Background issues G Calderini LPNHE Paris for the

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

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)

Pair production 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? 30 MHz/cm 2 Pt accept. @ 1. 5 T , 1. 2 cm ~Angular acceptance 1. 2 1. 5 R(cm)

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?

Radiative Bhabhas Bremsstrahlung process in the forward direction in Bha 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 Ba. Bar Neutrons ? ? ? Probably yes ! Should we look at?

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

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 +/- 4 m from the IP = 2. 3 MHz/bunch, reduced to 90 k. Hz 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 !

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 Super. B 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…

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

Detector 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?

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 Ba. Bar (for which we developed an interface to Solid. Edge ) it’s possible to use CAD oriented extensions to Geant-4: GDML ? TM

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

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