1. Progress for search of neutral Supersymmetric Higgs boson h/A
bb h0/A (h0/A  m+m-)
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Laboratori Nazionali di Frascati, Università di Roma
La Sapienza, INFN
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

2. Higgs Meeting 14 December 2005,CERN.
Outline
Preselection
Selection :
b-tag
muons
b-jets
Invariant mass
m -isolation
Conclusions & planning
Top decay:  100% t  bW
Background:
bb Z→ m m
tt → bb m m
ZZ → bb m m m n
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

3. Higgs Meeting 14 December 2005,CERN.
Selection
Preselection cuts:
At least a pair of opposite muons with pt > 10 GeV
and |h| < 2.5
At least a pair of jets with ET > 10 GeV and |h| < 2.5
Selection
At least 1 b-jets (pT > 15 GeV & b-tag weight>1)
ET miss < 45 GeV
25 GeV < PT m1 < 95 GeV
20 GeV < PT m2 < 60 GeV
for tt background
PTb2 < 40 GeV
PTb1 < 70 GeV
Final Cut
Minv( m+m-) /- DM (GA0, Gh0, sm) ( sm= exp. mass res.)
Isolation SPTtrack < 5 GeV around a cone DR<0.2
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

4. Higgs Meeting 14 December 2005,CERN.
Sample
particle
L =30 fb-1
sample h0
6000
5999 A0
7000
Zbb
6.8 x 105
340502* tt
170110 ZZ
3.8 x 103
3788
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

5. Higgs Meeting 14 December 2005,CERN.
Number of muons: no cut Nm
MC distributions
Reconstracted
Distribution h0 A
bbZ→mm tt ZZ
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

6. Higgs Meeting 14 December 2005,CERN.
PT of muons: no cut
pT m> 10 GeV
MC , reconstructed distributions
tt :
peaked at
lower PT m values h0
bbZ→mm tt ZZ
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

7. Higgs Meeting 14 December 2005,CERN.
At least a pair of m+ m- with pt > 10 GeV |h| < 2.5
particle
L =30 fb-1
sample
m pair h0
6000
5999
3643
(61%) A0
7000
4332
(62%)
Zbb
6.8 x 105
340502*
(61%) tt
170110
114718
(67%) ZZ
3.8 x 103
3788
1780
(47%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

8. Number of jets: after 1 cut
Njet
MC distributions
Reconstructed
distribution h0 A tt ZZ
bbZ→mm
x 0.5
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

9. Higgs Meeting 14 December 2005,CERN.
A pair of jets with pt > 10 GeV |η| < 2.5 P R E S L C T I O N
particle
L =30 fb-1
sample
m pair
jets h0
6000
5999
3643
(61%)
1758
(29%) A0
7000
4332
(62%)
2178
(31%)
Zbb
6.8 x 105
340502*
(61%)
127099
(37%) tt
170110
114718
(67%)
107075
(63%) ZZ
3.8 x 103
3788
1780
(47%)
1470
(39%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

10. After preselection: Number of Jets (DR=0.7)
Nev
Nev h0 A
Njet
Njet
Nev
Nev
bbZ→mm tt
Njet
Njet
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

11. After preselection: jets pT (DR=0.7)
Nev h0 A
Nev
<pT> ~25 MeV
<pT> ~26 MeV
Nev
PT(MeV)
Nev
PT(MeV)
bbZ→mm tt
<pT> ~53 MeV
<pT> ~35 MeV
PT(MeV)
PT(MeV)
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

12. Higgs Meeting 14 December 2005,CERN.
At least 1 b-jets (pT > 15 GeV & b-tag weight>1)
particle
initial
preselection
b-tag h0
5999
1758
(29%)
572
(9.5%) A0
7000
2178
(31%)
751
(10.7%)
Zbb
340502*
127099
(37%)
62812
(18.4%) tt
170110
107075
(63%)
89684
(52.7%) ZZ
3788
1470
(39%)
1042
(27.5%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

13. After b-tag cut: ETmissn
After b-tag cut: ETmiss
ET miss < 45 GeV h0 A
<ET>= 21.8 GeV
<ET>= 23.7 GeV
bbZ→mm tt
<ET>= 67.1 GeV
<ET>= 27.5 GeV
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

