Higgs Precision Measurements - at Future Collider Experiments

1. Higgs Precision Measurements - at Future Collider Experiments • Markus Klute (MIT) • Particle Physics Seminar • Boston University • November 7th, 2013

2. Roadmap Introduction Status of Higgs Searches at the LHC Prospects for the HL-LHC Potential future lepton collider projects Prospect for Higgs precision measurements

3. The Nobel Prize in Physics 2013

4. First three year of the LHC

5. First three year of the LHC Nevt = σ · Lint Higgs Discovery 2010 7 TeV 2011 7 TeV 2012 8 TeV

6. LHC Roadmap ATLAS CMS LS1 LS2 LS3 HL-LHC 13-14 TeV ➜ 8 TeV 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 1x1034cm-2s-1 5x1034cm-2s-1 0.7x1034cm-2s-1 2x1034cm-2s-1 • The Large Hadron Collider (LHC) at CERN, Switzerland

7. Higgs Footprint at the LHC mH = 125 GeV

8. Higgs Footprint at the LHC mH = 125 GeV

9. Overview of main SM Higgs channels ATLAS CMS

10. Status of Higgs Physics Program

11. Sensitive Higgs Channels Measure rate of Higgs events with different production and decay combinations. Cross-contamination of production and decay channels in categories.

12. Higgs Coupling Measurements Effective theory approach. Fit deviation from the SM expectation. Test varying degree of freedom.

13. Combining LHC Results used results available April ’13 20%

14. Significant progress in ttH channel in CMS • H ➜ γγ • H ➜ bb • H ➜ ττ • H ➜ ZZ • H ➜ WW HIG-13-015 HIG-13-019 HIG-13-020 Sensitivity approaching SM Higgs, directly to top Yukawa coupling μ = 2.5 ± 1.1

15. Invisible Higgs Decays in CMS • Studies in associated ZH and VBF production • sensitivity to Higgs decays to DM candidates • ZH • analyze shape of mT(Z,H) • BR(H➜inv.) < 75% (91% exp.) @ 95% CL • VBF • special VBF + MET trigger • BR(H➜inv.) < 69% (55% exp.) @ 95% CL • gluon fusion • re-interpretation or re-optimization of mono-jet analysis • ZH and VBF combination • BR(H➜inv.) < 54% (46% exp.) @ 95% CL • studies underway to include coupling fits with BRBSM included in total widths HIG-13-018 HIG-13-013

16. Status of Higgs Studies at CMS • Fantastic progress since discovery July 2012 • Observation in three bosonic channels • Evidence for fermion couplings • Precision mass measurement • Spin determined • Looks more and more like the SM Higgs boson • No evidence for non-SM decays • No evidence for additional Higgs boson • Publication of Run I legacy paper in progress • Summary of the Higgs boson properties • Mass • M = 125.7 ± 0.3 ± 0.3 GeV • 0.5% precision • Signal strength • μ = 0.80 ± 0.14 • Spin/CP • JCP = 0++ (SM-like Higgs boson) preferred • 0+- (2++) disfavored at a 3.3 (2.8)σ level Discovery opened a new era of Higgs measurements

17. Status of Higgs Studies at ATLAS • Fantastic progress since discovery July 2012 • Observation in three bosonic channels • Precision mass measurement • Spin determined • Looks more and more like the SM Higgs boson • No evidence for non-SM decays • No evidence for additional Higgs boson • Summary of the Higgs boson properties • Mass • M = 125.5 ± 0.2 ± 0.6 GeV • 0.5% precision • Signal strength • μ = 1.30 ± 0.20 • Spin/CP • JCP = 0++ (SM-like Higgs boson) preferred • 0+- (2++) disfavored Discovery opened a new era of Higgs measurements

18. Precision Higgs Measurement Imagine we do not find new (Higgs) particles in LHC data. How large are deviations to couplings from BSM? Deviations studied in numerous articles, e.g Gupta & Wells, arXiv:1206.3560. Conclusion, they find 1-10% deviations for vector bosons and fermion couplings. Most popular, MSSM Higgs sector in decoupling limit (large mA)

19. LHC Upgrade Stages LHC Reach 1034cm-2s-1 by LS2, double by LS3 and integrate 300fb-1 by 2022 <PU> = 50 HL-LHC Lumi-level 5x 1034cm-2s-1 and integrate 3000fb-1after LS3 <PU> = 140

