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Monica Pepe INFN Perugia

The RICH Detector of the NA62 Experiment at CERN. Monica Pepe INFN Perugia on behalf of the NA62 RICH Working Group: CERN, INFN Firenze, INFN Perugia. Second International Conference on Technology and Instrumentation in Particle Physics June 9 – 14, 2011, Chicago, IL.

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Monica Pepe INFN Perugia

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  1. The RICH Detector of the NA62 Experiment at CERN Monica Pepe INFN Perugia on behalf of the NA62 RICH Working Group: CERN, INFN Firenze, INFN Perugia Second International Conference on Technology and Instrumentation in ParticlePhysics June 9 – 14, 2011, Chicago, IL

  2. OUTLINE CERN Accelerators (notto scale) • The NA62 experiment at CERN • The RICH detector design • The RICH prototype: final test beam results • Summary NA62 The NA62 Collaboration: Bern ITP, Birmingham, Bristol, CERN, Dubna, Fairfax, Ferrara, Florence, Frascati, Glasgow, IHEP Protvino, INR Moscow, Liverpool, Louvain, Mainz, Merced, Napoli, Perugia, Pisa, Roma I, Roma II, San Luis Potosi, SLAC, Sofia, TRIUMF, Turin Monica Pepe - INFN Perugia

  3. The NA62 Experiment @ CERN Anewexperimentaiming at a 10% precisionmeasurementofBR(K+ p+nn) • “Golden” channel, theoreticallyveryclean, sensitive tophysicsbeyond SM • BRTH(K+→+) = (8.5 ± 0.7) × 10-11 SM@NLO (PRD78, arXiv:0805.4119) • BREXP(K+ → +) = (1.73 ) × 10-10E787/E949@BNL (PRL101, arXiv:0808.2459) • Main background events: BR(K+ → +) = 63.4% , BR(K+ → +0) = 21% +1.15 -1.05 • NA62 GOALS: • O(100) K+→p+nnevents in 2 years (starting in 2012) • ≤ 10% background contamination • background suppressionfactor ~ 10-13 • ~ 10% signalacceptance • Kinematicallyconstraint • background • REQUIREMENTS: • Km2rejectionfactorofat least 10-12 • Kinematics:~10-5 → StrawTracker + GTK • Veto forμ:~10-5→ Muon Veto • Particle ID:μsuppressionfactor ≤ 10-2 • Precise -K coincidence timing • Time resolution:≤ 100 ps RICH Monica Pepe - INFN Perugia

  4. The NA62 Detector Total Length 270m SPS primaryprotonbeam: 400 GeV ~5×1012 ppp → expectedsignalevents~50/year (1 “year”: 100 days/year, 60% overallefficiency) • decay in flight technique • unseparatedbeam/K/p (~6% K+) • Kaonmomentum: 75 GeV/c (Δp/p ~ 1%) • Kaonflux = 4.8 × 1012decay/year Monica Pepe - INFN Perugia

  5. The NA62 RICH Detector • REQUIREMENTS: • Separate in 15 < p < 35 GeV/cwith a muonsuppressionfactorbetterthan 10-2 • Measure pion crossing time with a resolution < 100 ps • Provide a L0 trigger for charged tracks Radiator:Neon gas at atmosphericpressure(non-flammable): appropriate refractiveindex at atmosphericpressure (n-1) = 62.8 10-6 at =300 nm (small dispersion) low atomicweighttominimizeradiationlength good light transparency in visible and near-UV, low chromatic dispersion Cmax = 11.2 mrad; pthreshold = m / (n2-1) = 12 GeV/c for MirrorMosaic (17 m focallength) 17 m Beam Vessel diameter 4→3.4 m Beam Pipe Volume ~ 200 m3 2 × ~1000 PM Monica Pepe - INFN Perugia

