Title: TOF%20Tracking%20What%20have%20we%20learned%20-%20What%20do%20we%20need?
1TOF TrackingWhat have we learned - What do we
need?
- E. Johnson, N. Khan, W. Skulski, F. Wolfs
- PHOBOS Time-of-Flight Group
- University of Rochester
- Rochester, NY 14627
2Outline
- Straight-line tracking
- Correlation between SPECN track and TOF
multiplicity. - How well does it work?
- What have we learned?
- Curved tracking
- Correlation between SPECN track and TOF
multiplicity. - How do we make it work?
- How well does it work?
- What have we learned so far?
- TOF PID with curved tracks
- Does it work?
- What do we need to optimize TOF PID?
3Straight-line tracking
- Use Inkyu Parks code to create straight-line
tracks. - The number of hits on the TOF is about 2 - 3
times the number of reconstructed tracks (vertex
dependent). - A clear correlation exists between the hits on
the TOF and the straight-line tracks.
z lt 1 cm
4Straight-line Tracking
- Create straight-line tracks
- Use theta-track to extrapolate to TOF
- Use hits on last two planes to extrapolate to TOF
- Conclude that using the last two hits improves
TOF - SPEC matching.
??TC 0.3 ??TB 0.2
5Impact of multiplicity on TOF trackingMust use
y position to improve Signal/Noise!!
6Using straight-line tracks for vertical position
calibration of the TOF
- The vertical position of the TOF scintillators
can be determined using the vertical position
information from the track. - Due to vertical segmentation of last silicon
planes, we need to use the azimuthal track angle. - A clear correlation is observed between y(track)
and y(TOF). - Procedure works nicely for the central
scintillators, but not for those near 32.5 and 90
degrees.
7Curved Tracks and TOF Multiplicity
- The number of straight-line tracks in all layers
of SPECN with field-off scales with the TOF
multiplicity (the number of TOF hits is 2 - 3
times the number of spectrometer tracks). - The number of straight-line tracks in the first 6
layers of SPECN with field-on also scales with
the TOF multiplicity (the number of TOF hits is 2
times the number of straight-line tracks).
8Curved Tracks and TOF Multiplicity
- The number of straight-line tracks in the first 6
layers of SPECN with field-on scales with the TOF
multiplicity. - Number of curved tracks in SPECN peaks at 1,
independent of TOF multiplicity. - Only events with at least two tracks can be used
for TOF-based particle identification.
9Curved Tracking
Simulation for pions
- Use Gunthers DSTs with curved tracks.
- Use last two hits in SPECN and do a linear
extrapolation to the TOF. - Expect a correlated angular shift as a function
of momentum.
10B-, PID 9 Positive charges, bending backward
Correlated Hits.
11B-, PID 8Negative charges, bending forward
Correlated Hits.
12B, PID 9 Negative charges, bending backward
Correlated Hits.
13B, PID 8 Positive charges, bending forward
Correlated Hits.
14Track matchingFirst observations
- Signal to background ratio is poor 15 - 10 for
central events. - Width of the correlated peak is about 5 (FWHM).
- Corrections to be made
- Momentum dependence this reduces the width to
about 2 (FWHM). - Position/angle dependence expect that this will
reduce the width to about 1 (FHWM). - Corrections will improve signal to background
ratio to 11 - 2. - Using the vertical position information will
further improve this ratio.
15TOF PID
- We like to use protons and Kaons to optimize
individual slewing corrections for PMTs. Most
background from secondaries have a shorter
time-of-flight. - Current limitations
- Very few tracks from last data run (728 protons
and 606 Kaons). Only half of these are directed
to the TOF. - To understand procedures, low multiplicity data
are crucial.
B- PID 9
16TOF PID
No T0 correction, no slew correction, and no
path- length correction yet.
- Observed correlation between TOF and P is
consistent with expectations. - What would we like to have?
- 100 protons per scintillator (minimum bias data)
24000 total. - Currently we have at most a few hundred protons
total, mostly from central events. - Achieve good calibration data set by
- Collecting more data (should be ok next run).
- Improving tracking efficiency (get more protons
per event).
B- PID 9
MC
17Summary and To-Do List
- Capability to match SPECN tracks and TOF hits has
been developed for both field-on and field-off
data. - Straight-line tracks useful for vertical position
calibration. - Finish vertical position calibration for
scintillators located close to 32.5 degrees and
90 degrees. - Optimize slewing corrections by using separate
rise times for each PMT channel (various
procedures are under consideration). - Correct TOF for path length variations for curved
tracks. - Use vertical position info to improve matching
efficiency.