1. Simulation of the DHCAL Prototype Lei Xia Argonne National Laboratory American Linear Collider Workshop: Ithaca, NY, July 13 - 16, 2003 Fe absorber Glass sheets PCB board Nylon spacers

2. Simulation Based on GEANT4 Default energy cut-off values Geometry of ‘extended’ prototype with 1.5 x 1.5 x 3.0 m 3 Leakage studies with 1.0 x 1.0 x 1.0 m 3 fiducial volume corresponding to 40 layers RPCs Active media Spacers every 5 cm Scintillator Set-up G10 Steel Glass Gas 20 mm 1.1 mm 3.0 mm 1.2 mm 1.1 mm 1.6 mm Steel Scintillator 20 mm 1.6 mm 6.4 mm

3. Readout Investigating both analog (ΣE) and digital (N hits ) readout No additional energy smearing applied Readout pad size 1 cm 2 Hit defined as positive energy in active medium (E dep > 0) Hit detection efficiency is 100% Error bars in following plots Variance of distributions Analog Digital

4. Linearity for e - DigitalAnalog RPCs Scintillator Analog readout linear up to 90 GeV Digital readout non-linear (as expected for e - ) Signal in RPCs smaller Results in both media very similar Lines only to guide the eye

5. Linearity for π - DigitalAnalog RPCs Scintillator Analog readout linear up to 90 GeV Digital readout almost linear Signal in RPCs smaller Results in both media very similar

6. Shower containment for π - RPCs Scintillator Definition Fraction of events with less than 5% of E dep … analog Hits … digital outside 1 m 3 Containment decreases with increasing energy Results similar in RPCs and scintillator Analog somewhat better than digital (different definition)

7. ElectronsPions RPCs Electrons Radius constant with E (A) Radius keeps increasing (D) Effect of dense core Pions ~ constant with energy (A+D) Effect of wide shower Difference A and D Different definition? Shower radius Definition Digital Analog Scintillator

8. Digital readout - Number of hits Electrons Pions More hits in scintillator (factor ~7) Effect on energy resolution ??? Response for e - and π - within ~10% Almost compensating

9. Digital readout - Shower containment Somewhat better containment in RPCs at lower energy Due to narrower showers in RPCs

10. Digital readout - Shower radius Electrons Pions Showers significantly narrower in RPCs Confirms previous studies by Videau, Sokolov Distinct advantage for EFAs

11. Shower radius – Understanding the difference New Scintillator configuration Using RPC structure Gas replaced by Scintillator (BC408) Everything else the same G10 Steel Glass Scintillator 20 mm 1.1 mm 3.0 mm 1.2 mm 1.1 mm 1.6 mm Shower radius: Results unchanged! Particles traversing active medium EM showers γ … conversion probability larger in SCI 4x10 -4 versus 1x10 -5 e + … 10% more in SCI e - … 90% more in SCI HAD showers γ, e ± … same as above π ± … same in RPC and SCI n … ~10% less in SCI (not detected) p … ~30% more in SCI e-e- p Excess at low energies E kin of particles traversing active medium

12. Shower radius – Examples EM showers RPC SCI ALL e+e+ e-e-

13. Shower radius – Examples HAD showers RPC SCI ALL e+e+ e-e-

14. SCI HAD showers Shower radius – Examples RPC p π-π- π+π+

15. Radius decreases with increasing E 0 Resolution worsens with increasing E 0 For E 0 ~ 1800 keV: both comparable to RPC Shower radius – E 0 dependence 50 GeV EM showers Vary E 0 in Scintillator Radius E Resolution

16. Shower radius – E 0 dependence 50 GeV HAD showers Vary E 0 in Scintillator Radius E Resolution Resolution worsens with increasing E 0 Radius always larger than in RPCs! Why is that?

17. Shower radius – Individual components EM showers in Scintillator Radius of e + and e - decreases with increasing E 0 Major effect from e - HAD showers in Scintillator Radius of e ±, π ± decrease with E 0 Radius of p remains large!!! Large radius due to protons Radius

18. Conclusions EM and HAD showers appear narrower in a DHCAL with RPCs compared to a DHCAL with Scintillator This effect is due to larger and wider cloud of deposits from electrons (and protons in HAD showers) in Scintillator compared to RPCs The results were obtained with a threshold for hits E 0 at 0 With increasing E 0 in Scintillator Radius and E resolution of EM showers decreases Radius of HAD shower remains large (due to protons) Lower energy cut-offs (GEANT) increase the number of hits insignificantly in RPCs by 10 - 20% in Scintillator by 2 – 10 %