[Halld-cal] effective velocity in the BCAL

[Zisis Papandreou]

Hi folks:

just a brief followup from our discussion on the timing calibration for the BCAL.  Andrei is working on producing plots to investigate effects that were suggested during our CALWG meeting.  

As far as philosophy goes, please glance at the paper from Belle (I highlighted a couple of sentences and boxed a table and equation).  Of course, this is a collider experiment and they use a TOF system (rather than a calorimeter) with chambers, but they do use the same philosophy as Andrei in treating v_eff as a parameter.  Their symmetrical situation and using muons gives them v_eff numbers for up and down (forward/backward in their paper) that are very close, but the point is that they do so to optimize timing for their TOF. 

Andrei’s presentation and the Belle paper can be found here:
 http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=3106 <http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=3106>

As we know, showers are nasty beasts in this regard and give different v_eff for different zones, whether layers, cells or up/down ends.  It would be great to deconvolute the geometrical effects and come with a single v_eff value over the whole calorimeter (as it should be since the fibers are similar within ~15%) but this is a daunting task that may introduce big errors and degrade the timing resolution.

We plan to discuss all these things and Andrei’s new plots further at the upcoming CALWG meeting.

Thanks and cheers, Zisis...

Dr. Zisis Papandreou
Professor of Physics, Ph.D., P.Phys.
---------------------------------------------------------
Department of Physics   
University of Regina	    
3737 Wascana Parkway
Regina, SK  S4S 0A2	 CANADA

Phone: (306) 585-5379
Fax: (306) 585-5659
Email:  zisis at uregina.ca <mailto:zisis at uregina.ca>
Website: http://www.uregina.ca/science/physics/people/faculty-research/zisis-papandreou/index.html <http://www.uregina.ca/science/physics/people/faculty-research/zisis-papandreou/index.html>




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