1. Plastic Scintillator Option for DB a simulation study by Maxim Gonchar, Yury Gornushkin and Dmitry Naumov JINR, Dubna, Russia Collaboration Meeting January 12-15 2007

2. Plastic Scintillator Option for muon veto @ DB Why Plastic Scintillator? A word of worry about it? Our analysis and suggestions to Collaboration Meeting January 12-15 2007

3. Coil Veto Shield Spectrometers Target Tracker Why Plastic Scintillator? Muon veto system based on plastic scintillators is a robust, cost-effective and efficient approach. There is an extensive experience using of this technology (MINOS, OPERA) (Yuri’s talk later on this).

4. Plastic Scintillator Option for muon veto @ DB A word of worry a gamma can kick out an electron from the medium due to the Compton scattering. If the flux of gammas is high enough they can produce fake triggers what is a bad thing. Collaboration Meeting January 12-15 2007 Are there reliable solutions? look for coincidences in different layers: double, tripple, quatrupole, etc put the scintillator in water to shield against gammas

5. Requirements for the muon veto Simulation Framework Trigger rate of muons vs Fake rate of gammas  CDR numbers  An attempt to understand Aberdeen tunnel data Study of various options for the plastic scintillator  3 layers by 1 cm thickness  4 layers by 1 cm thickness  3 layers by 1.5 cm thickness Conclusions and further work Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

6. Requirements for the muon veto 99.5% efficiency to detect muons reduce fake trigger rate due to natural radioactivity Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

7. Simulation Framework While DayaBay software is under development and revision (geometry via VGM, etc) build own light weight package as follows: Generators: Simple muon Generator following CDR for the modified Gaisser formula, ignore shape of mountains around Gamma spectrum as measured in Aberdeen tunnel Transport: Geant4 to transport particles Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

8. Simulation Framework While DayaBay software is under development and revision (geometry via VGM, etc) build own light weight package as follows: Data Containers: ROOT objects with hits, event header, detector responses Geometry: Geometry Factor to test about 10 (implemented) geometries Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

9. Simulation Framework Visualization: Use VGM to export Geant4 geometry to ROOT TGeo objects and visualize using ROOT (basically much more convinient than Geant4 shipped viewers) Analysis: ROOT macros and C++ classes to analyse data Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

10. Trigger rate of muons vs Fake rate of gammas  Main questions are:  how much gammas are more abundant than muons?  how to reduce gamma's fake rate to a modest level? Collaboration Meeting January 12-15 2007  CDR numbers  An attempt to understand Aberdeen tunnel data Plastic Scintillator Option for muon veto @ DB

11. Trigger rate of muons vs Fake rate of gammas  We simulated gammas and muons passing through plastic scintillators as were measured in the Aberdeen tunnel Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

12. Coin/min = 916.9 +/- 17.5 5 cm Coin/min = 517.3 +/- 13.2 397.3 +/- 11.5 Scin (surface area = 1000cm 2 ) Pb (0.3cm) Pb (5cm) (47927 / 30217) (48546 / 29543) (38436 / 21581) A B C 5 cm I 64.8 +/- 4.7 (13602 / 9663) D 67.35 +/- 1.3 (38436 / 21581) (35892/21937) adopted from Ming-chung Chu 朱明中

13.  Trigger rate of muons vs Fake rate of gammas Collaboration Meeting January 12-15 2007 used measured in Aberdeen spectrum Plastic Scintillator Option for muon veto @ DB

14.  Trigger rate of muons vs Fake rate of gammas  mode A Collaboration Meeting January 12-15 2007 detector geometry from event viewer Plastic Scintillator Option for muon veto @ DB

15.  Trigger rate of muons vs Fake rate of gammas  mode A Collaboration Meeting January 12-15 2007 energy released by gammas and muons in one plate due to inclined muons Plastic Scintillator Option for muon veto @ DB

16.  Trigger rate of muons vs Fake rate of gammas  mode A Collaboration Meeting January 12-15 2007 Probability to release energy by gammas and muons in one plate Plastic Scintillator Option for muon veto @ DB

17.  Trigger rate of muons vs Fake rate of gammas  mode A Collaboration Meeting January 12-15 2007 Coincidence by gammas and muons Plastic Scintillator Option for muon veto @ DB

18.  Trigger rate of muons vs Fake rate of gammas Collaboration Meeting January 12-15 2007 number of counts = gamma flux x probability (E>532 keV) + noise muons are marginal this is known from MC for every configuration comparing different configurations in Aberdeen experiment I estimate: noise = 3600 counts per minute gamma flux = 38000 counts per minute = 0.64 Hz/cm2 combining this with Daniel Ngai et al calculations it follows that muons are about 100 000 more suppressed than gammas Plastic Scintillator Option for muon veto @ DB

