Progress on SUSY particles reconstruction methods Massimiliano Chiorboli Università di Catania.
Transcript of Progress on SUSY particles reconstruction methods Massimiliano Chiorboli Università di Catania.
Progress on SUSY particles reconstruction methods
Massimiliano Chiorboli
Università di Catania
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
mSUGRA Points
Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204)
High total SUSY cross section
we can try to reconstruct masses with low integrated luminosity
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Point B
m0 100 GeV
m1/2 250 GeV
tan 10
A0 0
sign +
g 643.3 tL 412.5
bL 522.5 tR 600.5
bR 549.7 40 379.1
qL 570 30 358.8
qR 549 20 186.8
lL 211.4 2± 379.7
lR 145.8 1± 186.0
10 = LSP 99.6
pb 41.41TOTSUSY
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Decay chain and event topology
bb~
g~ pp
b~02
01
~
(26 %)
(35 %)
(0.2 %)
01
~ ~
(60 %)
p
p
g~
b~
b
b
01
~
02
~ ~
Event final state:
• 2 high pt isolated leptons OS
• 2 high pt b jets
• missing Et
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Events Production
• SPYTHIA (PYTHIA 6.136)• CMSJET 4.703
-1fb 10
SUSY (10 fb-1)ll 3912
17522
g 4420
gg 42809
q 14895
qg 192400
tt 15587
qq 108849
qb 3423
bb 5959
bg 4280
Total 414056
SMtt 6.2×106 (= 10 fb-1)
Z+jet (pthat >60) 8×106 (< 10 fb-1)
W+jet (pthat >60) 3×106 (< 10 fb-1)
ZZ,WW,ZW 2×106 (> 10 fb-1)
No pile-up
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Events selection
• at least 2 isolated leptons with pt>10 GeV and ||<2.5
• at least 2 b-jets with pt>15 GeV and ||<2
SUSY (10 fb-1) %ll 0
13 0.07
g 104 2.3
gg 1753 4.1
q 25 0.16
qg 3387 1.8
tt 525 3.3
qq 138 0.1
qb 90 2.6
bb 542 9.0
bg 272 6.4
SMtt 20770 (0.04 %)
Z+jet (pthat >60) 68 ( /106)
W+jet (pthat >60) 0 ( /106)
ZZ,WW,ZW 32 ( /106)
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Reconstruction of 0
102
~ ~
~
GeV 32.85 M
)MM)(MM(M
~
2~
2~
2~
2~
max01
02
SUSY SM SUSY + SM
PYTHIA Signal
CMSJET
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Subtracting invariant mass of OSOF pairs eliminate tt and combinatorial bkg, but not Z+jet
Other cuts
Reconstruction of 0
102
~ ~
~
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GeV 50 EmissT
Reconstruction of 0
102
~ ~
~
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GeV 1.64 86.00 Mmax
GeV 32.85 M
)MM)(MM(M
~
2~
2~
2~
2~
max01
02
01
02
~ ~
~Reconstruction of
Result of fit:
Generated value:
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reconstruction
02
~ 01
~
~maxM
GeV 92 M GeV 75
02
~
p
M
M1p
01
02
~
~
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Sbottom reconstruction
reconstructed neutralino combined with the most energetic b-jet, assuming Mknown
SUSY Signal
SUSY bkg
qg qq
gg q
g
bb tt
bg ll
qb
Cutting on Etmiss allows to suppress the SM bkg
GeV 50 EmissT
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
2 sbottoms
Etmiss > 100 GeV Et
miss > 150 GeV
we can’t resolve the 2 peaks
GeV 549.7 b~
GeV 522.5 b~
R
L
Sbottom reconstruction
10 fb-1
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M(b) estimation
47.5
GeV 6.6509.5b)~M( 02
GeV 7.549)b~
M(
GeV 5.522)b~
M(
R
L
Result of fit:
Generated masses:
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Estimation of Mllbmax
