J-PARC - PowerPoint PPT Presentation

J-PARC 高運動量ビームラインにおける チャームバリオン分光実験のデザイン 白鳥昂太郎 for the E50 collaboration Research Center for Nuclear Physics (RCNP) 計測システム研究会 @ RCNP 2015 7/24

2 Contents • Physics motivation • Experiment at J-PARC - High-momentum beam line - Design of Spectrometer system • Key devices - RICH - High-rate detectors - DAQ • Summary

3 What is a building block of hadrons ? q ͞ q Constituent Quark q q q ͞ q q Exotic hadron q q q q-q q-q correlation (diquark) Q

4 Charmed baryon spectrum: “Excitation Mode” Heavy Quark: Weak color-magnetic interaction ⇒ ” q-q ” isolated and developed: “q-q + Q” Spin-Spin ρ Interaction q-q Isotope shift q q ρ mode Q q q-q λ λ mode Q G.S.

Experiment High-momentum beam line Design of Spectrometer system Simulation

6 J-PARC & Hadron Facility

7 High-momentum beam line Construction by 2018 ? Primary proton beam ⇒ 2 ndary Beam High-p

8 Experimental conditions in Hadron hall Slow beam extraction Fixed target experiment c.f. GR, SKS, LHCb, CLAS, LEPS1&2 (2.0 sec/ 6.0 sec cycle) Magnet Detectors Beam intensity Target Beam Time (2.0 sec) Scattered particles DC 2 ndary beam: 10 7 − 10 8 Hz, 100 × 100 mm 2 , ∆ p/p = 2 − 3% • Beam measurement is essential. - Forward scattering by In-Flight reaction •

9 High-momentum beam line for 2 ndary beam • High-intensity beam: > 1.0 × 10 7 Hz π (< 20 GeV/c) - Unseparated beam • High-resolution beam: ∆ p/p ~ 0.1%(rms) - Momentum dispersive optics method Exp. Target (FF) Collimator Dispersive Focal Point (IF) 15kW Loss Target ∆ p/p~0.1% (SM)

10 Experiment K + & π − : 2 − 16 GeV/c Missing mass measurement Slow π s − : 0.5 − 1.7 GeV/c Decay measurement π ± & p: 0.2 − 4.0 GeV/c s π + p Λ c *+ OR Σ c 0 D 0 π − + p → Y c *+ + D * − reaction @ 20 GeV/c 1) Missing mass spectroscopy - D * − → D 0 π s − → K + π − π s − : D * − → D 0 π s − (67.7%), D 0 → K + π − (3.88%) 2) Decay measurement - Decay particles ( π ± & proton) from Y c *

11 Production cross section High energy 2-body reaction based on the Regge theory Normalized to strangeness production ⇒ Charm production: ~10 -4 No old data @ 10-20 GeV/c ＊ Assumed production cross section: σ ~ 1 nb - π − + p → Λ c + + D * − reaction @ 13 GeV/c: σ < 7 nb (BNL data) • High-rate beam & High-rate detector system - Beam intensity: 6 × 10 7 /2.0 sec spill (~1 MHz/mm)

12 Old experiments Target Holes for beam Missing mass spectrum BNL experiment in 1983 • π − p → Λ c + D* − @ 13 GeV/c - N π = 3 × 10 12 - ∆ M = 20 MeV ＊ ∆ p/p < 1 % Λ c Σ c + + ＊ Acceptance = a few 10%

13 Design procedure Beam momentum & target change 1) Reaction condition: Kinematics Momentum & angular distribution - Correlations of scattered particles Magnetic field - Production & decay angle dependences Strength & Shape - 2) Magnet: Dipole Exist magnet or new one Fast or Slow bending, - Gap size: Acceptance - Gap size, Magnet shape Magnetic field: Bending power - 3) Detector Detector choice Size, Layer, - ○ Size: Acceptance Segment, ○ Time & position resolution ○ Configuration: Layer, segment Thickness, ○ Counting rate per segment: Beam through Shape PID type - 4) Performance study Momentum resolution: Material thickness - Invariant & missing mass distribution - Target energy loss struggling & multiple scattering - PID performance - Feedback to whole procuress 5) Realistic magnet and detector design ⇒ Minor changes Full simulation - Detector R&D, Readout modules, cabling -

14 Spectrometer design Κ + Κ + π s − π − π − • Primitive design ⇒ 1) Kinematics & 2) Magnet • Magnet: Toy magnet

15 Spectrometer design π − Κ + π − Κ + π s − π s − • 2-arm design ⇒ 2) Magnet • Magnet: Super-BENKEI

16 Spectrometer design π − Κ + π − Κ + π s − π s − • 2-arm design ⇒ 2) Magnet • Magnet: Super-BENKEI ⇒ すでに破棄！

17 Spectrometer design π − Κ + π s − • 2-arm design ⇒ 2) Magnet • Magnet: FM magnet (E16 will use at High-p BL.)

18 Spectrometer design π − π − Κ + π s − • Single arm design ⇒ 3) Detector & 4) Resolution • Magnet: FM magnet

19 Spectrometer design FM cyclotron magnet Dipole magnet Magnet pole Target Beam Magnet pole Scattered particles • High-rate beam & High-rate detector system - Beam intensity: 6 × 10 7 /2.0 sec spill (~1 MHz/mm) • Dipole-magnet spectrometer - High-resolution: ∆ p/p < 1%

