Marc Pelizaeus - Meson

9 th International Workshop on 

Meson Production, Properties and Interaction 

Charm and Charmonium 

Spectroscopy 

M. Pelizäus (Ruhr-Universität Bochum) 

for the Babar Collaboration 

June 13, 2006 

Cracow, Poland

The Babar-Experiment 

• Asymmetric energy e + e - storage rings PEP-II 

– ~90% at 10.58 GeV ( ); ~10% at 10.54 GeV 

– more than 350 fb -1 recorded so far 

(~1.6x10 9 hadronic events) 

Solenoid (1.5T) 

Hadron /Muon Detector 

• Good track and 

vertex reconstruction 

• Good particle identification 

• Good photon detection 

(3.1 GeV) 

(9.0 GeV) 

Cherenkov Detector 

Vertex Detector 

Drift Chamber 

Electromagnetic Calorimeter 

M. Pelizäus, Charm and Charmonium Spectroscopy 

2

Production of hidden and open charm states 

• Production in B decays 

– ~380x10 6 B events 

– provides access to 

inclusive measurements 

of absolute branching fractions 

• e + e - →c fragmentation processes 

– ~1x10 9 charmed particles 

– spectroscopy of open charm 

states with high precision 

• Initial state radiation (ISR) e + e - →γ ISR 

(c) 

– J/ψ sample: ~14x10 6 events 

– resonance production in the 

energy range 

– only production of J PC =1 -- states) 

 

b 

 

W 

c 

 

s 

 

(*) 

 

 

b 

 

charmonium 

c 

 

W 

 

q 

 

q 

open charm 

c 

q 

D(s) 

(*) 

 

c 

 

ð (*) 

Babar offers excellent options for charm / charmonium spectroscopy 


3

Spectrum of c mesons 

• Picture on c mesons still incomplete 

– established are D s , D s * , D s1 , D s2 

• Candidates for lowest, missing 

J P =0 + ,1 + states (discovered in 2003) 

D sJ* 

(2317) (→D s 

π 0 ) 

m=2317.4±0.9 MeV, Γ

• Put further experimental constraints on the two states 

D sJ studies at Babar 

• Comprehensive, exclusive study for 

e + e - →c fragmentation processes 

– investigation of D s 

π 0 , D s 

γ, D s 

π 0 γ, D s 

π 0 π 0 , D s 

γγ, D s 

π + π - final states 

– measurement of branching ratios, masses and widths 

– search for doubly charged / neutral D sJ 

*(2317) partners in D s 

π ± 

system (predicted by some molecule models) 

• Inclusive study of B→D (*) D sJ decays 

– measurement of absolute branching fractions 


5

Exclusive study of D sJ 

*(2317) 

• Only observed D sJ 

*(2317)→D s 

π 0 

m=(2319.6±0.2±1.4)MeV/c 2 

Γ

Exclusive study of D sJ (2460) 

• Observe decays to 

D s* 

π 0 (→D s 

π 0 γ), D s 

γ and D s 

π + π - 

• Upper limits on branching ratios 

for 5 other decay modes 

Babar: 232 fb -1 

hep-ex/0604030 

submitted to PRD 

N=560±40 

D s sidebands 

Reflections: 

N=920±60 

D s sidebands 

N=123±15 

D s sidebands 


7

Exclusive study of D sJ (2460) 

• Measurement of two branching ratios 


hep-ex/0604030 


• Combined results from three decay modes 

m=(2460.1±0.2±0.8)MeV/c 2 

Γ

Exclusive study: Summary 

• Decay patterns of D sJ* (2317) and D sJ (2460) are compatible with spinparity 

assignment 0 + and 1 + , respectively 


9

Inclusive study of D sJ (2460) 

• Fully reconstructed B reco 

and D * from 

other B signal 

→D (*) X, D s 

(*) 

X decay 

investigate recoil mass m X 

for signal 

• First measurement of absolute branching fractions (BF) 

for decays, e.g. 

e - 

B reco 

e 

B + 

signal D* 

X 

π 

D * 

• Combine with previously 

measured product BF and BRs / use 

Sum of known BFs is: (77±17)% 



hep-ex/0605036 


10

Exclusive study of the DK system 

• Exlusive study of the DK system 

in e + e - →c processes 

949k entries 

791k entries 

• Good kaon / pion identification 

• Clean K S →π + π - and π 0 →γγ selection 

• Kinematic fit to common vertex 

• CMS momentum p * (DK)>3.5 GeV 


preliminary 

432k entries 


11

Reflection: 

Observation of a new resonance at 2.86 GeV 

Entries / 20 MeV/c 2 

x10 3 x10 3 


D 0 sidebands 

• New structure at 2.86 GeV 

– absent in D 0 sidebands and e + e - →c MC events 

– no reflection from D * decays 

– not due to kaon/pion misidentification 

broad structure 

at ~2.7 GeV 

Entries / 20MeV/c 2 

D sJ 

*(2860) 

new structure 

D sJ 

*(2860) 

