1. Pentaquark Searches and DsJ Studies in BaBar
The 32nd International Conference on High Energy Physics
Beijing August 16-22
Pentaquark Searches and DsJ Studies in BaBar
Update on DsJ Masses
Inclusive Search for qs+(1540)
Inclusive Searches for X5(1860) states
Inclusive Search for Possible N5, S5 Pentaquarks
Search for q*++(~1600) in B+ppK+ Decays
Valerie Halyo (SLAC)
Representing the BaBar Collaboration
1/18/2019

2. The BaBar Experiment e+e-  hadrons Detector optimized for B physics
Excellent tracking
Excellent particle identification
Excellent g, p0 detection
Data:
=10.58 U(4s)
=10.54 qq
244 fb-1 recorded so far
256M B decays
510M uds events
317M cc events
1/18/2019

3. Particle Identification
dE/dx from Drift Chamber
Cherenkov angle from DIRC
Distinguishing between p, p/m, K
1/18/2019

4. DsJ Event selection Identify DsK+K-p+ along
with any number of p+, p0, g
Kaon identification
Vertex fit (c2 probability > 1%)
Consistent with production at the
interaction region
Eg >100 MeV
p* (momentum in center of mass)
larger than 2.5 GeV
See also talk by Mat Charles
(Heavy Quarks, Wed. Aug 18 HQ(5) )
1/18/2019
m(K+ K- p+) GeV/c2

5. Ds and Neutrals
1/18/2019

6. Ds and Neutrals Limits on
have large uncertainties due to overlapping reflections
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7. Ds and Neutrals Measure DsJ reflection yield Establish decay mode
2-dimensional likelihood fit
on projection
Sideband
Sideband
Signal
Region
Signal
Region
Sideband
Sideband
Ds+p0g Invariant Mass GeV/c2
Ds+g Invariant Mass GeV/c2
Ds+p0 Invariant Mass GeV/c2
1/18/2019

8. Ds and Charged Search for DsJ(2317) Partners Neutral D+sJp- system
Ds+p+p- Invariant Mass GeV/c2
Preliminary Results
From 3 modes
Double Charged D+sJp+ system
Ds+p+/- Invariant Mass GeV/c2
No signals evident
No evidence for 2317Ds+p+p-
1/18/2019

9. Motivation for Pentaquark Searches
Claims of Exotic Narrow Baryons
q+(ududs): LEPS+CLAS+others
m= MeV/c2
G< 21 MeV/c2
X--(dsdsu): NA49
m= MeV/c2
G< 18 MeV/c2
qc0(ududc): H1
m= MeV/c2
G < 28 MeV/c2
If pentaquark production is the same as other baryon production then we expect:
~ 8x10-4 qs+ per event
~ 4x10-5 X5-- per event
1/18/2019

10. The BaBar Search Strategy
Pentaquark theory expects q5s+, X5 to be
members of the
Dedicated searches for claimed states,
q5s+, X5--, X50, q5c0
Inclusive searches for other states in
the
Specific searches for selected states
from other multiplets :q*++ 5
1/18/2019

11. Search for q5+(1540)p Ks0 No Signal of q5+ Lc+(2285) 1540
Clean Ks0 p+p- reconstruction using geometrical cuts
Clean protons using dE/dx and Cherenkov angle
Clear Lc+ sample with events
No structure near 1540 MeV/c2
No narrow structure except Lc+
Many additional/different cuts tried; same results
1/18/2019

12. Lc+  p Ks0 Control Sample
Fit signal in bins of p*
Check mass scale
Shape of resolution function same
as simulation
Width of resolution function same
Yield consistent with expectations
(Efficiency ~30%)
Now fit for q5+:
P-wave Breit-Wigner signal x
Fthreshold resolution function
Resolution ~2 MeV/c2 due to
proximity to threshold
Assume G=8 MeV/c2 best experimental
upper limit
Assume G=1 MeV/c2 very narrow state
MC simulation of mass resolution tracks
data very well.
1/18/2019

