User name A. Deur
Log entry time 12:04:55 on August25,2003
Entry number 113454
This entry is a followup to: 108004
keyword=more on pions, pid and EMC effectI looked in more details to the pion contamination to see if the pi/e estimate from the online replay is reliable. I also tried to understand more about the origin of the pions.
I looked at an empty ref cell run (4058), and N2 run (4059) and a pol He3 run (4060) from kinematic 12.40, where the pion contamination is the worst.
Using the online replay, I get (after online replay cut, exept of course the pid cuts):
pi/e for empty ref cell: 97.2
pi/e for nitro ref cell: 2.89
pi/e for pol. 3He cell: 4.28
Using my own good acceptance cuts and good pid cuts (see fig 1 for the shower/preshower cuts, I get
pi/e for empty ref cell: 90+/-15 (the uncertainty comes from removing the glass window)
pi/e for nitro ref cell: 2.87
pi/e for pol. 3He cell: 4.19
So we are in good shape.
Also I looked at the normalized rate coming from pions:
empty ref cell: 0.15 kHz/uA
Nitro ref cell: 1.41 kHz/uA
Pol. 3He cell: 0.33 kHz/uA
so for 3He production runs at this kinematics, half of the pions are from the window.
This does not contradict the previous entry 108004: The half we see from the window is greatly supressed by the acceptance. So we still have a much bigger pion production from the window, even if it contributes only to half of the pion we finally get.
If I remove the pion from the glass window, and I normalized to the pressure inside the cell (time 2 for N2 since it is a di-atomic molecule), we get the following pion rates:
Nitrogen: 0.074 kHz/uA/atmosphere
Pol. 3He: 0.015 kHz/uA/atmosphere
So we have about a factor 4.9, very close to the nucleon ratio for the two nuclei: 14/3=4.7
It seems we don't see much EMC effect here !
FIGURE 1
