Hayes at 13:44, 9 May 2011

2011-05-09T13:44:42Z

← Older revision		Revision as of 13:44, 9 May 2011
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	==Test-fitting matrix elements==		==Test-fitting matrix elements==

-	Once estimated counts are calculated, these can be fed back into Gosia as simulated data to do test ~~fitting~~ of the matrix elements ~~that are desired in the experiment~~. This is done by assigning counts (on an arbitrary scale) and corresponding predicted error bars and entering them into Gosia's file #3. The format of this file is given in the Gosia manual section XXX.	+	Once estimated counts are calculated, these can be fed back into Gosia as simulated data to perform a test fit of the desired measurements (matrix elements). This is done by assigning counts as in the section above (on an arbitrary scale) and corresponding predicted error bars and entering them into Gosia's file #3. The format of this file is given in the Gosia manual section XXX.

-	~~This section~~ is ~~incomplete~~.	+	Refer to the [[Fitting]] page for examples of fits to simulated or real yield data.
		+
		+	Once a fit is obtained, the accuracy can be ascertained by comparing the final values of the matrix elements with those used to simulate the data.
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		+	==Estimating the precision of measurements==
		+
		+	The precision of a desired measurement can be predicted by running a [[correlated error]] calculation following the test fit(s) to simulated data. This provides an estimate of the uncertainties expected in the actual experiment.

Hayes: creation

2011-05-09T13:24:46Z

creation

New page

==Introduction==

In Gosia, 'simulation' can mean simply performing a Coulomb excitation calculation with known matrix elements and initial guesses at the unknowns. This would generally involve an 'OP,INTI' integration over the laboratory solid angle of the particle and Ge detectors. The Gosia output can then be translated into expected counts of each decay transition in a planned beam run.

==Calculation of expected yields==

The expected total p-gamma counts can be obtained from the Gosia output as follows. The output of the integration gives cross sections in mb mg/cm^2/sr in the "YIELD" column:

<pre>
INTEGRATED YIELDS

EXPERIMENT 5 DETECTOR 1
ENERGY RANGE 967.500--- 985.000 MEV SCATTERING ANGLE RANGE 24.000--- 31.000 DEG

NI NF II IF YIELD NORMALIZED YIELD

21 2 3.0 2.0 0.13010E+01 0.94604E-01
21 3 3.0 4.0 0.27412E+00 0.19933E-01
21 20 3.0 2.0 0.16659E-03 0.12114E-04
20 1 2.0 0.0 0.14124E+01 0.10270E+00
20 2 2.0 2.0 0.15701E+01 0.11417E+00
20 3 2.0 4.0 0.36551E-01 0.26578E-02
5 4 8.0 6.0 0.13752E+02 0.10000E+01
4 3 6.0 4.0 0.49997E+02 0.36356E+01
3 2 4.0 2.0 0.10556E+03 0.76756E+01
2 1 2.0 0.0 0.35444E+02 0.25774E+01
********* END OF EXECUTION **********
</pre>

In these yields, the 1/sr units refer to the solid angle subtended by the Ge detector numbered '1' in the Gosia input file. To convert these yields to the expected counts during a beam run, the following formula can be used:

<math>N = 10^{-30} P (N_{Av} / A) Y \epsilon \Delta\Omega</math>

where N is the total p-gamma count expected in the laboratory, P is the total incident number of beam particles during the experiment, <math>N_{Av}</math> is Avogadro's number, A is the mass of the beam particle in g/mol, Y is the yield of the desired transition from the YIELD output, <math>\epsilon</math> is the absolute efficiency for the corresponding gamma-ray energy, and <math>\Delta\Omega</math> is the solid angle subtended by detector #1 above. ''Note that this is equivalent to the formula given in the OP,INTI and OP,INTG sections of the Gosia manual.''

==Test-fitting matrix elements==

Once estimated counts are calculated, these can be fed back into Gosia as simulated data to do test fitting of the matrix elements that are desired in the experiment. This is done by assigning counts (on an arbitrary scale) and corresponding predicted error bars and entering them into Gosia's file #3. The format of this file is given in the Gosia manual section XXX.

This section is incomplete.

Simulation (experiment planning) - Revision history

Hayes at 13:44, 9 May 2011

Hayes: creation