1. Prototypes photon veto detectors for NA62 experiment CERN M. Raggi - INFN/Frascati for the NA62 Photon Veto Working Group LNF, RM1, NA, PI, SOFIA First BTF user workshop Laboratori Nazionali di Frascati 7th May 2014

2. NA62 search for K + →    at the SPS 2 BR (       ) | SM ~ 10 -10 Minimal theoretical uncertainty Precise measurement of unitarity triangle for K system BR         ) ~ 21% Need rejection factor 10 -12 Photon veto inefficiency: Maximum 10 -4 for E  > 200 MeV NA62 goal: Detect 100 K + →    decays with S/B ~ 10 7/05/14Mauro Raggi BTF User Workshop

3. Photon veto detector system 7/05/14Mauro Raggi BTF User Workshop 3 5 GeV 2 GeV 1 GeV0.1 GeV ≈ 10 -5  detection inefficiency ≈ 10 -4 inefficiency E  > 200 MeV ++ RICH Liquid Krypton calorimeter Large Angle Photon veto (LAV) (LAV) Vacuum decay tube < 10 -6 mbar (IRC) (LAV) (SAC) 4 different types of detectors: LAV, LKr calorimeter, Intermediate ring calorimeter ( IRC ) and small angle calorimeter ( SAC )

4. 4 Lead/scintillating tile WLS fiber readout Lead/scintillating fiber Prototype built for CKM/FermilabPrototype built and tested at LNF Technologies tested at BTF Leadglass OPAL barrel EM

5. LNF fiber prototype 5 KLOE-type lead/scintillating fiber calorimeter 1-mm diameter scintillating fibers 0.5-mm thick lead foils Full-scale prototype of smallest rings 1/3 of final radial thickness Inner/outer radius: 60 cm - 72.5 cm Inner/outer length: 309.5 cm - 348.8 cm Readout granularity: 18 cells, 4.2  4.2 cm 2 16.8 cm (4 cells)8.2 cm (2 cells) ~13X 0 ~10X 0 3 cells All fibers (same as KLOE)Fibers + 1-mm Pb wires 7/05/14Mauro Raggi BTF User Workshop

6. Tile prototype from CKM at Fermilab 6 5 mm scintillating tile + 1 mm lead, 80 layers total Prototype consists of 2 of 16 sectors in azimuth - 4 PMTs per sector Measured performance at JLAB: 1 - e < 3x10 -6 for 1.2 GeV electrons 7/05/14Mauro Raggi BTF User Workshop

7. Ex OPAL EM calorimeter lead glass 7 3800 modules from the central part of the OPAL barrel EM calorimeter become available for use in NA62 37 cm 10 x 10 cm 2 front face OPAL PbGl at the BTF Schott SF57 lead glass: Density5.6 g/cm 3 Refractive index 1.85 Radiation length1.5 cm Moliere radius 2.6 cm 7/05/14Mauro Raggi BTF User Workshop

8. The Frascati Beam-Test Facility 8 attenuation target dipole 1 slits dipole 2 to DAFNE Electron test beam parameters: Energy range100 to 750 MeV Selection resolution  E/E ~ 1% Mean multiplicity1 to 10 9 Bunch length10 ns Repetition rate50 Hz Setup used during tests in 2007: Single electron mode (using electron tagger) Different energies: 203 MeV, 350 MeV, 483 MeV linac e  line  line 7/05/14Mauro Raggi BTF User Workshop

9. Beam tagging detectors 9 F1F2 H1H2 90 cm P1P2 beam Finger counters (F1, F2) Select 1e events 60 x 85 x 10 mm 3 scintillator paddles Hole counters (H1, H2) Define good beam trajectory 330 x 100 x 10 mm 3 (e.g. H2) paddle with 14-mm hole in center BTF fiber beam profile meters (P1, P2) Assist with beam positioning 1-mm scintillating fiber array (16 channels of 3  4 fibers) 7/05/14Mauro Raggi BTF User Workshop

10. Measurement principle 10 E A+B [MeV] 1 e event selection with fingers F1F2 F1F2H1H2 Good-beam definition with holes F1 ADC H1 ADC Reconstructed energy distribution, E beam = 483 MeV 1e1e 2e2e 3e3e 4e4e 5e5e Events Fiber prototype 7/05/14Mauro Raggi BTF User Workshop

11. Summer 2007 data-taking 11 Energy [MeV] P (1 e ) [%]  (tag|1 e ) [%] Tagged events Fiber (KLOE) 203 31.32.5 70k 350 33.09.2 210k 483 33.314.4 370k Tile (CKM) 203 29.53.7 65k 350 31.88.8 220k 483 29.017.6 370k Lead glass (OPAL) 203 30.23.9 25k 483 26.017.1 90k 7/05/14Mauro Raggi BTF User Workshop

