Hadron Spectroscopy at BABAR
BY
Usha Mallik (University of Iowa)
Representing
The BaBar Collaboration
The International Light-Cone Workshop
July 7, 2005
Cairns, Australia
1
Topics:
 Hadron Spectroscopy:
–
–
–
–
Ds (cs) States : Inclusive and Exclusive studies
Double Charmonium Production; the X and the Y
Pentaquarks
Charmed Baryon studies
 Summary
 What can we learn from each other ?
2
The BABAR Detector at PEP-II and the Dataset
e  e   (4S )  BB
And Much More
Ecm = 10.58 GeV
Plan to Double Dataset by Next Summer
3
DSJ (cs) Spectroscopy
 New States DSJ(2317)+ and DSJ(2460)+
– First Observed Inclusively in e+e- Collisions
 Previously Established States with Likely JPC
Ground State DS(1969)+: JP=0-,
c and s spins opposite, in S-wave
DS (2112)+  1-(+) S-Wave (c and s spins aligned)
Ds
also DS 0
DS(2536)+  1+(+) P-Wave (needs confirmation)
D*(2010)+K0
D*(2007)0K+
DS(2573)+  2+(+) D-Wave (consistent with)
D0K+
4
Discovery of DsJ States
e+e-  cc  DsJ + X
DsJ
(2317)+
 Ds
DsJ(2460)+  Ds*+0
+0
Ds*  Ds
Discovery
Caution: These Decays
cross-feed
M(2460) – M(2112)
BABAR, BELLE, CLEO mutually confirm, also CDF (2317)
BaBar 125 fb-1
B(DsJ (2460)  Ds 0 )
 0.11 (95% CL)

 0
B(DsJ (2460)  Ds   )
Belle 87 fb-1
B(DsJ (2460)  Ds 0 )
 0.21 (90% CL)
B(DsJ (2460)  Ds* 0 )
5
*
DsJ
(2317)  Ds 0  J P  0  ,1 ,2  ,3...

DsJ
(2460)  Ds* 0 S  wave  J P  1 (also D-Wave)
P  wave  J P  0 ,1 ,2
• Decays violate isospin:  0   0 mixing
(for a conventional meson)
• Look for radiative and dipion transitions
• If DsJ* (2317) is 0
, expect DsJ* (2317)  Ds is forbidden
DsJ* (2317)  Ds   is forbidden

• If DsJ* (2460) is 1,expect DsJ (2460)  Ds is allowed


DsJ (2460)  Ds   is allowed
6
Search for DsJ→Ds
No DsJ ( 2317)
Excludes 0±
if present

DsJ
(2460)

BABAR
Belle 87 fb-1
B(DsJ (2317)  Ds )
 0.05 (90% CL)
 0
B(DsJ (2317)  Ds  )
B(DsJ (2460)  Ds )
 0.55  0.13  0.08
* 0
B(DsJ (2460)  Ds  )


DsJ(2317): compatible
with 0+
DsJ(2460): 0± excluded
BaBar 125 fb-1
B(DsJ (2317)  Ds )
 0.17 (95% CL)
 0
B(DsJ (2317)  Ds  )
B(DsJ (2460)  Ds )
 0.375  0.054  0.057
 0
B(DsJ (2460)  Ds   )
7
BABAR: PRD 69 (2004) 031101 (R) ; BELLE
 : PRL 92 (2004) 012002
DsJ(2460)
DsJ(2460) → Ds0
Kinematics
BABAR
high Ds* sideband
DsJ (2460)

