# Citizen Science Episode 4

In this new episode of Citizen Science on Hive @lemouth introduce us to "Deciphering top quark production at CERN’s Large Hadron Collider".

All the steps including links to previous episodes can be found in his post:

For this new exercise i didn't encounter any problem, even if my "Virtualbox" asked for an update.

# Task 1: the event content

We have here to import the previously simulated events in MadAnalysis after starting it:

And generate an histogram displaying the content of the reconstructed events in terms of high-level objects:

ma5>set main.lumi = 140
ma5>plot NAPID
ma5>submit

Here is the graphical result:

ma5>open

I have a red color because i made a little mistake while importing but it doesn't change anything in the results.

# Task 2: Lepton and photon multiplicity

### In the first step of this task we first create a graphical view of the Leptons (l)

ma5>define l = l+ l-
ma5>plot N(l) 5 0 5

And a second after cleaning objets with ‘transverse momentum’ smaller than 20 GeV:
ma5>select (l) PT > 20
ma5>plot N(l) 5 0 5
ma5>plot NAPID
ma5>resubmit

We get this result after:
ma5>open

### In the second step of this task we do the same thing for Photons (a):

ma5>plot N(a) 5 0 5
ma5>select (a) PT > 20
ma5>plot N(a) 5 0 5
ma5>resubmit
ma5>open

With this result:

# Homework 1: Jet multiplicity

The homework consist in doing the same exercise for Jets (j) and B-Jets (b) with a different value for the cleaning: 25 GeV

So for Jets I entered in Mad5:

ma5>plot N(j) 5 0 5
ma5>select (j) PT > 25
ma5>plot N(j) 5 0 5
ma5>resubmit
ma5>open

With this result:

And for B-Jets I entered in Mad5:

ma5>plot N(b) 5 0 5
ma5>select (b) PT > 25
ma5>plot N(b) 5 0 5
ma5>resubmit
ma5>open

With this result:

For the question of the little variation, maybe we would have a greater with a greater value than 25.

# Task 3: Selection of a subset of all simulated collisions

We will focus here on events containing exactly one lepton.
So we enter the command:

ma5>select N(l)==1

The result is as expected, about 30% of the events have one lepton in the final state.

# Homework 2: Lepton multiplicity after the cut

We have now to study the effect of the above cut on the lepton multiplicity.

I entered the following code in Mad5:

ma5>plot N(l) 5 0 5
ma5>select N(l)==1
ma5>plot N(l) 5 0 5
ma5>resubmit
ma5>open

And got the result:

As we selected N (l) = 1 the result after the cut is in accordance, we have only the selected bar.

Here I had to update Ma5 because i had errors in the output so I entered:

ma5>exit
git pull
ma5>set ttbar.xsection = 505.491
ma5>set main.lumi = 140
ma5>plot NAPID
ma5>submit
ma5>open
ma5>define l = l+ l-

I'm not sure if the last lines were necessary but in doubt.

Now my graphical bars will be in blue.

In this task we create two histograms to study the transverse momentum (PT) and the absolute value of the pseudo-rapidity (ABSETA) of the Lepton (l) by entering the commands:

ma5>plot PT(l) 25 0 200 [logY]
ma5>plot ABSETA(l) 25 0 2.5 [logY]
ma5>resubmit
ma5>open

With the result:

In the next task we investigate the mass (M) of the two most energetic Jets in the event's final state with the command:

ma5>plot M(j[1] j[2]) 50 0 250 [logY]
ma5>resubmit
ma5>open

We get this result:

And we have the peak at about 80 GeV as expected.

# Homework 3: Missing transverse energy spectrum

I am a bit lost but intuitively I wanted to try the following commands:

ma5>plot PT(j[1] j[2]) 25 0 250 [logY]
ma5>resubmit
ma5>open

With this graphical result:

That doesn't get me any further in the question but I wanted to try.

H2
H3
H4
3 columns
2 columns
1 column