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Experimental methods for precise determination of CKM matrix sides

Experimental methods for precise determination of CKM matrix sides. Introduction Present status V td , V ts : B mixing Rare B decays V cb , V ub : Semileptonic decays B  Charm physics Overall status and future B factories : LHCb : Radiative B decays B s mixing.

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Experimental methods for precise determination of CKM matrix sides

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  1. Experimental methods for precise determination of CKM matrix sides • Introduction • Present status • Vtd, Vts : • B mixing • Rare B decays • Vcb, Vub : • Semileptonic decays • B • Charm physics • Overall status and future • B factories : • LHCb : • Radiative B decays • Bs mixing Marie-Hélène Schune Member of the BaBar and LHCb collaborations LAL-Orsay

  2. Introduction

  3. Framework : the CKM matrix Vud Vus Vub Vcd Vcs Vcb Vtd Vts Vtb d’ s’ b’ d s b = Mass eigenstates  weak interaction eigenstates  mixing matrix : the Cabbibo-Kobayashi-Maskawa matrix Weak interaction eigenstates Mass eigenstates CKM matrix Transition amplitude between the quarks i and j : Vij W b u Vub Vij complex  CP violation Wolfenstein parametrisation 1-2  A 3(-i) - 1- 2/2 A 2 A3(1- -i) -A 2 1 + O(4)

  4. 1-2  A 3(-i) - 1- 2/2 A 2 A3(1- -i) -A 2 1 3 families + CKM matrix unitarity  4 parameters CKM : present status Relations between the CKM matrix elements The unitarity triangle 4 parameters known with different precisions : =sin(c) ~0.4 % A ~ 1.7 %  ~ 15 %  ~ 5 %  (,) /2 (1,0)  /3  /1  (0,0)

  5. Some of the experiments e+e-(4s) pp s=14 TeV BELLE BABAR LHCb pit june 2006 CDF D0 pp s=1.96 TeV

  6. Present status

  7. Vtd and Vts • top quark couplings • loop or box diagrams Search for New Physics Radiative B decays d s r K* Top quark contribution dominates b B B mixing : Top quark contribution dominates Bd,s Bd,s Bd,s Bd,s 0 0 0 0 Vtb Vtb Vtb Vtb W b b b d d t s s t t W W Vtd Vtd Vtd Vtd t d d Vts Vts Vts Vts W s s

  8. B0-B0 oscillations Time-dependent probability for a produced at t=0 to be observed as a or at time t Can be predicted in the SM framework Non-perturbative QCD perturbativeQCD Reconstruct the decay time (t) Tag the B production state : Other B information (B factories and pp colliders) Same side tagging (for pp colliders only/ Bs) 

  9. B0-B0 Oscillations: Dmd Asymmetry  cos(Dmdt) Dmd = 0.5070.004 ps-1 Dmd : a high precision measurement (~0.8%) dominated by B factories results |Dt| (ps) HFAG BELLE 152 106 BB . Full B reconstruction Weak constraint on the UT triangle due to the knowledge of  use SU(3) flavour breaking smaller theoretical uncertainties Due to the size of the CKM elements Dms >> Dmd =1

  10. Bs-Bs oscillations: Dms ( ) ( ) LEP/SLD 1999 Dms : already a high precision measurement (~2.3%) CDF 2006 LEP/SLD 2002 • Several analysis from LEP, SLD, Tevatron • Combine different limits : the amplitude method • measurement of A at each Dms • At a given Dms : • A=0 : no oscillation • A=1 : oscillation • Dms excluded at 95% CL : A+1.645sA<1 • Sensitivity : same relation with A=0 HFAG First limit was set in 1993 at Dms>1.8 ps-1 at 95%CL !

  11. Implications of Dmd/ Dms measurements on the CKM parameters determinations Two very precise measurements : (~0.8 % and 2%) Indirect measurement of Dms (prediction) : But it does not translate into a precise determination of the SM parameters …  known to 5-8%

  12. Radiative B decays d s • New Physics • BF of bsg and bdg • Standard Model • Eg spectrum in b sg  |Vcb| and |Vub| • BF(bsg)/BF(bdg)  |Vtd|2/|Vtd|2 BR(b  d )  |Vtd|2 BR(b  s) |Vts|2 bs Inclusive photon energy spectrum sensitive to b-quark motion inside B meson  reduces the systematic uncertainty in the Vcb and Vub extractions Semi-inclusive analysis (~55% of the modes reconstructed) K* peak visible due to the good resolution

  13. B/  68%CL r 95%CL Full UT fit signal K*g qq other B SU(3) breaking correction weak annihilation diagram for BR(B  /w ) < 1.2 10-6 at 90% CL First observation: 5.5s Expect new BaBar results at ICHEP With the present statistics : use of all the modes, in future rg only ?

  14. Semileptonic decays: Vub and Vcb Vcb or Vub Weak decay of a free quark : G0 At the hadron level : free quark decay Perturbative +non-perturbative corrections Exclusive decays: depend on QCD form factors from eg LQCD, quark models... Inclusive decays : use Heavy Quark symmetry+ OPE measure OPE parameters from data (spectra and moments of bsg and b  cℓn distributions) Complication for charmless decays:  need to apply kinematic cuts to suppress b  cℓn background  measurements of partial branching fractions in restricted phase space regions  theoretical uncertainties more difficult to evaluate Exclusive and inclusive semileptonic approaches : different theoretical uncertainties

  15. Vcb from semileptonic decays ~5% precision Vcb exclusive Vcb inclusive (Buchmüller/Flächer): |Vcb|= (41.960.23exp 0.35HQE0.59GSL)10-3 |Vcb|F(1)= (37.60.8)10-3 ~2% precision r2 |Vcb|= (41.32.0)10-3 with F(1) = 0.91  0.04theo Does not contain the latest result from BaBar : |Vcb|= Good agreement

