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Towards a …?. Brian Meadows University of Cincinnati. Outline. Issues of uniformity Discussions with CLEO and BELLE What methods have been used? A new kind of fit?. Towards Uniformity (with CLEO and BELLE anyway). Discussions were held earlier this year between Alex

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### Towards a …?

University of Cincinnati

Outline
• Issues of uniformity
• Discussions with CLEO and BELLE
• What methods have been used?
• A new kind of fit?

Towards Uniformity(with CLEO and BELLE anyway)
• Discussions were held earlier this year between
• Alex

1975: Open charm discovered (c, FNAL BC 1975 ; D0, D+, SLAC 1976)

1976: De Rujula, Georgi, Glashow – light and heavy degrees of freedom decouple.

1989: Heavy Quark Symmetry

SQ

L

Sq

Heavy-Light Systems areLike the Hydrogen Atom
• When mQ ! 1, sQ is fixed.
• So jq = L­sq is separately conserved
• Total spin J = jq­sQ
• Ground state (L=0) is doublet with jq=1/2
• Orbital excitations (L>0) – two doublets (jq=l+1/2 and jq=l-1/2).
• For decays to ground state (L=1)! (L=0) +  :
• for jq=3/2 state, final hadrons are in orbital D wave

!jq= 3/2 states are narrow.

• for decay of DJ(jq=1/2) state, final hadrons are in orbital S wave

!jq=1/2 states are expected to be broad.

Heavy-Light Systems (2)

2jqLJ

JP

• Narrow statesare easy to find.
• Two wide states are harder.
• Since charm quark is not infinitely heavy, some jq=1/2, 3/2 mixing can occur for the JP=1+ states.

jq = 3/2

2+

small

3P2

large

1+

1P1

L = 1

1+

3P1

small

jq = 1/2

1P0

0+

large

tensor

spin-orbit

jq = 1/2

1-

small

1S1

L = 0

small

0-

1S0

Charmed Meson Spectroscopy
• This picture worked well prior to this year with all narrow L=0 and L=1 states found by 1995.
• The wide, nonstrangejl=1/2 states were found in B decays by CLEO (1999) and BELLE (2002). Subsequently confirmed by BABAR in 2003.
• Most potential model calculations had correctly predicted masses above threshold for  emission for these states, with broad widths. BUT they also
• Generally agreed that strange jl=1/2 states 1Ds0,1Ds1 would be above threshold for K emission.

Charmed Meson Spectroscopy c. 1995

Charmed Meson Spectroscopy pre 2003

D*0K+threshold

D0K+threshold

BABAR may have found

these – but below threshold.

The BaBar Detector at SLAC (PEP2)
• Asymmetric e+e- collisions at (4S).
•  = 0.56 (3.1 GeV e+, 9.0 GeV e-)
• Principal purpose – study CPV in B decays

1.5 T superconducting field.

Instrumented Flux Return (IFR)

Resistive Plate Chambers (RPC’s):

Barrel: 19 layers in 65 cm steel

Endcap: 18 “ “ 60 cm “

Electromagnetic Calorimeter
• CsI (doped with Tl) crystals
• Arranged in 48()£120()
• » 2.5% gaps in .
• Forward endcap with 8 more  rings (820 crystals).

BABAR

0

144 quartz bars

Particle ID - DIRC
• Measures Cherenkov angle in 144 quartz bars arranged as a “barrel”.
• Photons transported by internal reflection
• Along the bars themselves.
• Detected at end by ~ 10,000 PMT’s

Detector of

Internally

Reflected

Cherenkov light

PMT’s

Drift Chamber

40 layer small cell design

7104 cells

He-Isobutane for low multiple scattering

dE/dx

Resolution

»7.5%

Mean position

Resolution

125 m

Silicon Vertex Tracker (SVT)
• 5 Layers double sided AC-coupled Silicon
• Low mass design
• Stand alone tracking for slow particles
• Point resolution z» 20 m

Run 3

Run 4

Run 2

Run 1

Off Peak

PEP-II performances

Peak Luminosity ~ 6 £ 1033 cm-2/ s-1

24 fb-1 in run 1

70 fb-1 in run2

36 fb-1 so far in run3

10 fb-1 so far in run4

This analysis uses runs 1 and 2

» 110 M cc pairs

9% off peak

Currently (Nov 2003)

run 4 is in progress

with ~155 fb-1

On

Off

Charm at the BABARB Factory?
• Cross section is large Can use “off peak” data
• Also
• Relatively small combinatorial backgrounds in e+e- interactions.
• Good particle ID.
• Detection of all possible final states including neutrals.
• Good tracking and vertexing
• Very high statistics.

