These are explained in the talks Rick gave on
October 4th at the MC workshop which is on his "talks" WEBsite at
http://www.phys.ufl.edu/~rfield/cdf/rdf_talks.html

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The four different PYTHIA tunings (all with CTEQ5L) are as
follows:

	Set A: Double Gaussian with more initial-state radiation
	Set B: Double Gaussian with less initial-state radiation
	Set C: Single Gaussian with more initial-state radiation
	Set D: Single Gaussian with less initial-state radiation

At version 6.138 PYTHIA changed its default value of PARP(67)
from 4.0 to 1.0.  The larger the value of PARP(67) the more 
initial-state radiation.  All of Run I had PARP(67)=4, but
if you run PYTHIA 6.2 you get PARP(67)=1.  My "underlying event"
studies (and Kevin Lannon's b-correlations) favor the old
value of PARP(67) (i.e. Set A and Set C), but it is interesting
to see how sensitive a given analysis is to the initial-state 
radiation.  Also, PARP(67)=4 might be a bit high. I am working 
on a tune in between 1 and 4.

Set A seems to be the best  "tune" so far since it does a good 
job on both the "underlying event" in hard scattering processes 
and on "min-bias" (same program).

To run "min-bias" and low PT jet production run CKIN(3)=0.0.
To get more statistice on high PT jets run CKIN(3) > 5.0 (do
not run in the range 0 < CKIN(3) < 5).

PARP(89)=E0 is a reference point and corresponds to the place
where the "tuning" was done.  It should be set fixed at 1800.
regardless of the CM energy (i.e. leave it at 1800. even when
you run at 1960.).

These "tunes" only work for CTEQ5L.

These "tunes" were arrived at by fitting the "underlying event" in
hard scattering processes.  I have not tuned for b-quark 
fragmentation... etc.  Fragmentation "tunes" could be added on top
of these "tunes".

If you are running heavy quark production (i.e. c or b) you must
fix the "bug" I found in PYTHIA (see below).

===============================================================
PYTHIA 6.206 Parameters (Set A):
c   Double Gaussian: old ISR setting with more initial-state radiation
c   Structure Functions (CTEQ5L)
	MSTP(51)=4046
	MSTP(52)=2
c
c To model HC+DD+SD+EL run MSEL=2
c To model the HC inelastic cross section run MSEL=1
	MSEL=1
c For min-bias and low pt jets run CKIN(3)=0
c For high PT jets run CKIN(3) > 5
	CKIN(3)=dble(0.0)
c
c  Initial-State Radiation Max Scale Factor
c  Old ISR setting with more initial-state radiation
	PARP(67)=dble(4.0)
c
c  Underlying Event Parameters
	MSTP(81)=1
c Single Gaussian
	MSTP(82)=4
c MPI Cut-Off
	PARP(82)=dble(2.0)
c  Warm-Core: 50% of matter in radius 0.4
	PARP(83)=dble(0.5)
	PARP(84)=dble(0.4)
c Almost Nearest Neighbor
	PARP(85)=dble(0.9)
	PARP(86)=dble(0.95)
c Energy Dependence with E0=1.8 TeV (do not vary this!)
	PARP(89)=dble(1800.0)
	PARP(90)=dble(0.25)
c
===============================================================
PYTHIA 6.206 Parameters (Set B):
c   Double Gaussian: old ISR setting with more initial-state radiation
c   Structure Functions (CTEQ5L)
	MSTP(51)=4046
	MSTP(52)=2
c
c To model HC+DD+SD+EL run MSEL=2
c To model the HC inelastic cross section run MSEL=1
	MSEL=1
c For min-bias and low pt jets run CKIN(3)=0
c For high PT jets run CKIN(3) > 5
	CKIN(3)=dble(0.0)
c
c  Initial-State Radiation Max Scale Factor
c  New ISR setting with less initial-state radiation
	PARP(67)=dble(1.0)
c
c  Underlying Event Parameters
	MSTP(81)=1
c Single Gaussian
	MSTP(82)=4
c MPI Cut-Off
	PARP(82)=dble(1.6)
c  Warm-Core: 50% of matter in radius 0.4
	PARP(83)=dble(0.5)
	PARP(84)=dble(0.4)
c Nearest Neighbor
	PARP(85)=dble(1.0)
	PARP(86)=dble(1.0)
c Energy Dependence with E0=1.8 TeV (do not vary this!)
	PARP(89)=dble(1800.0)
	PARP(90)=dble(0.25)
c
===============================================================
PYTHIA 6.206 Parameters (Set C):
c   Single Gaussian: old ISR setting with more initial-state radiation
c   Structure Functions (CTEQ5L)
	MSTP(51)=4046
	MSTP(52)=2
c
c To model HC+DD+SD+EL run MSEL=2
c To model the HC inelastic cross section run MSEL=1
	MSEL=1
c For min-bias and low pt jets run CKIN(3)=0
c For high PT jets run CKIN(3) > 5
	CKIN(3)=dble(0.0)
c
c  Initial-State Radiation Max Scale Factor
c  Old ISR setting with more initial-state radiation
	PARP(67)=dble(4.0)
c
c  Underlying Event Parameters
	MSTP(81)=1
c Single Gaussian
	MSTP(82)=3
c MPI Cut-Off
	PARP(82)=dble(1.7)
c Nearest Neighbor
	PARP(85)=dble(1.0)
	PARP(86)=dble(1.0)
c Energy Dependence with E0=1.8 TeV (do not vary this!)
	PARP(89)=dble(1800.0)
	PARP(90)=dble(0.25)
c
===============================================================
PYTHIA 6.206 Parameters (Set D):
c   Single Gaussian: new ISR setting with less initial-state radiation
c   Structure Functions (CTEQ5L)
	MSTP(51)=4046
	MSTP(52)=2
c
c To model HC+DD+SD+EL run MSEL=2
c To model the HC inelastic cross section run MSEL=1
	MSEL=1
c For min-bias and low pt jets run CKIN(3)=0
c For high PT jets run CKIN(3) > 5
	CKIN(3)=dble(0.0)
c
c  Initial-State Radiation Max Scale Factor
c  New ISR setting with less initial-state radiation
	PARP(67)=dble(1.0)
c
c  Underlying Event Parameters
	MSTP(81)=1
c Single Gaussian
	MSTP(82)=3
c MPI Cut-Off
	PARP(82)=dble(1.6)
c Nearest Neighbor
	PARP(85)=dble(1.0)
	PARP(86)=dble(1.0)
c Energy Dependence with E0=1.8 TeV (do not vary this!)
	PARP(89)=dble(1800.0)
	PARP(90)=dble(0.25)
c