UCSD Physics Activities on BaBar Progress Report to DOE: 2004

1. UCSD Physics Activities on BaBarProgress Report to DOE: 2004 Vivek Sharma University of California, San Diego

2. Prize For Best PhD Dissertation At a US University or Laboratory Citation: "For his role in the development of the tools needed for the analysis of B factory data, including the tFIT program, a unique and comprehensive fitting framework for time-dependent analyses. The tools he developed played a key role in the observation of CP violation in the B system by the BaBar collaboration. These tools will be essential to the ongoing program of work as the B factories continue to probe the origins of CP violation." PhD Thesis Advisor : Vivek Sharma 2004Mitsuyoshi Tanaka Dissertation Awardto Shahram Rahatlou University of California, San Diego

3. Outline of This Talk • BaBar highlights from this summer • Physics responsibilities and activities of UCSD physicists • UCSD Physics Objectives • Brief description of analyses pursued • Outlook • Enclosed with this document, for more elaborate reading: • David MacFarlane’s comprehensive review of ICHEP04 results from Babar and Belle • Vivek Sharma’s review talk on Rare B and D Decays at “Physics at Meson factories”, Frascati 2004. • Daniele delRe’s talk on Vub at ICHEP04, Beijing • Daniele delRe’s talk on Recoil-side physics at SuperBfactory workshop • Shahram Rahatlou’s review talk on sin2+ at DPF 2004 • Shahram Rahatlou’s talk on BaBar Event Reconstruction at DPF2004

4. * VtdVtb * VudVub a g b * VcdVcb Reminder Of The Terminology

5. 3 x design ~245 million BB pairs Summary Of BaBar Physics Productivity PEP-II machine continues to Excel ! BaBar quick to analyze and provide public results

6. BABAR B0K+ B0K+ 4.2 CPV signal enhanced BaBar Physics Highlights: Discovery of Direct CPV in B Decays  B B 2 2 f f BABAR First Observation (4.2s) Belle 3.9s Confirms at ICHEP04 Average

7. B (cc) KS (CP odd) modes BaBar Physics Highlights: Precision Measurement of sin2 Just Three years after its discovery CPV in B J/K0 is now a precision measurement B J/ψKL (CP even) mode sin2β = 0.722  0.040 (stat)  0.023 (sys) (2002 measurement: sin(2β) = 0.741±0.067±0.034)

8. CP asymmetries in Penguin Dominated B Decays (sin2eff) Penguin dominated modes sensitive to New Physics in the loop Without NP, expect “sin2” from penguin modes to be same as “sin2” from K0 modulo corrections due to (small) contribution from other SM amplitudes Difference is 2.7 Adding Belle results, difference between measured sin2 from s-penguin and charmonium modes grows to 3.6 ??

9. 3.2s 5.2s BaBar Physics Highlights: No CPV Seen in B0+ - BaBar > 3 discrepancy between BABAR & Belle Belle

10. Tree Penguin BaBar Physics Highlights: Towards Precise Measurement of Angle  • In absence of Penguin contributions, can measure CKM angle  from B0+ - or + - • BaBar measurements show that B0+ - is most suited for measuring  since • Penguin pollution is more under control (limits on B00 0, B-- 0) • The decay is dominated by one helicity amplitude  well defined CP state • Rate is reasonably large; first observation by BaBar (2003) Run1-3 data (122M BB) B0+ - 314±34 Signal Events (205 tagged) Longitudinal polarization frac. fL=1.00±0.02 Clean tags

11. Can Measure  more precisely Time-dependent CP Asymmetry BaBar Physics Highlights: Towards Precise Measurement of Angle 

12. BaBar Physics Highlights: Measurements of Vub In Semileptonic Decay Exclusive modes LEP Inclusive studies*

13. Physics Analysis Focus of The UCSD-BaBar Group UCSD-Babar group led the measurements of sin2 from B  charmonium modes between 1998-2003. These measurement has now become “routine”. UCSD group has moved on more challenging measurements. With the large data set BaBar is accumulating our major physics focus is now on: • Search for the decay B0 D0 K0 and measurement of CKM angle  by time-dependent CP asymmetry. • Developing massive samples of fully reconstructed B mesons for Recoil side B meson decay studies. The aim is to measure CKM element Vub from inclusive and exclusive bul decays • Probe CP violation in Penguin decays such as • Measurement of production ratio Brief Description of UCSD analysis follows

14. UCSD Physics Activities On Babar • David MacFarlane (PI): • Main author of BaBar 2002 Phys. Rev. (D) on Measurement of B oscillation and CP violation. • Measurement of inclusive bu l spectrum (with Student Ed Hill) • Search for Time-dependent CP asymmetry in B0 KS KS KS (with student Haleh Hadavand) • Measurement of production ratio (with student Haleh Hadavand) • BaBar Spokesperson

