ZDCFitWrapper.h

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef ZDCANALYSIS_ZDCFITWRAPPER_H
#define ZDCANALYSIS_ZDCFITWRAPPER_H
 
#include "CxxUtils/checker_macros.h"
 
// Base class that defines the interface
//
#include <TF1.h>
#include <memory>
#include <cmath>
#include <stdexcept>
#include <algorithm> //std::max
 
inline double ZDCFermiExpFit(const double* xvec, const double* pvec);
inline double ZDCFermiExpFitRefl(const double* xvec, const double* pvec);
inline double ZDCFermiExpFitInduct(const double* xvec, const double* pvec);
 
class ZDCFitWrapper
{
private:
  std::shared_ptr<TF1> m_wrapperTF1{};
 
  float m_tmin{0};
  float m_tmax{0};
 
  float m_ampMin{0};
  float m_ampMax{0};
 
  float m_t0Min{0};
  float m_t0Max{0};
 
  bool  m_adjTLimitsEvent{false};
  float m_tminAdjust{0};
  float m_tempTmin{0};
  float m_tempTmax{0};
  
protected:
  // Actually sets the t0 parameter limits in the fit function
  //
  virtual void SetT0FitLimits(float tMin, float tMax) = 0;
 
public:
  ZDCFitWrapper(const std::shared_ptr<TF1>& wrapperTF1) : m_wrapperTF1(wrapperTF1),
    m_ampMin(0),
    m_adjTLimitsEvent(true)  // true here forces a setting of T0 par limits on first event
  {
    m_tmin = m_wrapperTF1->GetXmin();
    m_tmax = m_wrapperTF1->GetXmax();
 
    m_t0Min = m_tmin;
    m_t0Max = m_tmax;
  }
 
  virtual ~ZDCFitWrapper() {}
 
  void Initialize(float initialAmp, float initialT0, float ampMin, float ampMax);
  void Initialize(float initialAmp, float initialT0, float ampMin, float ampMax, float fitTmin, float fitTmax, float fitTRef);
 
  // Performs the class-specific event initialization
  //
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) = 0;
 
  void SetAmpMinMax(float minAmp, float maxAmp)
  {
    m_ampMin = minAmp;
    m_ampMax = maxAmp;
  }
 
  void SetT0Range(float t0Min, float t0Max)
  {
    m_t0Min = t0Min;
    m_t0Max = t0Max;
 
    SetT0FitLimits(t0Min, t0Max);
  }
 
  virtual void ConstrainFit() = 0;
  virtual void UnconstrainFit() = 0;
 
  virtual float GetAmplitude() const = 0;
  virtual float GetAmpError() const = 0;
  virtual float GetTime() const = 0;
  virtual float GetTau1() const = 0;
  virtual float GetTau2() const = 0;
 
  float GetMinAmp() const {return m_ampMin;}
  float GetMaxAmp() const {return m_ampMax;}
 
  float GetTMin() const {return m_tmin;}
  float GetTMax() const {return m_tmax;}
 
  float GetT0Min() const {
    if (m_adjTLimitsEvent) return m_tempTmin;
    else return m_t0Min;
  }
  
  float GetT0Max() const {
    if (m_adjTLimitsEvent) return m_tempTmax;
    else return m_t0Max;
  }
 
  float GetTMinAdjust() const {return m_tminAdjust;}
 
  virtual float GetBkgdMaxFraction() const = 0;
 
  virtual unsigned int GetNumShapeParameters() const = 0;
  virtual float GetShapeParameter(size_t index) const = 0;
 
  virtual double operator()(const double *x, const double *p) = 0;
 
  virtual std::shared_ptr<TF1> GetWrapperTF1() {return m_wrapperTF1;}
  virtual const TF1* GetWrapperTF1() const {return m_wrapperTF1.get();}
  virtual TF1* GetWrapperTF1RawPtr() const {return m_wrapperTF1.get();}
};
 
class ATLAS_NOT_THREAD_SAFE ZDCPrePulseFitWrapper : public ZDCFitWrapper
{
protected:
  float m_preT0Min;
  float m_preT0Max;
public:
  ZDCPrePulseFitWrapper(std::shared_ptr<TF1> wrapperTF1) : ZDCFitWrapper(wrapperTF1)
  {
    m_preT0Min = GetTMin();
    m_preT0Max = GetTMax();
  }
 
  virtual void SetInitialPrePulse(float amp, float t0, float expamp, bool fixPrePulseToZero) = 0;
 
  virtual void SetPrePulseT0Range(float tmin, float tmax) = 0;
  virtual void SetPostPulseT0Range(float tmin, float tmax, float initialPostT0) = 0;
 
  virtual unsigned int GetPreT0ParIndex() const = 0;
 
  virtual float GetPreT0()  const = 0;
  virtual float GetPreAmp() const = 0;
 
  virtual float GetPostT0()  const = 0;
  virtual float GetPostAmp() const = 0;
 
  virtual float GetExpAmp()  const = 0;
};
 
class ATLAS_NOT_THREAD_SAFE ZDCPreExpFitWrapper : public ZDCFitWrapper
{
protected:
  float m_defaultTau;
  bool m_fixTau;
 
public:
  ZDCPreExpFitWrapper(std::shared_ptr<TF1> wrapperTF1, float defaultExpTau, bool fixTau) :
    ZDCFitWrapper(wrapperTF1), m_defaultTau(defaultExpTau), m_fixTau(fixTau)
    {}
 
  virtual void SetInitialExpPulse(float expamp) = 0;
 
  bool fixExpTau() const {return m_fixTau;}
  float getDefaultExpTau() const {return m_defaultTau;}
  
  virtual float GetExpAmp() const = 0;
  virtual float GetExpTau() const = 0;
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiVariableTaus : public ZDCFitWrapper
{
protected:
  bool m_fixTau1{false};
  bool m_fixTau2{false};
 
  float m_tau1{0};
  float m_tau2{0};
 
public:
 
