Add nu Q2 x plots for simulation

Add nu Q2 x plots for simulation Will re-write jpsi kinematics in a simplified way (like nu Q2 x) Will re-write the plotting part to factorize out code

dvmp/analysis/util.h

@@ -156,6 +156,43 @@ get_y(const std::pair<ROOT::Math::PxPyPzMVector, ROOT::Math::PxPyPzMVector>&
   return 0.5*log((energy_pair + pz_pair)/(energy_pair - pz_pair));
 }
 
+//========================================================================================================
+//for structure functions
+
+struct inv_quant{    //add more when needed
+    double nu, Q2, x;
+};
+
+//for simu
+inline inv_quant calc_inv_quant_simu(const std::vector<ROOT::Math::PxPyPzMVector>& parts){
+  ROOT::Math::PxPyPzMVector q(parts[0] - parts[2]);
+  ROOT::Math::PxPyPzMVector P(parts[3]);
+  
+  double nu = q.Dot(P) / P.mass();
+  double Q2 = - q.Dot(q);  
+  inv_quant quantities = {nu, Q2, Q2/2./P.mass()/nu};
+  return quantities;
+}
+
+inline double get_nu_simu(inv_quant quantities) {
+  return quantities.nu/1000.;
+}
+inline double get_Q2_simu(inv_quant quantities) {
+  return quantities.Q2;
+}
+inline double get_x_simu(inv_quant quantities) {
+  return quantities.x;
+}
+
+//for tracking, add later
+
+//=========================================================================================================
+
+
+
+
+
+
 } // namespace util
 
 #endif