*
s
DsJ* (2317)
reflection

D
reflection

low Ds* sideband


hep-ex/0408067
8
BELLE: PRL 91 (2003)262002
9
Exclusive Production of D*SJ in B ->DSJ(*)+ D(*)
Reconstruct one B: other is a B
for Study
 Kinematic Constraints Help, Even though Lower Stats
 Reduces Backgrounds
 Measure Ratios of Branching Fractions
 Measure Br
 Well-defined Initial State
 Test DSJ(*) Spin Assignments
10
mES 
B  DsJ
s / 4  pB*2
(*)+ D(*)
mES
E  E B*  s / 2
BABAR: PRL 93 (2004) 181801
Data sample: 122 million B pairs
m(DsJ)
Full reconstruction
of the exclusive
B decay
Sum over charged
and neutral B’s
DsJ*(2317)+
 Ds0
112 ± 14 events
DsJ(2460)+
 Ds*0
139 ± 17events
DsJ(2460)+
 Ds
We measure:

B.F .( DsJ (2460)   Ds  )

B.F .( DsJ (2460)   D*s  0 )

 0.274  0.045  0.020
BABAR
mES
m(DsJ)
11
B  DsJ (*)+D* Results
m(Ds+0)
DsJ(2317)
B0
m(Ds*+0)
DsJ(2460)
B+
B.F. (10-3)
B.F. Products
B0
(*)+
for BDsJ D*
B+
BABAR
m(Ds)
B0
B+
DsJ(2460)
B0
B+
DsJ*(2317)+  Ds0
DsJ(2460)+ Ds*0
DsJ(2460)+ Ds
1.5 ± 0.4 ± 0.2(+0.5-0.3)
5.5 ± 1.2 ± 1.0(+1.9-1.2)
2.3 ± 0.3 ± 0.3(+0.8-0.5)
0.9 ± 0.6 ± 0.2(+0.3-0.2)
7.6 ± 1.7 ± 1.8(+2.6-1.6)
1.4 ± 0.4 ± 0.3(+0.5-0.3)
in agreement with Belle results
12
BELLE: PRL 91 (2003) 262002 Data sample: ~124 million B pairs
B  DsJ
m(Ds+0)
DsJ(2317)
B0
(*)+D
m(Ds*+0)
DsJ(2460)
B+
B.F. Products
for BDsJ(*)+D
Results
BABAR
m(Ds)
B0
0
DsJ(2460) B 
B+
B+
B.F. (10-3)
DsJ*(2317)+  Ds0
DsJ(2460)+ Ds*0
B0
1.8 ± 0.4 ± 0.3(+0.6-0.4)
2.8 ± 0.8 ± 0.5(+1.0-0.6) 0.8 ± 0.2 ± 0.1(+0.3-0.2)
B+
1.0 ± 0.3 ± 0.1(+0.4-0.2)
2.7 ± 0.7 ± 0.5(+0.9-0.6) 0.6 ± 0.2 ± 0.1(+0.2-0.1)
in agreement with Belle results
DsJ(2460)+ Ds
13
Spin Analysis of B  DDSJ*
• Two body decay BDDSJ forces DSJ to populate
helicity zero only
0
B
h
DsJ
Ds(*)
–
D
 (cos  ) of daughter
• Analyze angular distribution
h
of DSJ
• BELLE Finds from Angular Distribution
– DSJ(2317)*
J = 0 (Preliminary)
14
BDsJ(2460)+D
BABAR
Ds

