EvtPVVCPLH.cpp

Go to the documentation of this file.

 
/***********************************************************************
* Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
*                                                                      *
* This file is part of EvtGen.                                         *
*                                                                      *
* EvtGen is free software: you can redistribute it and/or modify       *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation, either version 3 of the License, or    *
* (at your option) any later version.                                  *
*                                                                      *
* EvtGen is distributed in the hope that it will be useful,            *
* but WITHOUT ANY WARRANTY; without even the implied warranty of       *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        *
* GNU General Public License for more details.                         *
*                                                                      *
* You should have received a copy of the GNU General Public License    *
* along with EvtGen.  If not, see <https://www.gnu.org/licenses/>.     *
***********************************************************************/
 
#include "EvtGenModels/EvtPVVCPLH.hh"
 
#include "EvtGenBase/EvtCPUtil.hh"
#include "EvtGenBase/EvtConst.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtId.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtRandom.hh"
#include "EvtGenBase/EvtReport.hh"
 
#include "EvtGenModels/EvtSVVHelAmp.hh"
 
#include <stdlib.h>
#include <string>
 
std::string EvtPVVCPLH::getName() const
{
    return "PVV_CPLH";
}
 
EvtDecayBase* EvtPVVCPLH::clone() const
{
    return new EvtPVVCPLH;
}
 
void EvtPVVCPLH::init()
{
    // check that there are 8 arguments (deltaMs no argument anymore)
    checkNArg( 8 );
    checkNDaug( 2 );
 
    checkSpinParent( EvtSpinType::SCALAR );
 
    checkSpinDaughter( 0, EvtSpinType::VECTOR );
    checkSpinDaughter( 1, EvtSpinType::VECTOR );
}
 
void EvtPVVCPLH::initProbMax()
{
    //This is probably not quite right, but it should do as a start...
    //Anders
 
    setProbMax( 2 * ( getArg( 2 ) * getArg( 2 ) + getArg( 4 ) * getArg( 4 ) +
                      getArg( 6 ) * getArg( 6 ) ) );
}
 
void EvtPVVCPLH::decay( EvtParticle* p )
{
    //added by Lange Jan4,2000
    static const EvtId BS0 = EvtPDL::getId( "B_s0" );
    static const EvtId BSB = EvtPDL::getId( "anti-B_s0" );
 
    //This is only to get tag-ID
    //Mixing is not relevant
    //Lifetime is made correctly later
    //Tristan
    EvtId other_b;
    double t;
 
    // To generate integrated CP asymmetry, EvtGen uses the "flipping".
    // CP-asymmetry in this channel very small, since:
    // deltaMs large ..and..
    // CPV-phase small
    EvtCPUtil::getInstance()->OtherB( p, t, other_b );
 
    //Here we're gonna generate and set the "envelope" lifetime
    //So we take the longest living component (for positive deltaGamma: tauH)
    //The double exponent will be taken care of later, by the amplitudes
    //Tristan
 
    static const double Gamma = EvtConst::c / ( EvtPDL::getctau( BS0 ) );
    static const double deltaGamma = EvtCPUtil::getInstance()->getDeltaGamma(
        BS0 );
    static const double ctauLong = EvtConst::c /
                                   ( Gamma - fabs( deltaGamma ) / 2 );
    // if dG>0: tauLong=tauH(CP-odd) is then largest
 
    //This overrules the lifetimes made in OtherB
    t = -log( EvtRandom::Flat() ) *
        ( ctauLong );    //ctauLong has same dimensions as t
    if ( isBsMixed( p ) ) {
        p->getParent()->setLifetime( t );
    } else {
        p->setLifetime( t );
    }
 
