1. New Physics Search at ATLAS
Yu Bai2, Shan Jin2, Sabine Kraml3, Feng Lu2,
Emmanuel Monnier1, LianYou Shan2, Muanza Steve1,
Huaqiao Zhang1, Xueyao Zhang4, Zhichao Zhan4,2
( 1:CPPM, 2:IHEP, 3:LPSC, 4:SDU )
F. Lu, FCPPL-3，Lyon/France

2. F. Lu, FCPPL-3，Lyon/France
Outline
CSC official result
ttH(WW*) 2L&3L 14TeV Fulsim Analysis
ttH(WW*) 3L 14TeV Fulsim Analysis
ttH extension analysis (work in progress)
SUSY 2top incl. & Excl. 10TeV Fulsim Analysis
SUSY 4top 1L & 0L 10TeV Fastsim Analysis
Further plan
F. Lu, FCPPL-3，Lyon/France

3. ttH(HWW)：top Yukawa Coupling measurement
Ndata - Nbkg
Systematic errors
Nnl ( n=2, 3 ): observed events in ttH-WW* n-lepton final states
L: LHC integrated luminosity
εnl: total efficiency of n-lepton final states
I(MH): the integral over the parton momentum in initial states, propagator of
gluon or quark in middle states and lepton/jet phase space in the final states
Cnl: the combination factor of branching of W decays
Directly measures: (ttH)*Br(HWW)=Nnl/(LnlCnl)
Important to study Higgs property
F. Lu, FCPPL-3，Lyon/France

4. F. Lu, FCPPL-3，Lyon/France
Selection
Basic selection
e, mu, C4-jet: |η|<2.5; Pt>15 GeV/c
e(Egamma): isEM=0x3FF,author=1,3
mu(StacoMu): IscombinedMuon=1
Calo Isolation: etcone20<10 GeV
Track Isolation: trkPtmax20<2.0 GeV/c
Cone Isolation:muon: dR(mu,jet)>0.25
electron: dR(e,jet) > 0.2 or
dR(e,jet)<0.1 and Eele/Ejet>0.65
( Remove related jet )
Isolation: Nlepton>=2/3, Njets>=6/4
Nlep=2/3,Same charge (for 2L)
Zveto: (75,100) (lep Pt> 6GeV/c)
MuonPt > 20GeV/c Yt b P
2 leptons
4 light jets P b b P
3 leptons
2 light jets P
F. Lu, FCPPL-3，Lyon/France b

5. ttH(HWW) Cut flow ( CSC@14TeV )
F. Lu, FCPPL-3，Lyon/France

6. ttH: Delayed by LHC Accident@2008
All important effects include: trigger inefficiency,
pile up, theo. & instr. Uncertainties were studied.
For the preparation of 2008 real data analysis,also
studied BKG data driven estimation & DPDmaker
Unfortunately, 19/Sep./2008 LHC accident had
greatly changed LHC Lum. & Ecm Plan, ttH(WW)
study is impossible within three years
Tevatron result ruled out MH in GeV/c2
F. Lu, FCPPL-3，Lyon/France

7. F. Lu, FCPPL-3，Lyon/France
WH(H->WW*)
Estimation of HW coupling (independent on Yukawa coupling)
Focus on three leptonic decay final state (two lepton final state also studied but overwhelmed by the W+Jets background)
Active Contribution to H production cross section Atlas note (ttH, WH…)
F. Lu, FCPPL-3，Lyon/France

8. WH(->WW*) Selection
Sample : CSC MC fulsim sample
Event Selection
At least 3 high pt isolation leptons (leading pt > 35GeV
and the rest > 15GeV)
Z Mass Veto (Z lepton candidate with invariant mass 65-
105GeV excluded)
Large Missing Et(>45GeV)
HS Cut(Lepton angular distribution)
B-jet veto (jet activity cut and b veto)
Background Studied: WZ, ttbar, ZZ, ttW,
Wbb,W+Jets
F. Lu, FCPPL-3，Lyon/France

9. F. Lu, FCPPL-3，Lyon/France
WH(->WW*) Results
Input(fb)
Basic selection
Isolation and Z veto
Missing Et HS
(B) jet veto
WH->WW(3L)
5.04
1.18
0.53
0.47
0.36
0.31+/-0.02 WZ
750
165.5
0.74
0.63
0.21
/-0.06
ttbar
833000
3564.3
6.11
5.10
1.02
/-0.3 ZZ
72.5
34.5
0.06
0.013
0.008
0.005+/-0.001
ttW
61.1
1.35
0.19
0.07
/-0.003
Wbb
66700
3.1 _
W(->ev)+Jets
2*10^7
17.6
W(->μv)+Jets
27.6
Total background
0.45+/-0.70
F. Lu, FCPPL-3，Lyon/France 9

