1. (University & I.N.F.N. of Bari)
Observation of two
narrow mesons
in the and
final states
Results from BABAR , CLEO & Belle
Alexis POMPILI
(University & I.N.F.N. of Bari)
[ Collaboration]
2003
Conversano - 15 June 03

2. Outline 2 QCD @ Work 2003 A.Pompili (U. of Bari & I.N.F.N.)
spectroscopy before new states observation
Charm B-factories – reconstruction method issues
Observation of the first new state - features
Feedback/explanations by theorists
Evidence for a second new state - features
Summary and conclusions 2
Work A.Pompili (U. of Bari & I.N.F.N.)

3. Spectroscopy of states
Potential models of [heavy-quark | light-quark] mesons have had so far
reasonable success in describing the spectroscopy of the D, Ds, B, Bs systems
S. Godfrey and N. Isgur, Phys. Rev. D32, 189 (1985); S. Godfrey and R. Kokoski, Phys. Rev. D43, 1679 (1991), M. Di Pierro and E. Eichten, Phys. Rev. D64, (2001)
Godfrey-Isgur model ?
[narrow] ?
Predicted mass range:
Predicted large width range :
(for decay by K-emission) ? ?
(mix?)
[narrow]
Limited
experimental
information
NO experim. candidates (so far)
IF their masses were below D(*)K
threshold, they would decay by
isospin-violating p-emission and
would be extremely narrow !
isospin-violating
The results presented here concern
2 states [0+,1+], below DK, D*K
threshold, decaying to Dsp0, Ds*p0 !
S-wave
P-wave 3
Work A.Pompili (U. of Bari & I.N.F.N.)

4. Charm Physics @ B-factories
e+e- Y(4S)
Beams
Data taking
Det./Expt.
[*]
CESR (Cornell)
Symmetric
CLEO-II
PEP-II (SLAC)
Asymmetric
Start: 1999
KEK-B (Tsukuba)
Belle
[*] Integrated Luminosity relative to the data sample used for the results presented here
The Y(4S) resonance “lays” on a large continuum bkgd :
Effective cross sections
at the energy of the Y(4S)
Powerful tool for
charm
physics 4
Work A.Pompili (U. of Bari & I.N.F.N.)

5. Charm Physics from Continuum Production
By using inclusive continuum events … combinatorial bkg is strongly reduced !
Solid (open) points: on (off) resonance data [normalized]
Kinematical selection: require cut on CMS momentum of charmed meson :
It can be increased for cleaner samples (if statistics allows) 5
Work A.Pompili (U. of Bari & I.N.F.N.)

6. 6 Reconstruction Method & Selection Criteria (from )
[charge-conjugate configurations are implied]
PID
not
sharing
photons
with others
geometric fit at
a common vertex :
consistent with production
at the interaction region
NOT IN SCALE
(or tighter)
gg couples (origin in track vertex)
with kinematic fit [constraint : m(p0)] :
gg couples (origin in production vertex)
with kinematic fit [constraint : m(p0)] : 6
Work A.Pompili (U. of Bari & I.N.F.N.)

7. Further background rejection
Select quasi-two body decay modes
2 disjoint
sub-samples
Helicity angles cut [ 2-body decays of ] 7
Work A.Pompili (U. of Bari & I.N.F.N.)

8. ! ! Mass Spectra : 8 QCD @ Work 2003 A.Pompili (U. of Bari & I.N.F.N.)
Broad peak due to random combination
where
A 2.32 GeV/c2 is
missing in sidebands dist’ns :
the peak is associated to the
Ds+ p0 system ! ! !
No other signal is evident
up to 2.7 GeV/c2 a part that
associated with
p0 : kinematic fit
E(Ds+): Ds+ mass constraint 8
Work A.Pompili (U. of Bari & I.N.F.N.)

9. Ds+p0 mass spectra and fits [ hep-ex/0304021, 12 April @ PRL]
Mass systematic uncertainty
estimated conservatively to be
< 3 MeV/c2
An estimate of the mass resolution for the system
K+K-p+p0 can be provided directly from the data
by fitting the mass dist’n for
characterized by a width consistent with that of
the observed signal .
A similar mass resolution can be obtained from
the simulation of
Observed width consistent with expt. resolution
Intrinsic width is smaller (G<10MeV/c2)[I-violation] 9
Work A.Pompili (U. of Bari & I.N.F.N.)

10. Angular dist’n consistent with being flat ( 43% probability )
Decay Angular Dist’n
[BKG subtracted]
Efficiency
arb. unit
arb. unit
Angular dist’n consistent with being flat ( 43% probability )
This would be expected for: a spin J=0 state
a higher-spin state produced unpolarized 10
Work A.Pompili (U. of Bari & I.N.F.N.)

11. This possible signal requires additional detailed study
Tests for Reflections
NO signal found using simulation of all known charmed states and decays
NO signal found when exchanging p -K identification hypotheses [no D+,D0,D* seen]
Investigated decays involving known particles and generating a signal through the addition/omission/substitution of a p or a g. Nothing found ! However...
Is this 2.46GeV/c2 a
new narrow state kinematically
feeding-down a signal: ?
Combinations
evts/7MeV/c2
Combinations ?
lost/random
CHECK [MC UNFOLDING] : this feed down …
…1) would have a width G=15MeV/c2 (smeared peak!)
…2) can explain only 1/6 of the observed 2.32 GeV/c2
This possible signal requires
additional detailed study 11
Work A.Pompili (U. of Bari & I.N.F.N.)

12. Confirmation of @ CLEO II & Belle
[ hep-ex/ ]
CIPANP/03 – 20 May]
Ds sidebands
p0 sidebands
Consistent with experimental resolution 12
Work A.Pompili (U. of Bari & I.N.F.N.)

