Recent V ub results from CLEO

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1 Recent V ub results from CLEO Marina Artuso Representing the CLEO Collaboration Beauty 2005, Assisi, June 20-25,

2 Quark Mixing Weak interaction couples weak eigenstates, not mass eigenstates: CKM matrix relates these two representations: λ λ Aλ 1 2 ρ iη λ λ 1 λ iηa λ Aλ ( 1+ iηλ ) Aλ ( 1 ρ iη) Aλ 1 weak V CKM mass Wolfenstein eigenstates eigenstates parameterization T To λ 3 in real part & λ 5 in im. part CKM unitary described by 4 parameters (3 real, 1 imaginary: e.g. A,λ,ρ,η) 2

3 η η The unitarity triangle in the r-h plane 1 V ub 1 V td λ V λ V cb ts η ρ 0 1 ρ m d m s 0 1 B ο B d mixing phase ρπ 8 o 8 o α B ο ψ K β ρ B s mixing phase o 7 o Bs D K S + + The triangle Magnitudes Can also measure γ via B - D o K - γ Bs ψη χ 0 ρ ( 5)% + ( 20)% ρ ν B Use different sets of measurements to define apex of triangle Also have ε K (CP in K L system) V ub

4 V ub extraction from inclusive charmless semileptonic decays In principle: easy and reliable: V ub == (3.06 ± 0.08 ± 0.08) 10 3 B ( B Xu ν ) τ ps B 1/2 Greatest uncertainty m b Non-perturbative effects small But Charm background 100 times charmless signal Experimental ingenuity needed [e.g. cuts] Theorists are kept busy evaluating and debating new sources of theoretical error 4

5 Where it all started: cut of the endpoint of the charged lepton spectrum ( a ) ( b ) Disadvantages: local OPE breaks down sensitivity to Fermi motion of the b quark f(k+) Motivated extraction of f(k+) from b sγ Alternative methods developed: either cutting on the hadronic invariant mass spectrum (m X <m D ): same problems with Fermi motion (function of the proximity of the cut to perturbative singularities) or q 2 >(m B -m D ) 2 5 Leptons / (50 MeV/c) Momentum (GeV/c)

6 Summary of techniques available to suppress charm background From Mile Luke- CKM2005 6

7 Theoretical issues Fermi motion at leading order (extracted from b sγ) and subleading order Weak-annihilation (common to all the methods) m b : rate proportional to m 5 b & restricting phase space increases sensitivity Perturbative corrections f(k + ): determine from the photon spectrum in B X s γ [subleading terms] 7

8 Weak Annihilation Weak annihilation in local OPE: An issue for tall inclusive determinations Relative size of the effect gets worse the more severe the cut Estimate: comparison between B 0 and B +, D,D s SL widths Weak annihilation in non-local OPE O Λ 2 2 QCD (16 π B ) 2 m B Can be >20% shift to integrated rate for E l >2.3GeV 8

9 CLEO study of WA in inclusive semileptonic decays Inclusive neutrino reconstruction analysis p ν from missing momentum and energy in BB event Signal leptons (e and µ): p l >1.5 GeV Data sample CLEO II +II.5 at Υ(4S) (9.7 fb -1 ) Event sample contains: Signal b u (spectator diagram + weak annihilation) Dominant b c background Continuum background e+e- qq Background from events with fake leptons Signal model: b u [hybrid approach combining exclusive model [ISGW2 for the lightest charmless final states + HQET motivated inclusive model to produce non-resonant n- body final states] + WA modeling 9

10 Model for WA Motivated by leading annihilation-like graph Most of the energy is carried by the l-n pair Hadronic system produced in the debris Kinematics driven by Λ QCD E x,m x,p x Λ Q 2 M B 2 - ΛMB Soft PDF: box with width x 0 and cutoff Λ o Model parameters varied through 5x6 values o Each 100K sample represents an realization of WA 10

11 On Υ(4S) + continuum data samples Fit Strategy MC: q 2 versus El Dalitz plot Binned χ 2 fit: p l : , ,>2.2 GeV 30 bins of q 2 (0-30 GeV 2 ) Float b u, b c,wa normalizations; fix fakes +cont 30 fits, one for each WA sample 11

12 Sample fit results (background subtracted) b u signal, including WA 12

13 Impact on a specific analysis R Γwa Γwa = Γ( b u) Γ ( b u) +Γ wa Γ wa E l >2.2 GeV P l >1 GeV, Mx<1.55 GeV CLEO data constrains results of WA as modeled to be small From fits 13

14 Exclusive B X u l ν results Heavy to light transition HQET is not expected to give predictions with the same level of accuracy as for B X c l ν Theoretical work theme: pin down regions of phase space where theoretical error small Use HQET to relate FF in B π l ν and D π l ν (Ligeti,Wise PDR D53, 4937 Use unquenched lattice QCD at high q2 Use double ratio * B K ee B ρ eν ν D ρ eν * D K e 14

15 To make progress It is important to make a good measurement of dγ/dq 2 Technique pioneered by CLEO, now data available also from BELLE Exploit very well understood ν reconstruction technique Extract B, dγ/dq 2, and V ub Based on CLEO II+ CLEO II.5 15

16 V ub from exclusive analysis B ρlν exp th V ub =(4.08±0.22(exp), ±0.40(lattice+SCET+disp))x