1. ATLAS Physics Analysis in China
On behalf of Chinese ATLAS Cluster
Feng LU
（ IHEP / CAS）
13/Dec./2006
1st Chinese-French Workshop, Beijing

2. 1st Chinese-French Workshop, Beijing
Outline
General Information
Physics analysis Status
Summary
13/Dec./2006
1st Chinese-French Workshop, Beijing

3. Chinese Physical ATLAS Cluster
Institute of High Energy Physics (IHEP, 9p):
Y. BAI, S. JIN, H.B. LIAO, F. LU, Y.Q. OU, L. ROOS (IN2P3),
L.Y. SHAN, G.L. TONG, H.Q. ZHANG
Shandong University (SDU, 7p):
C.F. FENG, M. HE, D. LIU, M.H. LIU, H. ZHANG, X.Y. ZHANG,
C.G. ZHU
University of Science and Technology, China (USTC, 9p):
C.W. GONG, L. HAN , Y. JIANG, G. JIN, G.Z. LI, Y.W. LIU,
H.T. WEI, X.Q. YU, P. ZHANG
Nanjing University (NJU, 6p):
S.J. CHEN, T.Y. CHEN, G.B. GONG, X.W. HU, M. QI, J.H. ZHONG
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1st Chinese-French Workshop, Beijing

4. 1st Chinese-French Workshop, Beijing
Chinese ATLAS Physics:
IHEP : ttH Yukawa Coupling, HVV anomalous Coupling, HW (Higgs)
SDU : top pair Spin Correlation (Top)
USTC : e resonance search in R-parity violation (SUSY), WZ (SM)
NJU : Single top (tb) production (Top)
Two topics (ttH Yukawa coupling/ tt spin correlation, supported by
NSFC ) with cooperation with CPPM/in2p3 (Emmanuel Monnier et. al., Marseille, France) since Oct./2004, which gives important help to Chinese ATLAS physics
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1st Chinese-French Workshop, Beijing

5. 1st Chinese-French Workshop, Beijing
ttH(WW) -- IHEP
Higgs mass is favored [114, 210GeV]
CERN LEP2: SM Higgs mass is above GeV ( 95% C.L. )
Global fit, Higgs mass lower than 208 GeV ( 95% C.L. )
MSSM, lightest Higgs mass is within 150GeV
Light Higgs search mainly through:
HZZ(*)  4l, H   and ppttH(H bb) ( very hot topic ! )
top Yukawa coupling direct measurement
ppttH(HWW(*)) gives important contribution when Higgs
mass  [120, 240GeV] ( important ! IHEP/CPPM cooperation )
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1st Chinese-French Workshop, Beijing

6. Top quark Yukawa Coupling
ttH could directly measures top-quark Yukawa coupling
Top-quark loop
1) Determine Higgs candidate properties
2) Comparison with indirectly top-quark Yukawa coupling (right)
measurement to check for new physics
13/Dec./2006
1st Chinese-French Workshop, Beijing

7. ttH (WW(*)) Production
SM Higgs decay
SM Higgs Production
ppttH ( H W W(*) ) has enough events when mH[120, 240]GeV/c2
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1st Chinese-French Workshop, Beijing

8. ttH(WW) FulSim Analysis
ttH,HWW tagged by two final states:
ttH-2L Signal: ttH,HWW  4W2b  2l2b4j2  2l6j
ttH-3L Signal: ttH,HWW  4W2b  3l2b2j3  3l4j
Background is strong, need careful FulSim study
Rome FulSim AOD analysis:
Signal : ttH(WW)-2L, 3L (L=e,mu)
Main BKG : tt, ttZ, ttW
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1st Chinese-French Workshop, Beijing

9. 1st Chinese-French Workshop, Beijing
ttH-2L(3L) selection
Good isolated lepton number is two(three) and good jet number is above five(three)
good L=e,: PT 20GeV/c, || PID
good Jet: Pt 15GeV/c, || 2.5
same charge sign for ttH-2L
lepton isolation
Z veto by rejecting events in MLL [75,100] GeV/c2 ( [76.2,106.2] GeV/c2 ) window
ttH-3L selection is basically similar to ttH-2L’s
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1st Chinese-French Workshop, Beijing

10. 30fb-1 normalization table (without b-Tag)
ttH summary
30fb-1 normalization table (without b-Tag)
ttH120
ttH160
ttH200
ttW
ttZ
tt(1L)
tt(2L)
ttH-2L
7.40.2
361
19 1
25 2
16 1
ttH-3L
151
71
Full simulation analysis shows that top-quark Yukawa coupling can be measured to a few tens of percent
Write an ATLAS note, turn to prepare CSC sample
Physical analysis (HG6 CSC note)
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1st Chinese-French Workshop, Beijing

