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David Hitlin Frascati Super B Workshop March 17, 2006

BABAR. Upgrading for Super. B. David Hitlin Frascati Super B Workshop March 17, 2006. Reusing existing detectors at Super B.

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David Hitlin Frascati Super B Workshop March 17, 2006

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  1. BABAR Upgrading for Super B David HitlinFrascati SuperBWorkshopMarch 17, 2006 David Hitlin Frascati SuperB Workshop March 17, 2006

  2. Reusing existing detectors at SuperB • With luck, we will soon have to face the question of whether SuperB should have a new detector built from scratch, or whether an existing detector (BABAR, Belle, or even CLEO-II) could be upgraded to do the job • In order to meaningfully discuss this question in detail, it is necessary to nail down a few important parameters • Do we collide every bunch or collide trains kicked out of rings? • The energy asymmetry (7x4, 8x3.5, 9x3.1) • Two beams vs four beams • A four-beam machine can have boosted decays in both the “forward” and “backward” directions. This is a major perturbation on the design • Requires a detector that has essentially the forward section of BABAR or Belle in both the forward an backward directions • A much longer solenoid and flux return is needed David Hitlin Frascati SuperB Workshop March 17, 2006

  3. We need to grapple with this question now • By the end of the year, we may need to provide preliminary details on schedules, costs and R&D needs for both the collider and detector • In order to confront the detector side, it is helpful to have a specific configuration in mind • An upgrade of either BABAR or Belle would, at first glance, seem to be a perfectly adequate detector for 1036 at SuperB • A first look at modifying BABAR, however, turns up issues • Using BABAR as the foundation seems feasible, however • Using Belle would likely generate essentially a similar end result (cf Tim Gershon’s talk) • A first look turns up a variety constraints, many of which are generic David Hitlin Frascati SuperB Workshop March 17, 2006

  4. Collider scheme has a direct effect • A linear collider-type machine and a storage ring-type machine have very different time structures and currents • These differences directly effect detector design • Sensitivities • Beam pipe diameter and thickness (cooling?) • Trigger/DAQ system - fundamental • Response time of detector subsystems • Tracker • Electromagnetic calorimeter • Radiation hardness David Hitlin Frascati SuperB Workshop March 17, 2006

  5. Linear collider vs storage ring • Linear collider • Small diameter, uncooled beampipe • “SLD” like DAQ • CsI(Tl) OK, at least for the barrel • Drift chamber tracker • Storage ring with LC final focus • Cooled beampipe thicker material (two walls + water) likely larger diameter • SuperBABAR type DAQ • Fast, radiation hard EMC (LSO/LYSO, pureCsI) • Barrel/endcap radiation sensitivity depends on luminosity term • Fast decay time is an advantage • A drift chamber is marginalA silicon tracker presents a multiple scattering problem David Hitlin Frascati SuperB Workshop March 17, 2006

  6. Backgrounds • Naïve scaling by current indicates that the occupancy and radiation damage issues at a conventional 1036 machine are much reduced at a linear collider type machine and are slightly better than SuperPEP-II or SuperKEKB in the new storage ring scheme, due to reduced circulating currents (scaling as the current, if the PEP-II luminosity term can be controlled) • Background sources • Current-related • Luminosity-related • Beam-beam • Touschek (intrabunch scattering) • Synchrotron radiation • We must move beyond naïve scaling to a Decay Turtle type calculation of lost particle backgrounds David Hitlin Frascati SuperB Workshop March 17, 2006

  7. Detector elements – BABAR foundation A constant of the motion: remove the Support Tube David Hitlin Frascati SuperB Workshop March 17, 2006

  8. SuperB BABAR strawman – I David Hitlin Frascati SuperB Workshop March 17, 2006

  9. Detector protractor – 9 on 3.1 GeV g’s BACKWARDPOLAR ANGLES FORWARDPOLAR ANGLES   bg U David Hitlin Frascati SuperB Workshop March 17, 2006

  10. Detector protractor – 8 on 3.5 GeV g’s David Hitlin Frascati SuperB Workshop March 17, 2006

  11. Detector protractor – 7 on 4 GeV g’s David Hitlin Frascati SuperB Workshop March 17, 2006

  12. SuperB BABAR strawman – I  bg  U David Hitlin Frascati SuperB Workshop March 17, 2006

  13. SuperB BABAR strawman – I  bg  U David Hitlin Frascati SuperB Workshop March 17, 2006

  14. Support tube • The support tube has some construction/alignment advantages, but the resolution penalty due to multiple scattering is severe • It should be done away with in an upgrade • Mount pixels/SVT on the beam pipe or on main tracker David Hitlin Frascati SuperB Workshop March 17, 2006

  15. Vertexing • The SVT we have been discussing, originally based on the SuperBABARconcept, involves two initial pixel layers followed by a ~5 layer SVT, starting at a very small radius (≤1 cm) • This has sufficiently good primary vertex resolution to allow an energy asymmetry as small as 7x4 GeV if the beam pipe radius is ≤10mm • In the storage ring-based design, things may be different • With currents of 1-2 A, water cooling required • A cooled beam pipe would have more material and would require a larger radius for the first tracking layer • What is the minimum practical beam pipe radius? • Needs a preliminary IP design and simulation David Hitlin Frascati SuperB Workshop March 17, 2006

