1 / 24

Exclusive Semileptonic B Decays and |V ub |: Experimental

Exclusive Semileptonic B Decays and |V ub |: Experimental. 4 th Flavor and CP Violation Conference Vancouver, BC 9 th – 12 th April 2006 Kevin Varvell University of Sydney. Significance of |V ub | Measurement. Precision measurement of SM parameter, size not theoretically predicted

ivy
Download Presentation

Exclusive Semileptonic B Decays and |V ub |: Experimental

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. Exclusive Semileptonic B Decays and |Vub|: Experimental 4th Flavor and CP Violation Conference Vancouver, BC 9th – 12th April 2006 Kevin Varvell University of Sydney

  2. Significance of |Vub| Measurement • Precision measurement of SM parameter, size not theoretically predicted • Constrain one side of the Unitarity Triangle • Test consistency of SM picture, particularly between |Vub|/|Vcb| and sin21 (sin2β) • Current precision • sin21~ 4% • |Vcb|~ 2% (one recent update mentioned here) • |Vub|~ 7% inclusive (talk this afternoon, E. Barberio) >10% exclusive (main subject of this talk) • Aim is for ‹ 5% precision for |Vub|excl, compare with |Vub|incl This side determined By |Vub|/|Vcb| K. Varvell

  3. From Exclusive Semileptonic B decay to |Vub| e+e-→Υ(4S) → BB • Measurements made in • Ideally want to measure rate of tree level process Γ(b  x l) • Complicated by strong interaction effects – form factors needed • Channel B  πl is the most promising for |Vub| - one dominant form factor q2 shape and normalization needed f+(q2) K. Varvell

  4. Determining the Form Factor f+(q2) • Earlier predictions made with quark models, e.g. ISGW2 • Lattice QCD • makes predictions at high q2 (q2 > ~16 GeV2) • unquenched calculations have become available in recent times • e.g. HPQCD FNAL • Light Cone Sum Rules • makes predictions at low q2 (q2 < ~14 GeV2) • e.g. Ball & Zwicky • Parametrization has traditionally been used to extend LQCD or LCSR to full q2 range • FF normalization main issue when extracting |Vub| • How much theory input needed for |Vub| measurement? (R. Hill talk) hep-lat-0601201 hep-lat-0409116 PRD 71 (2005) 014015 hep-ph/0509090 K. Varvell

  5. Approaches to Measuring B(B  πl) Signal Rest used to reconstruct  Signal ExampleTag side Signal ExampleTag side

  6. Range of Applicability of Methods 140 250 500 1000 • Scenario • Untagged • D(*) ltag • Full recon tag fb-1 • Boundaries indicative only • Full recon tag will ultimately become method of choice. • Currently • Belle Lint ~ 500 fb-1 • BaBar Lint ~ 300 fb-1 K. Varvell

  7. CLEO Untagged B  πl (9.7M BB) ΔE mBC Phys. Rev. D 68 (2003) 072003 • Search (and fit for yields) across a number of exclusive Xulν modes +,0,+,0,ω,η • Isospin constraints imposed in fit • Extract partial BF in 3 q2 bins for + and + -result K. Varvell

  8. CLEO Untagged B  πl (cont.) (9.7M BB) +0.16 +0.53 |Vub| = (3.17 ± 0.17 ± 0.03) x 10-3 -0.17 -0.39 Phys. Rev. D 68 (2003) 072003 • FF models enter extraction of BF through • Signal efficiency from MC • b → u crossfeed and b → c background modelling in MC Different FF models -result B(B0 π-l+) = (1.33 ± 0.18 ± 0.11 ± 0.01 ± 0.07) x 10-4 syst FF sig stat FF crossfeed ( and  mode combined) LCSR + LQCD (unq) FF shape ρ stat syst theo K. Varvell

  9. BaBar Untagged B0 π-l+ 79fb-1 (86M BB) mBC ΔE Phys .Rev. D72 (2005) 051102 • Simultaneous extraction of modes +,0,+,0 -result Yield 396 -lν, 137 0lν K. Varvell

  10. BaBar Untagged B0 π-l+ (cont) 79fb-1 (86M BB) +0.88 |Vub| = (3.82 ± 0.14 ± 0.22 ± 0.11 ) x 10-3 -0.52 Phys .Rev. D72 (2005) 051102 • Isospin constraints imposed • Extract partial BF in • 5 q2 bins  • 3 q2 bins ρ • “Marginal” agreement with ISGW2 -result B(B0 π-l+) = (1.38 ± 0.10 ± 0.16 ± 0.08) x 10-4 syst stat FF shape FNAL LQCD syst stat FF shape FF norm K. Varvell

  11. Belle SL Tag B  πl+ 253fb-1 (275M BB) xB2 Mx xB2 Mx hep-ex/0604024 • Simultaneous extraction of modes +,0,+,0 • xB2 must lie in range [0,1] for signal events Submitted to PLB Yield 156 -lν, 69 0lν K. Varvell

