The Construction and Commissioning of the Belle II iTOP Counter - PowerPoint PPT Presentation

The Construction and Commissioning of the Belle II iTOP Counter Boqun Wang on Behalf of Belle II iTOP Group Department of Physics, University of Cincinnati July 31, 2017 DPF 2017, Fermilab, US _ _ Belle II 1

Belle II Experiment • Belle is a B-factory operated on Y(4S) resonance energy, collected ~1.0 ab -1 of data • Successful physics achievements: direct CP violation in B decays, D meson mixing, new (X, Y, Z) hadrons, measurement of CKM matrix, etc. • Belle II is an upgrade of Belle • Target integrated luminosity: ~50 ab -1 and peak luminosity: 8 x 10 35 cm -2 s -1 (by using nano-beam technology) • Physics run: ~ 2018 Nano-beam 2

Principles of iTOP Detector cos θ c = 1/n β π and K have different θ c Different hit positions and arrival times of photons side-view top-view 3

Procurement of Synthetic Fused Silica (Quartz) • Two bars, one mirror and one prism per module. • Totally 16 modules and 1 spare module. • Acceptance test: • For 32+ bars: chip inspection, bulk transmittance, internal surface reflectance. • For 16+ mirrors: chip inspection, reflectivity, position of optical axis, focal point and focal length, spherical aberration, astigmatism • For 16+ prisms: chip inspection, transmission, angle of tilted surface. • Surface flatness, surface roughness, parallelism, perpendicularity and chamfer specs were qualified by vender. Interferograms of one of the bar surfaces from metrology report 4

QA: Quartz Bar Bulk Transmission Internal Reflectivity [%] Internal Reflectivity Requirement: Bulk Transmittance: > 98.5 %/m Internal Reflectivity: > 99.9 % 5 Bulk Transmittance [%/m]

QA: Mirror & Prism Specification 6525 89 Radius: 6500 ± 100 mm 88 6520 Reflectivity: > 85 % 87 6515 Reflectivity [%] 86 Radius [mm] 6510 85 84 6505 83 6500 82 6495 81 S S S S S S S S S S S S S S S S S S SN-002 SN-003 SN-004 SN-006 SN-007 SN-008 SN-010 SN-011 SN-012 SN-015 SN-005 SN-013 SN-014 SN-016 SN-017 SN-018 SN-019 SN-020 N N N N N N N N N N N N N N N N N N - - - - - - - - - - - - - - - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 1 1 1 1 1 1 2 2 3 4 6 7 8 0 1 2 5 5 3 4 6 7 8 9 0 Angle of tilted face: 18.07 ± 0.04 deg ( ± 144 arcsec) 6

Alignment & Gluing Procedure: 1. adjust surfaces positions using laser displacement sensor and micrometers 2. adjust surfaces angles using autocollimator and micrometers 3. repeat steps 1, 2 4. insert shims, tape joint 5. apply epoxy (EPOTEK 301-2) to joint 6. clean excess glue after curing and final inspection 7

After Gluing Long time exposure with laser input from prism end Laser scattering on the surface and inside the bar 8

Quartz Bar Box (QBB) Assembly Use vacuum based lifting jig to move glued optics to QBB assembly table 9

Front-End Electronics PMT module MCP-PMT: 4 x 4 anodes 27.6 x 27.6 mm2 For each iTOP module: 23.0 x 23.0 mm2 active 4 boardstacks 8 PMT modules 32 MCP-PMTs 512 readout channels QE requirement: > 24% at peak λ > 28% average Boardstack 10

Installation All module installed by May 2016 11

Readout System Transition from Full Waveform to Region of Interest & Feature Extraction IRSX: Waveform sampling ASIC • Operated at 2.7GSa/s sampling rate in TOP • 12bit resolution • ~600MHz analog bandwidth • 32768 samples storage depth 12

Global Cosmic Ray Test • Global cosmic ray data taking started since July 3, 2017 • Outer detectors including TOP joined the data taking • Rough number of photon hits per events agrees with MC • More detailed analyses are ongoing slot 5 slot5 slot5 1200 Entries Entries 32505 32505 24.94 24.94 Mean Mean 14.81 14.81 Std Dev Std Dev 1000 Very rough result 800 600 400 200 0 0 10 20 30 40 50 60 70 80 90 100 13

More Ongoing Work Channel by Channel Time Alignment Understanding laser data Laser fibers installed for each module 14

Summary • iTOP is a new type of ring-image Cherenkov detector for Belle II. It provides particle identification ability in the barrel region. • The construction of all modules took ~18 months. They’re all installed to Belle II and cabled, being tested. • The global cosmic ray data taking with other detectors started on July 3, 2017. The analysis of cosmic data is ongoing. • Excellent Kaon identification efficiency of 93% at a rather low 4% pion misidentification probability (88%, 9% respectively at Belle) over the wide momentum range is expected (see backup slides). • First collision data of phase 2 will be taken early 2018. • Belle II will take physics data with all sub-detectors installed in late 2018. 15

Backup

Expected Performance TOP L(K)-L( )>0 TOP+ARICH+dE/dx L(K)-L( )>0 π π 1 1 Efficiency Efficiency 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 kaons kaons 0.4 0.4 pions pions 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 2 Momentum [GeV/c ] 2 Momentum [GeV/c ] • Simulation performed in the Belle II software framework • Excellent K identification efficiency (small pi misidentification probability) over wide momentum range • Belle II: 93% (4%) • Belle: 88% (9%) 17 0.3

Readout System MCP-PMT Life Extension Improve low PMT gain: use template fit to waveform data