Charmed Baryons

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Charmed Baryons. Charmed Baryons. Hai-Yang Cheng Academia Sinica, Taipei Spectroscopy Strong & EM decays. Charm 2007, Cornell, August 5-8, 2007. Spectroscopy. In SU(3) representation, diquark = 3  3 = 3 +6 - PowerPoint PPT Presentation

Text of Charmed Baryons

  • Charmed Baryons Charmed Baryons Hai-Yang Cheng

    Academia Sinica, Taipei

    SpectroscopyStrong & EM decays Charm 2007, Cornell, August 5-8, 2007

  • SpectroscopyMany new resonances observed: Ground state: c*(2770) with mass = 2768.33.0 MeV (BaBar) Orbitally excited p-wave states: L=1 e.g. c(2593), c(2625), etc. (CLEO) Positive parity excitations: L=2,1,0 e.g. JP[c(2880)]=5/2+ (Belle)In SU(3) representation, diquark = 33 = 3+63: c+,c+,c0, all decay weakly6: c0,+c,0c,c++,+,0 only c0 decays weakly c*0,*+c,*0c,c*++,+,0 S=0 S=1

  • Orbitally excited charmed baryon statesL+L=Ll (not L+L=L !) Two possible p-wave states (L+L=1): L=1, L=0; antisymmetric under q1q2L=0, L=1; symmetric under q1q2

    Jl=Sl+Ll, J=Sc+Jlsymmetric

    antisymmetric(denoted by a tilde)In HQ limit, Jl & Sc are separately conserved

  • First positive parity excitations (L+L=2):L=2, L=0; L=0, L=2 symmetric under q1q2; Ll=2L=L=1 antisymmetric under q1q2; Ll=2,1,0

  • ---3/2-3/2-Only the parity of c & c(2880) has been measured3/2-3/2-3/2-3/2-

  • c(2595), c(2625) c1(1/2-,3/2-) c1(1/2-)![c]S, c1(3/2-)![c]P, [c]D c(2625) is narrower than c(2595)c0[c]S, c1[c]P, c2[c]D Since c(2880) observed in c spectrum has a width 65 MeV, and (c0c) 405 MeV from HHChPT c(2880) is most likely to be a c2(3/2-) c(2800): c2(3/2-), c1(3/2-), c0(1/2-)Antitriplet charmed baryons:+ (c, c+, c0)- (c(2595)+, c(2790)+, c(2790)0)3/2- (c(2625)+, c(2815)+, c(2815)0) c(2790), c(2815) c1(1/2-,3/2-)

  • c(2880): first positive parity excited charmed baryonCandidates for spin-5/2 states: parity assignment for c(2880)Angular analysis of c(2880) c by Belle J=5/2 is preferred JP=5/2- isdisfavored However, c2(5/2+) can decay into c* in a P-wave robust prediction c(2880) could be an admixture of HQS Chua,HYC (07)

  • Remarks: Based on the diquark idea, JP[c(2880)]=5/2+ has been predicted by Wilczek and Selem before Belle experiment Peking group (Zhu et al., hep-ph/0704.0075) has studied the strong decays of charmed baryons using 3P0 model Since c(2880) decays into D0p, it cannot be a radial excitation c(2880) is a pure state c2(5/2+) leads to too large ratio of c*/c for L=0, L=2, and too large width ( 78 MeV) for L=2, L=0An issue about mass: According to QM, m[c2(5/2+)] 2910MeV,The mass of is even higher

  • Other even-parity excitated states ? c(2765): even-parity orbital excitation +, supported by QM (Capstick, Isgur 86) & Skyrme model (Oh & Park 96) radial excitation 2+ (Ebert, Faustov, Galkin 07) c(2940): 3/2+, 5/2-, can be tested by measuring the ratio c*/c m(D*0)+m(p)=2945 MeV a D*0p molecular - state for c(2940) with binding energy 5 MeV ? (X.G. He et al.) first radial excitation of c with JP=3/2+ (Ebert et al.)M(c)-M(c) 180200 MeV for JP= +, -,3/2- c(2980) & c(3077) considered as counterparts of c(2765) & c(2880) c(2980): +, or 2+ c(3077): 5/2+, c(3055): ? c(3123): ?c(2980) is broader than c(3077); both are above D thresholdor c(2765)

