Ruslan Chistov (ITEP, Moscow)
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Charmed BaryonsCharmed Baryons atat BelleBelle
OUTLINE:(1) Introduction (2) Brief experimental review of baryonic B decays(3) Recent results from Belle: Observation of B decays to two charmed baryons: B+ 0
c c+ (similar to B0 c
- p)
B c+ c
- K(4) Brief experimental review of charm baryon
spectroscopy (5) Recent results from Belle: Observation of c(2800) in e+e- continuum
Improved measurement of c0 and c
+ masses (6) Summary
International Workshop e+e- Collisions from to Budker Institute of Nuclear Physics, Novosibirsk, Russia (Feb 27-March 2, 2006)
Ruslan Chistov (ITEP, Moscow)
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IntroductionIntroduction
Now B-factories Belle and BaBar are the reachest sources of charmed baryons.
They could provide new knowledge about the spectroscopy, decay modes and production mechanism of charmed baryons.
Study of baryonic B decaysCharmed baryons
in e+e- cc continuum
Ruslan Chistov (ITEP, Moscow)
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Experimental Review of Baryonic B DecaysExperimental Review of Baryonic B Decays (1)(1)
Ruslan Chistov (ITEP, Moscow)
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Experimental Review of Baryonic B Decays(2)Experimental Review of Baryonic B Decays(2)
Histograms are phase space expectation
Ruslan Chistov (ITEP, Moscow)
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Experimental Review of Baryonic B Decays (3)Experimental Review of Baryonic B Decays (3)
Ruslan Chistov (ITEP, Moscow)
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BB00 cc-- p and B p and B++ 00
cc cc++
PRL 90, 121802 (2003)
Br=(2.19+0.56-0.49+-0.32+-0.57)x 10-5
Consistent with the pole model prediction
but 100 times smaller than QCD
sum rule predictions and diquark models
One can expect Br ~ 10-5
Belle
Ruslan Chistov (ITEP, Moscow)
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Observation of BObservation of B++ 00cc cc
++
hep-ex/0510074
So, the naïve expectation is wrong
Ruslan Chistov (ITEP, Moscow)
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Evidence for BEvidence for B++ --cc cc
++
hep-ex/0510074
Ruslan Chistov (ITEP, Moscow)
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Observation of BObservation of B-- cc+ + cc
-- K K++
hep-ex/0508015
The Br’s of 2- and 3-body double charm baryonic decays are approximately the same in contrast of single charm baryonic decays.
Ruslan Chistov (ITEP, Moscow)
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Observation of BObservation of B00 cc+ + cc
-- K K00
hep-ex/0508015
Ruslan Chistov (ITEP, Moscow)
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Experimental review of charm Experimental review of charm baryon spectroscopy baryon spectroscopy
Charmed baryon spectroscopy is an excellent laboratory to study the dynamics of light diquark in the environment of heavy C-quark. Many theoretical predictions and approaches could be tested.
History: ARGUS(1993) observed first excited charmed baryon c(2625)+,then CLEO(1993) confirmed it and observed c(2593)+, E687 and ARGUS subsequently confirmed the latter. Next observations came from CLEO:c(2520)+, c(2765)+, c(2880)+.
Belle(2005): Observation of first orbital excitation of c : c(2800).
Ruslan Chistov (ITEP, Moscow)
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Observation of Observation of cc(2800): (2800): Results (PRL 94, 12202 (2005))Results (PRL 94, 12202 (2005))
Signal
c+ sideband
Feeddown from c(2880)+
Ruslan Chistov (ITEP, Moscow)
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Observation of Observation of cc(2800): (2800): Results (PRL 94, 12202 (2005))Results (PRL 94, 12202 (2005))
p=0.078+0.021-0.017
p=0.095+0.032-0.024
p=0.069+0.015-0.012
Xp spectra of observed resonances
Peterson parameters are similar to those for other excited charm baryons in e+e- annihilation at s ~ 10.6 GeV
Ruslan Chistov (ITEP, Moscow)
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Observation of Observation of cc(2800): (2800): Discussion Discussion
Theoretical models predict a rich spectrum of excited charmed baryons in the vicinity of the c(2800) [L.A.Copley, N.Isgur and G.Karl, Phys. Rev D 20, 768 (1979)].
One of the candidates is a c2 doublet with JP=3/2- and 5/2- (subscript 2 denotes the total angular momentum of light diquark.)c2 is expected to decay principally into c
+ in D-wave.
The predicted mass is close to the measured but the predicted width is only 15 MeV.
But the c2 (3/2-) can mix with the nearby c1 (3/2-) which would produce a wider physical state.
Ruslan Chistov (ITEP, Moscow)
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Improved measurement of Improved measurement of cc
00 and and cc++ masses masses
PLB 605, 237 (2005)
The c’s are reconstructed in 7 decay modes
Ruslan Chistov (ITEP, Moscow)
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Improved measurement of Improved measurement of cc
00 and and cc++ masses masses
PLB 605, 237 (2005)
+0.2-1.4
+0.2-1.4
Ruslan Chistov (ITEP, Moscow)
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SummarySummary
(2) NEW Charmed Baryon is observed by Belle:
c(2800)(3) Belle measured the 00
cc and cc++ masses with high
accuracy Large statistics collected by Belle opens a possibility for study ofB->baryons and new charmed baryons understand underlying QCD effects in heavy hadron system.
(1) Belle observed new type of B decays: BB++ cc
00 cc++ and B and B cc
++ cc-- K - decays to two charmed baryons K - decays to two charmed baryons
These are the bThese are the bccs transitions that have not been ccs transitions that have not been observed previously. observed previously. The B The B cc
++ cc-- K K have prominent Br but small energy release.
The Br(BB++ cc00 cc
++) is presumably ) is presumably 100 times larger than the bcud analog: the BB00 cc
-- p p decay. The question is to theoretically understand these observations (coherent and unified description of baryonic B decays).
Ruslan Chistov (ITEP, Moscow)
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KEKB asymmetric eKEKB asymmetric e++ee-- collider collider
Two separate ringse+ : 3.5GeVe- : 8.0GeV
Crossing angle 22mradEcm : 10.58GeV
c 200m
Beam size:x = 100m
y = 3m
Luminosity: design: 1.0x1034 cm-2s-1
achieved: 1.07x1034 cm-2s-1
Ruslan Chistov (ITEP, Moscow)
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Belle detectorBelle detector
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