J=2
J=1
h
DsJ+ (2460)
Data points from m(Ds fits
corrected for detector acceptance
and efficiency
J=1 (c2=4.0/4) preferred to J=2 (c2=36.4/4)
confirms Belle measurement
15
Taking Stock of cs States
DsJ*(2317)+, DsJ (2460)+
DsJ (2573)+
Ds1(2536)+
Ds1(2460)
Ds0(2317)
Ds*+
Ds+
e.g. Godfrey-Isgur model
S-wave
P-wave
– Observed by BaBar, Belle and
CLEO
– Unexpectedly below threshold
for DK and D*K, respectively
– Consistent with P-wave cs
states but other interpretations
not ruled out
– If cs, observed decays
• DsJ*(2317)+  Ds+ 0
• DsJ (2460)+  Ds*+ 0
are isospin violating  narrow
– DsJ (2460)+  Ds+ 
also observed (and used to
determine J)
Several other explanations exist
e.g. Molecules or Hybrids
16
New Charmonium-like States
X(3872)  J/π+πCDF
PRL 93 072201 (2004)
Average Mass 3871.9 ± 0.5 MeV
Narrow  < 2.3 MeV @ 90% CL
(D0D*0 threshold at 3871.3 ± 1.0)
BELLE
BABAR
hep-ex/0406022
PRL 92 262001 (2003)
D0
PRL 93 162002 (2004)
17
Recent Update:
B+  X(3872)0K+ Reconstruction
Background from
B decays to same
final state J/K
BELLE (256 fb -1) hep-ex/0505038, BABAR hep-ex in preparation
18
About X(3872)
• Search for a Charged Partner
From 212 fb -1 Data BABAR Observed No Signal for XPhys. Rev. D71 : 031501, 2005
B(B0  X-K+, X-  J/ π-π0) < 5.4 X 10 -6 @ 90% CL
B(B-  X-KS, X-  J/ π-π0) < 11 X 10 -6 @ 90% CL
• Charmonium State : no isospin partner expected (data)
• Molecule State (?) : highly suppressed B0  X(3872) predicted
E. Braten, M. Kusunoki hep-ph/0412268
• Diquark-antidiquark State : different masses of X(3872)
in B0 and B+ decays predicted, |M| > 5 MeV
L. Maiani, F. Piccini, A.D. Polosa, V. Riquer PRD 71(2005) 01402819
B0 X(3872)0KS Reconstruction
Background
20
Other searches for X(3872)
BABAR
Search for X(3872) in events with initial state radiation (if JPC = 1-- )
PRD 71 (2005) 052001
Search for X(3872) in B  X(3872)K in the spectrum recoiling against K
from the B decays (with the other B fully reconstructed):
mes of all the
exclusively
reconstructed B
mES : B mass using beam energy
Use BABAR-BELLE average BF(B+  X(3872)K+, X(3872)J/) = (13.2  2.2) x 10 -6
B(X(3872) in B  X(3872)K, X(3872)  J/) < 3.2 X 10
and so, BF(X(3872)  J/+-)  4.3 %
-4
at 90% CL
21
BELLE: 256 fb -1
4.0 
C= +1 favored
hep-ex/0505037
Also X(3872) π+π-π0J/
X(3872) : +- Invariant Mass Distribution
BELLE: hep-ex/0505038
BABAR: hep-ex in prep.
Di-pion mass consistent with 0+- , again C =+1 ; S-wave J/  favored: J++ favored over J-+
Isospin violating: predicted
D0D*0 molecule, Swanson PLB 588 (2004) 189, Törnqvist PLB 590 (2004) 209
22
X(3872): BELLE Finds Data Disfavors 0++ and 2++, Leaving 1++
M[Ge
3872
DDThreshold
cc ? 1++ is cc1’
X(3872) is
too light
23
Double Charmonium Production
Study double charmonium in e+e- annihilation
}C=+1
c , cc , c(2S)
}C=-1
J/, (2S)
Theorists predict the cross sections of the two processes
to be comparable
G. T. Bodwin, E. Braaten & J. Lee
PRD67, 054023 (2003)
24
Reconstruct J/ or (2S) and Look at Recoil Mass
BABAR: 124 fb -1, hep-ex/0506062
c
c(2S)
cc0
BABAR
BELLE: PRD 70 (2004) 071102
25
Double Charmonium Production from BELLE
From BELLE
Evidence of X(3940): 4.5
m = 3940 ± 12 MeV,  < 96 MeV at 90% CL
26
A Near-threshold J/ Mass Enhancement in B  KJ/ at 3940 MeV/c2
BELLE
8 : 253 fb -1 with 59 ±11 Events
Is it the same as X(3940) ?
Dominantly cc
BELLE: Phys. Rev. Lett. 94: 182002, 2005
27
A Broad Structure in J/π+π- Mass near 4.26 GeV
e+e-  ISRJ/+- in Initial State Radiation
Recoil Mass Consistent with zero
BABAR: 211 fb-1 (preliminary)
125±23 excess
events
(2S)
28
hep-ex/0506081, submitted to PRL
•In addition to (2S) a Broad Structure is Observed in ISR Events
