Detector WG

1
Detector WG

• Francesco Forti
• SuperB Workshop
• LNF, 16-18 March, 2006

2
A SuperB Detector

• Basic conclusion from December Workshop
• It is possible to reuse large parts of Babar and
  Belle with relatively minor technology changes
• Detector components
• Silicon vertex, with small radius pixels,
  essential for reduced boost.
• Drift chamber
• DIRC style PID, with improved readout
• CsI(Tl) calorimeter in barrel, something faster
  (LYSO) in endcap
• Existing coil
• LST style muon detectors

3
Issue number 0

• Beam parameters
• Current and Collision frequency vary wildly in
  different designs
• Was mA and 1MHz in december
• Raimondi Round with extraction 100 mA and 10
  MHz
• Raimondi Flat(3) uncompressed 1600mA and 500
  MHz
• Seeman 4500 mA and 68 MHz
• Different options have very large impact on
  technology choices and on the reusability of
  Babar and Belle components.

4
Collision frequency

• With 0.1-1MHz fc one could exploit the beam
  crossing time structure to relax detector
  constraints
• Drift time
• Electronics shaping time
• Crystal decay time
• One the other hand a low fc implies overlapping
  events (mainly Bhabha)
• The 10-50MHz regime is the LHC electronics area
• It might be possible to exploit the bx time
  structure, but is it useful ?
• At high fc (gt100MHz) back to current BFactories
  operation mode
• Continuous beam, no bx information
• no pileup

5
Current

• Two consequences of higher currents
• higher background in the detector
• occupancy
• radiation damage
• power dissipation in the beampipe requires water
  cooling
• more material
• larger radius

6
Types and level of backgrounds

• Beam gas
• Synchroton radiation
• ? Both proportional to current
• Should not be a problem at Superb
• They become a problem at higher currents
• Luminosity sources (eg radiative Bhabhas)
• Careful IR design. Bhabhas into the detector are
  there.
• Beam-beam interactions
• Potentially important
• Touschek background
• 1/E2. Improves with smaller asymmetry. But, much
  higher beam density
• Thermal outgassing
• Due to HOM losses. Not an issue with small
  currents
• Injection background
• Not an issue because of damping rings scheme
• Maybe not true anymore with the 1 collision/turn
  scheme
• Bursts
• Due to dust. No real cure. Need robustness of
  detector

7
Background bottom line

• Probably reasonable to assume background is not
  larger than what with have today
• Cannot claim a large background reduction with
  present schemes
• Need to design a robust detector with the enough
  segmentation and radiation hardness to withstand
  surprises (x5 safety margin)
• IR design is critical
• Radiative Bhabhas
• Syncrotron radiation shielding
• Shielding from beam-beam blow up

8
Issue number 1

• Boost
• lower boost advantegeous for machine design
• Babar 9 3.1 ß?0.56
• Belle 8 3.5 ß?0.45
• SuperB? 7 4 ß?0.28
• we can afford to have a lower boost only if the
  vertexing resolution is good
• small radius beam pipe
• very little material in b.p. and first layer
• if not, then we should stay with higher boost
  (0.45)

9
Separation significance

• ltDzgt/s(Dz) vs bg

10
Detector components

• Vertexing
• Thin pixel layer glued on beam pipe
• Good aspect ratio for small radius (compared to
  strips)
• Improves patter recognition robustness
• needs RD
• Intermediate tracking
• Strip detectors
• More or less like the current detectors
• Reduction in thickness would be desirable, but
  not essential
• Central tracking
• Drift chamber
• Solid state tracking not performant at low
  momentum
• Need to optimize cell size against occupancy
• Belle has developed a fast gas small cell DCH,
  but with a degraded resolutions

11
Detector components

• PID
• Cerenkov based PID like DIRC
• Need development on readout
• Fast focusing DIRC
• TOP
• Endcap region requires special study
• Calorimeter
• Barrel part could be reused (see other talks)
• In the endcaps require smaller Moliere radius and
  faster crystals ? LYSO
• Higher currents and smaller Bhabha pileup may
  change this conclusion
• Muon
• It doesnt seem to be a problem
• Trigger/DAQ
• Calorimeter and/or tracking information
• Not substantially different from current schemes.