Re: [BLAST_ANAWARE] outer detector recon questions

From: zhangchi (zhangchi@general.lns.mit.edu)
Date: Sun Jan 25 2004 - 14:15:02 EST


On Sun, 25 Jan 2004, Adrian T Sindile wrote:

> Hi, Chi, Chris, guys!
> I have been looking at the outer detector info we get (useful for PID) and
> I have a few questions:
> - when SC pad # = -1, that means the track at hand could not be linked to
> any TOF with confidence, right? (see first attachment);
that is right

> - when we are not confident about the TOF, the position is assumed to be
> in the horizontal plane (phi = 0)? (see second attachment);
when SC pad # = -1, please ignore any information related to the LINKED
Tof, position 0 or not, does not have any real meaning anyway.

> - do the above two things have anything to do with the spikes one gets in
> the reconstructed mass (see third attachment)? I am asking this, as I
No. the spikes in recontructed mass come from the "trigger tracks". The
particle linked to the TOF with least TDC. One must make an assumption on
the ID of this particle. when it is assumed to be an electron, the mass of
this track is made electron mass exactly. thus a spike at 0.051MeV. when
it is assumed to be a pi+ or pi-, its mass is 0.139 so you see a spike
there.

masses of other tracks are calculated from TOF and momentum so bear a
resolution, so is the peak arround 900MeV.

The design of our detector causes the ambiguity in the ID of the first
particle. usually it would be an electron but in the program, a set of
possibilities are tested and the best one is adopted.

> think the above two things are also linked with the PID (fourth
> attachment) as the number of counts for PID 42, 43 - unknown positive,
> negative - looks close to the number of counts one gets for TOF pad # = -1.

that is right. 42 and 43 are BLAST home brew(by Chris) generic PIDs. they
are generic positive and generic negative. A track is first given either
42 or 43 after Fast Fit, depend on which way it bends in Blast Field.
Later, if it can be linked to a TOF which makes further PID possible, PID
is then replaced by whatever the program determined it to be. If it does
not linke to TOF, generic PID will not be replaced.

> Thanks!
>
> Adrian
>
> -------------------------------
> Adrian Sindile
> Research Assistant
> Nuclear Physics Group
> University of New Hampshire
> phone: (603)862-1691
> FAX: (603)862-2998
> email: asindile@alberti.unh.edu
> http://einstein.unh.edu/~adrian/



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