1. c c c c c c c c c c a Charmed baryon spectroscopy at Belle
Y. Kato(KMI, Nagoya University)
Phys. Rev. D 89,
arXiv: c c
Introduction
Charmed strange baryons(Ξc) s s d a u c
Physics of charmed baryons
Ξc is a good probe to study u/d-s diquark system.
This correlation can be studied only in the charm sector
because in the strange sector, s quark is heavier
than u/d quarks and weak u-d diquark correlation emerges.
Charm quark is heavy (~1.5 GeV) compared with .....
Momentum of quarks inside the hadron (200 MeV)
→ Doubly charmed baryon is a good probe to study the
potential between heavy quarks. Similar to the study of QQbar potential
by charmonium spectroscopy.
2. Mass of u,d,s quarks ( MeV)
→ Singly charmed baryon is a good probe to study the
diquark correlation of light quarks. This is because
spin-spin interaction is proportional to 1/m1m2.
λmode s u
ρ mode
BaBar c c c c
Belle
Belle found Ξc(2980) and Ξc(3080)
in the Λc+K-π+ final state. Later,
BaBar studied the same final
state. They required Λc+π+ mass
to be Σc(*) and reported another
two resonances, Ξc(3055) and Ξc(3123)
Ξc(3080)
Σc(2520) d u
Σc(2455) c
Ξc(2980)
Ξc(2980)
Ξc(3080)
Ξc(3055)?
Require Σc(2455)
λ mode
Ξc(3123)?
Ξc(3080) q q
ρmode
Experimental situation
M(Λc+K-π+)
diquark
Require Σc(2520)
Re-analysis by Belle
M(Λc+K-π+)
・All the ground states of single charmed baryon has discovered
　mainly by e+e- collideer experiments like CLEO, BaBar, Belle.
・Many excited states has been also discovered.
・Almost no quantum numbers has been measured.
・No doubly charmed baryons including ground states.
Ξc(2980)+
Ξc(3080)+
Ξc(3080)+
Ξc(3055) is confirmed in Σc(2455) K-
while Ξc(3123) in Σc(2520) is not
confirmed. U.L of the cross section is
0.34 fb ⇔ (1.6±0.6±0.2)fb by BaBar.
Ξc(3055)+
spin=3/2
spin=1/2
charm
Further study with
ΛD final state
ΛD0
ΛD+
M(ΛD0)
D0 sideband
M(ΛD0bar)
M(ΛD+)
D+ sideband
M(ΛD-)
Ξc(3055)+
Ξc(3055)0
We observe Ξc(3055)/(3080) in the
ΛD final state. This is the first observation
of the Ξc(3055)0. As discussed later,
The relative branching fraction is sensitive
to the excitation modes (ρ,λ) c c
Ξc(3080)0
Search for doubly charmed baryons u
Experimental situation ？
The SELEX experiment in FNAL reported evidence of
Ξcc+ in the Λc+K-π final state at 3520 MeV. However, this
result was not supported by Belle, BaBar, Focus and LHCb.
To discover the ground state is a big milestone.
Discussion on the Ξc states
Comparison of Λc+ and Ξc, Σc and Ξc’
New analysis by Belle Jp
Λc+ (cud)
Ξc (cus)
ΔM(Mev/c2)
Note
1/2+
Λc(2286)+
Ξc(2470)
181
ground state
1/2-
Λc(2595)+
Ξc(2790)
194
Λ(1405) like
3/2-
Λc(2625)+
Ξc(2815)
188
Λ(1520) like ??
Λc(2765)+?
Ξc(2980)?
205
Isospin not determined
5/2+
Λc(2880)+
Ξc(3080)?
200
・Use full statistics (980fb-1) of Belle data.
=2 (4) times of previous Belle (BaBar) anslysis
・Study not only Λc+K-π+ final state but also Ξc0π+ decay mode
(Belle studied Λc+K-π+ only but BaBar studied both)
・Add several sub decay of Λc+ (pK-π+, pKS0)and Ξc0 (Ξ-π+, ΛK-π+, pK-K-π+)
→ yield is increased by 20% for Λc+ and 3 times for Ξc0
spin0
di-quark Jp Σc
Ξc’
ΔM(Mev/c2)
Note
1/2+
Σc(2455)
Ξc(2575)
120
ground state
3/2+
Σc(2520)
Ξc(2645)
125
Σ(1385) like ??
Σc(2800)
spin1
di-quark
Ξc0π+ mode
Λc+K-π+ mode
Ξc0→Ξ-π+
Ξc0→pK-K-π+
・Thee mass difference of Λc+ and Ξc is ~200 MeV, Σc and Ξc’ is ~120 MeV.
Λc+ with = 2855 MeV, or Σc with = 2935 MeV ?
Ξc(3055) is a pecial state by including strange quark??
Discussion from decay modes.
Data
Expectation of signal
(assuming σ=500fb, Br=5%)
Ξc0→ΛK-π+
Prediction from chiral quark model for relative branching fraction for Ξc(3055)
arXiv:
Lei-Hua Liu et al
No significant signal!
Close to the some of theoretical prediction.
Possible to access in the BelleⅡ?
Large branching fraction to ΛD is inconsistent
Ξc(3055)/(3080) can decay into
（heavy baryon+ light meson） and (light meson + heavy baryon) Σc Λ D K-
UL of σ(e+e-→ΞccX)×Br(Ξcc+→Ξc0π+)×Br(Ξc+→Ξ-π+)
σ(e+e-→ΞccX)×Br(Ξcc+→ΛcK-π+) c
Naively thinking…
λ mode→ (light baryon) + (heavy meson)
ρ mode→ (heavy baryon) + (light meson)
This study fb
Theory
3.5-10fb
(assuming Br=5%)
This study fb
Theory fb
(assuming Br=5%)
λ mode s u
Excitation of both λ and ρ mode?
Further theoretical study is necessary.
ρ mode