10. SUSY：decay to 1-2 top pair final state
Extension of ttH to SUSY ( SS-2top, 4top) towards to low lum., top decays provide iso. Leptons or high jet multiplicity which can suppress SM BKG
SUSY is the most promising theory beyond SM
SUSY LSP particle maybe source of dark matter, ~23% universe matter
SUSY mechanics predicts large x-section, may available at lower lum.
SUSY decay has important feature: MET, supress SM BKG
SUSY-2top
~g~g →2top + 2c+ 2~10 (LSP)
iso. Leptons + at least four Jets + MET
SUSY-4top
~g~g → 4top/4W4b + 2~10 (LSP)
 1L+ at least 8 jets + MET
 0L + at least 10 jets +MET
F. Lu, FCPPL-3，Lyon/France

11. Compressed-SUSY-2top：10TeV
m(~q)=1 TeV
m(~c01)=75 GeV
m(~t1)=110GeV
m(t)=172.5 GeV
Muanza Steve(CPPM): Compressed SUSY SLHA
Inclusive SUSY Signal
m(~g)
(GeV)
sLO (pb)
K-factor
Ngen
Evt Filter
Filter e
(%)
300
450
1.8
10k
Nlep>1
pT>10 GeV
|h|<2.7
4.5
400
360
1.3
500
350
0.7
550
0.4
Exclusive SUSY Signal
m(~g)
(GeV)
sLO
(pb)
K-factor
Ngen
300
2.2
1.8
10k
400
0.41
500
0.075
550
0.031
F. Lu, FCPPL-3，Lyon/France

12. F. Lu, FCPPL-3，Lyon/France
Comparison with Official:Atl-phys-pub “Same–sign leptons + 2jets +
F. Lu, FCPPL-3，Lyon/France

13. Compressed-SUSY-2top: Incl. & Excl.
Topology and strategy
Excl. Decay Chain:
Incl. Topology:
Works in progress:
Our X-section is much larger than the official, same trigger: L
Atlas fulsim samples for signal &SM BKG
Same topology & similar selection, but our own optimization
Our SS-2top fulsim analysis shows quite competition relative
to the Official result, detail analysis is still in proceeding
F. Lu, FCPPL-3，Lyon/France

14. mSUGRA-SUSY：4top/4W4b final state
Sabine Kraml (LSPC): SLHA based on MSSM
Sparticle Spectrum ( in GeV ) :
~chi_10: ~chi_20, ~chi_1+ -: ~t1: 350
~g: ~chi_30,40, ~chi_2+ -: ~q, ~l: ~1500
Decay Branching Ratio ( cost = ):
~g → ~t1 tbar +cc. 100% , ~t1 → ~chi_10 t : %
~t1 → ~chi_1+ b: 4.3% , ~chi_1+ → ~chi_10 W+ 100%
SUSY-4top production:
gg → ~g~g → 4top/4W4b + 2~chi_10( LSP )
NLO (gg  ~g~g) = 1.13 pb at 10 TeV
Feasibility is investigated by private fastsim production
F. Lu, FCPPL-3，Lyon/France

15. F. Lu, FCPPL-3，Lyon/France
Fast-Full simulation comparison at 10TeV from ATL-PHYS-PUB , triggered by Etjet>70G or MET>30G for early data
Fast performance is well for feasibility study
F. Lu, FCPPL-3，Lyon/France

16. ATL-PHYS-PUB-2009-075 14TeV@1fb-1 Multi-jets with b-jets
Finally ttbar is dominate in BKG
F. Lu, FCPPL-3，Lyon/France

17. Atl-phys-pub-2009-066 Jets+MET+0L/1L
About JET trigger & lepton trigger: efficiency is high ~99%
F. Lu, FCPPL-3，Lyon/France

18. Susy-4top-1L/0L Atlfast Analysis 10TeV@200pb-1 Work in progress
 1L(15GeV, iso.)
 8jets(20GeV,4jet-80GeV,leading 120GeV)
MET>100GeV
triggered by 1L or j70_xE70
FastAna shows ttbar is well under control
0L:
 10jets(20GeV,4jet-80GeV,leading 120GeV)
triggered by j70_xE70
FastAna shows ttbar & Z()4/5jets
is well under control
Susy-4top has great feature on strong jet activity & MET which can separate it from SM BKG
F. Lu, FCPPL-3，Lyon/France

19. F. Lu, FCPPL-3，Lyon/France
Further Plan
ttH CSC analysis established a good base to
naturally extend to SUSY area with high x-section
Next two years focus on 7TeV real data analysis,
especially ttbar(jets) to understand detector
performance and BKG behavior
Search for SUSY in two samples: susy-2top
from  2L sample; susy-4top from 8jets sample;
later apply MET>50/100GeV on samples, to
carefully compare DATA&MC distribution/yield
F. Lu, FCPPL-3，Lyon/France 19

20. F. Lu, FCPPL-3，Lyon/France
Thank you for your attention!
Welcome your comments!
F. Lu, FCPPL-3，Lyon/France