EDepInGas Class Reference

The Class for Energy deposit in the gas. More...

#include <EDepInGas.h>

Collaboration diagram for EDepInGas:

Public Member Functions
virtual	~EDepInGas ()
	Destructor.
void	initialize ()
	Initialize theclass.
double	getEDepInGas (int mode, int pdg, double p, double dx, double e3) const
	Return the energy deosite in the gas. More...
double	getMostProbabEDep (double p, double mass, double zi, double dx, double z, double a, double i, double rho) const
	Return the energy deosite in the material. More...

Static Public Member Functions
static EDepInGas &	getInstance ()
	Static method to get a reference to the EDepInGas instance. More...

Private Member Functions
	EDepInGas ()
	Singleton class.
	EDepInGas (const EDepInGas &)
	Singleton class.
EDepInGas &	operator= (const EDepInGas &)
	Singleton class.

Private Attributes
double	m_z1 = 0
	Z of He-C2H6 gas.
double	m_a1 = 0
	A of He-C2H6 gas.
double	m_i1 = 0
	I of He-C2H6 gas.
double	m_rho1 = 0
	rho of He-C2H6 gas
double	m_z2 = 0
	Z of "wire gas".
double	m_a2 = 0
	A of "wire gas".
double	m_i2 = 0
	I of "wire gas".
double	m_rho2 = 0
	rho of "wire gas"
double	m_z0 = 0
	Z of wire+gas.
double	m_a0 = 0
	A of wire+gas.
double	m_i0 = 0
	I of wire+gas.
double	m_rho0 = 0
	rho of wire+gas
const double	m_massE = 0.51099895e6
	electron mass
double	m_ak1 [6][2] = {{ }}
	coeffs a for density effect
double	m_bk1 [6][2] = {{ }}
	coeffs b for density effect
double	m_ck1 [6][2] = {{ }}
	coeffs c for density effect

Static Private Attributes
static EDepInGas *	m_pntr = 0
	Pointer that saves the instance of this class.

Detailed Description

The Class for Energy deposit in the gas.

This class provides the energy deposit in the gas.

Definition at line 20 of file EDepInGas.h.

Member Function Documentation

getEDepInGas()

double getEDepInGas	(	int	mode,
		int	pdg,
		double	p,
		double	dx,
		double	e3
	)		const

Return the energy deosite in the gas.

Parameters

mode	0: simple scaling; 1: scaling based on mpe; 2: based on probab.
pdg	pdg code of incoming particle
p	absolute momentum (GeV)
dx	thickness of material (cm)
e3	energy deposit in gas+wire

Definition at line 137 of file EDepInGas.cc.

{
  double xi1 = m_rho1 * (m_z1 / m_a1);
  double xi2 = m_rho2 * (m_z2 / m_a2);
  //  B2DEBUG(m_dbg, (xi1+xi2)/xi1 <<" "<< e3);
  if (mode == 0) return e3 * xi1 / (xi1 + xi2);
 
  static TDatabasePDG* ptrTDatabasePDG = TDatabasePDG::Instance();
  const double mass = ptrTDatabasePDG->GetParticle(pdg)->Mass();
  const double chrg = fabs(ptrTDatabasePDG->GetParticle(pdg)->Charge() / 3);
 
  const double me1 = getMostProbabEDep(mom, mass, chrg, dx, m_z1, m_a1, m_i1, m_rho1);
  if (mode == 2) {
    const double me0 = getMostProbabEDep(mom, mass, chrg, dx, m_z0, m_a0, m_i0, m_rho0);
    return e3 * me1 / me0;
  }
  const double me2 = getMostProbabEDep(mom, mass, chrg, dx, m_z2, m_a2, m_i2, m_rho2);
  if (mode == 1) return e3 * me1 / (me1 + me2);
 
