Contents 2 Overview of hadron spectroscopy at Belle
Contents 2 ・Overview of hadron spectroscopy at Belle. ・Review on X(3872). ・Recent results on charmed baryons (Ξc). ・Belle II ELPH研究会 2
Introduction 3 Success of constituent quark model Mesons Int. J. Mod. Phys. A, 21, 5583 (2006) Phys. Rev. D 18 (1978) 4187 Baryons ”Constituent quark” must be a good approximation. But. . ・Why it works so well? ・What is adaptive limit (exotic hadrons)? ・Any alternative degree of freedom (di-quark)? e+e- collider (especially B-factory) is a powerful probe! ELPH研究会 3
Belle experiment B e- ・Asymmetric energy e+e- collider. Υ(4 S) 8 Ge. V bb 4 e+ 3. 5 Ge. V ・√s=10. 58 Ge. V = Υ(4 S) mass (and other energies) ・Peak luminosity = 2. 1× 1034 cm-2 s-1 = World highest luminosity! ・General purpose feature of the Belle detector make it possible to study hadron spectroscopy. B Mt. Tsukuba 8 Ge. V e 3. 5 Ge. V e+ ~1 km Linac ELPH研究会 4
Hadron production at B-factory b B- Wu c c s K u B-meson decay ・Clean “charmonium laboratory”. ・X(3872), Z(4430)…. e- γ e+ Initial state radiation ・JPC=1– (same as photon) ・Y(4260) 5 e- c e+e-→ cc reaction ・Charmed baryons. ・ 2 -photon collision and double charmonium production also exist. ・Low multiplicity is an advantage compared with LHC experiment. ・Cross section lower than LHC but high luminosity compensate it. ELPH研究会 5
Data accumulated at Belle (and Ba. Bar) 6 Υ(5 S) ・ 10 years operation. Taken at various energies. ・~70 % of data is taken at Υ(4 S). ~7. 7× 108 BB pairs. ・Total inregrated luminosity ~=1000 fb-1. ~1× 109 e+e- → cc. ELPH研究会 6
“New hadrons” from B-factories Reaction Unexpected bonus of B-factories! Charmonium (like) D(s) B-decay ηc(2 S) X(3872) Zc(4050) Zc(4250) Zc(4430) Zc(4200) D 1(2430) Ds(2700) ISR Y(4260) Z(3900) Y(4008) Y(4660) Double charmonium X(3940) X(4160) Two photon χc 2(2 P) e+e-→ccbar Charmed baryon Bottomonium Ds 0(2317) Σc(2800) Λc(2940)+ Ξc(2980) Ξc(3080) Ωc(2770) Ξc(3055) Y(5 S) decay *some states may be missed Hadron type 7 Belle Ba. Bar Zb(10610) Zb(10650) hb(1 P) hb(2 P) ηb(2 S) ELPH研究会 7
X(3872) 8 @Virginia ELPH研究会 8
X(3872): First observation B- →K- J/ψπ+π- B- X K- J/ψ π- π+ M(ππJ/ψ)-M(J/ψ) ψ(2 S) X(3872) 152 M BBbar pairs zoom d Phys. Rev. Lett. 91. 262001 ELPH研究会 The most cited among ~450 papers in Belle (>1225@INSPIRE) 9
Confirmed by many experiments 10 Phys. Rev. Lett. 93: 072001, 2004 Eur. Phys. J. C. 72 (2012) 1972 Phys. Rev. Lett. 93, 162002 JHEP 04 (2013) 154 ・Existence is established. ELPH研究会 ・Understanding of the nature. Phys. Rev. D 71: 071103, 2005
A strange hadron: X(3872) 11 ・No quark model prediction in such mass region - Mass of the χc 1(2 P) is the closest but 30 Me. V higher. Phys. Rev. Lett. 91. 262001 ・Decay breaks Isospin -J/ψππ = J/ψρ. ccbar is I=0 ρ: I=1 -J/ψ3π = J/ψω is observed ω: I=0 ・Very narrow width though above DD threshold -Upper limit on the width =1. 2 Me. V. -Ex: Width of ψ(3770) is 27 Me. V ・Very close to the D 0 D*0 3871. 69± 0. 17 Me. V/c 2⇔ 3871. 80± 0. 12 Me. V/c 2 M(X 3872) MDD* ELPH研究会 M(ππ) c c c u u c D 0
DD* Molecular state?(1) 12 The most natural interpretation is DD* molecular state c c * D u D π u D*: JP=1 D : JP=0 - ・Narrow width →DD* has JP=1+, whereas DD has JP=0+ π exchange is forbidden for DD but allowed for DD* D π π D D Spin-parity not conserved ELPH研究会 L=1 D* Spin-parity can be conserved with orbital angular momentum.
