Charm 2006 Bejing 5 7 June 2006 Charm

Charm 2006 Bejing 5 -7 June, 2006 Charm Baryon Spectroscopy at Belle Ruslan Chistov (ITEP, Moscow) (1) (2) (3) (4) (5) Introduction to charmed baryons at Belle Observation of c(2800) in e+e- continuum Improved measurement of c 0 and c+ masses Study of excited states c(2645) (preliminary) 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- + (7) Summary (preliminary) Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006 1

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)+, E 687 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 2006 2

Observation of c(2800): (PRL 94, 12202 (2005)) c+ - c+ 0 c+ + Feeddown from c(2880)+ Signal c+ sideband ISOTRIPLET! Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006 3

Observation of c(2800): 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 c 2 doublet with JP=3/2 - and 5/2(subscript 2 denotes the total angular momentum of light diquark. ) c 2 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 Me. V. But the c 2 (3/2 -) can mix with the nearby c 1 (3/2 -) which would produce a wider physical state. Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006 4

Introduction Charm Baryons Improved to measurement of + masses c 0 and at Belle c PLB 605, 237 (2005) The c’s are reconstructed in 7 decay modes K- + + p. K-K- + + KS 0 p. KS 0 Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006 5

Introduction Charm Baryons Improved to measurement of + masses c 0 and at Belle c PLB 605, 237 (2005), Erratum PLB 617, 198 (2005) Due to the mass scale +0. 2 -1. 4 Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006 6

Study of excited states c(2645) L 450 fb-1 Reflection from C(2790)0 c’+ -, c’+ c+ (verified with MC) Mass( c+ -) C+ - + + C(2645)+ Reflection from C(2790)+ c’ 0 + (verified with MC) c’ 0 c 0 Mass( C 0 +) C 0 - + Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Fir st c onf irm ati on C(2645)0 Charm 2006 7

Study of excited states c(2645): mass measurements Preliminary Belle (2006): PDG(2005): Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006 8

New Charmed Baryons from Belle Near threshold in Mass( c+ K- +) two new charmed baryons cx(2980)+ and cx(3077)+ were observed -1 L 450 fb-1 cx(3077) +: 9. 7 N=326. 0 ± 39. 6 events M=3076. 7 ± 0. 9 ± 0. 5 Me. V =6. 2 ± 1. 2 ± 0. 8 Me. V cx(3077)+ cx(2980) +: 6. 3 cx(2980)+ N=405. 3 ± 50. 7 events M=2978. 5 ± 2. 1 ± 2. 0 Me. V =43. 5 ± 7. 0 Me. V wrong-sign c+ K+ - y r a il min Pre Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle Charm 2006 9

New Charmed Baryons from Belle 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 L 450 fb-1 cx(3077)0 cx(2980)0 wrong-sign c+ K+ - High mass state - cx(3077) 0 N=67. 1 ± 19. 9 M=3082. 8 ± 1. 8 Me. V =5. 2 ± 3. 1 Me. V Significance=5. 1 Low mass state - cx(2980) 0 N= 42. 3 ± 23. 8 M=2977. 1 ± 8. 8 Me. V =43. 6 Me. V FIXED Significance=2. 0 y r a il min Pre Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle 10 Charm 2006

Recent Results from Belle searched for the SELEX double charm baryon cc (3520)+ c+ K- + L 450 fb-1 null result N=8. 3 ± 37. 3 < 69. 1 @ 90% CL Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle n i m er li P y r a 11 Charm 2006

Recent Results from Belle: upper limit on the production of the SELEX double charm baryon We reconstruct 835360 ± 13748 c+ p. K- +decays ( cc(3520)+) Br( cc(3520)+ c+K- + | p*( c+)>2. 5 Ge. V) ( c+ | p*( c+)>2. 5 Ge. V) <1. 5 10 -4 @ 90% CL y r a n i Prelim Ba. Bar observes NO SIGNAL ALSO in a similar decay mode (hep-ex/0605075) Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle 12 Charm 2006

Summary (1) NEW Isotriplet of Charmed Baryons is observed by Belle: (2) c(2800) (2) Belle measured with high accuracy the masses of 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 cx(3077)+ c+ K- + cx(2980)+ c+ K- + cx(3077)0 c+ KS 0 Studies of their properties are ongoing Ruslan Chistov (ITEP, Moscow) Charm Baryon Spectroscopy at Belle 13 Charm 2006