started to implement class for photomeson production [ci skip]

agnpy/photo_meson/photo_meson.py

@@ -0,0 +1,52 @@
+# class for photomeson production
+import numpy as np
+from .kernels import PhiKernel
+from ..utils.math import axes_reshaper
+from ..utils.conversion import mpc2
+
+
+class PhotoMesonProduction:
+    def __init__(self, blob, target, integrator=np.trapz):
+        self.blob = blob
+        # check that this blob has a proton distribution
+        if self.blob._n_p is None:
+            raise AttributeError(
+                "There is no proton distribution in this emission region"
+            )
+        self.target = target
+        self.integrator = integrator
+        self.phi_kernel_gamma = PhiKernel("gamma")
+        self.phi_kernel_electron = PhiKernel("electron")
+        self.phi_kernel_positron = PhiKernel("positron")
+        self.phi_kernel_electron_neutrino = PhiKernel("electron_neutrino")
+        self.phi_kernel_electron_antineutrino = PhiKernel("electron_antineutrino")
+        self.phi_kernel_muon_neutrino = PhiKernel("muon_neutrino")
+        self.phi_kernel_moun_antineutrino = PhiKernel("muon_antineutrino")
+
+    def H(self, eta, E, phi_kernel):
+        """Compute the H function in Eq. (70) [KelnerAharonian2008]_.
+
+        Parameters
+        ----------
+        eta : float
+            kinematic variable (:math:`eta = 4 \epsilon \gamma_{\rm p}`)
+        E : float
+            energy of the secondary
+        phi_kernel : `~agnpy.photo_meson.PhiKernel`
+            kernel to be used for the integration (depends on the particle)
+        """
+        # we want this output to be a two-dimensional function, so let us reshape it
+        _gamma_p, _eta, _E = axes_reshaper(self.blob.gamma_p, eta, E)
+        _x = (_E / (_gamma_p * mpc2)).to_value("")
+        # obtain the energy of the target from eta
+        _E_ph = _eta * mpc2 / (4 * _gamma_p)
+        _H_integrand = (
+            mpc2
+            / 4
+            * self.blob.n_p(_gamma_p)
+            * self.target.n_ph(_E_ph)
+            * phi_kernel(_eta, _x)
+        )
+        import IPython
+
+        IPython.embed()