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

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  • 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