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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 T. Nomura (Kyoto Univ.) T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"
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"
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: KLp0p0p0 (BR 21%), p0p+p- (BR 13%), p0p0 (BR 10-3), … T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"
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"
Challenge “In-beam” environment • High intensity neutral beam(necessary to observe >100 KLpnn 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"
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"
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"
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"
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"
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"
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"
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"
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"
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"
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"
Application To KOPIO experiment at BNL To KLgp0nn experiment at JPARC T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"
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"
KOPIO detector & Beam Catcher T. Nomura @ Workshop on "Mass Origin and Supersymmetry Physics"
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"
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"
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"
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"
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"
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"
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"
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"