1. Detection of Cerenkov light emission in LAr Ettore Segreto University of L’Aquila Ettore Segreto University of L’Aquila Cryodet International Workshop Laboratori Nazionali del Gran Sasso 13-14 March 2006

2. 13 March 2006Cryodet workshop2 OUTLINE Detection of visible light in coincidence with cosmic ray muons in the ICARUS 10m 3 prototype during a dedicate test run at Gran Sasso Laboratory external facility. Geometrical features of the 3D reconstructed muons tracks. Monte Carlo simulation of the detector and of the cosmic muon flux. Comparison of Data with Monte Carlo results. Cerenkov radiation in a next generation large mass LAr TPC (?) Detection of visible light in coincidence with cosmic ray muons in the ICARUS 10m 3 prototype during a dedicate test run at Gran Sasso Laboratory external facility. Geometrical features of the 3D reconstructed muons tracks. Monte Carlo simulation of the detector and of the cosmic muon flux. Comparison of Data with Monte Carlo results. Cerenkov radiation in a next generation large mass LAr TPC (?)

3. 13 March 2006Cryodet workshop3 Nuclear Instruments and Methods in Physics Research A 516 (2004) 348-363

4. 13 March 2006Cryodet workshop4 ICARUS 10m 3 prototype  The module :  ~ 10m 3 of LAr (14 tons).  TPC ( 2.00m (w) x 3.26m (h) x 0.35m( l)  drift length) with two read-out planes: two independent representations of the ionizing event (and possibility of 3D reconstruction).  2” quartz windowed PMT (EMI 9814BQ) -spectral sensitivity: 160 nm-600 nm- not sensitive to 128 nm LAr scintillation radiation. 128

5. 13 March 2006Cryodet workshop5 Data sample The detector was exposed to cosmic ray flux at surface during a complete test (cryogenics, electronic, acquisition system…) held in the external facility (Hall di Montaggio) of LNGS (January-May 2000). The installation inside the 10m 3 LAr volume of the EMI 9814BQ PMT was designed in order to check any possible light emission phenomena, apart from VUV scintillation emission, accompanying ionization processes. In a limited period during the test run a sub-sample of the collected data have been acquired using the PMT signal as trigger for the detector. In principle, if no visible light emission is registered by the PMT in coincidence with the passage of particles in the liquid, no events are recorded. Indeed, we acquired a large sample of events during this dedicated test, indicating that visible light signals are associated to through-going particles. About 1200 events produced by single penetrating muons have been selected for the present analysis The detector was exposed to cosmic ray flux at surface during a complete test (cryogenics, electronic, acquisition system…) held in the external facility (Hall di Montaggio) of LNGS (January-May 2000). The installation inside the 10m 3 LAr volume of the EMI 9814BQ PMT was designed in order to check any possible light emission phenomena, apart from VUV scintillation emission, accompanying ionization processes. In a limited period during the test run a sub-sample of the collected data have been acquired using the PMT signal as trigger for the detector. In principle, if no visible light emission is registered by the PMT in coincidence with the passage of particles in the liquid, no events are recorded. Indeed, we acquired a large sample of events during this dedicated test, indicating that visible light signals are associated to through-going particles. About 1200 events produced by single penetrating muons have been selected for the present analysis

6. 13 March 2006Cryodet workshop6 Events selection and reconstruction (I) Collection view Induction view Typical event produced by a crossing muon in the 10m 3 detector triggered with the internal PMT Each view of each selected event is linearly fitted to obtain the geometric parameters of the two 2D projections of the event. PMT

7. 13 March 2006Cryodet workshop7 The analytic combination of the two 2D projection of the events allows to obtain a complete 3D reconstruction of the muon track:  Entry point in the detector.  Zenith (  and Azimuth (  angles. The analytic combination of the two 2D projection of the events allows to obtain a complete 3D reconstruction of the muon track:  Entry point in the detector.  Zenith (  and Azimuth (  angles. Hall di Montaggio Events selection and reconstruction (II)

8. 13 March 2006Cryodet workshop8 Geometrical features of selected tracks (I) The peak position in  distribution means that muons propagating towards the PMT window are strongly favored, i.e. strong directionality (characteristic of Cerenkov radiation) The left-right asymmetry (white histogram) is mainly due to the geographycal location of the detector. The presence of the Gran Sasso massif strongly suppresses the cosmic muon flux with larger values of zenith angles (  >45 0 ) in the region  ~ [200 0,340 0 ]. A cut was applied: only vertical muons are considered (  <45 0 ) to remove asymmetry (yellow histogram). The residual asymmetry is due to the PMT position, not perfectly symmetric with resepect to the wire chamber The peak position in  distribution means that muons propagating towards the PMT window are strongly favored, i.e. strong directionality (characteristic of Cerenkov radiation) The left-right asymmetry (white histogram) is mainly due to the geographycal location of the detector. The presence of the Gran Sasso massif strongly suppresses the cosmic muon flux with larger values of zenith angles (  >45 0 ) in the region  ~ [200 0,340 0 ]. A cut was applied: only vertical muons are considered (  <45 0 ) to remove asymmetry (yellow histogram). The residual asymmetry is due to the PMT position, not perfectly symmetric with resepect to the wire chamber

9. 13 March 2006Cryodet workshop9 Geometrical features of selected tracks (II) Most of the events are broadly distributed between 5 cm and 20 cm. The average value is ≈ 10 cm. Track Impact parameter w.r.t. the PMT optical window

