add example of creating simulation for midshower dimuon

Biasing/python/eat.py

@@ -82,6 +82,69 @@ def midshower_nuclear( detector , bias_factor , bias_threshold , min_nuclear_ene
 
     return sim
 
+
+def midshower_dimuon( detector , bias_factor , bias_threshold , min_nuclear_energy ) :
+    """Example configuration for producing mid-shower dimuon interactions in
+    the ECal that fake a missing energy (ME) signal.
+       
+    In this particular example, 4 GeV electrons are fired upstream of the 
+    tagger tracker. Then simulation events are then put through a series of
+    filters.
+
+    Parameters
+    ----------
+
+    detector : str
+        Name of the detector
+    bias_factor : float
+        Factor to multiply GammaToMuPair xsec by within the ECal
+    bias_threshold : float
+        Minium energy [MeV] to bias a photon
+    min_nuclear_energy : float
+        Minium total energy [MeV] that went to muons to keep event
+
+    Returns
+    -------
+    simulator :
+        configured for mid-shower dimuon interactions and far-upstream generator
+
+    Example
+    -------
+
+        from LDMX.Biasing import eat
+        eat_pn_sim = eat.midshower_nuclear('ldmx-det-v12',1000.,1700.)
+
+    """
+
+    #Instantiate the simulator. 
+    sim = simulator.simulator("eat-midshower-dimuon")
+    from LDMX.Ecal import EcalGeometry
+
+    #Set the path to the detector to use.
+    #the second parameter says we want to include scoring planes
+    sim.setDetector( detector , True )
+
+    #Set run parameters
+    sim.description = "Biased Mid-Shower DiMuon Interactions ME Background"
+    sim.beamSpotSmear = [20., 80., 0.] #mm
+
+    from LDMX.SimCore import generators
+    sim.generators = [ generators.single_4gev_e_upstream_tagger() ]
+
+    #Enable and configure the biasing
+    from LDMX.SimCore import bias_operators
+    sim.biasing_operators = [ bias_operators.GammaToMuPair('ecal', bias_factor, bias_threshold) ]
+
+    #Configure the sequence in which user actions should be called.
+    sim.actions = [
+            filters.PrimaryToEcalFilter(3500.),
+            util.PartialEnergySorter(bias_threshold),
+            filters.MidShowerDiMuonBkgdFilter(min_nuclear_energy),
+    ]
+
+    return sim
+
+
 def dark_brem( ap_mass , lhe, detector ) :
     """Example configuration for producing dark brem interactions in the ECal.