Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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Charm Baryon SpectroscopyCharm Baryon Spectroscopy atat BelleBelle

(1) Introduction to charmed baryons at Belle (2) Observation of c(2800) in e+e- continuum (3) Improved measurement of c

0 and c+ masses

(4) Study of excited states c(2645) (preliminary)

(5) Observation of new charmed baryons decaying into c

+ K- + and c+ K0

S - (preliminary) (6) Search for the SELEX double charm baryon decaying into c

+ K- +

(preliminary) (7) Summary

Ruslan ChistovRuslan Chistov(ITEP, Moscow)(ITEP, Moscow)

Charm 2006 Bejing 5-7 June, 2006

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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Introduction to Charm Baryons at Introduction to Charm Baryons at BelleBelle

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). This year recent results from Belle include also *observation of new charm baryons in c

+ K- + and c+ K0

S - final states *and study of excited states c(2645)

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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Signal

c+ sideband

Feeddown from c(2880)+

Observation of Observation of cc(2800): (2800): (PRL 94, 12202 (2005))(PRL 94, 12202 (2005))

cc++-- cc

++00 cc++++

ISOTRIPLET!

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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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.

Observation of Observation of cc(2800): (2800): DiscussionDiscussion

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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Introduction to Charm Baryons at Introduction to Charm Baryons at BelleBelle

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

K-+

pK-K-+

KS0 pKS

0KS0

K-++

-+

-++

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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Introduction to Charm Baryons at Introduction to Charm Baryons at BelleBelle

Improved measurement of Improved measurement of cc

00 and and cc++ masses masses

PLB 605, 237 (2005),Erratum PLB 617, 198 (2005)

+0.2-1.4

+0.2-1.4

Due to the mass scale

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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StudyStudy of excited states of excited states cc(2645)(2645)

Mass(c+ -) Mass(C

0 +)

CC(2645)(2645)00 CC(2645)(2645)++

Reflection from C(2790)0 c

’+ -,

c’+ c+

(verified with MC)

Reflection fromC(2790)+ c

’0 +

(verified with MC)c’0 c

0

C+ - ++ C

0 - +

LL450 fb450 fb-1-1

Firs

t co

nfirm

atio

n

Firs

t co

nfirm

atio

n

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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StudyStudy of excited states of excited states cc(2645):(2645):mass measurementsmass measurements

Belle (2006):

PDG(2005):

Pre

lim

inary

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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New Charmed Baryons from BelleNew Charmed Baryons from Belle

Near threshold in Mass(c+ K- +) two new charmed

baryons cxcx(2980)(2980)++ and and cxcx(3077)(3077)++ were observed

cx(2980)+

cx(3077)+

wrong-sign c+ K+ -

cx(3077)+: 9.7N=326.0 ± 39.6 events

M=3076.7 ± 0.9 ± 0.5 MeV=6.2 ± 1.2 ± 0.8 MeV

cx(2980)+: 6.3N=405.3 ± 50.7 events

M=2978.5 ± 2.1 ± 2.0 MeV=43.5 ± 7.5 ± 7.0 MeV

Preliminary

LL450 fb450 fb-1-1

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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New Charmed Baryons from BelleNew Charmed Baryons from BelleTo get more information about the properties of found states

we searched for their isopartners in Mass(c+ K0

S -) and observe cxcx(3077)(3077)00

cx(2980)0

cx(3077)0

wrong-sign c+ K+ -

High mass state - cx(3077)0

N=67.1 ± 19.9M=3082.8 ± 1.8 MeV=5.2 ± 3.1 MeVSignificance=5.1

Low mass state - cx(2980)0

N= 42.3 ± 23.8M=2977.1 ± 8.8 MeV=43.6 MeV FIXEDSignificance=2.0

Preliminary

LL450 fb450 fb-1-1

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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Recent Results from Belle Recent Results from Belle

Belle searched for the SELEX double charm baryon cc (3520)+ c

+ K- +

null result

Prelim

inary

N=8.3 ± 37.3 < 69.1 @ 90% CL

LL450 fb450 fb-1-1

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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Recent Results from Belle:Recent Results from Belle:upper limit on the production upper limit on the production

of the SELEX double charm baryon of the SELEX double charm baryon

Preliminary

(cc(3520)+)Br(cc(3520)+c+K-+ | p*(c

+)>2.5 GeV) <1.510-4

(c+ | p*(c+)>2.5 GeV) @ 90% CL

We reconstruct 835360 ± 13748 c+ pK-+decays

BaBar observes NO SIGNAL ALSO in a similar decay mode (hep-ex/0605075)

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006

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SummarySummary

(1) NEW Isotriplet of Charmed Baryons is observed by Belle: c(2800)(2) Belle measured with high accuracy the masses of cc

00 and cc++

c(2645)0 and c(2645)+ (3) Belle searched for the SELEX double charm baryon cc(3520)+, found no signal and set an UL on its production cross-section Belle observed three new charm baryons Belle observed three new charm baryons

cx(3077)+ c+ K- +

cx(2980)+ c+ K- +

cx(3077)0 c+ KS

0 -

Studies of their properties are ongoing