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Development of an Aerogel-based Photon Detector

Development of an Aerogel-based Photon Detector. T. Nomura (Kyoto Univ.). Motivation, Challenge, and Solution. A part of veto detector in rare K L experiment. Located in intense neutral beam. Aerogel-based photon detector. Motivation. Necessary in K L g p 0 nn measurement

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Development of an Aerogel-based Photon Detector

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  1. Development of an Aerogel-based Photon Detector T. Nomura (Kyoto Univ.) T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  2. Motivation,Challenge,and Solution A part of veto detector in rare KL experiment Located in intense neutral beam Aerogel-based photon detector T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  3. Motivation Necessary in KLgp0nn measurement • Importance of KLgp0nn • CP violating process • Branching ratio proportional to |Im(Vtd)|2, BR~10-11 • Very small theoretical uncertainty (~1%) • Play an important role to explore BSM (like SUSY) • Difficulty ofKLgp0nn experiment • All neutrals in initial and final states • Event signature: 2g (from p0)+ nothing (2n) • We have to prove “nothing” in order to suppress backgrounds: KLp0p0p0 (BR 21%), p0p+p- (BR 13%), p0p0 (BR 10-3), … T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  4. Main Photon Detector g n signal KLgp0nnSignature： g “2g (from p0)+ nothing” n Surrounding Veto veto g g g g Background g Escaping gthroughbeam-hole g g g Motivation To prove “nothing”, we needsHermetic veto system Need to catch photons escaping through the beam-hole What we want to develop !! T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  5. Challenge “In-beam” environment • High intensity neutral beam(necessary to observe >100 KLpnn events in 2-3 years) • A vast amount of neutrons (a few~10GHz) • Produce protons, pions, (g and e+/e-) in the detector • Most KLs survive after decay region (~100MHz) • Decay into p, g ,e+/e- in the detector  These secondary particles fire the counter and disturb its primary function !! T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  6. Solution • Utilize Cherenkov radiationAerogel (low refractive index ~1.05) radiator • Avoid detection of slow particles from neutron interactions Slow p, p and other hadrons cannot emit lights. • Use direction informationSegment the detector into many modules and require coincidence along the beam direction • Catch forward photons only Reduce fake signal due to g from secondary p0 (neutron interaction and KL decay in the detector) T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  7. e+ γ e- Plan view Example of g event (MC) g Require coincidence along forward direction red: e+/e-, blue: photon Design of In-Beam Photon Detector • Module • Pb (g converter) & Aerogel (Cherenkov radiator) • Light collection with Flat mirror & Winston cone • Sparse “sandwich” detector • modules’ array T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  8. PT1 Proof of Principle (I) We’ve made three generations of prototypes • Prototype 1 (2001-2) • Simple structure • 11cm x 11cm tiles • Flat mirror • Read by 5-inch PMT • Exercise to use aerogel detector • light yield T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  9. PT2 Proof of Principle (II) • Prototype 2 (2002-3) • Sophisticated optics • 11cm x 11cm tiles • 2-axis parabolic mirror • Read by 5-inch PMT • light yield • response to proton(as substitute for neutron) T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  10. M1*(M2+M3+M4) thres. = 2pe What we learned from Prototype 2 • Response to Proton(analogous to neutron’s) • Single module efficiency • Find N2 gas scintillation(problematic in 1p.e. region) • Two layers’ coincidence • Good agreement with MC T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  11. PT3 Proof of Principle (III) • Prototype 3 (2004-5) • Base design • 30cm x 30cm area(3x3 of 10cm sq. aerogel tiles) • Flat mirror • Winston cone • Read by 5-inch PMT • light yield • position / angular dependence T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  12. 