e_pi = hypot4(sim.fPxPi, sim.fPyPi, sim.fPzPi,
AliPID.ParticleMass(AliPID.kPion))
deu.SetXYZM(sim.fPxDeu, sim.fPyDeu, sim.fPzDeu,
AliPID.ParticleMass(AliPID.kDeuteron))
p.SetXYZM(sim.fPxP, sim.fPyP, sim.fPzP,
AliPID.ParticleMass(AliPID.kProton))
pi.SetXYZM(sim.fPxPi, sim.fPyPi, sim.fPzPi,
AliPID.ParticleMass(AliPID.kPion))
hyp = deu + p + pi
decay_lenght = TVector3(sim.fDecayVtxX, sim.fDecayVtxY, sim.fDecayVtxZ)
dl = decay_lenght.Mag()
if hyp.Gamma() == 0 or hyp.Beta() == 0:
continue
ct = dl / (hyp.Gamma() * hyp.Beta())
if hyp.Pt() < 1. or hyp.Pt() > 10.:
continue
hist_ctsim.Fill(ct)
hist_ptsim.Fill(hyp.Pt())
hist_psim.Fill(hyp.P())
hist_etasim.Fill(hyp.Eta())
hist_phisim.Fill(hyp.Phi())
# rec - sim diff
# if sim.fRecoIndex >= 0:
def __init__(self, parse, tree):
#electron and proton energy, GeV
self.Ee = parse.getfloat("main", "Ee")
self.Ep = parse.getfloat("main", "Ep")
print("Ee, GeV =", self.Ee)
print("Ep, GeV =", self.Ep)
#A and Z of the nucleus
self.A = 1
self.Z = 1
if parse.has_option("main", "A"):
self.A = parse.getint("main", "A")
if parse.has_option("main", "Z"):
self.Z = parse.getint("main", "Z")
print("A:", self.A)
print("Z:", self.Z)
#minimal photon energy, GeV
self.emin = parse.getfloat("main", "emin")
print("emin, GeV =", self.emin)
#alpha r_e^2
self.ar2 = 7.297 * 2.818 * 2.818 * 1e-2 # m barn
#electron and nucleus mass
self.me = TDatabasePDG.Instance().GetParticle(11).Mass()
self.mp = TDatabasePDG.Instance().GetParticle(2212).Mass()
self.mn = self.A * self.mp
#nucleus beam vector
nvec = TLorentzVector()
pz_a = TMath.Sqrt(self.Ep**2 - self.mp**2) * self.Z
en_a = TMath.Sqrt(pz_a**2 + self.mn**2)
nvec.SetPxPyPzE(0, 0, pz_a, en_a)
print("Nucleus beam gamma:", nvec.Gamma())
#boost vector of nucleus beam
self.nbvec = nvec.BoostVector()
#electron beam vector
evec = TLorentzVector()
evec.SetPxPyPzE(0, 0, -TMath.Sqrt(self.Ee**2 - self.me**2), self.Ee)
print("Electron beam gamma:", evec.Gamma())
#electron beam energy in nucleus beam rest frame
evec.Boost(-self.nbvec.x(), -self.nbvec.y(), -self.nbvec.z())
self.Ee_n = evec.E()
print("Ee_n, GeV:", self.Ee_n)
#minimal photon energy in nucleus rest frame
eminv = TLorentzVector()
eminv.SetPxPyPzE(0, 0, -self.emin, self.emin)
eminv.Boost(-self.nbvec.x(), -self.nbvec.y(), -self.nbvec.z())
emin_n = eminv.E()
print("emin_n, GeV:", emin_n)
#maximal delta in nucleus frame
dmax_n = 100.
if parse.has_option("main", "dmax_n"):
dmax_n = parse.getfloat("main", "dmax_n")
print("dmax_n:", dmax_n)
#cross section formula
self.eqpar = self.eq(self)
self.dSigDwDt = TF2("dSigDwDt", self.eqpar, emin_n, self.Ee_n, 0,
dmax_n)
self.dSigDwDt.SetNpx(2000)
self.dSigDwDt.SetNpy(2000)
gRandom.SetSeed(5572323)
#total integrated cross section over all delta (to 1e5)
dSigInt = TF2("dSigInt", self.eqpar, emin_n, self.Ee_n, 0, 1e5)
sigma_tot = dSigInt.Integral(emin_n, self.Ee_n, 0, 1e5)
print("Total cross section, mb:", sigma_tot)
#uniform generator for azimuthal angles
self.rand = TRandom3()
self.rand.SetSeed(5572323)
#tree output from the generator
tlist = ["true_phot_w", "true_phot_delta", "true_phot_theta_n"]
tlist += ["true_phot_theta", "true_phot_phi", "true_phot_E"]
tlist += ["true_el_theta", "true_el_phi", "true_el_E"]
self.tree_out = self.set_tree(tree, tlist)
print("Lifshitz_93p16 parametrization initialized")
