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

SCIPP: Major Highlights Major physics contributions include: Leading role (Lockman) in BaBar’s discovery of D 0 mixing Major role in measurement of |V td | 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

Students Post Docs Senior/Faculty Tim Beck [*] Juergen Kroseberg [1] Al Eisner [2] Christian Flacco [*] Lei WangBill Lockman Joel MartinezBruce Schumm Luke WinstromAbe Seiden [*] Graduated this year [1] Now on faculty at U. Bonn [2] Not supported by this grant Personnel

Final BaBar Data Sample RUNDURATIONACCUMULATED SAMPLE RUN I 01/00  10/00 20 fb –1 RUN II 01/01  06/02 61 fb –1 RUN III 11/02  08/03 32 fb –1 RUN IV 09/03  06/ fb –1 RUN V 04/05  08/ fb –1 RUN VI01/07 – 12/07 79 fb -1 TOTAL Y(4S)01/00 – 12/07425 fb -1  (3S) 01/08 – 03/08 30 fb -1  (2S) 03/08 – 04/08 14 fb -1 Off-PeakInterspersed 50 fb -1 GRAND TOTAL01/00 – 04/ fb -1 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.

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

Major Service Contributions Tasks Wang (Post Doc)Drift Chamber Residuals Winstrom (Grad)Prompt Reconstruction Manager6/07-12/07 Martinez (Grad)SVT Commissioner6/07-11/07 Eisner (Volunteer)SVT Online Data QualityOngoing Leadership Kroseberg (Post Doc)Radiative Penguin ConvenerTo 1/08 Eisner (Volunteer)Trigger/Filter/Luminosity ConvenerOngoing Schumm (Faculty)Speaker’s Bureau9/06-3/08

Refinement of Drift Chamber Time-to-Distance Relation DOCA ANGLE Hit position derived from time of signal arrival on wire Need position and uncertainty for track fitting 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

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

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 (V ts, V td and supports V ub measurement) B meson dynamics (input to extraction of V ub from B  X u l b motion Figure thanks to J Walsh, INFN-Pisa

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! qq + ττ BB XSγXSγ Cont. Signal selection

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

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

Fate of “Other” (Low-Energy) Photon Below 30 MeV (lost)13.9% Interact before DIRC (lost)5.0% Pass through CAL (lost)0.8% Interact in DIRC, and lost5.0% Interact in DIRC, and found8.0% Convert in CAL, and lost6.1% Conver in CAL, and found61.2% TOTAL100% 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! 00  that fakes signal “other”  B/Bbar Backgrounds

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). Fully Inclusive Measurement of  (b  s  ): Contributions and Target

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

V td Penguin physics accesses V td via independent diagram… MIXING: X d ~ 0.2  SM rate of order x  B PENGUINS: Overall suppression of  SM rate of order x  B New physics likely much more visible in b  d  width  Comparison of Penguin and Mixing measurements of |V td /V ts | is a sensitive testbed for new physics b  d  and New Physics (d)

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 B d /B s mixing, ratio of d  and s  observables directly sensitive to |V td /V ts | 2  0.04 b  d  Measurements

B  (  /  )  (a.k.a. b  d  “exclusive”) (and  ) Current Results (x10 6 ) BaBar (Run I-V) BELLE PRL 98, PRL 96, B +   +  1.1  0.3   0.4  0.1 B 0   0  0.8  0.2   0.4  0.1 B 0   0  < 0.8 <1.0 Since  0 has yet to be found, optimize Run I-VI analysis for this mode. ~8% “theory” error from annihlation, form factor

Reject continuum with “Boosted Decision Tree” multivariate discriminator with 55 input variables (validate with B  K *  sample) Reconstruct B 0   0   0   +  - B +   +   +   +  0 B 0   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 M ES  event momentum balance

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

But luck is not with us… Current and New Results (x10 6 ) Comparison PRELIMINARY; NOT PUBLIC BaBar Run I-V BaBar Run I-VI PRL 98, PRD to come… B +   +  1.10  0.34   0.42  0.25 B 0   0  0.79  0.21   0.23  0.11 B 0   0  0.40  0.22   0.26  0.07 Restricting new analysis to Run I-V shows that: Significance improved for B 0   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)

Fit to B   Sample

b  d  “semi-inclusive” measurement Reconstruct 7 b  d  final states, along with corresponding b  s  states. Restrict to mass range 0 < M had < 1.8 GeV/c 2 (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 

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

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

Correct for unmeasured modes, m had < 1.8 GeV/c 2  = 1.2  0.2 Ratio of  (b  d  ) to  (b  s  ) in range M had < 1.8 GeV/c 2

Extraction of |V td |/|V ts | where   1 corrects for Possible differences in d  and s  spectrum above M had = 1.8 GeV/c 2 (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%)

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 )

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

SCIPP On to charm physics…

Initial plans: 1)X s  fragmentation has been measured well, and correction factors derived. We can apply those correction factors to X d  and see how K changes. 2)Alternative X s  model based on R S  for ~10 resonances developed; simulate corresponding R d  and see how K changes.