Special source: colliding beams¶

Colliding beams as a source can be specified via command SPECSOUR and SDUM = PPSOURCE or ppsource, CROSSASY or CROSSSYM.

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 or nuclei of the first beam (GeV/c)
WHAT(2) =: lab momentum y-component for hadrons or nuclei of the first beam (GeV/c)
WHAT(3) =: lab momentum z-component for hadrons or nuclei of the first beam (GeV/c)
WHAT(4) =: lab momentum x-component for protons or nuclei of the second beam (GeV/c)
WHAT(5) =: lab momentum y-component for protons or nuclei of the second beam (GeV/c)
WHAT(6) =: lab momentum z-component for protons or nuclei of the second beam (GeV/c)
SDUM: : PPSOURCE or ppsource

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
≤ 0.0:: 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
= 0.0:: it is a proton beam, and WHAT(1) of 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) :

specifies the divergence of the first beam in the crossing plane (in rad):

$\sigma_{thC}$ for the Gaussian sampling of the angle between the direction of the particle and the most probable direction as defined by WHAT(1–3) of the first card

WHAT(3) :

specifies the divergence of the first beam in the orthogonal plane (in rad):

$\sigma_{thO}$ for the Gaussian sampling of the angle between the direction of the particle and the most probable direction as defined by WHAT(1–3) of the first card

WHAT(4) :

specifies the divergence of the second beam in the crossing plane (in rad):

$\sigma_{thC}$ for the Gaussian sampling of the angle between the direction of the particle and the most probable direction as defined by WHAT(4–6) of the first card

WHAT(5) :

specifies the divergence of the second beam in the orthogonal plane (in rad):

$\sigma_{thO}$ for the Gaussian sampling of the angle between the direction of the particle and the most probable direction as defined by WHAT(4–6) of the first card

WHAT(6) :

flag for interactions to be sampled: $i_0 + i_1 \cdot 10 + i_2 \cdot 100$

= 0: default, nuclear nonelastic + EMD if selected with the physics card

otherwise:

= $i_0$: flag for nuclear nonelastic interactions

= $i_1$: flag for nuclear elastic interactions

= $i_2$: flag for electromagnetic dissociation interactions

SDUM

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

For SDUM = CROSSASY (asymmetric crossing):

First card:

WHAT(1) =: lab momentum of hadrons or nuclei of the first beam (GeV/c)
WHAT(2) =: polar angle (rad) between the momentum of hadrons or nuclei 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 protons or nuclei of the second beam (GeV/c)
WHAT(5) =: polar angle (rad) between the momentum of protons or nuclei of the second beam and the -z (negative) direction (must be between 0 and $\pi/2$)
WHAT(6): : not used
SDUM: : CROSSASY or crossasy

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

For SDUM = CROSSSYM (symmetric crossing):

First card:

WHAT(1) =: lab momentum of protons or 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))
WHAT(4): – WHAT(6): not used

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

Notes

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.
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.
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.
The particles produced in the interaction of two beams have generation number 1 (i.e. they are considered as primary particles)
All the scores in a run where the source consists of two colliding beams are normalised per beam interaction