Charm at the BABARB Factory?
• Present sample of 91 fb-1 sample contains
• Compare with other charm experiments:
• E791 - 35,400 1
• FOCUS - 120,000 2
• CDF - 56,320
• Approximately 1.12 £ 106 untagged

D0!K-+ events

1. E791 Collaboration, Phys.Rev.Lett. 83 (1999) 32.

2. Focus Collaboration, Phys.Lett. B485 (2000) 62.

Data Selection
• All pairs of ’s, each  having energy > 100 MeV, are fitted to a 0 with mass constraint.
• Each 0 is fitted twice:
• To the production vertex to investigate the Ds+0 mass.
• To the K+K-+ vertex so that we can also use the Ds! K+K-+0 mode.

D’s from B decays were removed:

- each event was required to have pD* > 2.5 GeV/c

BABAR results from B decays are forthcoming however.

K+K-+ Mass Spectrum

Approx. 131,000 Ds+ events above large background.

4

3

2

1

0

X 103

X 103

60

40

20

0

D0! K+K-

Events / 3 MeV/c2

1.75 1.85 1.95

m(K-K+) GeV/c2

1.8 1.9 2.0

m(K-K++) GeV/c2

Small bump at 2010 MeV/c2 from

The Ds+ Dalitz Plot
• Data sample: D*s(2112)+!Ds+:
• NOTE
• K* and  bands do not cross (no double counting).
• cos2 distributions evident in vector bands.

Selection essentially keeps events in the 4 peaks.

Total K+K-+ Mass Spectrum
• Sum of + and K¤0K+ contributions is » 80,000 Ds+ above background.
• We define

signal region:

1954 < m(K+K-+) < 1980 MeV/c2

and two sideband regions:

1912 < m(K+K-+) < 1934 MeV/c2

1998 < m(K+K-+) < 2020 MeV/c2

The Ds(2317)see PRL 90, 242001 (2003)
• When Antimo Palano studied the Ds0 system he found a huge, unexpected peak.

There is no signal from Ds+ sidebands.

The Ds*!Ds+0 signal is clear too.

How did CLEO miss it?!

All these events.

The Ds(2317)
• The signal is clearly associated with both Ds+ and 0.

There is no signal from 0 sidebands either.

[NOTE – smearing the 0 signal smears the Ds*! Ds+0 signal too.]

A Real Particle?
• Is the signal due to reflection of a known resonance?

Approximately 80 £ 106e+e-!cc reactions simulated.

All that was known about charm spectroscopy was included.

Conclude signal is not a reflection.

CMS Momentum (p*) Dependence
• Signal seen in all p* ranges.
• Background less significant at higher p* values
• Yield maximum at ~3.9 GeV/c
• Excitation curve appears to be compatible with charm fragmentation process.

250

200

150

100

50

0

200

150

100

50

0

K*

Events / 5 MeV/c2

2.1 2.3 2.5

2.1 2.3 2.5

m(Ds+0)GeV/c2

Multiple Ds+ Modes
• Separate + and K¤0K+ subsamples:
• Ds*+(2112) and signal at 2.317 GeV/c2 present in both channels with roughly equal strength.

p* > 3.5 GeV/c

400

300

200

100

0

Events / 5 MeV/c2

2.1 2.2 2.3 2.4 2.5

m(Ds+0) GeV/c2

Fit to the Signal

Require p* > 3.5 GeV/c

Fit to polynomial and a single Gaussian.

N = 1267 § 53 Events

m = 2316.8 § 0.4 GeV/c2 = 8.6 § 0.4 MeV/c2

(errors statistical only).

 is compatible with detector resolution.

m requires small correction due to Ds(2458) overlap.

Cross Check - a Different Topology

Select Ds+! K-K++0

N = 273 § 33 events

m = 2317.6 § 1.3 MeV/c2

 = 8.8 § 1.1 MeV/c2

(consistent with detector resolution).

Results agree with those from other Ds+ modes

Conclusions on the state so far
• Real and it decays to Ds+0: Implies natural parity.
• Narrow - consistent with BaBar resolution : < 10MeV/c2.
• If a normal Ds+ then this decay violates I spin conservation.
• This could explain the narrowness.
• Being below D0K+ threshold may force such a decay.
• Could be the missing 0+ BUT if so, its mass is lower by » 170 MeV/c2 than expected by potential models.

