Observation of two narrow states ....

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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
QCD_at_Work 2003 Conversano - 15 June 03
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Outline
spectroscopy before new states observation
Charm physics _at_ 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
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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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, 114004 (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, DK threshold, decaying to
Dsp0, Dsp0 !
P-wave
S-wave
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Charm Physics _at_ B-factories
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
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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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)
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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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
gg couples (origin in track vertex) with
kinematic fit constraint m(p0)
(or tighter)
gg couples (origin in production vertex) with
kinematic fit constraint m(p0)
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Further background rejection
Select quasi-two body decay modes
2 disjoint sub-samples
Helicity angles cut 2-body decays of

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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Mass Spectra
Broad peak due to random combination
where
A signal _at_ 2.32 GeV/c2 is missing in sidebands
distns 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
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Dsp0 mass spectra and fits
hep-ex/0304021, 12 April _at_ PRL
Mass systematic uncertainty estimated
conservatively to be lt 3 MeV/c2
An estimate of the mass resolution for the
system KK-pp0 can be provided directly from the
data by fitting the mass distn 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
(Glt10MeV/c2)I-violation
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Decay Angular Distn
BKG subtracted
Efficiency
arb. unit
arb. unit
Angular distn consistent with being flat ( 43
probability )
This would be expected for a spin J0 state

a higher-spin state produced unpolarized
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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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 peak _at_ 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 G15MeV/c2 (smeared peak!) 2)
can explain only 1/6 of the observed peak _at_ 2.32
GeV/c2
This possible signal requires additional detailed
study
11
QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Confirmation of _at_ CLEO II
Belle
hep-ex/0305017
_at_ CIPANP/03 20 May
Ds sidebands
p0 sidebands
Consistent with experimental resolution
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Jp ? Other Decay Modes
For a parity conserving decay to Ds0-p0, only
natural spin-parity series is allowed Jp
0,1-,2,
IF Jp 0 (suggested by low mass compatible
with helicity distn) it cannot decay into
Ds0-g whereas e.-m. decay into Ds1-g is
allowed (by parity angular momentum
conservation)
On the other hand, IF Jp 1, it could strongly
decay into Dspp- I-conserving,
OZI-suppressed
IF Jp 0, it cannot (0 3pseudoscalars)!
Studied decay modes into
NO significant signals seen within current
statistics
CLEO B.R. w.r.t Dsp0 Upper Limits
Combinations
Combinations
Combinations
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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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
b) quark model explanations unlikely different
type of state (tetraquark)
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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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
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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YES! Evidence of a new state _at_ 2.46 GeV/c2
into
CLEO
BELLE
_at_ CIPANP/03 20 May
Ds signal region
Ds signal region
Ds signal region
Ds sidebands region
Feed-up 9
Upper Ds sideband
Lower Ds sideband
Raw yield 13121 candidates
Peaking BKG 388 candidates
BKG-subtracted yield 9322 cand.
Statistical significance 4.2s
Statistical significance 5.3s
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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states in exclusive decays of B mesons byBELLE
(_at_ FPCP/03 5 June)
Dominant exclusive process for the two DsJ
production in B decays is
CLEO B.R. w.r.t Dsp0 Upper Limits
90fb -1
13fb -1
A preliminary helicity distn shows to be
consistent with 1 state
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Summary Conclusions
Two narrow states have been observed, in the
inclusive Dsp0 Dsp0 invariant mass
distributions, near 2.317GeV/c2 2.460GeV/c2.
The widths Glt10MeV/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 mDsJ(2317)-mDs(1969)
mDsJ(2460)-mDs(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 Dsg, Dsg and Dspp- w.r.t. Dsp0 and the
preliminary B.R. measurement for the decay of
Ds(2460) into Dsg w.r.t. Dsp0 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.
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QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)
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Few more numbers
CLEO
BELLE
?
QCD _at_ Work 2003
A.Pompili
(U. of Bari I.N.F.N.)