BW_t Struct Reference

Description: The class to treat resonances, their lineshapes, and dispersion relation integral. More...

Public Member Functions
	BW_t (double m, double gtot, double ghad, double bll, double alpha=1/137.035999084)
	m is the mass of a resonance gtot is the total width of a resonance ghad is the hadronic width of a resonance bll is the leptonic width of a resonance alpha is the fine structure constant (it might depend on energy scale)
double	R (double s) const
	resonance shape
double	Rp (double s) const
	the first derivative of a resonance shape
double	Rpp (double s) const
	the second derivative of a resonance shape
double	DRIntegral (double s, double sp) const
	Dispersion relation indefinite integral: s is the parmeter, sp is the integration variable.
void	addknots (std::vector< double > &en) const
	Based on the resonance parameters place knots for linear piece-wise approximation with enough precision.

Public Attributes
double	Mv2
	resonance mass squared
double	Gv2
	resonance width squared
double	A
	resonance total amplitude

Detailed Description

Description: The class to treat resonances, their lineshapes, and dispersion relation integral.

Definition at line 224 of file EvtbTosllNPR.cc.

Constructor & Destructor Documentation

BW_t()

BW_t ( double m, double gtot, double ghad, double bll, double alpha = 1 / 137.035999084 )

inline

m is the mass of a resonance gtot is the total width of a resonance ghad is the hadronic width of a resonance bll is the leptonic width of a resonance alpha is the fine structure constant (it might depend on energy scale)

Definition at line 241 of file EvtbTosllNPR.cc.

  {
    //        const double alpha = 1 / 137.035999084;    // (+-21) PDG 2021
    Mv2 = m * m;
    Gv2 = gtot * gtot;
    A = (9 / (alpha * alpha)) * bll * gtot * ghad;
  }

Member Function Documentation

addknots()

void addknots ( std::vector< double > & en ) const

inline

Based on the resonance parameters place knots for linear piece-wise approximation with enough precision.

The current method might be not optimal but the better strategy requires more investigations.

Definition at line 297 of file EvtbTosllNPR.cc.

  {
    double Mv = sqrt(Mv2), Gv = sqrt(Gv2);
    double w = 0.6;
    double smin = (Mv - w * Gv) * (Mv - w * Gv);
    double smax = (Mv + w * Gv) * (Mv + w * Gv);
    en.push_back(Mv * Mv);
    for (int i = 0, n = 30; i < n; i++) {
      double s = smin + (smax - smin) * (i + 0.5) / n;
      en.push_back(s);
    }
    w = 2;
    double smin1 = (Mv - w * Gv) * (Mv - w * Gv);
    double smax1 = (Mv + w * Gv) * (Mv + w * Gv);
    for (int i = 0, n = 30; i < n; i++) {
      double s = smin1 + (smax1 - smin1) * (i + 0.5) / n;
      if (s >= smin && s <= smax)
        continue;
      en.push_back(s);
    }
    w = 8;
    double smin2 = (Mv - w * Gv) * (Mv - w * Gv);
    double smax2 = (Mv + w * Gv) * (Mv + w * Gv);
    for (int i = 0, n = 30; i < n; i++) {
      double s = smin2 + (smax2 - smin2) * (i + 0.5) / n;
      if (s >= smin1 && s <= smax1)
        continue;
      en.push_back(s);
    }
    w = 30;
    double smin3 = (Mv - w * Gv) * (Mv - w * Gv);
    double smax3 = (Mv + w * Gv) * (Mv + w * Gv);
    for (int i = 0, n = 30; i < n; i++) {
      double s = smin3 + (smax3 - smin3) * (i + 0.5) / n;
      if (s >= smin2 && s <= smax2)
        continue;
      en.push_back(s);
    }
    w = 100;
    double smin4 = (Mv - w * Gv) * (Mv - w * Gv);
    double smax4 = (Mv + w * Gv) * (Mv + w * Gv);
    for (int i = 0, n = 20; i < n; i++) {
      double s = smin4 + (smax4 - smin4) * (i + 0.5) / n;
      if (s >= smin3 && s <= smax3)
        continue;
      en.push_back(s);
    }
  }

DRIntegral()

double DRIntegral ( double s, double sp ) const

inline

Dispersion relation indefinite integral: s is the parmeter, sp is the integration variable.

Definition at line 282 of file EvtbTosllNPR.cc.

  {
    double zp = sp - Mv2, zp2 = zp * zp;
    double z = s - Mv2, z2 = z * z;
    double GM2 = Mv2 * Gv2, GM = sqrt(GM2);
    double ds = sp - s;
    return A * (0.5 * log(ds * ds / (zp2 + GM2)) - z * atan(zp / GM) / GM) / (z2 + GM2);
  }

R()

double R ( double s ) const

inline

resonance shape

Definition at line 252 of file EvtbTosllNPR.cc.

  {
    double z = s - Mv2, z2 = z * z;
    return A * s / (z2 + Mv2 * Gv2);
  }

Rp()

double Rp ( double s ) const

inline

the first derivative of a resonance shape

Definition at line 261 of file EvtbTosllNPR.cc.

  {
    double z = s - Mv2, z2 = z * z, t = 1 / (z2 + Mv2 * Gv2);
    t *= 1 - 2 * s * z * t;
    return A * t;
  }

Rpp()

double Rpp ( double s ) const

inline

the second derivative of a resonance shape

Definition at line 271 of file EvtbTosllNPR.cc.

  {
    double z = s - Mv2, z2 = z * z, t = 1 / (z2 + Mv2 * Gv2);
    t = t * t * (8 * s * z2 * t - 4 * z - 2 * s);
    return A * t;
  }

Member Data Documentation

A

double A

resonance total amplitude

Definition at line 232 of file EvtbTosllNPR.cc.

Gv2

double Gv2

resonance width squared

Definition at line 229 of file EvtbTosllNPR.cc.

Mv2

double Mv2

resonance mass squared

Definition at line 226 of file EvtbTosllNPR.cc.

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The documentation for this struct was generated from the following file:

• generators/evtgen/models/src/EvtbTosllNPR.cc