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/barBar_barBarMes [ Modules ]

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NAME

module barBar_barBarMes

PURPOSE

This module implements the calculation of baryon baryon -> baryon baryon meson cross sections.

barBar_barBarMes/NNpi [ Global module-variables ]

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SOURCE

  logical, save :: NNpi = .true.

PURPOSE

Global switch for the N N -> N N pi contibution

barBar_barBarMes/NNpi_BG [ Global module-variables ]

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SOURCE

  integer, save :: NNpi_BG = 2

PURPOSE

Switch for the N N -> N N pi background (s-channel):

  • 0 = no BG
  • 1 = BG according to Teis
  • 2 = BG according to Buss (improves threshold behavior, default)
  • 3 = BG according to Weil

barBar_barBarMes/NNV_BG [ Global module-variables ]

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SOURCE

  logical, save :: NNV_BG = .true.

PURPOSE

Incude a N N -> N N V background term, where V=omega,phi (in addition to possible resonance contributions).

barBar_barBarMes/isofac_omega [ Global module-variables ]

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SOURCE

  real, save :: isofac_omega = 1.

PURPOSE

Isospin enhancement factor for p n -> p n omega, relative to p p -> p p omega. Data indicate that this is around 2, while theory predicts even larger values (up to 5). Reference: Barsov et al., EPJ A21 (2004) 521-527.

barBar_barBarMes/isofac_phi [ Global module-variables ]

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SOURCE

  real, save :: isofac_phi = 1.

PURPOSE

Isospin enhancement factor for p n -> p n phi, relative to p p -> p p phi. Theory predicts values of 3-4, cf.: Kaptari, Kaempfer, Eur.Phys.J. A23 (2005) 291-304.

barBar_barBarMes/barBar_barBarMes [ Namelists ]

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NAME

NAMELIST barBar_barBarMes

PURPOSE

Includes the switches:

barBar_barBarMes/NN_NNpi_direct [ Functions ]

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NAME

function NN_NNpi_direct(srtfree, bg) result(Sigma_NNPion)

PURPOSE

Returns the background contributions to NN-> NN pion (via non-propagated resonances, plus non-resonant part).

It contain the following channels:

  • 1: p p -> p p pi^0 ; which is equivalent to n n -> n n pi^0
  • 2: p n -> n n pi^+ ; which is equivalent to p n -> p p pi^-
  • 3: p n -> p n pi^0 ;
  • 4: p p -> p n pi^+ ; which is equivalent to n n -> p n pi^-

INPUTS

  • real :: srtfree --- sqrt(s) in GeV

OUTPUT

  • real, dimension (1:4) :: Sigma_NNPion --- cross sections in mB

barBar_barBarMes/Np_NRplus_NNPion [ Subroutines ]

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NAME

subroutine Np_NRplus_NNPion(srtS, background, ch, sigmaDelta, sigma1_2, sigma3_2)

PURPOSE

Evaluates the cross sections for N p -> N Resonance(+) -> N N pion with vacuum assumptions. It returns the cross sections sigma1_2, which is summed over all I=1/2 resonances in the intermediate state, and sigma3_2, which is summed over all I=3/2 resonances in the intermediate state.

INPUTS

  • real :: srts -- sqrt(s)
  • logical :: background -- .true. : do not consider any propagated resonances, therefore the background contribution is returned; .false. : Consider all resonances, therefore the full resonance contribution is returned
  • integer :: ch -- charge of incoming nucleon

OUTPUT

  • real :: sigmaDelta -- cross section contribution of Delta
  • real :: sigma1_2 -- cross section summed over all I=1/2 resonances
  • real :: sigma3_2 -- cross section summed over all I=3/2 resonances (except the Delta)

barBar_barBarMes/sstatepi [ Functions ]

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NAME

function sstatepi(srts, choice) result(sigma)

PURPOSE

Function for calculation of N N -> N N pi background (non-resonant), for the following channels:

  • 1: p p -> p p pi0
  • 2: p n -> n n pi+ = p n -> p p pi-
  • 3: p n -> p n pi0
  • 4: p p -> p n pi+

INPUTS

  • real, intent(in) :: srts --- sqrt(s)
  • integer, intent(in), optional :: choice --- choice of parametrization: 1=Teis,2=Buss,3=Weil; if not given, the value is taken from the namelist switch 'NNpi_BG'

OUTPUT

  • real :: sigma(4)

barBar_barBarMes/sig_NNV [ Functions ]

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NAME

real function sig_NNV(srts, charge_in)

PURPOSE

Calculates cross sections for:

  • N N -> N N omega
  • N N -> N N phi
  • N N -> N N pi omega

in mb as function of sqrt(s), according to the parametrization (eq. 15) from Sibirtsev, Nucl. Phys. A 604 (1996) 455.

INPUTS

  • real, intent(in) :: srts --- sqrt(s) in GeV
  • integer, intent(in) :: charge_in --- total incoming charge (2=pp, 1=pn, 0=nn)

OUTPUT

  • real :: sig(1:3) --- cross section in mb for the three channels

NOTE The parameters for channel (1) have been taken from Sibirtsev. The first parameter 'a' has been updated slightly by M. Abdel-Bary et al., Phys. Lett. B 647 (2007) 351. The parameters for channel (2) are from E.Ya. Paryev, J.Phys.G G36 (2009) 015103. The parameters for the third channel have been fitted to results of Pythia 6.4.25 (tuned).

barBar_barBarMes/chooseCharge_NNpiomega [ Functions ]

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NAME

subroutine chooseCharge_NNpiomega(chIn, chOut)

PURPOSE

Choose final state charges for N N -> N N pi omega, using Clebsch-Gordan factors which assume the pion is produced via a Delta.

INPUTS

  • integer, dimension(1:2) :: chIn --- initial state charges (N,N)

OUTPUT

  • integer, dimension(1:3) :: chOut --- final state charges (N,N,pi)