N=872±139 

6.3σ 

m(D 0 K + ) / GeV/c 2 

m(D 0 K + ) / GeV/c 2 

MC does not reproduce 

signal / reflection 

yields adequate due 

to poor knowledge of 

charm production in 

fragmentation processes 


preliminary 

12

Further studies of D sJ 

*(2860) 

• New structure also apparent in 

K + D 0 (→K - π + π 0 ) and K S 

D + (→K - π + π + ) 

with consistent mean and width 


preliminary 

D sidebands 

N=872±139 

6.3σ 

• Fit to sum of all 3 data samples yields to 

D sJ 

*(2860) + 

m=2856.6±1.5±5.0 MeV/c 2 

Γ=48±7±10 MeV 

D s2 (2572) + 

m=2572.2±0.3±1.0 MeV/c 2 

Γ=27.1±0.6±5.6 MeV 

broad structure at ~2.7 GeV needed to fit data 

(best parameterization: Gaussian) 

also indication for activity in that region at low p * values 

for D 0 →K - π + sidebands (reflection) 

if resonance: X(2690) + (Breit Wigner parameterization) 

m=2688±4±2 MeV/c 2 , Γ=112±7±36 MeV 

• Decay to DK implies natural spin-parity 

– is D sJ 

*(2860) the missing J P =3 - c state 

m(D 0 K + ) / GeV/c 2 

m(D 0 K + ) / GeV/c 2 

N=1099±214 

5.1σ 

N=585±212 

2.8σ 

• No indication for D sJ 

*(2860)→D * K decays found 


m(D + K S ) / GeV/c 2 

13

Charmonium candidates X(3872) and Y(4260) 

• Below Dð threshold 

– detailed information about J/ψ,ψ′, χ cJ 

– less knowledge on η c ,η′,h c 

• Above Dð threshold many predicted 

states still undetected 

Y(4260) 

• Two candidates in this region are 

X(3872) Dð * 

Dð 

X(3872) (→J/ψπ + π − , J/ψγ, D 0 ð 0 π 0 ψ´ 

) 

η´ 

h 

m=3871.2±0.6 MeV, Γ

• Tetra quark model 

– predicts nonet with two neutral states 

X u 

=[cu][ș] and X d 

=[cd][ñ] 

– X u 

and X d 

mix to two neutral states produced in B 0 and 

B + decays with same rate but 

mass difference of ∆(m)=(7±2) MeV 

– two charged partners X + =[cu][ñ] and X - =[cd][ș] 

should exist 

Exotic interpretations of X(3872) 

Maiani et al. 

PRD71, 014028 (2005) 

• S-wave Dð * molecule 

– motivated by proximity to D 0 ð 0* threshold 

– 10x suppressed BR 

of B 0 →KX wrt B + →K + X decay 

Braaten, Kusunoki 

PRD71, 074005 (2005) 

• Wide variety of other models 

proposed 

see e.g. Swanson 

hep-ph/0601110 

for detailed review 


15

Babar: 232M B 

PRD 73, 011101 (2006) 

Exclusive study of X(3872) 

N=61±15 

6.1σ 

N=8.3±4.5 

2.5σ 

m ES 

sidebands 

m ES 

sidebands 

Neither tetra-quark nor Dð * models 

excluded strictly, need more data 

Babar: 234M B 

PRD 71, 031501 (2005) 


No charged partners 

found in B→ K(J/ψπ 0 π ± ) 

isospin I=0 

in conflict with tetra-quark model 

16

Exclusive study of X(3872) 

• B + →K + X→K + (J/ψγ), decay to J/ψγ implies C=+1 

– [ππ] system in J/ψπ + π - : I=1, most probably P-wave [ππ] 

Babar: 287M B 

Preliminary 

X(3872): I=0, C=+1, J P =1 + favoured 

– X→J/ψπ + π - violates isospin conservation → small width / radiative decay 

X(3872) 

N=19.2 ± 5.7 

3.4σ 

• Confirms observation of 

4σ signal by Belle with 

consistent BF/BR 


17

Inclusive study of X(3872) 

• Fully reconstructed B - reco 

and identified 

K + from other B + → K + X c 

decay 

• Two body decay: Measured K + 

momentum in rest frame of recoil B 

defines m(X c 

) 

K + 

B + X c 

e - e + 

π 

Babar: 232M B 

PRL 96, 052002 (2006) 

B - reco 

D 

N(J/ψ)=259±41 

π 

K 

N(η c ) =273±43 

N(χ c1 

)=227±40 

X(3872) 


18

Discovery of Y(4260) 

• Negative search result for 

X(3872) production in ISR 

events with γ ISR detected, but 

discovered ... 

