Transcript e+e−→ open charm via ISR X(4160) in J/ recoil Quarkonium Working Group, October 20, 2007

e+e−→ open charm via ISR
X(4160) in J/ recoil
Quarkonium Working Group, October 20, 2007
Experiment Belle
“An unexpected bonus from the B-factory experiments has been
the discovery of a large number of charmonium-like meson states…”
06/11/2015
Galina Pakhlova
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e+e− open charm final states
R-study around open charm threshold
e+e- machines at s ~(3.7 -5) GeV
•
•
•
PDG 2006
inclusive e+e-  hadrons
cross-section
complicated structure
model and fit dependent
description
For years no exclusive studies
e+e-  specific final states
Last years new interest both in
experiment and theory
A lot of new data!!!
Y(4260)
06/11/2015
Galina Pakhlova
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Exclusive e+e−D(*)D* cross-sections via ISR

ee+
e-
s=(Ecm-E)2-p2
D(*
)
D*

D not reconstructed
but constrained
Method
ISR at B-factories comparable with energy scan (CLEOc, BES)
• Hard ISR photon takes away significant fraction of energy
• Continuous ISR spectrum: access to whole s interval
• em suppression, but ~ 700/fb at Belle vs ~ 60/pb CLEO-c
The first measurement
Belle: D*+D*-, D+ D*- with partial reconstruction
• increase eff ~ 10 − 20 times
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Galina Pakhlova
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e+e-D(*)D* with partial reconstruction
Phys. Rev. Lett. 98, 092001 (2007)
Full reconstruction D(*) ISR
D+ D*-
D*+D*-
• wide peak in Mrec(D(*)ISR) at M D*
• contribution from e+e-D(*)D* (n)πγ
MD*
MD*
with ΔMrec cut
Mrec(D*+ISR)
Full reconstruction D(*) ISR + slow
from unreconstructed D*
• wide peak in Mrec(D(*)-ISR) at MD
Mrec(D+ISR)
Use recoil mass difference
ΔMrec = Mrec(D(*)ISR) - Mrec(D(*)ISR)
• narrow peak at (MD* - MD)
RMD~1 MeV
ΔMrec
06/11/2015
•
cancellation of momentum smearing
Tight ΔMrec cut  small background
Use kinematical constraint
ΔMrec Galina Pakhlova Mrecoil(D(*) ISR)  MD* to improve
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resolution
Exclusive e+e–D(*)D* cross-sections
Phys. Rev. Lett. 98, 092001 (2007)
D*+D*-
CHARM 2007
(4160)
D* D*
Charged D(*)D*
½ from CLEOc
(4040)
(4160)
D+D*-
(4040)
DD*
Y(4260)
550/fb
• Systematic errors ≈ statistical errors Y(4260) signal
• Submitted to Durham database
DD* : hint, but not significant
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Galina Pakhlova
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D*D* : clear dip (similar to inclusive R)
e+e−  DD at s~3.7−5 GeV via ISR
D0D0 or D+D– (full reconstruction)
 no extra tracks
detection of ISR is not required
if ISR is detected
M(DD ISR) is required ~ Ecm
D0D0
DD
D+D–
670 fb-1
ISR is not detected
ISR is detected
Combinatorial bgs are estimated from D s/b
 Other bgs are small and taken into account

Consistent with ISR production
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Galina Pakhlova
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Mass spectra of DD
arXiv:0708.0082
(4160)
(4415)
arXiv:0710.1371
(4040)
(4040)
(4160)
Y(4260)
Y(4260)
670 fb-1
(4415)
384 fb-1
no signal Y(4260)DD
Belle&BaBar are in a qualitative agreement
06/11/2015
Galina Pakhlova
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(e+e–  DD)
(4040)
(4160)
670 fb-1
(3770)
(4415)
(4040)
Charm 2007
DD
(4160)
Phys. Rev. Lett. 98, 092001 (2007)
Broad structure around 3.9 GeV
is in qualitative agreement ??
with coupled-channel model
D*D*
Phys. Rev. D21, 203 (1980)
σ(ee 

