1. Spectroscopy Today BaBar’s Contributions
Veronique Ziegler
Jefferson Lab

2. Highlights from BaBar * charm * light quark * heavy quark Spectroscopy
BaBar last day of running
Highlights from BaBar * charm * light quark * heavy quark Spectroscopy

3. Charm spectroscopy

4. The DsJ States Discoveries_
Before 2003, 4 cs mesons known
2 S-wave mesons, Ds (JP = 0−) and Ds∗ (1−)
2 P-wave mesons, Ds1(2536) (1+) and Ds2(2573) (2+)
Potential model mass predictions were in good
agreement with the measured masses.
BaBar discovery of two new states in 2003
Ds0∗(2317)+ → Ds+ π0
Ds1 (2460)+ → Ds*+ π0
with masses well below those predicted by existing potential models and this led to search for alternate interpretations
BaBar discovery of the DsJ∗(2860)
DsJ*(2860)+ → D0 K+
DsJ*(2860)+ → D+ KS
and another structure in the 2.7 GeV/c2
mass region
adding yet another component to the
complex DsJ spectroscopy picture…
Phys.Rev.Lett (2003)
754 citations
Phys.Rev.Lett (2006)
146 citations

5. BaBar as a Charm Baryon Factory
Access to rare decay modes &
High precision studies of charm baryon properties ...

6. A Precision Measurement of the Lc+ Mass
Using low Q-value modes
Phys.Rev.D72:052006,2005
First Observation
PDG
PDG
Baryon (decaying to a Lc+) masses estimated as mass differences w.r.t. the Lc+ with PDG Lc+ mass added  more precise Lc+ mass measurement affects these baryon mass measurements

7. Charm Baryon Production at the U(4S) Resonance
Typical c.m. momentum (p*) distribution
Production from B decays (+some continuum)
Continuum production

8. Production from B decays
Study of baryon production in B decays
Substantial B meson decay to Xc* 0,+
First observations of these decays
Branching Fractions & cross section
measurements
BF measurement (Phys. Rev. D 78, (2008))
indicates 3-body final state favored in agreement with the predictions of
Hou and Soni (Phys. Rev. Lett. 86, 4247 (2001))
Spin measurement possibilities (Phys. Rev. D 78, (2008))
Use of B-  Lc+ p p- to get mass, width
and spin of Sc(2455) distribution favors
spin 1/2 [solid line] over
spin 3/2 [dotted curve]
efficiency-corrected
background-subtracted _

9. Production from continuum
Precision mass and width measurements on excited charm cascades
Observation of the Xc(2980)+,0 and Xc(3077)+,0 & evidence for the Xc(3055)+ and the Xc(3123)+
First observation of the excited singly charmed baryon 􏰛􏰟Wc*(css) in the radiative decay Wc*  􏰛Wc0 g􏰩
First observation of a charm baryons decaying
to a charm meson
First observation of the Lc(2880)+ in D0p decay
Discovery of a new state at m = MeV/c2

10. Light Quark Spectroscopy
From charm baryon decays

11. Spin measurement of W- from Xc0 → W- K+, W- → L K- decays
PRL 97, (2006)

12. Analysis of Lc+ → X- p+ K+ to obtain X(1530) spin information
Only obvious structure:
X (1530)0 → X- p+
Lc+ signal region
Rectangular Dalitz plot
Note: m2(X- K+) depends linearly on cosqX

13. Analysis of Lc+ → X- p+ K+ to obtain X(1530) spin information
unweighted
uncorrected
Lc+ signal region
Efficiency-corrected
P4 Moment Dist.
X(1530)0
wj = (7/ √2) P4(cosq)
from Lc+ signal region
efficiency-corrected unweighted
m(X- p+) distribution in data
Spin 5/2 Test
PL moments (L ≥ 6) give no signal
wj = √10 P2(cosq)
Efficiency-corrected
P2 Moment Dist.
 spin 3/2 clearly established
 spin 5/2 ruled out
wj = √10 P2(cosq)
from Lc+ signal region
Spin 3/2 Test
analysis by establishing J=3/2 also established positive parity
(i.e. P-wave)

14. Dalitz Plot for Lc+ → L KS K+
Accumulation of events in KSK+
near threshold  evidence of a0(980)+
Background-subtracted, efficiency-corrected data
― Integrated signal function smeared by mass
resolution [Histogram]
― Signal function with no resolution smearing
― |A(a0(980)|2 contribution
― |A(X(1690)|2 contribution
― Interference term contribution
a0(980)+
For J(X[1690]) = 1/2
cosqL 14
X(1690)0
m(L KS) (GeV/c2)