  ZDCFitExpFermiVariableTaus(const std::string& tag, float tmin, float tmax, bool fixTau1, bool fixTau2, float tau1, float tau2);
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return GetWrapperTF1()->GetParameter(2);}
  virtual float GetTau2() const override {return GetWrapperTF1()->GetParameter(3);}
 
  virtual float GetTime() const override {
    const TF1* theTF1 = GetWrapperTF1();
 
    float fitT0 =  theTF1->GetParameter(1);
 
    float tau1 = theTF1->GetParameter(2);
    float tau2 = theTF1->GetParameter(3);
 
    // Correct the time to the maximum
    //
    if (tau2 > tau1) fitT0 += tau1 * std::log(tau2 / tau1 - 1.0);
    return fitT0;
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 1;}
      
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index == 0) return GetWrapperTF1()->GetParameter(4);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double amp = theTF1->GetParameter(0);
    double constant = theTF1->GetParameter(4);
 
    if (amp > 0) return constant / amp;
    else return -1;
  }
 
  virtual double operator()(const double *x, const double *p)  override{
    return ZDCFermiExpFit(x, p);
  }
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
};
 
//
// A special version of the fermi*negative exponential function that includes a term to describe
//   the "reflection" effects we see in the ZDC+LHCf joint run due to the splitting of the ZDC
//   signals to send a copy to LHCf DAQ. It's not really a reflection but an artifact introduced
//   by the bandwidth limit of the linear fan-in/fan-out module that we used.
//
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiVariableTausLHCf : public ZDCFitWrapper
{
protected:
  bool m_fixTau1{false};
  bool m_fixTau2{false};
 
  float m_tau1{0};
  float m_tau2{0};
 
public:
 
  ZDCFitExpFermiVariableTausLHCf(const std::string& tag, float tmin, float tmax, bool fixTau1, bool fixTau2, float tau1, float tau2);
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return GetWrapperTF1()->GetParameter(2);}
  virtual float GetTau2() const override {return GetWrapperTF1()->GetParameter(3);}
 
  virtual float GetTime() const override {
    const TF1* theTF1 = GetWrapperTF1();
 
    float fitT0 =  theTF1->GetParameter(1);
 
    float tau1 = theTF1->GetParameter(2);
    float tau2 = theTF1->GetParameter(3);
 
    // Correct the time to the maximum
    //
    if (tau2 > tau1) fitT0 += tau1 * std::log(tau2 / tau1 - 1.0);
    return fitT0;
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 5;}
 
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 5) return GetWrapperTF1()->GetParameter(5+index);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double amp = theTF1->GetParameter(0);
    double constant = theTF1->GetParameter(4);
 
    if (amp > 0) return constant / amp;
    else return 1;
  }
 
  virtual double operator()(const double *x, const double *p)  override{
    return ZDCFermiExpFitRefl(x, p);
  }
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiVariableTausInduct : public ZDCFitWrapper
{
protected:
  bool m_fixTau1{false};
  bool m_fixTau2{false};
 
  float m_tau1{0};
  float m_tau2{0};
 
public:
 
  ZDCFitExpFermiVariableTausInduct(const std::string& tag, float tmin, float tmax, bool fixTau1, bool fixTau2, float tau1, float tau2);
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return GetWrapperTF1()->GetParameter(2);}
  virtual float GetTau2() const override {return GetWrapperTF1()->GetParameter(3);}
 
  virtual float GetTime() const override {
    const TF1* theTF1 = GetWrapperTF1();
 
    float fitT0 =  theTF1->GetParameter(1);
 
    float tau1 = theTF1->GetParameter(2);
    float tau2 = theTF1->GetParameter(3);
 
    // Correct the time to the maximum
    //
    if (tau2 > tau1) fitT0 += tau1 * std::log(tau2 / tau1 - 1.0);
    return fitT0;
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 5;}
 
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 5) return GetWrapperTF1()->GetParameter(4+index);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double amp = theTF1->GetParameter(0);
    double constant = theTF1->GetParameter(4);
 
    if (amp > 1e-6) return constant / amp;
    else return 1;
  }
 
  virtual double operator()(const double *x, const double *p)  override{
    return ZDCFermiExpFitInduct(x, p);
  }
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiVariableTausRun3 : public ZDCFitExpFermiVariableTaus
{
public:
  ZDCFitExpFermiVariableTausRun3(const std::string& tag, float tmin, float tmax, bool fixTau1, bool fixTau2, float tau1, float tau2);
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiFixedTaus : public ZDCFitWrapper
{
private:
  float m_tau1{0};
  float m_tau2{0};
 
  float m_norm{0};
  float m_timeCorr{0};
 
  std::shared_ptr<TF1> m_expFermiFunc{};
 
public:
 
