diff options
Diffstat (limited to 'src/test-likelihood.c')
| -rw-r--r-- | src/test-likelihood.c | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/src/test-likelihood.c b/src/test-likelihood.c index f0266b9..45bbfe2 100644 --- a/src/test-likelihood.c +++ b/src/test-likelihood.c @@ -21,7 +21,7 @@ void simulate_cos_theta_distribution(int N, gsl_histogram *h, double T, double t * distribution is simulated as a gaussian distribution with standard * deviation `theta0`. */ int i; - double theta, phi, wavelength, u, qe, index, cerenkov_angle, dir[3], n[3], dest[3], E, p, beta, cos_theta; + double theta, phi, wavelength, u, qe, index, cerenkov_angle, dir[3], n[3], dest[3], E, p, beta, cos_theta, thetax, thetay; i = 0; while (i < N) { @@ -35,7 +35,7 @@ void simulate_cos_theta_distribution(int N, gsl_histogram *h, double T, double t /* Check to see if the photon was detected. */ if (genrand_real2() > qe) continue; - index = get_index(HEAVY_WATER_DENSITY, wavelength, 10.0); + index = get_index_snoman_d2o(wavelength); /* Calculate total energy */ E = T + MUON_MASS; @@ -45,21 +45,28 @@ void simulate_cos_theta_distribution(int N, gsl_histogram *h, double T, double t cerenkov_angle = acos(1/(index*beta)); /* Assuming the muon track is dominated by small angle scattering, the - * angular distribution will be a Gaussian centered around 0 with a - * standard deviation of `theta0`. Here, we draw a random angle from - * this distribution. */ - theta = randn()*theta0; - - n[0] = sin(theta); - n[1] = 0; + * angular distribution looks like the product of two uncorrelated + * Gaussian distributions with a standard deviation of `theta0` in the + * plane perpendicular to the track direction. Here, we draw two random + * angles and then compute the polar and azimuthal angle for the track + * direction. */ + thetax = randn()*theta0; + thetay = randn()*theta0; + + theta = sqrt(thetax*thetax + thetay*thetay); + phi = atan2(thetay,thetax); + + n[0] = sin(theta)*cos(phi); + n[1] = sin(theta)*sin(phi); n[2] = cos(theta); - /* To compute the direction of the photon, we start with a vector in - * the x-z plane which is offset from the track direction by the - * Cerenkov angle and then rotate it around the track direction by a - * random angle `phi`. */ - dir[0] = sin(cerenkov_angle + theta); - dir[1] = 0; + /* To compute the direction of the photon, we start with a vector which + * has the same azimuthal angle as the track direction but is offset + * from the track direction in the polar angle by the Cerenkov angle + * and then rotate it around the track direction by a random angle + * `phi`. */ + dir[0] = sin(cerenkov_angle + theta)*cos(phi); + dir[1] = sin(cerenkov_angle + theta)*sin(phi); dir[2] = cos(cerenkov_angle + theta); phi = genrand_real2()*2*M_PI; |