David Hitlin May 17, 2002 FPCP

1. David HitlinMay 17, 2002 FPCP Super B Factory Status Report

2. Is there a 1036 future? • This talk will not discuss in detail the physics case for a 1036 machine • The case is strong; we are working on refining the arguments • CP violation in B decay is likely to remain the centerpiece • Precision CP studies and other measurements related to achieving the ultimate sensitivity in consistency tests of the Standard Model • Measurements of CP-violating asymmetries in rare decays, such as BK*l+l-as a sensitive new probe of SUSY effects • Complementarity with hadron machines • Rather, the talk is aimed at exploring an upgrade path from the current BABAR detector to a new SuperBABAR detector capable of coping with 1036 • Presumably a similar case could be made for an upgraded Belle

3. With 10 ab-1, the Gronau-Wyler construction can place a stringent limit on penguin amplitudes Isolating the penguin contribution in Requires measurement of taggedanddecaybranching fractions Roodman Roodman

4. At 1036, e+e- is complementary to LHCb/BTeV/ATLAS/CMS SLAC-PUB-8970

5. MSSM:CPasymmetry inb  sg Bartl, Gajdosik, Lunghi, Masiero, Porod, Stremnitzer and Vives, hep:ph/0103324

6. The 1036 environment • The Snowmass Strawman design was developed as an existence proof that a 1036 detector could be built at all • Main concerns • Radiation dose • Machine-related backgrounds • synchrotron radiation • particle backgrounds, due primarily to continuous injection • Physics backgrounds – hadronic split-offs, ….. G. Eigen

7. We concluded that such a detector could be built

8. A potential upgrade path from BABAR to SuperBABAR • Flux return and IFR upgradedà la MINOS • Remove SVT,DCH, EMC,DIRC • New EMC –liquid Xe • New tracker –Two inner pixellayersSeven(?) thindouble-sidedSi-strip archlayers • New DIRC(s) with compact readout DIRC

9. The power bill is a function of the energy asymmetry J. Seeman

10. Studies of the energy asymmetry have been updated Normalized luminosity degradation factor S. Wagner

11. Tracking and Particle ID • Tracking • Snowmass concept of two pixel layers + seven double-sided strip layersis well-suited to the upgrade • B=1.5 T vs. 3 T for Snowmass design • Router = 75 cm vs. 45 cm • Momentum resolution improved by ~40%, but silicon area is greater • Particle ID • Barrel • New non-SOB DIRC is under development • Quartz is sufficiently radiation hard • Need pixel readout • Endcap • Requires single photoelectron readout in a magnetic field • No DIRC design yet exists • Aerogel would work

12. EMC and Instrumented Flux Return • EMC requirements • Fast response • Radiation Hardness • Excellent energy and position resolution • Longitudinal segmentation for best possible p/e separation • Minimal interruption in barrel/endcap region Can be met by a scintillating liquid xenon calorimeter • IFR requirements • High rate capability • Good time resolution • Stable response Can be met by a MINOS-type scintillating strip design

13. Comparison of CsI(Tl), LSO, Liquid Xe

14. Using the 175nm light from liquid xenon • Xe scintillation light has been measured with several techniques • Multi-alkali PMT • CsI photocathodes • Wavelength-shifting coatings • APD’s in LXe at ~165K

15. Conceptual design of a scintillating LXe EMC for SuperBABAR • The key idea is to absorb the 175 nm scintillation light in wavelength shifting fibers, read out by a photosensor, such as a pixelated APD, that works at cryogenic temperatures in a magnetic field • Shift from UV to visible on the cell walls and then shift again in a fiber • The volume of liquid xenon required is ~10 m3  30 tons (1 year’s production) • Current world price of LXe is ~ $2,500/liter • LXe light yield = 75,000 photons/MeV • Estimated photoelectron yield is hundreds of photoelectrons/MeV • Stochastic term in energyresolution <1% • Energy resolution will be determinedby Fano factor, insensitive material,shower leakage, albedo, …….. • Spatial resolution is determinedby number of sensors s/E E (GeV)

