1 / 31

BaBar @ SCIPP

BaBar @ SCIPP. Part I: Introduction, Service, Radiative Penguin and (3S) Physics. DOE Site Visit June 10, 2008. Bruce Schumm, SCIPP BaBar P.I. BaBar @ SCIPP: Major Highlights. Major physics contributions include: Leading role (Lockman) in BaBar’s discovery of D 0 mixing

emera
Download Presentation

BaBar @ SCIPP

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BaBar @ SCIPP Part I: Introduction, Service, Radiative Penguin and (3S) Physics DOE Site Visit June 10, 2008 Bruce Schumm, SCIPP BaBar P.I.

  2. BaBar @ SCIPP: Major Highlights • Major physics contributions include: • Leading role (Lockman) in BaBar’s discovery of D0 mixing • Major role in measurement of |Vtd| and search for new physics in b  d  transition (very rare!) • Pioneering work in sub-percent charm-sector CP asymmetries • Major role in “legacy” measurement of b  s  transition

  3. Personnel StudentsPost DocsSenior/Faculty Tim Beck[*] Juergen Kroseberg[1] Al Eisner[2] Christian Flacco[*] Lei Wang Bill Lockman Joel Martinez Bruce Schumm Luke Winstrom Abe Seiden [*] Graduated this year [1] Now on faculty at U. Bonn [2] Not supported by this grant

  4. Final BaBar Data Sample Over 7-8 years, BaBar accumulated roughly 0.5 ab-1 of data, mostly at the Y(4S). The analyses reported here all incorporated data through at least run V.

  5. H-Cal/ (IFR) E-Cal (EMC) DIRC Drift Chamber (DCH) SVT SCIPP Service to BaBar Traditionally, involved in SVT, DCH design and construction…

  6. Major Service Contributions Tasks Wang (Post Doc) Drift Chamber Residuals Winstrom (Grad) Prompt Reconstruction Manager 6/07-12/07 Martinez (Grad) SVT Commissioner 6/07-11/07 Eisner (Volunteer) SVT Online Data Quality Ongoing Leadership Kroseberg (Post Doc) Radiative Penguin Convener To 1/08 Eisner (Volunteer) Trigger/Filter/Luminosity Convener Ongoing Schumm (Faculty) Speaker’s Bureau 9/06-3/08

  7. Refinement of Drift Chamber Time-to-Distance Relation 2D distributions shows that error depends on entrance angle as well as “DOCA” Lei Wang: Characterize residual error (uncertainty) as a function of both DOCA and entrance angle; re-do track reconstruction DOCA ANGLE • Hit position derived from time of signal arrival on wire • Need position and uncertainty for track fitting

  8. Number of drift chamber hits per track, improved residual characterization minus default characterization Drift Chamber Time-to-Distance Relation Improvements • Improvements: • More DCH hits per track (see plot at right) • Improved by 3% overall and by 15% for pt < 200 MeV/c • 12% decrease in unused hits

  9. Radiative Penguin Physics The SM transition is high order (two weak plus one EM vertex… So new physics can enter at leading order • Also: • CKM parameters (Vts, Vtd and supports Vub measurement) • B meson dynamics (input to extraction of Vub from B  Xu l  b motion Figure thanks to J Walsh, INFN-Pisa

  10. qq + ττ BB XSγ Fully Inclusive Measurement of (bs) Winstrom, Eisner, Schumm (with SLAC, Notre Dame, Oregon) • Find high-energy photon • Use event shapes and lepton tag to suppress continuum background • Look for other 0 () photon, or extended clusters, to suppress B background • Very challenging! selection BB Cont. Signal

  11. Direct searches (LEP) But also rewarding… SUSY Extra Dimensions B  s constraints MSSM Constraints Leading indirect constraint on several new physics scenarios

  12. % of total Error Statistitical Model Systematic Update to Runs I-V Sample Run I-II Result (Phys.Rev.Lett.97:171803,2006 ) Br (BXsg) = (3.67  0.29  0.34  0.29) x 10-4 Run I-V analysis projecting 3.4% statistical error (run I-II is 7.9%)  Must work hard to reduce systematic and model errors!

  13.  that fakes signal B/Bbar Backgrounds 0 “other”  Reduce B backgrounds (blue) by finding “other” photon and reconstructing 0() decay How often is “other” (low-energy) photon missed? Answer: About 2/3 of time. Need to understand 1/3 loss with great precision! Fate of “Other” (Low-Energy) Photon

  14. Fully Inclusive Measurement of (bs): Contributions and Target Working with Calorimeter group to understand losses in DIRC, and in CAL (cracks, overlap with other clusters, etc.) Also working on smaller but significant background from anti-neutrons (how to constrain with antiprotons from   p?) Also doing basic coding and general infrastructure support for analysis… Group targeting late summer for result (updated branching fraction plus first and second photon energy moments).

