BSM search using invisible Higgs decay at the ILC Yu Kato, The - PowerPoint PPT Presentation

BSM search using invisible Higgs decay at the ILC Yu Kato, The University of Tokyo ILC Summer Camp July 24, 2017

q X q Z Z ν ν X ν q q ν Motivation l In SM, Higgs decays invisibly through LHC CMS result (95% CL) H → ZZ ∗ → 4𝜉 (BR(H → 𝑗𝑜𝑤.)~0.1%) observed (expected) l If BR(H → 𝑗𝑜𝑤.) exceeds SM prediction , 24% (23%) It signifies new physics beyond SM (BSM) l In this study, we estimate upper limit of BR(H → 𝑗𝑜𝑤.) Dark Matter… SUSY… l Compare between left & right polarization at the ILC invisible BSM invisible 𝐶𝑆 H → ZZ ∗ → 4𝜉 ~0.1% 𝐶𝑆 H → XX ~? ? ? % 8 ∝ 𝜏 ;< ・ 𝐶𝑆 H → 𝑗𝑜𝑤𝑗𝑡𝑗𝑐𝑚𝑓 𝑂 visible visible Ø A. Ishikawa (Tohoku Univ.), ”Search for Invisible Higgs Decays at the ILC” LCWS2014@Belgrade Ø M. A. Thomson (Univ. of Cambridge), arXiv: 1509.02853 (2015) BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 2

Setting & Flow of Analysis l Setting ◦ Generator: WHIZARD 1.95 ◦ Samples: DBD sample + Dirac sample ( e B e C → qqH, H → ZZ ∗ → 4𝜉 ) ◦ Detector: ILD full simulation ◦ E cm = 250 GeV, ∫ 𝑀𝑒𝑢 = 250 fb -1 , 𝑄 J K , 𝑄 J L = −0.8, +0.3 , (+0.8, −0.3) l Flow of analysis ◦ Isolated lepton tagging → veto ◦ Jet clustering ◦ forced 2-jet reconstruction using LCFIPlus ◦ Event selection (next page) ◦ assume BR(H→invisible)=10% ◦ Fit & Toy Monte Carlo to set upper limit BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 3

Event Selection 1. isolated lepton veto 2. loose restriction [ transverse di-jet momentum, di-jet invariant mass, recoil mass from di-jet] 3. number of PFOs and charged tracks: N pfo , N track 4. di-jet (Z) pt: Pt Z 5. di-jet mass: M Z 6. di-jet polar angle: θ Z 7. recoil mass: M recoil 8. multi-variate analysis: Boosted Decision Tree(BDT) method BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 4

Preliminary Recoil Mass Plots [Ecm = 250 GeV, 250 fb -1 ,BR(H->inv.)=10%] Left Right significance: 15.5 significance: 19.7 efficiency: 63.5% efficiency: 65.9% No. Cut No. Cut 1 Isolated lepton veto 5 80 < Mz < 100 MVA input variables 2 Loose Cut (Ptz,Mz,Mrecoil) 6 |cosθZ|<0.9 mz cosj1 3 Npfo>15 & Ntrack>6 & Ntrackji>1 7 100 < Mrecoil < 160 cosz cosj2 4 20 < Ptz < 80 8 BDT cut TMVA v-4.2.0 BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 5

How to set UL l Template Assume BR(H→invisible)=[1,2,…,10]% -> Event selection Ø Get # of events (N S+B ) in window range (Mrecoil ∈ [120,140] GeV) Ø Generate Poisson distribution of N S+B -> Get 95% CL limit (N UL ) Ø Repeat for each BR(H→invisible)=[1,2,…,10]% -> Get calibration line between N UL and UL Ø l Toy MC Ø Fit template bkg -> Generate pseudo experiment by fluctuated bkg function Get # of events (N S+B ) in window range (Mrecoil ∈ [120,140] GeV) Ø Translate N S+B into UL of BR(H→invisible) using calibration line Ø Repeat 10000 times -> Obtain UL distribution Ø UL N UL N S+B N UL UL[%] BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 6

Preliminary Statistical fluctuation of Upper Limit Left polarization Right polarization 250 fb -1 250 fb -1 250 fb -1 UL=0.95 ± 0.45% UL=0.53 ± 0.31% H20 (800 fb -1 ) 800 fb -1 800 fb -1 UL=0.55 ± 0.25% UL=0.25 ± 0.17% BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 7

Preliminary Left Right Left Right 250 fb -1 H20 (800 fb -1 ) BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 8

