Merge pull request #2539 from heppye/CMSSW_5_3_X

Create LambdaB_Psi2SLambda_ppi.dec

GeneratorInterface/ExternalDecays/data/LambdaB_Psi2SLambda_ppi.dec

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+# This is the decay file for the polarized decay Lambda_B0 -> Psi(2S)(MU+ MU-) Lambda0
+#
+# Descriptor: [Lambda_B0 -> Psi(2S)(mu+ mu-) Lambda0]cc
+#
+# NickName:
+#
+# Physics: Generates the correct angular distributions for polarized Lambda_b0 decay
+#
+# Tested: Yes
+# By: B. Drell
+# Date: 1-25-11
+#
+#
+# The helicity amplitudes are H[lambda1, lambda2] where lambda1 is the
+# Lambda0 helicity and lambda2 is the J/Psi helicity:
+# aPlus = H[1/2, 0]
+# aMinus = H[-1/2, 0]
+# bPlus = H[-1/2, -1]
+# bMinus = H[1/2, 1]
+#
+# The correct ordering for HELAMP is highest helicity to lowest, first particle
+# first. So the correct order is:
+# bMinus betaMinus aPlus alphaPlus aMinus alphaMinus bPlus betaPlus
+#
+# These numerical values come from the ATLAS paper.
+# Calculated using PQCD general amplitude coefficients.
+# I need to verify that these are correct.
+Define aPlus 0.423266
+Define alphaPlus -1.61239
+Define aMinus 0.257533
+Define alphaMinus 1.22743
+Define bPlus 0.295037
+Define betaPlus -1.84891
+Define bMinus 0.812939
+Define betaMinus 1.53438
+#
+#Helicity amplitudes for Lambda0 decay (from Lambda0 asymmetry
+#parameter alpha_Lam)
+#alpha_Lam = 0.642 +- 0.013 = |hPlus|^2 - |hMinus|^2
+Define hPlus 0.906
+Define hMinus 0.423
+#
+Alias MyLambda_b0 Lambda_b0
+Alias Myanti-Lambda_b0 anti-Lambda_b0
+ChargeConj MyLambda_b0 Myanti-Lambda_b0
+Alias MyLambda0 Lambda0
+Alias Myanti-Lambda0 anti-Lambda0
+ChargeConj MyLambda0 Myanti-Lambda0
+Alias MyPsi psi(2S)
+ChargeConj MyPsi MyPsi
+#
+Decay MyLambda_b0
+1.0 MyLambda0 MyPsi HELAMP bMinus betaMinus aPlus alphaPlus aMinus alphaMinus bPlus betaPlus;
+Enddecay
+#
+Decay Myanti-Lambda_b0
+#1.0 Myanti-Lambda0 MyPsi HELAMP bPlus betaPlus aMinus alphaMinus aPlus alphaPlus bMinus betaMinus;
+1.0 Myanti-Lambda0 MyPsi HELAMP bMinus betaMinus aPlus alphaPlus aMinus alphaMinus bPlus betaPlus;
+Enddecay
+#
+Decay MyLambda0
+1.0 p+ pi- HELAMP hPlus 0 hMinus 0;
+Enddecay
+#
+Decay Myanti-Lambda0
+1.0 anti-p- pi+ HELAMP hMinus 0 hPlus 0;
+Enddecay
+#
+Decay MyPsi
+1.0 mu+ mu- PHOTOS VLL;
+Enddecay
+#
+End