Charmed Meson Spectroscopy

Charmed Meson Spectroscopy

Robert K. KutschkeFermilab

HQL04 June 4, 2004

R. K. Kutschke Heavy Quarks and Leptons. 2004 2

Heavy-Light Mesons: Coupling Angular Mommenta

Sq

jSLSSJ QqQ )(

Heavy Quark Symmetry (HQS):

jl = total angular momentum of the light degrees of freedom.

QQ m

1

Spin of Q can be treated as a small perturbation.

Main features understood by treating jl as a good Q#!

q=u,d,s

SQ

L

0,1,1,2PJFor L=1:


P-Wave Charmed Mesons

• For each of cd, cu, cs, expect two doublets:

Narrow doublet:

•JP = ( 2+, 1+)

• jlight = 3/2

• D(*)decay: D wave.

• O( 10 MeV )

• All well established.

Broad doublet:

•JP = ( 1+, 0+)

• jlight = ½

• D(*)decay: S wave.

• O( 100 MeV )

• First observations recently.


Cartoon of Dominant Decay Modes

Q

Q

q

q

q

q

ssdduu ,,

*** ,DDD

SS DKDDKD ,, *** When permitted by conservation of Energy, J and P.


What’s Overly Simplified in the Ideal Picture?

• Doublets may overlap ( which 1+ is more massive?)

• Are all states above D and DK thresholds?

•Is suppression of S wave widths complete?

• Ds1 right at threshold for D*:

• Very narrow, < 2.3 MeV/c2 @ 90% CL.

• Data suggests mostly S-wave!


Where Were We at HQL02?

• All data consistent with simple picture of HQS.

• Narrow doublet well established: D0, D+, DS.

• Broad states not observed ( except for an unpublished CLEO result ).

• Delphi D’ still not confirmed by anyone.

What’s New Since HQ&L 2002?

• Observation of the expected broad DJ states.

• Observation of two new narrow DSJ states which decay to DS and DS

*.

– Are these the expected broad states ?


FOCUS’ Starting Point: D and D* Signals

K-K-

K-D*+ D0+


FOCUS Phys. Lett. B586, 11-20 (2004)

M(D0+)

Feeddown: ),( 000* DDDJ

Neutrals are unobserved

BG Function:DBmA Cme )()(

A,B,C,D Free parameters

Horrible Fit!

FOCUS


Same problem for M(D+-): Horrible Fit

M(D+-)

FOCUS explored many BG models but all failed.

Idea: We expect a broad state so add one to the fit.

Caveat: 2 broad states DD 0*

0

),( 0*01 DDD

FOCUS


FOCUS

• Add a single S-wave resonance to the fit.

• Get excellent fit quality.

• Fit is robust against many variations in background.

• Yield of broad resonance:– 18754 2200– 8.5 stnd. dev.

• Relative yields of signals and feed-downs consistent with expectations.


• Add a single S-wave resonance to the fit.

• Get excellent fit quality.

• Fit is robust against many variations in background.

• Yield of broad resonance:– 9810 2700– 3.6 stnd. dev.

• Relative yields of signals and feed-downs consistent with expectations.

FOCUS


Changing of the Guard

• To date all published measurements of D** come from inclusive measurements.

• A more powerful way of doing charm spectroscopy is to look at the Dalitz plots in BD(*) Dalitz decays.– The penalty is small product branching ratios.– We have been waiting a long time for this.– Remember the power of D Dalitz plots for light

quark spectroscopy.• CLEO CONF-99-6, unpublished, uses this technique

but with partial reconstruction of the final state.• Last year Belle submitted the first use of this

technique with full reconstruction.


Belle: hep-ex/0307021 To Appear in PRD.

DB *DB

Good signal to background ratio. Delta E cut kills Feed-down.

KD 0* DD KD0

KD0

http://arxiv.org/abs/hep-ex/0307021


Belle BD+ Dalitz Plot

Signal Region E Sideband


• Resonances Included:– Free M and :

• D2*(2460)

• D0*

– Virtual States:• B*• D*0D+

• All have significant fit fractions.

• Most new features established by interference effects.

• No constant term in final fit. It does not improve the likelihood.

Belle


Belle

Belle

Signal Region E Sideband

Belle BD*+ Dalitz Plot


• Resonances included:

– D2*(2460)

– Free M and

• D1(2420)

• D1(broad)

– Virtual States:• B*• D*

• All have significant fit fractions.

• Most new features established by interference effects.

• No constant term in final fit. It does not improve the likelihood.

Belle


Summary of D2* Data


Summary of Data for D1(2420)0


FOCUS measurements are of an unknown superposition of D1

*0 and D1

0. So it does not make sense to take an average of BELLE and FOCUS.


Summary of Charm Non-Strange Spectroscopy

• Broad states have now been seen.• Above threshold for decay to D(*)• Masses and widths approximately

as expected.• Angular distributions in the B Dalitz

plots supports the conventional spin parity assignments:

– D1(2427): 1+

– D0*(2308): 0+

• Mass ordering of the two 1+ states is not yet resolved.

• More statistics will help, especially the broad states.


A Surprise from BaBar: PRL 90, 242001 (2003)

BABAR91 fb-1

+

• Narrow peak in DS.

– JP = natural• Width consistent with

detector resolution, about 9 MeV.

• Mass near 2317 MeV.– About 40 MeV below

DK threshold.• Second state near 2456?M(DS)

• Could this be the DS*0?

• Mass is below most, but not all predictions, – Nowak, Rho and Zahed, PRD 49, 4370 (1993).– Bardeen and Hill, PRD 49, 409 (1994).


