BaBar DIRC in SoLID. P. Nadel-Turonski, Z. Zhao, C. Hyde... SoLID bi-weekly meeting, January 15, 2013

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1 BaBar DIRC in SoLID P. Nadel-Turonski, Z. Zhao, C. Hyde... SoLID bi-weekly meeting, January 15,

2 Emerging opportunity 1. BaBar DIRC suddenly becomes available in December 2012 SuperB (next generation BaBar) canceled in Italy JLab can get the DIRC from SLAC if needed for a good project 2. SoLID with K ID up to 90 offers unique physics opportunities He target outside, unpolarized (and longitudinal) targets inside solenoid High-pT SIDIS ( Alexei's slides) Hard exclusive reactions with kaons and leptons (J/ψ, TCS) Spectroscopy (Ξ, Ω, etc) 3. JLab would become main US center for Cherenkov technology Funding SoLID would become a step toward a future EIC Other prospective EIC technologies could also be incorporated into SoLID e.g., high-resolution (10-20 ps) TOF at forward angles 2

3 DIRC principle Charged particle traversing radiator with refractive index n with β = v/c > 1/n emits Cherenkov photons on cone with half opening angle cos θc = 1/βn(λ). For n> 2 some photons are always totally internally reflected for β 1 tracks. Magnitude of Cherenkov angle conserved during internal reflections Photons exit radiator into expansion region, detected on photon detector array. DIRC is intrinsically a 3-D device, measuring: x, y, and time of Cherenkov photons, defining θc, φc, tpropagation of each photon. 3

4 The synthetic fused silica (quartz) bars BABAR-DIRC bars were polished to 5 Å rms, non-squareness < 0.25 mrad Bar box: 12 bar boxes in BABAR 12 long (4.9m) bars per box 150μm air gap between bars dry nitrogen flow Long bar: 4 short (1.225m) bars Mirror on forward end Wedge on readout end 4

5 The DIRC in BaBar DIRC thickness: 8 cm radial incl. supports 19% radiation length at normal incidence DIRC radiators cover: 94% azimuth, 83% c.m. polar angle DIRC photon detection array: 10,752 PMTs ETL 9125 Low energy photons from accelerator hit Standoff Box. Background rates in 300 ns window: MHz per PMT (GHz per box) 5

6 Event reconstruction Calculate unbiased likelihood for signals to originate from e/ / /K/p track or from background: Likelihood: Pdf(θc) x Pdf(Δt) x Pdf(Nγ) Pdf = Probability distribution function Example: comparison of real event to simulated response of BABAR DIRC to e/π/k/p. Time resolution important for background suppression 300 nsec trigger window (~ background hits/event) 8 nsec t window (1-2 background hits/sector/event) 6

7 Focusing DIRC (FDIRC) at SLAC Photodetector: 12 arrays of 6*8 MaPMTs (HPK H8500) 18,432 pixels. Readout Electronics: TDC/ADC information for every photon. Bottom line: Conservative, robust design; 10x better timing resolution than BABAR DIRC; 25x smaller expansion volume than BABAR DIRC; Cherenkov angle determined from 2D spatial coordinates; Time primarily used to correct chromatic dispersion. Could be made cheaper (mineral oil instead of quartz) and momentum coverage could be extended 7

8 Cherenkov angle (θc) resolution BaBar (3σ) EIC? Extending π/k separation from 4 to 6 GeV/c requires σθ ~ 1 mrad (vs 2.4 in BaBar a 58% reduction). 8

9 PID as a function of θc resolution Extending 3σ π/k separation from 4 to 6 GeV/c requires σθ ~ 1 mrad (vs 2.4 in BaBar a 58% reduction). 9

10 Improving the θc resolution 10

11 Example 1 DIRC and SoLID as is Illustrates the maximum coverage of the DIRC bars In reality it would be preferable to increase the DIRC radius leaving more room for polarized targets e/π Cherenkov (blue) Thinner and longer calorimeter in barrel would be preferable reoptimization of GEMs Z. Zhao 11

12 Example 2 DIRC partially retracted Illustrates the DIRC in maximally retracted position Optimization of e/π Cherenkov and calorimeter would give more coverage Inner radius adjusted to 1 m (80% azimuthal coverage) Plenty of space for He target Cryotargets and longitudinally polarized target can be placed just inside the solenoid PID up to 90 in lab frame! Z. Zhao 12

13 Summary Adding the BaBar DIRC to SoLID open new physics opportunities High-pT SIDIS, exclusive reactions, spectroscopy Re-using a very expensive detector makes SoLID more appealing JLab could become a center for imaging Cherenkov technology in the US SoLID could become the basis for the development of a future EIC detector Need to think in detail about integration of the DIRC with SoLID Could invite expert from SLAC for collaboration meeting in February 13

14 Backup 14

15 BaBar 15

16 GlueX detector 16

17 BCAL for GlueX 17