13. NO significant signals seen within current statistics
Jp =? & Other Decay Modes
For a parity conserving decay to Ds+[0-]p0, only natural spin-parity series is allowed: Jp = 0+,1-,2+,…
IF Jp = 0+ (suggested by low mass & compatible with helicity dist’n)…
… it cannot decay into Ds+[0-]g
… whereas… e.-m. decay into Ds*+[1-]g is allowed (by parity & angular momentum conservation)
On the other hand, IF Jp = 1+, it could strongly decay into Ds+p+p- [I-conserving, OZI-suppressed]
IF Jp = 0+, it cannot ( pseudoscalars)!
Studied decay modes into:
NO significant signals seen within current statistics
CLEO B.R. [w.r.t Ds+p0]
Upper Limits
Combinations
MODE
90%C.L .
< 0.054
< 0.078
< 0.020
Combinations
Combinations 13
Work A.Pompili (U. of Bari & I.N.F.N.)

14. “Theorists sent back to their drawing boards” [from: SLAC Press Release]
10 papers in May 1-20 !
2 main classes of interpretations :
a) Within a quark model representation
Cahn & Jackson
hep-ph/
Modified potential model in standard spectroscopy
van Beveren & Rupp
hep-ph/
Quasi-bound in unitarized meson model
Bardeen, Eichten & Hill
hep-ph/
Chiral Perturbation theory + HQET
Godfrey
hep-ph/
Revision needed for masses! Crucial is the B.R. for decay
Colangelo & De Fazio
hep-ph/
Heavy quark spin-flavor sym.+ Vector Meson Dom. Ansatz
b) quark model explanations unlikely: different type of state (tetraquark)
Barnes,Close & Lipkin
hep-ph/
molecular type 4-quark state [DK molecule]
Cheng & Hou
hep-ph/
4-quark state
Szczepaniak
hep-ph/
Dp atom
Bali
hep-ph/
Lattice predictions on masses consistent with quark model 14
Work A.Pompili (U. of Bari & I.N.F.N.)

15. : is it really a new state?
MC studies : including
Kinematical
CROSS-THROUGH
Concern: FEED-UP from : for signal band there is a …
… peaking BKG associated with the crossing band produced by
This can be addressed with different techniques! For istance:
a) MC-based unfolding method: feed-up probability & lineshape distortion [CLEO]
b) Sidebands from data used to estimate peaking BKG [CLEO & BELLE]
will release
results soon 15
Work A.Pompili (U. of Bari & I.N.F.N.)

16. Peaking BKG : 38±8 candidates
… YES! Evidence of a new 2.46 GeV/c2 into
CLEO
CIPANP/03 – 20 May]
BELLE
Ds* signal region
Ds* signal region
Ds* signal region
Ds* sidebands region
Feed-up: 9%
Lower Ds* sideband
Upper Ds* sideband
Raw yield :131±21 candidates
Peaking BKG : 38±8 candidates
Ds*(2463)  Ds* p0
Sideband subtraction
Unfolding method
Number of candidates
40.8 ±11.3
40.7 ± 10.6
M(Ds*p0) - M(Ds*) [MeV]
351.6 ±1.7
350.6 ± 1.2
s [MeV]
5.3 ± 1.2
6.1 ± 1.0
BKG-subtracted yield: 93±22 cand.
Statistical significance ~ 4.2s
Statistical significance ~ 5.3s 16
Work A.Pompili (U. of Bari & I.N.F.N.)

17. A preliminary helicity dist’n shows to be consistent with 1+ state
states in exclusive decays of B mesons [byBELLE]
FPCP/03 – 5 June)
Dominant exclusive process for the two DsJ* production in B decays is :
CLEO B.R.
[w.r.t Ds*+p0]
Upper Limits
MODE
90%C.L .
< 0.49
< 0.16
< 0.08
90fb -1
13fb -1
A preliminary helicity dist’n shows
to be consistent with 1+ state 17
Work A.Pompili (U. of Bari & I.N.F.N.)

18. Summary & Conclusions
Two narrow states have been observed, in the inclusive Dsp0 & Ds*p0
invariant mass distributions, near 2.317GeV/c2 & 2.460GeV/c2.
The widths [G<10MeV/c2] are consistent with experimental resolution.
The smaller intrinsic widths are due to isospin-violation in their decay.
The most likely assignment for their spin-parity is 0+ & 1+.
They do not fit well into the existing potential models for spectroscopy.
The mass splittings m[DsJ*(2317)]-m[Ds(1969)] & m[DsJ*(2460)]-m[Ds*(2112)] are consi-stent with being equal as predicted by Bardeen et al. (BEH) if these are 0+ & 1+ states.
The B.R. Upper Limit for the decay of Ds*(2317) into Ds*g, Dsg and Dsp+p- [w.r.t. Dsp0] and the preliminary B.R. measurement for the decay of Ds*(2460) into Dsg [w.r.t. Ds*p0] are consistent with BEH predictions.
Most results are compatible with models based on HQET and chiral symmetry, which predict
that 0+ & 1+ are the chiral partners of the 0- & 1- states, with same mass splitting.
Interesting times ahead both for experimentalists & theorists. 18
Work A.Pompili (U. of Bari & I.N.F.N.)

19. Few more numbers… ? < 0.054 < 0.078 < 0.020 < 0.49 /
MODE
90%C.L .
< 0.054
< 0.078
< 0.020
BEH
0.08
CLEO
MODE
90%C.L .
< 0.49 /
< 0.16
< 0.08
BEH
0.24
0.22
0.20
BELLE ?
Work A.Pompili (U. of Bari & I.N.F.N.)