11. Possible topics at IHEP
Anomalous HVV coupling ( V= W,Z )
( PRD67,114024,2003, Y.-P. Kuang et. al. )
Topology: pp  W+W+jj  l+l+jj ( l =e,  )
To test new physics
Working on MC generation at ATLAS
HWWWW 2L, 3L final state, some similarities to ttH(WW)
Motivation
Higgs observation if Higgs mass above 150 GeV
Higgs weak gauge boson coupling
Status
Generator ready and validated by Altfast
Full simulation analysis is in preparation
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1st Chinese-French Workshop, Beijing

12. 1st Chinese-French Workshop, Beijing
pp  W+W+jj ++jj
A test by ComHep to
show ComHep-Pythia
chain is vailable
Why not forward jets ?
(due to statistics/problem?)
Need further check by altfast !
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1st Chinese-French Workshop, Beijing

13. Motivations: test top production and decay
tt Spin Correlation -- SDU
Motivations: test top production and decay
Top decay
Top production
Strong Interaction gg,qq tt pairs
tWb vertex
Top spin correlated
BR(tWb)~100%
No top hadronization
LHC
σ ~850 pb
Tevatron
σ ~7 pb
Test SM, Search for anomalous couplings
tt final states (10 fb-1)
Full hadronic (3.7M): jets
Dileptonic (0.4M): 2 l + 2 b + 2 n
Semileptonic (2.5M): l + n + 2b + jets
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1st Chinese-French Workshop, Beijing

14. 1st Chinese-French Workshop, Beijing
Measurement
Test the top production …
t and t not polarised in tt pairs, but correlations between spins of t and t
Mtt<550 GeV
A=0.33
A=0.42
… by measuring angular distributions of daughter particles in top rest frames
Angle between t(t) and spin analysers
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1st Chinese-French Workshop, Beijing

15. 1st Chinese-French Workshop, Beijing
Fulsim Rome samples
Signal samples – semileptonic tt, lepton = e, m:
TopReX+PYTHIA
AOD/CBNT
1500 pb-1
375k
# 4520, 4521
Background samples (most important with Atlfast):
W+4jets
AOD
75 pb-1
180k
# A7
Single Top
950 pb pb pb-1
90k 70k 19k
# # 4530, # 4540
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1st Chinese-French Workshop, Beijing

16. tt spin correlation summary
A (±stat)
SM value
0.42
TopReX Atlfast
0.42  0.02
TopReX Full sim
0.45  0.06
Full sim
0.02  0.09
TopRex values compatible with SM expectation
no spin correlation ... it gives 0
Write two ATLAS notes with CPPM cooperation
Next CSC samples physics analysis is preparing normally
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1st Chinese-French Workshop, Beijing

17. 1st Chinese-French Workshop, Beijing
ATLAS Physics at USTC
Search sneutrino em resonant to probe R-parity violating SUSY
back-to-back di-lepton in r-f
high pT~M/2 lepton
missing ET veto
dominant physics background
WW,ttbar, Ztt
Preliminary D0 result:
l’l < M=100GeV
1fb-1
First try with Atlfast:
l’l < M=100GeV
30fb-1
Very preliminary
13/Dec./2006
1st Chinese-French Workshop, Beijing

18. ATLAS Physics at USTC (cont.)
(1) cross section measurement of WZ leptons (Tri-lepton+MET)
(2) sensitivities to anomalous trilinear gauge boson couplings (TGCs)
The values of the anomalous TGCs contribute only via s-channel gauge boson intermediaries, and therefore the transverse momentum distributions of the vector bosons are particularly sensitive to the TGCs.
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1st Chinese-French Workshop, Beijing

19. 1st Chinese-French Workshop, Beijing
ATLAS Physics at NJU
To study single top (top+bottom) production at ATLAS
Topology: W(1L+MET) + 2b (B-tagging is important)
Motivation:
test electroweak properties of the top quark
Wtb coupling measurement
CKM element |Vtb|2 measurement
are backgrounds to many new physics search
sensitivity to new dynamics like topcolor
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1st Chinese-French Workshop, Beijing

20. 1st Chinese-French Workshop, Beijing
Summary
Chinese ATLAS physics analysis was initiated by ttH(WW) Yukawa
coupling and tt spin correlation studies, CPPM/IN2P3 cooperation is
very effective in both analyses, three ATLAS notes on ROME sample
physics analyses finished, next ATLAS CSC sample physical analyses
are in preparation
USTC and NJU joining strengthen Chinese team and widen physics
interests. There are many common links among these Chinese
sub-groups, such as lepton isolation and b-tagging
A robust team of Chinese ATLAS physics analysis is well formed and
trained preliminarily, warm-up stage was passed, next year will be very
hopeful to make more progresses with stronger cooperation
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1st Chinese-French Workshop, Beijing

21. 1st Chinese-French Workshop, Beijing
Greatly appreciate for CPPM/IN2P3 cooperation !
Thanks for your attention !
13/Dec./2006
1st Chinese-French Workshop, Beijing