FLUKA: 15} Special source: colliding beams
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15} Special source: colliding beams
Colliding beams as a source can be specified via command SPECSOUR and SDUM
equal to 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 2nd beam
(GeV/c)
WHAT(5)
= lab momentum y-component for protons or nuclei of the 2nd beam
(GeV/c)
WHAT(6)
= lab momentum z-component for protons or nuclei of the 2nd 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: 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 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 (only needed if the second is a heavy ion beam):
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_th_C 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_th_O 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_th_C 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_th_O 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
i0 + i1 * 10 + i2 * 100
0 = default, nuclear nonelastic + EMD if selected with the physics
card
otherwise:
i0 = flag for nuclear nonelastic interactions
i1 = flag for nuclear elastic interactions
i2 = 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
: not used
First and second continuation cards: as for SDUM
= PPSOURCE (see above)
For SDUM
= CROSSSYM (symmetric crossing):
First card:
WHAT(1)
= lab momentum for 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:
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.
4) The particles produced in the interaction of two beams have generation
number 1 (i.e., they are considered as primary particles)
5) All the scores in a run where the source consists of two colliding beams
are normalised per beam interaction
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