We label it “DsJ*(2317)+”

• What else …

DsJ+(2317) Decay Angular Distribution
• Helicity angle distribution could provide spin information.
• The corrected distribution in cos  is consistent with being flat (43% probability).
• This could mean that J=0 or just that state is unaligned.

Acceptance

Uncorrected

Corrected

0

DsJ(2317)

10 x Efficiency

Ds

cos

cos

cos

Search for Other DsJ+(2317) Decay Modes
• We have studied the mass spectra for
• Ds+0 0
• Ds+
• Ds+ 
• Ds*+(2112)
• Ds+0 
• In all cases, we require that:
• The ’s are not part of any 0 candidate.
• The combination has p* > 3.5 GeV/c.

None of these found

Ds+, Ds+, Ds*(2112)
• No evidence for DsJ(2317) in any of these decays.
• Absence of Ds+ weakly suggests J = 0
• However other two modes would be expected for a JP = 0+.

Ds+0, Ds*(2112)0- Other Possibilities
• No evidence for D*sJ(2317)+ either of these modes
• BUT …
• Is there a second state at ~ 2460 MeV/c2 ?

Events / 7 MeV/c2

Ds*(2112)0

m(Ds+0)

2.4

2.3

2.2

2.1

2.0

m(Ds+)GeV/c2

2.1 2.2 2.3 2.4 2.5

m (Ds+0) GeV/c2

A Second State ?
• The decays

DsJ(2317)+!Ds+0 and Ds*(2112)+!Ds+

overlap kinematically just where m(Ds+0)~2460 MeV/c2.

• Gives us two problems:
• Produces a kinematic peak at 2460 MeV/c2 – signal?
• Resolution smearing makes it difficult to distinguish decays of a 2460 MeV/c2 state to Ds*(2112)+0 or D*sJ(2317)+ ?

m(Ds+0)=

2.46 GeV/c2

A Second State ?
• Another concern we resolved: Is the D*sJ(2317) signal just a reflection of the higher mass state?!
• NO – such reflection is
• Too wide
• Wrong mass
• Too small by factor ~ 5.

A Second State ?

… from our PRL 90 (2003) 242001.

• “Although we rule out the decay of a state of mass 2.46 GeV/c2 as the sole source of the Ds+0 mass peak corresponding to the D*sJ(2317)+, such a state may be produced in addition to the D*sJ(2317)+. However, the complexity of the overlapping kinematics of the Ds*(2112)+!Ds+ and D*sJ(2317)+!Ds+0 decays requires more detailed study, currently underway, in order to arrive at a definitive conclusion.”

Meanwhile …

CLEO Sees D*sJ(2317) Too

m(Ds0) – m(Ds)

350.0 § 1.2 (stat) § 1.0 (syst) (MeV/c2)

Not in Ds+-

• From 13.5 fb-1 CLEO II
• Signal seen in Ds0
• Not seen in Ds+-,
• Ds, Ds1(2112)

Signal has events (» same yield / fb-1 as BABAR).

PRD 68, 032002 (2003)

So Does Belle (in continuum)
• 78 fb-1 sample
• Ds!, p* > 3.5 GeV/c
• M = 2317 § 0.5 MeV/c2
• = 8.1 § 0.5 MeV/c2
• N = 770 § 43 events
• They also observe it in
• B!D DsJ decays.

Y. Mikami, et al, hep-ex/0307052v2 (2003)

The DsJ (2458)+
• CLEO results are published with title:

“Observation of a Narrow Resonance of Mass 2.46-GeV/c2 Decaying to Ds*(2112)+0 and Confirmation of the D*sJ(2317)+ State.”

in PRD 68, 032002 (2003)

• BELLE has also observed the DsJ (2458)+
• In continuum – hep-ex/0307052
• In B!DDsJ decay – hep-ex/0308019
• What BABAR says about the second state now …

2.4

2.3

2.2

2.1

2.0

m(Ds+)GeV/c2

2.1 2.2 2.3 2.4 2.5

m (Ds+0) GeV/c2

Recap - theProblem
• The decays

DsJ(2317)+!Ds+0 and Ds*(2112)+!Ds+

overlap just where m(Ds+0)~2460 MeV/c2.

