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Charm Semileptonic D ecays

Charm Semileptonic D ecays. A. Oyanguren. (IFIC – Valencia). On Behalf of the BaBar Collaboration. Heavy Quarks and Leptons 2012, Praga. 11-May-2012. Outline.  Motivation.  Experiments and methods.  Pseudoscalar decays : D → P   (P=K, ,…).

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Charm Semileptonic D ecays

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  1. Charm Semileptonic Decays A. Oyanguren (IFIC – Valencia) On Behalf of the BaBar Collaboration Heavy Quarks and Leptons 2012, Praga 11-May-2012

  2. Outline Motivation Experiments and methods Pseudoscalardecays: D → P (P=K,,…) Vector decays: D(s)→ V (V=K*,, , …) S-wave systems Conclusions A. Oyanguren HQL 2012 2

  3. Motivation Understand (bymeasuring) non-perturbative QCD → Expressed in terms of formfactors (forsemileptonicdecays) → ComputedbyLattice-QCD Outcome: Validationforthe B sector (avoidingfake New Physicshints!) Study of JP=0+states (S-wave systems) in a non-hadronic environment A. Oyanguren HQL 2012 3

  4. Experiments >1ab-1 and data: BES III 3 fb-1 550 fb-1 cc ~1.3 nb DD ~6 nb CLEOc 7 fb-1 CLEO III 0.82 fb-1 ~1M cc +BeO A. Oyanguren HQL 2012 4

  5. Methods @ (3770)→DD  FOCUS: Reconstruct the D*→D, and the D in the semimuonic channel (or D→K)  CLEOc & BES III : - Tagged: Full reconstruction: one D in a hadronic channel, the other in the semileptonic channel (only the  is missing) - Untagged (CLEOc): lepton + hadron from the D, Emiss of the event = E CLEOc @ (4s) (cc)  BaBar: Partial reconstruction of cc events, the D*→D and the D in the Ke channel (or the D(s)→Vee ). D(s) direction and E from the rest of the event (untagged)  BELLE: Full reconstruction of cc events including hadronization particles, one D into hadrons, the other in the sl channel, only  is missing (tagged) BaBar A. Oyanguren HQL 2012 5

  6. D→P • Known angular distribution •  sin2() • Cabibbo favoured D→K and • suppressed D→ Vcs, Vcd  Only one form factor in the differential decay width f+(q2): q2=(pD – pP)2= (p + p)2  New Lattice QCD computations: f+K(q2) f+(q2) FNAL and MILC arXiv:1111.5471 FNAL and MILC arXiv:1111.5471 A. Oyanguren HQL 2012 6

  7. Formfactors Simple pole Model prediction: D→K mD*s = 2.112 GeV/c2 D→ mD* = 2.010 GeV/c2 Modified pole Lattice computation: D→K apole= 0.50(4)(7) D→ apole= 0.44(4)(7) ISGW2 Model prediction: D→K, D→ aI ~ 0.1 GeV-2 Series expansion No model predictions r1 = a1/a0 r2 = a2/a0 t  q2 |z| << 1 A. Oyanguren HQL 2012 7

  8. D→P @ B-factories: (Analysis with ~ 1/7 BaBar stat.) (Analysis with ~ ¼ Belle stat.) PRD 76 (2007) 052005 PRL 97 (2006) 061804 126  12 281 fb-1 106  13 73980 D0K-l+ mn² / GeV² = (mD*-mD0) data A. Oyanguren HQL 2012 8

  9. D→P - @ threshold:  NEW results from BES III (1/3 total stat.): D0 K+ ’’ 0.9fb-1 BES III Preliminary D0 e+ e -  CLEO –c also reconstruct the D+ →(,’)ee using tagged and untagged (GR) methods PRD 84 (2011) 032001 0.9fb-1 BES III Preliminary CLEO –c 818 pb-1 A. Oyanguren HQL 2012 9

