#ifndef __GRID_MEDIAN_BACKGROUND_ESTIMATOR_HH__
#define __GRID_MEDIAN_BACKGROUND_ESTIMATOR_HH__
//FJSTARTHEADER
// $Id: GridMedianBackgroundEstimator.hh 4354 2018-04-22 07:12:37Z salam $
//
// Copyright (c) 2005-2018, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
//
//----------------------------------------------------------------------
// This file is part of FastJet.
//
// FastJet is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// The algorithms that underlie FastJet have required considerable
// development. They are described in the original FastJet paper,
// hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
// FastJet as part of work towards a scientific publication, please
// quote the version you use and include a citation to the manual and
// optionally also to hep-ph/0512210.
//
// FastJet is distributed in the hope that it will be useful,
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// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with FastJet. If not, see .
//----------------------------------------------------------------------
//FJENDHEADER
#include "fastjet/tools/BackgroundEstimatorBase.hh"
// if defined then we'll use the RectangularGrid class
//
// (For FastJet 3.2, maybe remove the symbol and simply clean up the
// code below to use exclusively the RectangularGrid)
#define FASTJET_GMBGE_USEFJGRID
#ifdef FASTJET_GMBGE_USEFJGRID
#include "fastjet/RectangularGrid.hh"
#endif
FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
/// @ingroup tools_background
/// \class GridMedianBackgroundEstimator
///
/// Background Estimator based on the median pt/area of a set of grid
/// cells.
///
/// Description of the method:
/// This background estimator works by projecting the event onto a
/// grid in rapidity and azimuth. In each grid cell, the scalar pt
/// sum of the particles in the cell is computed. The background
/// density is then estimated by the median of (scalar pt sum/cell
/// area) for all cells.
///
/// Parameters:
/// The class takes 2 arguments: the absolute rapidity extent of the
/// cells and the size of the grid cells. Note that the size of the cell
/// will be adjusted in azimuth to satisfy the 2pi periodicity and
/// in rapidity to match the requested rapidity extent.
///
/// Rescaling:
/// It is possible to use a rescaling profile. In this case, the
/// profile needs to be set before setting the particles and it will
/// be applied to each particle (i.e. not to each cell).
/// Note also that in this case one needs to call rho(jet) instead of
/// rho() [Without rescaling, they are identical]
///
class GridMedianBackgroundEstimator : public BackgroundEstimatorBase
#ifdef FASTJET_GMBGE_USEFJGRID
, public RectangularGrid
#endif
{
public:
/// @name constructors and destructors
//\{
#ifdef FASTJET_GMBGE_USEFJGRID
//----------------------------------------------------------------
/// \param ymax maximal absolute rapidity extent of the grid
/// \param requested_grid_spacing size of the grid cell. The
/// "real" cell size could differ due e.g. to the 2pi
/// periodicity in azimuthal angle (size, not area)
GridMedianBackgroundEstimator(double ymax, double requested_grid_spacing) :
RectangularGrid(ymax, requested_grid_spacing),
_has_particles(false), _enable_rho_m(true) {}
//----------------------------------------------------------------
/// Constructor based on a user's fully specified RectangularGrid
GridMedianBackgroundEstimator(const RectangularGrid & grid) :
RectangularGrid(grid),
_has_particles(false), _enable_rho_m(true) {
if (!RectangularGrid::is_initialised())
throw Error("attempt to construct GridMedianBackgroundEstimator with uninitialised RectangularGrid");
}
//----------------------------------------------------------------
/// Constructor with the explicit parameters for the underlying
/// RectangularGrid
///
/// \param rapmin the minimum rapidity extent of the grid
/// \param rapmax the maximum rapidity extent of the grid
/// \param drap the grid spacing in rapidity
/// \param dphi the grid spacing in azimuth
/// \param tile_selector optional (geometric) selector to specify
/// which tiles are good; a tile is good if
/// a massless 4-vector at the center of the tile passes
/// the selection
GridMedianBackgroundEstimator(double rapmin_in, double rapmax_in, double drap_in, double dphi_in,
Selector tile_selector = Selector()) :
RectangularGrid(rapmin_in, rapmax_in, drap_in, dphi_in, tile_selector),
_has_particles(false), _enable_rho_m(true) {}
#else // alternative in old framework where we didn't have the rectangular grid
GridMedianBackgroundEstimator(double ymax, double requested_grid_spacing) :
_ymin(-ymax), _ymax(ymax),
_requested_grid_spacing(requested_grid_spacing),
_has_particles(false), _enable_rho_m(true)
{
setup_grid();
}
#endif // FASTJET_GMBGE_USEFJGRID
//\}
/// @name setting a new event
//\{
//----------------------------------------------------------------
/// tell the background estimator that it has a new event, composed
/// of the specified particles.
