EvtPHSPBMix Class Reference

The class provides routine to decay vector-> particle particle with B0 mixing, handles states with only one neutral B. More...

#include <EvtPHSPBMix.h>

Inheritance diagram for EvtPHSPBMix:

Collaboration diagram for EvtPHSPBMix:

Public Member Functions
	EvtPHSPBMix ()
	Default constructor.
virtual	~EvtPHSPBMix ()
	Default destructor.
std::string	getName ()
	Get function Name
EvtDecayBase *	clone ()
	Clone the decay
void	decay (EvtParticle *p)
	Decay function.
void	init ()
	Init function.
void	initProbMax ()
	Init maximal prob.
int	nRealDaughters ()
	Number of real daughters.

Private Attributes
double	_freq {0}
	mixing frequency in hbar/mm
bool	_print_info {false}
	Print evtgeninfo?

Detailed Description

The class provides routine to decay vector-> particle particle with B0 mixing, handles states with only one neutral B.

Definition at line 88 of file EvtPHSPBMix.h.

Constructor & Destructor Documentation

EvtPHSPBMix()

EvtPHSPBMix ( )

inline

Default constructor.

Definition at line 93 of file EvtPHSPBMix.h.

{}

~EvtPHSPBMix()

~EvtPHSPBMix ( )

virtual

Default destructor.

Definition at line 365 of file EvtPHSPBMix.cc.

{}

Member Function Documentation

clone()

EvtDecayBase * clone

(

)

Clone the decay

Definition at line 373 of file EvtPHSPBMix.cc.

{
  return new EvtPHSPBMix;
}

decay()

void decay

(

EvtParticle *

p

)

Decay function.

Definition at line 456 of file EvtPHSPBMix.cc.

{
 
  // generate a final state according to phase space
 
  //  const bool BBpipi(getNDaug()!=4);//true if BBpipi, if not BBpi
  if (_print_info)    std::cout << "decay B_MIX (0)" << std::endl;
  std::vector<EvtId> tempDaug(getNDaug() - 1);
  tempDaug[0] = getDaug(0);
  tempDaug[1] = getDaug(1);
  tempDaug[2] = getDaug(2);
  if (getNDaug() == 5)
    tempDaug[3] = getDaug(3);
 
  if (_print_info)    std::cout << "decay B_MIX (1)" << std::endl;
 
 
  p->initializePhaseSpace(getNDaug() - 1, tempDaug.data());
 
  EvtParticle* s1;
 
  s1 = p->getDaug(0);
 
  //delete any daughters - if there are daughters, they
  //are from the initialization and will be redone later
  if (s1->getNDaug() > 0) { s1->deleteDaughters();}
 
  EvtVector4R p1 = s1->getP4();
 
  // throw 1 random numbers to decide whether B1 is B0 or B0B
  const bool changed_flavor(EvtRandom::random() > 0.5); //Daug(0) becomes Daug(1)
  if (_print_info)    std::cout << "decay B_MIX (3)" << std::endl;
  s1->init(changed_flavor ? getDaug(getNDaug() - 1) : getDaug(0), p1);
 
  // choose a decay time for each final state particle using the
  // lifetime (which must be the same for both particles) in pdt.table
  // and calculate the lifetime difference for this event
  s1->setLifetime();
  if (_print_info)      std::cout << "decay B_MIX (4)" << std::endl;
  const double t1(s1->getLifetime());
 
  // calculate the oscillation amplitude, based on whether this event is mixed or not
  EvtComplex osc_amp(changed_flavor ? EvtComplex(0,
                                                 -sin(_freq * t1 / 2.)) : EvtComplex(cos(_freq * t1 / 2.))); //Amplitude return <B0(B)|B1>
  if (_print_info)    std::cout << "decay B_MIX (5)" << std::endl;
  // store the amplitudes for each parent spin basis state
  double norm = 1.0 / p1.d3mag();
  if (_print_info)    std::cout << "decay B_MIX (6)" << std::endl;
  vertex(0, norm * osc_amp * p1 * (p->eps(0)));
  vertex(1, norm * osc_amp * p1 * (p->eps(1)));
  vertex(2, norm * osc_amp * p1 * (p->eps(2)));
  if (_print_info)  std::cout << "decay B_MIX (7)" << std::endl;
  return ;
}

getName()

std::string getName

(

)

Get function Name

Definition at line 367 of file EvtPHSPBMix.cc.

