### TABLE OF CONTENTS

- 1. /photonXSections
- 1.1. photonXSections/iParam
- 1.2. photonXSections/omega_saphir
- 1.3. photonXSections/setIParam
- 1.4. photonXSections/readInput
- 1.5. photonXSections/photonXS
- 1.6. photonXSections/gammaN2VN_matrix
- 1.7. photonXSections/calcXS_gammaN2VN
- 1.8. photonXSections/calcXS_gammaN2VDelta
- 1.9. photonXSections/calcXS_gammaN2strange
- 1.10. photonXSections/calcXS_omega_saphir

## /photonXSections [ Modules ]

NAME

module **photonXSections**

PURPOSE

This module collects some routines for cross-section parametrizations for the photon-induced reactions (gamma+N).

## photonXSections/iParam [ Global module-variables ]

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SOURCE

integer, save ::iParam= 2

PURPOSE

Switch to select the kind of parametrization for gamma N -> V N:

- 1: "old parametrization", fit to experimental data, cf. Effenberger PhD, p.53
- 2: Pythia, cf. Friberg/Sjöstrand hep-ph/0007314
- 3: Donnachie, Landshoff [citation needed]

## photonXSections/omega_saphir [ Global module-variables ]

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SOURCE

` logical, save :: `**omega_saphir** = .true.

PURPOSE

If .true. an improved fit (to SAPHIR data) will be used for gamma N -> omega N. cf. "calcXS_omega_saphir"

## photonXSections/setIParam [ Subroutines ]

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NAME

subroutine **setIParam**(i,os)

PURPOSE

switching by hand between some parametrisations

INPUTS

- integer :: i -- new value of "iParam"
- integer, OPTIONAL :: os -- new value of "omega_saphir"

## photonXSections/readInput [ Subroutines ]

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NAME

subroutine **readInput**

PURPOSE

Reads input out of jobcard. Namelist 'photonXS'.

## photonXSections/photonXS [ Namelists ]

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NAME

NAMELIST **photonXS**

PURPOSE

Includes the parameters:

## photonXSections/gammaN2VN_matrix [ Subroutines ]

[ Top ] [ photonXSections ] [ Subroutines ]

NAME

subroutine **gammaN2VN_matrix**(srts,i,spot,matrix)

PURPOSE

Calculates squared matrix elements for gamma N -> V N with different parametrizations, cf. 'iParam'.

INPUTS

- real, intent(in) :: srts -- SQRT(s)
- integer, intent(in) :: i -- select vector meson V: 1=rho, 2=omega, 3=phi, 4=J/Psi
- real, intent(in) :: spot -- scalar potential for vector meson in final state

OUTPUT

NOTES

For rho, omega and phi this routine returns matrix elements, for J/Psi it directly returns the cross section.

The used coupling constants gV are not modified due to shadowing!

## photonXSections/calcXS_gammaN2VN [ Subroutines ]

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NAME

subroutine **calcXS_gammaN2VN**(srts,media,sig,sigi)

PURPOSE

Produces cross section for

gamma N -> V N

and

gamma N -> V pi N

INPUTS

OUTPUT

- real, dimension(1:4) :: sig -- cross section for gamma N -> (rho,omega,phi,JPsi) N
- real, dimension(1:4), OPTIONAL :: sigi -- cross section for gamma N -> (rho,omega,phi,JPsi) N Pion

NOTES

Returned cross sections are in microbarn.

## photonXSections/calcXS_gammaN2VDelta [ Subroutines ]

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NAME

subroutine **calcXS_gammaN2VDelta**(srts,sigi,media)

PURPOSE

Calculates the cross section for gamma N -> V Delta, where V is a vector meson.

INPUTS

OUTPUT

- real, dimension(1:4) :: sigi ! cross sections
- sigi(1) -> rho Delta
- sigi(2) -> omega Delta
- sigi(3) -> phi Delta
- sigi(4) -> JPsi Delta

NOTES

Units of cross sections: microbarn

## photonXSections/calcXS_gammaN2strange [ Subroutines ]

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NAME

subroutine **calcXS_gammaN2strange**(srts,sigma)

PURPOSE

Produces cross section for

gamma N -> Lambda K, Sigma K, N K Kbar

OUTPUT

- real, dimension(1:3 :: sigma ! cross section
- sigma(1) :: Lambda K
- sigma(2) :: Sigma K
- sigma(3) :: N K Kbar

NOTES

UNITS of cross sections????

## photonXSections/calcXS_omega_saphir [ Subroutines ]

[ Top ] [ photonXSections ] [ Subroutines ]

NAME

subroutine **calcXS_omega_saphir**(srts,cs)

PURPOSE

Calculates the cross section for gamma + N -> omega + N (fit to SAPHIR data). See P. Muehlich, diss., chapter 9.3.3. The data can be found in J.Barth, Eur. Phys. J. A18 (2003) 117-127

INPUTS

OUTPUT

- real,intent(out):: cs --- cross section in microbarn

NOTES

The matrix element for the process is tabulated in the file "gammaN_omegaN_ME_saphir.dat". It is computed from the (splined) SAPHIR cross sections.