15. UCSD Physics Activities On Babar • Vivek Sharma (PI) : • led, as co-convener, the BaBar physics group on Exclusive B decays to Open charm ( BRECO group) between 1999 –July 2004. All analyses involving exclusive hadronic B  Charm reconstruction are developed in this group. Guided thru publication 9 PRL, 2 PR(D)RC and 2 PR(D) articles and multiple conference papers including 11 papers at ICHEP04 in Beijing. • Physics goals of the BRECO group include: • exploration of decay modes capable of measuring CKM angle  and sin2+ • Decay dynamics in hadronic B decays to charm • Spectroscopy of new charm mesons from their production in B decays • Develop large sample of fully reconstructed B mesons for measuring inclusive properties of the recoiling B meson. This paradigm shifting enterprise is already contributing to several key measurements in B decays such as Vub and measurement of photon spectrum in b s  decays . • Breco group oversees the physics analysis of about 80 BaBar physicists from US, France, Italy and Germany. It is one of the largest analysis groups in Babar. • Guiding role in BaBar observation of CP violation (sin2) in BJ/K0 . Main author of the 2001 and 2002 PRLs on measurement of Sin2 • Member (since 2002) of the Babar Publication Board.

16. UCSD Physics Activities On Babar • Shahram Rahatlou (Post-doc): • Major contributions to BaBar observation of CP violation in B decays to charmonium (e.g. BJ/K0). Tools and samples he developed (BrecoUser, tFIT etc) are still used in many CP violation studies. Awarded The 2004 APS Tanaka prize for the best PhD thesis at a US university or Laboratory. • BaBar Event Reconstruction Manager since Jan 1, 2004. • The reco manager is Responsible for development and deployment of the common aspects of reconstruction, including the reconstruction geometry & alignment calibration model & code, the overall organization of reconstruction executables, and the reco infrastructure packages. He is responsible for the system-specific aspects of the reconstruction code to the level desired by the specific system managers. The reco manager is responsible for the technical aspects of the reco software within the five systems and their integration into the whole. • Shahram brings a unique and comprehensive knowledge of Babar analysis tools, computing and physics to this job. His leadership has been crucial in ensuring prompt and high quality event reconstruction and allowed BaBar to analyze the data collected till the end of Run 4 in mid July and present results based on it at the Beijing ICHEP04 in mid-August ! • Developing the time-dependent CP asymmetry analysis of B0 D0 K0for measurement of sin2+ and . First results presented at ICHEP04 (hep-ex/0408052 ).

17. UCSD Physics Activities On Babar • Daniele delRe (Post-doc): • Primary physicist in the development of large sample of fully reconstructed hadronic B decay (Semi-exclusive B sample). • Co-convener of the “Recoil Side Physics” forum in BaBar in charge of coordinating and assisting in the development of a variety of inclusive measurements in the decay of the B meson recoiling against the fully reconstructed B meson (in the semi-exclusive sample). • Led the pioneering measurement of Vub by measuring the hadronic mass spectrum in b u l from the recoil side B. Results published in PRL (92) 07180, 2004. Updated Vub results with more data (x 3) and improved observables in preparation. • Key contributor in the migration of BaBar analysis software to the new computing model implemented since September 2003. Technical coordinator of the data and MC “skims” and tagbits for the Breco and Semileptonic Physics groups. • Appointed co-convener of the Breco Physics group in August 2004.

18. UCSD Physics Activities On Babar • Haleh Hadavand (PhD. Student): • Member of BaBar charge Particle tracking group with important contributions to the Drift chamber calibration and Ks reconstruction studies. Her tracking efficiency studies provide the official BaBar “recipes” for all analyses involving branching fraction measurements. • Primary author of the measurement of the B+/B0 production ratio from the (4s) Meson using B+J/ K+ and B0J/  Ks decays  to be published in Phys. Rev. (D). • Primary author of the measurement of time-dependent CP asymmetry in penguin dominated mode B0 KS KS KS . • Edward Hill (Ph.D Student): • Drift chamber calibration. • Migration of BaBar analysis software related to Semi-leptonic decay physics to the new computing model and data-mining for the entire semi-leptonic physics group. • Developed algorithms for bcl background rejection for Semileptonic physics group • Measurement of Vub from inclusive semi-leptonic decay using the photon energy spectrum from b s  decays.

19. UCSD Physics: Probing CKM Angle  Look for B decays with 2 amplitudes with relative weak phase  Direct CP Asymmetry  Angle 

20. Angle  from B±DK±: Critical Requirement • Relative size of the 2 B decay amplitudes Crucial for interference and rate of CPV • Want rb to be large to get more interference  Large CP asymmetry • Diff. between rb=0.1 and rb=0.2 substantial for precision on  • Theory cannot calculate r reliably must measure experimentally Color suppression: Fcs  [0.2,0.5] Left side U.T.: Ru 0.4 Expected range

21. 90% 68% g [deg] Measuring rb By Reconstructing B±DK± in different D final states Bottomline : With low value of rb likely, need to consider multiple observables sensitive to CKM angle  B0D0K0

22. Measurement of sin(2b+g) with B0/B0 D(*)0K(*)0 • Interference between decay and mixing • Advantages: • Expected large asymmetries • Time-dependent measurement with K0  KS • Probe rB in self-tagging final state K*0K-p+ • Disadvantages: • Color suppressed decays: Smaller branching fractions than D(*)p • Possible competing effects from Doubly-Cabibbo-suppressed D0 decays Strong phase difference

23. Study of B0/B0 D(*)0KS Decays 124 million BB hep-ex/0408052 N=64 ± 11 Cannot distinguishB0 from B0 Hidden strangenesswith KS in final state D0 Sidebands N=11 ± 4 First Evidence Shahram Rahatlou & Vivek Sharma

24. No Signal inVub mediatedDecay Self-Tagging B0 D0K*0 and limit on rB 124 million BB Vcb transition Charge correlation toseparate B0 from B0 N=45 ± 9 Vub transition Preliminary Results based on more data and refined analysis technique forthcoming; targeted for publication in early 2005.

