Make the beam asymmetry from g1c data

Step 1 : Check the g1c data

g1c_data

column	name	#Bin	description
1	W(1.375-2.325)	19	The center of mass energy, W[01]=1.4, W[02]=1.45, and W[19]=2.3
2	M(π+, π-)	9	The invariant mass the π+ and π- pair
3	M(π+, p)	9	The invariant mass the π+ and p pair
4	cos(θ cm)	9	The cos (θ, c.m.)
5	φ(p)	11	The The azimuthal angle φ of the momentum direction of the π+,π- pair in the c.m.
11	num.of Y+	.	the number of helicity plus
12	num.of Y-	.	the number of helicity minus
13	polarization	.	he average photon polarization in that bin

Step 2 : Find the phi-angle distribution of Y+ and Y-

column 1, 5, 11,and 12 are used to get Y+ and Y- distribution.
For example, the following event has Y+(number 4) and Y-(number 2) in the phi-angle 320-360[degree] at W=1.4
The errors of Y+ and Y- are found by applying Sumw2()

1

1

2

2

9

1.40574

0.29481

1.11776

-0.63567

4.89847

4

2

0.18313

Step 3 : Find the degree of photon beam polarization

The average polarization = ( sum{Pol(Y+)} + sum{Pol(Y-)} )/( num(Y+) + sum(Y-) )

Step 4 : Make the beam asymmetry with the polarization

The beam-asymmetry = (1/ave_pol)*{ (sum(Y+) - sum(Y-))/(sum(Y+) + sum(Y-)) }

Step 5 : Compare the beam asymmetry with P.R.L. plot

	Ic_g1c_Steffen_data.txt