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B s Oscillations and Rare Decays at the Tevatron

B s Oscillations and Rare Decays at the Tevatron. GDR SUSY Workshop 28. April 2008 Strasbourg. Outline. Motivation Measurement of Bs mixing:  m s Measurement of DG CP Violation in the B s system Rare leptonic decays b->llX transitions Summary. Motivation. Why huge

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B s Oscillations and Rare Decays at the Tevatron

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  1. Bs Oscillations and Rare Decays at the Tevatron GDR SUSY Workshop 28. April 2008 Strasbourg Ralf Bernhard

  2. Outline • Motivation • Measurement of Bs mixing: ms • Measurement of DG • CP Violation in the Bs system • Rare leptonic decays • b->llX transitions • Summary

  3. Motivation Why huge matter-antimatter asymmetry in the universe? Why B Physics? - It’s got it all! • Electroweak symmetry breaking determines flavor structure: CKM matrix, CP violation, FCNC’s • QCD Modeling: production, spectroscopy, masses, lifetimes, decays Challenges lattice gauge, Heavy Quark Effective Theory, strong symmetries • Search for new physics rare decays and Why at the Tevatron?  Complementary to (4S) B factories

  4. Tevatron Tevatron continues to perform well • Over 3.9fb-1 delivered and 3.4fb-1 recorded by each experiment, 2.8fb-1 analysed • Peak luminosities of ~3 x1032 cm-2 s-1  up to 10 interactions

  5. Detectors Relevant for B physics: DØ Tracker: excellent coverage & vertexing • Silicon & scintillating fiber • Small radii, but extending to |h| < 2 • New Layer 0 silicon on beam pipe in 2006, improving impact para. resol. • Triggered muon coverage: |h| < 2 • E.g.triggers: dimuons, single muons, • track displacement @ L2 • CDF Tracker: excellent mass resolution • & vertexing • Silicon, Layer 00 • Large radii drift chamber, many hits, excellent momentum resolution • dE/dx (and TOF): particle id • Triggered muon coverage: |h| < 1 • E.g.triggers: dimuons, lepton + displ. track, two displaced tracks

  6. Mixing and Oscillations

  7. Mixing and Oscillations

  8. Mixing and Oscillations Probe entire matrix Whole new window for New physics Sensitive for NP Not sensitive for NP Very sensitive for NP

  9. Frequency of Oscillations Decays:

  10. Decay channels

  11. CDF Signal Selection

  12. DØ Signal Selection RunIIa Only 250 reconstructed and tagged hadronic events (CDF ~500)

  13. Decay channels

  14. Amplitude scan 1/Dm Asymmetry time Motivation is to simplify combining results with other experiments Power spectrum frequency Dm

  15. Bs: ms, Frequency of Osci.

  16. CP Violation In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!! e.g. 43 in MSSM

  17. CP Violation In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!

  18. CP Violation In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!

  19. Bs: ms, Frequency of Osci B Factories Tevtron Not much room for New Physics!

  20. Measurement of DG First assume no CP violation in Bs mixing, s=0 CP and mass eigenstates are the same • Bs→Ds(*)Ds(*) • Three channels • [DsDs (PP), Ds*Ds (VP), Ds*Ds* (VV)] • Heavy quark limit + factorization • Bsodd→Ds*Ds is forbidden • Ds*Ds* in S-wave • Ds(*)Ds(*) pure CP even • Flavor specific Bs lifetime • Flavor specific decays carry equal amounts of BH and BL • Get flavor specific lifetime if FS data with is fit w/ single exponential • Bs→J/yf P → VV • Even and odd paths distinguishable with angular analysis of final state particles

  21. DG from Bs→Ds(*)Ds(*) n m g K1 Bs K2 Ds K3 Ds g K4 p Phy. Rev.Letters 99, 241801 (2007) • Trigger on muon from semileptonic Ds decay • Ignore any photons • Look for correlated production of Ds→fp and Ds→fm

  22. DG from Bs→Ds(*)Ds(*) n m g K1 Bs K2 Ds K3 Ds g K4 p Phy. Rev.Letters 99, 241801 (2007)

  23. Bs Flavor Specific Lifetime Know flavor at time of decay from charge of decay product - + 50% CP-even, 50% CP-odd at time t0 hep-ph/0201071 Phys.Rev.Lett.97:241801,2006 D+→fp Ds→fp

  24. Bs Flavor Specific Lifetime

  25. Bs→J/yf • Heavy (H, CP-odd) and Light (L, CP-even) Bs states • Decays into two vector mesons that are either CP-odd (L=1) or CP-even (L=0,2) • Time-dependent angular distributions allow separation of components • Simultaneous fit to lifetime and three angles Not “flavor specific”, predicted to be more CP even than odd

  26. Bs→J/yf arXiv:/0802.2255 arXiv:/:0712.2348 even / light odd / heavy 2506±51 1976±65 Candidate BS

  27.  and s First assume no CP violation in Bs mixing, s=0 CP and mass eigenstates are the same

  28. CP Violation In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!

  29. CP Violation in Bs System Explore new part of matrix In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!

  30. CP Violation in Bs System Explore new part of matrix In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!

  31. CP Violation in Bs System • How could New Physics affect these phases • Both CDF and DØ measure/observe the phase responsible for CP violation in Bs -> J/ decays • Use flavor tagging to identify initial flavor of Bs or Anti Bs in J/ decays (and know value of ms)

  32. CP Violation in Bs→J/yf • Even without initial state flavor tagging, have sensitivity to s • But 4-fold ambiguity, reduce to 2-fold with flavor tagging...