14. Higgs Meeting 14 December 2005,CERN.
ETmiss < 45 GeV
particle
initial
preselection
b-tag
ETmiss h0
5999
1758
(29%)
572
(9.5%)
526
(8.8%) A0
7000
2178
(31%)
751
(10.7%)
675
(9.6%)
Zbb
340502*
127099
(37%)
62812
(18.4%)
52012
(15.2%) tt
170110
107075
(63%)
89684
(52.7%)
24180
(14.2%) ZZ
3788
1470
(39%)
1042
(27.5%)
885
(23.3%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

15. After ETmiss: the most energetic m PTm1
25 GeV<pT m1 < 95 GeV h0 A tt
bbZ→mm
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

16. Higgs Meeting 14 December 2005,CERN.
25 GeV<pTm1 < 95 GeV
particle
initial
preselection
b-tag
ETmiss
pTm1 h0
5999
1758
(29%)
572
(9.5%)
526
(8.8%)
464
(7.7%) A0
7000
2178
(31%)
751
(10.7%)
675
(9.6%)
597
(8.5%)
Zbb
340502*
127099
(37%)
62812
(18.4%)
52012
(15.2%)
43100
(12.6%) tt
170110
107075
(63%)
89684
(52.7%)
24180
(14.2%)
17928
(10.5%) ZZ
3788
1470
(39%)
1042
(27.5%)
885
(23.3%)
690
(18.2%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

17. After PTm1 :the 2nd most energetic m PTm2
20 GeV<pT m1 < 60 GeV h0 A h0
bbZ→mm tt tt
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

18. Higgs Meeting 14 December 2005,CERN.
20 GeV<pTm1 < 60 GeV
particle
initial
preselection
b-tag
ETmiss
pTm1
pTm2 h0
5999
1758
(29%)
572
(9.5%)
526
(8.8%)
464
(7.7%)
427
(7.1%) A0
7000
2178
(31%)
751
(10.7%)
675
(9.6%)
597
(8.5%)
536
(7.6%)
Zbb
340502*
127099
(37%)
62812
(18.4%)
52012
(15.2%)
43100
(12.6%)
36212 (10.6%) tt
170110
107075
(63%)
89684
(52%)
24180
(14.2%)
17928
(10.5%)
13545 (7.9%) ZZ
3788
1470
(39%)
1042
(27.5%)
885
(23.3%)
690
(18.2%)
589
(15.5%)
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.
*Corresponding to half luminosity

19. After PTm cut: 2nd most energetic b PTb2
pT b2 < 40 GeV A h0
bbZ→mm tt
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

20. Higgs Meeting 14 December 2005,CERN.
pTb2 < 40 GeV
particle
initial
preselection
b-tag
ETmiss
pTm
pTb2 h0
5999
1758
(29%)
572
(9.5%)
526
(8.8%)
427
(7.1%)
386 (6.5%) A0
7000
2178
(31%)
751
(10.7%)
675
(9.6%)
536
(7.6%)
492 (7.0%)
Zbb
340502*
127099
(37%)
62812
(18.4%)
52012
(15%)
36212 (10.6%)
24067 (7.0%) tt
170110
107075
(63%)
89684
(52%)
24180
(14%)
13545 (7.9%)
3983 (2.3%) ZZ
3788
1470
(39%)
1042
(27.5%)
885
(23%)
589
(15.5%)
406 (10.7%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

21. After PTb2 cut: most energetic b PTb1
pT b1 < 70 GeV h0 A
bbZ→mm tt
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

22. Higgs Meeting 14 December 2005,CERN.
pTb1 < 70 GeV
particle
initial
preselection
b-tag
ETmiss
pTm
pTb2
pTb1 h0
5999
1758
(29%)
572
(9.5%)
526
(8.8%)
427
(7.1%)
386 (6.5%)
356 (6.0%) A0
7000
2178
(31%)
751
(10.7%)
675
(9.6%)
536
(7.6%)
492 (7.0%)
441 (6.3%)
Zbb
340502*
127099
(37%)
62812
(18.4%)
52012
(15%)
36212 (10%)
24067 (7.0%)
20473 (6.0%) tt
170110
107075
(63%)
89684
(52%)
24180
(14%)
13545 (8.0%)
3983 (2.3%)
2438 (1.4%) ZZ
3788
1470
(39%)
1042
(27.5%)
885
(23%)
589
(15.5%)
406 (10.7%)
334 (8.8%)
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.
*Corresponding to half luminosity