Summary Use measurement of BR( H → 𝑗𝑜𝑤. ) as a means for indirect BSM search l Motivation ◦ set upper limit (UL) on BR(H → 𝑗𝑜𝑤.) ◦ develop analysis method to achieve high sensitivity ◦ compare between alternative polarization ◦ study is based on full ILD detector simulation, at E ST = 250 GeV, assuming 250 fb CW l Status ◦ optimized data selection methods Left polarization Right polarization significance [250 fb CW ] 15.5 19.7 ◦ set UL using toy MC for both left and right scenario UL of BR [%] (95%CL) Left polarization Right polarization 0.95 ± 0.45 (1σ) 0.53 ± 0.31 (1σ) 250 fb CW 0.55 ± 0.25 (1σ) 0.25 ± 0.17 (1σ) H20 scenario (800 fb CW ) Previous study(250 fb CW ) 0.95 0.69 BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 9

� Plan l Evaluate jet energy resolution and scale of Detector l Construct error matrix → kinematic fit sample: 2f_z_h 𝑡 = 250 GeV ∫ 𝑀𝑒𝑢 = 250 fb -1 BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 10

Back Up BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 11

� Recoil Mass Method l We can measure Higgs without directly looking at it → model independent − 𝐹 a _ − 𝑞 _ ⃗ a _ 𝑁 ]J^ = 𝑡 l Higgs-strahlung cross section can be obtained using leptonic decay of Z 𝑂 8 𝜏 ;< = 𝐶𝑆 Z → 𝑚 B 𝑚 C ε 8 𝑀 ε 8 : signal efficiency, N w : # of signal, 𝑀 : integrated luminosity J.Yan(KEK) et al. Phys. Rev. D94 113002 (arXiv:1601.07524 ) (2016) l For BSM search, this study uses hadronic channel 𝑎 → 𝑟𝑟 and 𝐹 ^{ = 250 GeV BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 12

Hadronic Channel Analysis Cut table [Ecm=250GeV,250fb -1 ,Left] 数式を⼊⼒します。 BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 13

Hadronic Channel Analysis Cut table [Ecm=250GeV,250fb -1 ,Right] BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 14

Preliminary signal: GPET (Gaussian + Exponential) Fit Signal & Background : 5 th order polynomial bkg Left Right BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 15

Preliminary Toy Monte Carlo to Set Upper Limit Left polarization Right polarization UL=1.03% (95%CL) UL=0.69% (95%CL) bkg : shape fixed, yields floated Ø ∫ 𝑀𝑒𝑢 = 250 fb -1 Ø bkg yields floated → 10000 times pseudo experiment Ø not include SM Higgs to invisible decay BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 16

Preliminary Toy Monte Carlo to Set Upper Limit Left polarization Right polarization 250 fb -1 250 fb -1 250 fb -1 UL=1.03% (95%CL) UL=0.69% (95%CL) H20 (800 fb -1 ) 800 fb -1 800 fb -1 UL=0.58% (95%CL) UL=0.39% (95%CL) BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 17

Preliminary Toy Monte Carlo to set upper limit Left Right UL=0.78% (95%CL) UL=0.52% (95%CL) bkg : shape & yields fixed Ø ∫ 𝑀𝑒𝑢 = 250 fb -1 Ø bkg fixed → 10000 times pseudo experiment Ø not include SM Higgs to invisible decay BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 18

Previous Study A. Ishikawa (Tohoku Unv.), ”Search for Invisible Higgs Decays at the ILC” LCWS2014@Belgrade l Smaller upper limit of BR(H → 𝑗𝑜𝑤.) → higher sensitivity to BSM l We aim to improve this result ∫ 𝑀𝑒𝑢 = 250,350,500 fb -1 for E ST = 250,350,500 GeV BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 19

X q X q Signal feature [hadronic channel] invisible l Two-Jet l Invisible particle exist l 𝑁 •• ≈ 𝑁 a ( 𝐶𝑆 Z → 𝑟𝑟 ~70% ) 𝐶𝑆 H → XX ~? ? ? % l 𝑁 ]J^‚ƒ„ ≈ 𝑁 …ƒ††‡ Major Backgrounds [hadronic channel] The major backgrounds have the final states qqll,qqlν,qqνν. 1. ZZ semileptonic 5. ννH , H → ZZ, Z → 𝑟𝑟 2. WW semileptonic 6. qqH, H → SM decay 3. Z𝜉 J 𝜉 J , Z → qq 4. W𝜉 J 𝜉 J , W → qq BSM search using invisible Higgs decay at the ILC 2017/7/24 @ILC camp 20