    //These should be filled with the transversity amplitudes at t=0 //Tristan
    EvtComplex G0P, G1P, G1M;
    G1P = EvtComplex( getArg( 2 ) * cos( getArg( 3 ) ),
                      getArg( 2 ) * sin( getArg( 3 ) ) );
    G0P = EvtComplex( getArg( 4 ) * cos( getArg( 5 ) ),
                      getArg( 4 ) * sin( getArg( 5 ) ) );
    G1M = EvtComplex( getArg( 6 ) * cos( getArg( 7 ) ),
                      getArg( 6 ) * sin( getArg( 7 ) ) );
 
    EvtComplex lambda_km =
        EvtComplex( cos( 2 * getArg( 0 ) ),
                    sin( 2 * getArg( 0 ) ) );    //was een min in oude versie
 
    //deltaMs is no argument anymore
    //Tristan
 
    static const double deltaMs = EvtCPUtil::getInstance()->getDeltaM( BS0 );
 
    EvtComplex cG0P, cG1P, cG1M;
 
    double mt = exp( -std::max( 0., deltaGamma ) * t / ( 2 * EvtConst::c ) );
    double pt = exp( +std::min( 0., deltaGamma ) * t / ( 2 * EvtConst::c ) );
 
    EvtComplex gplus =
        ( mt * EvtComplex( cos( deltaMs * t / ( 2 * EvtConst::c ) ),
                           sin( deltaMs * t / ( 2 * EvtConst::c ) ) ) +
          pt * EvtComplex( cos( deltaMs * t / ( 2 * EvtConst::c ) ),
                           sin( -deltaMs * t / ( 2 * EvtConst::c ) ) ) ) /
        2;
    EvtComplex gminus =
        ( mt * EvtComplex( cos( deltaMs * t / ( 2 * EvtConst::c ) ),
                           sin( deltaMs * t / ( 2 * EvtConst::c ) ) ) -
          pt * EvtComplex( cos( deltaMs * t / ( 2 * EvtConst::c ) ),
                           sin( -deltaMs * t / ( 2 * EvtConst::c ) ) ) ) /
        2;
    ;
 
    if ( other_b == BSB ) {
        //These are the right equations for the transversity formalism
        //cGOP is de 0-component, CP-even, so lives shorter: mainly lifetime tauL
        //cG1P is the //-component, also CP-even, also mainly smaller exponent
        //cG1M is the transverse component, CP-odd, so has mainly longer lifetime tauH
        //Tristan
        cG0P = G0P * ( gplus + lambda_km * gminus );
        cG1P = G1P * ( gplus + lambda_km * gminus );
        cG1M = G1M * ( gplus - lambda_km * gminus );
    } else if ( other_b == BS0 ) {
        //The equations for BsBar
        //Note the minus-sign difference
        //Tristan
        cG0P = G0P * ( gplus + ( 1.0 / lambda_km ) * gminus );
        cG1P = G1P * ( gplus + ( 1.0 / lambda_km ) * gminus );
        cG1M = -G1M * ( gplus - ( 1.0 / lambda_km ) * gminus );
 
    } else {
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "other_b was not BSB or BS0!" << std::endl;
        ::abort();
    }
 
    EvtComplex A0, AP, AM;
    //Converting the transversity amplitudes
    //to helicity amplitudes
    //(to plug them into SVVHelAmp)
    A0 = cG0P;
    AP = ( cG1P + cG1M ) / sqrt( 2.0 );
    AM = ( cG1P - cG1M ) / sqrt( 2.0 );
 
    EvtSVVHelAmp::SVVHel( p, m_amp2, getDaug( 0 ), getDaug( 1 ), AP, A0, AM );
 
    return;
}
 
bool EvtPVVCPLH::isBsMixed( EvtParticle* p )
{
    if ( !( p->getParent() ) )
        return false;
 
    static const EvtId BS0 = EvtPDL::getId( "B_s0" );
    static const EvtId BSB = EvtPDL::getId( "anti-B_s0" );
 
    if ( ( p->getId() != BS0 ) && ( p->getId() != BSB ) )
        return false;
 
    if ( ( p->getParent()->getId() == BS0 ) || ( p->getParent()->getId() == BSB ) )
        return true;
 
    return false;
}