  6. Mirror layout • Mirrorsfrom MARCON company • Sphericalmirrors, nominalradiusof curvature 34 m (±20 cm maximum), 17 m focallength • Glass substrate2.5 cm thick, aluminumcoatwiththindielectric film (MgF2) deposit • Hexagonalshape (35 cm side): 18 hexagons + 2 half hexagons (beam pipe) 3m diameter • Averagereflectivitybetterthan 90% in 195-650 nmwavelenghtrange, D0 < 4 mm • Carbonfiberhoneycombstructureformirrorsupport, piezoactuatorsforalignment • Mirrorspointingtowardleft and right of the beam pipe (2 PM regions) • Initialalignementwith laser, checkwith data Mirror layout and support MC Simulation (Geant4): photondistribution on the mirrors (15-35 GeV/c momentum) Monica Pepe - INFN Perugia

  7. The light detection Hamamatsu R7400 U03 Photomultiplier • Fast single anodephotomultiplier • Metal package tube, bialkalicathode, 8 dynodes • UV glasswindow, 16 mm ϕ (photocathode 8 mm active ϕ) • Sensitivityrange 185–650 nm, 420 nmpeaksensitivity • Gain: minimum 7x105 @800 V (~1.5x106 @900 V) • Transittime: 5.4 ns, transittime spread (FWHM): 0.28 ns • OperatingVoltage: 900 V (1000 V maximum) Light Collection • Winston ConescoveredwithaluminizedMylarfoils • 22 mm high • 7.5 to 18 mm wide • 1 mm thickquartzwindow HV CAEN System • 4 PMT suppliedby a single HV channel • SY1527 (16 slots), SY2527 (6 slot) mainframes • A1733N (12 ch.) and A1535S (24 ch.) board R7400U-06 Spectralsensitivity R7400U-03 Monica Pepe - INFN Perugia

  8. Front End and Readout Front End: Custom madecurrentamplifier NINO ASIC as fast Time-over-Thresholddiscriminator (from ALICE): LVDS output, 50 ps intrinsicresolution Signalleading and trailingedgerecordedfortimeslewingcorrections • Readout: based on TDC Boards • Board(TDCB) equippedwith128 ch. of TDC (HPTDC, 100 ps LSB) hasbeendevelopedby INFN Pisa • FPGA basedTEL62motherboard(evolutionof TELL1 boardsfromLHCb) housing4 TDCB (512 TDC ch.) • Trigger primitives are built in parallelwith the readout on the sameTEL62 board (1 MHz input toL1, implemented in software) • TDC CAEN V1190 (based on HPTDC, 97.7 ps LSB, 128ch) wasusedfor test purposes INFN PISA Monica Pepe - INFN Perugia

  9. The NA62 RICH Prototype • Vessel ~17 m long, ~60 cm diameter • filledwith Ne gas at ~1 atmosphere • One singlesphericalmirror(MARCON) • f = 17 m, d = 50 cm, 2.5 cm thickglass Test-beam 2007: RICH-100 prototype • 96 PMT Hamamatsu R7400 U03/U06 • Results in agreement with MC expectation: • Number of PM hit per event NHits ≈ 17 • Time resolution Dt≈ 70 ps • Cherenkov angle resolution Dqc≈ 50 mrad • NIM A 593 (2008) 314 Test-beam 2009: RICH-400 prototype • 414 PMT Hamamatsu R7400 U03 • Final results will be shown here RICH-100 Monica Pepe - INFN Perugia

  10. The RICH-400 Prototype • New PM flange: 414 PM (20% offinal detector) • Test Beam in may-june 2009, aiming at: • Validate p-mseparation @ 15<p<35 GeV/c • Test cooling system • Test newmirror • Test newreadout (TEL62) NIM A 621 (2010) Monica Pepe - INFN Perugia

