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Probing the Standard Model Frontier with B Physics at CDF

Probing the Standard Model Frontier with B Physics at CDF. Alessandro Cerri. Synopsis. The Big Picture Why B physics at the TeVatron is a good bet Tools of the trade CDF: detector and DAQ SVT: the CDF key to B physics Selected examples Hadronic Moments in b cl (V cb )

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Probing the Standard Model Frontier with B Physics at CDF

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  1. Probing the Standard Model Frontier with B Physics at CDF Alessandro Cerri

  2. Synopsis • The Big Picture • Why B physics at the TeVatron is a good bet • Tools of the trade • CDF: detector and DAQ • SVT: the CDF key to B physics • Selected examples • Hadronic Moments in bcl (Vcb) • Bs Mixing (Vtd and new physics) • Perspectives • Conclusions

  3. Qualitative to Quantitative Like other areas, CKM physics can now precisely probe the Standard Model

  4. B physics: precision probe of SM and beyond! TeVatron contribution is critical!

  5. The Tevatron as a b factory • B factories program extensive and very successful BUT limited to Bu,Bd • Tevatron experiments can produce all b species: Bu,Bd,Bs,Bc, B**, b,b • Compare to: • (4S)  1 nb (only B0, B+) • Z0 7 nb • Unfortunately • pp 100 mb • b production in pp collisions is so large (~300 Hz @ 1032 cm-2 Hz) that we could not even cope with writing it to tape!

  6. Path to New Physics CKM measurements could hint to new physics through discrepancies with SM predictions. How do we get there? • Design/improve the “tools of the trade” • Experimental (detector & techniques) • Theoretical (phenomenological devices) • Measure uncharted properties at the boundaries of our knowledge • Masses • Lifetimes • Branching ratios • Press further ahead and investigate beyond the boundaries: • Mixing • CP asymmetries

  7. CDF and the TeVatron • Renewed detector & Accelerator chain: • Higher Luminosity higher event rate • Detector changes/improvements: • DAQ redesign • Improved performance: • Detector Coverage • Tracking Quality • New Trigger strategies for heavy flavors: displaced vertex trigger COT Si Detector: L00,SVX II, ISL

  8. The CDF 3 level trigger ~2.7 MHz Crossing rate 396 ns clock Detector Raw Data Level 1 storage pipeline: 42 clock cycles Level 1 Trigger • Level 1 • 2.7 MHz Synchromous Pipeline • 5544 ns Latency • ~20 KHz accept rate SVT L1 Accept Level 2 buffer: 4 events Level 2 Trigger • Level 2 • Asynchromous 2 Stage Pipeline • ~20 s Latency • 250 Hz accept rate L2 Accept DAQ buffers L3 Farm Mass Storage (30-50 Hz) SVT: a specialized B physics triggerrequirements • Good IP resolution • ASAP (10 sec) • No Dead Time • @ earliest L2 where silicon data starts flowing • Drop stereo info: 2D tracking • Extensive custom design

  9. s ~ 48 mm Single Hit Road Detector Layers Superstrip …and a successful endeavor! • SVT is capable of digesting >20000 evts/second to identifying tracks in the silicon • CDFII has been running it since day -1 • The recipe uses specialized hardware: • Clustering • Find clusters (hits) from detector ‘strips’ at full detector resolution • Template matching • Identify roads: pre-defined track templates with coarser detector bins (superstrips) • Linearized track fitting • Fit tracks, with combinatorial limited to clusters within roads

  10. Benchmarks

  11. What was known about non--produced b (PDG’04)

  12. Measure: Branching Ratios First-time measurement of many Bs and b Branching Fractions http://www-cdf.fnal.gov/physics/new/bottom/031002.blessed-bs-br/ Hep-ex/0502044 http://www-cdf.fnal.gov/physics/new/bottom/050310.blessed-dsd/ http://www-cdf.fnal.gov/physics/new/bottom/050310.blessed-dsd/ http://www-cdf.fnal.gov/physics/new/bottom/030702.blessed-lblcpi-ratio_new/ http://www-cdf.fnal.gov/physics/new/bottom/050407.blessed-lbbr/

  13. Lifetimes: fully reconstructed hadronic modes • Testbed for our ability to understand trigger biases • Large, clean samples with understood backgrounds • Excellent mass and vertex resolution • Prerequisite for mixing fits! (B+) = 1.661±0.027±0.013 ps (B0) = 1.511±0.023±0.013 ps (Bs) = 1.598±0.097±0.017 ps Systematics (m) KK http://www-cdf.fnal.gov/physics/new/bottom/050303.blessed-bhadlife/

  14. Improving SM Tools

  15. u c u b l  Closing up on CKM D0  B+   • QCD corrections  uncertainty on the b wave function inside the meson • This is something that can be constrained experimentally!

