#include <JETSCAPE/blob/main/external_packages/trento/src/rapidity_profile.h>

Public Member Functions
	cumulant_generating ()

void	calculate_dsdy (double mean, double std, double skew)

double	interp_dsdy (double y)

Private Attributes
size_t const	N

double *	data

double *	dsdy

double	eta_max

double	deta

double	center

Detailed Description

A class for cumulant generating function inversion This class handles inverse fourier transform the cumulant generating function A direct transformation F^{-1} exp(i*m*k-(std*k)^2/2-skew*(std*k)^3/6) results in an ill-behaved function. Instead, skew is replaced by skew*exp(-(std*k)^2/2). In this way higher order cumulant are included to regulated the function. The reconstruction range is taken to be [-3.33, 3.33]*std, which does not seem to be very large, however, by trail and error, this range elimiates oscillations at large rapidity and leaves the details close to mid-rapidity unchanged. We used GSL FFT library (more specialized library would be FFTW, e.g.), with 256 points. The transformed results are stored and interpolated.

Definition at line 103 of file rapidity_profile.h.

View newest version in sPHENIX GitHub at line 103 of file rapidity_profile.h

Constructor & Destructor Documentation

cumulant_generating::cumulant_generating ( )

inline

Definition at line 112 of file rapidity_profile.h.

View newest version in sPHENIX GitHub at line 112 of file rapidity_profile.h

Member Function Documentation

void cumulant_generating::calculate_dsdy	(	double	mean,
		double	std,
		double	skew
	)

inline

This function set the mean, std and skew of the profile and use FFT to transform cumulant generating function at zero mean.

Definition at line 116 of file rapidity_profile.h.

View newest version in sPHENIX GitHub at line 116 of file rapidity_profile.h

References center, data, deta, dsdy, eta_max, i, IMAG, mean(), N, and REAL.

Referenced by trento::Event::compute_reduced_thickness().

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double cumulant_generating::interp_dsdy ( double y )

inline

When interpolating the funtion, the mean is put back by simply shifting the function by y = y - mean + dy/2, the last term is correcting for interpolating bin edge instead of bin center

Definition at line 144 of file rapidity_profile.h.

View newest version in sPHENIX GitHub at line 144 of file rapidity_profile.h

References center, deta, dsdy, eta_max, and Acts::Svg::View::xy().

Referenced by trento::Event::compute_reduced_thickness().

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