Charmed baryon decays at Belle - .Charmed baryon production at Belle 2 2017/11/8 2 ・ +Charmed baryons

1

2017/11/8 1

Charmed baryon decays at Belle Yuji Kato (KMI, Nagoya University)

c* D

Doubly Cabibbo Suppressed decay c

+pK+-

Hidden Strange pentaquark via c

+ 0 p decay

2 Charmed baryon production at Belle

2017/11/8 2

Charmed baryons are produced mainly via e+e-*cc Total integrated luminosity ~=1.0 ab-1. ~1.0109 e+e- cc. Many charmed baryons are discovered by Belle and BaBar so far. ( c(2940), c(2800), c(2980), c(3055), c(3080), c(2770) )

e-

e+

c

c *

Charmed strange baryons (c) 3

u S

C

u/d-s diquark system!

c(1/2+)

c(1/2+)

c(2645) (3/2+)

2.5

2.6

2.7

2.8

2.9

3.0

3.1

3.2

c(2790) c(2815)

c(2980)

c(3080) c(3055)

c(3123)? c

(1/2-) (3/2-)

u-s di-quark, which can not be achieved in the state. The states below c(2815) are well descrived by the quark model. Higher excited states contains rich dynamical information!

4 Higher excited c states in c++K- (past studies)

Both Belle and BaBar observed c(2980)

+, c(3055)+, and c(3080)

+ in c++K- final state.

c(3080)+ in c

*++K- final state (only BaBar observed c(3123)+)

Decays where charm quark in contained in meson will give more insight D!

M(c++K-)

Phys. Rev. D 89, 052003

Phys. Rev. D 77, 012002

M(c*++K-)

c(2980) c(3055)

c(3080)

c(3080) c(3123)

M(c++K-)

M(c*++K-)

2017/11/8 4

M(D) 5 c(3055)

+

c(3080)+

First observation of the decay of c(3055/3080) into D+.

N(c(3055)+) > N(c(3080)

+): Opposite to c++K-.

First observation of c(3055)0 (8.6)

M(D+)

D0K-++- D0K-+ D0K-+0

M(D0)

Phys. Rev. D 94, 032002

c(3055)0

c(3080)0

6 Relative branching fractions

6

c(3055)+

Br(D+)/Br(c++K-) = 5.091.010.76

c(3080)

+

Br(D+)/Br(c++K-) = 1.290.300.15

Br(c*++K-)/Br(c

++K-) = 1.070.270.01

Prefer D

Similar in 3 decays

Phys. Rev. D 94, 032002

2017/11/8

First ever measurement of relative branching fraction of (heavy-baryon + light-meson) and (light-baryon + heavy-meson).

Partial width of c(3055) by chiral quark model (MeV)

Phys. Rev. D 86, 034024

Inconsistent with our measurement!

7 Doubly Cabibbo Suppressed decay: c+pK+-

2017/11/8 7

In the baryon sector, Doubly Cabbibo Suppressed (DCS) decay had never been observed. c

+pK+- is expected to be sensitive. Naively, ratio to CF decay, pK-+ is expected to be W-exchange diagram can contribute only in CF decay.

c

c

c

pKB

pKB

4tan)(

)(

CF decays DCS decays

8 Results

Branching fraction ratio = ( 2.350.27(Stat)0.21(Sys) ) 10 -3 = (0.820.12)tan4c

After subtracting contribution of (1520) or intermediate, which contribute only on the CF decay, the ratio is (1.100.17)tan4

Contribution from W exchange diagram is not large. 8

DCS mode: pK+- CF mode: pK-+

(1.4520.015)106 events 3587380 events Significance: 9

Phys. Rev. Lett. 117, 011801

9 Search for pentaquark via c+0p

2017/11/8 9

LHCb observed hidden charm pentaquark state in the b

0 K- Pc+ K- (J/ p)

Natural extension is analogue search for hidden-strange pentaquark by switching b->c (b

0 c+), c->s (J/ -> )

:c+ 0 Ps

+ 0 ( p) c

+0p decay itself is not observed so far.