  // extract energy deposit (e1) based on probab., L(e1)*L(e3-e1),
  // where L is the analytic approx. of Landau dist.
  // find lm1 which maximizes probability
  const double mom2 = mom * mom;
  const double beta2 = mom2 / (mass * mass + mom2);
  const double buf = 0.1535e-3 * dx * chrg * chrg / beta2;
  xi1 *= buf;
  xi2 *= buf;
  const double xi1i = 1 / xi1;
  const double xi2i = 1 / xi2;
  const double lm1min =       -me1 * xi1i;
  const double lm1max = (e3 - me1) * xi1i;
  double lm1 = (e3 * me1 / (me1 + me2) - me1) * xi1i; // initial guess
  lm1 = min(lm1, lm1max);
  lm1 = max(lm1, lm1min);
  //  double edm = 1;
  int itry = 0;
  //  B2DEBUG(m_dbg, "e3,me1,me2,xi1i=" << e3 <<" "<< me1 <<" "<< me2 <<" "<< xi1i);
  //  B2DEBUG(m_dbg, "lm1min,lm1max,lm1=" << lm1min <<" "<< lm1max <<" "<< lm1);
  const double lm2b = (e3 - me1 - me2) * xi2i;
  const double r = xi1 * xi2i;
  double deltal = 0;
  double lm1old = lm1;
  while (itry <= 2 || fabs(lm1 - lm1old) > 0.001) {
    ++itry;
    lm1old = lm1;
    if (itry > 50) {
      //      B2DEBUG(m_dbg, "itry > 50" << "itry,lm1min,lm1max,lm1,edm=" << itry <<" "<< lm1min <<" "<< lm1max <<" "<< lm1);
      break;
    }
    lm1 -= deltal;
    lm1 = max(lm1min, lm1);
    lm1 = min(lm1max, lm1);
    double lm2 = lm2b - r * lm1;
    double emlm1 = exp(-lm1);
    double emlm2 = exp(-lm2);
    double dldlm1   = 1 - emlm1 - r + r * emlm2;
    double dl2dlm12 =     emlm1   + r * r * emlm2;
    deltal = dldlm1 / dl2dlm12;
    //    edm  = dldlm1 * deltal; //drop 0.5* for speed up
  }
 
  if (mode == 3) return xi1 * lm1 + me1;
 
  double lm2 = lm2b - r * lm1;
  double lmin = 0.5 * (lm1 + lm2 + exp(-lm1) + exp(-lm2));
  const double ymax = exp(-lmin);
  //  if (ymax < 1.e-10) return e3*me1/(me1+me2);
 
  // generate e1 according to probab.
  const double lm1w = lm1max - lm1min;
  double y = 10;
  double p =  1;
  int jtry = 0;
  double urndm[2];
  while (y > p) {
    ++jtry;
    if (jtry > 500) {
      //      B2DEBUG(m_dbg, "jtry > 500" <<"ymax" << ymax);
      lm1 = (e3 * me1 / (me1 + me2) - me1) * xi1i;
      break;
    }
    gRandom->RndmArray(2, urndm);
    lm1 = lm1min + lm1w * urndm[0];
    lm2 = lm2b - r * lm1;
    double l = 0.5 * (lm1 + lm2 + exp(-lm1) + exp(-lm2));
    p = exp(-l);
    y = ymax * urndm[1];
  }
 
  return xi1 * lm1 + me1;
}

getInstance()

EDepInGas & getInstance ( )

static

Static method to get a reference to the EDepInGas instance.

Returns

A reference to an instance of this class.

Definition at line 23 of file EDepInGas.cc.

getMostProbabEDep()

double getMostProbabEDep	(	double	p,
		double	mass,
		double	zi,
		double	dx,
		double	z,
		double	a,
		double	i,
		double	rho
	)		const

Return the energy deosite in the material.

Parameters

p	absolute momentum (GeV)
mass	lmass of incoming particle (GeV)
zi	z of incoming particle
dx	thickness of material (cm)
z	atomic number of material
a	atomic weight of material
i	ionization potential of material (eV)
rho	density of material

Definition at line 229 of file EDepInGas.cc.

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

• cdc/modules/cdcDigitizer/include/EDepInGas.h
• cdc/modules/cdcDigitizer/src/EDepInGas.cc