susy biweekly - truth mc study
TRANSCRIPT
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Boosted Topologies in stop decays
Truth Montecarlo studies for boosted decays of stop quark
Pierfrancesco Butti
NIKHEF
November 28, 2013
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Motivations
Motivations
Interest in moving to a b-tagging analysis
Two main area of possible work:
b-tagging in high pT jetsb-tagging for boosted topologies
Easy to understand the importance of the high-pT b-tagging in Susy
We are interested in knowing if Susy Stop decays present boostedtopologies in the final state
We would like to investigate the following channelst b+
t t+ 0
b t+
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introduction
What is a boosted topology?
Consider: t t+01Ifmt mt and mt m01large amount of energy is
given to the top quark,making it kinematicallyboostedIn the COM
Et =m2t m
2
01
+ m2t
2mt
In the LAB dependence onP
t
Similar in the b t+
channel
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Introduction
Expected final state
There is a possibility ofcollimated decay products (qqborbl)
Partial or full merging of thejets into the radius of a singlefat jet
The angular separation of thedecay products is approximatelyR 2m
pT
The use of large cone-size jetsis motivated by a R
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Introduction
We set up a truth MC study to investigate the kinematics of thedecay
The goal is to understand if all decays present a boosted topology. If
yes in which part of the grid
Disclaimer:
The study has just started
Very preliminary results
Investigated only the t b+
Possible presence of mistakes
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MC samples and Event Selection
t b+ process
Samples used:mc12_8TeV.*.MadGraphPythia_AUET2B_CTEQ6L1_t*_c*_n*_LeptonFilter.merge.
NTUP_TRUTH.e2094_p1581
Interested only on the Initial State (beforeshowering)Selection of the events:
Nlep = 1 (e,,) (mc_status == 3)
plepT >25 GeV, |
lep|
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MC truth display
Structure of an event
HS,showered,stable particles
We stopped to the HS for the moment
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Check distributions - mt = 700 GeV , m = 200 GeV
Check on
stop distri-butions
Stopproducedcentrally
Stop pair
producedback toback
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Check distributions - mt = 700 GeV , m = 200 GeV
Check on
lep andquarks dis-tributions
bs pT dis-tributionsagree
Nothing toreport
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Rplots - mt = 700 GeV , m = 200 GeV
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Grids for t b+
Grids for
R(b,
/W)Minimum value onthe diagonal
Soft , soft b,energetic W.
R(b,) depends
on the boost by ptT
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Grids for t b+
Grids for
R(b, q1/q2)Minimum value onthe diagonal
Soft , soft b,energetic W.
R(b,) depends
on the boost by ptT
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Grids for t b+
Grids for
R(q1, q2)Minimum value onthe top right corner
Hint for semiboosted topology
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Issues
Noticed that the pTof the t increases athigher masses
I was expecting theother way around.
This could be due
to the fact that thetare produced morecentrally at highermasses
A check on themomentum
magnitude gives thesame result
This could have
impact on the R
distributions since
there is correlation
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Conclusions and Future Work
We showed thePRELIMINARYresults of the truth study onboosted topologies
The study doesnt take into account any showering contribution andreconstruction level
An unexpected behaviour of the pTdistribution as a function of the
tmass has been seen. More investigation probably is requiredHint for boosted topologies on the diagonal and top right corner ofthe grid.
Future Work
The top+LSP topology has already been studied in detail for thedirect stop note. Good exercise to repeat though.
Check the b t+ . Little bit more complicated topology
Move to work on NTUP SUSY with more info available.
Check the pTof the t.
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