Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Charm Baryon Spectroscopy at Belle (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 + K 0 S  - (preliminary) (6) Search for the SELEX double charm baryon decaying into  c + K -  + (preliminary) (7) Summary Ruslan Chistov (ITEP, Moscow) Charm 2006 Bejing 5-7 June, 2006

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Introduction to Charm Baryons at Belle 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 + K 0 S  - final states *and study of excited states  c (2645)

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Signal  c + sideband Feeddown from  c(2880)+ Observation of  c (2800): (PRL 94, (2005)) c+-c+-c+-c+- c+0c+0c+0c+0 c++c++c++c++ ISOTRIPLET!

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 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 J P =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  c (2800): Discussion

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Introduction to Charm Baryons at Belle Improved measurement of  c 0 and  c + masses PLB 605, 237 (2005) The  c ’s are reconstructed in 7 decay modes K-+K-+ pK-K-+pK-K-+ KS0KS0 pKS0KS0pKS0KS0 K-++K-++ -+-+ -++-++

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Introduction to Charm Baryons at Belle Improved measurement of  c 0 and  c + masses PLB 605, 237 (2005), Erratum PLB 617, 198 (2005) Due to the mass scale

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Study of excited states  c (2645) Mass( c +  - ) Mass( C 0  + )  C (2645) 0  C (2645) + Reflection from  C (2790) 0   c ’+  -,  c ’ +   c +  (verified with MC) Reflection from  C (2790) +   c ’0  + (verified with MC)  c ’ 0   c 0  C+  - ++C+  - ++ C0  - +C0  - + L 450 fb -1 First confirmation

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Study of excited states  c (2645): mass measurements Belle (2006): PDG(2005): Preliminary

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm New Charmed Baryons from Belle  cx (2980) + and  cx (3077) + Near threshold in Mass(  c + K -  + ) two new charmed baryons  cx (2980) + and  cx (3077) + were observed  cx (2980) +  cx (3077) + wrong-sign  c + K +  -  cx (3077) + : 9.7  N=326.0 ± 39.6 events M= ± 0.9 ± 0.5 MeV  =6.2 ± 1.2 ± 0.8 MeV  cx (2980) + : 6.3  N=405.3 ± 50.7 events M= ± 2.1 ± 2.0 MeV  =43.5 ± 7.5 ± 7.0 MeV Preliminary L 450 fb -1

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm New Charmed Baryons from Belle  cx (3077) 0 To get more information about the properties of found states we searched for their isopartners in Mass(  c + K 0 S  - ) and observe  cx (3077) 0  cx (2980) 0  cx (3077) 0 wrong-sign  c + K +  - High mass state -  cx (3077) 0 N=67.1 ± 19.9 M= ± 1.8 MeV  =5.2 ± 3.1 MeV Significance=5.1  Low mass state -  cx (2980) 0 N= 42.3 ± 23.8 M= ± 8.8 MeV  =43.6 MeV FIXED Significance=2.0  Preliminary L 450 fb -1

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Recent Results from Belle Belle searched for the SELEX double charm baryon  cc (3520) +   c + K -  + null result Preliminary N=8.3 ± 37.3 < 90% CL L 450 fb -1

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Recent Results from Belle: upper limit on the production of the SELEX double charm baryon Preliminary  (  cc (3520) + )  Br(  cc (3520) +  c + K -  + | p*(  c + )>2.5 GeV) <1.5   (  c + | p*(  c+)>2.5 90% CL We reconstruct ±  c +  pK -  + decays BaBar observes NO SIGNAL ALSO in a similar decay mode (hep-ex/ )

Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm Summary (1)NEW Isotriplet of Charmed Baryons is observed by Belle:  c (2800) (2) Belle measured with high accuracy the masses of  c 0  c +  c 0 and  c +  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 + K S 0  - Studies of their properties are ongoing