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/ParamEP [ Modules ]

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NAME

module ParamEP

PURPOSE

This module defines routines which return parametrizations of the electron proton cross section.

INPUTS

The Namelist "paramEP" in the Jobcard.

NOTES

At the moment we include the parametrizations:

  • F. W. Brasse et al., ``Parametrization Of The Q**2 Dependence Of Virtual Gamma P Total Cross-Sections In The Resonance Region,'' Nucl. Phys. B {\bf 110}, 413 (1976).
  • M. E. Christy and P. E. Bosted, ``Empirical Fit to Precision Inclusive Electron-Proton Cross Sections in the Resonance Region,'' Phys.Rev. C81 (2010) 055213

In addition, we also include here the the ALLM parametrization for high W values (W>1.75 GeV):

  • H. Abramowicz, E. M. Levin, A. Levy and U. Maor, ``A Parametrization of sigma-T (gamma* p) above the resonance region Q**2 >= 0,'' Phys. Lett. B {\bf 269} (1991) 465.

Here the authors claim, that this provides a smooth continuation of the parametrization by Brasse et al.. The newest version is also implemented:

  • H. Abramowicz and A. Levy, ``The ALLM parameterization of sigma(tot)(gamma* p): An update,'' arXiv:hep-ph/9712415.

We also provide the parametrizations for R=sigma_L/sigma_T by:


ParamEP/useParam [ Global module-variables ]

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SOURCE

  integer, save :: useParam = 2

PURPOSE

select, which parametrization to use:

  • 1: Brasse
  • 2: Bosted


ParamEP/initInput [ Subroutines ]

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NAME

subroutine initInput

PURPOSE

Reads in job card, checks the settings of the input parameters and also reads the data arrays


ParamEP/paramEP [ Namelists ]

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NAME

NAMELIST /paramEP/

PURPOSE

Namelist for module ParamEP includes:


ParamEP/CalcParamEP [ Subroutines ]

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NAME

subroutine CalcParamEP(W,Q2,eps, XS, XSerr)

PURPOSE

Calculate the XS (and its error) according the selected Parametrization

INPUTS

  • real :: W -- incoming photon (W)
  • real :: Q2 -- incoming photon (Q^2)
  • real :: eps -- incoming photon (epsilon)

OUTPUT

  • real :: XS -- cross section
  • real,OPTIONAL :: XSerr -- error


ParamEP/CalcParamEP_Brasse [ Subroutines ]

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NAME

subroutine CalcParamEP_Brasse(W,Q2,eps, XS, XSerr)

PURPOSE

Calculate the XS (and its error) according the Brasse Parametrization:

  • F.~W.~Brasse et al., ``Parametrization Of The Q**2 Dependence Of Virtual Gamma P Total Cross-Sections In The Resonance Region,'' Nucl. Phys. B {\bf 110}, 413 (1976)

INPUTS

  • real :: W -- incoming photon (W)
  • real :: Q2 -- incoming photon (Q^2)
  • real :: eps -- incoming photon (epsilon)

OUTPUT

  • real :: XS -- cross section
  • real,OPTIONAL :: XSerr -- error

NOTES

The range of validity is:

  • eps = 0...0.6...0.9...1.0
  • Q2 = 0 ... ??? GeV^2
  • W = 1.1 ... 2.0 GeV

The returned cross section is

    \sigma^* = \sigma_T+\epsilon\sigma_L
             = \frac{1}{\Gamma} \frac{d\sigma}{dE' d\Omega}

Unfortunately, the authors do not giv a definition of Gamma.

An interpolation between different W bins would smoothen the results.


ParamEP/Flux_Bosted [ Functions ]

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NAME

real function Flux_Bosted(W,Q2,eps)

PURPOSE

return the value of equation (4) in Phys.Rev. C81 (2010) 055213

Multiplying this return value with the value given by CalcParamEP_Bosted() yields

     \frac{d\sigma}{dE' d\Omega}

INPUTS

  • real :: W -- incoming photon (W)
  • real :: Q2 -- incoming photon (Q^2)
  • real :: eps -- incoming photon (epsilon)

OUTPUT

  • function value -- flux in 1/GeV


ParamEP/CalcParamEP_Bosted [ Subroutines ]

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NAME

subroutine CalcParamEP_Bosted(W,Q2,eps, XS)

PURPOSE

Calculate the XS according the Bosted Parametrization:

  • M. E. Christy and P. E. Bosted, ``Empirical Fit to Precision Inclusive Electron-Proton Cross Sections in the Resonance Region,'' Phys.Rev. C81 (2010) 055213

INPUTS

  • real :: W -- incoming photon (W)
  • real :: Q2 -- incoming photon (Q^2)
  • real :: eps -- incoming photon (epsilon)

OUTPUT

  • real :: XS -- cross section

NOTES

This is a wrapper function around code provided by P.Bosted.

The returned cross section is

    \sigma^* = \sigma_T+\epsilon\sigma_L
             = \frac{1}{\Gamma} \frac{d\sigma}{dE' d\Omega}

with

    \Gamma = \frac{\alpha E' (W^2-M^2)}{(2\pi)^2 Q^2 M E (1-\epsilon)}

The returned values are given in mub.

The range of validity is:

  • eps = 0...1.0
  • Q2 = 0 ... 10 GeV^2
  • W = 1.1 ... 3.0 GeV


ParamEP/CalcParamEP_ALLM [ Subroutines ]

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NAME

subroutine CalcParamEP_ALLM(W,Q2, XS)

PURPOSE

Calculate the XS according the ALLM Parametrization:

  • H. Abramowicz, E. M. Levin, A. Levy and U. Maor, ``A Parametrization of sigma-T (gamma* p) above the resonance region Q**2 >= 0,'' Phys. Lett. B {\bf 269} (1991) 465.

INPUTS

  • real :: W -- incoming photon (W)
  • real :: Q2 -- incoming photon (Q^2)

OUTPUT

  • real :: XS -- cross section (in mub)

NOTES

The range of validity is:

  • W > 1.75 GeV
  • Q2 = 0...2000GeV^2

This routine returns sigma_tot == sigma_L+sigma_T


ParamEP/CalcParamEP_ALLM97 [ Subroutines ]

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NAME

subroutine CalcParamEP_ALLM97(W,Q2, XS)

PURPOSE

Calculate the XS according the ALLM97 Parametrization:

  • H. Abramowicz and A. Levy, ``The ALLM parameterization of sigma(tot)(gamma* p): An update,'' arXiv:hep-ph/9712415.

INPUTS

  • real :: W -- incoming photon (W)
  • real :: Q2 -- incoming photon (Q^2)

OUTPUT

  • real :: XS -- cross section (in mub)

NOTES

The range of validity is:

  • W > sqrt(3) GeV
  • Q2 = 0...2000GeV^2

This routine returns sigma_tot == sigma_L+sigma_T


ParamEP/CalcParamEP_R1990 [ Subroutines ]

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NAME

subroutine CalcParamEP_R1990(W,Q2, R)

PURPOSE

Calculate R=sigma_L/sigma_T according:

  • L.W.Whitlow et al., ``A Precise extraction of R = sigma-L / sigma-T from a global analysis of the SLAC deep inelastic e p and e d scattering cross-sections,'' Phys.Lett.B250:193-198,1990.

NOTES

We corrected a typo in the constant b1 from the paper.