Tim Barklow (SLAC) Nov 05, 2015 LCWS2015, Whistler, Canada Review - PowerPoint PPT Presentation

Tim Barklow (SLAC) Nov 05, 2015 LCWS2015, Whistler, Canada

 Review of ILC Higgs Coupling Precisions  Experimental and Theoretical Systematic Errors  Limits on BSM decays and the Ultimate Higgs Coupling Precision 2 2

− → σ + = ILC Measurement of ( e e ZH ) s 250 GeV Higgs Recoil Measurement of Higgs Mass and Higgstrahlung Cross Section → + − µ µ + − Z e e , → H anything, incl invisible − ∆ = ∆ σ σ 1 ILC: M .025 GeV, / =1.4% for L= 500 fb H HZ HZ ∆ = ∆ σ σ − 1 M .013 GeV, / =0.7% for L=2000 fb H HZ HZ σ  2 g HZ HZZ − ⇒ ∆ = 1 g / g 0.7% (0.35%) for L=500 (2000) fb HZZ HZZ [from leptonic recoil alone] 3 3

+ − σ × → = ILC BR measurements using e e ZH s 250 GeV All Z decays are used for measurement σ × → → νν of BR. These include Z qq and Z . Flavor tagging very important for distinguishing different decay modes 4 4

− → + νν = e e ZH , H s 350 GeV σ =  All of the BR Higgstrahlung studies that were done at s 250 GeV can also be done at = σ σ  s 350 GeV . Precisions for BR are comparable, as is the precision for (ZH) → once Z q q decays are included. = WW fusion production of the Higgs at s 350 GeV provides a much better measurement = of g compared to s 250 GeV. This gives a much improved estimate of the HWW Γ total Higgs width which in turn significan tly improves the coupling errors obtained H σ =  from BR measurements made at s 250 GeV. WW fusion also provides additional σ  BR measurements. = The recoil Higgs mass measurement is significantly worse at 350 GeV with respect to s = s 250 GeV. However, there is hope that direct calorimeter Higgs mass measurements + − → νν using e e H will recover the precision (two ongoing studies were presented at this conferen ce) 5 5

− → + νν = e e ZH , H s 350 GeV 6 6

− → + νν = e e ZH , H, t t H, ZHH s 500 GeV = The coupling can also be measured well at 500 GeV through fusion g s WW HWW σ + − → νν × → production of the Higgs. Also the measurement of ( e e H ) BR H ( X ) → can be made for many Higgs decay modes H X . + − → ∆ = Through e e ttH the top Yukawa coupling can be measured to y / y 18% t t − = = 1 with 500 fb at s 500 GeV. With same luminosity at s 550 GeV the precision ∆ = is y / y 7.2%. t t = The ZHH channel is open at s 500 GeV. The Hig gs self coupling can be measured − 1 to 27% with 4 ab assuming the true value is the SM value. 7 7

Summary of ILC Higgs Measureme nt Precision s From "500 GeV ILC Operating Scenarios" arX iv :1506.0 7830 8 8

H-20: Preferred 20 year Running Scenario 9 9

ILC Higgs Coupling Precision vs Time 10 10

ILC Higgs Coupling Precisions H20 @ 8yrs H20 @ 20yrs 11 11

Higgs Physics Systematic Error s Given that the statistical errors of many of the Higgs cross section σ  and BR reach the several per-mil level for the full H20 program, sys tematic errors must typical ly be 0.1% or less. The following systematic errors have been considered:  Flavor Tagging  Luminosity  Polarization  Model Independence of ZH Recoil Measurements  Theory Error 12 12

Higgs Physics Systematic Errors Luminosity, Polarization, & Flavor Tagging Systematic Errors Assumed in 2013 Snowmass Higgs White Paper: ∆ µ R(sensors) < 30 m polarization obtained from polarimeters upstream and downstream of IP + + − → + − physics processes such as e e W W + − → → + − b-tag efficiency errors obtained from a quick studying using e e ZZ l l bb as a control sample; could be improved with additional control sample processes 13 13