  ZDCFitExpFermiFixedTaus(const std::string& tag, float tmin, float tmax, float tau1, float tau2);
 
  ~ZDCFitExpFermiFixedTaus() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 2;}
    
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index == 0) return m_tau1;
    else if (index == 1) return m_tau2;
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    
    double C = theTF1->GetParameter(2);
    return C / amp;
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double amp = p[0];
    double t0 = p[1];
    double C = p[2];
 
    double deltaT = x[0] - t0;
 
    double expFermi =  amp * m_norm * m_expFermiFunc->operator()(deltaT);
 
    return expFermi + C; // + bckgd;
  }
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiPrePulse : public ZDCPrePulseFitWrapper
{
private:
  float m_tau1{0};
  float m_tau2{0};
  float m_norm{0};
  float m_timeCorr{0};
 
  std::shared_ptr<TF1> m_expFermiFunc = 0;
  std::shared_ptr<TF1> m_expFermiPreFunc = 0;
 
public:
  ZDCFitExpFermiPrePulse(const std::string& tag, float tmin, float tmax, float tau1, float tau2);
  ~ZDCFitExpFermiPrePulse() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
 
  virtual void SetInitialPrePulse(float amp, float t0, float /*expamp = 0*/, bool /*fixPrePulseToZero = false*/) override {
    GetWrapperTF1()->SetParameter(2, std::max(amp, (float) 1.5)); //1.5 here ensures that we're above lower limit
    GetWrapperTF1()->SetParameter(3, t0);
  }
 
  virtual void SetPrePulseT0Range(float tmin, float tmax) override;
  virtual void SetPostPulseT0Range(float /*tmin*/, float /*tmax*/, float /*initialPostT0*/) override {return;}
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual unsigned int GetPreT0ParIndex() const override {return 3;}
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetPreT0()  const override {return 0;}
  virtual float GetPreAmp() const override {return 0;}
 
  virtual float GetPostT0()  const override {return 0;}
  virtual float GetPostAmp() const override {return 0;}
 
  virtual float GetExpAmp() const override {return 0;}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 1;}
    
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 1) return GetWrapperTF1()->GetParameter(4);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
 
    double maxTime = GetTime();
 
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    
    double preAmp = theTF1->GetParameter(2);
    double preT0 = theTF1->GetParameter(3);
 
    double deltaTPre = maxTime - preT0;
    double background = preAmp * m_norm * m_expFermiFunc->operator()(deltaTPre);
 
    return background / (amp + background);
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp = p[0];
    double t0 = p[1];
    double preAmp = p[2];
    double preT0 = p[3];
    double C = p[4];
 
    double deltaT = t - t0;
    double deltaTPre = t - preT0;
 
    // We subtract off the  value of the pre-pulse at the minimum time (nominally 0,
    //   but can change if we exclude early samples) to account for the subtraction of the pre-sample
    //
    double deltaPresamp = GetTMinAdjust() - preT0;
 
    // double bckgd = linSlope*t;
 
    double pulse1 =  amp*m_norm*m_expFermiFunc->operator()(deltaT);
    double pulse2 =  preAmp * m_norm * (m_expFermiFunc->operator()(deltaTPre) -
                    m_expFermiFunc->operator()(deltaPresamp));
 
    return C + pulse1 + pulse2;// + bckgd;
  }
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiLHCfPrePulse : public ZDCPrePulseFitWrapper
{
private:
  float m_tau1{0};
  float m_tau2{0};
  float m_timeCorr{0};
 
  double m_preNorm{1.};
  
  std::shared_ptr<TF1> m_expFermiLHCfFunc = 0;
  std::shared_ptr<TF1> m_expFermiPreFunc = 0;
 
public:
  ZDCFitExpFermiLHCfPrePulse(const std::string& tag, float tmin, float tmax, float tau1, float tau2);
  ~ZDCFitExpFermiLHCfPrePulse() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
 
  virtual void SetInitialPrePulse(float amp, float t0, float /*expamp = 0*/, bool /*fixPrePulseToZero = false*/) override
  {
    double ampMin, ampMax;
    
    GetWrapperTF1()->GetParLimits(2, ampMin, ampMax);
    double initialAmp = std::min<double>(std::max<double>(amp, ampMin), ampMax);
    
    GetWrapperTF1()->SetParameter(4, initialAmp);
    GetWrapperTF1()->SetParameter(5, t0);
  }
 
  virtual void SetPrePulseT0Range(float tmin, float tmax) override;
  virtual void SetPostPulseT0Range(float /*tmin*/, float /*tmax*/, float /*initialPostT0*/) override {return;}
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual unsigned int GetPreT0ParIndex() const override {return 3;}
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetPreT0()  const override {return GetWrapperTF1()->GetParameter(3);}
  virtual float GetPreAmp() const override {return GetWrapperTF1()->GetParameter(3);}
 
  virtual float GetPostT0()  const override {return 0;}
  virtual float GetPostAmp() const override {return 0;}
 
  virtual float GetExpAmp() const override {return 0;}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 1;}
  
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 1) return GetWrapperTF1()->GetParameter(6);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
 
    double maxTime = GetTime();
 
