1. Higgs Strahlung and W fusion
IRN Terascale
Marseille
December 14, 2017
Dirk Zerwas
LAL Orsay
Introduction
Higgs
Conclusions

2. Introduction SFitter origin: determine supersymmetric parameters
No one-to-one correlation of parameters to observables
correlations exp and theoretical errors
treatment of theory errors!
 global ansatz necessary
Lafaye, Plehn, Rauch, Zerwas
A GDR/IRN product which started in a GPS!
SFitter, Eur. Phys. J. C54, 617 (2008)
E. Turlay and SFitter, J.Phys. G38 (2011)
Search for parameter point, determine errors including treatment of error correlations:
Apply techniques developed for SUSY to the Higgs sector
SFitter and DuehrssenJHEP0908 (2009) 009, arXiv:  [hep-ph]
SFitter and Klute, Phys.Rev.Lett. 109 (2012)
SFitter and Klute, Europhys.Lett. 101 (2013) 51001
Englert, P. Zerwas and SFitter Phys.Lett. B707 (2012)
Bock, P. Zerwas and SFitter Phys.Lett. B694 (2010) 44-53
Competitor: Fittino (talk by Tobias)

3. Errors, minima search etc
RFit Scheme: Höcker, Lacker, Laplace, Lediberder
No information within theory errors: flat distribution
intuitively reasonable
central value not biased!
not necessarily “conservative” (and probability….)
Frequentist
Bayesian
Search for minima:
Markov Chains (or……)
Projections:
Frequentist
Bayesian

4. Higgs Factories Future colliders HL-LHC (from 2025+N to 2030+M)
Linear collider electron-positron: ILC (Japanese statement EONY)
CLIC (350GeV-3TeV)
Circular collider circumference 100km: pp ee
at CERN? (FCC)
in China? (CEPC)
HL-LHC:
Baseline: dominated by theory uncertainty
Electron-positron colliders:
small theory errors
inclusive Higgs production cross section measurement
Ldt != Ldt (polarization: 1.4 is 1)

5. The Delta/Kappa/HiggsEFT framework
Definition: ΔX deviation of XXH coupling from SM value:
gXXH= gX gXSM (1+ΔX)
Loop induced coupling:
gXXH=gX gXSM (1+ΔXSM+ΔX)
Different models:
without anomalous effective couplings
with anomalous effective couplings (new physics possible in a loop)
+ couple the 2nd and 3rd generation quarks

6. Measurement precision
T. Barklow, J. Brau, K. Fujii, J. Gao, J. List, N. Walker and K. Yokoya, arXiv: [hep-ex].
In a nutshell:
Inclusive measurement
Complete set of exclusive channels
W fusion cm dependent
M. Ruan, Nucl. Part. Phys. Proc , 857 (2016) [arXiv: [hep-ex]].
ILC/FCC-ee:
Close to √ Ldt (P sensitive)
FCC-ee/CEPC:
Mostly √ Ldt
Sometimes Ldt
Take FCC-ee properly scaled
Cross section errors:
ZH, WWH: 0.5%
ttH: 1%

7. Dreams of years past: concurrent running
SFitter, EPL 101 (2013) no.5, 51001
Dreams of years past: concurrent running
HL-LHC: dominated by theory error
ee: statistics
Combination more powerful

8. Higgs: the LHC + ee colliders
SFitter, Phys.Rev. D96 (2017) no.7,
Higgs: the LHC + ee colliders
ΔZ/W Δτ/b Δb/W
ΔZ Δt Δb Δτ
So….:
Theory errors do matter!
FCCee-base – FCCee ZH: W fusion has an impact
ILC-base – ILC-stage: removes ttH
W fusion at higher √s compensates 8x Ldt
FCC Δg: affected by theory error on Δc
Deduced total width: 2-7%

9. Removing constraint: generational coupling
And that means:
Most of sensitivity is charm (well tagged)
Large indirect effect on Δg

10. Total width or ZH plus ZZZ (low BR, works only for FCC)
ΔΓ: determination
Several contributions
Same precision
3x Γ: total width remains….

11. W=Z SMEFT like ΔW = ΔZ Mechanical effect: determinations improve
Total with improves (width determination through Z instead of W)
Different parameter set can lead to different dependencies (delta!=EFT)
(Disagree with arXiv: (List et al) that W fusion does not matter)

12. FCC-ee-350: adds precision
ILC-lumi: helps with Δt
ILC stage and FCC similar
Gupta, Rzehak, Wells: Phys.Rev. D86 (2012)

13. Conclusions Electron-positron colliders:
W fusion at high CM compensates lower integrated luminosity low CM
Future is bright if…….