1 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 (B A B AR, 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 B A B AR or Belle in both the forward an backward directions  A much longer solenoid and flux return is needed

3 David Hitlin Frascati SuperB Workshop March 17, 2006  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 B A B AR or Belle would, at first glance, seem to be a perfectly adequate detector for at SuperB  A first look at modifying B A B AR, however, turns up issues Using B A B AR 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 We need to grapple with this question now

4 David Hitlin Frascati SuperB Workshop March 17, 2006 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

5 David Hitlin Frascati SuperB Workshop March 17, 2006 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 Super B A B AR 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 marginal A silicon tracker presents a multiple scattering problem

6 David Hitlin Frascati SuperB Workshop March 17, 2006 Backgrounds  Naïve scaling by current indicates that the occupancy and radiation damage issues at a conventional 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

7 David Hitlin Frascati SuperB Workshop March 17, 2006 Detector elements – B A B AR foundation More conservative Less conservative Retain Rebuild/AddRetainRebuild/Add SolenoidSVT(Strips)SolenoidSVT(Pixels+strips) Flux returnDrift ChamberFlux returnDrift Chamber Barrel EMCEndcap EMC(s)Barrel EMC LST’sDIRC SOBEndcap EMC(s) Trigger/DAQBarrel PID Forward PID IFR (especially EC) Trigger/DAQ A constant of the motion: remove the Support Tube

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

9 David Hitlin Frascati SuperB Workshop March 17, 2006 Detector protractor – 9 on 3.1 GeV  ’s     BACKWARD POLAR ANGLES FORWARD POLAR ANGLES

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

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

12 David Hitlin Frascati SuperB Workshop March 17, 2006 SuperB BABAR strawman – I    

13 David Hitlin Frascati SuperB Workshop March 17, 2006 SuperB BABAR strawman – I    

14 David Hitlin Frascati SuperB Workshop March 17, 2006 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

15 David Hitlin Frascati SuperB Workshop March 17, 2006 Vertexing  The SVT we have been discussing, originally based on the SuperB A B AR concept, 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

16 David Hitlin Frascati SuperB Workshop March 17, 2006 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 B A B AR, 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 m 2 ) Must perforce be double-sided, with Si thickess < 200  m Even so, mass resolution is worse than for a gas-based tracker  Choice requires a detailed understanding of backgrounds

17 David Hitlin Frascati SuperB Workshop March 17, 2006 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

18 David Hitlin Frascati SuperB Workshop March 17, 2006 EMC Projectivity & mechanics  EMC crystals are projective in , 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

19 David Hitlin Frascati SuperB Workshop March 17, 2006 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% X 0  Requires ~ 30 cm of space

20 David Hitlin Frascati SuperB Workshop March 17, 2006 PID geometry interacts strongly with the EMC  The current B A B AR 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

21 David Hitlin Frascati SuperB Workshop March 17, 2006 SVT/Main tracking upgrade options SVT OptionProsCons/Questions Very small radius uncooled beampipe Two layers of pixels Five layer SVT  Most robust pattern recognition  Best vertex resolution  Allows lowest energy asymmetry  Most expensive  Are pixels really needed? Small radius cooled beampipe Five layer SVT  Less uncertain (at least until IP is designed and backgrounds calculated)  Vertex resolution is worse  Energy asymmetry greater In all options: remove support tube Tracker OptionProsCons/Questions Drift chamber  Best momentum resolution  Most expensive  Are pixels really needed? Silicon strips  Best rate capability  Better solid angle coverage  Less material in front of EC PID/EMC  Much more expensive  Worse momentum resolution

22 David Hitlin Frascati SuperB Workshop March 17, 2006 EMC upgrade options OptionProsCons Retain Barrel & Forward Endcap (FEC) [Add BEC]  Cheapest  Radiation damage impairs performance  Must disassemble to move  Restricted solid angle  [Awkward barrel/BEC interface] Retain Barrel, new FEC [Add BEC]  Second cheapest  Improved FEC segmentation, resolution, speed  Radiation damage impairs barrel performance  Must disassemble barrel to move  [Awkward barrel/BEC interface] Retain Barrel crystals, rebuild mechanics + New FEC and BEC  Allows better BEC geometry  Can improve material, electronics  Improved solid angle  Improved FEC, BEC segmentation, resolution, speed  Radiation damage impairs barrel performance New LSO EMC  Better resolution, speed, segmentation  More flexible geometry  Most expensive

23 David Hitlin Frascati SuperB Workshop March 17, 2006 PID/IFR upgrade options PID OptionProsCons Barrel - DIRC  Proven concept  Good momentum range  Material in front of EMC  Difficult to have backward EMC endcap Endcap(s) Proximity focussed Cherenkov TOF  Extends PID solid angle  Material in front of EMC endcap(s)  Compatible momentum resolution?  Material in front of EMC endcap(s)  Extremely good timing in magnetic field required  Compatible momentum resolution? IFR OptionProsCons Barrel LST  Likely has adequate rate capabilty and radiation hardness  Endcap LST  May have adequate rate capabilty and radiation hardness  May require substantial additional shielding in upstream direction

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

25 David Hitlin Frascati SuperB Workshop March 17, 2006 Comparison – B A B AR and Belle for SuperB From Yamauchi’s Hawaii 2005 talk

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

27 David Hitlin Frascati SuperB Workshop March 17, 2006 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 B A B AR (or Belle)- based upgrade

28 David Hitlin Frascati SuperB Workshop March 17, 2006 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 Tevatron At 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  B A B AR, with very substantial upgrades, provides a suitable platform for a SuperB detector