  • +,2+ 3/2+,5/2-5/2+5/2++,2+ +,2+

  • 5/2+3/2-3/2+1/2+c c c c1/2+5/2+

  • An ideal place for testing heavy quark symmetry and chiral symmetry: heavy hadron chiral perturbation theory (HHChPT)Strong decays of s-wave charmed baryons are governed by two couplings g1 & g2. While info on g1 is absent due to the lack of c*c, g2 is fixed to be 0.610.04 by the measured rate of c++c++ (in units of MeV)Wise; Yan et al.; Burdman, Donoghue (92) (c*) 7(c), though they have same widths in HQ limit

  • S-wave (D-wave) transitions between s-wave and p-wave baryons are described by six couplings h2,,h7 (eight couplings h8,,h15) Pirjol, Yan (97)h2h10h10 & h8=h10Chau, HYC

  • Strong decays of p-wave charmed baryons isospin violation: c+0 2 c0+ , c00 c+- as 0 is lighter than Strong decays of c(2593) are near threshold sensitive to masses (c0(1/2-)c) 405 MeV

  • Electromagnetic decays suitable framework: HHChPT+ QM (Yan et al. 94)(in units of keV)It will be very difficult to measure EM decay rates

  • Other topics: Hadronic weak decays of c+,c+,c0,c0 Charm-flavor-conserving weak decays Lifetime differences Semileptonic decays Weak radiative decays discussed in back-up slides See review article on charmed baryons in Tau-Charm Physics Book at BESIII. Hope it will be posted on archive soon

  • Conclusions HQS & S can be nicely tested in charmed baryon sector. Strong couplings g2, h2 & h10 are updated Many orbitally excited charmed baryons have been observed Some form multiplets c(2880) is a first even-parity excited state. It could an admixture of We need more strong decay measurements to pin down spin- parity assignment

  • Back-up Slides

  • Lifetimes10-15sheavy quark expansion:Pauli interference & W-exchange are 1/mc3 corrections, enhanced by p.s. enhancement factor of 162c decayW-exchangedestructive P.I.constructive P.I.

    c+ 44226c+ 2006c0 112+13-10c0 6912

    D+ 10407Ds+ 5007D0 410.11.5

  • s=sinC, c=cosC Lifetime hierarchy (c+)>(c+)>(c0)>(c0) is qualitatively understandable, but not quantitatively. It has been claimed that lifetimes can be accommodated (except c+) provided that hybrid renormalization is employed and replacement of fD by FD is made (Shifman, Blok, Guberina, Bigi..) It is difficult to explain (c+)/(c+)=2.210.15 1/mc expansion is not well convergent and sensible

    DecAnnInt(-) Int(+)Semi-inclusive (10-13s) Exptc+1s21c2small P.I. 3.684.420.26c+1c21s2 2.642.000.06c01111small P.I. 1.931.12+0.13-0.10c016s210/3c2large P.I. 1.710.690.12

  • Hadronic weak decaysComplications: Baryons are made of three quarks Factorization approximation generally doesnt work W-exchange is not subject to helicity & color suppression Current algebra is no longer applicable as the outgoing meson is far from being soft. Also this soft-meson technique is not applicable to vector meson production

  • Hadronic weak decays Diagrammatic scheme (Chau, HYC, Tseng 96) Two distinct internal W emission diagrams, three different W exchange diagrams Need information of decay asymmetry to extract s-wave and p-wave amplitudes separately

  • Dynamical model calculation pole model: Consider low-lying pole contributions: s-wave is governed by - resonances p-wave is dominated by + ground-state baryonsRelativistic QM: Korner, Kramer, Ivanov,

  • BRs of Cabibbo-allowed decays W-exchange plays an essential role

  • Decay asymmetry for Cabibbo-allowed decays?? Longitudinal pol. of daughter baryon from unpol. parent baryon information on the relative sign between s- and p-waves

  • Decay modes that proceed through factorizable diagrams c+ p |a2|=0.600.10, close to c2 1/Nc is also applicable to charmed baryon sector c0-+ a1 c0*0K0 a2

  • Charm-flavor-conserving weak decays: Light quarks undergo weak transitions, while c quark behaves as a spectator e.g. cc, ccBr(c0c+-) = 2.9 10-4Br(c+c+0) = 6.7 10-4Br(c0+c-)= 4.5 10-6should be readily accessible soon

  • Semileptonic decays Semileptonic rate depends on BcB form factors| NRQM |RQMLFQMQSR QSRin units of 1010s-1Six form factors are reduced to two in mQ limit

  • Weak radiative decays Charm-flavor-changingc++, c00 Charm-flavor-conservingcc, cci) e.m. penguin cuii) emission from external quark in W-exchange emission from W boson in W-exchange