move everything to src directory

1 files changed, 260 insertions, 0 deletions

diff --git a/src/muon.c b/src/muon.c
new file mode 100644
index 0000000..4b46769
--- /dev/null
+++ b/src/muon.c
@@ -0,0 +1,260 @@
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_spline.h>
+#include <math.h>
+#include "optics.h"
+#include "quantum_efficiency.h"
+#include "solid_angle.h"
+#include "pdg.h"
+#include "vector.h"
+#include "muon.h"
+#include "sno.h"
+#include "scattering.h"
+
+static int initialized = 0;
+
+static double *x, *dEdx, *csda_range;
+static size_t size;
+
+static gsl_interp_accel *acc_dEdx;
+static gsl_spline *spline_dEdx;
+
+static gsl_interp_accel *acc_range;
+static gsl_spline *spline_range;
+
+static const double MUON_CRITICAL_ENERGY = 1.029e6;
+
+static int init()
+{
+    int i, j;
+    char line[256];
+    char *str;
+    double value;
+    int n;
+
+    FILE *f = fopen("muE_water_liquid.txt", "r");
+
+    if (!f) {
+        fprintf(stderr, "failed to open muE_water_liquid.txt: %s", strerror(errno));
+        return -1;
+    }
+
+    i = 0;
+    n = 0;
+    /* For the first pass, we just count how many values there are. */
+    while (fgets(line, sizeof(line), f)) {
+        size_t len = strlen(line);
+        if (len && (line[len-1] != '\n')) {
+            fprintf(stderr, "got incomplete line on line %i: '%s'\n", i, line);
+            goto err;
+        }
+
+        i += 1;
+
+        /* Skip the first 10 lines since it's just a header. */
+        if (i <= 10) continue;
+
+        if (!len) continue;
+        else if (line[0] == '#') continue;
+        else if (strstr(line, "Minimum ionization")) continue;
+        else if (strstr(line, "Muon critical energy")) continue;
+
+        str = strtok(line," \n");
+
+        while (str) {
+            value = strtod(str, NULL);
+            str = strtok(NULL," \n");
+        }
+
+        n += 1;
+    }
+
+    x = malloc(sizeof(double)*n);
+    dEdx = malloc(sizeof(double)*n);
+    csda_range = malloc(sizeof(double)*n);
+    size = n;
+
+    i = 0;
+    n = 0;
+    /* Now, we actually store the values. */
+    rewind(f);
+    while (fgets(line, sizeof(line), f)) {
+        size_t len = strlen(line);
+        if (len && (line[len-1] != '\n')) {
+            fprintf(stderr, "got incomplete line on line %i: '%s'\n", i, line);
+            goto err;
+        }
+
+        i += 1;
+
+        /* Skip the first 10 lines since it's just a header. */
+        if (i <= 10) continue;
+
+        if (!len) continue;
+        else if (line[0] == '#') continue;
+        else if (strstr(line, "Minimum ionization")) continue;
+        else if (strstr(line, "Muon critical energy")) continue;
+
+        str = strtok(line," \n");
+
+        j = 0;
+        while (str) {
+            value = strtod(str, NULL);
+            switch (j) {
+            case 0:
+                x[n] = value;
+                break;
+            case 7:
+                dEdx[n] = value;
+                break;
+            case 8:
+                csda_range[n] = value;
+                break;
+            }
+            j += 1;
+            str = strtok(NULL," \n");
+        }
+
+        n += 1;
+    }
+
+    fclose(f);
+
+    acc_dEdx = gsl_interp_accel_alloc();
+    spline_dEdx = gsl_spline_alloc(gsl_interp_linear, size);
+    gsl_spline_init(spline_dEdx, x, dEdx, size);
+
+    acc_range = gsl_interp_accel_alloc();
+    spline_range = gsl_spline_alloc(gsl_interp_linear, size);
+    gsl_spline_init(spline_range, x, csda_range, size);
+
+    initialized = 1;
+
+    return 0;
+
+err:
+    fclose(f);
+
+    return -1;
+}
+
+double get_range(double T, double rho)
+{
+    /* Returns the approximate range a muon with kinetic energy `T` will travel
+     * in water before losing all of its energy. This range is interpolated
+     * based on data from the PDG which uses the continuous slowing down
+     * approximation.
