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Raw A_LL vs Mass

Updated on Fri, 2012-12-21 12:32. Originally created by sgliske on 2012-12-20 19:05.
I've computed the A_LL using the raw (non background subtracted) number of pi0 candidates, in four different mass regions:
  1. Low mass: 0-0.1 GeV
  2. Peak: 0.1-0.2 GeV
  3. Above peak: 0.2-0.35 GeV
  4. High mass: 0.35-0.5 GeV

Comment on expected backgrounds

There are several different backgrounds.  The prodimant ones are considered to be:
  • gamma -> e+ e- (not too close to the EEMC face) and make the pair from the e+ e-  (peaked in shape, with mean slightly above the pi0 peak, and extending across most of the mass range)
  • combinatorics, including combinations with leptons from photon conversion (generally a rather flat and broad distribution, extending across most of the mass range)
  • Low mass, due to single clusters reconstructed as two clusters (peaked at low mass, extending slightly into the pi0 peak region, but with a definite max value)
  • Low mass, gamma -> e+ e- close to the EEMC face (small seperation distance implies localized at low mass--more details forthcoming)

 



Low Mass (0 to 0.1 GeV)


The last point is off scale, and is 
-0.306327 +/- 0.181745

Fitting to a constant:

Chi2                      =      13.1571
NDf                       =            6
p0                        = -0.000638024   +/-   0.0225805
consistant with zero -0.0282555

Mass Bin 2 (0.1 to 0.2 GeV)


Fitting to a constant 
Chi2                      =      1.22369
NDf                       =            6
p0                        =    0.0139913   +/-   0.0120544  
consistant with zero .

Mass Bin 3 (0.2 to 0.35 GeV)


Fitting to a constant: 
Chi2                      =      9.86854
NDf                       =            6
p0                        =    0.0104235   +/-   0.0278236  
consistant with zero 0.374627

Mass Bin 4 (0.35 to 0.5 GeV)


Fitting to a constant: 
Chi2                      =      6.15271
NDf                       =            6
p0                        =     0.011753   +/-   0.0418064  
consistant with zero 0.281129

Conclusions

While there is a significant amount of noise in the off peak data points (due to limited statistics), all off peak points are consistant with zero to a high degree with no obvious systematic trends.  The fits to a constand are at most 0.4 sigma from zero, with the reduced chi^2 of the fits being between about 1 to 2.2.  There is no apperent asymetry in the background.  The peak has a stronger indication of a signal, but the fit to a constant is still only 1.2 sigma from zero--3 times the maximum value of peak, but still not a statistially significant indication of an asymmetry.
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