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calcnufromloss.py
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calcnufromloss.py
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#coding=ASCII
"""Calculate the neutrino flux at a far detector from a G4Beamline loss file.
Install the package and add the path to the PYTHONPATH environment variable.
In the Python code, do
import nufromloss
nufromloss.set_detector(det_size), where det_size is a list = [width,
height, distance] of the detector
nufromloss.set_startfrom(z), where z is a float = G4Beamline longitudinal z to
start calculating contributions to the nu flux. Particles before this z will
be discarded.
nufromloss.get_flux(lossfile)
Parameter:
lossfile: str, the path to the G4BL loss file.
Return: A dictionary. Each key is the PDGid of the parent particle, and the
value is a N-by-3 numpy, columns = nu energy, flux, nu PDGid
"""
from __future__ import division
import numpy as np
from src.loadtxt import loadtxt
from src.flux_kinematics import flux_2body, flux_mu
from src.group_by_PDG import group_by_PDG
__all__ = ['set_cut', 'set_detector', "get_flux", "find_decay"]
_det_size = np.zeros(3)
_cut_from_z = None
def set_detector(det_size):
"""Set the detector size
detSize should be a list with three elements,
or an numpy ndarray of the shape [3,]
"""
try:
det_size_cp = np.array(det_size)
if det_size_cp.shape != (3,):
print "detSize should have 3 elements."
return
else:
global _det_size
_det_size = det_size_cp
except Exception as e:
print e
print "Can not convert detSize to an numpy ndarray"
def set_cut(z):
"""Set the longitudianl z for the cut
beam before this z will be discarded.
"""
global _cut_from_z
_cut_from_z = z
def get_flux(lossfile):
"""Calculate the flux at the FD, directly based on the loss beam in the beamline
set_detector and set_cut must have already been used before getnuflux.
"""
if _cut_from_z == None or len(np.nonzero(_det_size)[0]) == 0:
print "setdetector and setcut first."
return None
parents_list = find_decay(lossfile)
parents_list_cut = [ii_parent[ii_parent[:, 2]>=_cut_from_z, :]
for ii_parent in parents_list]
parents_list = parents_list_cut
neutrino_group = {}
for ii_parent in parents_list:
# for each type of parent particle, get its decay products
if len(ii_parent) == 0: continue
neutrino_group[int(ii_parent[0, 7])] = []
flux_2body_tmp = flux_2body(ii_parent, _det_size)
if flux_2body_tmp is not None:
neutrino_group[int(ii_parent[0, 7])].append(flux_2body_tmp)
flux_mu_tmp = flux_mu(ii_parent, _det_size)
if flux_mu_tmp is not None:
neutrino_group[int(ii_parent[0, 7])].append(flux_mu_tmp)
if len(neutrino_group[int(ii_parent[0, 7])]) > 0:
neutrino_group[int(ii_parent[0, 7])] = \
np.row_stack(neutrino_group[int(ii_parent[0, 7])])
else:
neutrino_group[int(ii_parent[0, 7])] = np.array([])
return neutrino_group
def find_decay(lossfile):
"""Find the particles that decayed in a G4Beamline simulation.
At least one daughter of the decay needs to be kept in the loss file
when doing the G4BL simulation.
------
Parameters:
lossfile, str, the path of the G4BL loss file
------
Returns:
all_parents_list, a list of numpy ndarrys (N-by-12), each list member is
a kind of the decayed parent particles at the points of the decay,
in G4Beamline ASCII beam format.
"""
lossbeam = loadtxt(lossfile, 3)
lossbeam_sorted = lossbeam[np.argsort(lossbeam[:, 8]), :]
number_of_loss = lossbeam.shape[0]
# Boolean vector that marks which particle to keep
bool_keep = np.zeros(number_of_loss)
# Iterating through the beam is much faster than filtering out each event.
iterator1 = iterator2 = 0
while iterator2 <= number_of_loss-2:
iterator2 += 1
# If there are no more than 2 particles for this eventID, skip;
if lossbeam_sorted[iterator1, 8] != lossbeam_sorted[iterator2, 8]:
if iterator2 - iterator1 >= 2:
# iterator2 - iterator1 covers all the particles with the
# same eventID, get them:
this_event = lossbeam_sorted[iterator1:iterator2, :]
bool_keep[np.nonzero(np.in1d(this_event[:, 9],
this_event[:, 10]))[0] +
iterator1] = 1
iterator1 = iterator2
if iterator1 != number_of_loss - 1:
# This means at least the last two eventID are the same
this_event = lossbeam_sorted[iterator1:, :]
bool_keep[np.nonzero(np.in1d(this_event[:, 9],
this_event[:,10]))[0] +
iterator1] = 1
# All the decayed particles in this lossbeam:
all_parents = lossbeam_sorted[bool_keep.astype(bool), :]
all_parents_list = group_by_PDG(all_parents)
return all_parents_list