The example program described in the previous section calculates the theoretical signal-to-noise ratio after a total observation time , for a given pair of detectors, and for a given strength of the stochastic background. A related--and equally important--question is the inverse: ``What is the minimum value of required to produce a given SNR after a given observation time ?'' For example, if , then the answer to the above question is the minimum value of for a stochastic background that is detectable with 95% confidence after an observation time . The following example program calculates and displays this 95% confidence value of for the inital Hanford, WA and Livingston, LA LIGO detectors, for approximately 4 months ( seconds) of observation time. (The answer is .) Again, we are assuming in this example program that the stochastic background has a constant frequency spectrum: for . By modifying the parameters in the #define statements listed at the beginning of the program, one can calculate and display the minimum required 's for different detector pairs, for different signal-to-noise ratios, and for different observation times .
Note: As shown in Sec. , the squared
signal-to-noise ratio can be written in the following form:
The omega_min example program can be run in two ways. Without any
uses the detectors defined by SITE1_CHOICE and SITE2_CHOICE. The program can also be run with two command line arguments which specify alternative detector site choices, for example:
machine-prompt> omega_min 23 31
which produces the output:
Detector site 1 = LIGO-WA_enh7 Detector site 2 = LIGO-LA_enh7 S/N ratio = 1.650000e+00 f_low = 0.000000e+00 Hz f_high = 1.000000e+04 Hz Observation time T = 1.000000e+07 sec Minumum Omega_0 = 5.290809e-09