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

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| FPCP06 11-Apr-2006 K. Varvell

From Exclusive Semileptonic B decay to |Vub| 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  π l  is the most promising for |Vub| - one dominant form factor q2 shape and normalization needed e+e-→Υ(4S) → BB f+(q2) FPCP06 11-Apr-2006 K. Varvell

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 FPCP06 11-Apr-2006 K. Varvell

Approaches to Measuring B(B  π l ) Untagged initial 4-momentum known missing 4-momentum = ν Reconstruct B  π l  using mB (beam-constrained) and ΔE = EB-Ebeam Pros High efficiency Cons ν resolution problematic Rel. high backgrounds (rel. low purity) Semileptonic (SL) Tag One B reconstructed in a selection of D(*) l  modes Two missing ν in event Use kinematic constraints Lower backgrounds (higher purity) Rel. low efficiency Full Recon Tag One B reconstructed completely in known b  c mode. Many modes used. Very good ν resolution Very low backgrounds Very low efficiency Rest used to reconstruct  Signal Signal ExampleTag side Signal ExampleTag side

Range of Applicability of Methods Scenario Untagged D(*) l  tag Full recon tag 140 250 500 1000 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 FPCP06 11-Apr-2006 K. Varvell

CLEO Untagged B  π l  - result mBC ΔE (9.7M BB) Phys. Rev. D 68 (2003) 072003 (9.7M BB) Search (and fit for yields) across a number of exclusive Xu l ν modes +,0,+,0,ω,η Isospin constraints imposed in fit Extract partial BF in 3 q2 bins for + and + mBC ΔE - result FPCP06 11-Apr-2006 K. Varvell

CLEO Untagged B  π l  (cont.) (9.7M BB) FF models enter extraction of BF through Signal efficiency from MC b → u crossfeed and b → c background modelling in MC Phys. Rev. D 68 (2003) 072003 Different FF models - result B(B0  π- l+ ) = (1.33 ± 0.18 ± 0.11 ± 0.01 ± 0.07) x 10-4 stat syst FF sig FF crossfeed |Vub| = (3.17 ± 0.17 ± 0.03) x 10-3 +0.16 +0.53 -0.17 -0.39 ( and  mode combined) LCSR + LQCD (unq) stat FF shape ρ syst theo FPCP06 11-Apr-2006 K. Varvell

BaBar Untagged B0  π- l+  Simultaneous extraction of modes +,0,+,0 Phys .Rev. D72 (2005) 051102 79fb-1 (86M BB) ΔE mBC - result Yield 396 -lν, 137 0lν FPCP06 11-Apr-2006 K. Varvell

BaBar Untagged B0  π- l+  (cont) Isospin constraints imposed Extract partial BF in 5 q2 bins  3 q2 bins ρ “Marginal” agreement with ISGW2 Phys .Rev. D72 (2005) 051102 79fb-1 (86M BB) - result B(B0  π- l+ ) = (1.38 ± 0.10 ± 0.16 ± 0.08) x 10-4 stat syst FF shape |Vub| = (3.82 ± 0.14 ± 0.22 ± 0.11 ) x 10-3 +0.88 -0.52 FNAL LQCD stat syst FF shape FF norm FPCP06 11-Apr-2006 K. Varvell

Belle SL Tag B  π l+  Mx xB2 hep-ex/0604024 253fb-1 (275M BB) Simultaneous extraction of modes +,0,+,0 xB2 must lie in range [0,1] for signal events Submitted to PLB Mx xB2 Yield 156 -lν, 69 0lν FPCP06 11-Apr-2006 K. Varvell

Belle SL Tag B  π l+  (cont) p- p0 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 stat syst FF shape B(B+  π0 l+ ) = (0.77 ± 0.14 ± 0.09 ± 0.00) x 10-4 stat syst FF shape |Vub| = (3.60 ± 0.41 ± 0.20 ) x 10-3 +0.62 -0.41 + + 0, q2 ≥ 16 GeV2, FNAL stat syst theo |Vub| = (4.03 ± 0.46 ± 0.22 ) x 10-3 +0.59 -0.41 + + 0, q2 ≥ 16 GeV2, HPQCD stat syst theo FPCP06 11-Apr-2006 K. Varvell

