Standard Model is very important. One such fundamental parameter is the strong coupling of QCD. Its importance can be gauged by taking a look at the various experiments and configurations where it was measured; for an up-to-date summary. The precise measurement of such a parameter is difficult for two reasons. First, high-quality data with small and well-controlled uncertainties are needed. Second, high-precision calculations are needed from the theory side, such that theoretical uncertainties are small as well., CERN Yellow Reports: Monographs, Vol. 3 (2020): Theory for the FCC-ee: Report on the 11th FCC-ee Workshop, Theory and Experiments, CERN, Geneva, 8–11 January 2019

We consider a method for determining the QCD strong coupling constant using fits of perturbative predictions for event shape averages to data collected at the LEP, PETRA, PEP and TRISTAN colliders. To obtain highest accuracy predictions we use a combination of perturbative ${\cal{O}}(��_{S}^{3})$ calculations and estimations of the ${\cal{O}}(��_{S}^{4})$ perturbative coefficients from data. We account for non-perturbative effects using modern Monte Carlo event generators and analytic hadronization models. The obtained results show that the total precision of the $��_{S}$ determination cannot be improved significantly with the higher order perturbative QCD corrections alone, but primarily requires a deeper understanding of the non-perturbative effects., 29 pages, 4 figures, 4 tables, journal version

The Future Circular Collider (FCC) at CERN, a proposed100km circular facility with several collidersin succession, culminates in a100TeV proton–proton collider. It offers a vast new domain of explorationin particle physics, with orders-of-magnitude advances in terms of precision, sensitivity, and energy.The implementation plan published in 2018 foresees, as a first step, an electroweak factory electron–positron collider. This high-luminosity facility, operating at centre-of-mass energies between 90 and365GeV, will study the heavy particles of the Standard Model (SM), Z, W, and Higgs bosons, andtop quarks with unprecedented accuracy. The physics programme offers great discovery potential:(i) through precision measurements, (ii) through sensitive searches for symmetry violations, forbidden,or extremely rare decays, and (iii) through the search for direct observation of new particles withextremely small couplings. The electroweak factorye+e−collider constitutes a real challenge to thetheory and to precision calculations, triggering the need for the development of new mathematicalmethods and software tools. A first workshop in 2018 focused on the first FCC-ee stage, the Tera-Z, andconfronted the theoretical status of precision Standard Model calculations on the Z boson resonanceto the experimental demands.The second workshop, in January 2019, extended the scope to the next stages, with the pro-duction of W bosons (FCC-ee-W), the Higgs boson (FCC-ee-H), and top quarks (FCC-ee-tt). In par-ticular, the theoretical precision in the determination of the crucial input parameters,αQED,αQCD,MW, andmt, at the level of FCC-ee requirements was thoroughly discussed. The requirements onStandard Model theory calculations were spelt out, so as to meet the demanding accuracy of theFCC-ee experimental potential. The discussion of innovative methods and tools for multiloop calcu-lations was deepened. Furthermore, phenomenological analyses beyond the Standard Model were dis-cussed, including effective theory approaches. The reports of 2018 and 2019 serve as white papers ofthe workshop results and subsequent developments. The FCC at CERN, a proposed 100-km circular facility with several colliders in succession, culminates with a 100 TeV proton-proton collider. It offers a vast new domain of exploration in particle physics, with orders of magnitude advances in terms of Precision, Sensitivity and Energy. The implementation plan foresees, as a first step, an Electroweak Factory electron-positron collider. This high luminosity facility, operating between 90 and 365 GeV centre-of-mass energy, will study the heavy particles of the Standard Model, Z, W, Higgs, and top with unprecedented accuracy. The Electroweak Factory $e^+e^-$ collider constitutes a real challenge to the theory and to precision calculations, triggering the need for the development of new mathematical methods and software tools. A first workshop in 2018 had focused on the first FCC-ee stage, the Tera-Z, and confronted the theoretical status of precision Standard Model calculations on the Z-boson resonance to the experimental demands. The second workshop in January 2019, which is reported here, extended the scope to the next stages, with the production of W-bosons (FCC-ee-W), the Higgs boson (FCC-ee-H) and top quarks (FCC-ee-tt). In particular, the theoretical precision in the determination of the crucial input parameters, alpha_QED, alpha_QCD, M_W, m_t at the level of FCC-ee requirements is thoroughly discussed. The requirements on Standard Model theory calculations were spelled out, so as to meet the demanding accuracy of the FCC-ee experimental potential. The discussion of innovative methods and tools for multi-loop calculations was deepened. Furthermore, phenomenological analyses beyond the Standard Model were discussed, in particular the effective theory approaches. The reports of 2018 and 2019 serve as white papers of the workshop results and subsequent developments.

