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khahn |
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#include "Angles.h"
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#include <iostream>
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void getAngles( LabVectors &l,
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Angles &a ) {
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//
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// define the frames
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// --------------------------------------------------------------------------------------------------
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TVector3 Xframe = l.vec4l.BoostVector();
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TVector3 Z1frame = l.vecz1.BoostVector();
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TVector3 Z2frame = l.vecz2.BoostVector();
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//
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// costheta(l1m,X) in Z1 frame
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// --------------------------------------------------------------------------------------------------
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TLorentzVector vecl1m_in_Z1frame( l.vecl1m ); // make a copies of the vectors
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TLorentzVector vec4l_in_Z1frame( l.vec4l ); //
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vecl1m_in_Z1frame.Boost( -1*Z1frame ); // now go to the Z1 rest frame
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vec4l_in_Z1frame.Boost( -1*Z1frame ); //
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a.costheta1
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= vecl1m_in_Z1frame.Vect().Dot(-1*vec4l_in_Z1frame.Vect()) /
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(vecl1m_in_Z1frame.Vect().Mag()*vec4l_in_Z1frame.Vect().Mag());
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//
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// costheta(l3,X) in Z2 frame
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// --------------------------------------------------------------------------------------------------
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TLorentzVector vecl2m_in_Z2frame( l.vecl2m ); // make copies of the vectors
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TLorentzVector vec4l_in_Z2frame( l.vec4l ); //
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vecl2m_in_Z2frame.Boost( -1*Z2frame ); // now go to the Z2 rest frame
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vec4l_in_Z2frame.Boost( -1*Z2frame );
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a.costheta2 =
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vecl2m_in_Z2frame.Vect().Dot(-1*vec4l_in_Z2frame.Vect()) /
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(vecl2m_in_Z2frame.Vect().Mag()*vec4l_in_Z2frame.Vect().Mag());
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//
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// Phi(Z1,Z2) in X frame
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// --------------------------------------------------------------------------------------------------
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// this is essentially what they do and it reproduces their numbers,
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// it's the angle between l1 and the z2 decay plane in the Z1 frame
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TLorentzVector vecz2_in_Z1frame( l.vecz2 ); //
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TLorentzVector vecl2m_in_Z1frame( l.vecl2m ); //
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TLorentzVector vecl2p_in_Z1frame( l.vecl2p ); //
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vecz2_in_Z1frame.Boost( -1*Z1frame ); //
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vecl2m_in_Z1frame.Boost( -1*Z1frame ); //
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vecl2p_in_Z1frame.Boost( -1*Z1frame ); //
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//
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// define the Z2 coordinate system in the Z1 frame
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// x : opposite the Z2 dir, lies in the Z2 decay plane
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// z : orthogonal to the Z2 decay plane
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// y : orthogonal to x&z, lies in the Z2 decay plane
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TVector3 nnewX = ( -1*vecz2_in_Z1frame.Vect()).Unit();
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TVector3 nnewZ = (vecl2m_in_Z1frame.Vect().Cross(vecl2p_in_Z1frame.Vect())).Unit();
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TVector3 nnewY = nnewZ.Cross(nnewX).Unit();
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TRotation rotation2;
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rotation2 = (rotation2.RotateAxes( nnewX, nnewY, nnewZ )).Inverse();
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TVector3 vecl1m_in_Z2coords_Z1frame = vecl1m_in_Z1frame.Vect().Transform(rotation2);
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//
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// axes are redfined so that Phi is the angle between the Z1 orthogonal
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// and the Z2 decay plane as given by y
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//
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TRotation rotation3;
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TVector3 nnnewX( 0,1,0 );
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TVector3 nnnewY( 0,0,1 );
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TVector3 nnnewZ( 1,0,0 );
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rotation3 = (rotation3.RotateAxes( nnnewX, nnnewY, nnnewZ )).Inverse();
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TVector3 vecl1m_in_Z2coords_redefined_Z1frame = vecl1m_in_Z2coords_Z1frame.Transform(rotation3);
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a.Phi = vecl1m_in_Z2coords_redefined_Z1frame.Phi();
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//
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// rather, I'd expect something like this ...
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//
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TLorentzVector vecl1p_in_Xframe( l.vecl1p ); // make a copies of the vectors
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TLorentzVector vecl1m_in_Xframe( l.vecl1m ); //
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TLorentzVector vecl2p_in_Xframe( l.vecl2p ); //
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TLorentzVector vecl2m_in_Xframe( l.vecl2m ); //
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vecl1p_in_Xframe.Boost( -1*Xframe ); // go to the X rest frame
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vecl1m_in_Xframe.Boost( -1*Xframe ); //
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vecl2p_in_Xframe.Boost( -1*Xframe ); //
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vecl2m_in_Xframe.Boost( -1*Xframe ); //
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/*
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// sanity check ...