Where to Look if DK and D*K are Forbidden

c

c

s

s

s

s

0(*)SD

mixing

0

c c

s s

(*)

SD

c c

s s

(*)SD

Isospin violating! Cho and Wise, PRD 49, 6228

(1994)


CLEO Sees Two States

Ds* signal region

Ds* sideband region

55±10 events

• Confirms BaBar state at 2317 MeV.

• Establishes new state near 2460 MeV.


Belle Confirms Both States

M(Ds+

π0 )-M(Ds+) M(Ds

*+ π0 )-M(Ds

*+)

Ds sidebands*

Sidebands: DS solid, 0 dashed.


A Conspiracy !• Feed-down:

– DS(2460) DS* (DS

*)

– Miss gamma and reconstruct as: DS

– Makes a narrow peak near 2317 MeV.• Feed-up:

– DS(2320) DS.– Add a random photon and require that

DScombination fall in DS* mass region. Plot

mass of DScombinations.– Makes a narrow peak near 2460 MeV.

• Most signal are about 75% pure and 25% feed up/down.

• CLEO, BaBar, Belle: different methods to deconvolve.


Example: BaBar’s Method)()( 0

0 SS DmDmm

Points: M(DS) in DS*

region.

Shaded: DS* sideband

Subtract distributions on the right.


Belle: Two New Decay Modes of DS(2460)

Forbids J=0

DS1(2536) !DS(2460)

Histogram: DS sidebands.

DS(2320) DS*(2112)


Belle: Sees the Decays BDDsJ

Histograms: E sidebands

Ds(2317)oDs

Ds(2460)oDs*

Ds(2460)Ds

2+

1+

DSJ Frame

DS

DS in B Frame

sJD


Focus Sees DS(2317) in Photoproduction

• Histograms: DS and 0 sidebands.

• First observation outside of e+e- at 10 GeV.

• M = 2323 2 MeV ( stat only; uses PDG DS mass).

– About 2 sigma above average of other experiments.• Width consistent with detector resolution.

• Energy calibration: DS* DS0 and D0 K-0.


Some Suggestions?

• HQS plus chiral symmetry explain low masses below DK threshold.– Bardeen, Eichten & Hill hep-ph/0305049. – Nowak, Rho & Zahed hep-ph/0307102.

• DK molecule– Barnes, Close & Lipkin hep-ph/0305025

• Mixture with 4-quark state above DK threshold – Browder et al. hep-ph/0307054

• Unitarized meson model – Van Beveran & Rupp hep-ph/0305049

• Masses using QCD Sum Rules– Dai, Huang & Zhu hep-ph/0306274


Some Suggestions?

• Can the lattice explain these as csbar states?– No: Bali hep-ph/0305049,– Yes: Dougall et al hep-ph/0307001

• On the importance of radiative decays:– Colangelo & De Fazio hep-ph/0305140– Godfrey hep-ph/0305122

• Branching Fractions in B decay DDSJ are much smaller than for DDS. Factorization suggests that they should be similar. Is this a sign of non c-sbar nature?– Chen and Li hep-ph/0307075 – Datta and O’donnel hep-ph/0307106 – Cheng and Hou hep-ph/0305038


Miscellany

• No signals seen in DS ( CLEO and CDF ).

– Excludes some molecule interpretations.


Summary of New DS States

M=2317.6 0.8 MeV M=2459.2 1.1 MeV < 4.6 MeV (90% CL) < 5.5 MeV (90% CL)

JP=0+ Favored JP=1+ Favored


An Important Measurement to Do

• Set the scale of the partial widths. This will help sort out competing models.– Hard to impossible with and 0 final states.

• An idea:

– Measure the width of the DS1(2536).

– Better measurements of DS1(2536) DS.

– Measure: DS1(2536) DS(*)

– This can calibrate the models which can then be applied to the 0+ and 1+ states.


What’s Interesting to do Next

• Increase statistics on BD(*)Dalitz plot analyses.– Improve measurements of the broad states and

find charged broad 1+ state.– Look for new states.

• Discover DS2 D*K.

• Dalitz plot analyses of B decays with DSJ in final state.– This will be hard and require lots of data but

Belle has shown that it is not out of the question.• CDF, D0, LHC-b and BTeV.

– Combinatoric BG kills inclusive measurements.– Should do well with analysis of B Dalitz plots.


Summary and Conclusions

• The charmed-non-strange P-wave broad states are established with their expected properties.– Waiting for BaBar’s results.– Can CDF and D0 compete here?.

• The charmed-strange “broad” states are really strange. They are narrow!– Below threshold for decay to D*K so they

appear in unexpected decay modes, DS*0,

DS and DS.

– Their JP are constrained but not fully determined.

• Lots still to do. Especially important to establish the widths of the narrow states.


Observation of the Ds2* at Focus

Prelim

inar

y

FOCUS

First observation of the D+KS

0 mode!

D0K+ D+KS0

There are some real KS0 in

the sideband sample.


Simultaneous Fits to D0K+ and D+KS0

Spectra

1. DS2 Signal: D-wave Rel. BW

2. Smooth background shape

3. MC DS1 feeddown shape

4. MC DS2 feeddown shape. Significance is not stable with cut variations!

Terms in the fit:

• Simultaneous: M and same.• Errors are statistical only PDG:

M = 2573.5 ± 1.7 MeV/c2

= ± 5 MeV/c2

Prelim

inar

y

First observation of D+KS0

mode


Observation of the DS1 at FOCUS

Prelim

inar

y

1. DS1 Signal: Non Rel BW, convoluted with a gaussian.

2. Smooth background shape.

3. DS2* Signal: D-wave Rel

BW.

Terms in the fit:

• Errors are statistical only

PDG:

= 525.35 ± 0.34 MeV/c2

< 2.3 MeV/c2 @ 90 % CL.

M(D*+Ks0)-

M(D*+)

Documents

Charmed Meson Spectroscopy