  33. CP Violation in Bs→J/yf • Now use initial state flavor tagging • Ambiguities

  34. CP Violation in Bs→J/yf • Now using initial state flavor tagging, constrain strong phases • Ambiguities

  35. fs Measurement m+ m+ nm B Bs Bs Ds- m- ↕ this versus this ↕ m- nm Bs Bs B Ds+ In Standard Model: fs≈arg(-Vts) ≈ 0.004 rad. Observables: Semileptonic asymmetries, interference in decays to CP eigenstates A. Lenz, U. Nierste hep-ph/0612167 Two samples Exclusive untagged Dsm Inclusive like-sign mm

  36. Same sign Dimuons Phys. Rev. D 74, 092001 (2006) N(same sign) ≈ 310K ~60/40 mix of Bd and Bs Z ~ 2c ASL(Bd)=-0.0047±0.0046 (HFAG, B-factories ) Regular flipping of polarity of solenoid (tracking) and toroid (muons) magnets essential for controlling systematic uncertainties

  37. Exclusive Bs→Ds±mnResults Exclusive Dsm m+ + pol Phys. Rev. Lett. 98, 151801 (2007) m- DØ Combined: m(fp) m+ - pol Using Dms from CDF: m- h>0 h<0 CDF: 1.6 fb-1, CDF Note 9015

  38. fs Results Combined with older DØ analysis before flavor tagging

  39. CP Violation in Bs: Combination • In Bs→J/yf flavor-tagged analyses, in (s,s) space CDF has ~1.5s deviation from SM, DØ ~1.8s deviation, consistent with each other • Need to be careful, non-parabolic log(L), multiple correlations (best is simply more data!!) DØ, 2.8fb-1

  40. UTfit results Next talk from Marcella Bona

  41. Direct CP violation in b Hadrons • Direct (not through mixing)CP violation expected to be large in some b hadron decays, including B mesons and b Baryons • Measure asymmetry: f=final state • CDF: Br's and asymmetries of two-body charmless states, Bhh’ • Expectations, asymmetry ~30% • First CP asymmetry measurement in b baryon decays

  42. Direct CP violation in b Hadrons • DØ: Small (~1%) CP asymmetry expected in SM for B+→J/K+ • Again, frequent solenoid and toroid polarity reversals essential to control charge asymmetry systematic uncertainties • Correct for K+/K- asymmetry • <1% precision factor ~2 better than current world average Accepted by Phys. Rev. Lett.

  43. Purely leptonic B decay • B->l+ l- decay is helicity suppressed FCNC • SM: BR(Bs->m+m-) ~ 3.410-9 • depends only on one SM operator in effective Hamiltonian, hadronic uncertainties small • Bd relative to Bs suppressed by |Vtd/Vts|2 ~ 0.04 if no additional sources of flavor violation • reaching SM sensitivity: present limit for Bs -> m+m- comes closest to SM value Current published limits at 95%CL: SM expectations:

  44. Purely leptonic B decay Two-Higgs Doublet models: • excellent probe for many new physics models • particularly sensitive to models w/ extended Higgs sector • BR grows ~tan6b in MSSM • 2HDM models ~ tan4b • mSUGRA: BR enhancement correlated with shift of (g-2)m • also, testing ground for • minimal SO(10) GUT models • Rp violating models, contributions at tree level • (neutralino) dark matter … Rp violating: ?

  45. Search Strategy NN • Preselection of Di Muon events • Normalization channel B+→J/ψK+ • Background estimation using sidebands • Background reduction using a LHR (DØ) or NN (CDF) RunIIa 0.8 ± 0.2 events Observe 1 event

  46. Limits Relative Normalization eB+ /eBs relative efficiency of normalization to signal channel fs/fu fragmentation ratio - use world average (3.71) with 15% uncertainty eBd /eBs relative efficiency for Bd-> m+ m- versus Bs-> m+ m- events in Bs search channel (~0.95) R = BR(Bd)/BR(Bs) is small due to |Vtd/Vts|^2 at 90% CL DØ Note 5344 PRL 100,101802 (2008)

  47. Rare decays constraining NP

  48. Study of b -> s l+l- • long-term goal: investigate b -> s l+ l- FCNC transitions in B+, Bd and Bs mesons • B+->l+ l- K+ and Bd -> l+ l- K* established at B factories • Bs -> l+ l- only accessible at the Tevatron • SM prediction: • short distance BR: ~1.6×10-6 • About 30% uncertainty due to B-> form factor • 2HDM: enhancement possible, depending on parameters for tanb and MH+

  49. b->sl+l- Theory Mass spectrum The forward backward asymmetry is defined as the asymmetry between forward and backward emitted positive leptons in the dilepton rest frame where the direction is relative to the direction of the B meson. Sensitive to “new Physics” contribution

  50. B->h @ CDF arXiv:0804.3908

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