LCFI Meeting 19/12/98

                   PHYSICS AND DETECTOR SIMULATIONS

                            Philip Burrows



DEVELOPMENTS ARISING FROM KEYSTONE AND FRASCATI WORKSHOPS:


1. European benchmark physics processes now defined (see DESY WWW pages)

   - supposed to be challenging to detector design

   - focus on these for Oxford Workshop (20-23 March 1999)
     and international workshop in Sitges (late April 1999)

   - not sure if US will adopt the same reactions; probably at least some

   - Japan still organising working groups


2. Detector/interaction region parameters:

   - renewed European interest in:

     beampipe radius (2 cm or 1cm?)

     detector solenoidal field: 3T or 4T?

     need for an intermediate tracker between VXD and main tracker

     forward tracking (have longer ladders in our design?)


3. VXD technologies:

   - maintained European interest in APS devices (Helsinki group)

   - US seems to have accepted CCDs: SLAC, Oregon, Berkeley


4. Detector simulation packages:

   - fast simulation of European detector - CCD VXD parametrised response in

   - ditto for US fast simulation (need to check CCD VXD is in)

   - work proceeds on detailed simulation: GEANT at DESY

                                           GISMO at SLAC (Object Oriented)

     as well as pattern recognition, track-fitting, etc. (!)

   - request to have flavour-tagging routines available for general use




           SUGGESTED PLAN FOR SIMULATIONS FOR OXFORD/SITGES

C. Bowdery, P. Burrows, D. Jackson, S. Menzel, A. Salter + ....?


Since time and manpower very limited, suggest a staged approach with realistic
goals:


A. FIRST STAGE

1. Use the parametrised impact-parameter response for the default 'Snowmass
detector', perhaps modified slightly in geometry eg. longer layers 2-5 to
provide improved polar-angle coverage - discuss this with Chris.

2. Generate jets of energy: 25, 50, 100, 200 GeV in standard e+e- --> hadrons
events

3. Apply the current SLD flavour-tagging package based on the ZVTOP algorithm

4. Generate the purity vs. efficiency curves as a function of jet energy and
jet polar-angle, for: b-jet, c-jet and uds-jet tagging.

5. Choose some standard tagging criteria (based on SLD 1998) and produce
b, c, uds efficiency and purity vs. jet energy and polar angle.
Provide simple parametrisations of these results.

These will provide a set of reference performance parameters of tagging
efficiency and purity that can be used by people doing any one of the
benchmark analyses. Eg. you need to know the efficiency for b-jet tagging
in process X, then read it off our curve for the typical b-jet energy of your
process.

6. We might also think about doing the above for tau-tagging, as there is
much interest now in H --> tau tau

7. For the standard tag, rerun some subset of results with the impact-parameter
response corresponding to:

i) a 2 cm beampipe

ii) a 1 cm beampipe but thicker CCDs - to be defined in discussions with Chris

iii) a 2cm beampipe and thick CCDs

these will help answer some of the questions about the desirability of a
small-radius beampipe.


B. SECOND STAGE

1. Choose a couple of challenging benchmark processes. I suggest:

e+e- --> H Z,  H --> b bbar, c cbar, tau tau

e+e- --> t tbar H, H --> b bbar

the second has received a lot of attention from a Spanish group, though with
very naive assumptions about b-jet tagging. It is now emerging as one of THE
most challenging benchmark processes that will push the luminosity and
detector requirements.

2. Generate events of these types and repeat stage A.


C. THIRD STAGE

We'll be lucky to get here by Sitges, but this might involve:

1. Running more benchmark processes

2. Investigating a more realistic detector simulation, eg. explicit hit
smearing in GEANT, and a parametrisation of the hit smearing folded into
the standard parametrised impact-parameter response.



*** ==> SEE PROGRESS REPORT FROM CHRIS BOWDERY!



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


                 INTEREST IN UK INVOLVEMENT IN ACCELERATORS


There is much interest in the UK getting involved in accelerator R+D again.
There was a meeting last month at RAL for interested people (I'm sure not
everyone who is interested was able to attend), organised by ken Peach and
Chris Batty. The outcome is 3 working groups looking at options for UK
involvement in:

1. Linear e+e- colliders

2. A muon collider and associated high-flux neutrino sources

3. Generic high-gradient accelerator R+D


Grahame Blair, Chris Damerell, Hywel Phillips and I agreed to form the first
one - EVERYONE INTERESTED is invited to join us! We're currently gathering
information on good projects at CERN, DESY and SLAC which might be well matched
to the likely level of UK effort (see below) and relevant UK expertise in both
the science community and industry.
For example: design and simulation of the interaction region and detector
interface, klystron development (Daresbury and EEV have expertise), positron
source and polarisation, precision energy spectrometer, etc etc.
If anyone has ideas, please let us know.

The likely level of UK funding for this effort is not yet clear, but the
CSR outcome for PPARC was of the wrong sign; we may be talking a few hundred
thousand pounds for each of the above areas - COMPLETELY UNOFFICIAL NUMBER -
but it's unlikely to be millions! That will mean that any effort will be
relatively small, and will need to be well focussed if it is to be effective
and form a meaningful contribution.

We're planning to have an informal 1/2-dayish meeting at RAL on the afternoon
of December 9 to share what we've learned so far, discuss promising areas,
and start thinking about writing a report to Ken Peach. WE ENCOURAGE ANYONE
INTERESTED TO COME, SEND SUGGESTIONS BY EMAIL, OR AT LEAST LET US KNOW OF
YOUR INTEREST SO THAT WE CAN KEEP YOU INFORMED.

In February Ken envisions a mini-workshop at RAL to discuss the findings and
recommendations from all 3 working groups, so that an action plan can be drawn
up and presented to our funding masters. It is clear that the case will need to
be well thought-out and presented, and may not fly, but it certainly won't
unless we try hard in the short term.

Chris Damerell        E-mail C.Damerell@rl.ac.uk
Rutherford Appleton Lab
Chilton, Didcot, OX110QX, UK.
Work phone (+44) 1235 446298
Work fax   (+44) 1235 446733
Home phone (+44) 1235 523418