Searches for exotic mesons

Transcription

1 Searches for exotic mesons Stephen L. Olsen University of Hawai i Multi-quark molecules u c c u qq-gluon hybrids c c baryonium u u d d u u DOE site visit Aug 22, 2005

2 test of QCD: running αs

3 Probe QCD from other directions non-qq or non-qqq hadron spectroscopies: Reawakened by the claims for Pentaquarks e.g. an S=+1 baryon u u d d s

4 Pentaquarks? Seen in many experiments but not seen in just as many others Compass Jlab p BES Belle BaBar CDF High interest: 1 st pentaquark paper has >500 citations

5 Pentaquark Scoreboard Positive signals Negative results Also: Belle Compass L3 Jlab(CLAS) (γp K + K s n) Yes: 17 No: 18

6 This talk Searches for non-standard mesons with hidden charm at Belle u c c u c c Search for baryonium mesons at BES u u d d u u

7 searches for non-standard mesons u c c u with hidden charm at Belle standard cc mesons are: best understood theoretically narrow & non overlapping c + c systems are commonly produced in B meson decays. b (i.e containing c & c) V cb W - CKM favored cosθ C c c c c s

8 Thanks to KEKB, Belle has lots of B mesons (>1M BB pairs/day) >1fb -1 /day Design: 10 34

9 X(3872) π + π J/ψ B K π + π J/ψ ψ π + π J/ψ X(3872) π + π J/ψ S.-K.Choi, S.L.Olsen et al (Belle) PRL (2003) M(ππJ/ψ) M(J/ψ)

10 Its existence is well established seen in 4 experiments 9.4σ 11.6σ CDF X(3872) D0 X(3872)

11 Is it a cc meson? Could it be one of these? 3872 MeV These states are already identified

12 no obvious cc assignment 3872 η c h c χ c1 M too low and Γ too small angular dist n rules out 1 + Γ(γJ/ψ) way too small ψ 2 Γ(γχ c1 ) too small;m(π + π ) wrong η c2 ψ 3 ππ η c should dominate Γ( γχ c2 & DD) too small SLO hep-ex/

13 go back to square 1 Determine J PC quantum numbers of the X(3872) with minimal assumptions

14 J PC possibilities (for J 2) exotic violates parity (η c ) (χ c0 ) exotic (ψ(3s)) exotic (χ c1 ) (h c ) (ψ 2 ) (η c2 ) (χ c2 ) exotic

15 J PC possibilities 0 -- ruled out; J P =0 +,1 - & 2 + unlikely exotic violates parity (η c ) exotic (ψ(3s)) (ψ 2 ) (η c2 ) 0 ++ (χ c0 ) 1 ++ (χ c1 ) 2 ++ (χ c2 ) 0 +- exotic 1 +- (h c ) 2 +- exotic

16 M(π + π ) Strong evidence for C=+1 X(3872) γj/ψ X(3872) π + π π 0 J/ψ virtual ω(782)? 13.6 ± 4.4 X(3872) γj/ψ evts (>4σ significance) Bf(X γj/ψ) Bf(X ππj/ψ) =0.14 ± 0.05 M(π + π π 0 ) Br(X 3πJ/ψ) Br(X 2πJ/ψ) = 1.0 ± 0.5 X(3872) π + π J/ψ Fits to ρ(760)

17 J PC possibilities (C=-1 ruled out) 0 -- exotic Violates parity exotic (η c ) (χ c0 ) 1 -- (ψ(3s)) (h c ) exotic (χ c1 ) 2 -- (ψ 2 ) 2 -+ (η c2 ) 2 ++ (χ c2 ) 2 +- exotic

18 Angular Correlations ρ J z =0 X 3872 J=0 J=0 z K Rosner (PRD ) Bugg (PRD ) Suzuki, Pakvasa (PLB ) J/ψ

19 θ θ lπ ψ χ 2 /dof=18/9 χ 2 /dof = 34/9 χ 2 /dof=34/9 cosθ cosθ lπ rule out 0 ++ & 0 -+ cosψ

20 J PC possibilities (0 -+ & 0 ++ ruled out) 0 -- exotic violates parity 0 -+ (η c ) 0 ++ (χ c0 ) 0 +- exotic 1 -- (ψ(3s)) exotic (ψ 2 ) 2 -+ (η c2 ) 1 ++ (χ c1 ) 2 ++ (χ c2 ) 1 +- (h c ) 2 +- exotic

21 M(ππ) can distinguish ρ-j/ψ S- & P-waves S-wave: χ 2 /dof = 43/39 (CL= 28%) P-wave: χ 2 /dof = 71/39 (CL=0.1%) q* roll-off Shape of M(ππ) distribution near the kinematic limit favors S-wave q* 3 roll-off

22 Possible J PC values (J -+ ruled out) 0 -- exotic violates parity 0 -+ (η c ) 0 ++ (χ c0 ) 0 +- exotic 1 -- (ψ(3s)) exotic (χ c1 ) 1 +- (h c ) 2 -- (ψ 2 ) 2 -+ (η c2 ) 2 ++ (χ c2 ) 2 +- exotic

23 X(3872) D 0 D 0 π 0? D *0 D 0 π 0? 1 ++ : DD* in an S-wave q* 2 ++ : DDπ in a D-wave q* 5 Strong threshold suppression M(D 0 D 0 π 0 ) 11.3±3.6 sig.evts (>4σ) Bf(B KX)Bf(X DDπ)=2.2±0.7±0.4x10-4