Molecular state? (isospin breaking) 0 D c u c π u D*0 D+ c 13 c D* d π d I=0 Eigen state is ・The mass difference of D 0 D*0 and D+D*- is around 8 Me. V (Mu<Md) ・This mass difference is large compared with binding energy. (~0. 1 Me. V) →The contribution of D 0 D*0 becomes large and Isospin 0 and 1 Phys. Lett. B 590 (2004) 209 -215 are mixed. ++ if it is a molecular state. The JPC of the X(3872) should be 1 ELPH研究会
Determination of C-parity: J/ψγ B+→K+J/ψγ 14 B 0→KSJ/ψγ J/ψ: C=-1 γ: C=-1 C=+1 ELPH研究会 Phys. Rev. Lett. 107: 9, 2011
Spin-parity determination. 15 -2 ln[L(2 -+)/L(1++)] Phys. Rev. Lett. 110, 222001 (2013) The estimated likelihood ratio for JPC=2 -+ and 1++. Compare with observed likelihood. →Favor 1++ by 8. 2σ=Consistent with S-wave DD* ELPH研究会
Pure molecular state? Phys. Rev. Lett. 93: 072001, 2004 16 pp 1. 9 Te. V ・ 80% comes from ”prompt production” (not from B decay). ・If X(3872) is pure molecular state, binding energy is small. →Size is large: Radius is ~8 fm →Easy to be broken. →Prompt production cross section should be small. Measurement : 3. 1± 0. 7 nb ⇔Prediction: 0. 071 -0. 11 nb 0 D c u c D*0 and C C π u χc 1(2 P) ELPH研究会 Phys. Rev. Lett. 103: 162001, 2009 Hybrid?
Absolute branching fraction 17 ・In order to explore the nature of X(3872), we need to investigate many decays and productions (like Tevatron). ・B→K+X(3872) provides another information. ・Currently, only the product: Br(B+→K+X(3872))×Br(X(3872)→J/ψπ+π-) is measured. B- X K- J/ψ π- π+ ELPH研究会 Br(B+→K+X(3872)) = (2. 68± 0. 5)× 10 -5 : Pure molecular (0. 38± 0. 06)× 10 -5 : Pure charemonium (1. 0± 0. 68)× 10 -5 : Mixing angle 5 -13° PRB, Volume 702, Issue 5, Pages 359– 363
Absolute branching fraction (2) ・It is necessary to identify the X(3872) without relying on decay ・In the B-factory, we have only two B mesons in the final state. ・Impossible at LHCb ELPH研究会 18
Physics of single charmed baryons 19 ・Charm quark is heavy (1500 Me. V/c 2) > u, d, s quarks (300 -500 Me. V/c 2) ・spin-spin interaction∝ 1/m 1 m 2 ・Di-quark correlation in light quarks (more simple!). Nucleon Every pair can not be distinguished. Charmed baryon Light di-quark and charm quark. ELPH研究会 19
Excitation modes in the charmed baryons 20 ・There are two kind of excitation modes. Both states have JP=1/2 - λ mode: excitation between c quark and u-d di-quark. - ρ mode: excitation in the di-quarks. T. Yoshida et al. PRD 92, 114029 (2015) ½- λ mode The fraction of λ mode for the 1 st excited state. ρ mode
Observed charmed baryons Λc+ (1/2+) Λc(2595)+ 1/2Λc(2625)+ (3/2 -) [Λc(2765)+ ? ? ] Λc(2880)+ 5/2+ Λc(2940)+ ? ? Σc(2455) (1/2+) Σc(2520) (3/2+) Σc(2800) ? ? c d u CLEO 8(7) (1995~ 2001) BELLE 3 (2006~) BABAR 5(2) (2007~) c d u 21 Ξc (1/2+) Ωc (1/2+) Ξ’c (1/2+) Ξc(2645) (3/2+) Ξc(2790) (1/2 -) Ξc(2815) (3/2 -) [Ξc(2930) ? ? ] Ξc(2980) ? ? [Ξc(3055) ? ? ] Ξc(3080) ? ? [Ξc(3123) ? ? ] Ωc(2770)(3/2+) c s s c s u ・ 16/21 (12/17) charmed baryons are observed in e+e- collider experiment. ・All the ground states predicted by quark model have been discovered. ・Spin-parity almost from quark model prediction (). ELPH研究会 21
