11-16-95

Report on the BB mini-review of Oct 1995

by Fred Wohn and Toru Sugitate

This BB report consists of three sections (mechanics, electronics and
simulations) in outline form, each having a brief list of action items
with suggested dates, followed by a list of issues and concerns.

A. Mechanics:

1\. Design review at BNL needs to be held in Jan 1996. (There is no
review committee in Japan that has to approve the BB design,)

2\. Position in z of the BB counter needs to be decided. A 10-28-95
e-mail from Toru discussed the 3 options shown below:

\(a\) Place the BB array face at Z==1400 mm.

R(mask)=1400 mm X tan(5.7) = 139.74 mm \< R(inscribe)

Z(back plate) = 1630 mm

=\> Mask 1/8 sensive area of 12 PMTs in outermost ring; back plate is
out of the primary space allocation by 30 mm.

\(b\) Place the BB array face at unmasked position.

Z(bb)=144.08 mm/ tan(5.7) = 1443.50 mm

Z(mask)=144.08 mm == R(inscribe)

Z(back plate) = 1673.5 mm

=\> All PMTs see the collision center; back plate is out of the primary
space allocation by 73.5 mm.

\(c\) Place the BB back plate (back face) at Z==1600mm.

Z(bb)=1370 mm

Z(mask)=1370 mm X tan(5.7)=136.74 mm \< R(inscribe)=144.08 mm

Z(back plate)=1600 mm.

=\> Mask 1/4 sensive area of 12 PMTs in outermost ring; back plate is at
the edge of the primary space allocation.

The LANL response indicated option (b) would be fine. However, there are
concerns about the cable runs and whether the flower pot needs to be
notched to obtain the space needed for the cable runs. This needs
further discussion (between Hiroshima and LANL). A reasonable goal is to
have this settled by the time of the Jan 1996 design review at BNL.

3\. Where in z to change the beam pipe from Be to SS? The concern here
is the effect of the beam-pipe material on the BB detector for beams
from p-p to Au-Au. This is on the simulation study agenda - see Section
C.

B. Electronics:

1\. \"Kink\" in the Nevis discriminator. Both Toru and Chi would like to
get rid of the kink (which may then enable a \"quick time\" slew
correction to be done). Plans for this are vague. An action item is to
specify what to do at Nevis and to set a reasonable time schedule for
doing it.

2\. Tests of the new LANL CFD may show it to be a viable alternative to
the Nevis CFD, especially if the Nevis \"kink\" is not fixed. A schedule
for this test should be specified soon to permit a decision date to be
set on the choice (Nevis versus LANL) for the BB CFDs.

3\. Measurement is wanted to confirm that the time drift in the 5-m
signal cable is really 4.3 ps per 10 degree C. For histograms of 25 ps
width, this is small enough, but Toru would like to have this confirmed.
What is needed is a decision as to who is to confirm it and when.

C. Simulation Studies: The following comes mainly from a 11-10-95 e-mail
by Toru and his grad student, Kazuhiro Kaimi. It is an exhaustive plan
which covers the simulation issues raised at the Oct 1995 mini-review.

1\. QED background: Study QED events.

Event generator: QED_EE

What to see: ADC distribution

Momentum distribution at BB

PID in BB

Detection rate

Action: Compare the spectra with magnet \'On\' and \`Off\'

2\. Trigger: Study LVL-1 trigger performance.

Event generator: UA1 and QED_EE

What to see: w/UA1 event

Difference in performance of 3 timing methods:

FTDC (fastest TDC value)

MTDC(mean of TDC values)

HTDC(peak of TDC values)

w/UA1+QED mixed event

Difference of performance of 3 timing methods:

Fake trigger rate

Efficiency

w/BB on North and South:

Fake trigger rate

Efficiency

Position resolution

3\. Luminosity monitor: Study BB as luminosity monitor.

a\) Heavy Ion (We observe QED electrons)

Event generator: QED_EE

What to see: Detection rate

Threshold dependence

Action: \`Magnet On\' and \`Off\'.

b\) proton + proton (We observe the secondary particles)

Event generator: I don\'t know what I should use

What to see: Detection rate

Action: \`Magnet On\' and \`Off\'.

4\. Effect of beam pipe: Study beam-pipe effects on BB.

Event generator: UA1 and QED_EE

What to see: PMT multiplicity

TOF resolution

ADC distribution

Momentum distribution

PID

Action: Study, for a few selected pipe compositions,

\`Magnet On\' and \`Magnet Off\'

NOTE: UA1 and QED_EE are built-in event generators in PISA, but, since
the UA1 generator can generate only pions, it is an unrealistic choice.

\[In Ames, Athan Petridis has already addressed some of the time spectra
issues involved in simulating the LVL-1 trigger response for BB. He will
assist the Hiroshima simulation studies in this regard if they wish.\]

D. Issues and Concerns:

1\. The Critical Path concern is the \"warming up\" of PMTs for a
reasonable period (such as 8 weeks) to eliminate bad PMTs before
installation. This may be difficult to do if delays in the PMT schedule
occur.

2\. A time schedule to decide upon the CFD needs to be set soon.
Vagueness in the current schedule statements is a concern.

3\. At the Oct 1995 BB mini-review, Chi stated his concerns about
Nevis\' \"engineering manpower and DAQ schedule\". These concerns are
shared by us as the BB electronics work at Nevis is likely to be
impacted. An update on this situation by Chi at the next DC meeting is
recommended.

4\. Event generators. Several of the studies outlined in section C above
refer to event generator needs. Charlie\'s same day reply to Toru\'s
11-10-95 e-mail showed his concern and stated some ways to try to get
help with these needs. These event generator inadequacies have been
realized for a long time, but the slow progress towards resolving it is
a major concern. (Other subdetectors besides BB are also impacted.)
Because of the event generator issues, completing the BB simulation
studies planned may be delayed significantly. Suggestions on what to do
about the issue of event generators are welcomed!