• This gives us two problems:
• Produces a kinematic peak at 2460 MeV/c2
• Resolution smearing makes it difficult to distinguish decays of a 2460 MeV/c2 state to Ds*(2112)+0 or DsJ(2317)+

m(Ds+0)=

2.46 GeV/c2

BABAR - There is a Signal!

Data

MC

A strong peak appears in BABAR data that is absent in generic MC

[e+e-!cc that includes D*sJ(2317)+ production].

Attribute the excess to a new signal at 2458 MeV/c2.

DsJ(2458)+

m() ´ m(KK0) - m(KK0)

m(0) ´ m(KK0) - m(KK)

NOTE – Change of variables

Next: a) extract signal strength and properties; b) distinguish Ds*(2112)+0 from DsJ(2317)+

100

80

60

40

20

0

0.3

0.2

0.1

80

60

40

20

0

Events / 7 MeV/c2

m() GeV/c2

0.25 0.50

m(0) GeV/c2

0.25 0.50

m(0) GeV/c2

0.25 0.50

m(0) GeV/c2

Extraction of Signal from Background

Seems most obvious method - make a (peaking) sideband subtraction and fit to Gaussian: ! m = 344.6 § 1.2 MeV/c2.

BUT:

• Assumes background is linear.
• Not true as resolution of m(0) changes with m().
• Width of signal depends on width of sideband selected.
• Ignores D*sJ(2317)+ decay possibility.

Monte Carlo for

DsJ(2458)+!Ds*(2112)0

Monte Carlo for

DsJ(2458)+!DsJ(2317)

Decay Mode
• Distinction between Ds*(2112)0 and DsJ (2317)+ decays is possible from different line shapes each produces.
• Data clearly prefer the shape for DsJ (2458)+! Ds*(2112)0

Channel Likelihood1 Method
• Determine fractions xi of processes producing events and best mass (m) and Gaussian width () for DsJ (2458).
• Each Ds+0 combination is assigned a likelihood:

L = x1P1 + x2P2 + … + (1 - x1 - x2 - …)

where Pi are normalized Probability Density Functions.

Processes included were:

P1: DsJ(2458) !Ds*0

P2: DsJ(2458) !DsJ(2317)

P3: Ds+0!Ds* + random 

P4: Ds+0!DsJ(2317) + random 0

P5: Ds+0! combinatorial background

Assumption: that DsJ(2458) decay is all quasi two body with no interference (reasonable since the states are all narrow).

1 P.E. Condon and P.L. Powell, PRD 9, 2558 (1974)

Fit Results
• Important results from the fit are:
• The DsJ(2458)+ width is consistent with detector resolution indicating that the state is narrow.
• We infer that:

Fit Results (2)
• The fit assigns a probability xiPi to each event to belong to a process, so weighted plots take account of all reflections.

Unweighted

Ds+0

Weighted

Data

Weighted

DsJ(2458)+!Ds*+0

Fit

Weighted

DsJ(2458)+!DsJ(2317)+

Correction to DsJ (2317)+ Mass
• Distortion of the DsJ(2317)+ signal due to background from DsJ(2458)+!Ds*(2112)+0decays can be estimated from a Monte Carlo study.
• Re fitting to include this, DsJ(2317)+ parameters are:

m = 2317.3 § 0.4 MeV/c2 ;  = 7.3 § 0.2 MeV/c2.

Spin-Parity of DsJ(2458)+
• The decay observed here violates I-spin. The width is small.
• So natural parity (0+, 1-, 2+, …) appear to be ruled out as this state could decay to D0K+, conserving I-spin.
• It is below D*K threshold, a decay accessible to unnatural parity, so its width is compatible with JP=0-, 1+, 2-, …
• The helicity distribution is also consistent with this hypothesis.

Spin-Parity of DsJ (2458)+
• Helicity angle of :
• JP = 0- agrees worst. 1- and 2+ cannot be ruled out.
• Unnatural parity distributions depend on alignment of DsJ(2458)+.

