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

Looking into mu/pi separation in the ECAL. HPgTPC Meeting Eldwan Brianne DESY Hamburg, 03 rd September 2019

Motivation. A hard task • Started to look into pions and muons in the ECAL • Theoretically e − • ECAL thickness ~ 1 � λ π e + γ EM component • The probability to interact before reaching a Absorber distance d γ P = ∫ π 0 d γ p ( l ) dl = 1 − exp ( − d � λ ) π − π − 0 π − • In the ECAL, � ➠ about 37% will P ( λ ) = 63.2 % μ − look like muons π + n ¯ ν μ • May slightly depend on the particle energy π + (cross-section rises at low energies) • How do they look like? λ π • Can we distinguish them with the ECAL only? Hadronic component � 2 Eldwan Brianne | HPgTPC meeting | 03/09/2019 Page

� Parameters of the study. To set the context • 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 of interaction) • Classified pions in three categories • Punch-through (just going through the ECAL) • Based on interaction hardness criterium ➠ i ∑ E i − E leading > 0.33 × E mother daughters • Hard interaction • Soft interaction � 3 Eldwan Brianne | HPgTPC meeting | 03/09/2019 Page

Interaction probability. Is it as expected? • Interaction Probability • As expected 20 - 30% of the pions don’t interact (or too soft 100 Probability [%] interaction) in the ECAL 90 • ➠ Will be the hard ones to spot! 80 • ➠ Look at the di ff erence between all categories and compare 70 to muons 60 • Number of hits Interacting Pions 50 Punch-through and soft Pions • Energy sum 40 • Hit energy 30 • Hit radius 20 • More ideas to look at? 10 0 1 2 3 4 5 Energy [GeV] � 4 Eldwan Brianne | HPgTPC meeting | 03/09/2019 Page

Number of hit distribution. Normalized entries 2.0GeV Muons 1 − 10 Not so great discriminant Punch-through Pions Interacting Pions Soft interacting Pions • 2 − Distribution as expected 10 • Muon and punch through pions have a similar distribution 3 − • 10 Tendency to have a larger tail • Interacting pions have a broad range 4 − 10 • Not very good variable to separate both • Soft interacting pions should not be too much of trouble 0 500 1000 1500 2000 2500 3000 3500 4000 nHits Normalized entries 4.0GeV Muons 1 − 10 Punch-through Pions Interacting Pions Soft interacting Pions 2 − 10 3 − 10 4 − 10 0 500 1000 1500 2000 2500 3000 3500 4000 nHits � 5 Eldwan Brianne | HPgTPC meeting | 03/09/2019 Page

1 Normalized entries Energy sum distribution. 2.0GeV Muons Punch-through Pions Not so great discriminant − 1 10 Interacting Pions Soft interacting Pions • Peaks where it is expected − 2 10 • ~ 0.814 MeV/layer ➠ ~ 0.07 GeV in the ECAL • 3 − Muon and punch through pions have a similar distribution 10 • Higher tail at higher energies 4 − 10 • Not very good variable to separate both 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Energy Sum [GeV] 1 Normalized entries 4.0GeV Muons Punch-through Pions 1 − 10 Interacting Pions Soft interacting Pions 2 − 10 3 − 10 4 − 10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Energy Sum [GeV] � 6 Eldwan Brianne | HPgTPC meeting | 03/09/2019 Page

1 Hit energy distribution. Normalized entries 0.5GeV Muons 1 − 10 Punch-through Pions Maybe sth here Interacting Pions Soft interacting Pions 2 − 10 • Interaction pions have pronounced tail to high hit energies 3 − 10 • Punch-through and soft-interacting pions also have a tail to 4 − 10 high hit energies • May help to distinguish from muon by shape? − 5 10 • But alone would not help much 6 − 10 • Tail get more pronounced at higher pion energies 7 − 10 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 • May come from radiative processes that get more Hit Energy [GeV] important at higher energies 1 Normalized entries 5.0GeV Muons 1 − 10 Punch-through Pions Interacting Pions 2 − Soft interacting Pions 10 3 − 10 4 − 10 5 − 10 6 − 10 7 − 10 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 Hit Energy [GeV] � 7 Eldwan Brianne | HPgTPC meeting | 03/09/2019 Page

Normalized entries Hit radius distribution. 1 2.0GeV Muons Punch-through Pions Not so great discriminant Interacting Pions 1 − 10 Soft interacting Pions • Muon and punch-through pion have a similar distribution 2 − 10 • Expected to be at 0 (only a track) • However, large tail also at higher radii but very low amount 3 − 10 compare to the bulk at 0 • Some interaction pions may also contaminate the sample 4 − 10 • ➠ high EM fraction ➠ small shower 0 20 40 60 80 100 120 140 Mean Hit Radius [cm] Normalized entries 1 4.0GeV Muons Punch-through Pions Interacting Pions 1 − 10 Soft interacting Pions 2 − 10 3 − 10 4 − 10 0 20 40 60 80 100 120 140 Mean Hit Radius [cm] � 8 Eldwan Brianne | HPgTPC meeting | 03/09/2019 Page

Conclusions and Outlook. Next steps? • Started to look at mu/pion in the ECAL • Things don’t look so great for being able to separate mu/pi • only 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 � ?) λ π W e n e e o • d Will reduce the number of layers f s m o u m o e n • May a ff ect linearity and energy resolution s t a o g r t g e r • Would we have possibility to have a muon chamber on the outside? • If not, is it acceptable to have 20-30% of events mis- tagged? What and how would it have an e ff ect on? � 9 Eldwan Brianne | HPgTPC meeting | 14/05/2019 Page

Backup Slides.