+     *
+     * `T` should be in MeV, and `rho` should be in g/cm^3.
+     *
+     * Return value is in cm.
+     *
+     * See http://pdg.lbl.gov/2018/AtomicNuclearProperties/adndt.pdf. */
+    if (!initialized) {
+        if (init()) {
+            exit(1);
+        }
+    }
+
+    return gsl_spline_eval(spline_range, T, acc_range)/rho;
+}
+
+double get_T(double T0, double x, double rho)
+{
+    /* Returns the approximate kinetic energy of a muon in water after
+     * travelling `x` cm with an initial kinetic energy `T`.
+     *
+     * `T` should be in MeV, `x` in cm, and `rho` in g/cm^3.
+     *
+     * Return value is in MeV.
+     *
+     * See http://pdg.lbl.gov/2018/AtomicNuclearProperties/adndt.pdf. */
+    double a, b, range, T;
+
+    if (!initialized) {
+        if (init()) {
+            exit(1);
+        }
+    }
+
+    range = get_range(T0, rho);
+
+    /* This comes from Equation 33.42 in the PDG Passage of Particles Through
+     * Matter article. */
+    b = log(1 + T0/MUON_CRITICAL_ENERGY)/range;
+    /* Now we compute the ionization energy loss from the known range and b. */
+    a = b*T0/(exp(b*range)-1.0);
+
+    /* Compute the kinetic energy after travelling a distance `x` in the
+     * continuous slowing down approximation. */
+    T = -a/b + (T0+a/b)*exp(-b*x);
+
+    if (T < 0) return 0;
+
+    return T;
+}
+
+double get_dEdx(double T, double rho)
+{
+    /* Returns the approximate dE/dx for a muon in water with kinetic energy
+     * `T`.
+     *
+     * `T` should be in MeV and `rho` in g/cm^3.
+     *
+     * Return value is in MeV/cm.
+     *
+     * See http://pdg.lbl.gov/2018/AtomicNuclearProperties/adndt.pdf. */
+    if (!initialized) {
+        if (init()) {
+            exit(1);
+        }
+    }
+
+    return gsl_spline_eval(spline_dEdx, T, acc_dEdx)/rho;
+}
+
+double get_expected_charge(double x, double T, double *pos, double *dir, double *pmt_pos, double *pmt_normal, double r)
+{
+    double pmt_dir[3], cos_theta, n, wavelength0, omega, theta0, E, p, beta, z, rho, R;
+
+    z = 1.0;
+
+    SUB(pmt_dir,pmt_pos,pos);
+    normalize(pmt_dir);
+
+    if (DOT(pmt_dir,pmt_normal) > 0) return 0;
+
+    /* Calculate the cosine of the angle between the track direction and the
+     * vector to the PMT. */
+    cos_theta = DOT(dir,pmt_dir);
+
+    /* Calculate total energy */
+    E = T + MUON_MASS;
+    p = sqrt(E*E - MUON_MASS*MUON_MASS);
+    beta = p/E;
+
+    omega = get_solid_angle_approx(pos,pmt_pos,pmt_normal,r);
+
+    R = NORM(pos);
+
+    if (R <= AV_RADIUS) {
+        rho = HEAVY_WATER_DENSITY;
+    } else {
+        rho = WATER_DENSITY;
+    }
+
+    /* FIXME: I just calculate delta assuming 400 nm light. */
+    wavelength0 = 400.0;
+    n = get_index(rho, wavelength0, 10.0);
+
+    if (beta < 1/n) return 0;
+
+    /* FIXME: is this formula valid for muons? */
+    theta0 = get_scattering_rms(x,p,beta,z,rho);
+
+    /* FIXME: add angular response and scattering/absorption. */
+    return 2*omega*2*M_PI*FINE_STRUCTURE_CONSTANT*z*z*(1-(1/(beta*beta*n*n)))*get_probability(beta, cos_theta, theta0)/(sqrt(2*M_PI)*theta0);
+}