N=125±23 

8σ 


PRL 95, 142001 (2005) 

∼12000 ψ(2S) 

• Y(4260) in e + e - → γ ISR (π + π - J/ψ) 

– γ ISR 

need not to be detected 

– ISR implies J PC =1 -- 

– fit with one resonance 

hypothesis yields to: 

J/ψ sidebands 

Y(4260) 

– isospin I=0 

Confirmation 

• CLEO-c scan: Enhanced cross sections for 

e + e - →π + π - J/ψ (π 0 π 0 J/ψ) at √s=4.26 GeV 

• CLEO-III: Observation in 

e + e - → γ ISR (π + π - J/ψ) at √s=10.58GeV 


19

Search for other Y(4260) decays in ISR proccesses 

• e + e - →γ ISR 

(φπ + π - ) (γ ISR 

detected) 


preliminary 

J/ψ 

M(K + K - ) 

• e + e - →γ ISR 

(Dð) 

(γ ISR 

need not to be detected) 


preliminary 

at least 70x smaller than same BR for ψ(3770) 

shaded: φ sidebands 

no Y(4260) signal 

Events / 20 MeV/c 2 

ψ(3770) 

ψ(4040) 

ψ(4160) 

D sidebands 

no Y(4260) signal 

Also no signal found for 

e + e - →γ ISR 

(p) (γ ISR 

detected)) 


m(Dð) / GeV/c 2 


PRD 73, 012005 (2006) 

20

• X(3872) (→J/ψπ + π − , J/ψγ, D 0 ð 0 π 0 ) 

Charmonium candidates X(3872) and Y(4260) 

– m=3871.2±0.6 MeV/c 2 , Γ

• Discovery of new states in recent years has pushed experimental / 

theoretical activity in charm / charmonium spectroscopy 

Summary 

• Comprehensive study of D sJ* (2317) and D sJ (2460) 

– precise measurement of mass, width and branching ratios 

– first measurement of absolute D sJ (2460) branching fractions 

• Discovery of D sJ 

*(2860) state decaying to DK (brand new) 

• Charmonium candidates X(3872) and Y(4260) 

– studies on production processes and decay modes 

– further investigation required to understand the nature of these states 


22

Backup Slides 


23

Reconstruction 

• Clean sample 

– well identified K ± und π ± candidates 

– common vertex required 

– Momentum: p CM 

(D s 

)>2.2 GeV/c 

– >400.000 reconstructed 

D s 

→φ(K + K - )π + and 

D s 

→ * (K - π + )K + decays 

e - 

γ 

π 0 

γ 

K - 

K + 

π + 

D s e + 

• Combination of D s candidates 

with further γ,π 0 ,π ± of same event 

– Momentum: p CM 

(D sJ 

)>3.2 GeV/c 


24

Reflections in D s π 0 

Data 

MC 

Efficiency / 

resolution 


25

Reflections in D s π 0 γ 

Fraction of reflection underlying signal 

estimated from upper and lower 

D s* 

sidebands 

Upper sideband 

Signal region 

Lower sideband 


26


PRD 71, 031501 (2005) 

Search for charged partners of X(3872) 

3872 MeV 3872 MeV 

• No indication for charged partner states of X(3872) 


27

D sJ 

*(2860) study 

• No evidence for D sJ 

*(2860) 

decays to: 

D *0 K + , D *0 D 0 π 0 

D *0 K + , D *0 D 0 γ 

D ∗+ K 0 S , D*+ D + π 0 


28

Confirmation of Y(4260) from CLEO-III / CLEO-c 

• ISR production of π + π - J/ψ events 

in CLEO-III data near √s=10.58 GeV 

CLEO-III: 13.3 fb -1 

Preliminary 

• Enhanced cross sections at 

hep-ex/0602034 

4.26 GeV from CLEO-c scan hep-ex/0602034 

+ 

σ( 

e e 

− 

+ − 

→π 

π J ψ) 

= (58 

+ 12 

−10 ± 

N=37 (11 σ) 

4)pb 

σ( 

e 

+ 

e 

− 

0 0 

→π 

π J ψ) 

= (23 

+ 12 

−8 

N=8 (5.1 σ) 

± 1)pb 


29

Y(4260) production in B decays 

• Exclusive study of B + →K + (J/ψπ + π - ) decays 

Babar: 232M B 

PRD 73, 011101 (2006) 

• Indication for production in B decays 

– Signal lineshape uses mass and intrinsic width 

obtained from signal observed in ISR production 

– Needs confirmation 

N=128±42 

3.1σ 

4260 MeV 


30

ISR studies of Y(4260) 

• No indication for Y(4260) decay to p in ISR proccesses 


PRD 73, 012005 (2006) 


31

Marc Pelizaeus - Meson

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