30cm 30cm 3 x-sectionals, jointed here 30cm 48cm Elements of Prototype 3 • Elements • 3x3 10cm sq tiles, stacked 5 layers • Winston cone • made by thin Al • Al+SiO2 evaporated on inner surface 45 Tiles made by Matsushita Made by Yokohama-Kiko T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  13. What we learned from Prototype 3 (i) • Position dependence • Global structure, reproduced well by MC • Edge effect between tiles • surface deterioration by trimming process (water jet) By Winston cone entrance (x=6cm) By tiles’ edge effect (x=5cm) T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  14. What we learned from Prototype 3 (ii) • Angular dependence • Global structure, reproduced well by MC • Winston cone deformed • stressed by joint or support By cone’s acceptance (q=7 deg) Reflection anglemeasured by laser By cone deformation (q=5 deg) T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  15. BA APC Practice in KEK E391a experiment E391a-III had run with this Prototype 3 called “APC” (Aerogel Photon Catcher) • Used as in-beam g tagger BA (Beam Anti) E391a in-beam detector PWO & Quartz sandwich T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  16. Application To KOPIO experiment at BNL To KLgp0nn experiment at JPARC T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  17. Barrel Veto Main (endcap)Photon Detector Signal 2g KOPIO experiment Terminated (2005 August) Planned KLgp0nn experiment at BNL (Construction 2006-, Run 2010-) • High intensity proton beam • 100 TP/spill • Soft KL beam • 0.5-1.0 GeV/c • Horizontally wide beam • 4mrad x 90mrad • Measure g direction as well as energy • Sensitivity: 40 SM events (S/N~2), or 200 SM events (S/N~0.3) T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  18. KOPIO detector & Beam Catcher T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  19. Top view Beam envelope 12m downstream of main detector KOPIO In-beam Photon Detector In-beam Aerogel Detector • Module size: 30cm x 30cm • Module array • Number of modules: 420 • 12-21 in horizontal with beam divergence • 25 layers along beam(8.3 X0 in total) • Z gap between layers: 35cm T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  20. Photon Efficiency 99% @ 300MeV Expected Performance by MC (1) In KOPIO case • Photon efficiency • Soft KL in KOPIO • Relatively low energy g • Relatively small shower • Low threshold Coincidence condition: 4 p.e in A, 2 p.e. in B T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  21. Expected Performance by MC (2) In KOPIO case Hit probability for Neutrons Hit probability for KLs Dominated by decays in the detector 0.3% @ 800MeV T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  22. Application to Experiment at J-Parc KLgp0nn experiment plan at J-Parc • 30GeV proton, 100 TP/spill • Small production angle, relatively hard KL beam • Pencil beam • ( a few ~ 10 ) mstr, ~10cmf at the detector • Step 1 with (modified) KEK E391a detector • ~10 SM events, Discovery phase • Step 2 with new, optimized detector • Precision measurement, ~100 SM events T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  23. Beam 30cmx30cm 25 modules(8.3X0), 35cm pitch  ~9m long In-beam Detector for J-Parc experiment • In contrast with KOPIO case • Pencil beam • A series of modules along beam direction • Relatively high energy g (neutrons) • Detection threshold can be (has to be) higher • 3 consecutive hits, 4~24 p.e. T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  24. Neutron Hit probability Level of 0.1% @ 4.0GeV/c Photon efficiency 90% efficiency @1GeV 99% efficiency @2GeV At high energy limit, inefficiency ~ O(10-3) Example of photon event (MC) Example of neutron event (MC) red: e+/e-, blue: photon dot-chain: neutral hadron Expected Performance In J-Parc case T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  25. Inefficiency for Photon Hit probability for Neutrons O(10-3) @ 4GeV/c ~10% ineff @ 1GeV ~1% ineff @ 2GeV Expected Performance In J-Parc case With various threshold T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

  26. Summary • We’ve developed Aerogel-based Photon Detector to use in intense neutral beam • One of the key detectors in KLgp0nn experiment to explore physics beyond the SM • New concept • Pb (converter) + Aerogel (Cherenkov radiator) • Sparse “sandwich” detector • Proof-of-Principle done with 3 generations of prototypes • Originally, it was designed for KOPIO experiment.Now, we are considering to use this detector at J-PARC T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"

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