final results on tth h + -
DESCRIPTION
Final results on ttH H + -. Akihiro, ITO, Reisaburo TANAKA O kayama University Shoji ASAI, Junichi TANAKA ICEPP, University of Tokyo Junichi KANZAKI KEK Many thanks to Lidija ZIVKOVIC (Weizmann) A TLAS Higgs Working Group Meeting, September 22, 2003. Contents. - PowerPoint PPT PresentationTRANSCRIPT
Final results on ttH H+-Final results on ttH H+-
Akihiro, ITO, Reisaburo TANAKAOkayama University
Shoji ASAI, Junichi TANAKAICEPP, University of Tokyo
Junichi KANZAKIKEK
Many thanks to Lidija ZIVKOVIC (Weizmann)
ATLAS Higgs Working Group Meeting, September 22, 2003
2003/9/22 Final Results on ttH (H->tau+tau) 2
ContentsContents
1. ttH (H+-) analysis
2. tag algorithm
3. ATLFTAU
4. Summary
2003/9/22 Final Results on ttH (H->tau+tau) 3
1. ttH (H+-) analysis1. ttH (H+-) analysis Physics Motivation: direct determination of top-Yukawa coupling
in the mass range MH=[100, 130]GeV/c2. Complementary to Hbb. Signal
Small cross section (Br 40fb @MH=120 GeV/c2) ttH WbWb … 9 different modes, followings are analyzed.
lb+jjb +l+h channel … same charge di-lepton ll Br=14%lb+jjb + h+h channel … single lepton Br=13%lb+jjb +l+l channel … tri-lepton Br= 4%lb+lb+l+h channel … tri-lepton Br= 2%lb+lb+h+h channel … di-lepton Br= 2%
BackgroundsHUGE tt ! (ttH)Br(H) / (tt) 10-4, ttW ttZ, ttWW, ttH(HWW) … irreducible backgrounds.
Key issue: -tag, fake-jet rejection
Israel 5 modesJapan 2 modes
2003/9/22 Final Results on ttH (H->tau+tau) 4
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
100 110 120 130 140 150 160 170 180
top-Yukawa coupling in ttH(Hbb,+-,W+W-)
2030%
L = 30 fb-1
Preliminary
Hbbpoor S/N
HW+W-
H+-
(Weizmann)
MH [GeV/c2]
gtt
H/g
ttH
Athens Physics Workshop (R.T.)
2003/9/22 Final Results on ttH (H->tau+tau) 5
2 issues tag algorithm
ATLFTAU v.s. Weizmann- ATLFTAU: parametrized 50% fixed efficiency- Weizmann: inspired by TDR algorithm.
Is ttH(H-> ) lb+jjb + h+h possible?
2003/9/22 Final Results on ttH (H->tau+tau) 6
2. tag algorithm 2. tag algorithm Issue: tag algorithm optimization for ttH ATLFTAU … 50% fixed efficiency for low Pt taus is not good. Leads to unreasonable low rejection factor.
Emulated Weizmann tau identification method Rj-track < 0.07 (distance between jet and nearest track) Ntrack = 1 or 3 (# of tracks with PT>5GeV/c in DR = 0.07) PT(track) > 5GeV/c (PT of track nearest to jet) I < 0.03 I = { ET(0.4) – ET(0.2) } / ET(0.2) PT(-jet) > 20GeV/c Ncell < 6 (# of cells in jet, COMMON/ATLFEVENT/ K(nj, 3) )
Observed good agreements on these variables. Though differences in PT(track) and I distributions.
