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FlowMapper.h
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81 lines (61 loc) · 2.7 KB
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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
#ifndef ALICEO2_EVENTGEN_FLOWMAPPER_H_
#define ALICEO2_EVENTGEN_FLOWMAPPER_H_
#include "TH1D.h"
#include "TH3D.h"
#include "TF1.h"
namespace o2
{
namespace eventgen
{
/*****************************************************************/
/*****************************************************************/
// this class implements a mapper that introduces a synthetic v2
// into an otherwise uniform initial distribution of phis. It can
// be used, for instance, to create artificial flow of realistic
// intensity in PYTHIA simulations.
// The input histograms are to be read from the CCDB and can
// be customized if necessary. Multiple copies of this mapper
// could be used in case different species should have different
// additional flow.
// N.B.: the main advantages of this mapper is that:
// 1) it preserves total number of particles
// 2) it retains a (distorted) event structure from
// an original event generator (e.g. PYTHIA)
class FlowMapper
{
public:
// Constructor
FlowMapper();
void Setv2VsPt(TH1D hv2VsPtProvided);
void SetEccVsB(TH1D hEccVsBProvided);
void SetNBinsPhi(long mBinsPhiProvided) { mBinsPhi = mBinsPhiProvided; };
void SetPrecision(long mPrecisionProvided) { mPrecision = mPrecisionProvided; };
void SetDerivative(long mDerivativeProvided) { mDerivative = mDerivativeProvided; };
void CreateLUT(); // to be called if all is set
Double_t MapPhi(Double_t lPhiInput, Double_t b, Double_t pt);
long mBinsPhi; // number of phi bins to use
double mPrecision = 1e-6; // precision threshold for numerical inversion success
double mDerivative = 1e-4; // delta-X for derivative calculation
std::unique_ptr<TH1D> mhv2vsPt; // input v2 vs pT from measurement
std::unique_ptr<TH1D> mhEccVsB; // ecc vs B (from Glauber MC or elsewhere)
// Cumulative function to be inverted
std::unique_ptr<TF1> mCumulative;
// the look-up table
std::unique_ptr<TH3D> mhLUT;
ClassDef(FlowMapper, 1);
};
/*****************************************************************/
/*****************************************************************/
} // namespace eventgen
} // namespace o2
#endif /* ALICEO2_EVENTGEN_FLOWMAPPER_H_ */