1. On Behalf of the BaBar Collaboration
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
 Pseudoscalar decays: D → P (P=K,,…)
 Vector decays: D(s) → V (V=K*,, , …)
 S-wave systems
 Conclusions
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3. Motivation  Understand (by measuring) non-perturbative QCD
→ Expressed in terms of form factors
(for semileptonic decays)
→ Computed by Lattice-QCD
Outcome:
 Validation for the B sector
(avoiding fake New Physics hints!)
 Study of JP=0+ states (S-wave systems) in a non-hadronic
environment
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4. Experiments and data: >1ab-1 BES III 3 fb-1 550 fb-1 CLEOc 7 fb-1
cc ~1.3 nb
DD ~6 nb
CLEOc
7 fb-1
CLEO III
0.82 fb-1
~1M cc
+BeO
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5. Methods  FOCUS:  CLEOc & BES III :  BaBar:  BELLE: @ (3770)→DD
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
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6. D→P f+K(q2) f+(q2) Vcs, Vcd HQL 2012 A. Oyanguren 6
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:
FNAL and MILC
arXiv:
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7. Form factors HQL 2012 A. Oyanguren 7 Simple pole Modified pole ISGW2
Model prediction:
D→K mD*s = GeV/c2
D→ mD* = 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
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8. D→P @ B-factories: (Analysis with ~ 1/7 BaBar stat.)
(Analysis with ~ ¼ Belle stat.)
PRD 76 (2007)
PRL 97 (2006)
126  12
281 fb-1
106  13
73980
D0K-l+
mn² / GeV²
= (mD*-mD0)
data
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9. D→P @ threshold: HQL 2012 A. Oyanguren 9 -
 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)
0.9fb-1
BES III Preliminary
CLEO –c
818 pb-1
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10. D→K HQL 2012 A. Oyanguren 10  Results on form factors: Simple pole
Modified pole
arXiv:
mpole far from theoretical
Expectations mDs* =2.112 GeV
→ High precision measurements
→ Agreement ?
pole<1 as expected
Contributions from
other states
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11. D→K HQL 2012 A. Oyanguren 11 Series expansion
 Results on form factors:
Physics interpretation?
Provided by L. Gibbons (HFAG)
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12. D→ HQL 2012 A. Oyanguren 12  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)
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13. D→P HQL 2012 A. Oyanguren 13  Form factor normalization: D→K D→
(HFAG prel.)
Experimental accuracy below 1% !
D→
(HFAG prel.)
Good agreement between lattice and experiments
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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, (2005)
 Sensitive to the K S-wave (JP=0+ )
@ Babar:
PRD 83 (2011)
347fb-1
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15. D→K HQL 2012 A. Oyanguren 15  Form factors mesurement:
 Detailed mesurement
of the D→K channel:
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16. D→K HQL 2012 A. Oyanguren 16 @ CLEO-c:
Measure the q2 dependence of helicity form factors in D→K
PRD81, (2010)
 Comparison with BaBar results:
PRD 83 (2011)
Form factor component
Good agreement
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17. K S-wave HQL 2012 A. Oyanguren 17 •S-wave contribution @ BaBar: BaBar
PRD 83 (2011)
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+
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18. D→ HQL 2012 A. Oyanguren 18 @ 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
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19. Ds→
BaBar same reconstruction technique as previous
analyses ( ~1/2.5 BaBar stat.) D- Ds +  e+ K+ K-
PRD78 (2008) (RC)
Determination
of form factors:
214 fb-1
BaBar
In agreement with Lattice:
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20. KK S-wave BaBar HQL 2012 A. Oyanguren 20  First evidence of a S-wave:
Small contribution (0.22% in the  region)
PRD78 (2008) (RC)
BaBar
BaBar
Interference with 
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→,
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21. Ds→f0 HQL 2012 A. Oyanguren 21 @ CLEOc (4176 MeV):
PRD 80 (2009)
@ 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
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22. Conclusions  Many results in different channels
 New data BESIII
 Only partial data analyzed at B-factories
 |Vcs|f+K(0) accuracy at 1%
 |Vcd|f+(0) accuracy at 2%
 Precise Lattice results to be compared with,
in agreement with experiments
 Important informations on the S-wave systems
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23. and to my 5-year-old daughter Maia for the background picture
Thank you
Special thanks to P. Roudeau and L. Gibbons for the averages
and to my 5-year-old daughter Maia for the background picture