15 Special source: colliding beams

One of the two colliding beams (from now on the "first beam") is a beam of hadrons (including protons or heavier nuclei), the other one (the "second beam") is a beam of protons or heavier nuclei but not of other hadrons. The different SDUM values allow to define the two beams in different ways. The first and the second continuation cards are identical for all SDUM options.

For SDUM = PPSOURCE or ppsource:

First card:

    WHAT(1) = lab momentum x-component for hadrons of the first beam (GeV/c)

    WHAT(2) = lab momentum y-component for hadrons of the first beam (GeV/c)

    WHAT(3) = lab momentum z-component for hadrons of the first beam (GeV/c)

    WHAT(4) = lab momentum x-component for nuclei of the the 2nd beam (GeV/c)

    WHAT(5) = lab momentum y-component for nuclei of the the 2nd beam (GeV/c)

    WHAT(6) = lab momentum z-component for nuclei of the the 2nd beam (GeV/c)

    SDUM:   not used

First continuation card:

    WHAT(1) = sigma_x (cm) for the Gaussian sampling of the interaction position
              around XBEAM (the x position defined in the BEAMPOSit card)

    WHAT(2) = sigma_y (cm) for the Gaussian sampling of the interaction position
              around YBEAM (the y position defined in the BEAMPOSit card)

    WHAT(3) = sigma_z (cm) for the Gaussian sampling of the interaction position
              around ZBEAM (the z position defined in the BEAMPOSit card)

    WHAT(4) = sampling limit, in sigma, applying along x, y, and z

            =< 0: ignored (no limit)

    WHAT(5) = particle id number (or corresponding name) of hadrons of the
              first beam
              Default: as defined by the BEAM card (and by the HI-PROPErt card
              in case it is a heavy ion)

    WHAT(6) = mass number of the nuclei of the second beam
            = 0: it is a proton beam, and the second continuation card
                 - if present - is ignored

    SDUM    = "&" in any position in column 71 to 78 (or in the last field if
              free format is used)

Second continuation card:

    WHAT(1) = atomic number of the nuclei of the second beam

    WHAT(2)-WHAT(6): not used

    SDUM    = "&&" in any position in column 71 to 78 (or in the last field if
              free format is used)

For SDUM = CROSSASY (crossing asymmetric):

First card:

    WHAT(1) = lab momentum of hadrons of the first beam (GeV/c)

    WHAT(2) = polar angle (rad) between the momentum of hadrons of the first
              beam and the z (positive) direction (must be between 0 and pi/2)

    WHAT(3) = azimuthal angle (deg) defining the crossing plane (see Note 2
              below)

    WHAT(4) = lab momentum of nuclei of the second beam (GeV/c)

    WHAT(5) = polar angle (rad) between the momentum of nuclei of the second
              beam and the -z (negative) direction (must be between 0 and pi/2)

    WHAT(6) = not used

    SDUM:   not used

First and second continuation cards: as for SDUM = PPSOURCE (see above) For SDUM = CROSSSYM (crossing symmetric):

First card:

    WHAT(1) = lab momentum for nuclei of both beams (GeV/c) (see Note 3)

    WHAT(2) = half crossing angle (rad) (must be between 0 and pi/2)

    WHAT(3) = azimuthal angle (deg) defining the crossing plane (see Note 2
              below)

    WHAT(4)-WHAT(6): not used

First and second continuation cards: as for SDUM = PPSOURCE (see above) Notes:

1) When SPECSOUR is used to define two colliding beams (SDUM = PPSOURCE, CROSSASY or CROSSSYM), DPMJET must be linked through the script $FLUPRO/flutil/ldpmqmd. A card PHYSICS with SDUM = LIMITS sets the maximum CMS momentum (GeV/c) in WHAT(1) for DPMJET initialization purposes.

2) With SDUM = CROSSASY and CROSSSYM, the half plane containing the two proton momenta at the sampled interaction point (XXX, YYY, ZZZ) is assumed to be limited by an axis z' passing through (XXX, YYY) and parallel to the z-axis. Polar and azimuthal angles are defined with

         respect to z', with WHAT(3) = 0 corresponding to the xz' half plane
         towards positive x, WHAT(3) = 90 corresponding to the yz' half plane
         towards positive y, WHAT(3) = 180 corresponding to the xz' half plane
         towards negative x, WHAT(3) = 270 corresponding to the yz' half plane
         towards negative y.

3) With SDUM = CROSSSYM, the particles of the two beams are identical and have the same momentum. They can only be protons or nuclei: other hadrons are excluded.

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