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

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

Sep 05, 2022 165 likes •379 views

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 X q q Motivation l In SM, Higgs decays invisibly through LHC CMS result (95% CL) H ZZ

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SLIDE 1

BSM search using invisible Higgs decay at the ILC

Yu Kato, The University of Tokyo

ILC Summer Camp July 24, 2017

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SLIDE 2

lIn SM, Higgs decays invisibly through H → ZZ∗ → 4𝜉 (BR(H → 𝑗𝑜𝑤.)~0.1%) lIf BR(H → 𝑗𝑜𝑤.) exceeds SM prediction , It signifies new physics beyond SM (BSM) lIn this study, we estimate upper limit of BR(H → 𝑗𝑜𝑤.) lCompare between left & right polarization at the ILC

Motivation

q q

BSM

X X

invisible

Dark Matter… SUSY…

visible 𝐶𝑆 H → XX ~? ? ? % 𝑂

8 ∝ 𝜏;<・𝐶𝑆 H → 𝑗𝑜𝑤𝑗𝑡𝑗𝑐𝑚𝑓

2017/7/24 @ILC camp

BSM search using invisible Higgs decay at the ILC

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q q Z Z ν ν ν ν

𝐶𝑆 H → ZZ∗ → 4𝜉 ~0.1% invisible 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)

LHC CMS result (95% CL)

  • bserved (expected)

24% (23%)

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SLIDE 3

Setting & Flow of Analysis

lSetting

  • Generator: WHIZARD 1.95
  • Samples: DBD sample + Dirac sample (eBeC → qqH, H → ZZ∗ → 4𝜉)
  • Detector: ILD full simulation
  • Ecm= 250 GeV, ∫𝑀𝑒𝑢 = 250 fb-1 , 𝑄

JK, 𝑄JL = −0.8, +0.3 , (+0.8, −0.3)

lFlow 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

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BSM search using invisible Higgs decay at the ILC

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SLIDE 4

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: Npfo, Ntrack
  • 4. di-jet (Z) pt: PtZ
  • 5. di-jet mass: MZ
  • 6. di-jet polar angle: θZ
  • 7. recoil mass: Mrecoil
  • 8. multi-variate analysis: Boosted Decision Tree(BDT) method

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SLIDE 5

Recoil Mass Plots [Ecm = 250 GeV, 250 fb-1,BR(H->inv.)=10%]

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Left Right

No. Cut No. Cut 1 Isolated lepton veto 5 80 < Mz < 100 2 Loose Cut (Ptz,Mz,Mrecoil) 6 |cosθZ|<0.9 3 Npfo>15 & Ntrack>6 & Ntrackji>1 7 100 < Mrecoil < 160 4 20 < Ptz < 80 8 BDT cut

MVA input variables

mz cosj1 cosz cosj2 TMVA v-4.2.0

BSM search using invisible Higgs decay at the ILC

significance: 15.5 efficiency: 63.5% significance: 19.7 efficiency: 65.9%

Preliminary

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SLIDE 6

How to set UL

l Template

Ø Assume BR(H→invisible)=[1,2,…,10]% -> Event selection Ø Get # of events (NS+B) in window range (Mrecoil∈[120,140] GeV) Ø Generate Poisson distribution of NS+B -> Get 95% CL limit (NUL) Ø Repeat for each BR(H→invisible)=[1,2,…,10]% -> Get calibration line between NUL and UL

l Toy MC

Ø Fit template bkg -> Generate pseudo experiment by fluctuated bkg function Ø Get # of events (NS+B) in window range (Mrecoil∈[120,140] GeV) Ø Translate NS+B into UL of BR(H→invisible) using calibration line Ø Repeat 10000 times -> Obtain UL distribution

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BSM search using invisible Higgs decay at the ILC

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NS+B NUL UL NUL

UL[%]

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SLIDE 7

2017/7/24 @ILC camp 7

Left polarization Right polarization

250 fb-1 H20 (800 fb-1 )

BSM search using invisible Higgs decay at the ILC

Statistical fluctuation of Upper Limit

UL=0.95±0.45% UL=0.25±0.17% UL=0.55±0.25% UL=0.53±0.31%

Preliminary

250 fb-1 800 fb-1 250 fb-1 800 fb-1

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SLIDE 8

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BSM search using invisible Higgs decay at the ILC

