Privacy and Security Notice
two pion production
Privacy and Security Notice
Privacy
and Security Notice
Privacy
and Security Notice
Multi-pion
production
- Used the program , genev_Linux , to produce the data files
for multi-pion electroproduction. In the input file, genev.inp, one can
set which multi-pion channels to use by picking different channels.
Initially I used just channel 30 (
gamma +
p ---> P + PI+ + PI- (MODEL)) to produce
data file 2pi.data . Later
to get more than 2pi, I ran the code using channels 21,27,28 and 30 (
listed in table) and produced the file multpi.data . The input file was
run with 5496 MeV beam energy and range of Q2 between 4 and 7 GeV^2.
Channel number
|
Reaction
|
21
|
Gamma +
P ---> P + PI+ + PI-
+ PI0 |
27
|
Gamma +
p ---> pi+ + pi+ + pi-
+ pi- + p
|
28
|
gamma +
p ---> pi+ + pi+ + pi-
+ pi- + pi0 + p
|
30
|
gamma
+ p ---> P + PI+ + PI- (MODEL)
|
The program
and data file are in /work/hallc/e01002/2pi_genova.d/genev/
. The
program randomly generates p(e,ep) events
according to a weight from Hall B cross section data
at Q2 = 2 which is extrapolated to higher Q2 by a dipole form
factor.
- The file genev.f was
modified. Commented out the write statement to unit=95 and introduced a
write statement to unit=20 ( fort.20
file). The fort.20 file
contains
one line for each event and the line contains the electron momentum
component in the x direction, electron momentum component in the y
direction,electron momentum component in the z direction, total
electron momentum, electron mass, the proton momentum component
in the x direction, proton momentum component in the y direction,proton
momentum component in the z direction, total proton momentum,
proton mass. This is just to make the file size smaller.
- In the file , bcs.inc,
the parameter nbcs was
changed from 700000 to 3000000. This allowed more events to be produced
when running the code. To get a large number of events the code had to
be run many times.
- Presently 2pi.data
has 921,220 events. To look at the event distribution, ntup.kumac
reads in multpi.data ,
creates an ntuple and creates the histograms using the program, calc.f .
A plot of the Q2, W , electron momentum and
proton momentum distributions. A plot of
the electron and proton theta and phi. The dips near 180 and 360
degrees are due to the rejection of events with electron and proton on
same side of the beam which happens 88% of the time. A plot of the difference between electron and
proton phi angles shows that
for most events the electron and proton are in the same plane.
- Modified SIMC to read in data from 2pi.data which is a link to the
file multpi.data in /work/hallc/e01002/2pi_genova.d/genev. So SIMC
doesn't
randomly pick the kinematics for the event. Each event is read from the
file. The polar angles, theta
and phi, are calculated. Then
the electron phi angle is
randomly rotated to be between -4 and +4 degrees and the proton phi angle is also rotated by the
same amount as the electron phi.
The angles relative to the spectrometer coordinate system are
calculated. Then the electron is tracked through the SOS and the proton
is tracked
through the HMS.
- Comparing data to MC
For each W range made comparison between data and mult-pi MC.
Use
standard cuts to identify electrons and protons. No cuts to further
reduce radiative tail. In column " Plots comparing MC to data" are
links to web pages which have links to data/mc comparison for all
kinematics settings of the SOS angle=47.5 run. For each HMS angle and
momentum there is a link to a plot which has 4 histograms. The upper
left plot is the raw counts of the data versus missing mass squared
(MM2). The upper right plot is the raw counts of the multpi MC versus
MM2.
The lower left plot is the ratio of the data counts to the multpi MC
counts summed over three missing mass squared regions of 0.07
< MM2 < 0.2 or 0.35 <
MM2 < 0.55 or 0.68 <
MM2 < 0.95.
In the lower right plot is
the data compared to the multpi MC ( red in plot) normalized by the
ratio.
In column "Plots of ratio" is a plot of the data/MC ratio normalized by
the charge and correction factor of the setting for each HMS angle
plotted as a function of the HMS momentum.