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X(3872) Review

X(3872) Review. T.Aushev LPHE seminar. Introduction. Era of the new family of particles, named XYZ, started from the observation of X(3872) in the J/ψ π+π- final state by the Belle experiment

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X(3872) Review

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  1. X(3872) Review T.Aushev LPHE seminar

  2. Introduction • Era of the new family of particles, named XYZ, started from the observation of X(3872) in the J/ψ π+π- final state by the Belle experiment • Many new states have been found/observed/studied by Belle and other experiments, BaBar, CDF, D0, CLEO after that • This is just a short list of them X(3872), X(3940), Y(3940), X(4160), Y(4008), Y(4260), Y(4350), Y(4660), Z(3930), Z(4415), Z(4430)+, Yb(10580), … • These particles are not fittable to any of the known or predicted states • Most probably it is new type of quark particles in addition to mesons and baryon, although it is not proved yet T.Aushev, LPHE seminar

  3. Observation of X(3872) Observed by Belle in B± → K± +-J/ 2003 152M BB, PRL91, 262001(2003) X(3872) ' Belle data: 152 M BB events Mass = 3872.0±0.6±0.5 MeV Significance = 10 σ M(+-l+l-)-M(l+l-) It did not fit to any known cc-bar states Mass of X(3872) is close to DD* What is it: charmonium, DD*-molecule, tetraquark...? T.Aushev, LPHE seminar

  4. Most recent measurements 0809.1224 (2008) 0906.5218 (2009) 12.8σ (K+) + 5.9σ (KS) 5.2σ 0405004 (2004) (>> or = ∞) σ 0803.2838 (2008) 8.6σ (K+) + 2.3σ (KS) 8 February 2010 T.Aushev, LPHE seminar 4

  5. X(3872) mass measurements • Recent CDF’s result is the most precise measurement of X(3872) mass • Together with CLEO’s update on the D0 mass gives hint on the X(3872) mass to be below the D0D*0 threshold Current mass is below the DD* threshold T.Aushev, LPHE seminar

  6. Determination of JPC quantum numbers of the X(3872) T.Aushev, LPHE seminar

  7. JPC possibilities (for J ≤ 2) T.Aushev, LPHE seminar

  8. no. of B’s in M(J/) bins 13.6±4.4 ev. (4) M=3872 MeV =13 MeV X(3872) C-parity Belle, 275M BB, hep-ex/0505037(2005) B± → K± J/ Existence of X(3872)J/ established: C(X(3872))=+1 J/ (2S) BaBar, 465M BB, 0809.0042 (2009) Relatively large fraction of (2S)  supports D*D molecule hypothesis and possible admixture of cc-bar component 8 February 2010 T.Aushev, LPHE seminar 8

  9. 5.200 Isospin violation B± → K± ( + - 0)J/ virtual → +- 0 Further evidence for C(X(3872))=+1 If 3 come from , 2 – from  large isospin violation, difficult to explain if X=cc state 8 February 2010 T.Aushev, LPHE seminar 9

  10. JPC possibilities (for J ≤ 2) T.Aushev, LPHE seminar

  11. Belle, 275M BB, hep-ex/0505038 X(3872) P-parity M( + -) from B± → K±  + -J/ Looks like X(3872)→J/  J/ : S wave P wave For C=+1: if P=+1 L({+-},J/)=0,2,… P=-1 L({+-},J/)=1,3,… M( + -) upper boundary is modulated by q2L+1 centrifugal barrier: S,P waves should dominate S wave: 2/dof=43.1/39 (CL=28%) P wave: 2/dof=71.0/39 (CL=0.1%) 55% 7.7% P(X(3872))=+1 8 February 2010 T.Aushev, LPHE seminar 11

  12. JPC possibilities (for J ≤ 2) T.Aushev, LPHE seminar

  13. + X(J/)  l- l+ - - X(J/)  B K + X(3872) properties (cont') Angular distributions in B± → K±  + -J/ Belle, hep-ex/0505038 0++ (S, D waves) is disfavored expected JPC=0++ Opposite parity 0-+ (P wave) has been also ruled out |cos| side band 1++ (S, D waves) is favored JPC=0++, 1++, 2++ ? JPC=1++ |cos| 8 February 2010 T.Aushev, LPHE seminar 13

