Check the eloss effect

eps files

10 Run ( Period 3 ) :

run 55560, 55565, 55568, 55570, 55573, 55574, 55576, 55580, 55585, 55593

the topology γ p -> p π+ π- (All detected)
ngrf = 1
tagrid -> same for all particles
difference between z-vertex of any pair of particles < 5 cm
using the eloss correction updated at May 26, 2010

To check if our FROST eloss do work or not, I compare the ratio of (calculated photon energy - measured photon energy) to measured photon energy. In this research, I used the topology γ p -> p π+ π- (). That is, all particles are detected and there is no missing particle. However, In my data, there are other situations. For example, γ p -> p π+ π- γ or γ p -> p π+ π- π0. To remove these unuseful decay mode, I made the cut of mising mass and missing momentum.

1. In the z - vertex position

The FROST experiment has three kinds of targets; butanol, carbon, and ch2. I make 2-D histogram. The y-axis value has {calcaulated photon energy - measured photon energy}/{measured photon energy}. The x-axis has Z-vertex position taken from MVRT bank. In y-axis, each bin value is 0.001 (no unit) and in x-axis, a bin size is 1 mm. I have not applied any momentum correction in this research.

Before Eloss Correction	After Eloss Correction

In the upper histogram, there is 400 bins on x-axis. I have made the projected histograms every 5 bins and then fitted them using the gaussian function. The results are presented in the following table.

Before Eloss Correction	After Eloss Correction
Butanol	Butanol (Eloss)

The mean and sigma values of the gaussian are used to make the following histogram.

Before Eloss Correction	After Eloss Correction

py projection - Sigma	py projection - Sigma (Eloss)

2. In the measured photon beam

The y-axis is the same with before histograms and the x-axis value has the measured photon energy. In x-axis, a bin size is 20 MeV. The first row is for the butanol target, the second the carbon, and the last row histograms are from Ch2 target.

Before Eloss Correction	After Eloss Correction

To find out the position of the peaks in the upper histograms exactly, histograms are sliced every five bins (100 MeV). I fitted them using the gaussian function. The results are expressed in the following table.

Before Eloss Correction	After Eloss Correction
Butanol	Butanol (Eloss)
Carbon	Carbon (Eloss)
CH2	CH2 (Eloss)

Before Eloss Correction	After Eloss Correction

py projection - Sigma (Butanol)	py projection - Sigma (Eloss & Butanol)

py projection - Sigma (Carbon)	py projection - Sigma (Eloss & Carbon)

py projection - Sigma (CH2)	py projection - Sigma (Eloss & CH2)