24 Possible J PC values (2 ++ ruled out) 0 -- exotic violates parity 0 -+ (η c ) 0 ++ (χ c0 ) 0 +- exotic 1 -- (ψ(3s)) 1 -+ exotic (χ c1 ) 1 +- (h c ) 2 -- (ψ 2 ) 2 -+ (η c2 ) 2 ++ (χ c2 ) 2 +- exotic

25 can it be a 1 ++ cc state? 1 ++ χ c1 Mass is too low 3872 π + π (Isospin forbidden) Bf(X π+π J/ψ)>4% is too large χ c1 component of X(3872) is few%

26 Intriguing fact M X3872 =3872 ± 0.6 ± 0.5 MeV m D0 + m D0* = ± 1.0 MeV lowest mass charmed meson lowest mass spin=1 charmed meson Deuson? deuteron-like DD* bound state? c π D D* u c u 2 loosely bound qq color singlets with M= m D+ m D* - δ one π exchange attractive for 1 ++ Tornqvist PLB 590, 209 (2004)

27 X(3872) = D 0 D* 0 bound state? J PC = 1 ++ is favored M m D0 + m D0* Tornqvist PLB 590, 209 (2004) Large isospin violation is natural (& was predicted): D 0 D* 0 > = 1/ 2( 10> - 00>) Γ(X γj/ψ) < Γ(X ππj/ψ) was predicted Γ(X D 0 D 0 π 0 ) too large? Equal mixture of I=1 & I =0 Swanson PLB 588, 189 (2004) Swanson PLB 598, 197 (2004)

28 X(3872) conclusion J PC = 1 ++ cc content is small C C matches most expectations for a D 0 D* 0 bound state a non-qq meson u c u c

29 Are there others? Is the X(3872) a one-of-a-kind curiousity? or the 1 st entry in a new spectroscopy? Look at other B decays hadrons+j/ψ: B K η J/ψ B K π J/ψ B K ω J/ψ

30 B K ωj/ψ in Belle Y(3940) M 3940 ± 11 MeV Γ 92 ± 24 MeV M bc M bc M bc S.K. Choi et al hep-ex/ to appear in PRL

31 Y(3940): What is it? Brambilla et al (QWG) hep-ph/ Charmonium? Conventional wisdom: ωj/ψ should not be a discovery mode for a cc state with mass above DD & DD* threshold! Some kind of ω-j/ψ threshold interaction? the J/ψ is not surrounded by brown muck; can it act like an ordinary hadron? J/ψ ω

32 Y(3940): What is it (cont d)? another tetraquark? M 2m Ds not seen in Y ηj/ψ (η contains ss) s c s c?? PRL 93, M(η J/ψ) width too large?? no π exchange for D S D S

33 Y(3940): What is it (cont d)? cc-gluon hybrid? predicted by QCD, decays to DD and DD* are suppressed ( open-charm thresh = m D + m D** = 4.3 GeV) large hadron+j/ψ widths are predicted masses expected to be 4.3 ~ 4.4 GeV (higher than what we see) c c Horn & Mandula PRD (1974) + (many) others

34 e + e BaBar s Y(4260) γ π π J / ψ ( J/ψ e e or µ µ ISR ) 211 fb -1 data collected at (s) = GeV ψ(2s) Y(4260) 11802±110 ψ(2s) evts 125±23 Y(4260) evts M=4259 ± 8 MeV Γ = 88 ± 23 MeV J/ψ sideband Well above DD & DD* threshold but found in an OZI-suppressed mode??

35 X(3872): cc summary J PC established as 1 ++ cc component is small ( few %) all properties consistent with a D 0 D* 0 bound state u Y(3940), Y(4260): c c u No obvious cc assignment tetraquark seems unlikely cc-gluon hybrid? a non-standard meson c????? -Lots to do: determine J PC ; find other modes (DD*, D s D s,?) c

36 Baryonium at BES? acceptance weighted BW M=1859 MeV/c 2 Γ < 30 MeV/c 2 (90% CL) Phys. Rev. Lett. 91, (2003) J/ψ γpp 3-body phase space M(pp)-2m p (GeV)

37 Baryonium potential & Wave fcn Potential barrier G.J. Dung & M.L. Yan hep-ph/ I = 0, J pc =0 -+ pp annihilation -V 0 δ(r) M ~ 1860 MeV Γ ~ 16 MeV Rectangularized Skyrmion-type potential large uncertainties X π + π η should be a strong channel

38 M(π + π η ) from J/ψ γ π + π η 7.7σ The π + π - η mass spectrum for η decaying into η π + π - η and η γρ N obs = 264 ± 54 BESII Preliminary M = 1834±6±3 MeV Γ = 68 ± 20 ±8 MeV B( J ψ γx ) B( X π π η ) + = (2.2 ± 0.4 ± 0.4) 10 4 c. f. : B( J ψ γx ) B( X pp ) = (7.0 ± )

39 _ Re-fit to J/ψ γp p including FSI Include FSI curve from A.Sirbirtsev et al. ( Phys.Rev.D71:054010, 2005 ) in the fit (I=0) M = ± 6.7 MeV Γ = < 153 In good agreement with X(1835) M 2m pp p

40 Other new particles from Belle e + e - J/ψ + X

41 X(3940) DD* seen ( DD & ωj/ψ not seen)

42 γγ Z(3931) DD at Belle sin 4 θ (J=2) 41± 11 evts (5.5σ) M=3931 ± 4 ± 2 MeV Γ=20±8 ±3 MeV

43 Z(3931) = χ c1 (almost for sure)? X(3940) Y(3940) (maybe the η c )

44 Hawaii particles η c X(1860)( pp) X(3872) