Charmed Baryons at Belle

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)

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Experimental Review of Baryonic B Decays(2)Experimental Review of Baryonic B Decays(2)

Histograms are phase space expectation

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Experimental Review of Baryonic B Decays (3)Experimental Review of Baryonic B Decays (3)

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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

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Observation of BObservation of B++ 00cc cc

++

hep-ex/0510074

So, the naïve expectation is wrong

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Evidence for BEvidence for B++ --cc cc

++

hep-ex/0510074

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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.

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Observation of BObservation of B00 cc+ + cc

-- K K00

hep-ex/0508015

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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).

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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)+

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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

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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.

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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

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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

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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).

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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

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Belle detectorBelle detector