Current situation. 22 ・ The diquark picture has NOT been established. ・ Experimentally, we need to. . - Discover more charmed baryons - Determine spin and parity - Determine mass and width precisely - Study the decay pattern - Study the production mechanism → Compare global consistency with diquark picture. ELPH研究会 22
Charmed strange baryons (Ξc) C Ξc λ mode u ρ mode S u/d-s diquark system! ・u-s di-quark, which can not be realized in the Λ or Ξ. ・Relatively light excited states are well described by quark mode. ・Many higher states observed but nature not understood yet. 23 3. 2 Ξc(3123)? Ξc(3080) Ξc(3055) Ξc(2980) 3. 1 3. 0 2. 9 2. 8 Λ(1520) like Λ(1405) like Ξc(2815) (3/2 -) Ξc(2790) (1/2 -) Σ(1385) like Ξc(2645) (3/2+) Σ(1192) like Ξc’(1/2+) 2. 7 2. 6 2. 5 Λ(1116) like Ξc(1/2+)
Higher excited states in ∑c++K- (past studies) 24 Phys. Rev. D 77, 012002 Phys. Rev. D 89, 052003 M(∑c++K-) Ξc(2980) Ξc(3055) Ξc(3080) M(∑c*++K-) M(∑c++K-) Ξc(3123) M(∑c*++K-) ・Both Belle and Ba. Bar observed Ξc(2980)+, Ξc(3055)+, and Ξc(3080)+ in ∑c++K- final state. Ξc(3080)+ in ∑c*++K- final state (only Ba. Bar observed Ξc(3123)+) ELPH研究会 24
Decay pattern? c λ mode: u s/d 25 Naively, λ mode excitation decays to light baryon + heavy meson ρ mode excitation decays to heavy baryon + light meson ρ mode ・All the excited Ξc are observed in (heavy baryon) + (light meson) final states. (Light baryon) + (heavy meson) decay provides complementary information → ELPH研究会 ΛD! 25
M(ΛD+) distribution Phys. Rev. D 94, 032002 M(ΛD+) Ξc (3055)+ (11. 7σ) Ξc(3080)+ (4. 8σ) M(∑c++K-) (The same as previous) Ξc(2980) Ξc(3055) ・First observation of decay of Ξc(3055/3080) into ΛD+ ・Ξc(3055)+ yield is larger than that in Ξc(3080)+ (opposite to Σc. K) 26
Combine ΛD and ∑c(*) modes ar. Xiv: 1605. 09103 27 ・Branching fraction ratios: - Ξc(3055)+ Prefer ΛD Br(ΛD+)/Br(Σc++K-) = 5. 09± 1. 01± 0. 76 Similar in 3 decays - Ξc(3080)+ Br(ΛD+)/Br(Σ ++K-) = 1. 29± 0. 30± 0. 15 c Br(Σc*++K-)/Br(Σc++K-) = 1. 07± 0. 27± 0. 01 ・First ever measurement of branching ratio for (heavy-baryon + light-meson) and (light-baryon + heavy-meson). ・Br(Σc*++K-)/Br(Σc++K-) is sensitive to the Jp of Ξc(3080)+ ELPH研究会 27
Comparison with chiral quark model 28 Partial width (Me. V) In the chiral quark model, Ξc(3055) = 2 Dλλ(3/2+) Ξc(3080) = 2 Dρρ(3/2+). (Phys. Rev. D 86, 034024) ・ Predicted large width in Σc. K but small width in ΛD ・ Inconsistent with this measurement. → Challenge for theorist! ELPH研究会 28