•JPC = 1-- ; Can be Characterized by a single Resonance
at 4.26 GeV and Width ~ 0.09 GeV
•Too low Statistics to Discern if Multiple States together
- (e.g. S and D waves can mix)
D*D* threshold
BABAR
3.77
Y(4260)  J/ S-wave phase space
BES, PRL 88 (2003), 101802
4.26
Why no rise in R ?
+ - mass distribution from Y(4260)
29
Pentaquark searches
Pentaquark discovery in 2003, ( confirmed by 13 experiments)
(statistical significance of individual experiments is not high ~5-6 )
Also many negative searches reported, especially a recent high statistics study by CLAS
Claims of exotic narrow baryons
LEPS, CLAS, …:
5
S
(1540)+ [uudds]
I3
M=(1542±5)MeV/c2
<21MeV/c2
NA49: X5(1860)  [ddssu]
M=(1862±2)MeV/c2
<18MeV/c2
H1: 5c(3100)0[uuddc]
M=(3099±6)MeV/c2
<28MeV/c2
The anti-decuplet for Pentaquarks
30
Inclusive and Exclusive Searches at BABAR
5+, X5--, X50, 5c0
31
e+e- annihilation (~123 fb -1)
hep-ex/0502004
accepted by PRL
32
accepted by PRL
33
Upper Limit
34
•So far, evidence of 5 claimed in
— real/virtual photoproduction
— hadroproduction
• photoproduction
No Signal Observed by CLAS in this Mode
with ~40 times Statistics , now repeating
other modes
BABAR studies electro- and hadro-production in interactions with the
material of the inner detector ; Observes no signal
35
BABAR 230 fb -1
e-
Detector Tomography with pKS0 vertices
e+
36
Clear Ks from  Decays Selected
Protons Selected from Particle ID
BABAR
pKs mass distribution
Mass resolution ~2 MeV
37
Associate p Ks Vertex with ± and K±
BABAR
(1115)
38
BABAR
No Pentaquark Observed by BABAR
39
Charmed Baryon Studies
 Precision Mass Measurement of C+ (cud)
 Production Process and Ratio of Branching Fractions of XC0 (csd)
cc or B  XC0 + X
 Production Process and Ratio of Branching Fractions of C0 (css)
cc or B  C0 + X
C0  - +
 - + - +
X-K- + +
40
BABAR
Mass Measurement of C+
Using Low-Q-value Decay Modes of C+  KSK+ and C+  0KSK+
BABAR Result : m(C+ ) = 2286.46 ± 0.14 MeV/c2
PDG Value 2284.9 ± 0.6 MeV/c2
m(C+  KsK+ ) = 2286.501 ± 0.042 (stat.) ± 0.144 (sys.) MeV/c2
m(C+  0KsK+ ) = 2286.303 ± 0.181 (stat.) ± 0.126 (sys.) MeV/c2
Cross-checks:
hep-ex/0507009, submitted to PRD
m(C+  pK+ ) = 2286.39 ± 0.12 (stat.) ± 0.45 (sys.) MeV/c2
m(C+  pKs) = 2286.36 ± 0.03 (stat.) ± 0.43 (sys.) MeV/c2
m() = 1115.68 ± 0.01 (stat.) ± 0.04 (sys.) MeV/c2 PDG Value = 1115.683 ± 0.006 MeV/c2
m(KS) = 497.56 ± 0.04 (stat.) ± 0.26 (sys.) MeV/c2 PDG Value = 497.648 ± 0.022 MeV/c2
41
Goals: Measure Ratio of Decay BFs
: Study Production Mechanism
BABAR
116 fb -1
Xc0X-π+
Xc0-K+
B(Xc0-K+)
B(Xc0X-π+)
= 0.294 ± 0.018 ± 0.016
hep-ex/0504014, submitted to PRL
42
BABAR
Study Xc0 Momentum (p*) in e+e- rest frame
116 fb -1
Xc
0 from
Xc0X-π+
B Decays
Xc0 peak from B’s absent in off-peak
hep-ex/0504014, submitted to PRL
Results:
Efficiency Corrected
 (e+e-  XC0X) •B (Xc0 X-+) = 388 ± 39(stat.) ± 41(syst.) fb
B (B X 0X) •B (X 0 X-+) = 2.11 ± 0.19(stat.) ± 0.25(syst.) 43
X 10 4
c
c
Inclusive c0 Studies
BABAR
Branching Fractions and Production Mechanism from p* Spectrum
Decay Modes of C0 Studied
 -+, -+- +, and X-K- + +
Results:
225 fb -1
C0-+
P* > 2.8 GeV/c
SLAC-PUB-11323, 44
hep-ex/0507011
The p* Spectrum from -π+ Mode
BABAR
B  C0 Production (First Observation)
Off-peak only
On & Off-peak
Not Corrected for Efficiency
Analysis in Progress
SLAC-PUB-11323 45
hep-ex/0507011
Summary & Conclusion
 Unfolding cs spectroscopy
 New States X(3872), Y(3940)… and Y(4260)?
 Copious Double Charmonium Production
 Pentaquark Fading ?
 Exciting Charmed Baryon Spectroscopy
 What can we Provide ?
46
47
48
49
50
Kaon momentum spectrum
51
*
sJ
D (2317) Kinematics
DsJ* (2317)

