I have attempted to look at the beam helicity asymmetry in run 2814 taken last
night with 500k events in it. I used the epics information about the lamda half
plate in/out at the source. The situation for this run is following:
Integrated current for positive helicity: 166.604 Coulombs
Integrated current for negative helicity: 194.006 Coulombs
So, we took slightly more data with negative helicity, where I define negative
helicity as half wave plate in. I added a ntuple variable to the eep ntuple
call "hel" ( the same entry is made into the epics ntuple). When I plotted
the raw paddle hits (normalized to the Intergrated current) from the eep ntuple
the difference between pos and negative helicity was sizable, which makes sence
since we know that the noise is not linear with the current. When I plotted
paddle hits for protons using "plnn" and "prnn" cuts the situation improves.
I include a plot that generated with macro show_hel.C (residing in the development
directory). What is ploted is the number of proton hits in the paddles integrated
over all paddles on the other sides with the appropriate cuts from cuts.C (note that
"plnn[6]" does not exist and thus shows more events) for negative helicity (red)
and positive helicity (black). Top left shows protons on the left and top right
shows protons on the right. Underneath them is the plot for Left side and Right
side asymmetry takes as \frac{N_{-} - N_{+}}{N_{-}+N_{+}}.
More statistics is needed, but I can't include more runs since current init.C
does not load different epics ntuple needed to calculate Integrated current for
each asymmetry.
Let me know what you think.
Cheers, Vitaliy
=====================================================================
Vitaliy Ziskin Tel: (617)253-9209
MIT 26-547 http://www.lns.mit.edu/people/vziskin/
77 Massachusetts Ave
Cambridge, Ma
02139
======================================================================
"For long you live and high you fly
And smiles you'll give and tears you'll cry
And all you touch and all you see
Is all your life will ever be"--Pink Floyd
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