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High density aerogel for ASHIPH SND – test results

10-th INTERNATIONAL CONFERENCE ON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS. High density aerogel for ASHIPH SND – test results. Beloborodov K. Authors. Budker Institunte of Nuclear physics, Novosibirsk: SND team: Beloborodov K., Golubev V., Serednyakov S., Vesenev V. KEDR team:

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High density aerogel for ASHIPH SND – test results

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  1. 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS High density aerogel for ASHIPH SND – test results Beloborodov K.

  2. Authors • Budker Institunte of Nuclear physics, Novosibirsk: • SND team: • Beloborodov K., Golubev V., Serednyakov S., Vesenev V. • KEDR team: • Barnyakov A., Barnyakov M., Bobrovnikov V., Buzykaev A., • Kononov S., Kravchenko E., Onuchin A. • Boreskov Institute of Catalysis, Novosibirsk: • Danilyuk A.

  3. Outline • VEPP-2000, SND detector • Physical program for SND at VEPP-2000 • Aerogel properties • SND aerogel counter design. Construction status. • Test with cosmic muons • Misidentification • π/K – separation power. • Conclutions

  4. VEPP-2000 complex Main parameters: •perimeter:24.4 m • collision time: 82 nsec • beam current: 0.2 A • bunch length: 3.3 cm • energy spread:0.7 MeV Luminosity: L ≃1•1032cm-2s-1at 2E= 2.0 GeV ≃1•1031cm-2s-1at 2E= 1.0 GeV ► Design feature: round beams (βx≃βz: 6.3cm) ► Project goal: 3 fb-1 till 2011

  5. Physical program for SND at VEPP-2000 • Precise measurement of the quantity R = (e+e- → hadrons) / (e+e- → +-) • Study of hadronic channels: e+e- → 2h, 3h, 4h …, h = , K,  • Study of ‘excited’ vector mesons: ’, ’’, ’, ’’, ’,.. • CVC tests: comparison of e+e- → hadrons (I=1) cross section with -decay spectra • Study of nucleon-antinucleon pair production, nucleon electromagnetic form factors, … • Hadron production in ‘radiative return’ (ISR) processes: e+e- → γγ* , γ* → hadrons • Two photon physics: e+e- → e+e- + X • Test of the QED high order processes 2 → 4,5

  6. Spherical Neutral Detector (SND) 1 – VEPP-2000 beam pipe, 2 – Tracking system, 3 – Aerogel Cherenkov counter, 4 – NaI(Tl) counters, 5 – Vacuum phototriodes, 6 – Fe absorber, 7-9 – Muon system, 10 – VEPP-2000 s.c. focusing solenoids

  7. SND drift chamber: π/K-separation Design parameters: Main parameters: • sensitive length along beam axis: 230-280 mm • internal diameters of sensitive volume: 42 mm • outer diameter of sensitive volume: 200 mm • type drift cell: JET • number of measurements within drift cell: 9 • number of drift cells: 24 • acceptance (4 layer / 9 layers): 94 % / 75 % of 4π • entrance material budget: ≤ 1 % X0 • total material budget: 4 % X0 • number of shield wires (Ø 120 μm): 984 • number of sensitive/anode wires (Ø 15-20 μm): 312 • number of cathode strips: 288 • spatial resolution: - drift time in R-φ plane: σX ≈ 150 μm - charge division along wire: σZ ≈ 1.5 mm - cathode strips: σZ ≈ 0.5 mm • angular resolution: σφ≈ 0.3 o σθ≈ 0.5 o • energy loss resolution: σ(dE/dx)/<dE/dx>≈ 25 % • π/K separation: at p ≤ 300 MeV/c

  8. μ0=10 ph.e. Dependence of the detection efficiency on particle momentum: μ0=5 ph.e. K π μ0 – average number of photoelectrons for a relativistic particle pthr – Cherenkov threshold momentum for a particle nopt 1,14 1,12 Aerogel refraction index: selection • Requierements on effective π/K - separation momentum region: • should overlap with DC: pmin = 300 MeV/c • K-mesons should not produce Cherenkov light: • pmax = 870 MeV/c • (for K-meson in e+e-  K+K-) n = 1.13 ± 0.01

