Near Detector Tracker. Dean Karlen / U. Victoria & TRIUMF NP04 Neutrino Session - KEK August 25, 2004

Transcription

1 Near Detector Tracker Dean Karlen / U. Victoria & TRIUMF NP04 Neutrino Session - KEK August 25, 2004

2 Overview This talk is a summary of the current ideas for the tracking system for the near detector Draws from presentations given at the ND280m pre-meeting and previous ND280m meetings In particular, contributions from: Katsuki Hiraide Pier Loverre Lucio Ludovici Emilio Radicioni Federico Sánchez D.K. August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 2

3 Design criteria Design criteria for the tracker Good point resolution good muon momentum resolution Good two particle resolution better pattern recognition for more complicated events Low mass to reduce multiple scattering better momentum resolution to reduce dead & non-0 2 target material neutrino cross section measurements Simple, proven design to be built in timely manner there is little time for R&D August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 3

4 Tracker geometry Shape: rectangular UA1/Nomad magnet Size: still to be determined consensus developing that it should be consist of a few section ~1 m long advantages for thick tracking layers: improved momentum resolution increased separation of reaction products reduced dead mass in interfaces easier construction better use of gas as a target material August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 4

5 Detector geometry studies Muon acceptance studied by Katsuki Hiraide µ (4) µ (3) µ (2) Divided into 4 event categories CC-QE FGD Air gap µ-catcher Non-QE # of ev. ratio # of ev. ratio Generated in FV 7,624 6, FGD stopped event 694 9% % 2. Chamber hit event 4,017 53% 4,476 70% 3. Chamber + µ-catcher 2,104 28% % 4. µ-catcher event % 201 August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 5 3%

6 Muon acceptance (cont.) Muon momentum distribution Muon acceptance as a function of µ momentum µ-catcher event Chamber hit event Chamber + µ-catcher event FGD stopped event August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 6

7 Preferred tracker technology: TPC Time Projection Chamber a gas container in which electrons, liberated by traversing ionizing particles, drift towards an endplate uniform electric field, set up by a field cage, is parallel to external magnetic field gas amplification at endplates the position and time of signals at the endplates are recorded to reconstruct the particle trajectories x y 2.5 m ν z 2.5 m E? m August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 7

8 Advantages of TPC Excellent resolution Fine granularity Low mass Proven technology The TPC gas itself can be used as an additional oxygen rich target: eg. 2.5 m 2.5 m 1 m volume of CO 2 = 12.5 kg 4 such modules (50 kg) would provide about 5000 events per year, with very fine granularity similar statistics as SK August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 8

9 CO 2 gas properties very slow at low fields very low diffusion Drift velocity (cm / µs) Transverse Diffusion µm / (d [cm]) trans. diff. ~ long. diff. pure CO E (V/cm) 2 E (V/cm) August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 9

10 TPC with CO 2 For a modest field: 200 V/cm (140 cm drift) ~ 30 kv maximum potential no problem v ~ 1.5 mm/µs ~1 ms maximum drift time no problem given the beam spill interval (seconds) electronics can be slow (cheaper, less noise) very small lorentz angle: ~ 2 at 0.5 T minimum ionizing electon-ion pairs: ~91/cm diffusion: ~ 140 µm / cm 1.7 mm max σ diffusion limits space resolution to ~0.3 mm per 4 mm sample gain: lower, but probably acceptable inexpensive and non-flammable a good target material, rich in O 2 August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 10

11 Magnetic field distortions Because drift velocity is so slow, the sensitivity to the magnetic field direction is very low: example: (Following notes by J. Va vra) here ωτ ~ 0.02 E = ( E,0,0) B = v x v x v y ( B x Bz ωτ v vyz B x,0, ( ) 2 z ωτ v If B z / B x ~ 1% for full 125 cm drift distance, the offset in y is only 0.3 mm ample cosmics can be used to develop corrections B z ) B z << B x B B x August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 11

12 Gas amplification For readout, gas amplification of ~1000 is necessary New technology TPC: micropattern gas detectors for gas amplification: Gas electron multipliers (F. Sauli, 1996) Micromegas (Y. Giomataris, 1996) provide better resolution, granularity significant R&D program underway for the International Linear Collider TPC August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 12

13 Gas electron multiplier TPC 1250 mm E drift = 0.2 kv/cm ~5 mm ~5 mm E transfer 3 kv/cm E induction 3.5 kv/cm V 400 V V 400 V Readout pads August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 13