M(ΛD 0) distribution Ξc(3055)0 Ξc D 0→K-π+ (3080)0 Ξc(3055)0 29 D 0→K-π+π+πΞc(3080)0 Ξc(3055)0 D 0→K-π+π0 Ξc(3080)0 ・Simultaneous fit by fixing relative yield from efficiency and branching fractions ・First observation of Ξc(3055)0 (8. 6σ)! M(Ξc(3055)0) = 3059. 0± 0. 5± 0. 6 Me. V/c 2 Γ(Ξc(3055)0) = 6. 4± 2. 1± 1. 1 Me. V ΔM=M(Ξc(3055)+)-M(Ξc(3055)0) = -3. 2± 0. 9 Me. V/c 2 ELPH研究会 29
Isospin splitting for light Ξc Phys. Rev. D 94, 052011 M(Ξc+) - M(Ξc 0) (Me. V/c 2) 3/2+ 1/2+ Ξc(2645) Ξc ’ 1/2 - 3/2Ξc(2815) Ξc(2790) Ξc(2980) ・Isospin splitting can be measured with accuracy of ~0. 5 Me. V. ・M(d)>M(u) -> M(Ξc 0)>M(Ξc+) ・Repulsive Coulomb potential → M(Ξc+)>M(Ξc 0) ・p-wave baryons has large splitting as Coulomb potential become weak. ・Can we say anything on large splitting for Ξc(2980)? 30
Belle→Belle II 31 Aim to find physics beyond the Standard Model ・ 40 times peak luminosity. ・ 50 times integrated luminosity. ・Physics run w/o vertex detector in 2018 ELPH研究会 ・More exotic states like Tcc ・Doubly charmed baryons ・Spin-parity of charmed baryons ・Doubly charmed baryons 31
Summary 32 ・Belle is one of the hottest place for the hadron spectroscopy. ・X(3872) is extensively studied. - Admixture of χc 1(2 P) and DD* molecule is most plausible. - Interested in the absolute branching fractions ・Many results from charmed baryons. - Di-quark picture is expected but not established. - Basically experiment driven. More input from theory is important - Spin-parity determination and possibly new excited states by Belle II ELPH研究会
Backup ELPH研究会 33
Comparison of Λc+ and Ξc or Σc and Ξc’ Jp Λ c+ Ξc ΔM(Mev/c 2) Note 1/2+ Λc(2286)+ Ξc(2470) 181 ground state 1/2 - Λc(2595)+ Ξc(2790) 194 Λ(1405) like 3/2 - Λc(2625)+ Ξc(2815) 188 Λ(1520) like ? ? Λc(2765)+? Ξc(2980)? 205 Isospin not determined 5/2+ Λc(2880)+ Ξc(3080)? 200 Jp Σc Ξc ’ ΔM(Mev/c 2) Note 1/2+ Σc(2455) Ξc(2575) 120 ground state 3/2+ Σc(2520) Ξc(2645) 125 Σ(1385) like ? ? Σc(2800) ? ? spin 0 di-quark spin 1 di-quark ・The mass difference of Λc and Ξc is ~200 Me. V/c 2, Σc and Ξc’ is ~120 Me. V Ξc(3055) has no corresponding states in Λc/Σc ELPH研究会 34
Corresponding state just not found? LEP s=92 Ge. V ARGUS s=10. 5 Ge. V J: spin p Λ Σ eye guide Δ ΞΣ*+- Λ(1520) Ξ* Ω - Production rate of hadrons in e+e- collision is known to lie on the exponential curve. If corresponding state in Λc or Σc exists, ELPH研究会 experimentally much easier to find. 35
Doubly charmed baryons at Belle c→s Ξcc+ M(Ξc 0π+) Ξc 0 + π c→s Ξ- s→u π+ Λ π 36 s→u p π ・Belle searched for Ξcc in the Ξc 0π+ and Λc+K-π+ decay modes. ・No significant signals were observed. ・Upper limit on the production cross section is close to theoretical predictions. ・Good subject in the Belle II. Phys. Rev. D 89, 052003