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TLorentzVector z1inX = vecl1p_in_Xframe+vecl1m_in_Xframe;
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TLorentzVector z2inX = vecl2p_in_Xframe+vecl2m_in_Xframe;
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float dotz1z2 = z1inX.Vect().Dot(z2inX.Vect()) / (z1inX.Vect().Mag()*z2inX.Vect().Mag());
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std::cout << "dotz1z2: " << dotz1z2 << std::endl;
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*/
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TVector3 Z1ortho_in_Xframe = // define the decay planes via the orthogonals
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vecl1m_in_Xframe.Vect().Cross(vecl1p_in_Xframe.Vect());
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TVector3 Z2ortho_in_Xframe =
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vecl2m_in_Xframe.Vect().Cross(vecl2p_in_Xframe.Vect());
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/*
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// sanity check ... why are these small but not exactly zero ???
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float z1odot = Z1ortho_in_Xframe.Dot(z1inX.Vect())/(Z1ortho_in_Xframe.Mag()*z1inX.Vect().Mag());
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float z2odot = Z2ortho_in_Xframe.Dot(z2inX.Vect())/(Z2ortho_in_Xframe.Mag()*z2inX.Vect().Mag());
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float l1podot = Z1ortho_in_Xframe.Dot(vecl1p_in_Xframe.Vect())/(Z1ortho_in_Xframe.Mag()*vecl1p_in_Xframe.Vect().Mag());
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float l1modot = Z1ortho_in_Xframe.Dot(vecl1m_in_Xframe.Vect())/(Z1ortho_in_Xframe.Mag()*vecl1m_in_Xframe.Vect().Mag());
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std::cout << "Z1ortho_in_Xframe.Dot(z1inX): " << z1odot << "\t"
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<< "Z2ortho_in_Xframe.Dot(z2inX): " << z2odot << "\t"
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<< "Z1ortho_in_Xframe.Dot(veclp1_in_Xframe) : " << l1podot << "\t"
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<< "Z1ortho_in_Xframe.Dot(veclm1_in_Xframe) : " << l1modot << "\t"
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<< std::endl;
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*/
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// a.Phi = Z1ortho_in_Xframe.DeltaPhi(Z2ortho_in_Xframe);
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//a.Phi = Z1ortho_in_Xframe.Angle(Z2ortho_in_Xframe);
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//
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// costheta*(Z1,pp) in X frame
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// --------------------------------------------------------------------------------------------------
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TLorentzVector vecz1_in_Xframe( l.vecz1 ); // make a copies of the vectors
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TLorentzVector vecpp_in_Xframe( 0., 0., 1., 0. ); // define pp axis
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vecz1_in_Xframe.Boost( -1*Xframe ); // go to the X rest frame
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vecpp_in_Xframe.Boost( -1*Xframe ); //
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a.costhetastar =
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vecz1_in_Xframe.Vect().Dot(vecpp_in_Xframe.Vect()) /
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(vecz1_in_Xframe.Vect().Mag()*vecpp_in_Xframe.Vect().Mag());
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//
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// Phi1(Z1,pp) in X frame
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// --------------------------------------------------------------------------------------------------
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// define the Z1 decay plane in the Xframe
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// y: orthogonal to the Z1 decay plane
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// x: lies in the Z1 decay plane, but orthogonal to Z1
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// z: z1 in Xframe
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TVector3 newY = (vecl1p_in_Xframe.Vect().Unit().Cross(vecl1m_in_Xframe.Vect().Unit())).Unit();
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TVector3 newX = (newY.Cross(vecz1_in_Xframe.Vect().Unit())).Unit();
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TVector3 newZ( (vecz1_in_Xframe.Vect()).Unit() );
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TRotation rotation;
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rotation = (rotation.RotateAxes( newX, newY, newZ )).Inverse();
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TVector3 vecpp( 0., 0., 1. );
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TVector3 vecpp_in_Z1coords_Xframe = vecpp.Transform(rotation);
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a.Phi1 = vecpp_in_Z1coords_Xframe.Phi();
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a.mz1 = (l.vecl1m+l.vecl1p).M();
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a.mz2 = (l.vecl2m+l.vecl2p).M();
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a.m4l = (l.vec4l).M();
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};
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