  15. Vtd (d) (d) (d) (d) bd and the CKM Parameter Vtd Measurement of the bd transition provides direct sensitivity to Vtd Accurate measurement of Vtd provided by Bd mixing rate; normalize to Bs mixing rate to minimize hadronic uncertainties (CDF, D0; Phys.Rev.Lett. 97 (2006) 242003 ) (d) (d)

  16. Vtd (d) (d) (d) (d) bd and New Physics (d) (d) Penguin physics accesses Vtd via independent diagram… MIXING: Xd ~ 0.2  SM rate of order 10-1 x B PENGUINS: Overall suppression of 10-5 SM rate of order 10-5 x B New physics likely much more visible in bd width  Comparison of Penguin and Mixing measurements of |Vtd/Vts| is a sensitive testbed for new physics

  17. bd Measurements Two approaches; both avoid hadronic uncertainties by normalizing to corresponding bs process: Exclusive measurement of Br(B [/])/Br(BK*) Martinez, Kroseberg, Schumm (with CalTech) Semi-Inclusive measurement of (bd)/(bs) Beck (thesis), Schumm (with Imperial College and Edinburgh) As for Bd/Bs mixing, ratio of d and s observables directly sensitive to |Vtd/Vts|2  0.04

  18. (and ) B  (/) (a.k.a. b  d “exclusive”) ~8% “theory” error from annihlation, form factor Current Results (x106) BaBar (Run I-V) BELLE PRL 98, 151802 PRL 96, 221601 B+  + 1.1  0.3  0.1 0.6  0.4  0.1 B0 0 0.8  0.2  0.1 1.3  0.4  0.1 B0 0 < 0.8 <1.0 Since 0 has yet to be found, optimize Run I-VI analysis for this mode.

  19. Reject continuum with “Boosted Decision Tree” multivariate discriminator with 55 input variables (validate with B  K* sample) Reconstruct B0  0 0  + - B+  + +  + 0 B0  0 0  + - 0 (rejection of kaons from B  K*; K*  K is critical) Use the two largely uncorrelated “fit” discriminating variables: E  event energy sum MES  event momentum balance

  20. Boosted Decision Tree selection much cleaner: B0  0 analysis; old (Run I-V) analysis B0  0 analysis; new (Run I-VI) analysis

  21. But luck is not with us… Current and New Results (x106) Comparison PRELIMINARY; NOT PUBLIC BaBar Run I-V BaBar Run I-VI PRL 98, 151802 PRD to come… B+  + 1.10  0.34  0.09 1.20  0.42  0.25 B0 0 0.79  0.21  0.06 1.03  0.23  0.11 B0 0 0.40  0.22  0.05 0.49  0.26  0.07 • Restricting new analysis to Run I-V shows that: • Significance improved for B0  0 • Run VI data has unlucky background fluctuation in B+ • Collaboration needs to decide whether to use these or stay with old numbers (probable: these will supplant old numbers via a PRD article)

  22. Fit to B   Sample

  23. b  d “semi-inclusive” measurement Reconstruct 7 b  dfinal states, along with corresponding b  s states. Restrict to mass range 0 < Mhad < 1.8 GeV/c2 (S/N issues) More signal, but no explicit use of intermediate resonance structure  higher backgrounds Measure more of partial width  lower (?) and independent systematics First time ever tried for b  d

  24. FIT… Breakdown of Measured/Unmeasured Width Nominal Signal MC 1.0 < Mhad < 1.8 1.8 < Mhad (,,K*) XS Increase measured fraction of bd width from ~10% to ~30% # bodies UNMEASURED Xd MEASURED # 0 Mhad

  25. Preliminary – Not Yet Public Continuum background bs + MisID background Fit to seven bd modes in high-mass region (most challenging of four fitting regions) (Statistical errors only, but dominated by bd statistics)

  26. Correct for unmeasured modes, mhad < 1.8 GeV/c2  = 1.2  0.2 Ratio of (bd) to (bs) in range Mhad < 1.8 GeV/c2

  27. Extraction of |Vtd|/|Vts| • where   1 corrects for • Possible differences in d and s spectrum above Mhad = 1.8 GeV/c2 (should be small) • Annihilation diagrams effects (as for / ) • Quark/hadron duality assumption But: once theorists have done their work, should provide a better-than 20% measurement of |Vtd|/|Vts| (global /  constraint is about 13%)

  28. Search for Dark Matter Candidates at the (3S) • Using 30 fb-1 of e+e-  (3S) • Luke Winstrom (thesis topic), Al Eisner, Bruce Schumm; with Steve Sekula (Ohio State postdoc) • Develop tagged sample of (1S) decays through decay chain (3S) (1S) + + + - • Look for (1S)  invisible; possible sources include SUSY, generic light dark matter • Limit with 30 fb-1 of e+e-  (3S) expected to be better than 5x10-4 (Belle limit with 3 fb-1 is 2.5x10-3)

  29. Irreducible Background: (3S)  (1S) + + + - with leptons outside of fiducial volume. BOTH MUONS FOUND l+ + l- ONE MUON FOUND Luke Winstrom: Asymmetric detector allows geometrical inefficiency to be constrained by looking at difference between one- and two-lepton cos distributions Goal: Preliminary result by late summer

  30. BaBar @ SCIPP On to charm physics…

  31. Initial plans: • Xs fragmentation has been measured well, and correction factors derived. We can apply those correction factors to Xd and see how K changes. • Alternative Xsmodel based on RS  for ~10 resonances developed; simulate corresponding Rd and see how K changes.

More Related