Theory for the FCC-ee : Report on the 11th FCC-ee Workshop

The Future Circular Collider (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

Precise determination of α

We present a determination of the strong coupling constant αS( $m_{Z^0 }$ ) using a global fit of theory predictions in next-to-next-next-leading-order (NNLO) combined with resummed predictions at the next-to-next-leading-log level (NNLL) [

Precise determination of αS( m Z 0 mZ0 m_{Z^0 } ) from a global fit of energy-energy correlations to NNLO+NNLL predictions

We present a determination of the strong coupling constant αS( m Z 0 $m_{Z^0 }$ ) using a global fit of theory predictions in next-to-next-next-leading-order (NNLO) combined with resummed predictions at the next-to-next-leading-log level (NNLL) [1]. The predictions are compared to distributions of energy-energy correlations measured in e+e−annihilation to hadronic final states by experiments at the e+e−colliders LEP, PETRA, TRISTAN and PEP. The predictions are corrected for hadronisation effects using the modern generator programs Sherpa 2.2.4 and Herwig 7.1.1

αs\alpha_s(2019): Precision measurements of the QCD coupling

This document collects a written summary of all contributions presented at the workshop '$\alpha_s$(2019): Precision measurements of the strong coupling' held at ECT* (Trento) in Feb. 11--15, 2019. The workshop explored in depth the latest developments on the determination of the QCD coupling $\alpha_s$ from the key categories where high precision measurements are available: (i) lattice QCD, (ii) hadronic $\tau$ decays, (iii) deep-inelastic scattering and parton distribution functions, (iv) event shapes, jet cross sections, and other hadronic final-states in $e^+e^-$ collisions, (v) Z boson and W boson hadronic decays, and (vi) hadronic final states in p-p collisions. The status of the current theoretical and experimental uncertainties associated to each extraction method, and future perspectives were thoroughly reviewed. Novel $\alpha_s$ determination approaches were discussed, as well as the combination method used to obtain a world-average value of the QCD coupling at the Z mass pole

Theory for the FCC-ee: Report on the 11th FCC-ee Workshop Theory and Experiments

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.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