*
sJ
D (2317)



DsJ* (2317)
*
s
D
reflection


DsJ (2460)  Ds* (Ds ) 0
reflection





• Mutual cross feed
DsJ* (2317)  DsJ (2460)
• DsJ* (2317) and DsJ (2460)
widths are consistent
with zero
• No evidence for
DsJ (2460)  Ds 0
B(DsJ (2460)  Ds 0 )
 0.21 (90% CL)
B(DsJ (2460)  Ds* 0 )
-1
Belle 87 fb
B(DsJ (2460)  Ds 0 )
 0.11 (95% CL)

 0
B(DsJ (2460)  Ds   )
BaBar 125 fb-1
52

sJ
D (2460)
Search for DsJ→Ds
Excludes 0±
if present
BABAR

Belle 87 fb-1
B(DsJ (2317)  Ds )
 0.05 (90% CL)
 0
B(DsJ (2317)  Ds  )
B(DsJ (2460)  Ds )
 0.55  0.13  0.08
* 0
B(DsJ (2460)  Ds  )


DsJ(2317): compatible
with 0+
DsJ(2460): 0± excluded
BaBar 125 fb-1
B(DsJ (2317)  Ds )
 0.17 (95% CL)
 0
B(DsJ (2317)  Ds  )
B(DsJ (2460)  Ds )
 0.375  0.054  0.057
 0
B(DsJ (2460)  Ds   )
53
BABAR: PRD 69 (2004) 031101 (R) ; BELLE
 : PRL 92 (2004) 012002
54
55
56
57
Search in Inclusive B  XK Reconstruction
58
Branching fractions from b  xk study
59
60
Ds+
•
•
•
f p+ :Results
D* and g selection analogous to inclusive analysis
Ds+ f (K+K)  fully reconstructed
measure branching fraction product:
B (B0  Ds*+ D*) x B (Ds+ f+) = (8.71  0.78(stat)) x10-4
mES  s / 4  pB*2
Dividing by our measurement of
B(B0 Ds*+D*-), we obtain
B(Ds+ f+) = (4.71 ± 0.47(stat) ±0.35(syst))%
Signal 212 ±19
to be compared with
B(Ds+ f+) = (3.6 ± 0.9)%
(CLEO)
Readjustment of many results needed!
Not used yet for other results in this talk
61
Electroproduction in e-Be
BABAR
62