Fast Evolution of Parton Distributions
Static Public Member Functions | List of all members
integration_contour Class Reference

#include <integration_contour.h>

Static Public Member Functions

static double nonsinglet (const partondistribution &f, double Q, double x, double u)
 
static vector_d singlet (const partondistribution &s, const partondistribution &g, double Q, double x, double u)
 
static vector_d singlet_with_qed (const partondistribution &Delta, const partondistribution &s, const partondistribution &g, const partondistribution &phot, const partondistribution &lept, double Q, double x, double u)
 

Detailed Description

This class provides some helper methods to perform numerically an inverse Mellin transform along a parabolic contour.

Member Function Documentation

§ nonsinglet()

double nonsinglet ( const partondistribution f,
double  Q,
double  x,
double  u 
)
static

This method returns

\[ \frac{c_2}{2 \pi} \mbox{Re}\; \left( e^u \left( 1 - i c_2 c_3 \sqrt{u} \right) EF(x,z) \right) \]

where

\[ z = c_0 + i c_2 \sqrt{u} + \frac{1}{2} c_2^2 c_3 u, \]

\[ c_2 = \sqrt{\frac{2 F F''}{F''^2 - F' F'''}}, \]

\[ c_3 = \frac{F'''}{3 F''}, \]

\[ F(x,z) = x^{-z} \sum\limits_{i=0}^{n-1} A_i B(z+\alpha_i-1,1+\beta_i), \]

\[ EF(x,z) = x^{-z} E^z(Q^2,Q_0^2) \sum\limits_{i=0}^{n-1} A_i B(z+\alpha_i-1,1+\beta_i), \]

and $c_0$ is the minimum of $F$ on the real axis right to the rightmost pole.

§ singlet()

vector_d singlet ( const partondistribution s,
const partondistribution g,
double  Q,
double  x,
double  u 
)
static

Same as integration_contour::nonsinglet, but now for the singlet case.

§ singlet_with_qed()

vector_d singlet_with_qed ( const partondistribution Delta,
const partondistribution s,
const partondistribution g,
const partondistribution phot,
const partondistribution lept,
double  Q,
double  x,
double  u 
)
static

Same as integration_contour::singlet, but now with the inclusion of QED effects.


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