23. After tt cuts:Invariant mass distributionsh0 A
bbZ→mm tt
x 0.5
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

24. Higgs Meeting 14 December 2005,CERN.
Mass selection window
Fit results are consistent with detector mass resolution and natural with of particle
k = -820 MeV measured at Z mass
f = standard deviation fraction corresponding to chosen
probability: (e.g. f =2)
Where G toth0 =3.31 GeV G totA = 4.28 GeV
s m= 2.6% measured at Z mass
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

25. Higgs Meeting 14 December 2005,CERN.
Invariant mass h0 A
bbZ→mm tt
x 0.5
Fit results are consistent with detector mass resolution
and natural with of particle
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

26. Higgs Meeting 14 December 2005,CERN.
|Minv|< |Mh/A± window|
particle
initial
preselection
b-tag
tt cut
Minv h0
5999
1758
(29%)
572
(9.5%)
356 (6.0%)
245
(4.0%) A0
7000
2178
(31%)
751
(10.7%)
441 (6.3%)
293
(4.1%)
Zbb
340502*
127099
(37%)
62812
(18.4%)
20473 (6.0%)
490
(0.1%) tt
170110
107075
(63%)
89684
(52.7%)
2438 (1.4%)
323
(0.2%) ZZ
3788
1470
(39%)
1042
(27.5%)
334 (88.8%) 9
(0.02%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

27. After invariant mass cut:isolation
SPT for tracks in D R < 0.2
SPT < 5 GeV
see Louis Flores
Presentation Atlas week
SPT < 5 GeV tt h0
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

28. Higgs Meeting 14 December 2005,CERN.
Isolation SPT < 5 GeV
particle
initial
preselection
b-tag
tt cut
Minv
isol h0
5999
1758
(29%)
572
(9.5%)
356 (6.0%)
245
(4.0%)
243 (4.0%) A0
7000
2178
(31%)
751
(10.7%)
441 (6.3%)
293
(4.1%)
291 (4.1%)
Zbb
340502*
127099
(37%)
62812
(18.4%)
20473 (6.0%)
490
(0.4%)
465 (0.1%) tt
170110
107075
(63%)
89684
(52%)
2438 (1.4%)
323
(0.3%)
306 (0.2%) ZZ
3788
1470
(39%)
1042
(27.5%)
334 (8.8%) 9
(0.02%)
8 (0.02%)
*Corresponding to half luminosity
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

29. Higgs Meeting 14 December 2005,CERN.
Conclusions
The possibility for a discovery of the neutral MSSM Higgs in bb A/h0 →mm has been investigated in a test point of MSSM parameter space (tanb, mA): mA=110.3 GeV, mh0 = GeV
A study with considering Zbb, tt, and ZZ background led to a significance
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

30. Higgs Meeting 14 December 2005,CERN.
Next future
Background subtraction method using
bbZ→ e+ e- sample
Consider other possible discriminator variable
Develop an estimator in order to approach a near possible the Z peak
Scan (tanb, mA) plane
b-tag improvement (difficult)
Credit to Giovanni Nicoletti.
without him this work can never done
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

31. Higgs Meeting 14 December 2005,CERN.
Riserve
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

32. Higgs Meeting 14 December 2005,CERN.
after 1 cut
bbZ→mm
bbZ→mm tt
x 0.5
x 0.5 tt
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.

33. Higgs Meeting 14 December 2005,CERN.
Study of sample: Jets
h0→ m+ m-
Z → m+ m-
Number of jets
Number of jets
<ET gen> ~ 20 GeV
<ET gen> ~ 26 GeV
ET jets
ET jets
Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti
Higgs Meeting 14 December 2005,CERN.