  16. Improving phenomenological tools: Hadronic Moments • No room for everything… I will focus on one example: • HQET/OPE is a fundamental tool for CKM physics with B mesons. For instance it relates: • BXul to [bul]  Vub • BXcl to [bcl]  Vcb • OPE is “semi-empirical”: parameterizes any prediction in a series expansion of effective operators • Expectation value of these operators is a “universal” property of the theory which can be assessed with concurrent measurements • Example: Vcb (±1%exp±2.5%theo)  Hadronic Moments

  17. Moments-ology Many inclusive observables can be written using the same expansion (same non-perturbative parameters).Thespectral moments: • Photonic moments: Photon energy in b  s  (CLEO) • Leptonic moments: BXcl, lepton E in B rest frame (CLEO, DELPHI, BABAR) • Hadronic moments: BXcl, recoil mass M(Xc) (CLEO, DELPHI, BABAR, CDFII) Aim: Constrain the unknown non-pert. parameters and reduce |Vcb| uncertainty. With enough measurements: test of underlying assumptions (duality…).

  18. What is Xc? Higher mass states: D** Semi-leptonic widths (PDG 04): (PDG b/B+/B0 combination, bu subtracted) • ~25% of semi-leptonic width is poorly known • Possible D’D(*)contributions neglected: • No BlD’ experimental evidence so far • DELPHI limit: • We assume no D’ contribution in our sample

  19. Analysis Strategy Typical mass spectrum M(X0c)(Monte Carlo): D0 and D*0 well-known measure only f**  only shape needed 1) Measure f**(sH) 2) Correct for background, acceptances, bias  moments of D** 3) Add D and D*  M1,M2 4) Extract OPE parameters (, 1)

  20. D+/D*+ Reconstruction Exclusive reconstruction of D**: D**0 D*+**- D0*+ (Br=67.7%) K- + (Br=3.8%) K- + - + (Br=7.5%) K- + 0 (Br=13.0%) K- + B- D**0l- D+ + PV “D*+” - (aka **) l- D**0 D+**- K- + + (Br=9.2%) “D+” ~28K e/D Candidates in total!

  21. Backgrounds Physics background: BD(*)+Ds-, D(s)Xl  MC, subtracted Combinatorial background under the D(*) peaks:  sideband subtraction • Feed-down in signal: • D**0 D*+( D+0)- • irreducible background to • D**0 D+-. • subtracted using data: • shape from D0- in D**0 D*+( D0+)- • rate: ½ (isospin) x eff. x BR • Prompt pions faking **: • fragmentation • underlying event • separate B and primary vertices (kills also prompt charm)  use impact parameters to discriminate •  model: wrong-sign **+-combinations

  22. Corrected Mass and D** moments Results (in paper): Procedure: • Unbinned procedure using weighted events. • Assign negative weights to background samples. • Propagate efficiency corrections to weights. • Take care of the D+ / D*+relative normalization. • Compute mean and sigma of distribution. No Fit !!!

  23. Systematic Errors

  24. Results & Comparison with other experiments (Correlated uncertainties) (Correlated uncertainties) (Correlated uncertainties) (Correlated uncertainties) Pole mass scheme

  25. Extraction of the HQE Parameters • Combination of all the experimental measurements of the hadronic moments • Effective determination of the two OPE operators relevant at order 1/mB() 1/mB2 (1) • CDF contributes as much as the B factories in this determination!

  26. Bs Mixing

  27. Working our way on CKM sides    • Vtd is derived from mixing effects • QCD uncertainty is factored out in this case resorting to the relative Bs/Bd mixing rate (Vtd/Vts) • Beyond the SM physics could enter in loops!

  28. B production at the TeVatron • Production: ggbb • NO QM coherence, unlike B factories • Opposite flavor at productionone of the b quarks can be determined to assess the flavor of the other at production • Fragmentation products have some memory of b flavor as well

  29. Nunmix-Nmix A= Nunmix+Nmix Bs Mixing 101 • ms>>md • Different oscillation regime  Amplitude Scan Perform a ‘fourier transform’ rather than fit for frequency B lifetime A  ms [ps-1]

  30. Amplitude Scan • Mixing amplitude fitted for each (fixed) value of m • On average every m value (except the true m) will be 0 • “sensitivity” defined for the average experiment [mean 0] • The actual experiment will have statistical fluctuations • Actual limit for the actual experiment defined by the systematic band centered at the measured asymmetry Just an example: Not based on real data!

  31. Bs Mixing Ingredients Proper time resolution Flavor tagging Signal-to-noise Event yield

  32. Nunmix-Nmix A= Nunmix+Nmix Flavor Tagging Reconstructed decay Fragmentation product “Same Side” B meson Several methods, none is perfect !!!