X(3872)→ψ’γ 37 Predicted to be small for pure molecular. Large for charmonium state. Phys. Rev. Lett. 102: 132001, 2009 Phys. Rev. Lett. 107: 9, 2011 R=2. 46± 0. 64± 0. 29 Probably not a pure charmonium. But a large uncertainty on theoretical predictions. Nucl. Phys. B 886 (2014) 665 -680 ELPH研究会
Other experiments ・ ・ pp 1. 9 Te. V ・ ・ pp 7, 8 Te. V e+e- ~4 Ge. V 38 ・e e 10. 58 Ge. V + - e+e- 10. 58 Ge. V ・Collider experiment ・General purpose detector ELPH研究会 38
+ Z(4430) 39 ・X(3872) is interesting! However, interpretation is difficult. As the charge is zero, mixing with ccbar is possible. K- π+ M(ψ’π+) with K* veto M 2(ψ’π) B 0 Z ψ’ K* M 2(Kπ) (Ge. V) Phys. Rev. D 88, 074026 (2013) ・Decay into ψ’π+→Contains ccbar ・The charge of ψ’π+ is +1→Not ccbar only →Minimal quark content is 4. ELPH研究会 Ba. Bar reported negative result. Phys. Rev. D 79: 112001, 2009
Confirmation by LHCb experiment 40 Phys. Rev. Lett. 112 (2014) 222002 ・The statistics of B 0→ψ’π+K- is 12 times higher than Belle data. 2010 ± 50± 40 (Belle) ⇔ 25176± 174 (LHCb) ・The statistical significance of the Zc(4430)+ is 13. 9σ. ・Favor JP=1+ by 8σ. ・M=4475± 7+15 -25 Me. V/c 2, Γ=172± 13+37 -34, Consistent with Belle result. ELPH研究会 40
Y(4260) 41 M(π+π- J/ψ) ISR ee+ γ J/ψ Y(4260) π+ π- ・Quantum number is the same as photon: 1 -・No prediction in quark model. ・No DD decay is observed. ・Molecular, bound state of charmonium and gluon? ? ELPH研究会 41
Zc(3900)+ : Second Zc ee+ 42 Phys. Rev. Lett. 110, 252002 (2013) γ J/ψ z π+ Y(4260) π+ M(J/ψπ+π-) Y(4260) Phys. Rev. Lett. 110, 252001 (2013) ELPH研究会 The mass is again close to DD*. 42
Zc(3900) →DD* by BES III γ ee+ D* z 43 M(D 0 D*+) D Y(4260) π+ π decay angle distribution JP=1+ JP=0+ Phys. Rev. Lett. 112, 022001 (2014) ELPH研究会 43
Short summary Name X(3872) Y(4260) Z(3900) Z(4430) JPC 1++ 1 -1+ 1+ 44 Decay J/ψππ etc J/ψππ J/ψπ, DD* ψ’π Production B decay, prompt ISR Y(4260) decay B decay Z: Charmonium with charge. Y: Produced with ISR (JPC=1 --). Not appear in quark model. X: Other mysterious charmoniums. ELPH研究会 44
Relation between Z(3900) and X(3872) 45 ・Assume Z(3900) and X(3872) are orthogonal state in Isospin space. X(3872) is close to the I=0 Z(3900) is close to the I=1 ・The attractive potential from pion exchange is large for I=0 channel →MZ 3900> MX 3872 is qualitatively OK? M(J/ψη) in B→J/ψηK ・The isospin of J/ψπ+ is 1 ・The decay in isospin=0→J/ψη ・Already searched for at Belle but no signal. Interesting subject at Belle II. ELPH研究会 10. 1093/ptep/ptu 043 45
The relation between Zc(3900) and Zc(4430)? 46 Zc(4430): ψ’ (2 S) π+ decay Zc(3900): J/ψ (1 S) π+ decay ・M(Zc(4430)) – M(Zc(3900)) ~= 580 Me. V/c 2 ~= M(ψ’)-M(J/ψ) Imagine this kind of structure. q J/ψ or ψ’ CC q Active works are on going in all over the world! ELPH研究会 46