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    
    double preAmp = theTF1->GetParameter(2);
    double preT0 = theTF1->GetParameter(3);
 
    double deltaTPre = maxTime - preT0;
    double background = preAmp * m_preNorm * m_expFermiLHCfFunc->operator()(deltaTPre);
 
    return background / (amp + background);
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp = p[0];
    double t0 = p[1];
    double tau1 = p[2];
    double tau2 = p[3];
    double preAmp = p[4];
    double preT0 = p[5];
    double C = p[6];
 
    m_expFermiLHCfFunc->SetParameter(0, amp);
    m_expFermiLHCfFunc->SetParameter(2, tau1);
    m_expFermiLHCfFunc->SetParameter(3, tau2);
    m_expFermiLHCfFunc->SetParameter(4, tau2);
 
    double deltaT = t - t0;
    double deltaTPre = t - preT0;
 
    // We subtract off the  value of the pre-pulse at the minimum time (nominally 0,
    //   but can change if we exclude early samples) to account for the subtraction of the pre-sample
    //
    double deltaPresamp = GetTMinAdjust() - preT0;
 
    double pulse1 =  m_expFermiLHCfFunc->operator()(deltaT);
    double pulse2 =  preAmp * m_preNorm * (m_expFermiPreFunc->operator()(deltaTPre) -
                       m_expFermiPreFunc->operator()(deltaPresamp));
 
    return C + pulse1 + pulse2;
  }
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiPreExp : public ZDCPreExpFitWrapper
{
private:
  float m_tau1{0};
  float m_tau2{0};
  float m_timeCorr{0};
  double m_norm{};
  
  std::shared_ptr<TF1> m_expFermiFunc{0};
  std::shared_ptr<TF1> m_expFermiPreFunc{0};
 
public:
  ZDCFitExpFermiPreExp(const std::string& tag, float tmin, float tmax, float tau1, float tau2,
               float defExpTau, float fixExpTau);
  ~ZDCFitExpFermiPreExp() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void SetInitialExpPulse(float amp) override
  {
    GetWrapperTF1()->SetParameter(2, std::max(amp, (float) 0.5)); //0.5 here ensures that we're above lower limit (0)   
  }
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual float GetExpAmp() const override {return GetWrapperTF1()->GetParameter(2);}
  virtual float GetExpTau() const override {return GetWrapperTF1()->GetParameter(3);}
 
  virtual unsigned int GetNumShapeParameters() const override {return 2;}
 
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 2) return GetWrapperTF1()->GetParameter(index + 4);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double maxTime = GetTime();
 
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    
    double preAmp = theTF1->GetParameter(2);
    double preT0 = theTF1->GetParameter(3);
 
    double deltaTPre = maxTime - preT0;
    double background = preAmp * m_norm * m_expFermiFunc->operator()(deltaTPre);
 
    return background / (amp + background);
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp = p[0];
    double t0 = p[1];
    double expAmp = p[2];
    double expTau = p[3];
    double expSqrtTau = p[4];
    double C = p[5];
 
    double deltaT = t - t0;
    double pulse =  amp * m_norm * m_expFermiFunc->operator()(deltaT);
 
    // We subtract off the value of the exponential pulse at the minimum time (nominally 0),
    //   because it would have been included in the baseline subtraction
    //
    double tRef = GetTMinAdjust();
    double expPre = 0;
    if (t > 0 && std::abs(expSqrtTau)>1e-6) expPre = expAmp * (std::exp(-t/expTau-expSqrtTau*std::sqrt(t)) - std::exp(-tRef/expTau));
    else expPre = expAmp * (std::exp(-t/expTau) - std::exp(-tRef/expTau));
      
    return C + pulse + expPre;
  }
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiLHCfPreExp : public ZDCPreExpFitWrapper
{
private:
  float m_tau1{0};
  float m_tau2{0};
  float m_timeCorr{0};
  
  std::shared_ptr<TF1> m_expFermiLHCfFunc{};
  std::shared_ptr<TF1> m_expFermiLHCfPreFunc{};
 
public:
  ZDCFitExpFermiLHCfPreExp(const std::string& tag, float tmin, float tmax, float tau1, float tau2,
               float defExpTau, float fixExpTau);
  ~ZDCFitExpFermiLHCfPreExp() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void SetInitialExpPulse(float amp) override
  {
    GetWrapperTF1()->SetParameter(4, std::max(amp, (float) 0.5)); //0.5 here ensures that we're above lower limit (0)   
  }
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetTime() const override {
    const TF1* theTF1 = GetWrapperTF1();
 
    float fitT0 =  theTF1->GetParameter(1);
 
    float tau1 = theTF1->GetParameter(2);
    float tau2 = theTF1->GetParameter(3);
 
