Re: CDC hits in MC data

[David Lawrence <davidl@jlab.org>]

Hi Mark,

    Want you want is to get the DCDCTrackHit objects rather than the 
DCDCHit objects. These two have a 1:1 correlation, but the DCDCTrackHit 
has a pointer to a DCDCWire object which has the info you want. Note 
that DCDCWire inherits from DCoordinate system which has an "origin" 
member that points to the center of the wire in the standard lab 
coordinate system in cm. The "udir" member points in the direction along 
the wire (including any stereo tilt). The "L" member gives the total 
length of the wire.

    The "tdrift" member of the DCDCTrackHit class gives the drift time 
plus time of flight from the vertex (at t=0 by definition) in ns.

    I don't know that any formal documentation currently exists of this 
information so feel free to ask if you have additional questions.

Regards,
-David

Mark M. Ito wrote:
> Software Gurus,
>
> I am trying to get cdc data to use in my track fitter. If I do an 
> hd_dump on the hddm file Simon graciously provided, I see the 
> information listed below. My questions:
>
> What are the units of t?
> Do I need to know some other reference time?
> How to I get the geometry information for ring 3, straw 13?
>
> What I really need of course is a pointer to the documentation of 
> course. Thanks in advance!
>
>  -- Mark
>
> DCDCHit:
> ring: straw:    dE:    t:
> --------------------------
>    1     10  0.000    60
>    2     11  0.000    73
>    3     13  0.000    86
>    4     16  0.000    95
>    5     17  0.000    37
>    6     16  0.000   101
>    7     17  0.000    47
>    8     22  0.000   127
>    9     23  0.000    20
>   10     25  0.000   127
>   11     26  0.000    23
>   12     28  0.000   120
>   13     30  0.000   105
>   14     32  0.000    43
>   15     31  0.000     7
>   16     33  0.000   133
>   17     36  0.000    41
>   18     38  0.000    91
>   19     39  0.000    74
>   20     41  0.000    55
>   21     42  0.000   114
>   22     44  0.000    11
>   23     46  0.000   132
>   24     47  0.000    43
>   25     49  0.000    78
>

-- 

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  David Lawrence Ph.D.
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