Ds*(2112)

h

0

Ds

No conclusive information on spin here

Belle 86.9 fb-1

CLEO “Ds(2463)” 13.5 fb-1

D*(2112)

D*(2112)

sidebands

N = 41§ 12 events (>5)

m = 349.8 § 1.3 MeV/c2

N = 126§ 25 events

m = 345.4 § 1.3 MeV/c2

CLEO and Belle See Ds(2458) in Continuum

PRD 68, 032002 (2003)

hep-ex/0307052

More Observations by Belle
• See both states in B decay
• See DsJ(2458)+!Ds+

Continuum

B!D DsJ

DsJ(2317)+

!Ds+0

DsJ(2458)+

!Ds*(2112)+0

DsJ(2458)+ !Ds+

Rules out J = 0

Belle observes DsJ(2458)+!Ds+
• Helicity angle from Ds+ decay in:
• NOTE – DsJ(2458)+ is aligned with helicity 0.
• J=1 appears to be better description than J=2.

J = 2

J = 1

! JP = 1+ strongly suggested by all evidence so far.

Decays to Di-pions

Belle – 86.9 fb-1

See DsJ (2458) !Ds+-

Modes conserve I-spin

But are OZI suppressed

Preliminary

CDF Run 2

~ 80 pb-1

CLEO II

~13.5 fb-1

CLEO 13.5 fb-1

m(Ds++-)

Comparison of Results
• BABAR measures, for p* > 3.5 GeV/c2, the ratio
• This, and masses for the two DsJ states, are in good agreement with Belle. Values for CLEO’s DsJ (2458)+ mass and R are slightly higher.

Experimental Summary - DsJ*(2317)+
• A large, narrow state at 2.32 GeV/c2 with width  < 10 MeV/c2 was discovered by BABAR.
• The mass is about 40 MeV/c2 below the DK threshold.

m = 2317.4 § 0.5 (stat.) § 0.6 (syst.) MeV/c2 (my average)

• So far, this is only seen in the Ds0 decay mode. It is not seen in Ds , Ds, Ds, Ds*(2112), Ds or Ds0
• The decay to Ds0 implies natural parity (0+, 1-, 2+, etc.)
• J P=0+ suggested by absence of Ds+  or Ds decays.
• If this is so, decay to Ds*(2112)  is allowed, but not yet seen.
• The state is confirmed by both CLEO and BELLE.

Experimental Summary - DsJ (2458)+
• BABAR first showed evidence for a narrow structure in the Ds*(2112)0 system near 2460 MeV/c2, however they deferred claiming it as a well defined state.
• CLEO observes DsJ (2463) ! Ds* (2112)0 state, confirmed by BELLE in continuum and B decay.
• Belle also observe decay to Ds and Ds+-.
• The mass is about 40 MeV/c2 below the D*K but above D0K+ threshold.

m = 2458.6 § 0.8 (stat.) § 0.7 (syst.) (my average)

• J P=1+ suggested by absence of a signal in D0 K+, and in helicity distribution from B decay sample. Higher spins are not excluded.

Charmed Meson Spectroscopy Now

John Bartelt, Sept, 2003

If these States are cs Mesons.
• Decays observed violate isospin conservation
• Not a problem. D*s(2112) also decays to Ds0 about 5% of the time. Rate predicted by Cho and Wise assuming 0- mixing is the mechanism.
• But can we learn anything from relative rates for 0 vs. ?
• A class of potential models is incapable of predicting their masses to be so low.
• Earlier predictions good to ~10 MeV/c2 . New states ~160-180 MeV/c2 low.

R. Cahn and J.D. Jackson, hep-ph/0305012, P. Colangelo and F. De Fazio, hep-ph/0305140, S. Godfrey, hep-ph/0305012.

• Apparently relativistic corrections do not help either.

W. Lucha and F. F. Schoberl, hep-ph/0309341

• Possibly, if effects are due to mixing of the jq=1/2 and 3/2 states, then B spectroscopy will reveal this?

If these States are cs Mesons.
• Quenched lattice gauge calculations also predict higher masses for a scalar cs system.

G. Bali, hep-ph/0305209

… though calculations in the continuum limit seem to be able to accommodate the masses observed and the pattern of splittings in the radial excitations.

A. Dougall, et al., hep-lat/0307001

• However, chiral symmetry models predict the observed splittings

m1+ – m0+ = m1- – m0- ¼ 141.2 § 1.2

W. A. Bardeen, E. J. Eichten, C. T. Hill, hep-ph/0305049

What Else Can they Be?
• Meson-meson molecules (conjectured by N. Isgur and H. Lipkin), or 4q states
• If so we still need to find the cs states.
• Expect to find other states with mixed I spin.
• Should see narrow Ds+§ decay modes.