    // Correct the time to the maximum
    //
    if (tau2 > tau1) fitT0 += tau1 * std::log(tau2 / tau1 - 1.0);
    return fitT0;
  }
 
  virtual float GetExpAmp() const override {return GetWrapperTF1()->GetParameter(4);}
  virtual float GetExpTau() const override {return GetWrapperTF1()->GetParameter(5);}
 
  virtual unsigned int GetNumShapeParameters() const override {return 1;}
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 1) return GetWrapperTF1()->GetParameter(5);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
 
    double maxTime = GetTime();
    
    double expAmp = theTF1->GetParameter(4);
    double expTau = theTF1->GetParameter(5);
    double bexpSqrt = theTF1->GetParameter(6);
 
    double tRef = GetTMinAdjust();
    double expPre = expAmp * (std::exp(-maxTime/expTau - bexpSqrt*maxTime*maxTime) - std::exp(-tRef/expTau - bexpSqrt*tRef*tRef));
 
    return expPre / (amp + expPre);
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp = p[0];
    double t0 = p[1];
 
    double tau1 = p[2];
    double tau2 = p[3];
    
    double expAmp = p[4];
    double expTau = p[5];
    double bexpSqrt = p[6];
    double reflFrac = p[7];
 
    m_expFermiLHCfFunc->SetParameter(0, amp);
    m_expFermiLHCfFunc->SetParameter(2, tau1);
    m_expFermiLHCfFunc->SetParameter(3, tau2);
    m_expFermiLHCfFunc->SetParameter(6, reflFrac);
 
    m_timeCorr = m_tau1 * std::log(m_tau2 / m_tau1 - 1.0);
 
    double deltaT = t - t0;
    double pulse = m_expFermiLHCfFunc->operator()(deltaT);
 
    // We subtract off the value of the exponential pulse at the minimum time (nominally 0),
    //   because it would have been included in the baseline subtraction
    //
    double tRef = GetTMinAdjust();
    double expPre = 0;
 
    expPre = expAmp * (std::exp(-t/expTau - bexpSqrt*t*t) - std::exp(-tRef/expTau - bexpSqrt*tRef*tRef));
      
    return pulse + expPre;
  }
};
 
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiInductPreExp : public ZDCPreExpFitWrapper
{
private:
  float m_tau1{0};
  float m_tau2{0};
  float m_timeCorr{0};
  
  std::shared_ptr<TF1> m_expFermiInductFunc{0};
  std::shared_ptr<TF1> m_expFermiPreFunc{0};
 
public:
  ZDCFitExpFermiInductPreExp(const std::string& tag, float tmin, float tmax, float tau1, float tau2,
               float defExpTau, float fixExpTau);
  ~ZDCFitExpFermiInductPreExp() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void SetInitialExpPulse(float amp) override
  {
    GetWrapperTF1()->SetParameter(2, std::max(amp, (float) 0.5)); //0.5 here ensures that we're above lower limit (0)   
  }
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual float GetExpAmp() const override {return GetWrapperTF1()->GetParameter(2);}
  virtual float GetExpTau() const override {return GetWrapperTF1()->GetParameter(3);}
 
  virtual unsigned int GetNumShapeParameters() const override {return 3;}
 
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 3) {
      if (index == 0) return GetWrapperTF1()->GetParameter(4);
      if (index == 1) return GetWrapperTF1()->GetParameter(6);
      if (index == 2) return GetWrapperTF1()->GetParameter(7);
    }
    throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
 
    double maxTime = GetTime();
    
    double expAmp = theTF1->GetParameter(2);
    double expTau = theTF1->GetParameter(3);
    double bexpSqrt = theTF1->GetParameter(4);
 
    double tRef = GetTMinAdjust();
    double expPre = expAmp * (std::exp(-maxTime/expTau - bexpSqrt*maxTime*maxTime) - std::exp(-tRef/expTau - bexpSqrt*tRef*tRef));
 
    return expPre / (amp + expPre);
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp = p[0];
    double t0 = p[1];
 
    double expAmp = p[2];
    double expTau = p[3];
    double bexpSqrt = p[4];
    double C = p[5];
    double inductA = p[6];
    double inductB = p[7];
 
    m_expFermiInductFunc->SetParameter(0, amp);
    m_expFermiInductFunc->SetParameter(6, inductA);
    m_expFermiInductFunc->SetParameter(7, inductB);
 
    double deltaT = t - t0;
    double pulse = m_expFermiInductFunc->operator()(deltaT);
 
    // We subtract off the value of the exponential pulse at the minimum time (nominally 0),
    //   because it would have been included in the baseline subtraction
    //
    double tRef = GetTMinAdjust();
    double expPre = 0;
 
    expPre = expAmp * (std::exp(-t/expTau - bexpSqrt*t*t) - std::exp(-tRef/expTau - bexpSqrt*tRef*tRef));
      
    return pulse + C + expPre;
   }
};
 
 
// ----------------------------------------------------------------------
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiLinearFixedTaus : public ZDCFitWrapper
{
private:
  float m_tau1{};
  float m_tau2{};
 
  float m_norm{};
  float m_timeCorr{};
 
  std::shared_ptr<TF1> m_expFermiFunc;
 
public:
 
  ZDCFitExpFermiLinearFixedTaus(const std::string& tag, float tmin, float tmax, float tau1, float tau2);
 
  ~ZDCFitExpFermiLinearFixedTaus() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 2;}
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 2) return GetWrapperTF1()->GetParameter(index + 2);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    
    double slope = theTF1->GetParameter(2);
 
    double background = slope * GetTime();
    return background / amp;
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double amp    = p[0];
    double t0     = p[1];
    double deltaT = x[0] - t0;
 
    double bckgd = p[2] * x[0] + p[3];
 
    double expFermi =  amp * m_norm * m_expFermiFunc->operator()(deltaT);
 
    return expFermi + bckgd;
  }
};
 