  16. Vub in inclusive B decays In these regions the theory (OPE) breaks down, acceptance sensitive to Fermi motion of b quark inside the B meson Several approaches : signal

  17. Vub exclusive : Bℓ Bℓ B 0 ℓ B + ℓ  = missing of the event ; can add Breco tag to improve S/B • Measure the form factor q2 dependance. • Compare with theoretical calculations signal p-ℓn r-ℓn Missing mass2 Yields : 36 -ℓn, 34 0ℓn Various experimental results in good agreement p0ℓn r0ℓn BF(B ℓ ) precision~8%

  18. Vub from semileptonic decays summary Vub determination from exclusive decays Vub inclusive (HFAG) ~8% precision BF precision~8% but |Vub| precision ~20%  theory dominated |Vub|~ (4.40.2 0.3 )10-3 inclusive |Vub|~ (3.70.2 0.7 )10-3 exclusive Understanding of the difference ?

  19. B ~216 signal events Vub Using |Vub| from HFAG : • In the SM it measures fB |Vub| • Direct measurement of fB when using |Vub| from SL decays (to be compared to LQCD predictions) • Test of NP (e.g.: charged Higgs could enhance BF) • Experimental technique • One B fully reconstructed (hadronic or semileptonic) • Search for  in the rest of the event (2n) Electromagnetic energy not associated with the Btag nor the p0 from the t decay (GeV) 4.2s

  20. Charm physics + Measurements of fD+ and fDs improved prediction of fB/fBs precise measurements of Dmd and Dms precise determination of Vtd/Vts parameters Validation of LQCD (DK ℓ ) Vcd precise determination of Vub/Vcb parameters Extraction of D form factors D BF measurements B form factors (D /ℓ)

  21. Measuring fD and fDs Preliminary • Pseudo scalar decay : Vcd D*S DSg  m n g and normalize to Dsf p  wave function overlap CLEO-c 281 pb-1 Nmn = 489±55 50 events NBkgd=2.920.50 Ds→mn signal stat syst Ds→fp LQCD Aubin et al. PRL 95 122002 (2005) Recent lattice result (hep-lat/0506030)

  22. Semi-leptonic D decays CLEO-c (~117 events) DK ℓ form factor : comparison of recent experimental results with LQCD calculation Events / 10 MeV U ( = Emiss – |Pmiss| ) CLEO BF relative to PDG

  23. Overall status and future

  24. Phases and sides measurements in good agreement Preferred region using only the sides measurements The CKM mechanism works well… NP should appear as correction to this framework

  25. Future from the sides point of view : the B factories • The existing B factories will collect about 1 ab-1 (X2 present samples) per experiment • B measurement will improve  confrontation with LQCD predictions • B/  determination will improve • Vub analyses will be able to discriminate between theoretical models  improved Vub extraction • B factories : charm factories ! • Super B factory ? • Japanese project, based on KEK2 experience : 40 ab-1 before 2020 • More futuristic : Italian project (linked to ILC development) : 50 ab-1 before 2015 • Improvement of all the above points : • eg : expect few thousands BR(B) signal events !

  26. Future from the sides point of view : LHCb Full simulation of bb inclusive events Use of radiative B decays : Analysis complicated by the presence of a p0 Bdr0 should be easier BELLE has ~6 signal events in this mode LHCb 2005-01 But the extraction of |Vtd/Vts| is not completely clean from a theoretical point of view (SU(3) breaking, presence of a weak annihilation diagram in r/  (and not in K*)

  27. Very precise measurement of Dms using Bs Ds(KK ) events : Expected unmixed BsDs sample in one year of LHCb data taking One year of data taking (2fb-1) : 80k fully reconstructed events with B/S~0.3 and (t) ~40 fs LHCb 2003-127 Recent NN approaches lead to ~9% for Bs The tagging performances will be checked on data (similar self tagging decay modes, double tagging technique Ksame) (ms) will be dominated by the systematics (eg knowledge of the time scale)

  28. And then … fBBB ~ 5% x ~ 3% BK ~ 5% Lattice QCD 2010 : B factories 2 x 1 ab-1 LHCb : 4 fb-1 Vub ~ 5% Vcb ~ 1% (ms) = 0.3 ps-1 • b < 1° • ~ 7 ° • ~ 5°(half B-factories/half LHCb) Theoretical inputs Experimental inputs Hopefully this picture will not be the one we will see in 2010 and sides and angles measurements will be incompatible ! Preferred region determined by sides measurements Sides and angles determination of (r,h) : similar precision

  29. Summary Hadronic colliders : Very precise measurement of the Bs–Bs mixing frequency Measurements of BK*, Bs and B/  All modes with neutrinos are difficult in hadronic environment B factories : Vcb and Vub determinations More and more inputs from data to constraint the theory  improved Vub and Vcb measurements. fB extraction from B measurement Increasing role of charm physics which provide high-quality “lattice calibration”  improvement on the precision of the CKM parameters Many new results expected for ICHEP !

  30. Backup slides

  31. Constraints in the (,) plane 2 sides ; 3 angles  aim : to overconstrain this unitarity triangle precision test of the Standard Model Bccs : 1 /b K : CPV in K decays bcℓ and buℓ Bd and Bs mixing B// : 2/ BDK : 3/

  32. The “B” experiments : main characteristics

  33. Experimental techniques at B factories BB events coherent BB production qq events (q=u,d,s,c) B-Flavour tagging Exclusive B meson reconstruction Dt=1.6 ps Dz 200, 250 mm Exploit kinematic constraints from beam energies Beam Energy-substituted mass Energy difference Event shape (4S) rest frame s(DE) : mode dependent s(mES)  3 MeV

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