from tancredi's message, Re: [BLAST_SHIFTS] runplan 11/12, the integrated current
may not be very accurate.
>Yesterday data was inhibited during ramp/stacking but not the charge,
>so they may be useless in terms of false elicity asymmetries.
instead of putting the epics stuff in init.C, could ntuple.C just write out the
integrated current for each helicity for each run?
--chris
Vitaliy Ziskin wrote:
> 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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