  12. Belle SL Tag B  πl+ (cont) p- p0 |Vub| = (4.03 ± 0.46 ± 0.22 ) x 10-3 |Vub| = (3.60 ± 0.41 ± 0.20 ) x 10-3 +0.62 +0.59 -0.41 -0.41 hep-ex/0604024 • Extract partial BF in 3 q2 bins B(B0 π-l+) = (1.38 ± 0.19 ± 0.14 ± 0.03) x 10-4 syst stat FF shape B(B+ π0l+) = (0.77 ± 0.14 ± 0.09 ± 0.00) x 10-4 syst stat FF shape + + 0,q2 ≥ 16 GeV2, FNAL syst stat theo + + 0,q2 ≥ 16 GeV2, HPQCD syst stat theo K. Varvell

  13. BaBar SL Tag B0 π-l+ 211fb-1 (232M BB) hep-ex/0506064 • Single mode - studied • cos2fB  [0,1] for signal events Yield 61 -lν K. Varvell

  14. BaBar SL Tag B0 π-l+ (cont) 211fb-1 (232M BB) +0.8 |Vub| = (3.3 ± 0.4 ± 0.2 ) x 10-3 -0.4 hep-ex/0506064 • Extract partial BF in 3 q2 bins B(B0 π-l+) = (1.03 ± 0.25 ± 0.13) x 10-4 syst stat +0.8 HPQCD04 syst FF norm stat K. Varvell

  15. BaBar SL Tag B+ π0l+ 81fb-1 (88M BB) hep-ex/0506065 • Single mode0studied • cosθB0l  [-1, 1] for signal events Yield 45 0lν B(B+ π0l+) = (1.80 ± 0.37 ± 0.23) x 10-4 stat syst K. Varvell

  16. BaBar Full Recon Tag B  πl+ 211fb-1 (233M BB) p- p0 hep-ex/0507085 • Tag : Fully reconstructed B  D decays (“Breco” tag) Select using ΔE, mES (beam constrained B candidate mass) • mmiss2 distribution : peaks at zero for signal (single missing neutrino) mγγ Yield 36 -lν, 34 0lν K. Varvell

  17. BaBar Full Recon Tag B  πl+ +0.8 |Vub| = (3.7 ± 0.3 ± 0.2 ) x 10-3 -0.5 hep-ex/0507085 • Extract partial BF in 3 q2 bins p0 p- B(B0 π-l+) = (1.14 ± 0.27 ± 0.17) x 10-4 stat syst B(B+ π0l+) = (0.86 ± 0.22 ± 0.11) x 10-4 syst stat Combined + + 0 B(B  πl+) = (1.28 ± 0.23 ± 0.16) x 10-4 syst stat + + 0, HPQCD syst stat FF norm K. Varvell

  18. Summary of B(B  πl) Exclusive p0 p- HFAG Winter 2006 Note: Updated Belle SL tag result not yet incorporated in plot Untagged analyses currently the most precise Average B(B0 π-l+): (1.34 ± 0.08 ± 0.08) x 10-4 K. Varvell

  19. Summary of |Vub| from Exclusive B  πl HFAG Winter 2006 Experimental q2 shape input not used (yet) Using FF calculated in region of applicability Using FF extrapolated to full q2 range K. Varvell

  20. Other B  Xul Exclusive Modes +0.47 +0.35 -0.54 -0.47 Tag PRD 68 (2003) 072003 Untagged Untagged PRD 61 (2000) 052001 Full hep-ex/0408068 Untagged PRL 90 (2003) 181801 PRD 72 (2005) 051102 Untagged SL hep-ex/0604024 Untagged PRD 68 (2003) 072003 SL hep-ex/06xxxxx PRL 93 (2004) 131803 Untagged HFAG Compilation, except with updated Belle SL result included K. Varvell

  21. BaBar Exclusive |Vcb| Measurement 79fb-1 (86M BB) Update to PRD 71 (2005) 051502 submitted to PRD hep-ex/0602023 • Multi-Dimensional fit to helicity amplitudes for 2 (slope parameter) and R1, R2 (FF ratios), all functions of H+,-,0(w). w = vB· vD* K. Varvell

  22. BaBar Exclusive |Vcb| Measurement (cont) +1.5 |Vcb| = (37.6 ± 0.3 ± 1.3 ) x 10-3 -1.3 syst stat theo hep-ex/0602023 • Improvement in FF uncertainty • Reduces |Vcb| systematic error • Useful for understanding b → c background in b → u R1 = 1.396 ± 0.060 ± 0.035 ± 0.027 R2 = 0.885 ± 0.040 ± 0.022 ± 0.013 ρ2 = 1.145 ± 0.059 ± 0.030 ± 0.035 w cosθl χ cosθV K. Varvell

  23. Summary of Exclusive |Vcb| Measurements HFAG Winter 2006 Note: Does not include latest BaBar result from hep-ex/0602023 K. Varvell

  24. Summary and Future : Exclusive |Vub| Measurements • CLEO, BaBar and Belle ⇒ Xu BF measurements using several channels and several techniques Xu :+,0,+,0,ω,η ⇒ |Vub| extracted using +,0 modes – Exptl error approaches 5% - FF normalization error dominates ⇒ Xc BF measurements and |Vcb| continue to be important ⇒ future precision Xu measurements using Full Recon tagging ⇒FF shapemeasurements from experiment now possible • Theory progress important (and happening) as well (R. Hill talk) (P. Mackenzie talk) • |Vub| to better than 5% precision overall from exclusive semileptonic B-factory measurements? ⇒ Feasible. K. Varvell

More Related