Summary of precision QCD issues at FCC-ee

Transcription

1 Summary of precision QCD issues at FCC-ee th 11 FCC-ee workshop: Theory & Experiments th CERN, 11 Jan David d'enterria CERN 1/25

2 Precision QCD & FCC-ee physics FCC-ee uniquely small EXP uncertainties is key to NP > 50TeV limits. Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables. 2/25

3 Precision QCD theory & FCC-ee physics FCC-ee uniquely small EXP uncertainties is key to NP > 50TeV limits. Precise QCD theory (small intrinsic uncertainty) is required in SM stress tests & BSM searches for most FCC-ee observables. New analytical+numerical concepts & tools needed to compute (faster) H.O. EWK+QCD multi-loop,-legs,-scales corrections for heavy particles (Z,W,H,t): [S. Weinzierl] [G. Rodrigo] [R. Pittau] [K. Papadopoulos] [T. Riemann] [B. Page] [J. Usovitsch] [S. Jones] [See J. Gluza next] 3/25

4 Precision QCD coupling & FCC-ee physics FCC-ee uniquely small EXP uncertainties is key to NP > 50TeV limits. Precise QCD coupling (small parametric uncertainty) is required in SM stress tests & BSM searches for most FCC-ee observables: [C. Grojean] 4/25

5 Precision QCD & FCC-ee physics FCC-ee uniquely small EXP uncertainties is key to NP > 50TeV limits. Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (1) pqcd Higher-Order (H.O.) theoretical predictions of EWPO at Z pole. (2) pqcd H.O. & coupling impact on Higgs decay widths (H gg,...) (3) pqcd H.O. theoretical predictions of WW cross sections. (4) pqcd H.O. & coupling & non-pqcd impact on top properties (mt, t, t). (5) pqcd H.O. & coupling impact on SM parameters extractions (mc,b, ) (6) pqcd H.O. theoretical predictions of flavour physics. (7) pqcd H.O. & coupling impact on (N)MSSM Higgs. Unique permille-precision extractions of the QCD coupling at FCC-ee. 5/25

6 Precision QCD & FCC-ee Z boson physics Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (1) pqcd H.O. theoretical predictions of EWPO at Z pole. [J. Gluza] 6/25

7 Precision QCD & FCC-ee Higgs physics Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (2) pqcd H.O. & coupling impact on Higgs decay widths (H gg,...) [M. Spira] [S. Heinemeyer] 7/25

8 Precision QCD theory & FCC-ee W boson physics Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (3) pqcd H.O. theoretical predictions of WW cross sections. [C. Schwinn] 8/25

9 Precision QCD theory & FCC-ee top physics Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (4) pqcd H.O. & coupling & non-pqcd impact on top properties (mt, t, t): [P. Janot] 9/25

10 Precision QCD theory & FCC-ee top physics Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (4) pqcd H.O. & coupling & non-pqcd impact on top x-section & mass: Parametric s unc.: -10%, +2% [A. Maier] [M. Steinhauser] [D. Samnitz] 10/25

11 Precision QCD theory & FCC-ee QED extraction Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (5) pqcd H.O. & coupling impact on QED extraction: 11/25 [F. Jegerlehner]

12 Precision QCD theory & FCC-ee mc,b extraction Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (5) pqcd H.O. & coupling impact on charm, bottom mass extractions: [M. Steinhauser] 12/25

13 Precision QCD theory & FCC-ee flavour physics Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (6) pqcd H.O. theoretical predictions of flavour physics: [R. Szafron] 13/25

14 Precision QCD & FCC-ee BSM Higgs physics Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (7) pqcd H.O. & coupling impact on (N)MSSM Higgs: [S. Heinemeyer] 14/25

15 QCD coupling s Determines strength of the strong interaction between quarks & gluons. Single free parameter in QCD in the mq 0 limit. Determined at a ref. scale (Q=mZ), decreases as s~ln(q2/ 2),-1 ~0.2 GeV Uncert.~2.5% Uncert.~6% Uncert.~0.9% 2017 Least precisely known of all interaction couplings! ~10-10 GF 10-7 G~10-5 s~ /25

16 s determination at FCC-ee Determined today by comparing 6 experimental observables to pqcd NNLO,N3LO predictions, plus global average at the Z pole scale: [Bethke/Dissertori/Salam] (1) lattice (2) decays (3) PDFs (4) e+e- jets (shapes, rates) (5) W, Z decays (6) pp ttbar 16/25

17 s from hadronic -lepton decays Computed at N3LO: Experimentally: R,exp = ± (±0.23%) Various pqcd approaches (FOPT vs CIPT) & treatment of non-pqcd corrections (note: ( /m 2 ~2%), yield different results. Uncertainty slightly increased: 2013 (±1.3%) 2017 (±1.5%) (±1.5%) Future prospects: Better TH understanding of FOPT vs CIPT differences. Better EXP spectral functions needed (high stats & better precision): B-factories (BELLE-II?) FCC-ee: High-stats, O(1011), from Z s/ s < 1% 17/25

18 s from hadronic Z decays (today) Computed at N3LO: LEP: Extraction from fits to 3 Z-peak pseudo-observables: Z = ± GeV (±0.1%) After Higgs discovery, s can be also directly determined from full fit of SM: s (Mz) = ± (±2.5%) 18/25

19 s from hadronic Z decays (FCC-ee) Computed at N3LO: FCC-ee: Extraction from fits to 3 Z-peak pseudo-observables. FCC-ee Huge Z stats ( 105 LEP) will lead to: s/ s < 0.2% Full SM-fit extraction: Parallel reduction of parametric (sin2 eff,mw,mtop) TH uncertainties. 19/25