T. Barnes, F. E. Close, H. J. Lipkin, hep-ph/0305025, Cheng and Hou, hep-ph/0305038, S. Szczepaniac, hep-ph/0305060, K. Terasaki, hep-ph/0305213.

• Mixed 4 quark and cs systems
• These states are the predominantly cs part
• Need to find mainly 4q component - at higher mass (~2.6 GeV/c2) and broad.

T. E. Browder, S. Pakvasa, A. Petrov, hep-ph/0307054 v4

• Poles in unitarized DK scattering

E. Van Beveran, G. Rupp, hep-ph/0305035, hep-ph/0306155

Summary
• Discovery by BABAR of the D*sJ(2317)+ has opened up a new window in QCD.
• This could have far reaching consequences for studies of spectroscopy in all sectors.
• Much theoretical speculation (at least 40 papers so far)
• Much experimental work to do to look for radiative decays and more new states , perhaps exotics.

Yet Another New Narrow State!

BELLE’s “X”

CDF Confirms “X”

BELLE : m = 3872.0 § 0.6 § 0.5 MeV/c2

CDF : m = 3871.4 § 0.7 (stat.) MeV/c2

 compatible with resolution.

Yet Another New Narrow State!

CLAS

hep-ex/0307018

DIANA

hep-ex/0304040

Spring-8

hep-ex/0301020

PRL 91: 012002 (2003)

d!K+K-pn

K+Xe!K0pXe'

 n!K+K-n

MM(K+)

CLAS : m = 1542 § 5 MeV/c2;

DIANA : m = 1539 § 2 MeV/c2

Spring-8 : m = 1.54 § .01 GeV/c2

¼ resolution

and …
• (1405) – has charm counterpart c(2593)
• a0(980), f0(980)
• , , …

Pure Speculation ?
• Could there be a relationship between
• Meson-meson (DD*) molecules ?

and

?

Back up Slides

Peaking Background

CLEO background – judged from the Ds*(2112)+ sidebands - has only a small peak.

CLEO

Belle

BABAR

Peak

• Peak is below DsJ(2458)+ signal
• For BaBar and Belle it is aboveDsJ(2458)+.

Other Results from BELLE:

Particle ID - DIRC

It Works Beautifully!

10

8

6

4

2

0

BABAR

K/ separation ()

Provides excellent K/ separation

over the whole kinematic range

• 2.5 3 3.5 4
• Momentum (GeV/c)

Particle ID - DIRC

D0

D0

An Example: Ds Production spectrum
• Below 2.4 GeV/c Ds can come from B decay
• Can use off peak data there to reduce combinatorial background

Off peak (normalized for p*>2.4 GeV/c)

On peak

Selection of Ds+!+ and K¤0K+
• Select  mass band: |m(K+K-) – 1.019| · 0.01 GeV/c2;
• Select K¤0 mass band: |m(+K-) – 0.896| · 0.05 GeV/c2;
• Require |cos| > 0.5 to enhance proper helicities of each vector.
• Each resulting sample has about same size.

Summary
• New charmed, strange, narrow resonance at 2.32 GeV/c.
• Poses possible problems for the quark potential model.
• May be a four quark or DK bound state.
• Much speculation is being generated:

R. Cahn, J.D. Jackson, hep-ph/0305012

T. Barnes, F. E. Close, H. J. Lipkin, hep-ph/0305025

E. Van Beveran, G. Rupp, hep-ph/0305035

H-Y Cheng, W-S Hou, hep-ph/0305038

W. A. Bardeen, E. J. Eichten, C. T. Hill, hep-ph 0305049

P. Szczepaniak, hep-ph/0305060

S. Godfrey, hep-ph/0305122

P. Colangelo, F. De Fazio, hep-ph/0305140

cs

DK

DK

csnn

cs (chiral L)

Dpi

?

?

Decays to di-Pions

Modes conserve I-spin

But are OZI suppressed

No obvious signals (yet)

BABAR

~81 fb-1

CDF Run II

Preliminary ~80 pb-1

m(Ds+00)

CLEO II

~13.5 fb-1

m(Ds++-)

m(Ds++-) – m(Ds+)

DK Molecule?

T. Barnes, F.E. Close, H.J. Lipkin, hep-ph/0305025

• I=0 csnn or a DK bound state?
• If DK bound state, then some I=0 component to explain narrow width.

A qqcs Four Quark State?

From H. Cheng and W. Hou, hep-ph/0305038.

Quasi Bound cs State?