// ----------------------------------------------------------------------
class ATLAS_NOT_THREAD_SAFE ZDCFitExpFermiLinearPrePulse : public ZDCPrePulseFitWrapper
{
private:
  float m_tau1{};
  float m_tau2{};
  float m_norm{};
  float m_timeCorr{};
  std::shared_ptr<TF1> m_expFermiFunc;
 
public:
  ZDCFitExpFermiLinearPrePulse(const std::string& tag, float tmin, float tmax, float tau1, float tau2);
  ~ZDCFitExpFermiLinearPrePulse() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual void SetInitialPrePulse(float amp, float t0, float /*expamp = 0*/, bool /*fixPrePulseToZero = false*/) override {
    GetWrapperTF1()->SetParameter(2, std::max(amp, (float) 1.5)); //1.5 here ensures that we're above lower limit
    GetWrapperTF1()->SetParameter(3, t0);
  }
 
  virtual void SetPrePulseT0Range(float tmin, float tmax) override;
  virtual void SetPostPulseT0Range(float /*tmin*/, float /*tmax*/, float /*initialPostT0*/) override {return;}
 
  unsigned int GetPreT0ParIndex() const override {return 3;}
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetPreT0()  const override {
    float fitPreT0 =  GetWrapperTF1()->GetParameter(3);
 
    // Correct the time to the maximum
    //
    fitPreT0 += m_timeCorr;
 
    return fitPreT0;
  }
  virtual float GetPreAmp() const override {return GetWrapperTF1()->GetParameter(2);}
 
  virtual float GetPostT0()  const override {return 0;}
  virtual float GetPostAmp() const override {return 0;}
 
  virtual float GetExpAmp() const override {return 0;}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 1;}
 
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index < 1) return GetWrapperTF1()->GetParameter(index + 4);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
 
    double maxTime = GetTime();
 
    double amp = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    
    double preAmp = theTF1->GetParameter(2);
    double preT0 = theTF1->GetParameter(3);
    double slope = theTF1->GetParameter(4);
 
    double deltaTPre = maxTime - preT0;
 
    double background = slope * maxTime + preAmp * m_norm * (m_expFermiFunc->operator()(deltaTPre) -
                        m_expFermiFunc->operator()(-preT0));
 
    return background / amp;
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp = p[0];
    double t0 = p[1];
    double preAmp = p[2];
    double preT0 = p[3];
    double linSlope = p[4];
 
    double deltaT = t - t0;
    double deltaTPre = t - preT0;
 
    // We subtract off the  value of the pre-pulse at the minimum time (nominally 0,
    //   but can change if we exclude early samples) to account for the subtraction of the pre-sample
    //
    double deltaPresamp = GetTMinAdjust() - preT0;
 
    double pulse1 =  amp * m_norm * m_expFermiFunc->operator()(deltaT);
    double pulse2 =  preAmp * m_norm * (m_expFermiFunc->operator()(deltaTPre) -
                                        m_expFermiFunc->operator()(deltaPresamp));
 
    double bckgd = linSlope * (t - deltaPresamp) + p[5];
 
    return pulse1 + pulse2 + bckgd;
  }
};
 
 
 
// ----------------------------------------------------------------------
class ATLAS_NOT_THREAD_SAFE ZDCFitComplexPrePulse : public ZDCPrePulseFitWrapper
{
private:
  float m_tau1{};
  float m_tau2{};
  float m_norm{};
  float m_timeCorr{};
  std::shared_ptr<TF1> m_expFermiFunc;
 
public:
  ZDCFitComplexPrePulse(const std::string& tag, float tmin, float tmax, float tau1, float tau2);
  ~ZDCFitComplexPrePulse() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void SetInitialPrePulse(float amp, float t0, float expamp, bool /*fixPrePulseToZero = false*/) override {
    GetWrapperTF1()->SetParameter(2, std::max(amp, (float) 1.5)); //1.5 here ensures that we're above lower limit
    GetWrapperTF1()->SetParameter(3, t0);
    GetWrapperTF1()->SetParameter(6, std::max(std::abs(expamp), (float) 1.5));
  }
  
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual void SetPrePulseT0Range(float tmin, float tmax) override;
  virtual void SetPostPulseT0Range(float /*tmin*/, float /*tmax*/, float /*initialPostT0*/) override {return;}
 
  unsigned int GetPreT0ParIndex() const override {return 3;}
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError() const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetPreT0()  const override {
    float fitPreT0 =  GetWrapperTF1()->GetParameter(3);
 
    // Correct the time to the maximum
    //
    fitPreT0 += m_timeCorr;
 
    return fitPreT0;
  }
  virtual float GetPreAmp() const override {return GetWrapperTF1()->GetParameter(2);}
 
  virtual float GetPostT0()  const override {return 0;}
  virtual float GetPostAmp() const override {return 0;}
 
  virtual float GetExpAmp() const override {return GetWrapperTF1()->GetParameter(6);}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 3;}
    
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index <  3) return GetWrapperTF1()->GetParameter(4 + index);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
 
    double maxTime = GetTime();
 
    double amp    = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    
    double preAmp = theTF1->GetParameter(2);
    double preT0  = theTF1->GetParameter(3);
    double slope  = theTF1->GetParameter(4);
 
    double deltaTPre = maxTime - preT0;
 
    double background = slope * maxTime + preAmp * m_norm * (m_expFermiFunc->operator()(deltaTPre) -
                        m_expFermiFunc->operator()(-preT0));
 
    return background / amp;
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp      = p[0];
    double t0       = p[1];
    double preAmp   = p[2];
    double preT0    = p[3];
    double linSlope = p[4];
    double linConst = p[5];
    double expamp   = p[6];
 
    double deltaT    = t - t0;
    double deltaTPre = t - preT0;
 