  33. Bs Mixing: tagging performance Summer ‘04 Measured from Bd data! • Fall ’05 (mostly re-optimize existing taggers): • 1.12±0.18  1.55±0.16 • 1.43±0.093  1.55±0.085

  34. BsllDs K K  BsDs K K  Ds Ds l  l Bs Bs ~0.5% ~15% s æ ö m ç ÷ P s = s Ä s B ct Å t ç ÷ ct L K P P xy è ø t t Proper time resolution Semileptonic modes: momentum uncertainty Fully reconstructed: Lxy uncertainty  improve reconstruction

  35. Bs Mixing: semileptonic • BsDsl • Ds (4350100 3.1 ) • DsK*K (175080 0.42 ) • Ds (157090 0.32) Yield s/b Summer ‘04 ms> 6.8 ps-1 @ 95% CL Sensitivity: 10.6 ps-1 Reach at large ms limited by incomplete reconstruction (ct)!

  36. Bs Mixing: hadronic • BsDs • Ds (55040 ~1.8) • DsK*K (24040 ~1.7) • Ds (11025 ~1.0) • Using also BsDs [about 1/3 more statistics] Yield s/b ms> 0.0 ps-1 @ 95% CL Sensitivity: 9.8 ps-1 Low statistics, but promising!

  37. Combined Bs mixing limit ms> 8.6 ps-1 @ 95% CL Sensitivity: 13.0 ps-1 ms> 16.6 ps-1 @ 95% CL Sensitivity: 20.0 ps-1 Competitive in precision with best experiment at large Dms More statistics and improvements to come…

  38. Bs Mixing Perspectives • Analysis is pretty much defined! We know where we can improve: • Statistics • Data (lumin.: 350pb-1600pb-1??) • New Modes (e.g. BsDs* >2x?) • D2 : • Additional taggers (SSK, OSK…) • Improve existing algorithms • Proper time resolution • Refine event-by-event reconstruction • Optimal usage of kinematics for non-closed modes With the March 2006 data sensitivity~SM value

  39. What happens for large xs? • Indirect Measurement of Dms: • SM DGs/Gs=0.120.06 (Dunietz, Fleischer & Nierste)

  40. Probing at large ms: / • BsJ/ • B VV, mixture of CP even/odd separate by angular analysis • Combine two-lifetime fit + angular DGs=GH-GL few ps-1 in ms ! PRL 94, 101803 2005

  41. Beyond the SM • Analyses like this have laid down the path and the tools and techniques for the exploration of the SM boundaries: • Non SM effects: • bd ? • bs • Rare decays (bs) • Bs, etc. • BK • Bs • xs

  42. Rare decays • Exploit the large B production rate • Measure relative BR (e.g.  to J/K) to factor out absolute  and luminosity measurements • SM: BR(Bs) <3.8E-9 • Sensitive to new physics! Publ: PRL 93, 032001 2004 Update: Hep-ex/0502044 PRD 68, 091101 2003

  43. hep-ex/0502044 • bsss transitions are ‘misbehaving’ at B factories • …CDF II can look at them too. We started from K: CP: sss • …With the advantage of being able to look at Bs too:

  44. Perspectives Exciting times ahead: • Most analyses sensitive to BSM physics are statistically limited • Significant improvements can be made including new modes and techniques • Bs results will be an important complementary addition to the CKM mapping!

  45. Conclusions • We are living an exciting transition era of more and more quantitative results in the CKM sector • BSM physics could be around the corner, but hard to discern models without direct evidences • With LHC we will soon jump in the completely uncharted territory! • Living this constant exploration of new discoveries puts us at the forefront of human knowledge, but this is not news! • “Modern science did not spring perfect and complete, as Athena from the head of Zeus, from the mind of Galileo and Descartes”

  46. Purgatory

  47. A guiding theme • Exploring the boundaries of knowledge is a recurrent theme in history • Geographical explorations exemplify the paradigm: Question (Why? Where? What? When? Who?) Development of tools (ships, telescope, microscope…) Explore the boundaries of knowledge (ships, telescope, microscope) G. Galilei Jump in! (the unknown) (America, planets, atoms…)

  48. Hadronic Moments, HQET and Vcb Most precise determination of Vcb comes from sl (“inclusive” determination): (4S), LEP/SLD, CDF measurements. Experimental |Vcb|~1% Theory with pert. and non-pert. corrections. |Vcb|~2.5% Ftheory evaluated using OPE in HQET: expansion in s and 1/mB powers: O(1/mB)  1 parameter:  (Bauer et al., PRD 67 (2003) 071301) O(1/mB2)  2 more parameters: 1, 2 O(1/mB3)  6 more parameters: 1, 2,T1-4 Constrained from pseudo-scalar/vector B and D mass differences

  49. How can CDF look at it? Must reconstruct all channels to get all the D** states. • However CDF has limited capability for neutrals • B0D**-l+ always leads to neutral particlesignore it • B- D**0l- better, use isospin for missing channels: • D**0 D+- OK • D**0 D00 Not reconstructed. Half the rate of D+- • D**0 D*+- • D*+ D0+OK • D*+ D+0 Not reconstructed. Feed-down to D+- • D**0D*00 Not reconstructed. Half the rate of D*+-

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