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khahn |
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#include "Angles.h"
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#include <iostream>
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//
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// angles from Gainer, et. al.
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// arVix:1108.2274v1 [hep-ph], 10 Aug 2011
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//
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// NB : phi1 will look quite different from the plots on pg 14, which have no kinematic cuts. phi1 looks
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// more like the plots on pg 22, which do have cuts.
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void getAngles_ANL_NWU( LabVectors &l, Angles &a ) {
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//
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// define the frames & coordinate systems
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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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// "partons" (pg6)
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TLorentzVector kq( 0, 0, (l.vec4l.E()+l.vec4l.Pz())/2, (l.vec4l.E()+l.vec4l.Pz())/2 );
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TLorentzVector kqbar( 0, 0, (l.vec4l.Pz()-l.vec4l.E())/2, (l.vec4l.E()-l.vec4l.Pz())/2 );
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TLorentzVector veckq_in_Xframe(kq);
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TLorentzVector veckqbar_in_Xframe(kqbar);
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veckq_in_Xframe.Boost(-1*Xframe);
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veckqbar_in_Xframe.Boost(-1*Xframe);
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// Z vectors
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TLorentzVector vecz1_in_Xframe (l.vecz1);
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TLorentzVector vecz2_in_Xframe (l.vecz2);
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TLorentzVector vecz1_in_Z1frame (l.vecz1);
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TLorentzVector vecz2_in_Z2frame (l.vecz2);
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vecz1_in_Xframe.Boost(-1*Xframe);
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vecz2_in_Xframe.Boost(-1*Xframe);
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vecz1_in_Z1frame.Boost(-1*Z1frame);
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vecz2_in_Z2frame.Boost(-1*Z2frame);
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// coord system in the CM frame
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TVector3 uz_in_Xframe = vecz1_in_Xframe.Vect().Unit();
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TVector3 uy_in_Xframe = (veckq_in_Xframe.Vect().Unit().Cross(uz_in_Xframe.Unit())).Unit();
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TVector3 ux_in_Xframe = (uy_in_Xframe.Unit().Cross(uz_in_Xframe.Unit())).Unit();
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TRotation rotation;
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rotation = rotation.RotateAxes( ux_in_Xframe,uy_in_Xframe,uz_in_Xframe ).Inverse();
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// coords for Z2. rotate CM around y by pi
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TVector3 ux_in_Xframe_z2(ux_in_Xframe);
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TVector3 uy_in_Xframe_z2(uy_in_Xframe);
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TVector3 uz_in_Xframe_z2(uz_in_Xframe);
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TRotation aroundy;
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aroundy.Rotate(TMath::Pi(),uy_in_Xframe_z2);
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ux_in_Xframe_z2.Transform(aroundy);
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uz_in_Xframe_z2.Transform(aroundy);
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TRotation rotation2;
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rotation2 = rotation2.RotateAxes( ux_in_Xframe_z2,uy_in_Xframe_z2,uz_in_Xframe_z2 ).Inverse();
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//
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// for going to the Z frames from the CM frame
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//
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TLorentzVector vecz1_in_Xframe_newcoords(vecz1_in_Xframe);
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vecz1_in_Xframe_newcoords.Transform(rotation);
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TVector3 Z1frame_from_Xframe_newcoords = vecz1_in_Xframe_newcoords.BoostVector();
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TLorentzVector vecz2_in_Xframe_newcoords(vecz2_in_Xframe);
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vecz2_in_Xframe_newcoords.Transform(rotation2);
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TVector3 Z2frame_from_Xframe_newcoords = vecz2_in_Xframe_newcoords.BoostVector();
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//
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// theta(l1m), phi(l1m) in Z1 frame
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// --------------------------------------------------------------------------------------------------
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TLorentzVector vecl1m_in_Z1frame(l.vecl1m);
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// redefine coords
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vecl1m_in_Z1frame.Boost(-1*Xframe);
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vecl1m_in_Z1frame.Transform(rotation);
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// then boost to Z1
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vecl1m_in_Z1frame.Boost(-1*Z1frame_from_Xframe_newcoords);
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// now get angles
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a.costheta1 = vecl1m_in_Z1frame.CosTheta();
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a.phi1 = vecl1m_in_Z1frame.Phi();
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//
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// theta(l2m), phi(l2m) in Z2 frame
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// --------------------------------------------------------------------------------------------------
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TLorentzVector vecl2m_in_Z2frame(l.vecl2m);
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// redefine coords
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vecl2m_in_Z2frame.Boost(-1*Xframe);
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vecl2m_in_Z2frame.Transform(rotation2);
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// then boost to Z
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vecl2m_in_Z2frame.Boost(-1*Z2frame_from_Xframe_newcoords);
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// now get angles
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a.costheta2 = vecl2m_in_Z2frame.CosTheta();
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a.phi2 = vecl2m_in_Z2frame.Phi();
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a.Phi = TVector2::Phi_0_2pi(TMath::Pi()
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-TVector2::Phi_0_2pi(a.phi1)
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-TVector2::Phi_0_2pi(a.phi2) );
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//
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// Theta(Z1,pp) in X frame
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// --------------------------------------------------------------------------------------------------
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// but store it under Phi1 ...
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// redefine coords
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veckq_in_Xframe.Transform(rotation);
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// already boosted ....
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a.Phi1 = veckq_in_Xframe.Theta();
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//
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// why not ... let's add some masses
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// --------------------------------------------------------------------------------------------------
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khahn |
1.2 |
// 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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khahn |
1.1 |
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};
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