Looking into mu/pi separation in the ECAL. HPgTPC Meeting Eldwan - - PowerPoint PPT Presentation

Looking into mu/pi separation in the ECAL.

Eldwan Brianne DESY Hamburg, 03rd September 2019

HPgTPC Meeting

Motivation.

2 Page

A hard task

Eldwan Brianne | HPgTPC meeting | 03/09/2019

• Started to look into pions and muons in the ECAL
• Theoretically
• ECAL thickness ~ 1
• The probability to interact before reaching a

distance d

• In the ECAL,

➠ about 37% will look like muons

• May slightly depend on the particle energy

(cross-section rises at low energies)

• How do they look like?
• Can we distinguish them with the ECAL only?

λπ

P = ∫

d

p(l)dl = 1 − exp (− d λ )

P(λ) = 63.2 %

e− π0 γ

γ

e+ γ π− n π+ π− π− ¯ νμ μ− π+

EM component Hadronic component

Absorber

λπ

Parameters of the study.

3 Page

To set the context

Eldwan Brianne | HPgTPC meeting | 03/09/2019

• Uses the current MPD geometry available in GArSoft
• 80 layers of 2 mm Cu in the Barrel
• Looked only in the Barrel
• Shoot muons/pions between 0.5 and 5 GeV at various theta angles

and positions in the HPgTPC (energy gaussian distributed with 0.16 GeV smearing)

• 25k events per energy point
• Looked only at the simulation level (easier to track particle and type
• f interaction)
• Classified pions in three categories
• Punch-through (just going through the ECAL)
• Based on interaction hardness criterium ➠
• Hard interaction
• Soft interaction

i

∑

daughters

Ei − Eleading > 0.33 × Emother

Interaction probability.

4 Page

Is it as expected?

Eldwan Brianne | HPgTPC meeting | 03/09/2019

• Interaction Probability
• As expected 20 - 30% of the pions don’t interact (or too soft

interaction) in the ECAL

• ➠ Will be the hard ones to spot!
• ➠ Look at the difference between all categories and compare

to muons

• Number of hits
• Energy sum
• Hit energy
• Hit radius
• More ideas to look at?

1 2 3 4 5

Energy [GeV]

10 20 30 40 50 60 70 80 90 100

Probability [%]

Interacting Pions Punch-through and soft Pions

500 1000 1500 2000 2500 3000 3500 4000

nHits

4 −

10

3 −

10

2 −

10

1 −

10

Normalized entries

2.0GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

500 1000 1500 2000 2500 3000 3500 4000

nHits

4 −

10

3 −

10

2 −

10

1 −

10

Normalized entries

4.0GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

Number of hit distribution.

5 Page

Not so great discriminant

Eldwan Brianne | HPgTPC meeting | 03/09/2019

• Distribution as expected
• Muon and punch through pions have a similar distribution
• Tendency to have a larger tail
• Interacting pions have a broad range
• Not very good variable to separate both
• Soft interacting pions should not be too much of trouble

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Energy Sum [GeV]

4 −

10

3 −

10

2 −

10

1 −

10 1

Normalized entries

2.0GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Energy Sum [GeV]

4 −

10

3 −

10

2 −

10

1 −

10 1

Normalized entries

4.0GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

Energy sum distribution.

6 Page

Not so great discriminant

Eldwan Brianne | HPgTPC meeting | 03/09/2019

• Peaks where it is expected
• ~ 0.814 MeV/layer ➠ ~ 0.07 GeV in the ECAL
• Muon and punch through pions have a similar distribution
• Higher tail at higher energies
• Not very good variable to separate both

Hit energy distribution.

7 Page

Maybe sth here

Eldwan Brianne | HPgTPC meeting | 03/09/2019

• Interaction pions have pronounced tail to high hit energies
• Punch-through and soft-interacting pions also have a tail to

high hit energies

• May help to distinguish from muon by shape?
• But alone would not help much
• Tail get more pronounced at higher pion energies
• May come from radiative processes that get more

important at higher energies

0.002 0.004 0.006 0.008 0.01 0.012 0.014

Hit Energy [GeV]

7 −

10

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1

Normalized entries

0.5GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

0.002 0.004 0.006 0.008 0.01 0.012 0.014

Hit Energy [GeV]

7 −

10

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1

Normalized entries

5.0GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

Hit radius distribution.

8 Page

Not so great discriminant

Eldwan Brianne | HPgTPC meeting | 03/09/2019

• Muon and punch-through pion have a similar distribution
• Expected to be at 0 (only a track)
• However, large tail also at higher radii but very low amount

compare to the bulk at 0

• Some interaction pions may also contaminate the sample
• ➠ high EM fraction ➠ small shower

20 40 60 80 100 120 140

Mean Hit Radius [cm]

4 −

10

3 −

10

2 −

10

1 −

10 1

Normalized entries

2.0GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

20 40 60 80 100 120 140

Mean Hit Radius [cm]

4 −

10

3 −

10

2 −

10

1 −

10 1

Normalized entries

4.0GeV Muons Punch-through Pions Interacting Pions Soft interacting Pions

Conclusions and Outlook.

9 Page

Next steps?

• Started to look at mu/pion in the ECAL
• Things don’t look so great for being able to separate mu/pi
• nly via calorimeter variables
• too thin ECAL
• Time of flight not possible here (only for energies < 100 MeV

➠ 1 ns)

• Need a bit more statistics and granularity in energies
• Need to look at thicker ECAL in the back (up to 3

?)

• Will reduce the number of layers
• May affect linearity and energy resolution
• Would we have possibility to have a muon chamber on the
• utside?
• If not, is it acceptable to have 20-30% of events mis-

tagged? What and how would it have an effect on?

λπ

Eldwan Brianne | HPgTPC meeting | 14/05/2019

W e n e e d s

• m

e s

• r

t

• f

m u

• n

t a g g e r

Backup Slides.