20 s from hadronic W decays [D.d'E, M.Srebre, PLB763 (2016) 465] Width (BR) known at N3LO (NNLO). Small sensitivity to s (beyond Born) [EWK: -0.35%] Vi,j % s(1-4) % s % TH improvements: finite quark-mass effects included (LO), updated PDG parameters, careful evaluation of parametric (Vi,j, mw) & theoretical uncert. Calculation dominated by ±1.5% parametric (mostly Vcs) uncertainty: W(MeV) = ± 22.40(par) ± 0.04(th) ± 0.96(par) ± 0.04(th) (exp. CKM) (CKM=1) BRW = W/ tot = ± (par) ± (th) (exp. CKM) ± (par) ± (th) (CKM=1) TH uncertainty (missing s5 terms, non-pqcd ( QCD/mW)4 power corrs., finite quark masses beyond LO, CKM matrix renorm. scheme): ±0.03% 20/25

21 s from hadronic W decays (today FCC-ee) Computed at N2,3LO: LEP: W = 1405±29 MeV (±2%), BRW = ± (±0.4%) Extraction with large exp. & parametric s (Mz) = ± (CKM Vcs) uncertainties today: (±35%) [D.d'E, M.Srebre, PLB763(2016)465] FCC-ee: Huge W stats ( 104 LEP) will lead to: s/ s < 0.3% TH (param.) uncertainty: Vcs to be significantly improved (10-4) 21/25

22 s from e+e- event shapes & jet rates Computed at N2,3LO+N(2)LL accuracy. Experimentally (LEP): Thrust, C-parameter, jet shapes 3-jet x-sections Results sensitive to non-pqcd (hadronization) accounted for via MCs or analytically: (±2.9%) [T. Gehrmann] 22/25

23 s from e+e- event shapes & jet rates (future) Computed at N2,3LO+N(2)LL accuracy. Experimentally (LEP): Thrust, C-parameter, jet shapes 3-jet x-sections Results sensitive to non-pqcd (hadronization) accounted for Modern jet substructure techniques: via MCs or analytically: Soft drop /grooming to reduce non-pqcd corrections for evt shapes: [A. Kardos] [T. Gehrmann] s/ s <1% New data: Lower- s (Belle-II) for evt shapes, higher- s (FCC-ee) for rates TH: Improved hadronization for shapes, (N2,3LL) resummation for rates. Future: 23/25

24 s from e+e- energy-energy correlations (new) [A. Kardos] 24/25

25 Summary FCC-ee uniquely small EXP uncertainties is key to NP > 50TeV limits. Precise QCD theory & QCD coupling are required in SM stress tests & BSM searches for most FCC-ee observables: (1) pqcd Higher-Order (H.O.) theoretical predictions of EWPO at Z pole. (2) pqcd H.O. & coupling impact on Higgs decay widths (H gg,...) (3) pqcd H.O. theoretical predictions of WW cross sections. (4) pqcd H.O. & coupling & non-pqcd impact on top properties (mt, t, t). (5) pqcd H.O. & coupling impact on SM parameters extractions (mc,b, ) (6) pqcd H.O. theoretical predictions of flavour physics. (7) pqcd H.O. & coupling impact on (N)MSSM Higgs. Unique permille-precision extraction of the QCD coupling at FCC-ee: 25/25

26 Backup slides 26/25

27 Summary: s at FCC-ee World-average QCD coupling at N2,3LO: Determined today from 6 observables with ~1% uncertainty (least well-known coupling). Impacts all LHC (& FCC-hh) QCD x-sections & decays. Role beyond SM: GUT, EWK vacuum stability New colored sectors? ~0.1% uncertainty, combining Z,W, hadronic decays (plus F2 (x,q2) & FFs fits) ONLY possible with machine like FCC-ee: New extractions/updates: PDF fits, e-p jets, full pp ttbar Reduction of hadronization & resummation uncertainties: New TH developments needed New precise e+e- data needed Other extraction methods proposed: TH work towards NNLO accuracy. 27/25

28 Importance of the QCD coupling s Impacts all QCD x-sections & decays (H), precision top & parametric EWPO: Impacts physics approaching Planck scale: EW vacuum stability, GUT (New coloured sectors?) 28/25

29 Other s extractions (not yet in world average) There exist at least 8 other classes of observables, computed today at lower accuracy (NLO, NNLO*), that could be used to extract as. Three of them to be exploited at FCC-ee: decay factor (NNLO*) soft parton FFs (NNLO*) F2 (x,q2) decays (NLO) (NLO) ep jets (NNLO) hard W decays (NNLO) parton pp jet observ. (NLO) FFs (NLO) 29/25

30 s from QCD structure function Computed at NNLO: Poor F2 (x,q2) experimental measurements: Extraction (NLO) with large exp. uncertainties today: s (Mz) = ± (±4.5%) [M.Klasen et al. PRL89 (2002)122004] Future prospects: Fit with NNLO F2 evolution (ongoing) Better e+e- data badly needed: Belle-II? Dedicated studies at ILC exist: Huge (EPA) stats at FCC-ee will lead to: s/ s < 1% 30/25 [R.Nisius, arxiv: ]

31 s from parton-to-hadron FFs Soft Fragmentation Functions (NNLO*+NNLL): Hard Frag. Functions (NLO): Combined fit of energy evolution of HBP moments: s (NNLO)=0.1199± (±3.6%) s (NNLO*+NNLL)=0.1205± (±2%) [AKK, B.Kniehl et al., NPB 803(2008)42] s (NLO)=0.1176±0.0055± (±4.7%) [D.d'E., R.Perez-Ramos, arxiv: ] Future prospects: Full-NNLO fit for FF (& moments) evolution. FCC-ee: Huge hadron stats. up to 2 LEP Ejet 31/25 s/ s < 1%