1. w and r± sources of p0 background in PRIMEX

2. p0 elasticity distribution observed in PRIMEX (crystal part of Hycal)
Calculation of number of
p0 near the elastic peak
is not enough. We have
to know their spectrum
to check how they affect
fit which we are using to
separate our elastic peak !

3. The following sources of quasielastic p0s were studied:
Coherent w: g A -> w A
Incoherent w: g A -> w N A’
g A -> w D A’
Incoherent r±: g A -> r± N A’
g A -> r± D A’
With consequent decays:
w/r0 -> p0 g; w -> p0 p- p+; r± -> p0 p±

4. w/r decays kinematics: E(p0) / E(w/r) distribution

5. t’ distributions for w and r production used in MC
t’ = |t – tmin|

6. production angle distributions for w and r used in MC

7. cos(qGJ) distributions for w and r used in MC
1+x2
1-x2

8. Distributions obtained from MC were scaled and subtracted from the data
Scale factor for MC data:
Kscale = FMC / Fdata
FMC = Nevent NC / (L Br s)
L – number of atoms per sq. unit
Br – decay branching ratio
s – production cross section

9. p0 elasticity distribution observed (crystal part of Hycal) with simulated background from w and r+ -
w and r+ -
contribution
r+ - only
contribution

10. p0 elasticity distribution with subtracted background from w and r+ -
Elastic peak
parameters
improved

11. dN/dq for original data and with background subtraction (on the level of gg invariant mass spectrum, bin by bin basis)
original
rad. width changes
by ~ -0.8%;
more calculations
will be performed
Subtracted part