What is the charmed analog of (1405)?

Kiyoshi Tanida(Seoul National University)

Aug. 23, 2011APFB2011, Seoul

Λ （ 1405 ）

How is it in charmed sector?

• Large mass difference of πΣ and DN→ mixing should be small

• Both of Σπ resonance and ND bound state can be seen as separate peaks?

strange charmMΛ 1116 2286

MΣ 1190 2455

MK （ M

D ）495 1872

Σπ 1330 2595NK （ ND ）

1435 2810

MΛ* 1405 ？

Σcπ resonance?

• Just on Σcπ threshold

• Still, the main decay mode is Σcπ

Is there DN bound state?

• JP are unknown, but they may be the bound state.Binding energies: 45MeV & 10MeV, respectively

• In the strangeness sector, attraction for I=0 channel is stronger than I=1.

Λc （ 2765 ）

PRL86 （ 2001 ） 4479data from CLEO

B decay →Λc*→Λcππ（ Σcπ 、 Σc*π included ）

Width ～ 50 MeV

Λc （ 2765 ）

Λc （ 2880 ）

CLEO data

Λc （ 2880 ） Σcπ

BR=31±7%

Rough estimation in similar way:Λc （ 2765 ） Σcπ ～ 26%Λc （ 2765 ） Σc*π

～ 33%

via Σcπ

via Σc*π

Λc （ 2880 ）Λc （ 2765 ）

BELLE data

PRL98 (2007) 262001

This paper’s main subject is Λc(2880), but Λ(2765) was clearly seen, too.

Black: via Σcπ

Red ： sideband background　　 （ scaled ）

Width ： 73±5 MeV(Not used in PDG)

Σcπ partial decay rate?• Λc(2595):

– Full width=3.6+2.0-1.3 MeV– BR(Σcπ) > 70%. Partial width ~ 2.5 MeV

• Λc(2765):– Rough estimation: Γ(Σcπ) ～ 30MeV

• Dividing by phase space ・・・– Λc(2595): Q-value too small

Σc++π-: 1.7±0.6 MeV 、 Σc

+π0: 7.4±0.7 MeV

Q may be < 0 （ Threshold effect on spectrum ）→ Unmeasured Σc

+π0 mode would be the main channel

– Squared matrix element may be twice larger for Λc(2595)

Q-value 1 MeV 3 MeV 5 MeV 172 MeV

Phase space （ relative ）

1 1.8 2.3 37

Λc(2595) shape• CLEO data fit with threshold effect considered. (PRD67 074033)

M(Λc*) M(Λc) = 305.6±0.3 MeV ~3 MeV below c

Known things• Λ(1405) analog states– Σπ resonance certainly exists.– DN bound state: candidate exists.

• Comparing partial decay rates, it seems Λc(2595) has a stronger coupling to Σcπ

• Λc(2765) has too many unknowns, and the quality of data Λc(2595) is not enough.

What we want to know• Is Λc(2765) really the ND bound state and can be

considered as a Λ(1405) analog state?• Key measurements– Spin-parity: Many controversial predictions– Decay width, branching ratios

• Λc(2595) needs more data, too.– Need to consider threshold effect. Σc

+π0 mode would be a key.

• Need help from theory side– Threshold effect for Λc(2595)

– Discussion from partial widths– Determination of parity (which was the case for Λc(2880))

BELLE data

PRL98 (2007) 262001

This paper’s main subject is Λc(2880), but Λ(2765) was clearly seen, too.

Black: via Σcπ

Red ： sideband background　　 （ scaled ）

Width ： 73±5 MeV (Not used in PDG)

Possibility at BELLE• Decay widths seem feasible– Is Λc(2595)→Σc

+π0 possible?

• Determination of spin– angular distribution of

Λc→Σcπ

– Done for Λc(2880)

• Parity– Most difficult– Λc(2880) parity was

determined from BR ofΣcπ and Σc*π using model (heavy quarksymmetry)

Summary• Charmed analog of Λ(1405)– Σπ resonance ： Λc(2595)

– DN bound state: Λc(2765)?

• We want to know the nature of Λc(2765)– Spin-parity (1/2?)– Decay width measurements would help, too.

• B-factory data contains huge statistics→ analysis seems feasible