2003/9/22 Final Results on ttH (H->tau+tau) 7
0 50 100 150 200 2500.0
0.2
0.4
0.6
10
100
pT (GeV)
je
t re
ject
ion
efficien
cy tag efficiency and jet rejection
0 50 100 150 200 2500.0
0.2
0.4
0.6
10
100
pT (GeV)
jet
reje
ction
efficien
cy
algorithm
mH = 120 GeV50%
fake real pT--jet
E.Gross, June 25, 2003@Higgs WG
2003/9/22 Final Results on ttH (H->tau+tau) 8
Weizmann cut on llb + jjb + hb + jjb + h + h + h High Level Trigger Lepton
PT > 20GeV/c, |η| < 2.5, Nlepto
n ≥ 1 Jet
PTj1 > 35GeV/c, PT
j2 > 25GeV/c
|η| < 4.5, Njet ≥ 2 b-jet ( efficiency = 70%)
PT > 20GeV/c, |η| < 2.5,
Nb-jet ≥ 2 -jet
PT > 20GeV/c, |η| < 2.0,
N-jet ≥ 2
Mass windows
60 < Mqq < 90 GeV
150 < Mbjj < 195 GeV
50 < M-jet,-jet < 120 GeV
Missing ET > 25GeVΦ( , missing ) < 1opposite charge of -jet
B-tag efficiency 70%
2003/9/22 Final Results on ttH (H->tau+tau) 9
(GeV)
Labeled -jet
Other jetJapan
Israel
ATLFAST, ttH MH=120GeV, Low lumi.
Rj-track< 0.07 Ntrack= 1 or 3 PT> 5 GeV/c
2003/9/22 Final Results on ttH (H->tau+tau) 10
(GeV)
Japan
Israel
ATLFAST, ttH MH=120GeV, Low lumi.
ConeR<0.3
N5I< 0.03 PT> 20 GeV/c
Very powerful cut !
2003/9/22 Final Results on ttH (H->tau+tau) 11
Japan Israel
ttH 2.9 4.7
tt 8.9 5.9
Japan Israel
ttH(H)
efficiency 44% 44%
rejection 80 84
tt
Efficiency 38% 33%
rejection 72 100
Results with Weizmann tau ID
ttHlb+jjb + h+hMH=120GeV, Low lumi. 100fb-1
Remaining differenceYPAR(93) - fraction of tau-jet in a cone Rtau-jet
Japan: default 0.9Israel : 0.0 (optimistic?)
Ncell Ncell
2003/9/22 Final Results on ttH (H->tau+tau) 12
(GeV)
Signal-jet
ETcell > 0.5GeV
(noise & pile-up) signal
tt
ttH tt
efficiency 4444% 3838%
rejection 8087 7278
Japan
ttH 3.0
tt 4.4
Think about ET cuts in cells ?
N4ET>0.5GeV
ttHlb+jjb + h+hMH=120GeV, Low lumi. 100fb-1
2003/9/22 Final Results on ttH (H->tau+tau) 13
Japan
ttH tt
precuts 38.8 1555
Trigger 37.5 (97) 1405 (90)
Q1*Q2 < 0 28.3 (75) 658 (47)
18.6 (66) 399 (61)
MW wind. 11.2 (60) 155 (39)
Mtop wind 8.8 (79) 77.2 (50)
|W| 7.8 (89) 56.8 (74)
Missing ET6.0 (77) 39.0 (69)
Ptlep 5.5 (92) 34.6 (89)
PTj1 5.1 (93) 24.0 (69)
PTj1 3.5 (69) 10.7 (44)
M-jet,-jet wind 2.9 (80) 8.9 (83)
Japan
ttH tt
precuts 40.3 1256
Trigger 39.2 (97) 1131 (90)
Q1*Q2 < 0 30.4 (78) 516 (46)
20.3 (67) 248 (48)
MW wind. 12.2 (60) 86.1 (35)
Mtop wind 10.1 (83) 39.0 (45)
|W| 8.8 (87) 29.2 (75)
Missing ET6.6 (75) 16.0 (55)
Ptlep 5.9 (89) 15.1 (94)
PTj1 5.3 (90) 8.9 (59)
PTj1 3.4 (64) 4.4 (50)
M-jet,-jet wind 3.0 (88) 4.4 (100)
Without ETcell cut With ET
cell cut
Number of events for 100fb-1 (percentage wrt previous cut)
2003/9/22 Final Results on ttH (H->tau+tau) 14
3. ATLFTAU3. ATLFTAUAtlftau Results
• Reasons• Fake -jet charge
Japan Israel
ttH 2.7 2.5
tt 126.7 22.1
6 times!
