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ttHww study in ATLAS. Lianyou SHAN ATLAS group of IHEP, CAS LHC-MiniWS12, Xi’an June 15’ th 2014. Outline. Introduction Recent Higgs analyses in ATLAS ttHww studies Summary. Introduction. To this workshop Honor and pleasure to visit Xi’an An ancient land with legends, thanks !

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tthww study in atlas

ttHww study in ATLAS

Lianyou SHAN

ATLAS group of IHEP, CAS

LHC-MiniWS12, Xi’an

June 15’th 2014

outline
Outline
  • Introduction
  • Recent Higgs analyses in ATLAS
  • ttHww studies
  • Summary

ttHww in Xi'an

introduction
Introduction
  • To this workshop
    • Honor and pleasure to visit Xi’an
      • An ancient land with legends, thanks !
    • Seeking for overlap/collaborations
      • Learn more from you theorists
    • Informal and preliminary
      • Please pardon for possible ignorance/bias
      • Please do not cite/spread the plots/numbers yet
  • Birdview of LHC
  • ATLAS in brief

ttHww in Xi'an

slide4

日内瓦湖

  • CMS
  • LHCb
  • 机场
  • ALICE
  • ATLAS

Birdview of LHC

  • circum27 Km,100m underground CM energy 8-14TeV

ttHww in Xi'an

slide5

25 ns

8cm length & 16*10-4 cm radius

Event rate:

N = L x (pp)  109 interactions/s

Mostly soft (low pT) events

Interesting hard (high-pT) events are rare

 very powerful detectors needed

ttHww in Xi'an

atlas in brief
ATLAS in Brief

NJU

SDU

IHEP, USTC

ttHww in Xi'an

atlas in brief1
ATLAS in BRIEF
  • physics principle known
    • Quantified with

empirical practice

  • Range is important
    • Material,geometry,
    • Readout…
  • Precision is more crucial
    • Dead time
    • ERRORS are always there

ttHww in Xi'an

pile up eff i ect
Pile up effiEct
  • A price trade for high Lumi
  • Main challenge to 2012 , even Run2 analyses
  • Obstacle
    • In electron/muon reconstruction
    • In γ/jet energy measurement
  • Finally extra Backgrounds

Fortunately the experiences from Run1 are leading us out of the backgrounds

ttHww in Xi'an

atlas performance
ATLAS performance
  • Trigger rate
  • Particle reconstruction an d Identification
    • 80% 8000
    • 75%
    • 90% 900
    • 60% 30
    • 60% 400(8)
  • Event shape 60% 6
  • Tot
  • Few% systematics from each individual source

ttHww in Xi'an

most moving
Most moving

A new particle is announced in July 4 of 2012, via γγ and ZZ

Compatible with the Standard Model Higgs, 2013 Nobel

ttHww in Xi'an

recent higgs analyses in atlas
Recent Higgs analyses in ATLAS
  • Subjects
    • Production strength
    • Mass combination
    • Rare decays
    • Higgs decay to taus
    • invisible
  • Reminders/Warning :
    • Not a full list and tech details are skipped ( doc 600p+ )
    • Neither ATLAS result Nor evidence for your paper
    • Merely for your peekings/feelings

ttHww in Xi'an

production strength via
Production strength via γγ

Benefit from new calibration, main systematics are … less dependent on mass

In ZZ channel one peeks :

ttHww in Xi'an

rare decay to z
Rare decay to Zγ

ttHww in Xi'an

decay to taus
Decay to taus

ttHww in Xi'an

invisible higgs
Invisible higgs

ttHww in Xi'an

tthww studies
ttHwwstudies
  • ATLAS Upgrades for Run2
  • The Physics and status of ttHww
  • Simulations for Run2
  • Some challenges

ttHww in Xi'an

upgraded atlas
Upgraded ATLAS
  • Pixel : extracted, repaired and reinserted
    • TRT leaks fixed
    • Insertable B Layer(IBL) upgraded
  • Tilecal and LAr LV power supplies
    • extracted, inserted, extracted, inserted…
    • Jet reconstruction, egamma energy
  • Muon repairing
    • RPC for trigger
    • CSC for better momentum
  • Some others … less sensitive to phys…

ttHww in Xi'an

reminder for run2 triggers
Reminder for Run2 triggers
  • Single lepton trigger will be pre-scaled
    • Unless very high ptthreshould
  • Combined trigger is expected to help
    • Di-lepton, lepton+jets, lepton+MET …

ttHww in Xi'an

the physics in tthww
The physics in ttHww
  • The process read :
    • Or j3j4 /j1j2 can be replaced with 2 leptons
  • To explore :
    • 1’st direct measuring of Yukawa Yt
    • Searching for Massive (extra) Higgs
    • Detect possible CP Violation ( b term )

ttHww in Xi'an

the physics in tthww1
The physics in ttHww
  • We chosen better channels
    • SS2L ( 4.1% )
    • 3L ( 2.6% ) or 2L+τ ( 4.1% )
  • All are balances
    • Between x-sec and backgrounds
  • Please let me know
    • if you find better channels

ttHww in Xi'an

the status of tthww
The status of ttHww
  • CMS : PAS HIG-13-020
    • ttHWW signal is not established yet

ttHww in Xi'an

8tev tthww in atlas
8TeV ttHww in ATLAS
  • Objects definations

|η| < 2.5

pT > 20 in SS2L

Leading pT > 15 for 3L

HT > 100GeV

ttHww in Xi'an

8tev tthww in atlas1
8TeV ttHww in ATLAS
  • Reject main backgrounds
  • Wjets, Zjets suppression
    • lepton isolation
    • MET against Zjets
  • Further WZ suppression
    • ≥ 2 b-tag
  • fake is serious

ttHww in Xi'an

preliminary numbers
Preliminary numbers
  • This is NOT any result !

ttHww in Xi'an

simulations for run2
Simulations for Run2
  • Siganl enhance over topless backgrounds
    • For the gluonic PDF
    • Unfortunately , ,are still heavy
  • Final particles are boost
    • survive di-lepton trigger
    • Survive pileup cleanings
    • Higher pTthreshould
  • Better b-tag
    • Upgraded IBL

ttHww in Xi'an

only a hint
Only a hint

An realistic extrapolation

from 8 to 14 TeV

There are also

independent “predictions”

ECLA-ATL-PHYS-PUB

-2013-014

ArXiv 1307.7280-v2

Please note only 5 times of signal, close to the margin of statistics

ttHww in Xi'an

challenges
Challenges
  • Estimate fake from real data
    • A essential but tedious/hard step
  • Uncertainty from high jets multiplicity
    • No sufficiently reliable x-sect for and WZ yet
    • An independent measurement of ?
  • Event topology reconstruction
    • probable pairing the charged lepton and b ?
    • Probable recovering or merging of neutrinos ?

ttHww in Xi'an

kinematical topology reconstruction
kinematical topology reconstruction

Could we find an angle or an energy

As the signature of Higgs ?

  • Something like fat jet ?
  • Any variant of MT ? Something like MT2 ?
  • Most probable/likely ?

Charge lepton assignment ?

neutrino recovering ?

ttHww in Xi'an

summary
Summary
  • Higgs properties are investigated in LHC
    • But the output is still very preliminary
    • expect more data from Run2
  • ttHww seem meaningful
    • Preparations/progress for experiment
    • The core parts are identified …
    • Your contributions/solutions are welcome !

Thanks !

ttHww in Xi'an