    // We subtract off the  value of the pre-pulse at the minimum time (nominally 0,
    //   but can change if we exclude early samples) to account for the subtraction of the pre-sample
    //
    double deltaPresamp = GetTMinAdjust() - preT0;
 
    double pulse1 =  amp    * m_norm *  m_expFermiFunc->operator()(deltaT);
    double pulse2 =  preAmp * m_norm * (m_expFermiFunc->operator()(deltaTPre) - m_expFermiFunc->operator()(deltaPresamp));
 
    double linBG = linSlope * (t - deltaPresamp) + linConst;
    double expBG = expamp * std::exp(-(t) / m_tau2) - expamp;  // deltaPresamp
 
    return pulse1 + pulse2 + linBG + expBG;
  }
};
 
 
// ----------------------------------------------------------------------
class ATLAS_NOT_THREAD_SAFE ZDCFitGeneralPulse : public ZDCPrePulseFitWrapper
{
private:
  float m_tau1{};
  float m_tau2{};
  float m_norm{};
  float m_timeCorr{};
  std::shared_ptr<TF1> m_expFermiFunc;
 
public:
  ZDCFitGeneralPulse(const std::string& tag, float tmin, float tmax, float tau1, float tau2);
  ~ZDCFitGeneralPulse() {}
 
  virtual void DoInitialize(float initialAmp, float initialT0, float ampMin, float ampMax) override;
  virtual void SetT0FitLimits(float tMin, float tMax) override;
 
  virtual void SetInitialPrePulse(float amp, float t0, float expamp, bool fixPrePulseToZero) override {
    GetWrapperTF1()->ReleaseParameter(2);
    GetWrapperTF1()->ReleaseParameter(3);
    GetWrapperTF1()->SetParameter(2, std::max(amp, (float) 1.5)); //1.5 here ensures that we're above lower limit
    GetWrapperTF1()->SetParameter(3, std::max(t0, (float) 20.0));
    GetWrapperTF1()->SetParameter(6, std::max(std::abs(expamp), (float) 1.5));
 
    if (fixPrePulseToZero) {
      GetWrapperTF1()->FixParameter(2, 0. );
      GetWrapperTF1()->FixParameter(3, 20.);
    }
  }
 
  virtual void ConstrainFit() override;
  virtual void UnconstrainFit() override;
 
  virtual void SetPrePulseT0Range(float tmin, float tmax) override;
  virtual void SetPostPulseT0Range(float tmin, float tmax, float initialPostT0) override;
 
  unsigned int GetPreT0ParIndex() const override {return 3;}
 
  virtual float GetAmplitude() const override {return GetWrapperTF1()->GetParameter(0); }
  virtual float GetAmpError()  const override {return GetWrapperTF1()->GetParError(0); }
 
  virtual float GetTau1() const override {return m_tau1;}
  virtual float GetTau2() const override {return m_tau2;}
 
  virtual float GetPreT0()  const override {
    float fitPreT0 =  GetWrapperTF1()->GetParameter(3);
 
    // Correct the time to the maximum
    //
    fitPreT0 += m_timeCorr;
 
    return fitPreT0;
  }
  virtual float GetPreAmp() const override {return GetWrapperTF1()->GetParameter(2);}
 
  virtual float GetPostT0()  const override {
    float fitPostT0 =  GetWrapperTF1()->GetParameter(8);
 
    // Correct the time to the maximum
    //
    fitPostT0 += m_timeCorr;
 
    return fitPostT0;
  }
  virtual float GetPostAmp() const override {return GetWrapperTF1()->GetParameter(7);}
 
  virtual float GetExpAmp() const override {return GetWrapperTF1()->GetParameter(6);}
 
  virtual float GetTime() const override {
    return GetWrapperTF1()->GetParameter(1) + m_timeCorr; // Correct the time to the maximum
  }
 
  virtual unsigned int GetNumShapeParameters() const override {return 5;}
    
  virtual float GetShapeParameter(size_t index) const override
  {
    if (index <  5) return GetWrapperTF1()->GetParameter(index + 4);
    else throw std::runtime_error("Fit parameter does not exist.");
  }
 
  virtual float GetBkgdMaxFraction() const override
  {
    const TF1* theTF1 = ZDCFitWrapper::GetWrapperTF1();
 
    double maxTime = GetTime();
 
    double amp    = theTF1->GetParameter(0);
    if (amp <= 0) return -1;
    double preAmp = theTF1->GetParameter(2);
    double preT0  = theTF1->GetParameter(3);
    double slope  = theTF1->GetParameter(4);
 
    double deltaTPre = maxTime - preT0;
 
    double background = slope * maxTime + preAmp * m_norm * (m_expFermiFunc->operator()(deltaTPre) -
                        m_expFermiFunc->operator()(-preT0));
 
    return background / amp;
  }
 
  virtual double operator() (const double *x, const double *p) override
  {
    double t = x[0];
 
    double amp      = p[0];
    double t0       = p[1];
    double preAmp   = p[2];
    double preT0    = p[3];
    double linSlope = p[4];
    double linConst = p[5];
    double expamp   = p[6];
    double postAmp  = p[7];
    double postT0   = p[8];
 
    double deltaT     = t - t0;
    double deltaTPre  = t - preT0;
    double deltaTPost = t - postT0;
 
