<html>
<head>
</head>
<body text="#000000" bgcolor="#ffffff">
Dear Folks,<br>
<br>
Here is the explanation of gpart vs npart from Stepan. I suggest we
follow his recommendation and use gpart >= 2 with at least two
tracks with dc_stat > 0.<br>
<br>
- Larry<br>
<br>
-------- Original Message --------
<table cellspacing="0" cellpadding="0" border="0" class="moz-email-headers-table">
<tbody>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Subject: </th>
<td>Re: gpart vs npart</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Date: </th>
<td>Tue, 24 May 2011 11:58:00 -0400</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">From: </th>
<td>Stepan Stepanyan <a href="mailto:stepanya@jlab.org"><stepanya@jlab.org></a></td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">To: </th>
<td>Larry Weinstein <a href="mailto:weinstei@jlab.org"><weinstei@jlab.org></a></td>
</tr>
</tbody>
</table>
<br>
<br>
<pre>Dear Larry,
Since you are looking for two charged particles, it always
should be npart>=2. In fact for elastic npart=2. If find
more events with elastic kinematics, that means one of
tracks did not pass timing information. It can be either
time-based tracking (less likely) or TOF information was
way OFF - PID (if SC counters had too high occupancy this
is more likely). Since PID is not an issue for elastic events,
you may want to use gpart>=2 events, but make sure
you select those that have 2 time based tracks, dc_stat>0
for both tracks.
Regards, Stepan
On 5/24/11 11:51 AM, Larry Weinstein wrote:
> Dear Stepan,
>
> Thanks! Is there any reason to analyze gpart tracks or should we
> limit all our analysis to npart tracks? I ask because Puneet found
> about 10% more events passing our elastic cuts when he required gpart
> >= 2 rather than npart >= 2.
>
> - Larry
>
> PS: I am also appalled at the dearth of documentation on our offline
> software.
>
> Stepan Stepanyan wrote:
>> Dear Larry,
>>
>> There is no documentation on that. I sue to have a short writeup
>> link from old offline page but it disappeared for some reason.
>>
>> As for gpart/npart - gpart is number of "geometrically matched
>> particles", no timing information. Npart is number of particles
>> that were found after timing analysis (time based tracks and in
>> time neutral hits). EVNT bank has "gpart" entries, first "npart" of
>> which are particles that passed timing analysis.
>>
>> Regards, Stepan
>>
>> On 5/24/11 10:49 AM, Larry Weinstein wrote:
>>> Dear Stepan,
>>>
>>> Is there any documentation on the difference between gpart and
>>> npart? Are there any cuts on the data other than the number of HBT
>>> and TBT tracks per event?
>>>
>
</pre>
</body>
</html>