Friends --

  my apologies, I have been quite sick for several days.  (It does seem 
that when members of our Rome/UW group become ill, we do not do so 
lightly; let us hope that our results will have corresponding gravitas.)

   I have selected four parameter points for preliminary discussion, with
emphasis on triggering challenges.

The first I will call the classic.

mzprime = 2 TeV
mpi = 30 GeV,
pizero lifetime= 100 ps,
piplus lifetime= infinity

Note the Z' mass is not 3 TeV! The lower Z' mass allows a larger cross 
section (or order 10 fb) for the same pizero lifetime, and also gives 
lower energy events with softer jets and less MET, for which the trigger 
may be more challenged.  I think the issues of non-pointing clusters,
muons which do not point back, etc, will already arise in this case.

The second I will call the anemic

mZprime = 2 TeV
mpi = 20 GeV
pizero lifetime = 5 ns
piplus lifetime = infinity

Again the cross-section is of order 10 fb.
This will be very challenging!!  The hard vpions escape the detector;
the ones in the detector are mostly soft.  Maybe this choice of
parameters is too difficult; let's see.

The third I will call the midrange

mzprime = 3 TeV
mpi = 60 GeV
pizero lifetime = 5 ps
piplus lifetime = infinity

Here triggering should be straightforward, with everything pointing back 
to the primary vertex to a good approximation; if not, that's important to 
know. Indeed many of the vertices are near or inside the beampipe and 
should be rather easy to find.

The fourth I will call the unstable-piplus

mzprime = 3 TeV
mpi = 150 GeV
pizero lifetime = 10 fs
piplus lifetime = 100 ps

Here we will have much less MET, many more jets, and a very
busy environment in which to find the vertices, which now
have large opening angles.  I have no idea what will happen here.

************

Let me point out a case which does not arise in the simplest models.
You might be interested in
mzprime = 3 TeV
mpi = 150 GeV
pizero lifetime = 100 ps
piplus lifetime = infinity

similar to the previous case, but with more MET and less activity, and 
with large opening angles for the highly-displaced vertices.  This case 
does not occur in the simplest models.  This is simple to understand: the 
higher mass of the vpizero increases the phase space for its decay, and 
the only way to make it long-lived is to increase the mass of the Z', 
which then means there's no v-quark production rate.

However, one *can* have this kind of scenario if the vpions are produced 
in decays of an LSP; in that case, the Z', which mediates the vpion 
decays, could be 10-100 TeV in mass.  And there are other scenarios too 
that I'm sure I can cook up with a little effort. So you might want to 
study this case at some point, even though the current event generator 
would be giving you an unrealistic model.

*************

Again, this is preliminary; comments welcome, and I will set up a website 
with a table of these choices, and make checks on all the numbers, on 
Friday.  I will also try to add to the event generator an estimator of the 
cross-sections involved with any given model.

Matt




Matthew Strassler		Associate Professor
Department of Physics		Office: B403 Physics-Astronomy Building
University of Washington	Phone: 206-616-9649  Fax: 206-616-9172
PO Box 351560			Email: strassler@phys.washington.edu
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http://www.phys.washington.edu/~strasslr