Gagan Mohanty

1
New Hadron Spectroscopy _at_ BaBar

• X(3872)
• Inclusive charmonia
• ee- ? J/? cc
• Y(4260)

New

• Gagan Mohanty
• University of Warwick
• Representing the BaBar collaboration

2
X(3872) Observation
Discovered by Belle in B ? KX(3872) with
X(3872) ? pp-J/? (compatible with ?J/?)
Belle PRL91, 262001
CDF PRL93, 072001

• CDF
• D0
• BaBar in 107 fb-1
  
  
  
  
  

confirm
BaBar PRD71, 071103
D0 PRL93, 162002
MX 3871.90.5 MeV/c2 GX lt 2.3 MeV _at_ 90 C.L.
Close to D0D0 threshold, Study other properties
3
X(3872) charged partner
If X(3872) were an isovector object, then
B(B?KX-) 2.B(B?KX0)
BaBar PRD 71, 031501 on 212 fb-1
Hypothesis is ruled out _at_ 10-4 confidence level
4
X(3872) Exclusive B decays
B?X(3872)K B0?X(3872)KS
pp-J/?
BaBar update hep-ex/0507090 on 211 fb-1
6.1s
2.5 s
N 61.215.3, MX 3871.30.60.1 MeV/c2
N 8.34.5, MX 3868.61.20.2 MeV/c2
R B(B0?X(3872)KS)/B(B?X(3872)K)
0.50.30.05 ?M 2.71.30.2 MeV/c2
5
X(3872) ISR production
BaBar PRD 71, 052001 on 89 fb-1
Search for ee- ? X(3872)?ISR X(3872)?J/? pp-,
J/??µµ- (?ISR is tagged in this sample)
?(2S)
X(3872)
Only possible, if JPC 1--
No signal observed
6
X(3872) Interpretation

• ?J/? mode stands against the charmonium
  assignment (an isospin violating decay)
• Standard quarkonium theory needs to be improved,
  if we want it to fit in correctly
• Mass being right at D0D0 threshold may be
  possibly due to
• Need more data to convincingly discriminate the
  models

• D0D0 molecule formation R 10-1
• Diquark-antidiquark (Xucu-cu or Xdcd-cd) state
  ?M 72 MeV/c2

Braaten et. al. PRD 71, 074005
Maiani et. al. PRD 71, 014028
7
Inclusive charmonia technique

• Fully reconstruct one of the Bs (robust NN to
  enhance S/B ratio)
• Find a recoiling K calculate its momentum in
  the other B rest frame calculate mX

BaBar Preliminary on 210 fb-1
Can measure the absolute B of X
8
Inclusive charmonia Results
BaBar Preliminary on 210 fb-1

• Clear J/?, ?c (7s) and ?c1 (6s) signal peaks
• Indication for ?(2S) (3s), ?(3770) (1.4s) and
  ?c(2S) (2s)
• No signature of X(3872), 90 UL on B(B?KX) lt
  3.2x10-4
• Using world average value of B(B?KX(3872).(X?J/
  ? pp)), we derive B(X(3872) ? J/? pp-) gt 4.2
  at 90 CL

9
Double Charmonium Production
Aim Technique
BaBar PRD 72, 031101 on 124 fb-1
Study ee- ? J/? cc

• Reconstruct a J/? cand.
• Compute its recoil mass

10
Double Charmonium Production (Theory vs.
Experiment)
PRL 88, 052001
PRD 67, 054007

dont include the B(? gt 2 tracks) factor
hep-ph/0408141

• Measured cross sections significantly differ
  from the theoretical predictions
• Recent works incorporating charm quark dynamics
  seem to resolve the conflict

hep-ph/0412335
hep-ph/0506076
11
Exploring ISR production
Recap from page 5
Features

• Photon from initial e/- states (mostly lost in
  beampipe)
• Small recoil mass against the final state low
  missing pT
• Well known benchmark channels e.g. J/?, ?(2S)

12
Y(4260) ISR production
BaBar hep-ex/0506081 on 233 fb-1 (accepted by
PRL)

• No X(3872)
• Observed Y(4260)

J/? sideband
?(2S)
8.2 s

• However, current dataset does not allow a
  statistically significant discrimination between
  single- and multi-resonance hypothesis

13
Y(4260) Exclusive B decays
BaBar hep-ex/0507090 on 211 fb-1 (page 4)

• Observed an excess of J/?pp- events with mass
  just above 4.2 GeV/c2
• Fixing M and G of this peak to the values from
  ISR analysis

3.1s

• N 12842
• B(B-?Y(4260)K-).B(Y?J/? pp-)
  (2.00.70.2)x10-5

14
Summary

• Hadron spectroscopy is one of most exciting
  pursued areas within BaBar (B factories in
  general)
• Ive selected only a few topics here
• These recent discoveries have created a renewed
  interest in the charmonium sector

• X(3872) is not fully understood (beg for more
  fb-1)
• Novel technique employed in inclusive charmonia
• Theory is catching up with experiment in J/? cc
• Y(4260) is just observed hunt-work continues

15
Back-up Slides
16
Inclusive charmonia Table
17
Y(4260) Interpretation

• Charmonium state?
• Molecule of Ds Ds- Y(4260) is just above
  threshold, 4225 MeV/c2 and no evidence for
  Y(4260) ? KK- J/?
• Molecule of D0 D0(2420) (threshold 4287
  MeV/c2)
• Hybrid (ccg)?
• Others?

Maiani et. al. PRD 72, 031502
Llanes-Estrada. hep-ph/0507035
Zhu hep-ph/0507025