Japan Israel
Method
Random number [0,1]
< 0.5 Q=-1
> 0.5 Q=+1
Sum up charged track in
R = 0.07 from Jet
2003/9/22 Final Results on ttH (H->tau+tau) 15
Generator
ATLFAST parameter
Japan Israel
Generator PYTHIA6.2 PYTHIA6.2
PDF CTEQ5L CTEQ5L
tt event number 500k 300k
cross section 492pb 490pb
Japan Israel
YPAR(90) 10.000 10.000
YPAR(91) 2.500 2.500
YPAR(92) 0.300 0.300
YPAR(93) 0.900 0.000
YPAR(93) : fraction in a cone R_tauj for tau-jet
2003/9/22 Final Results on ttH (H->tau+tau) 16
ttH ttQ*Q2
ttH tt
Israel
Japan
Drops the ttH signal.But also artificial cut on tt.Unphysical effect.
Explains factor 3 difference
2003/9/22 Final Results on ttH (H->tau+tau) 17
Japan Israel
ttH tt ttH tt
precuts 61.6 19532 75 20330
Trigger 59.0 (96) 18115 (93) 68.5 (91) 17671 (87)
Q1*Q2 < 0 20.1 (34) 1427 (7.9) 24 (35) 1426 (8.1)
12.5 (62) 685 (48) 15 (63) 704 (49)
MW wind. 8.1 (65) 308 (45) 8.4 (56) 301 (43)
Mtop wind 6.7 (83) 190 (62) 6.16 (73) 191.5 (64)
|W| 6.0 (90) 167 (88) 5.35 (87) 150 (78)
Missing ET4.8 (80) 133 (80) 4.5 (84) 117 (78)
Ptlep 4.5 (94) 108 (81) 4.3 (96) 96.5 (82)
PTj1 3.9 (87) 85.6 (79) 4.08 (95) 84.6 (88)
PTj1 2.8 (72) 48.7 (57) 3.08 (75) 44.5 (53)
M-jet,-jet wind 2.1 (75) 26.6 (55) 2.5 (81) 22.3 (50)
ATLFAST
Number of events for 100fb-1 (percentage wrt previous cut)Now identical condition YPAR(93)=0.0, Φcut good agreement.
2003/9/22 Final Results on ttH (H->tau+tau) 18
4. Summary4. Summary Compared two analyses on ttH(H)
Tau hadronic mode: llb + jjb + hb + jjb + h + h + h -tag algorithm
ATLFTAU (50% eff. Fixed) - Unreasonable at low Pt. Problematic for ttH.
Weizmann algorithm - Ncell is a powerful parameter for tt rejection
but pile-up and noise should be taken into account. Full simulation with noise&pile-up under study.
ATLFAST (parametrized ATLFTAU)Good agreement between Japan and Israel results now.Discrepancies due to -jet charge assignment ,YPAR(93),Φ.
These are not critical for our final results …
2003/9/22 Final Results on ttH (H->tau+tau) 19
ttH (H+-)
t( l b ) + t( l b ) + ( h ) + ( l )
t(l b ) + t(jjb) + ( h ) + ( l )
Sig. Bkg. tt ttZ ttW ttH
2-lepton 11.5 16.7 6.7 4.1 4.5 1.4
3 lepton 3.7 2.4 0.3 1.1 0.3 0.7
Our Results for AthensL=300 fb-1 MH=115GeV/c2
For 2 300 fb-1
S/B = 0.8S/B = 4.5 (Poisson)
t(lb) + t(jjb) + (h)+ (h)Similar sensitivity as di-lepton channel,but suffers from irreducible ttZ, ttWW …background.