19.  Trigger rate of muons vs Fake rate of gammas Collaboration Meeting January 12-15 2007 there is a reasonable agreement for bottom counter (2) and coincidences, while upper counter counts systematically more than expected...may be different threshold or so Plastic Scintillator Option for muon veto @ DB

20.  Study of various options for the plastic scintillator:  Keep in mind that the muon veto must be able to suppress gamma background by a factor 100000 or better 1000000  We built 3 options:  detector 1 – 3 layers by 1 cm thick of scintillator  detector 2 – 4 layers by 1 cm thick of scintillator  detector 3 – 3 layers by 1.5 cm thick of scintillator Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

21.  Study of various options for the plastic scintillator:  Keep in mind that the muon veto must be able to suppress gamma background by a factor 100000 or better 1000000  We built 3 options:  detector 1 – 3 layers by 1 cm thick of scintillator  detector 2 – 4 layers by 1 cm thick of scintillator  detector 3 – 3 layers by 1.5 cm thick of scintillator Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

22. 2 of 3 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB

23. 3 of 3 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB

24.  Study of various options for the plastic scintillator:  Keep in mind that the muon veto must be able to suppress gamma background by a factor 100000 or better 1000000  We built 3 options:  detector 1 – 3 layers by 1 cm thick of scintillator  detector 2 – 4 layers by 1 cm thick of scintillator  detector 3 – 3 layers by 1.5 cm thick of scintillator Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

25. 2 of 4 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB

26. 3 of 4 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB

27. 4 of 4 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB

28.  Study of various options for the plastic scintillator:  Keep in mind that the muon veto must be able to suppress gamma background by a factor 100000 or better 1000000  We built 3 options:  detector 1 – 3 layers by 1 cm thick of scintillator  detector 2 – 4 layers by 1 cm thick of scintillator  detector 3 – 3 layers by 1.5 cm thick of scintillator Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

29. 2 of 3 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB

30. 3 of 3 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB

31.  Water shielding (studied 3 options with 3 layers):  50 cm of water  100 cm of water  150 cm of water Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB put in water

32. 2 of 3 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB muon no water 50 cm of water 100 cm of water 150 cm of water

33.  Conclusions:  Use of coincidence allows to suppress gamma background while keeping high efficiency of muon detection Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB from the data gamma flux = 0.64 Hz/cm2 = 6.4 e3 Hz/m2

34.  Conclusions:  Water shielding greatly impoves the result and may provide an economic solution Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB from the data gamma flux = 0.64 Hz/cm2 = 6.4 e3 Hz/m2

35.  Further work:  Implement this work into official Daya Bay code –> quite straightforward  work more on optimization of thickness taking into account optics properties of plastic scintillator, p.e. and all that Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

36.  Trigger rate of muons vs Fake rate of gammas  Backup slides Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

37. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode B Collaboration Meeting January 12-15 2007 detector geometry from event viewer 5 cm

38. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode B Collaboration Meeting January 12-15 2007 energy released by gammas and muons in one plate due to inclined muons

39. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode B Collaboration Meeting January 12-15 2007 Probability to release energy by gammas and muons in one plate

40. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode B Collaboration Meeting January 12-15 2007 Coincidence by gammas and muons

41. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode C Collaboration Meeting January 12-15 2007 detector geometry from event viewer 5 cm

42. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode C Collaboration Meeting January 12-15 2007 energy released by gammas and muons in one plate due to inclined muons

43. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode C Collaboration Meeting January 12-15 2007 Probability to release energy by gammas and muons in one plate

44. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode C Collaboration Meeting January 12-15 2007 Coincidence by gammas and muons

45. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode D Collaboration Meeting January 12-15 2007 detector geometry from event viewer 5 cm

46. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode D Collaboration Meeting January 12-15 2007 energy released by gammas and muons in one plate due to inclined muons

47. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode D Collaboration Meeting January 12-15 2007 Probability to release energy by gammas and muons in one plate

48. Plastic Scintillator Option for DB  Trigger rate of muons vs Fake rate of gammas  mode D Collaboration Meeting January 12-15 2007 Coincidence by gammas and muons

49.  Study of various options for the plastic scintillator:  Keep in mind that the muon veto must be able to suppress gamma background by a factor 100000 or better 1000000  We built 3 options:  detector 1 – 3 layers by 1 cm thick of scintillator  detector 2 – 4 layers by 1 cm thick of scintillator  detector 3 – 3 layers by 1.5 cm thick of scintillator  detector 4 – 2 layers: 1cm and 3 cm thick of scintillator Collaboration Meeting January 12-15 2007 Plastic Scintillator Option for muon veto @ DB

54. 2 of 3 coincidence as a function of energy deposit Plastic Scintillator Option for muon veto @ DB