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/formfactors_A_piZero_proton [ Modules ]

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NAME

module formfactors_A_piZero_proton

PURPOSE

This module reads in the form factors for gamma* N -> N pi out of text files and includes modules to return the form factors as functions of theta, s and Q^2.

For the isospin channel gamma p -> p pi^0.

INPUTS

None


formfactors_A_piZero_proton/getA [ Functions ]

[ Top ] [ formfactors_A_piZero_proton ] [ Functions ]

NAME

function getA(thetaIn,sIn,QSquaredIn)

PURPOSE

This function returns the invariant Amplitudes A_1, ... A_6 of the MAID analysis.

INPUTS

  • real :: thetaIn ! Theta scattering angle of the pion relative to q in the CM system of the hadronic vertex
  • real :: QSquaredIn ! Q^2=-q^mu q_mu of the gamma
  • real :: sIn ! Mandelstam s of the hadronic vertex: gamma* N-> pi N

OUTPUT

complex, dimension(1:6) :: getA ! The complex amplitudes A_1 to A_6 in units of:

  • [GeV**-2] for A(1)
  • [GeV**-4] for A(2) and A(5)
  • [GeV**-3] for A(3), A(4) and A(5)


getA/get_i [ Functions ]

[ Top ] [ getA ] [ Functions ]

NAME

integer function get_i(tin,Win,Qin,int_nint_switch)

PURPOSE

Evaluates index which corresponds to the grid point which lies closest to the input values:

  • For int_nint_switch=.false. it's the overall closest point
  • For int_nint_switch=.true. it's the closest point which is also in all dimensions closer to 0 than the input point.


getA/get_neighbors [ Functions ]

[ Top ] [ getA ] [ Functions ]

NAME

function get_neighbors(tin,Win,Qin)

PURPOSE

Returns the eight grid points which are defining the smallest cube in which the input point (tin,win,Qin) can be locked into. These are the neighboring grid-points of our input point.

OUTPUT

integer,dimension(1:8) :: get_neighbors


getA/init_datFile [ Functions ]

[ Top ] [ getA ] [ Functions ]

NAME

subroutine init_datFile

PURPOSE

Reads in the MAID input file, writes into FF_A.dat the control output. It expects an input file with the following format:

  • first some comment lines (doesn't matter how many)
  • Data lines with the following order : W, ThetaCM , Q^2 ,s ,t, Re(A_1), Im(A_1),...Re(A_6), Im(A_6)

The loop structure to generate this input file should be :

  • thetaCM-Loop, W-Loop, Q^2-Loop

OUPTUT Initializes the fields:

  • complex, save , dimension(:,:), Allocatable :: A
  • real, save , dimension(:) , Allocatable :: W, theta, Q2, s, t
  • real,save :: W_max, theta_max, q2_max ! maximaal values for W,theta,q^2
  • real, save :: dW,dTheta,dQ2 ! steps size for W,theta,q^2
  • integer, save :: numSteps_q,numSteps_t,numSteps_w ! number of different values for q^2,theta, w