  9. Aerogel: properties • Stages of dense aerogel production: • Synthesis of “light”aerogel with densityρ=0.24 г/см³ (n=1.05) • Sintering“light”aerogel to density ρ=0.50÷0.76 г/см³ (n=1.10÷1.15) Nucl.Instrum.Meth.A494:491-494,2002 Aerogel parameters: • Refraction index: n=1.13±0.01 • Density: ρ=0.65 g/cm3 • Light scattering length: Lsc=19 mm at =400 nm • Light absorbtion length: Labs=100 cm at =400 nm

  10. Aerogel counters: design 3 2 1 1 - PMT, 2 – aerogel with n=1.13, 3 - WLS Aerogel counter Design • Scheme: Aerogel + Wavelength • shifter (WLS) + PMT • (Nucl.Instrum.Meth.A315:517-520,1992) • WLS position: displaced by ~5° from • counter center • Aerogel cover: teflonwith a refractivity • of R ~98% • Aerogel thickness: ~31 mm Aerogel System Design • Cylindrical shape: R=105÷141 mm • Walls material: Al, 1 mm thickness • Consists of 3 segments with 3 separate • counters in each • Solid angle: ~60% of4π • Thickness: 0.09 Xo

  11. SND aerogel counter: construction

  12. SND aerogel counter: 27.02.2008

  13. Test with cosmic muons Time resolution Pb pμ>500 MeV/c Signal amplitude pμ>1000 MeV/c • Measurements with cosmic rays: • Signal amplitude • Inhomogeneity of light collection • Time dependence of amplitude • Time resolution

  14. Amplitude. Inhomogeneity of light collection b Map of mean amplitudes in units of photoelectrons. Boxes indicate the locations of trigger counters. The errors are statitical.

  15. Time dependence of amplitude 1 year • Barnyakov. Influence of water absorbed in aerogel on light • (poster) absorption length

  16. ACC counter time resolution • Contributions into the time resolution : • cherencov light collection time < 0.5 ns • time spread of trigger counters ~ 0.7 ns • time spread of the photon propagation in the WLS < 0.1 ns • decay time of BBQ + number of photo electrons ~ τBBQ/Nph.e.≈15/7.5≈2 ns FWHM/2.36 ≈ 2.0 ns Time resolution vs Nph.e: ΔT=τ/Nph.e. Time resolution of the counter mostly depends on decay time of BBQ τBBQ=15 ns τ = 15.7 ± 0.6 ns

  17. KEDR aerogel counter: tests with π/p-beams protons pions Nucl.Instrum.Meth.A494:424-429,2002 ─ Cherenkov light of the initial particle (π, p) ─ Cherenkov light of δ-electrons Cherenkov light of δ-electron with pe ─Cherenkov light from the teflon, scintillations, … δ-electron spectra

  18. Misidentification calculation kaons pions kaons Iπ=9.48 ph.e. kaons pions IK=0.18 ph.e. kaons • Equality of misidentifications: • Mis-n: ~1% (2.6σ) • ε(K)=90%: • Mis-n of π: ~8·10-2 % (3.3σ) • ε(π)=90%: • Mis-n of K: ~7·10-3 % (3.9σ) 1 2 2 3 pions 3 1

  19. Separation power: DC + ACC εK = 90%, Imax = 8 ph.e. επ= 90%, Imax = 8 ph.e. K meson separation π meson separation επ= 90%, Imax = 10 ph.e. εK = 90%, Imax = 10 ph.e. π meson separation K meson separation

  20. Conclusions • First time high density aerogel is used for PID • Aerogel counters designed and constructed for SND • Tests with cosmics muons was perform: • Average amplitude is around 10 ph.e. • Inhomogeneity of light collection is not more than 20% over the counter • Maximum amplitude decrease with time τ≈725 days and aerogel should be repaired time to time • Time resolution is σt~15/Nph.e • Calculation of underthreshold effects was done • Estimated π/K-separation power for SND detector

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