1. Background issues for the Super-B background simulation team
G.Calderini (LPNHE, Paris)
for the
Super-B background simulation team
Machine/Detector joint session

2. This time mainly a list of open issues
Post-CDR era
Adding what is missing
The tools
For the Beamline
For the Detector
The interaction with the final focusing design
The interaction with the detector design
(too slow till now, in my opinion)

3. Pair production Are we happy with the level of generator
Studied with Guinea Pig and Diag-36 generators
After some debugging, the two results are more
similar
Are we happy with the level of generator
discrepancies? Are they acceptable?
30MHz/cm2
Pt accept. @ 1.5 T , 1.2 cm
~Angular acceptance
1.2
1.5
R(cm)

4. Not fully simulated with Geant for the CDR.
Background analysis in the tracker is based
on kinematical distributions
We agreed we should go for a more detailed
simulation. Is it just matter of sending the
primaries to Geant-4?
Is it going to work in a straightforward way?
Probably not…
CPU time computing issues? Other issues?

5. Radiative Bhabhas Bremsstrahlung process in the forward direction in
BhaBha scattering: e+e- -> e+e- g
Simulated with the BBBrem generator and fully propagated in the Geant-4 description. But this is good for low angles only.
Integrate with BHLUMI/BHWIDE for larger
angles in the same way we plugged BBBREM in the
Geant-4 framework. This should be not difficult,
we did that already for BaBar
Neutrons ??? Probably yes ! Should we look at?

6. Radiative Bhabhas Shielding: we added tons of Tungsten to protect the
detectors (with 10cm thick masks we succeeded!)
Could we do better? Should we interact more with the
machine design to minimize the backscattering?

7. Touschek
The study prepared for the CDR was based on the Boscolo code (LNF). This contains an approximate description of the ring and transport the off-energy particles due to intra-bunch scattering. The primaries
hitting the beampipe are passed to Geant-4
Expected loss particle rate in a +/- 4m from the
IP = 2.3 MHz/bunch, reduced to 90kHz after collimators
deployment.
This is in good shape at interface level, but still there
are problems with the lifetimes. More work is probably
needed at the generator level !

8. Lost particles
Mainly Coulomb/Bremsstrahlung interactions with residual
gas molecules in the beampipe. For the CDR effort, the estimate was based on PEP-II rates and rescaled for beam currents.
Probably a pessimistic extrapolation, given the absence of
permanent dipoles very close to the IP in SuperB final
focusing.
Further effort necessary for a better description
As soon as an updated final focus design will be available, we should try to implement a Turtle description or something equivalent.
This is not difficult but requires a lot of work, unless
suitable tools are available to produce the decks…

9. Injection Should this be considered?
We never discussed injection backgrounds in the Super-B design.
Given the BaBar experience with trickle injection,
this is probably not a dominant source, but…
Should this be considered?

10. Detector Larger manpower contribution from subdetectors?
Is the level of detector description satisfying?
Probably not, the present detector is simplified
The segmentation for many subsystems is neither adequate nor optimized
(we actually were not provided with a “frozen” detector design until the very last days)
Larger manpower contribution
from subdetectors?

11. Useful developments Better organization of the software
Presently the code is under CVS but organized as
a single package. Difficult for different people to
work on different parts at the same time
Interfaces for the beamline optics
Some software, like the BDSIM interface, used for
ILC studies, allows to import MAD configurations into
a Geant-4 description. That could help, even if we tried
a little bit already and it gave problems…
Interfaces for the geometry/detector
As in the case of BaBar (for which we developed an
interface to SolidEdgeTM ) it’s possible to use CAD
oriented extensions to Geant-4: GDML ?

12. Organization In the CDR phase, the integration between background
simulations and final focusing design was rather limited,
as well as the interaction with some subdetector.
This needs absolutely to be improved in the next phase.
Background studies are not intended to determine simply
if a certain detector is feasible, but should be used to
optimize the machine and the detector design
The turn-around time is critical to keep the ball moving,
but also periodic interaction with people involved

13. Manpower Many Institutions have already expressed their
interest to participate to Super-B background
studies. But who is really going to work?
How should we organize the work?
Some proto-organization for some source of background is already in the Eurocrab proposal, but it refers only to a subsample of the issues.
We could think to a more extended structure and then Eurocrab, if approved, could fit in.
Background subgroups?
MDI-like meetings with detector/machine people?
We need at least a core group working high-priority