LumiFast

class description - source file

class LumiFast

    protected:

      float abs(float a)
      float Eres(float energy)

    public:

       LumiFast LumiFast()
           void ~LumiFast()
          float GetBdl()
          float GetBeta()
          float GetEnergyDn()
          float GetEnergyGam()
          float GetEnergyGamTrue()
          float GetEnergyTrueDn()
          float GetEnergyTrueUp()
          float GetEnergyUp()
          float GetERes()
          float GetEScaleDn()
          float GetEScaleUp()
          float GetEWindowMax()
          float GetEWindowMin()
      GenGamma* GetGenerator()
          float GetPosRes()
           TF1* GetThetaDist()
          float GetXMax()
          float GetXMin()
          float GetXOffset()
          float GetXPosDn()
          float GetXPosGam()
          float GetXPosGamTrue()
          float GetXPosUp()
          float GetYMaxDn()
          float GetYMaxUp()
          float GetYMinDn()
          float GetYMinUp()
          float GetYOffset()
          float GetYPosDn()
          float GetYPosGam()
          float GetYPosGamTrue()
          float GetYPosUp()
          float GetZ()
          float GetZMagnet()
          float GetZSpectro()
          float GetZTrue()
            int IsCoincidence()
            int IsHitDn()
            int IsHitUp()
           void NewEvent()
           void ProcessEvent()
           void SetBdl(float new_bdl)
           void SetBeta(float beta)
           void SetEnergyLoss(int isloss)
           void SetEnergyRes(float neweres)
           void SetEScaleDn(float new_escale)
           void SetEScaleUp(float new_escale)
           void SetEWindow(float Emin, float Emax)
           void SetEWindowMax(float Emax)
           void SetEWindowMin(float Emin)
           void SetGenerator(GenGamma* generator)
           void SetNyStripsDn(int nstrips)
           void SetNyStripsUp(int nstrips)
           void SetPosRes(float newres)
           void SetScattering(int iscat)
           void SetXOffset(float new_offset)
           void SetYOffset(float new_offset)
           void Show()

Data Members

    private:

          float fBdl           Integral BdL
          float fysep          separation of to calorimeters
          float fyoffset       offset of the spectrometer
          float fxoffset       offset of the spectrometer
            int fnxstrips      number of fiducial x strips 
            int fnystrips_up   number of fiducial y strips up
            int fnystrips_dn   number of fiducial y strips dn
          float fxmax          assume symmetric and same for both detectors
          float fzmagnet       z-position of magnet
          float fzspectro      z-position of spectrometer 
            int fIsScattering  switch on/off the scattering
            int fIsEnergyLoss  switch on/off the energy loss in the window
          float fEwindowMin    
          float fEwindowMax    
          float fEnergy_res    Energy resolution
          float fPos_res       Position resolution
          float fEscale_up     relative energy scale (e.g. 1.=true energy)
          float fEscale_dn     
          float fEnergy_e      electron energy
          float fEnergy_p      positron energy
          float fxpos_gam      photon hit position
          float fypos_gam      
          float fEnergy_up     
          float fEnergy_dn     
          float fypos_up       
          float fxpos_up       
          float fypos_dn       
          float fxpos_dn       
           TF1* fThetaDist     
      GenGamma* fGenerator     
      GenGamma* fGenInternal   default generator

Class Description

This is a class for fast simulation of the Luminosity Spectrometer for ZEUS. It contains generation of the photons and passing them through the detector and then parameterizing the physics processes and the detector simulation. Photon generation and the physics of the window is contained in the class GenGamma. This is set to the LumiFast through data member rather then by inheritance so that the effects of the same event for different detector settings can be studied.

The simulation steps are:

In the class GenGamma:

Generate photon with energy according to Bethe-Heitler or custom defined spectrum.
Generate photon position according to Gaussian beam profile or custom provided one.
Generate the splitting of photon into e+e- pair. The energy splitting is generated according to GEANT long writeup.
Generate energy loss in the window.

For he details on how to set the photon generator look at its class GenGamma.

