1 / 13

Rare Decays at D0

Rare Decays at D0. Rare Decays at D0 D. Buchholz – Northwestern University For the D0 Collaboration. Flavor Changing Neutral Currents. Standard Model and data agree remarkably well Standard Model forbids FCNC at tree level Look for deviations from SM

toya
Télécharger la présentation

Rare Decays at D0

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. Rare Decays at D0 • Rare Decays at D0 • D. Buchholz – Northwestern University • For the D0 Collaboration D. Buchholz, Rare Decays at D0, ICHEP 2008

  2. Flavor Changing Neutral Currents • Standard Model and data agree remarkably well • Standard Model forbids FCNC at tree level • Look for deviations from SM • One place to search for new physics is in FCNC decays • FNAL’s Tevatron has large c and b cross sections • Challenge- how to select c and b decays from much larger inelastic total σ • Trigger on single μ from semileptonic or leptonic decays D. Buchholz, Rare Decays at D0, ICHEP 2008

  3. D+(s)→π+μ+μ- Example of beyond tree level diagram in SM for D+→π+μ+μ- • Look in the up quark sector c→ u μμ • Expect long distance resonance production, e.g. c→ u , which is not a test of FCNC • BR =1.9X10-6 • Short range continuum production , test of FCNC • Modification to SM- e.g. • Fajfer et al, PRD 73, 054026 (2006) – effect of light Higgs • Burdman et al., PRD 66 014009, (2002) – RPV in up sector but not in down sector D. Buchholz, Rare Decays at D0, ICHEP 2008

  4. Resonant D+(s) Decays • Resonant production • Select  region for m(μμ) • N(Ds+)=254±36 • N(D+) = 115±31 • Statistical Significance • 8σ for combined Ds+ and D+ • 4.1 σ for D+ • First observation for Ds+ • First evidence for D+ • Measure BR(D+→ π+→μ+μ-π+) • (1.8±0.5±0.6)x10-6 D. Buchholz, Rare Decays at D0, ICHEP 2008

  5. Continuum D+(s) Decays • Remove resonant  →μ+μ- mass region and then look in m(μ+μ-π+) • leaves 19 candidates in D+ window • Background expect from sidebands 25.8±4.6 • Normalize to D+→ π+ • BR(D+→ μ+μ-π+) • <3.9x10-6 @90%CL • PRL 100, 101801 (2008) D. Buchholz, Rare Decays at D0, ICHEP 2008

  6. Purely Leptonic B decays • Look for B0→ℓ+ℓ-, either from B0d or B0s • Helicity suppressed FCNC • SM predicts Buras- Phys Lett B566, 115 (2003) • BR(B0s→μ+μ-) =(3.4 ± 0.54)x10-9 • BR(B0d→μ+μ-) =(1.0 ± 0.14)10-9; suppressed by |Vtd/Vts|2 ~ 0.04 • Depends on one SM operator in effective Hamiltonian with small hadronic uncertainties • To reach SM limit for B0→ℓ+ℓ- • Current limits B0s→ μ+μ- is closest D. Buchholz, Rare Decays at D0, ICHEP 2008

  7. Analysis Process for B0(s)→μ+μ- • Dimuon trigger • Select broad mass range • Optimize selection- • use likelihood ratio method based on 6 exp variables - LHR • Blind analysis in B mass region • Normalize to B±→J/ΨK±, J/Ψ→μ+μ- • to get a branching ratio D. Buchholz, Rare Decays at D0, ICHEP 2008

  8. Look for B0(s)→μ+ μ- decays • Separate data into Run IIa and IIb • Plot Invariant μ+ μ-mass vs. LHR • Cut on LHR to get final number of μ+ μ- in B0 region and sidebands • 1 event in Run IIa • 2 events in Run IIb • Consistent with background • Preliminary result • BR(B0s→ μ+μ-)<7.3 x10-8 • D0 Conf. Note 5344 D. Buchholz, Rare Decays at D0, ICHEP 2008

  9. CPV and Bs→Ds(*)Ds(*) Partial width difference between CP even and CP odd Bs decays ≈ saturated by the Bs→Ds(*)Ds(*) branching fraction No CPV Also traces out contour in DG/fs plane with CPV See poster session- SungWoo Youn from D0 for Bs→Ds(*) Ds(*) details Projection from J/yf Projection from Ds(*)Ds(*) Not used in constraints b/c theory error uncontrolled Odd fraction of Ds(*)Ds D. Buchholz, Rare Decays at D0, ICHEP 2008

  10. Finding Bs→Ds(*)Ds(*) Extracted using one semileptonic Ds decay and normalized to Bs→Dsmn Use Likelihood ratio method for analysis Signal extracted from 2-D unbinned log-likelihood fit to m(Ds)-m(f) plane p m(KKp) g K Bs K DsDs K K g m n m(KK) D. Buchholz, Rare Decays at D0, ICHEP 2008

  11. Extract Background from Bs→Ds(*)Ds(*) ~10% Residual backgrounds from Bu,d and Bs semileptonic decay subtracted by looking in 2-D m(fm)-m(Dsfm) plane B→DsDsKX Bs→Dsfmn D. Buchholz, Rare Decays at D0, ICHEP 2008

  12. Bs→Ds(*)Ds(*) preliminary results Statistics at 2.8 fb-1 Accelerator division will reduce this Sys dominated by input Bs and Ds BFs Need help from CLEO-c and Belle ϒ(5S) Consistent with standard model- see poster of SungWoo Youn D. Buchholz, Rare Decays at D0, ICHEP 2008

  13. Conclusions • D0 very active in decay studies of FCNC • B0s→ μ+μ- • D+→μ+μ-π+ • Adding information on existing puzzles • CPV from fswithDs(*)Ds(*) • Tevatron contributing to rare heavy quark decays • Rare bottom and ultra rare charm • More statistics to come D. Buchholz, Rare Decays at D0, ICHEP 2008

More Related