Gabriele Cosmo
81 lines
3.3 KiB
C++
81 lines
3.3 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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//
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// This is the right-hand side for equation of motion for a
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// massive particle in a gravitational field.
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//
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// History:
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// - 14.06.11 P.Gumplinger, Created.
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// -------------------------------------------------------------------
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// Adopted from G4EqMagElectricField.hh
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//
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// Thanks to Peter Fierlinger (PSI) and
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// A. Capra and A. Fontana (INFN Pavia)
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// -------------------------------------------------------------------
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#include "G4EqGravityField.hh"
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#include "globals.hh"
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void
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G4EqGravityField::SetChargeMomentumMass(G4double,
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G4double,
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G4double particleMass )
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{
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fMass = particleMass;
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}
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void
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G4EqGravityField::EvaluateRhsGivenB(const G4double y[],
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const G4double G[],
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G4double dydx[] ) const
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{
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// Components of y:
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// 0-2 dr/ds,
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// 3-5 dp/ds - momentum derivatives
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G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
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G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
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G4double Energy = std::sqrt(momentum_mag_square + fMass*fMass);
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G4double cof2 = Energy/c_light;
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G4double cof1 = inv_momentum_magnitude*fMass;
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G4double inverse_velocity = Energy*inv_momentum_magnitude/c_light;
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dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
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dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
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dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
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dydx[3] = G[0]*cof1*cof2;
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dydx[4] = G[1]*cof1*cof2; // m*g
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dydx[5] = G[2]*cof1*cof2;
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// Lab Time of flight
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dydx[7] = inverse_velocity;
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return;
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}
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