16. Example EGS showers in liquid xenon 100 MeV 500 MeV 750 MeV 200 MeV Thanks to Ralph NelsonandRay Cowan 300 MeV 1000 MeV 14 X0

17. Hexagonal cell structure built of eptfe or aluminized mylar • Non-load bearing hex structure • TPB-coated eptfe compartments • Reflectivity for shifted light is 95% for sufficient thickness • Non-sensitive material • Mylar 5 mils = 4x10-4 X0 • eptfe 0.5 mm = 2x10-3 X0 • Fiber 1 mm = 2x10-3 X0

18. Unit cell of the LXe EMC • Hexagonal cells of ~ 1 Molière radius in transverse dimension are formed from thin quadraphenyl butadiene (TPB)-coated eptfe sheets • Cells are not load-bearing, thus thin • Longitudinal segmentation is provided byTPB-coated optical separators, with WLS fibers sensitive only in a particular segment • Three segments is probably optimal • Massless gap – ascertain whetherthere was an interaction in materialin front of the EMC 2, Two larger segments, with divisionnear shower max • Fibers are read out by a pixelized APD,located in the LXe volume • Clear fibers between coil segment and APD • Redundant readout is simple and inexpensive • All readout at rear, minimizing nuclear counter effect

19. External QE of TPB # photons emitted into 2p# photons incidentvs incident wavelength (Lally, et al.) is high LXe scintillation How do we detect the shifted light from TPB? - continued RMD pixelized APB QE <QE> ~80% Y8,Y11 emission Y11 Y11 Y8 Capture efficiencyof Y11 ~5.5-7% Y8,Y11 absorption TPB emission

20. polystyrene PMMA fluorinatedPMMA 1 mm 30 mm WLS fibers and APD readout • Does the light get into the fibers? • Yes: npolystyrene=1.59 nLXe=1.57 • Conversion efficiency of WLS: • Conversion ~80-90 % in Y11 • Capture efficiency of fiber • Round • Single clad 3.1% • Multi clad 5.4% • Square • Single clad 4.2% • Multi clad 7.3% ??? • Square fiber has more surface area and is a better match to square pixel transmission coefficient close to1

21. Candidate readout device • RMD pixelized APD 8x8 array with 1mm pixels MINOS Far Detector 1 mm WLS fibers

22. 1.2 1.2 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 There is an optimal helix pitch • Absorption length of Y11 fiber dictates the pitch • For a single fiber, read out at both ends: • By varying the pitch, light collection efficiency can be made uniform labs(cm) 500400300 200 100 Efficiency (%) Efficiency (%) labs (cm) 500400300 200 100 Pitch (cm) Pitch (cm) 9X0 section 5X0 section

23. A working device trumps a calculation • Scintillation light from liquid helium has been observed using a technique much like that proposed here • LHe scintillates at • TPB (tetraphenyl butadiene)(0.2mg/cm2) evaporated on 1.6mm Gore-tex (eptfe) walls ~20cm length x 4.1cm diameter + 2 coiled Kuraray Y11 fibers (~430  490nm) @ 6mm pitch • Hamamatsu R943-02 PMT with 13% QE at 500 nm • Estimated efficiency 0.04% to 0.14% • Radiative decay of the metastable molecule in liquid helium • D. N. McKinsey, C. R. Brome, J. S. Butterworth, S. N. Dzhosyuk, P. R. Huffman, C. E. H. Mattoni, and J. M. Doyle • Department of Physics, Harvard University, Cambridge, Massachusetts 02138 • R. Golub and K. Habicht • Hahn-Meitner Institut, Berlin-Wannsee, Germany • PHYS. REV.A59, 200, JANUARY 1999 80nm

24. The future of e+e-- based heavy flavor physics • The physics case for a data sample of 50 ab-1 is there • A focused argument must still be crafted • It appears that a 1036B Factory can be built • It is likely that it will have bg =0.5 or less • There is an upgrade path from BABAR to SuperBABAR • An LXe-based upgrade of BABAR may be a viable approach • LXe is likely just one of several alternative approaches • Alternative technologies also likely exist for tracking, muon ID, PID

25. Coming to a laboratory near you Fall '02 Watch for it ! The Sequel