Physics of (single) charmed baryons c Mass of the charm quark is ~1. 5 Ge. V. This is much heavier than…. 1. Mass of the u, d, s quarks (300 -500 Me. V) spin-spin interaction∝ 1/m 1 m 2 Di-quark correlation in light quarks. -More simplified view of the baryon. -Di-quark excitaion is a hint of qq potential. d u di-quark c c 2. Momentum of quarks inside the baryon radius ~1 fm → 200 Me. V/c. →Non-relativistic quark model is a good approximation. Study of QQ potential from doubly charmed baryon. (Similar to QQbar potential by charmonium spectroscopy) ELPH研究会 d 47
On going analysis: Λc/Σc(2765)+ Most poorly known Λc/Σc state hep-ex/0010080 hep-ex/0608043 ・First evidence by CLEO ・By Belle Λc(2765) + Λc(2880) Λc(2765)+ ・Di-quark excitation (1/2 -)? ・p. D bound state? ・Roper like (1/2+) state? 2803 Me. V/c 2 38 Me. V/c 2 Λc(2940) 2765 Me. V/c 2 M(Λc+π+π-) M(Σ ELPH研究会 cπ) p+D 0 Λc+(2765) 48
Prediction from coupled channel approach hep-ph: 1205. 2275 Coupled channel calculation in I=0 channel. Λc(2595)+ is clearly seen. Charm partner of Λ(1405). Calculate amplitude in I=1 channel Λc(2595)+ If the scenario is correct, it must be. . . ・Isospin = 1 (Σc state) ELPH研究会 ・Jp= 1/2 - (S-wave DN scattering ) 49
Spin-parity measurement of Λc(2880)+ ・Spin/parity measurement by Belle@553 fb-1 (hep-ex/0608043) Σcπ decay angular distribution About 5σ exclusion for spin 1/2, 3/2 M(Λc+π±) for Λc(2880)+ events Σc(2455) Σc(2520) Prediction by Heavy Quark Spin Symmetry R=0. 23 for 5/2+ ELPH研究会 50 R=1. 45 for 5/2
New physics with Belle II 51 ・The semi-leptonic decay B→D(*) τν is mediated by W boson in the SM. ・As the mass of τ is heavy (~1. 7 Ge. V), charged Higgs predicted by SUSY may contribute. ・Taking ratio to the electron, muon: R(D(*)) = BR(B D(*)τν)/BR(B D(*)lν) cancels various uncertainties like form-factors. ・Current measurement on R(D(*)) shows deviation from SM by 4. 0σ HFAG
Results (Preliminary) 52 Mass (Mev/c 2) Width (Me. V) Ξc(2645)+ 2645. 58± 0. 06± 0. 07+0. 28 -0. 40 (2645. 9± 0. 5) 2. 06± 0. 13 (2. 6± 0. 2± 0. 4) Ξc(2815)+ 2816. 73± 0. 08± 0. 06+0. 28 -0. 40 (2816. 6± 0. 9) 2. 43± 0. 20± 0. 17 (<3. 5) Ξc(2980)+ 2966. 0± 0. 8± 0. 2+0. 3 -0. 4 (2970. 7± 2. 2) 28. 1± 2. 4+1. 0 -5. 0 (17. 9± 3. 5) Ξc’+ 2578. 4± 0. 1± 0. 4+0. 3 -0. 4 (2575. 6± 3. 1) - Ξc(2790)+ 2791. 6± 0. 2± 0. 1± 0. 4+0. 3 -0. 4 (2789. 8± 3. 2) 8. 9± 0. 6± 0. 8 (<15) PDG values in () ・Significant improvement for the accuracy of masses. ・First significant measurement for the widths for many states.
Ξcπ(π) (Preliminary) M(Ξc 0π+π-) Ξc(2815)0 M(Ξc 0π+) Ξc(2645)0 M(Ξc 0π+π-) Ξc(2980)0 53 M(Ξc+π+π-) Ξc(2815)+ M(Ξc+π-) Ξc(2645)+ M(Ξc+π+π-) Ξc(2980)+ Reduce background using decay chain Ξc(2815)→Ξc(2645)π→Ξcππ
Ξc’π(π) (Preliminary) M(Ξc 0γ) M(Ξc+γ) Ξ’ 0 Ξ’+ M(Ξc’ 0π+) M(Ξc’+π-) Ξ(2795)+ Ξ(2815)+ Ξ(2980)+ 54 Ξ(2795)0 Ξ(2815)0 Ξ(2980)0 First observations for Ξc(2815)→Ξc’π Ξc(2980)→Ξc’π
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