  11. RICH-400: Test Program • Beam: mainly+, 15% p, few % K+, variable % ofe+ • Momentumrange: 10 to 75 GeV/c • 1.5% Δp/p, negligibleangular spread (divergence < 30 mrad) • p-mseparation @ 15-35 GeVmeasuredusingonlypions: • eachmeasurementdonewithtwopoints in momentum: nextmomentumpointis a π with the sameβof the μ of the actualpoint(μ-π equivalent) • p15.2 17.7 20.0 23.4 26.5 28.7 31.0 35.0 GeV/c • ″m″20.0 23.4 26.5 31.0 35.0 38.0 41.0 46.3 GeV/c • Test prototype performance under differentconditions: • Moving the mirror, differentrates, different TEL62 firmwareversions, polluting the gas (air and CO2), etc. • Repeatmeasurementswith the newmirror(final device, made by Marcon, aluminized and coated at CERN): • Specialruns: • checktrigger algorithms and accidentals at higherintensities • measure efficiency for ring fittingmethods Monica Pepe - INFN Perugia

  12. Test installation: the mirror Monica Pepe - INFN Perugia

  13. Test installation: vessel closing Monica Pepe - INFN Perugia

  14. Numberof PM hits Typical data eventswithfittedrings Numberof hit PMsfor a single ring (cut at 4 due to the software trigger algorithm) Pions at 15 GeV/c: NHit PM≈ 8 Pions at 35 GeV/c: NHit PM≈ 17 Positrons at β=1: NHit PM≈ 20 Results in agreement with MC expectations Averagenumberof hit PMsfor a single ring as a functionofmomentum in the range 15-35 GeV/c Monica Pepe - INFN Perugia

  15. Timing and Cherenkov angle • Cherenkov angle resolution • Δθc ≈ 70 μradfor β → 1 • Timeresolution • ΔtEvent< 100 ps CherenkovResolution [μrad]   Timeresolutionas a functionof the π momentum: averagerootmeansquareof the selected hit timewithrespectto the average hit time Cherenkov angle resolutionas a functionof the π momentum: the standard deviation σ isestimatedby a Gaussianfitto the radiusdistribution • The resultsfulfill the requirementfor the NA62 RICH detector and are compatiblewiththoseof the 2007 beam test • The sameresults are obtainedusingboth the standard readout system and the newreadoutprototype • Data are in agreement with Montecarlo simulation Monica Pepe - INFN Perugia

  16. MC/Data Comparison NA62 Detector Simulation: GEANT4 based RICH beam test results in good agreement with Monte Carlo simulationexpectations in 15-35 GeV/c Monica Pepe - INFN Perugia

  17. /μseparation (I) e p “m” e 15 GeV/c 35 GeV/c “m” p 2 Fittedring radius R(m) The “μ” is a  withthe sameβas a µ at 15 (35) GeV/c • RICH REQUIREMENT: μsuppression ≤10-2 • The probabilitytomisidentify a μ as a π isintegratedbetween15 and 35 GeV/c (assuming the expectedspectrumof µ from Kµ2) • Repeat the measurementchangingmirrororientation and analysiscuts Monica Pepe - INFN Perugia

  18. /μseparation (II) 15 GeV 35 GeV p p “m” “m” Red line: signaldefinition (+3 frompeak) Blueline: half way between and μpeaks Calculate:μcontamination and  loss (under differentconditions) in momentumbins (Use ring radiusdistribution and the reconstructedsquared mass of the particle) Monica Pepe - INFN Perugia

  19. /μseparation: results Measurementsrepeatedwithdifferentcuts and ring reconstructionmethods: upper and lowerlimit are the 3σ constraint on the position of the fitted ring center. Measurementsrepeatedfor 4 differentalignmentpositionsof the mirror, in orderto take into account possibledisplacementsof the ring center (in mm). misidentificationprobabilitylowerthan 10-2 Overall integral  0.7% residual contamination of muons in the pion sample Monica Pepe - INFN Perugia

  20. SUMMARY • The NA62 RICH willbeusedfor: • background suppression (p-m separation) • precise measurement of track time • first level trigger • The prototype test beam results fulfill the design requirements • time and Cherenkov angle resolution • number of hit PM’s per ring • p-m separation and m suppression factor The construction of the NA62 detector has already started: the first data taking will take place in 2012 Monica Pepe - INFN Perugia

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