Status Report on IFR Physics Issues

1. Status Report on IFR Physics Issues Jeff Richman UC Santa Barbara IFR Barrel Replacement Workshop, November 15, 2002

2. Physics Session Agenda

3. Outline • Charge, people, organization • Questions to address • Physics program for the IFR • Benchmark detector/absorber layouts

4. Most relevant part of the charge to IFR Replacement Review Committee for physics studies The committee should advise on improvements that can be made to the muon identification in the barrel IFR based on the foreseeable physics goals of the experiment. In particular, this includes improvements in pion rejection due to increased material inserted in the barrel gaps in place of sensing layers. The committee should revisit the issue of muon identification/pion rejection efficiency versus KL identification/veto efficiency and provide a clear statement of priorities for the IFR.

5. People involved • David Lange (LLNL) [consultant to the committee] • Gianluca Cavoto (Rome/Princeton): MC studies • Ajit Mohapatra (U. Wisconsin): MC studies • J.D.R. • People working on specific studies • Joerg Stelzer (SLAC), Danning Dong (SLAC): Dsmn • Oliver Buchmueller (SLAC): data vs. MC comparisons • Bryan Dahmes (UCSB): KL information • Jeff Berryhill (UCSB):BK(*)l+l- • Gabriella Sciolla (MIT): tagging in BJ/y K • Tina Cartaro (Naples): IFR endcap studies • Urs Langenegger (SLAC): KL veto in BXu l n

6. Web page for collecting information on physics studies for IFR http://www.slac.stanford.edu/BFROOT/www/Detector/IFR/lange/IfrBarrelUpgrade/ We already have a full page of links to new plots, as well as previous studies. There are lots of basic plots related to muon ID. Much of the hard work is being done by David Lange,Ajit Mohapatra, and Gianluca Cavoto. We have been meeting Monday mornings at 8:30. See IFR Improvement Hypernews.

7. Absorber in front of the IFR

8. Basic features of the IFR: absorber traversed to live chamber in fullsimulation • Current barrel • Old endcap • MC study; chamber inefficiencies included

9. Basic features of the IFR: acceptance vs. f folded distribution

10. What questions should we ask? • What are the physics measurements that motivate and justify the IFR Barrel replacement? • For important processes with muons, how much absorber would make a significant difference in improving the quality of the measurement? • What are the minimal requirements for KL ID? Can a KL veto be effective? • What are the requirements on detector efficiency, resolution, and granularity? ….and get the answers by Dec 8

13. What about tagging for CP measurements? • Now have study by Gabriella Sciolla (http://babar-hn.slac.stanford.edu:5090/HyperNews/get/sin2beta/488/1.html) • set the muon ID efficiency to zero • retrain the tagger and then test on an independent sample • Go from total Q=30.3% to Q=29.1% • Get partial recovery into other tagging categories

14. Approaches • Study some specific processes of interest. Understand the role of muon ID and fake-muon backgrounds. • Generic approach: estimate m efficiencies and pm fake probabilities vs. momentum and cos(q). • Compare different ``benchmark’’ detector layouts.

15. Issues for new detector/absorber layouts • The difficulty in replacing the detectors in Layer 19 presents a very serious problem, since we effectively lose 10 cm (0.6 lint) of absorber before we even start with our design. • Replacing one detector layer with 2.2 cm brass restores only 0.15 lint need to replace 4 layers just to break even! • Note: CLEO has 3 detector triplets following lint=3, 5, 7. • In spite of this, I think that the most important physics issue is high m detection efficiency. • Presumably, we should retain detectors in layer 1 for track linking with the DCH. However, all BaBar muon selectors currently require at least 2l, so m detection before this amount of material is not very important. • Currently, KL ID requires hits in two successive layers.

16. Benchmark Designs • D. Lange, L. Cavoto, T. Cartaro, and J.D.R. have decided on 6 benchmark designs to answer some basic questions. Can more material be added? Earthquake issues…

17. Benchmark Design #1 (add 5 absorber layers)

18. Benchmark Design #2 (add 6 absorber layers)

19. Benchmark Design #3 (add 9 absorber layers)

20. Studies Planned for Benchmark Designs • Make material maps of each design: l vs. cos(q). • Make detailed performance plots for two separate regions in cos (q). • Barrel/Fwd endcap overlap region: 0.7< q<1 radian • Barrel region: 1< q<2 radians

21. Conclusions • We have a lot to do in a very short time, but results will start appearing rapidly. • We need to get your input now. • Thanks to all who are helping out!

22. Backup Slides

23. Performance Plots • Muon efficiency vs. p • Prob(pm) vs. p • Prob(pm) vs. muon efficiency in slices of momentum: 0.5<p<1.0 GeV/c; 1.0<p<1.5 GeV/c; 1.5<p<2.5 GeV/c; p>2.5 • Dl distributions: m and p as separate curves on one plot. Make plots in same momentum slices as given above. • KL efficiency vs. p • Scatterplots of Dl vs. cos(q) for m and p samples. Use same momentum slices as given above. • If possible: p fake-rate decomposition vs. p • pm decays before and within the IFR • p punchthroughs or sailthroughs (no decay)

24. Other Issues • We hope to perform some data vs. MC comparisons (m,KL efficiencies, pmfake probs) using data samples from early 2000, when the RPC efficiencies were reasonably high. • A question I would like to answer: How much absorber would we need to add to the IFR before the fake prob from non-decaying pions is reduced to one-half the fake prob from decaying pions?

25. Basic features of the IFR: absorber traversed to live chamber with perfect chamber efficiencies • Current barrel • Old endcap • MC study

26. Basic features of the IFR: absorber traversed to live chamber w/o L19 • Current barrel • Old endcap • Layer 19 removed • Perfect efficiency for other chambers

27. Benchmark physics processes: muons • There are many processes with muons that will important to the BABAR physics program for many years. • B D* ln: largest branching fraction of any B decay, |Vcb |, intermediate momentum spectrum; lint =5 prob. sufficient. • Brln (hard lepton spectrum), Bp l n, | Vub |lint >5 ? • BK(*)l+l- (efficiency is very important); BXsl+l- • BXu ln inclusive, | Vub | (high-p muons, contin. bkgnd.) • e+e- Ds*Dsg; Ds mn (fakes lint >5 ?), fDs • B J/y KS ; J/y l+l- (muon ID barely needed) • We are making the momentum and range spectra (number interaction lengths) for these processes as a function of cos(q).

28. Muon momentum spectra for key modes (see web page for many more)

29. Muon momentum spectra for key modes:cos(q) vs. plab

30. Muon penetration in iron vs. momentum(Geant Toy MC) l=10 l=5

31. Probability for a muon to penetrate L interaction lengths vs. momentum L=2 3 4 5 6 7 8 90%

32. Benchmark physics processes: KL • Currently, the role of KL identification in the BaBar physics program is very limited. • B J/y KL; J/y l+l- High momentum KL !!! • In discussions with AWG convenors, processes with KL final states have usually not been listed as part of the planned physics program. • There may be analyses in which it is useful to veto KL’sin order to improve the correspondence between missing energy and neutrino momentum. We need to investigate this. What is efficiency at low p??? • My own view is that we should try to maintain some level of KL efficiency unless this results in measurable degradation in muon ID performance. For any new detector design, we should monitor its effect on the benchmark decay B J/yKL .