void set_particles(const std::vector & particles);
/// determine whether the automatic calculation of rho_m and sigma_m
/// is enabled (by default true)
void set_compute_rho_m(bool enable){ _enable_rho_m = enable;}
//\}
/// @name retrieving fundamental information
//\{
//----------------------------------------------------------------
/// returns rho, the median background density per unit area
double rho() const;
/// returns sigma, the background fluctuations per unit area; must be
/// multipled by sqrt(area) to get fluctuations for a region of a
/// given area.
double sigma() const;
/// returns rho, the background density per unit area, locally at the
/// position of a given jet. Note that this is not const, because a
/// user may then wish to query other aspects of the background that
/// could depend on the position of the jet last used for a rho(jet)
/// determination.
double rho(const PseudoJet & jet);
/// returns sigma, the background fluctuations per unit area, locally at
/// the position of a given jet. As for rho(jet), it is non-const.
double sigma(const PseudoJet & jet);
/// returns true if this background estimator has support for
/// determination of sigma
bool has_sigma() {return true;}
//-----------------------------------------------------------------
/// Returns rho_m, the purely longitudinal, particle-mass-induced
/// component of the background density per unit area
double rho_m() const;
/// returns sigma_m, a measure of the fluctuations in the purely
/// longitudinal, particle-mass-induced component of the background
/// density per unit area; must be multipled by sqrt(area) to get
/// fluctuations for a region of a given area.
double sigma_m() const;
/// Returns rho_m locally at the jet position. As for rho(jet), it is non-const.
double rho_m(const PseudoJet & jet);
/// Returns sigma_m locally at the jet position. As for rho(jet), it is non-const.
double sigma_m(const PseudoJet & jet);
/// Returns true if this background estimator has support for
/// determination of rho_m.
///
/// Note that support for sigma_m is automatic if one has sigma and
/// rho_m support.
bool has_rho_m() const {return _enable_rho_m;}
/// returns the area of the grid cells (all identical, but
/// referred to as "mean" area for uniformity with JetMedianBGE).
double mean_area() const {return mean_tile_area();}
//\}
/// @name configuring the behaviour
//\{
//----------------------------------------------------------------
/// Set a pointer to a class that calculates the rescaling factor as
/// a function of the jet (position). Note that the rescaling factor
/// is used both in the determination of the "global" rho (the pt/A
/// of each jet is divided by this factor) and when asking for a
/// local rho (the result is multiplied by this factor).
///
/// The BackgroundRescalingYPolynomial class can be used to get a
/// rescaling that depends just on rapidity.
///
/// Note that this has to be called BEFORE any attempt to do an
/// actual computation
///
/// The same profile will be used for both pt and mt (this is
/// probabaly a good approximation since the particle density
/// changes is what dominates the rapidity profile)
virtual void set_rescaling_class(const FunctionOfPseudoJet * rescaling_class);
//\}
/// @name description
//\{
//----------------------------------------------------------------
/// returns a textual description of the background estimator
std::string description() const;
//\}
private:
#ifndef FASTJET_GMBGE_USEFJGRID
/// configure the grid
void setup_grid();
/// retrieve the grid cell index for a given PseudoJet
int tile_index(const PseudoJet & p) const;
// information about the grid
double _ymin, _ymax, _dy, _dphi, _requested_grid_spacing, _tile_area;
int _ny, _nphi, _ntotal;
int n_tiles() const {return _ntotal;}
int n_good_tiles() const {return n_tiles();}
int tile_is_good(int /* itile */) const {return true;}
double mean_tile_area() const {return _tile_area;}
#endif // FASTJET_GMBGE_USEFJGRID
/// verify that particles have been set and throw an error if not
void verify_particles_set() const;
// information abotu the event
//std::vector _scalar_pt;
double _rho, _sigma, _rho_m, _sigma_m;
bool _has_particles;
bool _enable_rho_m;
// various warnings to inform people of potential dangers
LimitedWarning _warning_rho_of_jet;
LimitedWarning _warning_rescaling;
};
FASTJET_END_NAMESPACE // defined in fastjet/internal/base.hh
#endif // __GRID_MEDIAN_BACKGROUND_ESTIMATOR_HH__