Merge pull request #10008 from ferencek/DegridifiedUnpackedPhi_from-C…

…MSSW_7_4_4 Degridifying unpacked phi to break degeneracies in angular separations for packed candidates: 74X
cms-sw · Aug 1, 2015 · aabe8e3 · aabe8e3
2 parents 234ff7f + 2c753b3
commit aabe8e3
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Showing 2 changed files with 10 additions and 3 deletions.
diff --git a/DataFormats/PatCandidates/src/PackedCandidate.cc b/DataFormats/PatCandidates/src/PackedCandidate.cc
@@ -61,9 +61,13 @@ void pat::PackedCandidate::packVtx(bool unpackAfterwards) {
 }
 
 void pat::PackedCandidate::unpack() const {
-    p4_ = PolarLorentzVector(MiniFloatConverter::float16to32(packedPt_),
+    float pt = MiniFloatConverter::float16to32(packedPt_);
+    double shift = (pt<1. ? 0.1*pt : 0.1/pt); // shift particle phi to break degeneracies in angular separations
+    double sign = ( ( int(pt*10) % 2 == 0 ) ? 1 : -1 ); // introduce a pseudo-random sign of the shift
+    double phi = int16_t(packedPhi_)*3.2f/std::numeric_limits<int16_t>::max() + sign*shift*3.2/std::numeric_limits<int16_t>::max();
+    p4_ = PolarLorentzVector(pt,
                              int16_t(packedEta_)*6.0f/std::numeric_limits<int16_t>::max(),
-                             int16_t(packedPhi_)*3.2f/std::numeric_limits<int16_t>::max(),
+                             phi,
                              MiniFloatConverter::float16to32(packedM_));
     p4c_ = p4_;
     unpacked_ = true;

diff --git a/DataFormats/PatCandidates/src/PackedGenParticle.cc b/DataFormats/PatCandidates/src/PackedGenParticle.cc
@@ -19,7 +19,10 @@ void pat::PackedGenParticle::unpack() const {
     float m=MiniFloatConverter::float16to32(packedM_);
     float pz = std::tanh(y)*std::sqrt((m*m+pt*pt)/(1.-std::tanh(y)*std::tanh(y)));
     float eta = std::asinh(pz/pt);
-    p4_ = PolarLorentzVector(pt,eta,int16_t(packedPhi_)*3.2f/std::numeric_limits<int16_t>::max(),m);
+    double shift = (pt<1. ? 0.1*pt : 0.1/pt); // shift particle phi to break degeneracies in angular separations
+    double sign = ( ( int(pt*10) % 2 == 0 ) ? 1 : -1 ); // introduce a pseudo-random sign of the shift
+    double phi = int16_t(packedPhi_)*3.2f/std::numeric_limits<int16_t>::max() + sign*shift*3.2/std::numeric_limits<int16_t>::max();
+    p4_ = PolarLorentzVector(pt,eta,phi,m);
     p4c_ = p4_;
     unpacked_ = true;
 }