Hi Jason,
If it is possible it would be nice to produce the plot adding Cerenkov cuts:
a + particle you find it in the zeros of the Cerenkov TDC and a - particle
within the corresponding TDC peak. This could clean things up.
Take care,
Ricardo
-----Original Message-----
From: Jason Seely [mailto:seely@MIT.EDU]
Sent: Wednesday, May 14, 2003 9:11 AM
To: Blast_Anaware
Subject: [BLAST_ANAWARE] show_ep_asym.C
hi everyone,
sorry i missed the analysis meeting today - i meant to show the
following, but here it is.
i have put a new macro in /macros/ called 'show_ep_asym.C'. this script
just produces asymmetries and super ratios for each sector, and for both
beam and target asymmetries separately. to run it, just do
root -l show_ep_asym.C run#
i have included a plot as an example. this plot is for runs 303-306
308-309 311-317 323-328, which were supposedly polarized ep runs where
the target was flipped automatically and the waveplate was taken in and
out at each fill. there are four combinations of polarization states:
++, +-, -+, -- where, for example, +- means (beam is +)(target is -).
from these, we can form four separate asymmetries:
A1 = (++ - +-)/(++ + +-)
A2 = (-+ - --)/(-+ + --)
A3 = (++ - -+)/(++ + -+)
A4 = (+- - --)/(+- + --)
so A1 and A2 are the asymmetries for constant beam helicity, but
flipping the target, and A3 and A4 are the asymmetries for a constant
target polarization, but flipping the beam helicity. note that if
everything is normalized properly A1 = -A2, A3 = -A4, A1 = A3, A2 = A4.
by comparing these asymmetries to each other, we should be able to get a
handle on the false asymmetries, and also spot any measured asymmetry
since, for example A1 and A2 will differ by a minus sign.
anyway, please see the plot. as it stands, i don't think we are seeing
any asymmetry yet. to produce the plot, the only cuts i made were to
ask for a + particle on one side and a - particle on the other, that
their vertex was within z = +/- 10 cm (to try to find particles closer
to the center of the target where the polarization should have been
higher) and an adc cut ("(atl>5000&&atr<5000)||(atr>5000&&atl<5000)").
there is more to be done here, but i just wanted to send the plot out
and let people know it's there so as the polarized data rolls in, we can
use this script to find asymmetries.
thanks,
jason
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jason seely
26.650.b
massachusetts institute of technology
77 massachusetts avenue
cambridge, ma 02139-4307
email: seely@mit.edu
phone: 617.253.4772/6734
html: web.mit.edu/seely/www
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