E. van Beveren, G. Rupp, hep-ph/0305035

• Charmed cousin of a0(980), f0(980), (600), (800) nonet.
• Predicts D0(2030) – broad because above DK threshold
• Also predicts D0(2640), D0(2790) to go with K0(1430), etc.

Introduction

The spectrum of Ds (cs) states has gaps.

• The scalar state predicted could decay to DK so it would be broad (» 270-990 MeV/c2).

Observed

Predicted

Ds2

Ds1

D*K

Mass GeV

D0K

D*s

DsJ(2317)

Ds

New State

JP

This would make it difficult to observe …BUT

If it were below DK threshold, it could be narrow.

Data Selection
• In this study we look for resonances decaying to: Ds0
• Ds+ mesons are selected with +,K¤0K+ and K+K-+0 decay modes, so we select events in final state:

K+K-+ (+ charged conjugate)

• To do this we:
• Select all combinations of three charged tracks with total charge § 1, an identified K+K- pair and a third track which is not a K§.
• Require Ds+ candidate fit well to a common vertex.
• Fit the Ds+ composite momentum to a primary vertex

Resolution Improvement

a) Constrain Ds mass

b) Remove duplicated ’s

Experimental Resolution
• Fit Ds*+(2112) width in Monte Carlo and Data:

Data:  = 6.6 § 0.1 MeV/c2

MC:  = 5.7 § 0.1 MeV/c2

• So MC is too optimistic by factor 1.16.
• Generate Monte Carlo events for DsJ+(2317) with  = 0:

 = 7.7 § 0.2 MeV/c2

• Scale by factor 1.16 ! expect  = 8.9 MeV/c2.
• ForDsJ+(2317)with p* > 3.0 GeV/c we find:

 =9.0§0.4MeV/c2

So width is consistent with mass resolution.

Another Topology Ds+!K+K-+0

Rational:

• Mode has same topology as Ds+0 when Ds+!K+K-+.
• Width of Ds+!K+K-+0 gives further, direct information on the Ds+0 mass resolution.
• Can provide corroborative evidence for Ds+0(2317) signal.

Strategy:

• Use other vertex fit.
• Select cleaner sample using K*0, K*§, +,  resonant sub channel selections.

Data from Ds+!K+K-+0

X 103

Use other vertex for 0

Require at least one vector meson in two body subsystem.

No  from a 0 candidate can be part of any other 0.

Require p* > 3.5 GeV/c.

Require laboratory momentum of each  be > 300 MeV/c.

25

20

15

10

5

0

Ds+

D+

1.75 2.0

m(K+K-+0) GeV/c2

Over 1500 events in the signal.

The resonance has width comparable with the mass resolution in these systems.

It is evident in two different topologies

a)D§s!K§ K¨ § (two modes)

b) D§s!K§ K¨ §0

Masses consistent in all channels – width » resolution.

New Narrow Resonance “DsJ(2317)”

“Ds(2317)”

Ds1(2112)

p* > 3.5 GeV/c

p* > 3.5 GeV/c

Ds1(2112)

Test Using Monte Carlo Simulation
• We simulate the reaction

e+e-!cc

using GEANT4.

• Events generated contain all that is presently known about charm spectroscopy.
• Approximately 80 x 106 events are processed exactly the same way as the data.

Test Using Monte Carlo Simulation
• Sum of + and K¤0K+ and Ds+0 mass spectra.
• We observe the known decay: Ds¤+(2112)!Ds+0.
• The Ds+0 mass spectrum shows no sign of 2.32 GeV/c2 signal. We would expect » 1,400 events.

We conclude that the 2.32 GeV/c2 structure is not due to reflections from known charm states.

2.32 GeV/c2

Is 2.32 GeV/c2 Structure due to Ds¤+(2112)?
• We use the ’s from the 0 candidate to compute the two masses Ds+1,2.
• The 2.32 GeV/c2 signal survives when events with a Ds+1,2 mass in the Ds¤+(2112) are removed.

Ds¤+(2112)

removed

Ds¤+(2112)

selected

We conclude that the signal at 2.32 GeV/c2 is not a Ds¤+ reflection

Mass and Width

Ds+! K-K++0:

M = 2317.6 § 1.3 MeV/c2

 = 8.8 § 1.1 MeV/c2

Ds+! K*0K+, +:

M = 2316.8 § 0.4 MeV/c2

 = 8.6 § 0.4 MeV/c2