0.720.160.06
D+D−)/σ(ee
D0D0)
=
at MDD≈M(3770)
06/11/2015with BES/CLEOc
is consistent
Cross section above 4 GeV
has a similar shape to this
measured for ee  D*D* ?
Galina Pakhlova
DD*
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e+e−  D0D–+ at s ~ 4−5 GeV via ISR
670 fb-1
D0 D− +
 full reconstruction
 no extra tracks
 similar analysis and bgs
 no major bgs except
06/11/2015
for combinatorial
Clear (4415)DD signal
Galina Pakhlova
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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
arXiv:0708.3313, submitted to PRL
670 fb-1
M = 4411± 7 MeV
tot =77±20 MeV
Nev= 109± 25
DD*2(2460)
~10σ
DD non DD*2(2460)
Consistent with BES,
hep-ex/0705.4500,
PDG06, Barnes at.al
Phys. Rev. D72, 054026 (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
06/11/2015
Galina Pakhlova
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Contributions to the inclusive cross-section at 3.7-5GeV
Phys. Rev. Lett. 98, 092001 (2007)
NEW
D*D*
2
DD*
NEW
+
DD
arXiv:0708.0082
submitted to PRD(RC)
DDπ
=
2
arXiv:0708.3313, submitted to PRL
uds-continuum
Anything else?
These 4 final states almost
saturate inclusive cross section
06/11/2015
Galina Pakhlova
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+
New state in double charmonium
production
New study of e+e−  J/ D(*)D(*)
arXiv:0708.3812
D*
D*π
D
D*
693fb-1
D
The method is pioneered by
Belle Phys. Rev. Lett. 98, 082001 (2007)
Reconstruct J/ and one of
two D (or D*)
Unreconstructed D(*) is seen
as a peak Mrecoil (J/ D(*))
D and D* recoiling against
reconstructed J/ D(*) are well
separated (~2.5)
Simultaneous fit to D-signal
and D-sidebands to fix bg
All signals are > 5
06/11/2015
Galina Pakhlova
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e+e–J/DD
D
Tag unreconstructed D:
• |Mrecoil (J/ D) - M D | < 70MeV
Refit Mrecoil (J/ D) M D :
• improve M DD by ~10
Broad peak at MDD is not
consistent with non resonant
DD production in the process
e+e−  J/ DD
large fitting systematic error in
the parameters of this enhancement
06/11/2015
Galina Pakhlova
DD
3.8 
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e+e– J/DD* and D*D
D*
D reconstructed D*tag
D
ee  J/ DD reflection
6.0 
M = 3942 +7
±6 MeV
-6
tot =37 +26
±12 MeV
- 15
Nev= 52 +24
±11
- 16
* confirmed with new data
X(3940)DD
06/11/2015
Galina Pakhlova
M and  are in agreement with published results.
D*-reconstructed D-tag
3.8 
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e+e−  J/ D*D*
D*
Broad clear peak at threshold
• New state X(4160) ≠ ψ(4160) is
observed in D*D* decay mode
M=(4156−20 15)MeV/c2
+25
D*reconstructed D*tag
 =(139 −61 21)MeV
+111
5.5 
One more particle to explain …
JPС=0− + (hc (4S)) is not excluded
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Galina Pakhlova
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Summary
e+e− open charm
D*D*
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•
•
complicated shape of cross section
consistent with CLEO_c at MD*D* (3.8-4.3) GeV
clear dip at MD*D* ~ 4260GeV (similar to inclusive R)
DD*
• broad peak at threshold (shifted relative to 4040 GeV)
• consistent with CLEO_c at MDD* (3.8-4.3) GeV
• hint at MDD* ~ 4260GeV
DD
•
•
•
•
•
complicated shape of cross section
consistent with CLEO_c at MDD (4.0-4.3) GeV
σ(ee(3770)→DD) consistent with BES/CLEO_c
broad enhancement ~ 3.9 GeV – coupled channel effect?
above 4GeV similar shape as D*D*
DD
• (4415) signal observed, dominated by (4415)  DD**2
• DD + DD + D*D + D*D* cross section is close to
ee  hadrons ( - ee  uds continuum)
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Galina Pakhlova
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Double charmonium production
X(3940)
• is confirmed with a significance ~ 6.0
X(4160)
• NEW state observed for the first time ~ 5.5 
06/11/2015
Galina Pakhlova
あ
り
が
と
う
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