HERA-B%20RICH - PowerPoint PPT Presentation

About This Presentation
Title:

HERA-B%20RICH

Description:

16 ch, using two ASD08 (amplifier, shaper, discriminator) chip each. C4F10 radiator ... Most sensitive geometrical parameter in RICH is placement of photon detectors ... – PowerPoint PPT presentation

Number of Views:156
Avg rating:3.0/5.0
Slides: 23
Provided by: roys95
Category:
Tags: 20rich | hera | scan

less

Transcript and Presenter's Notes

Title: HERA-B%20RICH


1
HERA-B RICH
Fall 99 Status and Prospects
  • University of Texas at Austin
  • University of Barcelona
  • University of Coimbra, Portugal
  • DESY, Hamburg
  • University of Houston
  • Northwestern University
  • J. Stefan Institute and University of Ljubljana,
    Slovenia

2
Detector
Readout Cards 16 ch, using two ASD08 (amplifier,
shaper, discriminator) chip each
Base Board Socket, voltage divider, output
circuitry for 4 multianode PMTs
Photon Detectors
M16 PMT Hamamatsu 16-anode multiplier
Plastic Molding
Lens System 21 image reduction
Spherical Mirrors
Planar Mirrors
Super Module Crate made from plastic molded iron
sheets magnetic shield and mounting structure
C4F10 radiator
1488 M16s 752 M4s
Photon Detectors
3
Photon Detectors
  • ASD Summary
  • 4-8 single hot channels (faulty boards)
  • 3 full boards, 2 half-boards faulty
  • 90 dead channels (broken lines in cables)
  • PMT Summary
  • 6 missing
  • 11 dead (mostly in unpopulated regions)
  • 13 faulty (?)

4
The Bottom Line
  • 98 of channels installed and working
  • Photon yield and resolution agree with design
    report expectations
  • Hardware issues
  • Two fallen mirrors replaced/remounted
  • Traced to poor adhesive batch
  • Safety wires improved
  • System appears stable
  • Radiator gas leaks fixed
  • Improvements to re-circulation-purification
    system implemented
  • Present C4F10 concentration 50
  • Complete filling later this Fall
  • Present efforts concentrating on fine-tuning
    performance

5
Ongoing Activities
  • Studies to refine alignment
  • Correlations with tracking systems to fine-tune
    alignment of individual detector modules/mirrors
  • Refine ring-finding/particle-ID routines
  • Likelihood analyses
  • Speed-up (?) stand-alone ring-finding
  • Monitoring performance/database updates
  • Run-by-run ring-radius determination
  • Hot/dead channels
  • Hardware
  • Gas system review/refill C4F10 by end of year
  • PMTs exchange faulty channels

6
Expected Performance
  • Cherenkov relations
  • Widths of bands
  • Critical RICH parameters which depend on
  • relative photon yield path length/detection
    efficiency
  • D angle error/photon dispersion/optical
    quality/cell size

(independent of qC and p!)
(usually smaller than q2 term)
7
Detected Photon Yields
  • Basic Cherenkov relation independent
    of radiator composition
  • Design value (corresponds to 47L(cm)ltqcgt2
    in PDG notation)
  • Actual limiting angle does depend on radiator
  • Biases in measurement of yield
  • Efficiency in ring-finding
  • Nearby conversion pairs
  • Shadowing by beam-shroud
  • Acceptance

Relative biases will Change with radius
8
Uncorrected Data
  • Yield in pure N2
  • Scan rings with mixed C4F10

9
Issues in Alignment and Resolution
  • RICH measures angles xhit/R, yhit/R
  • Dispersion and granularity set scale
  • sgas 0.4 mrad
  • scell 1.6/?12 mrad ?
  • ? Nphoton 5 - 6
  • Spherical aberrations important
  • Scale as (projection of ray from origin)3
  • Distort ring shape and displace center
  • Analytic expressions for distortions and shifts
    exist at required accuracy

