w and r± sources of p0 background in PRIMEX

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 !

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±

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

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

production angle distributions for w and r used in MC

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

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

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

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

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