  14. JPC possibilities (for J ≤ 2) T.Aushev, LPHE seminar

  15. CDF study of quantum numbers T.Aushev, LPHE seminar

  16. JPC possibilities (for J ≤ 2) T.Aushev, LPHE seminar

  17. JPC possibilities (for J ≤ 2) T.Aushev, LPHE seminar

  18. Quantum numbers summary JPC = 1++ is the most favored 1++ charmonium Xc1’ state is unlikely assignment for X(3872): Potential model predicts Xc1’ mass to be 3953-3990 MeV/c2 Large isospin violation coming from BR(XJ/ψω)/BR(XJ/ψρ) ~ 1  J/ decay of  ’c1 should be much stronger than isospin violating decay  J/. Experimentally the ratio is 0.14±0.05. Possible interpretation: X(3872) =D0D*0 molecule T.Aushev, LPHE seminar

  19. DD* threshold enhancement in BKDD* D0D0p0 PRD 77, 011102 (2008) PRL 97, 162002 (2006) Both saw higher mass & BR(DD*) ≈ 10x BR(π+π-J/ψ) Higher X mass raised some speculations about new particle X(3875) T.Aushev, LPHE seminar

  20. B→X(3872) K; X(3872)D*0D0; D*0D0 (γ,π0) hep-ex:0810.0358 MD*D = (3872.9+0.6-0.4+0.4-0.5) MeV BaBar: (3875.1+0.7-0.5±0.5) MeV Γ(Belle) =(3.9+2.8-1.4+0.2-1.1) MeV Γ(BaBar)=(3.0+2.5-1.3+0.5-0.3) MeV Nsig = 50.1+14.8-11.1 Significance = 6.4 σ X(3872) mass shape is also well fittable by Flatte function NEW BR(BX(3872)(D*0D0)K) = (0.73±0.17±0.13)×10-4 2++ is rather unlikely (at least one D wave near threshold) T.Aushev, LPHE seminar

  21. X(3872)→J/ψπ+π– B+→XK+ 12.8 B0→XK0s 5.9 Charged and neutral partners of X(3872) diquark-antidiquark models Xu and Xd from B0and B+decays MX= 8±3 MeV Maiani et al PRD71, 014028 MX=(+0.18±0.89±0.26 )MeV/c2 Br(B0→XK0) / Br(B+→XK+) = 0.82± 0.22±0.05 Br(B0→XK0) Br(J/–+)= (6.65± 1.63± 1.00)x10–6 Br(B+→XK+) Br(J/–+)= (8.10± 0.92± 0.66)x10–6 T.Aushev, LPHE seminar

  22. Molecule model Most advanced theory which can explain all observed decay modes and their parameter is the molecule model. According to it X(3872) is the D*0D0 state with bounding energy which make its mass below D*0D0 threshold. It favors ten times larger BR to double charm in comparison with charmonium decays T.Aushev, LPHE seminar

  23. Different models • X(3872) likely not a charmonium state • Radial excitation of χc1 (JPC = 1++) expected at 3950 MeV/c2 • ηc2 (JPC = 2-+) should have X →J/ψγ suppressed • No satisfactory cc assignment • D0D*0molecule? Phys. Rev. D71, 074005 (2005) • Would explain proximity of the D0D*0threshold • favors DD* decay over J/ψππ over J/ψγ (as observed) • Expect X →ψ(2S)γ to be suppressed (in contradiction with observation) • tetraquark state? Phys. Rev. D71, 014028 (2005) • Predict 2 neutral states and 2 charged states • Neutral states produced in B0 and B+ decays: Δm ≈ (7 ± 2) MeV/c2 • Measurements: • Δm = (+0.18±0.89±0.26) MeV/c2 in B →J/ψπ+π- • No evidence for charged partners • Mixing of D0D*0 and χc1? Something else?... T.Aushev, LPHE seminar

  24. Conclusion • X(3872) is JPC=1++ state • Normal cc-bar charmonium can not be assigned to this particle • Most probable nature is D0D*0 molecule with probably admixture of normal cc-bar state T.Aushev, LPHE seminar

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