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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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)
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
~ ~
~
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
GeV 50 EmissT
Reconstruction of 0
102
~ ~
~
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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:
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
reconstruction
02
~ 01
~
~maxM
GeV 92 M GeV 75
02
~
p
M
M1p
01
02
~
~
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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:
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Estimation of Mllbmax
02
~01
~
~b~
b
PYTHIA Signal
total
Lb~
Rb~
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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:
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Gluino Reconstruction
Etmiss > 50 GeV Et
miss > 100 GeV Etmiss > 150 GeV
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
66.6
GeV 9.2611.2bb)~M( 02
Gluino Reconstruction
Result of fit:
GeV 3.643)g~M( Generated mass:
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Combinatorial suppression
b)b~
( angle
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Estimation of
4.0cos
doesn’t depend on M(10) !
GeV 30)~M( 01
)b~
M(-)g~M(
)b~
M(-)g~M(
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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:
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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(
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
Point G
bb~
g~ pp
b~02
(26 %)
(44 %)
01
~ ~
(8.8 %)
GeV 140 M GeV 100
GeV 300 E
fb 60missT
-1
31/10/2001 Massimiliano Chiorboli CMS Physics Meeting
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(