25. New Idea: Measurement of |Vub| From Semileptonic B Decays recoiling against (large samples of) Fully Recostructed B mesonsCapitalizes on UCSD Expertise in B meson Reconstruction (Breco Samples  SemiExcl Samples) Measurement of | Vub | From Inclusive and Exclusive Final States

26. Beginning of an Experimental Paradigm Shift in Vxb Measurements in Semileptonic Decays at B Factories • Hermiticity, so vital for SL measurements is not the best feature of Belle/ Babar detectors due to intrusion of machine into detector • But B-factory detectors recording ever increasing samples of BB pairs (> 250 Million BB recorded already  1000 Million soon) • At the price of modest efficiency (4%), can fully reconstruct one B decay into all hadronic final states (Breco) and examine the other (recoiling) B decay • This “Recoil side” studies perfectly suited for many Vxb studies • Much “cleaner” and more powerful than neutrino reconstruction a la CLEO • This is the most promising way for the future Vub and other Semileptonic measurements

27. In this (rare) case all particles were sprayed within fiducial volume of detector The Perfect (4S) Event: Example of Recoil Side Analysis Replace this with your Favourite Vxb mode e.g: b  u l

28. Hadronic B Decay Reconstruction Rate: 4000/ fb-1 80fb-1 World’s largest sample of Fully reconstructed B mesons  1,000,000 and growing! S/B~0.3 Full B reconstruction on one side provides kinematic constraints and Background reduction allowing Important inclusive B decay Measurements like Vub. Require Lepton (p*>1.0GeV) S/B~2.5 Largely the work of UCSD postdoc Daniele delRe

29. Xu n l p D* Xu B B Y(4s) Y(4s) Breco Brecoil D* Y(4S) B Candidate Mass l p n Recoil Side B Decay Rate Measurement : Technique Can measure Neutrino 3-vector Reco side Recoil side missing mass squared • MX reconstruction • Kinematic constraints to • improve MX resolution

30. Resulting MX Spectrum clearly separates b c l  & b  u l

31. ucsd Measurements of |Vub| from b u l Daniele delRe & Ed Hill (UCSD) Most Measurements are systematic limited or model dependent. The Recoil side method has the best potential for precise measurement of |Vub| with larger data samples already available

32. B±p0ln B0rln B±r0ln B0wln Exclusive Final States: B (p,r,w) ln In Breco Sample Approach similar to the inclusive analysis but resonances are exclusively and fully reconstructed on recoil side. We measure, very cleanly and over large kinematic range: As Lattice calculations become more robust, measurement of B l rate over large kinematic range may lead to one of the best measure Vub precisely. Experimental measurement is statistics limited

33. Accepted in PR(D) RC Haleh Hadavand David MacFarlane

34. Determining KS+ - Tracking Efficiency Correction Precise data and MC comparison todetermine efficiency correction in bins of trans. momentum (Pt) and polar angle  for various drift chamber high voltage conditions during data taking periods. Algorithm and “recipe” is now a BaBar standard. Hadavand & MacFarlane

35. y x p+ p- p- p+ K0s p+ K0s K0s ~30 mm Beam ~200 mm Inflated Beam CPV In Pure s-Penguin Decay B0KS KS KS • New probe of CPV in s-penguin decays, clean signal • Perform Ks and B vertexing using 5 layer Silicon tracker (technique pioneered by BaBar and tested on BKs0 sample). Often one of three Ks decays inside SVT. • Reconstructed B vertex resolution sufficient for time-dependent CPV measurement a la B  J/ KS • First analysis of its kind, currently “blind”, expect public results and publication by early 2005. • CPV precision expected to be statistics limited, will improve with rapidly accumulating BaBar data KS p- KS ~4 mm KS 90 10 signal after bkgnd subtraction Hadavand

36. UCSD-Babar Physics Outlook • Golden years of Babar physics productivity enabled by excellent PEP-II running and success of the new Babar computing model • UCSD-Babar physicists continue to play a key role in BaBar productivity by contributing to physics and computing leadership, service tasks and by performing outstanding and topical analyses. • The UCSD-Babar group’s planned near-term physics focus is on • Strategies for measurement of , particularly B0/B0 D(*)0K(*)0 • Determination of |Vub| with the novel recoil side method • Inclusive bulmeasurements • Exclusive bulfinal states (exploring new ideas such as that of Grinstein & Pirjolhep-ph/0404250) • Innovative new probe of CPV in s-penguin modes with B0 KSKSKS