    // We subtract off the  value of the pre-pulse at the minimum time (nominally 0,
    //   but can change if we exclude early samples) to account for the subtraction of the pre-sample
    //
    double deltaPresamp = GetTMinAdjust() - preT0;
 
    double pulse1 =  amp     * m_norm *  m_expFermiFunc->operator()(deltaT);
    double pulse2 =  preAmp  * m_norm * (m_expFermiFunc->operator()(deltaTPre) - m_expFermiFunc->operator()(deltaPresamp));
    double pulse3 =  postAmp * m_norm *  m_expFermiFunc->operator()(deltaTPost);
 
    double linBG = linSlope * t + linConst;
    double expBG = expamp * std::exp(-(t) / m_tau2) - expamp * std::exp(-(GetTMinAdjust()) / m_tau2);  // deltaPresamp
 
    return pulse1 + pulse2 + pulse3 + linBG + expBG;
  }
};
 
double ZDCFermiExpFit(const double* xvec, const double* pvec)
{
  double t = xvec[0];
 
  double amp = pvec[0];
  double t0 = pvec[1];
  double tau1 = pvec[2];
  double tau2 = pvec[3];
  double C = pvec[4];
 
  double tauRatio = tau2 / tau1;
  double tauRatioMinunsOne = tauRatio - 1;
 
  double norm = (std::pow(1. / tauRatioMinunsOne, 1. / (1 + tauRatio)) /
         ( 1 + std::pow(1. / tauRatioMinunsOne, 1. / (1 + 1 / tauRatio))));
 
  double deltaT = t - t0;
  if (deltaT < 0) deltaT = 0;
 
  double expTerm = std::exp(-deltaT / tau2);
  double fermiTerm = 1. / (1. + std::exp(-(t - t0) / tau1));
 
  return amp * expTerm * fermiTerm / norm + C; 
}
 
double ZDCFermiExpFitRefl(const double* xvec, const double* pvec)
{
  double t = xvec[0];
 
  double amp = pvec[0];
  double t0 = pvec[1];
  double tau1 = pvec[2];
  double tau2 = pvec[3];
  double C = pvec[4];
  
  double refldelay = pvec[5];
  double reflFrac = pvec[6];
  double reflwidth = pvec[7];
  double delta = pvec[8];
  
  double tauRatio = tau2 / tau1;
  double tauRatioMinunsOne = tauRatio - 1;
 
  double norm = std::pow(1. / tauRatioMinunsOne, 1. / (1 + tauRatio)) /
    ( 1 + std::pow(1. / tauRatioMinunsOne, 1. / (1 + 1 / tauRatio))) ;
 
  double deltaT = t - t0;
  if (deltaT < 0) deltaT = 0;
 
  // Note: the small constant added here accounts for the very long tail on the pulse 
  //   which doesn't go to zero over the time range that we sample
  //
  double expTerm = delta + std::exp(-deltaT / tau2);
  double fermiTerm = 1. / (1. + std::exp(-(t - t0) / tau1));
 
  double deltaTRefl = deltaT - refldelay;
  double reflTerm =  -reflFrac*amp*std::exp(-0.5*deltaTRefl*deltaTRefl/reflwidth/reflwidth);
 
  return amp * expTerm * fermiTerm / norm + C + reflTerm; 
}
 
double ZDCFermiExpFitInduct(const double* xvec, const double* pvec)
{
  double t = xvec[0];
 
  double amp = pvec[0];
  double t0 = pvec[1];
  double tau1 = pvec[2];
  double tau2 = pvec[3];
  double C = pvec[4];
  
  double period = pvec[5];
  double Acos = pvec[6];
  double Bsin = pvec[7];
  double delta = pvec[8];
  
  double tauRatio = tau2 / tau1;
  double tauRatioMinunsOne = tauRatio - 1;
 
  double norm = std::pow(1. / tauRatioMinunsOne, 1. / (1.0 + tauRatio)) /
    ( 1.0 + std::pow(1. / tauRatioMinunsOne, 1. / (1.0 + 1.0 / tauRatio))) ;
 
  double deltaT = t - t0;
  double deltaTInduct = deltaT - tau1 * std::log(tauRatioMinunsOne);
  
  if (deltaT < 0) deltaT = 0;
  if (deltaTInduct < 0) deltaTInduct = 0;
    
  //  Note: the small constant added here accounts for the very long tail on the pulse 
  //  which doesn't go to zero over the time range that we sample
  
  double twoPiOverPeriod = 2.0*M_PI/period;
  double inductTerm = (1.0 + Acos*std::cos(deltaTInduct*twoPiOverPeriod) +
               Bsin*std::sin(deltaTInduct*twoPiOverPeriod))/(1+Acos);
  double expTerm = delta + std::exp(-deltaT / tau2)*inductTerm;
  double fermiTerm = 1. / (1. + std::exp(-(t - t0) / tau1));
 
  return amp * expTerm * fermiTerm / norm + C; 
}
 
#endif