12. Efficiency for E beam = 203 MeV 12 Total events:8657175 1 e fully tagged:68829 E A+B < 50 MeV 5 events 1  = (7.3 +4.1 -3.3 )  10 -5 E A+B < 50 MeV E A+B [MeV] Events Threshold E A+B [MeV ] - Measured value n FC 68.27% CL (1 - e) 7/05/14Mauro Raggi BTF User Workshop

13. Efficiency for E beam = 350 MeV 13 Total events:6835715 1 e fully tagged:207385 E A+B < 50 MeV 3 events 1 -  = (1.4 +1.1 -0.9 )  10 -5 E A+B < 50 MeV E A+B [MeV] Events (1 - e) Threshold E A+B [MeV ] - Measured value n FC 68.27% CL 7/05/14Mauro Raggi BTF User Workshop

14. Efficiency for E beam = 483 MeV 14 Total events:7779171 1 e fully tagged:371633 E A+B < 50 MeV 1 event 1 -  = (2.7 +4.7 -1.7 )  10 -6 E A+B < 50 MeV E A+B [MeV] Events (1 - e) Threshold E A+B [MeV ] - Measured value n FC 68.27% CL 7/05/14Mauro Raggi BTF User Workshop

15. Technology efficiency comparison 15 Fiber/KLOE Tile/CKM  PbGl/OPAL Efficiencies for e  detection similar for all 3 technologies E beam [MeV] (1 -  ) E meas < 50 MeV Assumes no false tags 68.27% FC CLs 7/05/14Mauro Raggi BTF User Workshop

16. Fiber prototype linearity 16 E beam [MeV] Side A Side B  Side A+B  E / E beam [%] E meas [MeV] Not easy to test quantitatively: BTF energy selection  E = 1% (included in error bars) Run-by-run energy scale fluctuations ~5% (not included in error bars) Perform run-by-run energy-scale calibration for resolution and efficiency measurements Linearity basically satisfactory at low energy Need readout with extended dynamic range in real experiment 7/05/14Mauro Raggi BTF User Workshop

17. Fiber prototype energy resolution 17 Perform Gaussian fits to 1e - peak (  1.5s) after run-by-run calibration Side A Side B  Side A+B Example fits Side A+B 203 MeV 350 MeV 483 MeV Resolution  E / E [%] E [MeV] Using information from both sides: EE E 5.1%  E [GeV]  4.4% = 7/05/14Mauro Raggi BTF User Workshop

18. Small angle calorimeter test 2013 7/05/14Mauro Raggi BTF User Workshop 18 Electron energy: 570MeV to 606 MeV 24 spills per second 10ns spill Everything readout by a 1 GHz FADC (including the trigger scintillators) External triggering from the BTF No trigger bias and possibility for offline study SAC FADC RO PC Ch 0,1,2,3 : SAC 70 lead scintillator sandwiches 1.5mm lead 1.5mm scintillator Kuraray Y-11(250) 1mm fibers 20.5x20.5 cm 2 front face 4 Hamamatsu R6427 PMT SAC main characteristics Readout scheme

19. Collected spectrum of the BTF beam 7/05/14Mauro Raggi BTF User Workshop 19 Charge collected on the 4 PMTs Fit performed with 6 gaussian distribution with no constraints

20. Linearity and energy resolution 7/05/14Mauro Raggi BTF User Workshop 20 Linearity of the response seem to be quite good single impact point! No scanning of the front surface Linearity resultsEnergy resolution

21. SAC inefficiency for electrons 7/05/14Mauro Raggi BTF User Workshop 21 The events below 1e peak doesn't look exactly as inefficient events They are above the no-activity in SAC – 5pC That kind of activity seem to present also under the 1-2-3-x electrons peaks No inefficient events below 5pc leads to an inefficiency estimate: 5pC cut: inefficiency<6x10 -5 1e  tagged

22. Summary and outlook 22 NA62 requires photon veto detectors with 1-  200 MeV. In 2007 we tested at the Frascati BTF 3 different prototypes for the NA62 large angle photon veto measuring an inefficiency for electrons down to few 10 -6 at 500 MeV for all the 3 technologies. In June 2013 we tested the NA62 Small Angle Calorimeter prototype achieving an preliminary inefficiency measurement down to 6x10 -5 Frascati BTF played a crucial role in the development of the NA62 photon veto allowing very precise calibration of the detectors and inefficiency measurements down to few 10 -6. All the efficiency measurements were limited by statistics. For this reason a higher number of bunches per second was desirable. Tagged photons lines would have been a very desirable. 7/05/14Mauro Raggi BTF User Workshop