BaBar SL Tag B0  π- l+  hep-ex/0506064 211fb-1 (232M BB) Single mode - studied cos2fB  [0,1] for signal events Yield 61 -lν FPCP06 11-Apr-2006 K. Varvell

BaBar SL Tag B0  π- l+  (cont) hep-ex/0506064 211fb-1 (232M BB) Extract partial BF in 3 q2 bins B(B0  π- l+ ) = (1.03 ± 0.25 ± 0.13) x 10-4 stat syst |Vub| = (3.3 ± 0.4 ± 0.2 ) x 10-3 -0.4 +0.8 +0.8 HPQCD04 stat syst FF norm FPCP06 11-Apr-2006 K. Varvell

BaBar SL Tag B+  π0 l+  hep-ex/0506065 81fb-1 (88M BB) Single mode 0 studied cosθB0l  [-1, 1] for signal events Yield 45 0lν B(B+  π0 l+ ) = (1.80 ± 0.37 ± 0.23) x 10-4 stat syst FPCP06 11-Apr-2006 K. Varvell

BaBar Full Recon Tag B  π l+  hep-ex/0507085 211fb-1 (233M BB) 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) p0 p- mγγ Yield 36 -lν, 34 0lν FPCP06 11-Apr-2006 K. Varvell

BaBar Full Recon Tag B  π l+  hep-ex/0507085 Extract partial BF in 3 q2 bins p- p0 B(B0  π- l+ ) = (1.14 ± 0.27 ± 0.17) x 10-4 stat syst B(B+  π0 l+ ) = (0.86 ± 0.22 ± 0.11) x 10-4 stat syst B(B  π l+ ) = (1.28 ± 0.23 ± 0.16) x 10-4 Combined + + 0 stat syst |Vub| = (3.7 ± 0.3 ± 0.2 ) x 10-3 -0.5 +0.8 + + 0, HPQCD stat syst FF norm FPCP06 11-Apr-2006 K. Varvell

Summary of B(B  π l ) Exclusive p- p0 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 FPCP06 11-Apr-2006 K. Varvell

Summary of |Vub| from Exclusive B  π l  HFAG Winter 2006 Experimental q2 shape input not used (yet) Using FF calculated in region of applicability Using FF extrapolated to full q2 range FPCP06 11-Apr-2006 K. Varvell

Other B  Xu l  Exclusive Modes Expt Mode BF [10-4] Reference CLEO B0  ρ- l  2.17±0.34 ±0.41 2.69±0.41 ±0.50 BaBar 2.57±0.52±0.59 B0  ρ- e  3.29±0.42±0.47±0.60 2.14±0.21±0.51±0.28 Belle 2.17±0.54±0.31±0.08 B+  η l  0.84±0.31±0.16±0.09 B+  ρ0 l  1.33±0.23±0.17±0.05 B+  ω l  1.3±0.4±0.2±0.3 Tag +0.47 -0.54 Untagged PRD 68 (2003) 072003 +0.35 -0.47 Untagged PRD 61 (2000) 052001 Full hep-ex/0408068 Untagged PRL 90 (2003) 181801 Untagged PRD 72 (2005) 051102 SL hep-ex/0604024 Untagged PRD 68 (2003) 072003 SL hep-ex/06xxxxx Untagged PRL 93 (2004) 131803 HFAG Compilation, except with updated Belle SL result included FPCP06 11-Apr-2006 K. Varvell

BaBar Exclusive |Vcb| Measurement hep-ex/0602023 Update to PRD 71 (2005) 051502 submitted to PRD Multi-Dimensional fit to helicity amplitudes for 2 (slope parameter) and R1, R2 (FF ratios), all functions of H+,-,0(w). w = vB· vD* 79fb-1 (86M BB) FPCP06 11-Apr-2006 K. Varvell

BaBar Exclusive |Vcb| Measurement (cont) 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 cosθV χ |Vcb| = (37.6 ± 0.3 ± 1.3 ) x 10-3 +1.5 -1.3 theo stat syst FPCP06 11-Apr-2006 K. Varvell

Summary of Exclusive |Vcb| Measurements HFAG Winter 2006 Note: Does not include latest BaBar result from hep-ex/0602023 FPCP06 11-Apr-2006 K. Varvell

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 shape measurements 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. FPCP06 11-Apr-2006 K. Varvell