02
~01
~
~b~
b
PYTHIA Signal
total
Lb~
Rb~
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GeV 38.11.364Mmaxb
GeV 12.844 M
)MM)(MM(M
02
01
02
02L
~
2~
2~
2~
2
b~
max
b
GeV 37.504 M
)MM)(MM(M
02
01
02
02R
~
2~
2~
2~
2
b~
max
b
Estimation of Mllbmax
GeV 50EmissT
Result of fit:
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Gluino Reconstruction
SUSY Signal
SUSY bkg
qg qq
gg q
g
bg tt
ll
bb
qb
Another b-jet is associated to the recostructed sbottom
b)b~
( angle
the b-jet closest in angle to the
reconstructed sbottom is chosen
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Gluino Reconstruction
Etmiss > 50 GeV Et
miss > 100 GeV Etmiss > 150 GeV
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66.6
GeV 9.2611.2bb)~M( 02
Gluino Reconstruction
Result of fit:
GeV 3.643)g~M( Generated mass:
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Combinatorial suppression
b)b~
( angle
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Gluino after angle cut
4.0cos
8.0cos
71.0
GeV 9.6604.6bb)~M( 02
66.9
GeV 13.3597.4bb)~M( 02
10 fb-1
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Sbottom after angle cut
4.0cos
8.0cos
50.5
GeV 8.5502.4b)~M( 02
56.9
GeV 8.6511.8b)~M( 02
10 fb-1
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Estimation of
4.0cos
doesn’t depend on M(10) !
GeV 30)~M( 01
)b~
M(-)g~M(
)b~
M(-)g~M(
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30.8
GeV 5.80.78b)~M(bb)~M( 02
02
4.0cos
GeV 6.93)b~
M(-)g~M(
GeV 8.120)b~
M(-)g~M(
R
L
Estimation of )b~
M(-)g~M(
Result of fit:
From the model:
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Sbottom and Gluino reconstruction With 40 fb-1
49.7
GeV 3.9514.5b)~M( 02
68.2
GeV 5.4615.4bb)~M( 02
No angle cutssbottom gluino
Only SUSYEtmiss > 150 GeV
GeV 3. 643 ) g~ M(GeV 7.549)b
~M(
GeV 5.522)b~
M(
R
L
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With 40 fb-1
4.0cos
8.0cos
53.4
GeV 4.4506.6b)~M( 02
50.4
GeV 8.3519.3b)~M( 02
sbottom
GeV 7.549)b~
M(
GeV 5.522)b~
M(
R
L
Generated values
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With 40 fb-1
4.0cos
8.0cos
70.4
GeV 5.6607.8bb)~M( 02
72.8
GeV 9.1611.2bb)~M( 02
gluino
Generated value GeV 3. 643 ) g~ M(
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
With 40 fb-1
1.72
GeV 2.11.69b)~M(bb)~M( 02
02
.542
GeV 3.90.94b)~M(bb)~M( 02
02
no cut 4.0cos )b~
M(-)g~M(
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Point G
+sign
0A0
20tan
375 GeVm1/2
120 GeVm0
152.510 = LSP
294.51±193.4lR
546.12±299.6lL
294.820780qR
532.430814qL
545.340771.3bR
800.8tR723.0bL
589.4tL919.8g
pb 6.00TOTSUSY
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Point G
bb~
g~ pp
b~02
(26 %)
(44 %)
01
~ ~
(8.8 %)
GeV 140 M GeV 100
GeV 300 E
fb 60missT
-1
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Conclusions
• estimation of M(l+l-)max
• estimation of M(l+l-b)max
• sbottom reconstruction with Resol. ~ 10 %, but 2 sbottoms not resolved
• gluino reconstruction with Resol. ~ 12 %
• M(g) - M(b) estimation, independent from M(10), with Err ~ 7 %
Point B, with 10 fb-1
Point G, with 60 fb-1
• No sbottom reconstruction, needs more investigation
~2~
2~
2~
2~ M)MM)(MM( 0
102
02
01
02
02R
~2~
2~
2~
2
b~ M)MM)(MM(