Susy Biweekly - truth mc study

8/13/2019 Susy Biweekly - truth mc study

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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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Susy Biweekly - truth mc study