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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