{
  return "PHSP_B_MIX";
}

init()

void init

(

)

Init function.

Definition at line 378 of file EvtPHSPBMix.cc.

{
  // check that there we are provided exactly one parameter
  //One arg: Delta m
  const unsigned short int narg(1);
  if (getNArg() != narg) {
    EvtGenReport(EVTGEN_ERROR, "EvtGen") << "EvtPHSPBMix generator expected "
                                         << " " << narg
                                         << " argument(s) (delta m) but found:"
                                         << getNArg() << endl;
    EvtGenReport(EVTGEN_ERROR, "EvtGen") << "Will terminate execution!" << endl;
    ::abort();
  }
 
 
  //report(DEBUG,"EvtGen") << "EvtPHSPBMIX::init point (2)"<<std::endl;
  //usage: mixing P0 P- pi+    : 4 arg. -> P0  P- pi+       P0b    PHSP_B_MIX dm;
  //     : mixing P0 P- pi+ pi : 5 arg. -> P0  P- pi+  pi0  P0b    PHSP_B_MIX dm;
 
 
  checkNDaug(4, 5);
  // report(DEBUG,"EvtGen") << "EvtPHSPBMIX::init point (3)"<<std::endl;
 
  bool BBpipi(getNDaug() == 5);
 
  if (!(EvtPDL::chargeConj(getDaug(0)) == getDaug(getNDaug() - 1))) {
    EvtGenReport(EVTGEN_ERROR, "EvtGen") << "EvtPHSPBMix generator expected two first particles "
                                         << "to be charge conjugate." << endl
                                         << "  Found " << EvtPDL::name(getDaug(0)).c_str()
                                         << "," << EvtPDL::name(getDaug(getNDaug() - 1)).c_str() << endl;
    EvtGenReport(EVTGEN_ERROR, "EvtGen") << "Will terminate execution!" << endl;
    ::abort();
  }
  //parameters for mixing of particle1
 
  _freq = getArg(0) / EvtConst::c;
 
  //double gamma= 1/EvtPDL::getctau(getDaug(0));  // gamma/c (1/mm)
 
  double tau = 1e12 * EvtPDL::getctau(getDaug(0)) / EvtConst::c; // in ps
  double dm = 1e-12 * getArg(0); // B0/anti-B0 mass difference in hbar/ps
  double x = dm * tau;
 
  std::ostringstream sss;
  sss << "    " << EvtPDL::name(getParentId()).c_str() << " --> "
      << EvtPDL::name(getDaug(0)).c_str() << " + "
      << EvtPDL::name(getDaug(1)).c_str();
  sss << " + " << EvtPDL::name(getDaug(2)).c_str();
  if (BBpipi)
    sss << " + " << EvtPDL::name(getDaug(3)).c_str();
 
  EvtGenReport(EVTGEN_INFO, "EvtGen") << "PHSP_B_MIX will generate mixing :"
                                      << endl << endl
                                      << sss.str() << endl << endl
                                      << "using parameters:" << endl << endl
                                      << "  delta(m)  = " << dm << " hbar/ps" << endl
                                      << "  _freq     = " << _freq << " hbar/mm" << endl
                                      << "  dgog      = "  << 0 << endl
                                      << "  dGamma    = "  << 0 << " hbar/mm" << endl
                                      << "  q/p       = " << 1 << endl
                                      << "  tau       = " << tau << " ps" << endl
                                      << "  x         = " << x << endl
                                      << endl;
 
}

initProbMax()

void initProbMax

(

)

Init maximal prob.

function

Definition at line 449 of file EvtPHSPBMix.cc.

{
  // this value is ok for reasonable values of all the parameters
  setProbMax(4.0);
  //noProbMax();
}

nRealDaughters()

int nRealDaughters

(

)

Number of real daughters.

Definition at line 444 of file EvtPHSPBMix.cc.

{
  return getNDaug() - 1;
}

Member Data Documentation

_freq

double _freq {0}

private

mixing frequency in hbar/mm

Definition at line 119 of file EvtPHSPBMix.h.

_print_info

bool _print_info {false}

private

Print evtgeninfo?

Definition at line 122 of file EvtPHSPBMix.h.

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The documentation for this class was generated from the following files:

• generators/evtgen/models/include/EvtPHSPBMix.h
• generators/evtgen/models/src/EvtPHSPBMix.cc