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Magnetic spectrometer based on the straws operated in vacuum environment

This article discusses the usage of a magnetic spectrometer based on straws operating in a vacuum environment. It presents the first results from the LHC and their physical interpretation.

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Magnetic spectrometer based on the straws operated in vacuum environment

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  1. Magnetic spectrometer based on the straws operated in vacuum environment Yu. Potrebenikov First Results from the LHC and Their Physical Interpretation 19-21 October 2010

  2. Motivations

  3. - +11.5 -10.5 Present measurement (E787/949): BR(K+p+nn) = 17.3 × 10-11(2009 - 7 events) The K+p+nn decays: a clean test of SM CKM unitarity triangle with kaons VudV*ub+VcdV*cb+VtdV*tb=0 • Flavor Changing Neutral Current loop process: sd coupling and highest CKM suppression, proceed via Z-penguin and W-box diagrams • Very clean theoretically: short distance contributions dominate in the matrix element; hadronic matrix element can be related to measured quantities (K+ 0e+ ). SM predictions (uncertainties from CKM elements): BR(K+ + )  (1.6×10-5)|Vcb|4[sh2+(rc-r)2]  (8.0 ± 1.1)×10-11 BR(KL0 )  (7.6×10-5)|Vcb|4h2  (3.0 ± 0.6)×10-11 Unique in K and B physics and extremely sensitive to New Physics

  4. p qKp K+ n n m2miss=(PK-Pp)2 Goal and Principles of the NA62 O(100) (55 ev/year) K+p+nnevents ~ 10% (<7.5 ev/year) background Physics:BR(SM) = 8×10-11 Kaon decay in flight technique Intense proton beam from SPS High energy K (PK = 75 GeV/c) Acceptance 10% K decays ~1013 (4.8*1012/year) Kinematical rejection Veto and particle ID Kaon 3-momentum: beam tracker (2 time) and precise timing (100 ps in GTK) Long vacuum decay region Pion 3-momentum: spectrometer and RICH g/m detection: calorimeters Charged veto: spectrometer K/p - CEDAR p/m/e separation: RICH Resolution requirements: Pp< 1 %, PK 0.3 %, qKp  50-60 μrad

  5. Backgrounds Kinematically constrained Not kinematically constrained 92% of total background 8% of total background • Allows us to define a signal region • K+ p+p0 forces us to split it into • two parts (Region I and Region II) Hermetic span across the signal region Rejection must rely on veotes

  6. Spectrometer

  7. p- p+ p+ K+ ~2.5 m Current Setup Spectrometer vacuum LKr He Kevlar Window Beam Pipe ~120 m • The Straw Trackers operated in vacuum will enable us to: • Remove the multiple scattering due to the Kevlar Window • Remove the acceptance limitations due to the beam-pipe • Remove the helium between the chambers Straw Tracker Setup: vacuum n RICH p+ Straw Trackers K+ n • The Straw Tracker is essential to study ultra-rare-decays in flight

  8. The Magnetic Spectrometer(i.e. the downstream tracker) Magnetic Spectrometer • 4 chambers with 16 layers of straw tubes each Rate: ~ 40 KHz/cm2 (max 0.8 MHz per 10 mm straw) In vacuum, X/X0~0.1% per view Low X/X0 Good space & angle resolution 130 mm per hit 10 cm >5 cm radius beam hole displaced in the bending plane Free for beam particles

  9. Straw

  10. Main parameters Material: Hostaphan RNK 2600with Al (0.075 m at both side) 36 m thickness Cu+Au: (0.050+0.020 m at one side) Material budget (per view): Straws – (0.093 – 0.095) %X0 (450 straws) Wires - 0.0046 %X0 (Luma 861) Gas mixture - 0.010 %X0 (CO2 + CF4 + Isobutene - slow or Ar + CO2 - fast) Inner supports - 0.022 %X0 (Ultem bushes and twisters) Straw dimensions and quality:  - 9.750.05 mm (9.2 mm effective area) Length - 2300 mm (2100 mm active area) Straightness - 0.1 mm Elongation - 2.0 mm per m per 1 kG  increasing - 0.08 mm per 1 atm overpressure Gas flow - 0.16 cm3/min (70 cm3/min per view) Production technology and rate: Ultrasonic weld, 600 - 1200 mm straw per 1 minute

  11. Straw production and quality Seam 0.40 mm Seam 0.85 mm , mm

  12. Main problems of straw welding Still • Dust accommodation on anvil and sonotrode nose • Anti dust actions: • anvil and sonotrode nose coating by specific • metals (W, Co, Re …) • flow gas around anvil • rotation anvil and/or sonotrode • remove coating from tape edge by ultrasonic • …. Zoom x60 D~1 mm