10. 13 March 2006Cryodet workshop10 Cerenkov radiation in LAr by cosmic muons. A cosmic muon (z= ±1) in ultra-relativistic regime (   1) propagating in LAr (n  1.22) radiates visible Cerenkov photons with an angle w.r.t. its direction: The spectrum is continuous: Average number of Cerenkov photons detectable by the installed PMT (160nm-600nm): A cosmic muon (z= ±1) in ultra-relativistic regime (   1) propagating in LAr (n  1.22) radiates visible Cerenkov photons with an angle w.r.t. its direction: The spectrum is continuous: Average number of Cerenkov photons detectable by the installed PMT (160nm-600nm):

11. 13 March 2006Cryodet workshop11 Monte Carlo simulation Simulation code based on the GEANT 3 package. Precise description of the geometrical features and of the materials constituting the detector. Exact spectrum (energy, azimuth and zenith angles) for cosmic muons. Cerenkov photons production and propagation. Optical properties of the materials: Refelectivity of the internal structures (aluminium/stainless steel). Rayleigh scattering in LAr (and no absorption). PMT response (Quartz window transmittance and photo- cathode quantum efficiency). Simulation code based on the GEANT 3 package. Precise description of the geometrical features and of the materials constituting the detector. Exact spectrum (energy, azimuth and zenith angles) for cosmic muons. Cerenkov photons production and propagation. Optical properties of the materials: Refelectivity of the internal structures (aluminium/stainless steel). Rayleigh scattering in LAr (and no absorption). PMT response (Quartz window transmittance and photo- cathode quantum efficiency).

12. 13 March 2006Cryodet workshop12 Real data vs. MC simulation Yellow Data Red MC Yellow Data Red MC The detected light is consistent with Cerenkov radiation emission by cosmic muons.

13. 13 March 2006Cryodet workshop13 From Carlo Rubbia talk

14. 13 March 2006Cryodet workshop14 Single detector: charge imaging, scintillation, Cerenkov light LAr Cathode (- HV) E-field Extraction grid Charge readout plane UV & Cerenkov light readout PMTs E≈ 1 kV/cm E ≈ 3 kV/cm Electronic racks Field shaping electrodes GAr

15. 13 March 2006Cryodet workshop15 Cerenkov photons: additional discrimination  + with 500 MeV of kinetic energy The track in the LAr TPC Spectrum: 200nm< <600nm Full GEANT-4 simulation Idea: use combination of charge readout and Cerenkov light to determine mass of particle (hep-ph/0402110 A. Rubbia) Drift

16. 13 March 2006Cryodet workshop16 e    Signal e  e Background Example:  /  discrimination in beta beams The combination of the information from the tracking and calorimetric measurements with the Cerenkov light provides improved particle identification. For example one can separate in this way pions from muons, a very important tool in the context of beta-beams The combination of the information from the tracking and calorimetric measurements with the Cerenkov light provides improved particle identification. For example one can separate in this way pions from muons, a very important tool in the context of beta-beams 20% coverage and 20% Q.E. Energy(MeV)     2001016840016412620 6009728429401089183485 100019308058672042936244

17. 13 March 2006Cryodet workshop17 Conclusions Ionizing tracks from cosmic ray muons crossing the ICARUS 10m 3 active volume have been collected in coincidence with visible light signals from a PMT immersed in liquid argon. By means of a detailed Monte Carlo simulation we have shown that the geometrical characteristics of the events are compatible with the hypotesys of Cerenkov light emission as the source of the PMT signals. Ionizing tracks from cosmic ray muons crossing the ICARUS 10m 3 active volume have been collected in coincidence with visible light signals from a PMT immersed in liquid argon. By means of a detailed Monte Carlo simulation we have shown that the geometrical characteristics of the events are compatible with the hypotesys of Cerenkov light emission as the source of the PMT signals.

18. 13 March 2006Cryodet workshop18 Backup Slides

19. 13 March 2006Cryodet workshop19 Combinig Cerenkov and charge read-out (I)  Non destructive multiple read-out of a LAr TPC allows to reconstruct particle tracks with bubble-chamber quality.  Fine granularity allows precise calorimetric measurements.  Tracking and calorimetry provide momenta, particle identification, clean e/    separation …

20. 13 March 2006Cryodet workshop20 Why detect Cerenkov radiation in a LAr TPC of next generation? Passive perlite insulation  ≈70 m h =20 m Max drift length Electronic crates A “general-purpose” detector for superbeams, beta-beams and neutrino factories with broad non-accelerator physics program (SN, p-decay, atm, …)

21. 13 March 2006Cryodet workshop21 Neutrino detection: LAr TPC vs water Cerenkov K2K ICARUS 50 liters Multi prong event detection not possible with water Cerenkov

22. 13 March 2006Cryodet workshop22 Pion contamination for 90% muon acceptance Kinetic energy (MeV) Q.Efficiency = 1 Q.Efficiency = 4% Q.Efficiency = 2% 20002.07 e-141.93 e-08 3001.45 e-131.98 e-074.69 e-05 4001.08 e-062.18 e-042.75 e-03 5009.76 e-047.6 e-032.5 e-02 6002.21 e-025.38 e-029.61 e-02 7008.85 e-021.49 e-012.11 e-01 8002.17 e-012.78 e-013.33 e-01 9003.73 e-014.23 e-014.67 e-01 10004.34 e-014.78 e-015.16 e-01 20008.71 e-018.73 e-018.75 e-01 30009.53 e-01 9.52 e-01