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Left Right

250 fb-1

Left Right

H20 (800 fb-1) Preliminary

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SLIDE 9

Summary

Use measurement of BR(H → 𝑗𝑜𝑤.) as a means for indirect BSM search lMotivation

  • 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 EST = 250 GeV, assuming 250 fbCW

lStatus

  • optimized data selection methods
  • set UL using toy MC for both left and right scenario

2017/7/24 @ILC camp

BSM search using invisible Higgs decay at the ILC

9 UL of BR [%] (95%CL) Left polarization Right polarization 250 fbCW 0.95±0.45 (1σ) 0.53±0.31 (1σ) H20 scenario (800 fbCW) 0.55±0.25 (1σ) 0.25±0.17 (1σ) Previous study(250 fbCW) 0.95 0.69 Left polarization Right polarization significance [250 fbCW] 15.5 19.7

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SLIDE 10

Plan

lEvaluate jet energy resolution and scale of Detector lConstruct error matrix → kinematic fit

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BSM search using invisible Higgs decay at the ILC

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sample: 2f_z_h 𝑡

  • = 250 GeV

∫𝑀𝑒𝑢 = 250 fb-1

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SLIDE 11

Back Up

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Recoil Mass Method

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lWe can measure Higgs without directly looking at it → model independent 𝑁]J^

_

= 𝑡

  • − 𝐹a _ − 𝑞

⃗a _ lHiggs-strahlung cross section can be obtained using leptonic decay of Z

𝜏;< = 𝑂8 𝐶𝑆 Z → 𝑚B𝑚C ε8𝑀 ε8: signal efficiency, Nw: # 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

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SLIDE 13

Cut table [Ecm=250GeV,250fb-1,Left]

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Hadronic Channel Analysis

BSM search using invisible Higgs decay at the ILC

数式を⼊⼒します。

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SLIDE 14

Cut table [Ecm=250GeV,250fb-1,Right]

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Hadronic Channel Analysis

BSM search using invisible Higgs decay at the ILC

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SLIDE 15

Fit Signal & Background

signal: GPET (Gaussian + Exponential) bkg : 5th order polynomial

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BSM search using invisible Higgs decay at the ILC

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Left Right

Preliminary

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SLIDE 16

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Left polarization Right polarization

BSM search using invisible Higgs decay at the ILC

Toy Monte Carlo to Set Upper Limit

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

Preliminary

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SLIDE 17

2017/7/24 @ILC camp 17

Left polarization Right polarization

250 fb-1 H20 (800 fb-1 )

BSM search using invisible Higgs decay at the ILC

Toy Monte Carlo to Set Upper Limit

UL=1.03% (95%CL) UL=0.39% (95%CL) UL=0.58% (95%CL) UL=0.69% (95%CL)

Preliminary

250 fb-1 250 fb-1 800 fb-1 800 fb-1

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SLIDE 18

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Left Right

BSM search using invisible Higgs decay at the ILC

Toy Monte Carlo to set upper limit

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

Preliminary

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SLIDE 19

Previous Study

lSmaller upper limit of BR(H → 𝑗𝑜𝑤.)

→ higher sensitivity to BSM

lWe aim to improve this result

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BSM search using invisible Higgs decay at the ILC

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  • A. Ishikawa (Tohoku Unv.),

”Search for Invisible Higgs Decays at the ILC” LCWS2014@Belgrade

∫ 𝑀𝑒𝑢 =250,350,500 fb-1 for EST =250,350,500 GeV

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SLIDE 20

Signal feature [hadronic channel]

lTwo-Jet lInvisible particle exist l𝑁•• ≈ 𝑁a (𝐶𝑆 Z → 𝑟𝑟 ~70%) l𝑁]J^‚ƒ„ ≈ 𝑁…ƒ††‡

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BSM search using invisible Higgs decay at the ILC

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q q X X

invisible 𝐶𝑆 H → XX ~? ? ? %

Major Backgrounds [hadronic channel]

The major backgrounds have the final states qqll,qqlν,qqνν.

  • 1. ZZ semileptonic
  • 2. WW semileptonic
  • 3. Z𝜉J𝜉J, Z → qq
  • 4. W𝜉J𝜉J, W → qq
  • 5. ννH,H → ZZ, Z → 𝑟𝑟
  • 6. qqH, H → SM decay