  10. D→K  Results on form factors: Simple pole Modified pole arXiv:0906.2498 mpole far from theoretical Expectations mDs* =2.112 GeV → High precision measurements → Agreement ? pole<1 as expected Contributions from other states A. Oyanguren HQL 2012 10

  11. D→K Series expansion  Results on form factors: Physics interpretation? Provided by L. Gibbons (HFAG) A. Oyanguren HQL 2012 11

  12. D→  Results on form factors: Simple pole Modified pole mpole far from theoretical expectations mD* =2.010 GeV pole<1 as expected Info from contributions from other states Series expansion Provided by L. Gibbons (HFAG) A. Oyanguren HQL 2012 12

  13. D→P  Form factor normalization: D→K (HFAG prel.) Experimental accuracy below 1% ! D→ (HFAG prel.) Good agreement between lattice and experiments A. Oyanguren HQL 2012 13

  14. D→K • The decay rate depends on 5 variables: mV, q2,v , l , • For vector decays (D→K*) two form factor ratios are • introduced: A1(q2),A2(q2), and V(q2)shapes: single pole or Fajfer and Kamenik PRD 72, 034029 (2005)  Sensitive to the K S-wave (JP=0+ ) @ Babar: PRD 83 (2011) 072001 347fb-1 A. Oyanguren HQL 2012 14

  15. D→K  Form factors mesurement:  Detailed mesurement of the D→K channel: A. Oyanguren HQL 2012 15

  16. D→K @ CLEO-c: Measure the q2dependence of helicity form factors in D→K PRD81,112001 (2010)  Comparison with BaBar results: PRD 83 (2011) 072001 Form factor component Good agreement A. Oyanguren HQL 2012 16

  17. K S-wave •S-wave contribution @ BaBar: PRD 83 (2011) 072001 BaBar •Same phase variation in D→K decays and Kπ scattering in the elastic regime (Watson’s theorem) → BaBar and LASS agree well • Helpful to understand the effect of the spectator π in D+ →K- π+ π+ A. Oyanguren HQL 2012 17

  18. D→ @ CLEOc : arXiv:1112.2884 [hep-ex] - With full reconstruction also measure the suppressed decay De () 818 pb-1 CLEOc In agreement with Fajfer and Kamenik A. Oyanguren HQL 2012 18

  19. Ds→  @ BaBar same reconstruction technique as previous analyses ( ~1/2.5 BaBar stat.) e+  + Ds K+ PRD78 (2008) 051101 (RC) K- D- Determination of form factors: 214 fb-1 BaBar In agreement with Lattice: A. Oyanguren HQL 2012 19

  20. KK S-wave  First evidence of a S-wave: Small contribution (0.22% in the  region) PRD78 (2008) 051101 (RC) BaBar BaBar Interferencewith 214 fb-1 Important for s measurements: → Expected contribution of the S-wave in the Bs→J/ KK channel below 1% (in the same m). This in agreement with D0, CDF and LHCb observations  For D→, A. Oyanguren HQL 2012 20

  21. Ds→f0 PRD 80 (2009) 052009 @ CLEOc (4176 MeV): - D→KK and D→ using the full reconstruction method In addition to the , they also observe the f0 (980) (→ ) (0+ state) 600 pb-1 CLEO-c The ratios of the decay rates at q2=0: Simple pole BaBar form factors Important to measure CPV in the Bs→J/ f0 channel A. Oyanguren HQL 2012 21

  22. Conclusions Manyresults in differentchannels  New data coming@ BESIII Onlypartial data analyzed at B-factories  |Vcs|f+K(0) accuracy at 1%  |Vcd|f+(0) accuracy at 2%  Precise Latticeresultstobecomparedwith, in agreementwithexperiments Importantinformationsonthe S-wave systems A. Oyanguren HQL 2012 22

  23. Thankyou Special thanks to P. Roudeau and L. Gibbons for the averages and to my 5-year-old daughter Maia for the background picture

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