In the class LumiFast:

Generate the opening angle/multiple coulomb scattering. This has been parameterized according to GEANT simulation.
True positions of hits in the spectrometer are calculated by knowing the true position in the window, the energies of the e+e- and the magnetic field. Positions are the smeared by the Gaussian. The position resolution can be set by SetPosRes(float resolution).
Energies are smeared according to the resolution of the calorimeters. Energy resolution = const sqrt(Energy) where constant can be set by SetEnergyRes(float resolution).

How to set the simulation up:

Processes for scattering can be switched on/off via SetScattering(0) or SetScattering(1) respectively. The radiation is controlled by SetRadiation() function.
Integral Bdl is controlled by the function SetBdl(float Bdl) and GetBdl(). The functions GetBeta() and SetBeta(float beta) are provided, where Beta = 0.3 Bdl L(magnet to spectro) with the simplification of formula vertical deflection = Beta/Energy
The position of the spectrometer is fixed up to the relative offset which can be adjusted by calling functions SetXOffset(float xoffset) and SetYOffset(float yoffset).
The fiducial volume starts one strip deep inside the calorimeter. This means there are 9 fiducial strips for LSD Up and 13 strips for LSD Dn. To set the option for running with the symmetric spectrometer call SetNyStripsDn(9).
The information about the event can be retreived by e.g GetXPosUp(), GetXPosDn(), GetEnergyUp(),GetEnergyDn() etc... The reconstructed hit information is also available through call to e.g. GetXPosGam() for the photon hit or GetZ() for reconstructed z = Ee/Egamma.
One should always check if the hit was reconstructed inside the detector by looking at IsHitUp() and IsHitDn() methods. The IsCoincidence() method checks fro the energy window as well. Window can be set by SetEWindow(float Emin,float Emax).

How to use the class:

First of all instantiate it Lumifast *lf = new LumiFast(). This also sets the default values for the parameters. Photon generator is initialized automatically.
Set the initial parameters. (e.g. geometry, energy scales, magnetic field, switch off the scattering etc..)
The new event is generate after calling NewEvent() method. If we want to process the same event from photon generator then call only ProcessEvent() method
Get the information you need and fill the histograms.
Look at the simple example macro.

Inline Functions

            float Eres(float energy)
            float abs(float a)
         LumiFast LumiFast()
             void ~LumiFast()
            float GetYMinUp()
            float GetYMaxUp()
            float GetYMinDn()
            float GetYMaxDn()
            float GetXMax()
            float GetXMin()
            float GetYOffset()
            float GetXOffset()
            float GetBdl()
            float GetZMagnet()
            float GetZSpectro()
            float GetBeta()
             void SetBeta(float beta)
            float GetERes()
            float GetPosRes()
            float GetEScaleUp()
            float GetEScaleDn()
            float GetEnergyTrueUp()
            float GetEnergyTrueDn()
            float GetEnergyGamTrue()
            float GetXPosGamTrue()
            float GetYPosGamTrue()
            float GetZTrue()
            float GetEnergyUp()
            float GetEnergyDn()
            float GetYPosUp()
            float GetXPosUp()
            float GetYPosDn()
            float GetXPosDn()
            float GetZ()
            float GetXPosGam()
            float GetYPosGam()
            float GetEnergyGam()
            float GetEWindowMin()
            float GetEWindowMax()
        GenGamma* GetGenerator()
             TF1* GetThetaDist()
             void SetBdl(float new_bdl)
             void SetEScaleUp(float new_escale)
             void SetEScaleDn(float new_escale)
             void SetEWindowMin(float Emin)
             void SetEWindowMax(float Emax)
             void SetEWindow(float Emin, float Emax)
             void SetScattering(int iscat)
             void SetEnergyLoss(int isloss)
             void SetPosRes(float newres)
             void SetEnergyRes(float neweres)
             void SetYOffset(float new_offset)
             void SetXOffset(float new_offset)
             void SetNyStripsUp(int nstrips)
             void SetNyStripsDn(int nstrips)
             void SetGenerator(GenGamma* generator)
             void NewEvent()
             void ProcessEvent()
              int IsCoincidence()
              int IsHitUp()
              int IsHitDn()
             void Show()

Last update: Mon Nov 26 13:21:16 2001

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