David Hitlin Caltech December 3, 2004

1. Physics Requirements for a Super Factory Trigger B David Hitlin Caltech December 3, 2004 D. Hitlin Super B Factory Trigger Workshop

2. Physics objectives of a Super B Factory • The physics objectives of an experiment at a Super B Factoryrevolve around the search for New Physics. The specific approaches fall into several distinct categories • Improvements in the classic unitarity triangle-related measurementsto the “ultimate” precision [a balance of theoretical, statistical and systematic uncertainties] • UT angles • measure asymmetries with minimum systematic error • lepton tag has smallest systematics • Measure branching ratios of rare modes for g • UT sides • use the recoil method to reduce backgrounds and theoretical uncertainties • Maximum sensitivity for very rare decays – B, D, t • Branching fractions • ACP, AFB • Kinematic distributions D. Hitlin Super B Factory Trigger Workshop

3. p Brecoil e- D* n Breco e+ Xu The recoil physics method at the¡(4S) • Fully reconstruct one of the two • B’s in hadronic modes (for some • topics, in semileptonic modes as well) • …and do it with “high” efficiency • Semileptonic decays • B D(*)n, B (p,r)n, BXc,un …… () • B D(*)tn (sensitive to New Physics) • B D(*)tn • Purely leptonic decays Btn, …. • B Knn • Binvisible • B Xsg • The rest of the event is the otherB, whose four-momentum is known You have a single Bbeam, withreduced systematics inVcb, Vubstudies, and reduced backgrounds for rare decays, especially those involving neutrinos or photons D. Hitlin Super B Factory Trigger Workshop

4. Measurement precision – angles of the Unitarity Triangle Theory: a ~5%, b ~ 1%, g ~0.1% D. Hitlin Super B Factory Trigger Workshop

5. Probes of new physics - I • Measure the CP asymmetry in modes other than that measure sin2b in the Standard Model • Precision of benchmark sin2b in can improve to the 1% level • Expect the same value for “sin2b ” in“ ,but different SUSY models can produce different asymmetries • A great deal of luminosity is required to make these measurements to meaningful precision D. Hitlin Super B Factory Trigger Workshop

6. Extrapolated statistical errors on CP asymmetries BABAR measurement errors 10 to 50 ab-1 are required for a meaningful comparison Currentprecision D. Hitlin Super B Factory Trigger Workshop

7. Measurement precision – rare decays D. Hitlin Super B Factory Trigger Workshop

8. Measurement precision - rare B decays D. Hitlin Super B Factory Trigger Workshop

9. Measurement precision – rare decays Masiero, Vempati, Vives tmg is sensitive to 23 generation mass insertions,(analogous to b sss) but in the lepton sector D. Hitlin Super B Factory Trigger Workshop

10. fKS BABAR(now) fKS 30 ab-1 The scale of New Physics • Mass insertion approximation: model-independent f23 mass insertion f13 mass insertion DACP (J/ KS-fKS) DACP (J/ KS-p0KS) Ciuchini, Franco, Martinelli, Masiero, & Silvestrini D. Hitlin Super B Factory Trigger Workshop

11. Physics demands an open trigger • In the face of the impressive rates and amounts of data that will be encountered at a Super B Factory, the first reaction is usually to think about a restrictive trigger • This is unlikely to work, since the physics requires • A large, unbiased sample of fully reconstructed B decays • Recoil studies, ACP, B to invisible, etc. • Sensitivity to rare t decays • A trigger that can do this will manifestly provide a large sampleof D decays as well D. Hitlin Super B Factory Trigger Workshop

12. The New Snowmass Year • The “Snowmass Year” was defined in 1988, based on data from CESR/CLEO: 1 Snowmass Year = 107 s • The Snowmass Year factor is meant to account for • The difference between peak and average luminosity • Accelerator and detector uptime • Deadtime • ……………………….. • PEP-II performance April 2003-April 2004 (Dec 03 Trickle LER, Feb 04 Trickle HER) • Given the excellent performance of PEP-II/BABAR and KEK-B/Belle, and the advent of trickle injection, the modern B factory Snowmass Year constant is 1.4 x 107 • Thus we can integrate 10 ab-1/year with 7 x 1035cm-2s-1, instead of with 1036cm-2s-1 D. Hitlin Super B Factory Trigger Workshop

13. 1036 7x1035 2x1035 20% 1036 7x1035 2x1035 Now: 8 physics clusters Occupancy extrapolations are uncertain, but sobering D. Hitlin Super B Factory Trigger Workshop

14. Tracking will have to be done with silicon, not gas • We will have to develop a silicon tracking trigger D. Hitlin Super B Factory Trigger Workshop

15. Top module D. Hitlin Super B Factory Trigger Workshop

16. Bottom module D. Hitlin Super B Factory Trigger Workshop

17. Midplane module 574% D. Hitlin Super B Factory Trigger Workshop

18. There will be pixels, (striplets) and DSSD layers Pixel or striplets (2 layers) Intermediate DSSD(3 layers) Central Silicon Tracker(4 layers) R(outer) = 60 cm D. Hitlin Super B Factory Trigger Workshop

19. There is a fast, rad hard replacement crystal for CsI(Tl) D. Hitlin Super B Factory Trigger Workshop

20. Comparison of CsI(Tl), LSO, Liquid Xe D. Hitlin Super B Factory Trigger Workshop

21. D. Hitlin Super B Factory Trigger Workshop

22. An upgrade path from BABAR to SuperBABAR EMC  Liquid Xe scintillation or fast, rad-hard crystals (LYSO) DIRC  Faster, pixelated readout SuperBABAR SVT 5 layers of double-sided striplets 2 layers of thin pixels + 3 layers of thin pixels Tracker  4 layers of thin double-sided Si + New trigger and DAQ system BABAR D. Hitlin Super B Factory Trigger Workshop

23. Projections depend heavily on the luminosity term Cross sections: • BB: 1 nb 1010BBpairs/year • uds: 1.6 nb, c: 1 nb • leptons (m, t): 0.78 each • recognizable Bhabhas: ~50nb • The Level 1 trigger rate: • BABAR/PEP-II projections show that the hardware trigger rate will be dominated by luminosity-related interactions at luminosities above 1034 . • At 7x1035, this gives a rate for a BABAR-like hardware trigger of about 50K events per second. Half of these are scaled Bhabhas. There are ~ 6K beam background-like events per second. • Unless we are clever we might have to cope with a ~100K/second L1 rate ! • Event size ~50K (~2X BABAR) • How well must we know the efficiency of each trigger line? • Precise absolute branching ratios may not be of extreme importance Scaled from GPDF in Hawaii D. Hitlin Super B Factory Trigger Workshop

24. The challenge • Design a trigger D/A system with a silicon tracking plus fast calorimeter trigger which has all the virtues of a classical e+e- trigger in a much more challenging environment • Store and analyze the data efficiently • Find New Physics D. Hitlin Super B Factory Trigger Workshop