1. e+e−→ J/ D(*)D(*) & ψ(4160) → DD
P. Pakhlov
(ITEP)
for the Belle Collaboration
BES-Belle-Cleo-BaBar Meeting, November 25, 2007

2. Introduction
Charmonium above open charm threshold decaying to open charm are seen in
ee annihhilation (via ISR at B-factories or energy scan at charm factories)
ee  double charmonium production
X(3940)
DD*
(4415) ???
DD*
More here?
one state is found in γγ
(4040)
D*D*
(4160)
c2’ DD
02/04/2019
P. Pakhlov

3. New study of e+e−  J/ D(*)D(*)
Monte Carlo
The method is pioneered by Belle Phys. Rev. Lett. 98, (2007)
Reconstruct J/ and one of
two D (or D*)
Unreconstructed D(*) is seen
as a peak Mrecoil (J/ D(*))
M ~ 30MeV < MD* – MD  D and D* recoiling against reconstructed J/ D(*) are well separated (~2.5)
e+e−  J/ DD(*) with J/ D reconstruction
Cross talk e+e−  J/ DD
to e+e−  J/ DD* ~ 15% due to ISR
J/ψ D e- D*  D e+
M(Dπ) ~ MD* if MDD* is around the threshold
02/04/2019
P. Pakhlov

4. e+e−  J/ D(*)D(*) signals in the data
693fb-1 D*
D*π D
arXiv:
Signals for all three processes are well seen in the data
e+e− J/ DD* and e+e− J/ D*D* are seen with both D and D* reconstruction
Backgrounds are combinatorial
Simultaneous fit to D-signal
and D-sidebands to fix bg
Monte Carlo:
All signals are > 5
02/04/2019
P. Pakhlov

5. e+e– J/D D
D D
3.8  D
Tag unreconstructed D:
|Mrecoil (J/ D) - M D | < 70MeV
Refit Mrecoil (J/ D) M D :
improve M DD resolution by ~10
Broad threhsold enhancement at MDD is not consistent with non resonant DD production in the process e+e−  J/ DD
However:
large fitting systematic error in the parameters of this enhancement
Significance is still low
No definite conclusion! but this study is needed to fix cross talk to e+e−  J/ DD*
02/04/2019
P. Pakhlov

6. D*-reconstructed D-tag
e+e– J/DD* and D*D D*
X(3940)
D reconstructed D*tag
6.0 
ee  J/ DD reflection D
M = ±6 MeV
tot = ±12 MeV
N = ±11 +7 –6
+26
–15
D*-reconstructed D-tag
X(3940)
cross check
3.8 
+24
–16
X(3940)DD* confirmed with new data
M and  are in agreement with published results.
02/04/2019
P. Pakhlov

7. D*reconstructed D*tag
e+e−  J/ D* D*
5.5 
X(4160)
D*reconstructed D*tag D*
M=( 15)MeV/c2
 =( 21)MeV
Broad clear peak at threshold
New state X(4160)(C=+1) ≠ ψ(4160)(C=–1) is observed in D*D* decay mode
+25
−20
+111
−61
One more state to explain …
JPС=0− + (c (4S)) is not excluded
Born cross-sections for two observed states
comparable to other double charmonium cross-sections
02/04/2019
P. Pakhlov

8. Systematics & cross checks
Systematics in masses and widths are dominated by fitting uncertainty (BW and bg parameterizations)
Production systematics is dominated by uncertainty in due to unknown angular distributions
Cross checks:
with different D sb windows
with different D subsamples
for X(3940)/X(4160) with D and D* reconstructions
give consistent results
02/04/2019
P. Pakhlov

9. e+e−  D0D–+ at s ~ 4−5 GeV via ISR
Phys. Rev. Lett. 98, (2007): D*D + D*D* 
Different reconstruction methods used for different hadronic final states:
DD* & D*D* – partial reconstruction of D* + detection of ISR photon
DD & D0 D− + – full reconstruction of hadronic part; ISR photon detection is not required (but used if in the detector acceptance) e- e-
reconstructed
D(*) e+
s=(Ecm-E)2-p2  D* D
not reconstructed but constrained
arXiv: : DD
not reconstructed if undetectable  e- e- D e+
s=(Ecm-E)2-p2 
reconstructed D
02/04/2019
P. Pakhlov

10. e+e−  D0D–+ at s ~ 4−5 GeV via ISR
Consistent with ISR production
670 fb-1
D0 D− +
full reconstruction
no extra tracks
similar analysis and bgs to e+e−  DD
no major bgs except for combinatorial
Clear (4415)DD signal
02/04/2019
P. Pakhlov

11. Resonant structure in (4415)DD
M(D0+) vs M(D-+) from (4415) region
Clear D*2(2460) signals
Positive interference
Non D*2(2460) contribution is not seen
DD non DD*2(2460)
DD*2(2460)
~10σ
670 fb-1
arXiv: , accepted by PRL
M = 4411± 7 MeV
tot =77±20 MeV
Nev= 109± 25
Consistent with BES,
hep-ex/ ,
PDG06, Barnes et.al
Phys. Rev. D72, (2005)
σ(e+e-(4415))×Br((4415)DD*2(2460))×Br(D*2(2460) D)=(0.74±0.17±0.07)nb
Br((4415)  D(D)non D2(2460))/Br((4415) DD*2(2460))<0.22
02/04/2019
P. Pakhlov

12. Decomposition of inclusive cross-section
D*D*
DD*
Phys. Rev. Lett. 98, (2007) DD
NEW
arXiv:
submitted to PRD(RC) 2 + +
DDπ
NEW
arXiv: , submitted to PRL = 2
uds-continuum
Anything else?
These 4 final states almost
saturate inclusive cross section
02/04/2019
P. Pakhlov

13. is confirmed with a significance ~ 6.0 X(4160)
Summary
X(3940)
is confirmed with a significance ~ 6.0
X(4160)
NEW state observed for the first time ~ 5.5 
(4415)
(4415)  DDπ signal observed, dominated by (4415)  DD**2
DD + DD + D*D + D*D* cross section is close to
ee  hadrons (  ee  uds continuum); still a room for (4415)  open charm final states exists!
02/04/2019
P. Pakhlov