D ? 0.6 mrad sV,H ? 0.15 mrad
Overall goal sV,H ? 0.3 mrad
10
Compare with ECAL
RICH/ECAL vertical residuals (radians)
  • Upper/Lower half-planes have systematic offset
    0.5 mrad
  • Within a half-plane, sV, H 0.7 mrad

11
Self-consistent Test of Alignment
  • Examine Upper/Lower detector yields vs position
  • Symmetry of detector placement w.r.t. mid-plane
    of mirrors
  • Signal/background
  • Define Up/Down photon asymmetry
  • Expect

12
Asymmetry Data
Conclusions
Nominal
  • Photon detectors are close to symmetric (within
    0.2 mrad) in their nominal geometric positions
  • Vertical spot size OK
  • ? (2.8/11.4)?40 mrad
  • Background photons 25
  • Implies occupancy 1, consistent with observed
    occupancies
  • Background is subtracted in usual stand-alone
    ring-finding algorithm

Upper Shifted 4 mm
1 mrad shift
13
How to Reconcile RICH ECAL ?
  • Most sensitive geometrical parameter in RICH is
    placement of photon detectors within respective
    focal planes.
  • dq/dx 0.16 mrad/mm (in focal plane)
  • ECAL and U/L asymmetry data suggest a symmetric
    displacement of each set of supermodules by 2 mm
  • At limit of estimated survey errors
  • Not unique
  • New set of geometrical constants generated with
    this shift

14
Results with Shifted Photon Detectors
  • Mean offsetslt 0.2 mrad
  • Overall RMS 0.7 mrad

15
Position Dependence of Residuals
1 mrad/box
16
Comments on aligning using ECAL
  • Advantages
  • Only system available on regular basis
  • Matches RICH acceptance
  • Disadvantages
  • Not a tracking systemmust make assumptions about
    track directions
  • Efficiencies differ for different particle types
  • Response not uniform/constant
  • Biases apparent at boundaries of active regions
  • Biases due to photon/track overlap
  • Resolution at limit needed for RICH alignment

17
Match RICH rings with OTR tracks
  • TDC information not used
  • Horizontal offset 0.5 mrad
  • RMS horizontalmatch lt 1 mrad
  • Vertical RMS broadened by OTR stereo

18
Preliminary Conclusions on Alignment
  • Small adjustments to nominal detector positions
    are indicated by the data
  • System is at the design level of accuracy with
    only this correction
  • The ultimate accuracy of the RICH will be better
    than the design specification
  • Comparisons will be performed with other tracking
    systems to understand potential optical errors
  • Adjustments to individual detector supermodules
    and mirrors
  • Ultimate accuracy in track direction of 0.3
    mrad/ plane seems feasible
  • Initial matching with OTR promising

19
Critical RICH Parameters
  • Measure N/q2 and D directly from fits to rings
    that match with ECAL
  • No corrections for partial rings

20
Spring 99 Data
  • Critical RICH parameters already at or near
    design specs Design Measured
  • 13,000 10,000-13,000
  • D 1 mrad 0.7 1.0 mrad syst.
    err. 0.5 mrad
  • Particle ID in ECAL/RICH mode differs from design
    mainly because of poor dp/p

21
Consequences for Particle ID
Todays ECAL/RICH tracking
With Design Tracking
22
Summary
  • RICH working at design performance level
  • Photon yields and resolution at or near
    specifications
  • Occupancies as expected (magnet on)
  • Stand-alone ring finding gives post-magnet tracks
    to 0.5 mrad
  • Ongoing effort to institutionalize performance
    monitoring
  • Automatic database updating of critical
    parameters
  • Continuing alignment studies should reduce
    optical errors to below design specifications
  • We encourage the use of RICH information by
    everyone
  • Global alignment studies
  • Physics!!!
Write a Comment
User Comments (0)
About PowerShow.com