TPM1 Drift Velocity (Re: Drift Velocty Variations of TPM)

From: J.H. Lee (jhlee@sgs1.hirg.bnl.goV)
Date: Fri Dec 14 2001 - 15:41:55 EST

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    Dear Trine and Others,

Probably what we have to do for calibrating the TPM1 drift velocity is
parameterize some of the observables you've mentioned with the measured
DVM values, and then we can use either values for the drift velocity.
Projecting TPM1 tracks to Fibers might be a little bit tricky for the most
of
the physics runs since there is a vertical focusing effect due to the
magnetic
field.  But one of the possibilities is that we use TPM2 Fiber information
in
zero-field runs, and comapare the measured positions of TPM1 tracks in the
Fibers with the DVM values to get a scale factor (hopefully it's a
constant).
Then  it's just drift velocity = DVM value*scale factor.
Here is a y distribution of the TPM1 tracks projected to the Fibers on the
front of TPM2 for the run 5823 (D5=0).  The measured distances (integrated
over x) between two Fibers are consistent  with the physical separations (2
cm)
for this run,

Fiber2-Fiber3 =  2.305-0.315 = 1.99 cm
Fiber3-Fiber4 =  0.315+1.73  = 2.045 cm
Fiber4-Fiber5 = -1.73+3.74   =  2.01 cm,

which means that the TPM1 drift velocity we used (1.7) is correct for this
particular run.    I'm looking at some more Fiber data from zero-field
runs, which we don't have much, with DVM values to see if we can
just scale them with a constant factor.

JH


> Dear JH, Ian and others,
> ...
> Also what's the most efficient / reliable way to determine it for TPM1
> which doesn't have fibres?  Is it safe to assume proportionality to
> the TPM2 variations (or DVM runs) or should one do more careful studies
> of track intersection with beam plane and TPM2 fibres, MRS track match
> parameters, bottomcluster positions etc. etc. ....
> ...
>                                          Trine
    tpm1_fiber.gif

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