20. Experimental Goals Physics: precision measurements at the EWK scale while searching for new particles up to the multi-TeV scale. Detector: extend and enhance detector capability, especially in the forward region where effects of PU and radiation are most severe Pile-up: achieve robustness with up to 6x higher pile-up Trigger: maintain low thresholds to support physics goals Requires significant upgrades for ATLAS and CMS

21. Phase II Upgrade Plans for ATLAS and CMS • Challenge: longevity due to radiation damage, pile-up • Extensive redesign of trigger system • Replacement of tracking detectors • Calorimeterupgrades: electronics and new forward detectors • Muon detector upgrades • Software and computing upgrades to cope with large data volume ATLAS CMS Phase II tracker proposal

22. HL-LHC as Higgs Factory number of produced events

23. Projections in HEP

24. Projections in HEP 19 MeV 1.1 GeV Large statistics allows to: - be selective, use your best events. - calibrate data in situ. Theory calculations are work in progress, e.g. Annastasio et al working on NNNLO, PDF constrains from LHC data. Assumptions on systematic uncertainties Scenario 1: no change Scenario 2: Δ theory / 2, rest ∝ 1/√L

25. Higgs Boson Coupling Modifier Fits κg, κγ, κZγ: loop diagrams ➜ allow potential new physics κW, κZ: vector bosons κt, κb: up- and down-type quarks κτ, κμ: charged leptons total width from sum of partial widths alternatively: assumption here κW, κZ < 1 CMS Projection coupling precision 2-10 % factor of ~2 improvement from HL-LHC

26. Theoretical Uncertainties To test the importance of theoretical uncertainties we show the effect of removing them. Theoretical uncertainties dominated by QCD scale and PDF uncertainties. Uncertainty on BR become relevant at few % precision. Δ theory = 0, rest unchanged

27. Comparison of ATLAS and CMS • Uncertainty on signal strength • Ranges [x,y] are not directly comparable • ATLAS • [no theory uncertainty, Scenario 1] • CMS • [Scenario 2, Scenario 1] • Overall reasonable agreement, but • ATLAS does not include H ➜ bb mode • CMS outperforms ATLAS H ➜ ττ mode • Large differences in H ➜ Zγ mode

28. Comparison with ATLAS and CMS • Large differences in fits for coupling strength • ATLAS connects Κτ with Κb to overcome H ➜ bb mode, but H ➜ ττ then becomes overall limitation in constraining total width.

29. Comparison with ATLAS and CMS CMS [3,5] [3,3] [4,5] [3,5] [4,5] [3,4] [8,8] [12,12] [4,8] [no theory uncertainty, Scenario 1] Good agreement in ratio measurements

30. Future Lepton Collider Projects live on different time-scales and are at different state of readiness ILC CLIC Future Circular Collider (FCC) MAP

31. Higgs Couplings at Lepton Collider • Higgs-strahlung is main production process • HZZ coupling observed at the LHC • Vector boson fusion give small contribution at 250 GeV • Cross section plateau at 240-280 GeV • Reasonable background level

32. Higgs Couplings at Lepton Collider • Higgs-strahlung with Z → ll allows decay modeindependent measurement • performed on OPAL data (Eur.Phys.J.C27:311-329,2003) • benchmark for linear collider studies • sensitive invisible Higgs decays • Coupling • model independent extraction of gZZH from σZH in fit to recoil mass spectrum • other Higgs couplings extracted from σHZ x BR measurements and gZZH • total width extracted from combination of initial and final state measurement • Mass • can also be measure model dependent • Spin • using √s - scan • CP properties • using angular distributions TESLA physics TDR

33. Comparing Future Collider Option Projects live on different time-scales and are at different state of readiness

34. Comparing Future Collider Option

35. Comparing Future Collider Option

36. Comparing Future Collider Option

37. Conclusion Higgs discovery opened a new field of study. Current measurements consistent with SM Higgs hypothesis. Future hadron and lepton collider experiments have potential for precision Higgs physics. Couplings with 2-10% precision from HL-LHC. % level precision from lepton collider. Improvements on theoretical uncertainties needed. Higgs program does not stop with coupling measurement. Rare decays, spin and parity studies and further BSM Higgs searches are of similar importance.