15. BaBar’s contributions to charm baryon spectroscopy
Insight into charm baryon production
Measurements of charm baryon spin from exclusive B decay processes
Insight into light quark spectroscopy from hyperon resonances produced in charm baryon decay

16. Quarkonium spectroscopy

17. The discovery of charmonium
Discovery of a narrow width state with mass 3.1 GeV
by SLAC
and BNL
pN → e+e- X J
BNL
SLAC
ψ(3100)
e+e-→hadrons
J/ψ resonance
PRL 33, 1404 (1974)
PRL 33, 1406 (1974)
discovery of the charm quark,
J/y was the first observed cc bound state

18. Charmonium Production Mechanisms
B → cc K(*) decay
Initial state radiation
JPC = 1- -
Two-photon collision
Double charmonium
production
C= +, J= 0, 2
Recoil against
J/y  C = +

19. All charmonium production mechanisms seen at BaBar
The X(3872): a charmonium-like state in B± → K± J/ψ p+p- decays
(PRD77, (2008)) opened the
door to exotic meson interpretations
BaBar pins down C-parity (+) from observation of the X in J/y g and excludes the isovector hypothesis from lack of evidence for a charged partner
BaBar discovers the Y(4260) in ISR:
e+e- → gISR Y(4260) → J/ψ p+p- decays
and the subsequently the Y(4350) in
e+e- → gISR Y(4350) → ψ(2S) p+p-
(PRL95, (2006))
Improbable interpretation of both states as charmonium
Y(4260) → J/ψ p+p-
Also significant BaBar contributions to charmonium states seen in double charmonium production & 2 photon collisions
(e.g. gg → hc → K+ K- p0,h [PRD 89, (2014))

20. The discovery of bottomonium
observed bb bound state
CUSB Collaboration 20

21. over 30 years of discoveries in the Bottomonium Sector!
Opened the door…
over 30 years of discoveries in the Bottomonium Sector! 21

22. The Search for the hb at BaBar

23. The hb(1S) discovered in Y(3S) data and confirmed in Y(2S) data
BF measurements:
B((3S)  ghb(1S)) = (5.1 ± 0.7)  B((2S)  ghb(1S)) = (3.9 ± 1.5)  10- 4
Compatible with predictions
Combined values of mass and HF splitting:
mhb(1S) = ± 2.8 MeV/c2 (Ghb(1S)  10 MeV)
(m(1S) – mhb(1S)) = 69.3 ± 2.8 MeV/c2 hb hb
S. Godfrey, J.L. Rosner
PRD (2001)

24. Detailed studies of bottomonium transitions from U(3S) events using g→e+e- conversions
Resolution dominated
Small Doppler broadening

25. Evidence for the hb(1P) in the decay U(3S) pohb
background-subtracted result:
hb signal region
uncertainty from background fit
10814± 2813 signal events
M(hb) = 9902±4 ±2 MeV/c2 (C.G.= ±0.27 MeV/c2 )
Phys.Rev. D84 (2011)

26. The hb(1P) and hb(2P) seen by Belle in e+e-→ p+p- transitions at the U(5S)
Phys.Rev.Lett. 108, (2012)
p+p- recoil mass spectrum
hb(2P)
hb(1P)
Measured hb(1,2P) mass values consistent with predictions
BaBar hb(1P) mass measurement consistent with Belle’s
Observed hb production rate enhancement may be indicative of exotic process violating HQ spin-flip suppression 26

27. Future directions Spectroscopy at J-Lab with 12 GeV
Unique photo-production research opportunities to identify exotics by amplitude analyses of final states
hadron spectroscopy by coherent bremsstrahlung production in Hall D
and by tagged (quasi-)real photoproduction in Hall B to yield complementary results
Many new results from the LHC
spectroscopy of X, Y, Z states, bottomonium spectroscopy
heavy flavor baryon data, …
COMPASS hadron program is to study the light-quark hadron spectrum, and in particular, to search for evidence of hybrids and glueballs (COMPASS confirms previous Brookhaven discovery of the π1(1600) 1-+ wave in rp).
BESIII continues to make detailed explorations of the region just above the charmonium threshold.
BaBar continues to produce interesting results such as the analysis of B→J/ψ f K [hep-ex , recently accepted in PRD] that shows an interesting structure in m(J/ψ f)… 27