Progress for search of neutral Supersymmetric Higgs boson h/A bb h 0 /A (h 0 /A m + m - )

Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni NicolettiHiggs Meeting 14 December 2005,CERN.

Progress for search of neutralSupersymmetric Higgs boson h/A

bb h0/A (h0/A Halina Bilokon, Vitaliano Chiarella, Simonetta Gentile, Giovanni Nicoletti

Laboratori Nazionali di Frascati, Università di Roma

La Sapienza, INFN


OutlinePreselectionSelection :• b-tag• muons• b-jets • Invariant mass • -isolation

Conclusions & planning

Background: •bb Z→•tt → bb •ZZ → bb

• Top decay: 100% t bW


SelectionPreselection cuts: At least a pair of opposite muons with pt > 10 GeV and || < 2.5At least a pair of jets with ET > 10 GeV and < 2.5SelectionAt least 1 b-jets (pT > 15 GeV & b-tag weight>1) ET miss < 45 GeV 25 GeV < PT 1 < 95 GeV 20 GeV < PT 2 < 60 GeV for tt background

Final CutMinv( +-) +/- M (A0, h0, m) ( m= exp. mass res.)

Isolation PTtrack < 5 GeV around a cone R<0.2

PTb2 < 40 GeV

PTb1 < 70 GeV


Sample particle L =30 fb-1 sample

h0 6000 5999

A0 7000 7000

Zbb 6.8 x 105 340502*

tt 1.7 104 170110

ZZ 3.8 x 103 3788

130 fbLdt

*Corresponding to half luminosity


Number of muons: no cut MC distributions Reconstracted

Distribution

h0 A

bbZ→ tt ZZ

x 0.5

N 2


PT of muons: no cut MC , reconstructed distributions

tt :

peaked at

lower PT values

h0

tt ZZ

x 0.5

bbZ→

pT > 10 GeV


particle L =30 fb-1 sample pair

h0 6000 5999 3643(61%)

A0 7000 7000 4332(62%)

Zbb 6.8 x 105 340502* 206629 (61%)

tt 1.7 104 170110 114718(67%)

ZZ 3.8 x 103 3788 1780(47%)


•At least a pair of + - with pt > 10 GeV < 2.5


Number of jets: after 1 cut MC distributions Reconstructed

distribution

x 0.5

Ah0

ttbbZ→

x 0.5

ZZ

Njet 2


particle L =30 fb-1 sample pair jets

h0 6000 5999 3643(61%)

1758(29%)

A0 7000 7000 4332(62%)

2178(31%)

Zbb 6.8 x 105 340502* 206629 (61%)

127099(37%)

tt 1.7 104 170110 114718(67%)

107075(63%)

ZZ 3.8 x 103 3788 1780(47%)

1470(39%)


•A pair of jetswith pt > 10 GeV |η| < 2.5

PRESELECTION


After preselection: Number of Jets (R=0.7)

tt

Ah0

bbZ→

Nev

Nev

Nev

Nev

Njet

Njet

Njet

Njet


After preselection: jets pT (R=0.7)

h0 A

bbZ→

tt

Nev

Nev Nev

Nev

PT(MeV) PT(MeV)

PT(MeV) PT(MeV)

<pT> ~25 MeV <pT> ~26 MeV

<pT> ~35 MeV <pT> ~53 MeV


particle initial preselect

ionb-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%)


•At least 1 b-jets (pT > 15 GeV & b-tag weight>1)


After b-tag cut: ETmiss

h0 A

bbZ→

tt

ET miss < 45 GeV<ET>= 21.8 GeV

<ET>= 27.5 GeV

<ET>= 23.7 GeV

<ET>= 67.1 GeV



ionb-tag ET

miss

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%)


• ETmiss < 45 GeV


After ETmiss:

the most energetic PT1

h0

bbZ→ tt

x 0.5

25 GeV<pT 1 < 95 GeVA



ionb-tag ET

miss pT1

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%)


• 25 GeV<pT1 < 95 GeV


After PT1 :the

2nd most energetic PT2

h0

ttbbZ→

x 0.5

20 GeV<pT 1 < 60 GeV

Ah0

tt


particle initial presele

ctionb-tag ET

miss pT1 pT

2

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%)*Corresponding to half luminosity

• 20 GeV<pT1 < 60 GeV


After PT cut:

2nd most energetic b PTb2

pT b < 40 GeV

bbZ→

x 0.5

Ah0

tt


particle

initial preselection

b-tag ETmiss pT

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

• pTb < 40 GeV


After PTb cut:

most energetic b PTb1

pT b < 70 GeV

h0 A

x 0.5

bbZ→ tt


particle


b-tag ETmiss pT

pTb2 pT

b1

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%)


• pTb < 70 GeV


After tt cuts:Invariant mass distributions

bbZ→

x 0.5

h0

tt

A


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 chosenprobability: (e.g. f =2) Where tot

h0 =3.31 GeV totA = 4.28 GeV

m= 2.6% measured at Z mass

21

2

2

/ 36.2/0

0

m

TOT

Ah

Ahfkm


Invariant mass

Fit results are consistent with detector mass resolution and natural with of particle

h0 A

bbZ→x 0.5

tt


particle


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%)


• |Minv|< |Mh/A± window|


After invariant mass cut:isolationPT for tracks in R < 0.2

PT < 5 GeVsee Louis FloresPresentation Atlas week 28.10.05

h0

tt

PT < 5 GeV


particle


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%)


• Isolation PT < 5 GeV


Conclusions

The possibility for a discovery of the neutral MSSM Higgs in bb A/h0 →has been investigated in a test point of MSSM parameter space (tan, mA): mA=110.3 GeV, mh0

=109.25 GeV

A study with considering Zbb, tt, and ZZ background led to a significance

130 fbLdt

15B

S


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 (tan, mA) plane

b-tag improvement (difficult)

Credit to Giovanni Nicoletti.without him this work can never done


Riserve


after 1 cut

x 0.5

bbZ→ bbZ→

x 0.5tt

tt


Study of sample: JetsZ → + -h0→ + -

<ET gen> ~ 20 GeV <ET gen> ~ 26 GeV

Number of jets Number of jets

ET jets ET jets

Progress for search of neutral Supersymmetric Higgs boson h/A bb h 0 /A (h 0 /A m + m - )

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