  13. New straw machine design

  14. Simulation From 2006 – GEANT4 + VMC for detector simulation From 2007 – GARFIELD for simulation processes into drift volume: threshold = 4 fC threshold = 6 fC threshold = 12 fC Electron drift lines in a straw Signal shape from ASD-8 chip

  15. Prototypes and experimental results

  16. 48 straws: 36 - Al 12 - Cu+Au Design and assembling of the first straw prototype

  17. Cosmic test in Dubna Residuals Resolution about 110 m cm

  18. Test run 2007 Main goal: estimation of a straw spatial resolution ~90 m to DCH ~127 m from a beam target Gas mixture - CO2+isoC4H10+CF4 (80%:10%:10%) Trigger condition: Q1 x 1-track ~105 triggers/burst (burst - 16.8/4.8 s) TDC resolution – 97.66 ps ASD-8 chip in FE Statistics: Muon beam - 160M Pion beam - 60M Kaon beam - 550M ----------------- Total - 770M

  19. Test run 2008 Burst - 43.0/4.8 s TDC resolution – 195.3 ps CARIOCA and ASDQ chips in FE Non-inflammable gas mixture: CO2+isoC4H10+CF4(82%:5%:13%) Statistics:

  20. Electronics choosing New FE - based on ASDQ chip (120 Ohm; 8-10 mV/fC; 10-12 ns peaking time, 4200 e noise) - based on CARIOCA chip (45 Ohm; 14 mV/fC; 12-14 ns peaking time, 2000 e noise)

  21. Spatial resolution & efficiency CO2+isoC4H10+CF4 (80%:10%:10%), low rate Efficiency 99.98% Th=6 fC Th=12 fC R=4.7 mm 2400V 2400V 2500V 2500V 2600V 2600V

  22. Straw resolution vs R for different gas mixtures Beam test CARIOCA Th=10 fC Gas gain G=2x10**5 Garfield + CARIOCA Th=10 fC Gas gain G=2x10**5 Ar/CO2 CO2/isoC4H10/CF4 Resolution (cm) Residual (µm) R (cm) R (cm) HOD trigger resolution: ~ 1.3 ns (instead 0.2 ns in 2008)

  23. Ar/CO2: straw rate capability study 2 5 7 10 13 15 1 3 6 9 11 14 30 27 25 22 19 17 31 29 26 23 21 18 14 11 9 6 3 1 15 13 10 7 5 2 30 27 25 22 19 17 31 29 26 23 21 18 1 6 7 Straw efficiency vs beam rate (track: 6 hits in the 6 first layers ch2≤2, straw in the 7-th layer – tested) Straw residual vs beam rate for R ~4.45 mm (track: 6 hits in any 7 layers)

  24. New straw prototype

  25. Straw view design

  26. Gas manifolds and WEBs

  27. Beam test 2010 • Goals: • test of straw prototype • wires positioning (vertical scan – dY=52 mm) • straw bending • check grounding concept • cross-talks study • test 4 new front-end boards based on CARIOCA • TDC binning (0.1 ns/ch ) • DAQ (based on TELL-1 as a RO module) • straw spatial resolution and efficiency study • straw rate test: • total rate capability – up to0.65 MHz per straw • local rate capability – up to 200 kHz/cm2=> (100-200) kHz per 1 cm of wire (Fe-55, Eγ=5.9 KeV) • Gas mixtures: Ar/CO2 (70:30), Ar/CO2 (80:20) – fast gas mixtures • CO2/isoC4H10/CF4 (90:5:5) – slaw gas mixtures • Thresholds: (5-7) fC • Gas gain: 4·104 - 2·105 • Beam:pions, muons

  28. Full scale prototype – Module-0

  29. Final detector design

  30. Production company

  31. Assembly tooling FEM calculation of deformations and stresses 31

  32. Combination design: ring + square shape

  33. Data Base for detector production http://na62.jinr.ru/straw Page for short description and latest news

  34. Summary and conclusion

  35. The straw detector switching to production…. • Module 0 fabrication in November and start straw insertion in January • A few critical issues/decisions in the fall (December): • Full straw validation (material, metallization and welding) • FE choice from studies in the lab and test beam results in 2010 • Choice for the readout • Run 2011: one or two straw modules with other NA62 some detectors

  36. Thank you!

  37. Located in the same hall of NA48 Proposal to Measure the Rare Decay K+p+nn at the CERN SPS (NA62) CERN-SPSC-2005-013 SPSC-P-326 Schedule September 2005: presented at CERN SPSC December 2005: R&D endorsed by CERN Research Board Start of test beams at CERN in 2006 2007 - 2008: prototypes construction and test at CERN and Frascati beams November 2008 - SPSC decided to recommend NA62 for approval. The SPSC Recommendation was endorsed by the CERN Approved by the CERN Research Board (December 5, 2008) 2009 – 2012: Technical design and construction 2013 - Start of data taking

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