We present a local subtraction scheme for computing next-to-next-to-leading order QCD corrections to the production of a massive quark-antiquark pair from a colourless initial state. The subtraction terms are built following the CoLoRFulNNLO method and refined in such a way that their integration gives rise to compact, fully analytic expressions. All ingredients necessary for a numerical implementation of our subtraction scheme are provided in detail. As an example, we calculate the fully differential decay rate of the Standard Model Higgs boson to massive bottom quarks at next-to-next-to-leading order accuracy in perturbative QCD., LaTeX, 32 pages, 4 figures

We present state-of-the-art extractions of the strong coupling based on N$^3$LO+NNLL accurate predictions for the two-jet rate in the Durham clustering algorithm at $e^+e^-$ collisions, as well as a simultaneous fit of the two- and three-jet rates taking into account correlations between the two observables. The fits are performed on a large range of data sets collected at LEP and PETRA colliders, with energies spanning from $35$ GeV to $207$ GeV. Owing to the high accuracy of the predictions used, the perturbative uncertainty is considerably smaller than that due to hadronization. Our best determination at the $Z$ mass is $��_s(M_Z) = 0.11881 \pm 0.00063(exp.) \pm 0.00101(hadr.) \pm 0.00045(ren.) \pm 0.00034(res.)$, which is in agreement with the latest world average and has a comparable total uncertainty., 36 pages,13 figures, 5 tables

The most precise determination of fundamental parameters of the Standard Model is very important. One such fundamental parameter is the strong coupling of QCD. Its importance can be gauged by taking a look at the various experiments and configurations where it was measured, for an up to date summary see Ref. [1]. The precise measurement of such a parameter is two-fold difficult. First, high quality data with small and well-controlled uncertainties are needed. Second, high precision calculations are needed from the theory side such that theoretical uncertainties are small as well. In a theoretical prediction based on calculation in perturbation theory the uncertainty has two main sources: the omission of higher-order terms which are estimated by the renormalization scale and the numerical stability of the integrations. While the dependence on unphysical scales can be, in principle, decreased by including more and more higher-order contributions in the prediction the numerical uncertainty can be intrinsic to the method used to obtain the theoretical prediction. Beside this, the way of comparison of experiment with theory is also affected by another uncertainty. While an experiment measures color-singlet objects, hadrons, the predictions are made in QCD for colorful ones, partons. The assumption of local partonhadron duality ensures a correspondence between these two up to non-perturbative effects. Non-perturbative effects are power corrections in nature going with some negative power of the collision energy. This means that for an accurate comparison 1) either these effects should be estimated and taken into account 2) or the experiment should have a high enough energy that these contributions become negligible compared to other effects 3) or an observable has to be chosen which is not sensitive to these effects.

We briefly review a subtraction scheme for computing radiative corrections to QCD jet cross sections that can be defined at any order in perturbation theory. Hereafter we discuss the computational methods used to evaluate analytically and numerically the integrated counterterms arising from such a subtraction scheme. Basically these methods the Mellin-Barnes (MB) representations technique together with the harmonic summation and the sector decomposition., Comment: Talk given at 13th International Workshop on Advanced Computing and Analysis Techniques in Physics Research, ACAT2010, February 22-27, 2010, Jaipur, India