Hadron Scattering
A simple hadron scattering model. It is intended to take into account
that the overlap of multiple strings at low transverse dimensions
is likely to lead to some collective effects, not unlike those
observed in heavy-ion collisions, even if not quite as pronounced.
Specifically, it is assumed that the hadrons produced can scatter
against each other on the way out, before the fragmenting system
has had time to expand enough that the hadrons get free. Thereby
heavier particles are shifted to higher transverse momenta, at the
expense of the lighter ones.
Warning: This is still at an experimental level,
and should not be used unless you know what you are doing.
flag HadronScatter:scatter
(default = off)
Master flag for hadron scattering.
flag HadronScatter:afterDecay
(default = off)
Perform hadron scattering before or after first round of decays,
involving very short-lived particles like the rho.
The default is to perform scattering directly after the
string fragmentation, before any decays.
flag HadronScatter:allowDecayProd
(default = off)
Allow two hadrons with same parent hadron to scatter.
flag HadronScatter:scatterRepeat
(default = off)
Allow hadrons which have already scattered to scatter again.
Even if switched on, the same pair can not scatter off each
other twice.
Hadron selection
mode HadronScatter:hadronSelect
(default = 0; minimum = 0; maximum = 0)
Probability that a hadron is soft enough to scatter.
(A high-pT hadron presumably being part of a jet,
and thus produced away from the high-particle-density region
at small transverse dimensions.)
option 0 :
P = N exp(-pT^2 / 2 / sigma^2) /
( (1 - k) exp(-pT^2 / 2 / sigma^2) + k pT0^p / (pT0^2 + pT^2)^(p/2),
with sigma = 2 StringPT:sigma and pT0 the same as that
used in MultipartonInteractions.
parm HadronScatter:N
(default = 1.0; minimum = 0.01; maximum = 1.0)
N parameter as above.
parm HadronScatter:k
(default = 1.0; minimum = 0.01; maximum = 1.0)
k parameter as above.
parm HadronScatter:p
(default = 6; minimum = 2; maximum = 30)
p parameter as above.
Scattering probability
mode HadronScatter:scatterProb
(default = 0; minimum = 0; maximum = 2)
Probability for a pair of hadrons to scatter.
option 0 : All hadrons scatter with probability
j max(0, 1 - dR^2 / rMax^2). Angular distribution
is picked flat in cos(theta).
option 1 : As option 0, above, but only pi-pi,
pi-K and pi-p scatterings are considered.
option 2 : Only pi-pi, pi-K and
pi-p scatterings are considered, with probability
given by (1 - exp(-j sigEl)) max(0, 1 - dR^2 / rMax^2).
The elastic cross sections and angular distributions are taken
from the partial-wave distributions.
parm HadronScatter:j
(default = 0.5; minimum = 0.0; maximum = 10.0)
j parameter as above.
parm HadronScatter:rMax
(default = 0.5; minimum = 0.1; maximum = 2.0)
rMax parameter as above.
flag HadronScatter:tile
(default = off)
Use tiling in (eta, phi) to reduce number of pairwise tests.