14 GEM TPC prototypes Several prototypes have been built to prove the concept TPG prototype for MICE: August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 14

15 GEM TPC prototypes University of Victoria prototype (Linear Collider TPC R&D): 30 cm drift 2mm 7 mm pads August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 15

16 Cosmic events in Victoria prototype With P5 gas, 25 cm drift, using DESY magnet transverse diffusion reduced with B field B=0T B=0.9T B=2.5T B=4.5T August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 16

17 Space point resolutions CO 2 transverse diffusion: 140 µm/ cm transverse resolution (mm) B = 0, D t = 700 µm/ cm B = 0.9 T, Dt = 170 µm/ cm target = 0.3 mm projection for 1250 mm B = 1.5 T, Dt = 110 µm/ cm 30 mm drift time (50 ns bins) 300 mm August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 17

18 Near detector TPC concept GEMs or micromegas foils available: cm figure below exaggerates the gaps between foils ν 30 cm August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 18

19 Pad readout: one possibility Behind each GEM have a rectangular array of 4mm x 4mm pads: August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 19

20 Simulation of a GEM TPC Event displays with a minimum ionizing track: Drift distance: cm Drift distance: 130 cm only 25 cm sections of tracks are shown August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 20

21 Muon momentum resolution Using parameterizations from PDG, ignoring multiple scattering in gas: σ x 720 σ 1/ r L 2 N + 4 For L = 1 m, 4 mm samples, σ = 0.3 mm, B = 0.2 T δp p 0.01p [ GeV] For L = 0.5 m, 8 mm samples, σ = 0.3 mm, B = 0.2 T δp p 0.05p [ GeV] August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 21

22 Muon momentum resolution Geant study: (Federico Sánchez) August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 22

23 Multiple scattering in CO 2 Parameterization: cos λ = 0.5 σ ms 1/ r β p [ GeV] cos λ L X 0 δp p L = 0.5 m δp p L = 1.0 m p [ GeV] p [ GeV] August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 23

24 Neutrino events in gas target To see what events in the gas target look like, a sample of NEUT events were generated randomly in the gas volume following images show some of the first 10 events in a small gas volume, 25 cm x 25 cm x 140 cm GEANT was used to generate de in 1 mm steps, insert the produced electrons into GEM-TPC simulation package Charge collected by 4 mm 4 mm pads August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 24

25 Event 1 4 mm x 4 mm pads color: relative signal amplitude: µ p = 85 MeV/c ν p p = 248 MeV/c E = 742 MeV π + p = 547 MeV/c p p = 150 MeV/c August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 25

26 Event 2 µ p = 159 MeV/c p p = 211 MeV/c ν E = 352 MeV p p = 415 MeV/c August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 26

27 Event 4 p p = 280 MeV/c ν E = 2727 MeV µ p = 2636 MeV/c August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 27

28 Event 6 ν π + p = 170 MeV/c µ p = 5846 MeV/c p p = 1048 MeV/c E = 6572 MeV p p = 50 MeV/c proton stops August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 28

29 Event 7 p p = 650 MeV/c ν E = 722 MeV µ p = 492 MeV/c August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 29

30 Electronics considerations About 1 million pads (4mm x 4mm) needed to instrument the TPCs (both sides). occupancy is extremely small for a live time frame of 1 ms there are 10 9 voxels very safe against background hits that accumulate in 1ms multiplexing possible slow shaping & sampling times can be used: 1 µs sampling 2 mm resolution in drift direction faster ADCs can be used to sample many pads $2/channel readout possible in ASIC (?) August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 30

31 Multiplexing option To reduce channel count, could gang pads use arrival times to sort out correct locations (TPG, Emilio Radicioni) Use existing electronics systems (eg. ALICE), and with 60,000 channels, electronics costs could be reduced to 360k Euro August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 31

32 Next steps Conveners of ND280m group request a cost and time schedule for TPC construction Initial ideas by D.K. and E.R.: Tests with existing prototypes can start soon pure CO 2 operation pad geometry ND prototype construction optimistic completion, end 2005 (?) beam test at TRIUMF (?) ND construction largest cost item: electronics August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 32

33 Summary TPC is preferred option for the ND tracker Advantages: better resolution, two particle separation introduces very little extra material we can effectively use the gas as an active target could provide important data (complimentary to the liquid/solid targets) to pin down the ν -O 2 cross sections Much work to be done an interesting project bound to attract new collaborators real work needs to begin right away! August 25, 2004 Near Detector Tracker / Dean Karlen, U. Victoria & TRIUMF 33