20 Spectrometer design Λ c * decay measurement Dipole magnet Magnet pole Target Beam Beam Target Magnet pole D* measurement • High-rate beam & High-rate detector system - Beam intensity: 6 × 10 7 /2.0 sec spill (~1 MHz/mm) • Dipole-magnet spectrometer - High-resolution: ∆ p/p < 1%

21 Spectrometer design Λ c * decay measurement Dipole magnet Magnet pole Target Beam Beam Target Magnet pole D* measurement • High-rate beam & High-rate detector system 100% acceptance - Beam intensity: 6 × 10 7 /2.0 sec spill (~1 MHz/mm) • Dipole-magnet spectrometer - High-resolution: ∆ p/p < 1%

22 Spectrometer system Dipole Magnet Decay π − π s − Κ + π − π − Target Decay π +

23 Spectrometer system Dipole Magnet Decay π − π s − Κ + π − π − Target Beam measurement Fiber trackers • Decay π + Beam Cherenkov •

24 Spectrometer system Dipole Magnet Decay π − π s − Κ + π − π − Target Beam measurement D* measurement Fiber trackers • Fiber trackers • Decay π + Beam Cherenkov • Internal DCs • Downstream DC, TOF • Ring Image Cherenkov •

25 Spectrometer system Λ c * decay measurement Dipole Magnet Internal DCs • Internal TOF Decay π − • Pole face TOF detector π s − • Κ + π − π − Target Beam measurement D* measurement Fiber trackers • Fiber trackers • Decay π + Beam Cherenkov • Internal DCs • Downstream DC, TOF • Ring Image Cherenkov •

26 Charmed baryon spectrometer Large Acceptance Multi-Particle Spectrometer Acceptance: ~50% for D * , ~80% for decay π /p • Mass resolution: M Λ c* = 10 MeV(rms) @ 2.7 GeV/c 2 •

27 Charmed baryon spectrometer Large Acceptance Multi-Particle Spectrometer Acceptance: ~50% for D * , ~80% for decay π /p • Mass resolution: M Λ c* = 10 MeV(rms) @ 2.7 GeV/c 2 •

28 Background spectra @ 20 GeV/c Q-value _ D 0 mass Q-value (M(K + π − π − )-M(K + π − )-M π ) [GeV] Invariant mass M(K + π − ) [GeV/c 2 ] K + , π − , π s − events Background = Signal × 10 6 ＊ Both D 0 mass and Q-value region selected by narrow gate

29 Background reduction: D* tagging Invariant mass M(K + π − ) [GeV/c 2 ] Invariant mass M(K + π − ) [GeV/c 2 ] Signal event region 1.852 GeV/c 2 < M D < 1.878 GeV/c 2 4.3 MeV < Q < 7.5 MeV Q-value (M(K + π − π − )-M(K + π − )-M π ) [GeV] Q-value (M(K + π − π − )-M(K + π − )-M π ) [GeV] ＊ Both D 0 mass and Q-value region selected by narrow gate ⇒ More than 10 6 reduction for background events

30 Expected spectra Known Mass & Width in PDG Simulation Λ c (2595) Λ c (2625) Λ c (2880) Λ c @ 1 nb Λ c (2940) Σ c (2800) Σ c (2520) Σ c (2455) ~2000 counts @ N pot = 8.64 × 10 13 (100 days, ε total = 0.5) Λ c (g.s.): 1 nb production cross section • Production ratio for excited states - Background level and reductions were precisely studied. • ＊ Achievable sensitivity of 0.1 − 0.2 nb: (3 σ level, Γ < 100 MeV)

Key devices RICH High-rate detector DAQ

32 Requirements • Small production cross section of π − p → Y c * D * − ⇒ High-rate beam - 6 × 10 7 /spill (30 MHz) ＊ High-rate detectors • Huge background events from hadronic reaction ⇒ Good PID performance - Wide momentum range: 2 − 16 GeV/c ＊ Ring image Cherenkov counter • High speed data taking for high production rate ⇒ DAQ system with recent techniques ＊ Pipelined front-end modules with high speed data link ＊ On-line event reconstruction

33 RICH: Design & simulation Conceptual design Huge background by hadronic reaction • - Wrong PID of π + or proton as K + ⇒ 20 times higher contribution ＊ 3% wrong PID ⇒ Background × 2.4 High-momentum PID • - Wide momentum range: 2-16 GeV/c ⇒ Hybrid RICH - Aerogel (n=1.04) + C 4 F 10 gas (n=1.00137) Detector plane: 2 × 1 m 2 • - Segment size: 5.4 cm - MPPC (>3 × 3 mm 2 size) + Light guide Spherical mirror: ~3 m diameter • Performances • - Efficiency of K, π , p: ~99% - Wrong PID: 0.10%( π → K) and 0.14%(p → K) ⇒ Background × 1.05 Reconstructed Cherenkov angle

34 RICH: Test experiment Experimental setup To check • - Spherical mirror response - MPPC performance ⇒ Dependence on both positions and angles Mirror MPPC plane GeV- γ beam line in ELPH • - 700 MeV electron beam - Radiator: Air - MPPC: 8 × 8 array Preliminary result • Hit pattern Measured Cherenkov angle - Cherenkov angle was clearly reconstructed. ○ θ Chere. = 24 msr ○ ∆θ Chere. ~ 3.0 msr(rms) - Other analysis on-going ＊ Feedback to realistic design