13. q+ Cross Section and Upper Limit
Model independent limits on the total production cross 95% C.L. :
= G = 8 MeV/c2
< < fb
< 5.4x < 10.7x10-5 per qq event
< 17.9x < 35.0x10-5 per U(4s)
Fitted yields consistent with zero
We 95% C.L.
a model independent cross section
upper limit as a function of momentum
1/18/2019

14. Search for X5--X-p- and X50X-p+IP
We look for inclusive production of :
Geometrical selection of two displaced vertices
Loose particle ID
Select masses near the nominal L0 and X- masses
Control particles: X*0(1530)X-p+, Xc(2470) X-p+
1/18/2019

15. X-p-, X-p+ Invariant Mass
95% C.L. U.L. on X--
prod. cross section:
< fb
< 1.0x10-5 per qq
< 3.2x10-5 per U(4s)
(G = 18 MeV/c2)
No Signal of X5--
~5K events
~2K events
No Signal of X50
1/18/2019

16. Search for X50 L0 Ks0 No Signal of X50
Analysis method similar to above
Xc0 L0Ks0 seen, ~2K events
No Signal of X50
95% C.L. U.L. on X50 production cross-section x BF :
< 82.8 fb G=1MeV/c2
<204.7 fb G=18MeV/c2
<
1/18/2019

17. Search for X- L0 K- No Signal of X5- L0 selection as above
Combine with identified K-
Control particle W-, ~8K events
No Signal of X5-
95% C.L. U.L. on production cross-section x BF :
< 83.6 fb G=1MeV/c2
<181.0 fb G=18MeV/c2
1/18/2019

18. Additional Searches Also S0K+, S0K-, S0Ks0
N5+(uudss)L0K+
N50(uddss)L0Ks
S5+(uudss)pKs
Also S0K+, S0K-, S0Ks0
No unexpected narrow structure
M(p Ks) in [1.60 – 1.8 ] GeV/c2
1/18/2019

19. Results in perspective
Assume pentaquarks have J= ½
BF(q+p Ks0) = 25%
BF(X5-- X-p-) = 50%
BF for X5-, X50 very unclear
Limits are below expectations for
baryons:
q5+ by a factor of 8-15
X-- by a factor of 4-6
1/18/2019

20. Exclusive Search for q*++ (pK+)
Prediction for a q*++(uuuds) pentaquark
I=1, I3=1
m(q*++) = [1.43—1.7] GeV/c2
G = [37—80] MeV/c2
We searched in the exclusive
B+q*++ppK+p decay.
81 fb-1 data sample was used; 89M BB
events
“Standard” B decay analysis used,
(see talks in CP-violation, Heavy
Quark sessions)
1/18/2019

21. BppK+ Measurement BF(BppK+) = (6.7 0.9(stat.) 0.6(syst.))x10-6
5.276 < mES < GeV
DE < 29 MeV
212 events in the signal region
~68 events have charmonium decays to pp
~40 background events
BF(BppK+) = ( (stat.) 0.6(syst.))x10-6
1/18/2019

22. Upper Limit on q*++ BF(B+q*++(pK+)p) < 1.49x10-7 @ 90% C.L.
Projection on pK+ axis
Events outside the
Charmonium region
Events in the
Charmonium region
No entries for m q*++ < 1850 MeV/c2
BF(B+q*++(pK+)p) < 90% C.L.
1/18/2019

23. Summary Improved measurements of DsJ*(2317), DsJ(2460),
DsI(2536) masses.
Many L0, X-, X*0, -, Xc0, Lc+ baryons found in our data.
No signal for any pentaquark seen:
Production of q+(1540), X--(1860) well below ordinary baryons of similar mass.
No narrow peaks for hypothetical states in several search modes.
No signal for the hypothetical q*++pK+;
BF(B+q*++ppK+p) < 90% C.L.
1/18/2019