Alain Romeyer - January 20051 Light higgs decay in SUSY cascade - Status report Introduction Trigger...
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Transcript of Alain Romeyer - January 20051 Light higgs decay in SUSY cascade - Status report Introduction Trigger...
Alain Romeyer - January 2005 1
Light higgs decay in SUSY cascade - Status report
Introduction
Trigger efficiency
B tagging
Jet calibration
Invariant mass reconstruction
Likelihood fit
Conclusion
Filip Moortgat (CERN)Alain Romeyer (Mons - Belgium)
Alain Romeyer - January 2005 2
Introduction
Signature :h0
01χ LSP
MET
b
bB tagging
02χ
q / g
Benchmark point LM5Tan = 10AO = 0µ > 0M1/2 = 360 GeVM0 = 230 GeV
MSUGRA 5 parameters : m0, m1/2, A, tan , sign(µ)
S. Abdullin – L. Pape Update II of the new MSUGRA test points proposal
0 02 1
0 0
g
q
χ χ
H h
m ~ 860GeV
m ~ 800 GeV
m ~ 273 GeV m ~ 142 GeV
m ~ 570 GeV m ~ 116 GeV
Alain Romeyer - January 2005 3
Simulated events Production of signal events and pile-
up
Signal events : all SUSY channel (easier for later event reweighting)
~20% contains our decay chain
Digitisation : merge pile-up and signal
official 100 000 evts production at CERNavailable
our reconstruction strategy launched on digis
First results
Isajet 7.69 +
Pythia 6220
+ CMKIN
OSCAR2_4_6
ORCA7_6_1
generator
simulation
digitisationFU
LL S
IMU
LA
TIO
N C
HA
IN
Alain Romeyer - January 2005 4
« Reconstruction » strategy ORCA_8_6_1
Simulatedevents I – L1 +HLT
ReconstructionII - Jet Reconstruction :
• Iterative Cone Algo.• cone size : 0.5• tower Et thr. : 0.5 GeV • seed Et thr. : 1 GeV
III - B tagging : • By Track Counting• Number of tracks above minimum significance : 2
MET : • MET from EcalHcalTower
Analysis
• event selection• IV - b ̅b inv mass reco.
Efficiency ?
Jet sel.Pt > 10 GeV
Alain Romeyer - January 2005 5
Trigger efficiencyGenerated HLT
100 000 96 462 (19 338)
L1 : 99.9 % - HLT : 96 %
~ all events !!!
Trigger Condition (GeV) % of evts
1 jet Et > 571 23.5
3 jets Et > 209 21.7
4 jets Et > 122 32.7
B jet 1 Jet Et > 237 77.4
MET calo1 jet > 180 GeV + MET
> 123 79.5
MET jets1 jet > 180 GeV + MET
> 123 79.8
Low
Lum
i.
Caveat : ~ same efficiency for SUSY bkg.
Non cumulative Trigger !!!
Alain Romeyer - January 2005 6
Btagging
Number of jets
Number of tagged jets
Efficiency /
Inefficicency (%)
b 95593 47310 49.5
u 123 807 9408 7.6
d 97409 7957 8.2
c 50728 9103 17.9
Global efficiency : 49.5 % Global inefficiency : 9.4 %
Nhiggs = Nhiggs after HLT * ( Btag Eff. )² ~ 4700 evts
Track Counting Algo. (default setting)
Need to be optimised Filip
Alain Romeyer - January 2005 7
Efficiency / inefficiency
Alain Romeyer - January 2005 8
Efficiency / inefficiency…
Alain Romeyer - January 2005 9
Select b jets from h0
Select only b jets coming from h0 decay
No jet energy calibration (from parton content in a 0.3 cone)
Alain Romeyer - January 2005 10
Jet reconstruction accuracy
Alain Romeyer - January 2005 11
Jet calibration
Jet calibration method following CMS-note 1999/066
Association between rec. Jets and generated partons before hadro. (cone < 0.3)
2 types of jets : b jets and other Etrue
jet = sum(Equarks,gluons) Correction Factor C = Etrue
jets / Erecjets
Fit of the correction factor surface in the E vs || plane :
21 a
1 3 43
22
f(|η|)C η, E = +
E
f(|η|) = + |η|+ |η|
a
b b b b+ |η|
Alain Romeyer - January 2005 12
E correction for b jets
Alain Romeyer - January 2005 13
E correction for non b jets
Same operation is done with the jet momentum
Alain Romeyer - January 2005 14
Impact on Minv Select only b jets coming from h0 decay
Calibrated jets
Alain Romeyer - January 2005 15
Impact on jet reco. accuracy
Alain Romeyer - January 2005 16
Invariant mass (no cuts)
Alain Romeyer - January 2005 17
Likelihood fit Follow the Z’ µµ strategy (CMS AN 2004/018) Unbinned method
No constraints on the absolute background level only on the background shape
3 parameters : mh, and
S Sh s h bg h
tot. tot.
N NP(m )= P (m ,σ) + [1 - ] P (m )
N N
Fraction of signal NormalisedGaussian
Extract from background fit
S
tot.
N
N
Alain Romeyer - January 2005 18
Fit result (full stat)
S+BS = 2 ln 14.1 B
LL
Unbinned fi
t
Binned o
nly w
hen plo
tted
Alain Romeyer - January 2005 19
Various running time
50 000 evts – S = 10.9
25 000 evts – S = 7.9515 000 evts – S = 5.8
100 000 evts – S = 14.1
Alain Romeyer - January 2005 20
Conclusion For the first time the full analysis chain is working
higgs peak visible with significance above 5 ~15000 evts (~ 40 days of understood data)
Future : Include SM background Improve S/B ratio (cuts, b tagging optimisation…) Reduce the width of the invariant mass Run the code on the Zbb sample for cross check and
optimisation of the reconstruction strategy Fast simulation (FAMOS) in order to explore the SUSY
parameter phase space Contour plot for the CMS reach