Higgs Physi cs System at i c Errors Model Indep endence of ZH Recoil M ea s ur ements In order to use the hadronic ZH recoil measurement in our Higgs analyses we have to quantify the penalty σ → + associated with the fact that ( ZH q q X ) is "almost model independent". By how much must we ∆ σ → + bl ow up ( ZH q q X ) to account for the fact that the efficiencies differ by as much as 7%? 14 14

Model Independence of ZH Recoil Measurements It is not sufficient to vary the SM Higgs branching ratios to estimate this systematic error. The problem is the BSM decays; they cannot be accounted for in this way. To handle the BSM decays we have used an approach where we σ  use all of our BR measurements for SM Higgs decays to obtain σ → + an estimate of the average signal efficiency for ( ZH q q X ). It is σ  then straightforward to propagate the B R errors, as well as the i systematic errors on the individual decay mode efficiencies for the σ → + σ → + ( ZH q q X ) selection, to the error on ( ZH q q X ). 15 15

Model Independence of ZH Recoil Measurements Let Ψ ≡ σ → + ( ZH q q X ) Ω = σ → + Number of signal + background events in ( ZH q q X ) analysis Β = σ → + Predicted number of background events in ( ZH q q X ) analysis Ξ σ → + = Average efficiency for signal events to pass ( ZH q q X ) analysis = L luminosity Ω − Β 1 ∑ ∑ Ψ = = ψ ξ ψ = where Ξ Ξ i i i L i i ψ = σ  ( ZH BR ) i i ξ = σ → + e fficiency for events from Higgs decay i to pass ( ZH q q X ) analysis i ∑ ψ ξ i i Ξ = i ∑ ψ i i 16 16

Model Independence of ZH Recoil Measurements ω − β ψ = i i η i L i ω = σ  Number of signal + background events in ( ZH BR ) analysis i i β = σ  Predicted number of background events in ( ZH BR ) analysis i i η σ  = efficiency for Higgs decay i to pass BR analysis i i Κ = number of signal + background events common to had Z recoil i σ  and BR analyses i Ε = number of signal + background events unique to had Z recoil analysis ε σ  = number of si gnal + background events events unique to BR analysis i i + Β S ∑ Ω = Ε + Κ ≡ Ω Β Τ ≡ S - i S i + β s ω = Κ + ε ≡ ω − β τ ≡ i i s i i i i i i i s i Κ λ ≡ ≡ σ ≡ δ ≡ ξ − Ξ i N L r BR ω i ZH i i i i i 2   ∆Ψ   2 ( ) N ∑   Τ + τ δ − λ η δ + ∆ ξ This is our result for the error on 2  2 2 2 2    = 1 r 2   Ψ Ω i i i i i i i σ → +     ( ZH q q X ) i 17 17

Model Independence of ZH Recoil Measurements 2     ∆ σ → + 2 2 ( ZH q q X ) N 1 N ∑ ∑ Τ +  τ δ + ∆ ξ   τ δ + ∆ ξ  2 2 2 2 2 2 2 2 2   = 1 r i.e. sys err = r       σ → + Ω Ω i i i i i i i i   ( ZH q q X )   2 i i = − 1 Assume s 350 GeV and L=5 00 fb + β ∆ σ • s BR ( SM ) = σ = = = − τ = = i i i N L 45383 r BR (1 BR ) BR SM ( ) ( S M ) σ • ZH i i BSM i i BR ( SM ) s i i + Β S Τ = = Ω = ξ Assume 0.014 =S+B 17738 and ( SM ) given in the table four pages back. i S We assume that the vis+invis efficiency values in the table four pages back cover all possib le BSM decays since they cover all SM decays from completely invisible to fully hadronic multi-jet decays. Assuming no knowledge of the properties of the BSM decays we can then set ξ = ξ + ξ = + = 0.5 * [ (max) (min)] 0.5 * [0.258 0.188] 0.22 + + BSM vis i nvis vis invis ∆ ξ ξ − ξ = = 0.5 * [ (max) (min)] .035 + + BSM vis invis vis invis 18 18