  16. Main Tracking • In a linear collider, a drift chamber (even a jet chamber) would be the clear choice • In the storage ring design, the viability of a gas-based solution remains to be demonstrated • Drift Chamber • Carbon fiber mechanics would be advantageous for the endplates, especially if we want to deploy endcap PID • Where do we mount the on-chamber electronics? • In BABAR, the drift chamber electronics is entirely in the backward direction • Can tracking solid angle be extended below ~300 mrad? • Silicon Tracker • Requires a large area of silicon (CMS=200 m2) • Must perforce be double-sided, with Si thickess < 200mm • Even so, mass resolution is worse than for a gas-based tracker • Choice requires a detailed understanding of backgrounds David Hitlin Frascati SuperB Workshop March 17, 2006

  17. EMC • Should the barrel CsI(Tl) calorimeter be retained? • There is already some radiation damage observed (barrel & EC) • The mechanical structure of the existing EMC barrel is a major constraint • Projective towers, displacement of collision point • Calorimeter would have to be completely disassembled for shipping • Several of the important new physics objectives (most are related to recoil-related studies) make hermeticity increasingly important • This motivates the addition of a backward EMC endcap • Both a forward and backward EMC endcap should be fast and radiation-hard (LSO/LYSO), as should the barrel, if it is replaced • Smaller Molière radius and radiation length and fast decay time are a significant advantage David Hitlin Frascati SuperB Workshop March 17, 2006

  18. EMC Projectivity & mechanics • EMC crystals are projective in f, very nearly in  • The projective geometry itself is independent of boost • The offset of the IP, meant to optimize solid angle coverage for a given boost, is a non-negliglible constraint on other boosts • If the EMC mechanics were to be rebuilt: • By removing crystals from the forward barrel and adding new crystals at the rear, one could optimize for a lower boost • By stiffening the carbon fiber egg crate structures with an inner carbon fiber wall, one could reduce the dead material between crystals, improving the energy resolution • If the barrel were taken apart, the shaping time constants could be re-optimized • Were both the barrel and forward endcap to be rebuilt, a geometry with no real barrel/endcap break (à la H1) could be built without precluding access to the tracker David Hitlin Frascati SuperB Workshop March 17, 2006

  19. Particle ID • The DIRC water standoff box is a source of background from beam-related particles • In a detector for the storage ring design it is desirable to remove the SOB • Doing so depends on development of compact DIRC readout • It is difficult, but perhaps not impossible, for a barrel DIRC and a rear EMC endcap to coexist • Even if a readout that works in a magnetic field is developed, there would be a substantial amount of material in the barrel/rear endcap corner • Endcap PID • A proximity-focussed Cherenkov ring imaging device with aerogel radiator(s) appears to be a good choice • Presents 10-20% X0 • Requires ~ 30 cm of space David Hitlin Frascati SuperB Workshop March 17, 2006

  20. PID geometry interacts strongly with the EMC • The current BABAR DIRC readout precludes a useful backward EMC endcap • An evolved design, with a quartz standoff and pixel pmt readout in a magnetic field poses its own severe limitations on an upgraded EMC • If the readout is brought out beyond the barrel EMC, there is perforce an awkward break between the barrel and BEC • If the readout is inside the EMC, the barrel/EMC break can be much more graceful, but there will be a rather large concentration of high Z material in the EMC corner region David Hitlin Frascati SuperB Workshop March 17, 2006

  21. SVT/Main tracking upgrade options In all options: remove support tube David Hitlin Frascati SuperB Workshop March 17, 2006

  22. EMC upgrade options David Hitlin Frascati SuperB Workshop March 17, 2006

  23. PID/IFR upgrade options David Hitlin Frascati SuperB Workshop March 17, 2006

  24. Trigger/DAQ upgrade options See talk by Gregory Dubois-Felsmann David Hitlin Frascati SuperB Workshop March 17, 2006

  25. Comparison – BABAR and Belle for SuperB From Yamauchi’sHawaii 2005 talk David Hitlin Frascati SuperB Workshop March 17, 2006

  26. Comparison - II From Yamauchi’sHawaii 2005 talk David Hitlin Frascati SuperB Workshop March 17, 2006

  27. Moving forward • We need an R&D plan • Formulate R&D objectives • Develop an R&D schedule • Formulate a budget • See David Leith’s talk • We need a reliable cost estimate of a BABAR (or Belle)-based upgrade David Hitlin Frascati SuperB Workshop March 17, 2006

  28. Conclusions • The details of a SuperB detector depend intimately on whether SuperB is a linear collider or a (new type of) storage ring • Parenthetic remark • In 1977 I ran a group at Aspen that was charged with designing (in the Summer Study sense) a detector for what eventually became the TevatronAt that time, it was undecided whether the machine would be based on collisions between the existing 200 GeV machine and a new 1 TeV superconducting ring, or whether the collisions would take place solely in the 1 TeV ring.In other words, would the CM be stationary in the lab, or moving in the lab (perhaps that’s where Oddone got the idea)The SuperB detector issue is trivial by comparison • BABAR, with very substantial upgrades, provides a suitable platform for a SuperB detector David Hitlin Frascati SuperB Workshop March 17, 2006

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