10 Results

2017/11/8 10

M(K+K-p0) M(K+K-)

Perform 2D fit on M(K+K-p0) and M(K+K-) plane. No significant c

+ signals is observed. New upper limits: - Br (c

+ p 0) < 15.3x10-5

- Br (c+K+K-p0 )NR < 6.3x10

-5 Also perform 2D fit in each M(p) bin. No significant Ps

+ signal observed. - Br(c

+Ps+0)xBr(Ps

+p) < 8.310-5

M(p)

Phys. Rev. D 96, 051102(R)

11 Summary

2017/11/8 11

First observation of the decay c(3055) and c (3080) D - Br(D)/Br(c

++K-) are different for two states. - First observation of c(3055)

0

First observation of Doubly Cabibbo Suppressed decay: c

+pK+-

- The ratio to CF decay can be explained by CKM suppression. Contribution from W-exchange diagram is small. Search for hidden strange pentaquark Ps

+ in c+ 0 ( p)

- No signal for Ps+ as well as the decay c

+ 0 ( p) Stay tune for more results on charmed baryon from Belle!

12 Backup

2017/11/8 12

13 Physics of single charmed baryons

Charm quark is heavy: (1500 MeV/c2) > u,d,s quarks (300-500 MeV/c2) spin-spin interaction1/m1m2 Di-quark correlation in light quarks (more simple!).

13

Nucleon Charmed baryon

Every pair can not be distinguished. Light di-quark and charm quark.

2017/11/8

c+ (1/2+)

c(2595)+ 1/2-

c(2625)+ (3/2-)

[c(2765)+ ?? ]

c(2880)+ 5/2+

c(2940)+ ??

c(2455) (1/2+)

c(2520) (3/2+)

c(2800) ??

c (1/2+)

c (1/2+)

c(2645) (3/2+)

c(2790) (1/2-)

c(2815) (3/2-)

[c(2930) ??]

c(2980) ??

c(3055) ??

c(3080) ??

[c(3123) ??]

c (1/2+)

c(2770)(3/2+)

CLEO 8(7) (19952001) BELLE 3 (2006) BABAR 5(2) (2007)

Observed charmed baryons

14

c s u

c s s c

d u

d u c

2017/11/8

16/21 (12/17) charmed baryons are observed in e+e- collider experiment. All the ground states predicted by quark model are discovered.

Still many things to do! Spin-parity almost from quark model prediction (). Some states has only poor evidence (states in []). Many states are observed in only 1 decay mode. Accuracy of mass/width is not good enough. No and mode excitation states identified.

14

Todays topic

15 Belle experiment

2017/11/8 15

Mt. Tsukuba

8 GeV e- 3.5 GeV e+

Linac

~1 km

e- e+ bb

8 GeV 3.5 GeV

(4S)

B

B

Asymmetric energy e+e- collider. s=10.58 GeV = (4S) mass (and other energies) Peak luminosity = 2.11034 cm-2s-1 = World highest luminosity! General purpose feature of the Belle detector make it possible to study hadron spectroscopy.

16 Comparison with quark model prediction

2017/11/8 16

They predicted - D decay is suppressed for both c(3055)

+ Inconsistent with this measurement. Challenge for theorists!

In the quark model, they should be N=2 shell and these states are identified as: c(3055) =

2D(3/2+) or 2D(3/2

+). (Phys. Rev. D 86, 034024)

Partial width (MeV)

Jp c+ c M(Mev/c

2) Note

1/2+ c(2286)+ c(2470) 181 ground state

1/2- c(2595)+ c(2790) 194 (1405) like

3/2- c(2625)+ c(2815) 188 (1520) like

?? c(2765)+? c(2980)? 205 Isospin not

determined

5/2+ c(2880)+ c(3080)? 200

Comparison of c+ and c or c and c

c(3055) has no corresponding state in c/c

The mass difference of c and c is ~200 MeV/c2, c and c is ~120 MeV

Jp c c M(Mev/c2) Note

1/2+ c(2455) c(2575) 120 ground state

3/2+ c(2520) c(2645) 125 (1385) like

?? c(2800) ??

spin0 di-quark

spin1 di-quark

17 2017/11/8

17

18 DCS decay of the c+

u d c

W+

In the baryon sector, Doubly Cabbibo Suppressed (DCS) decay has NEVER been observed. c

+pK+- is expected to be sensitive. Naively, ratio to CF decay, pK-+ is expected to be In the CF decay, the W exchange diagram may contribute.

c

c

c

pKB

pKB

4tan)(

)(

u d c

W+

DCS decay CF decay with W exchange

2017/11/8 18

19

19

Dalitz plot for c+pK-+ Phys. Rev. Lett. 117, 011801

(1520)

K*

??

??

Weak decay of charmed baryon is unique light baryon laboratory 2017/11/8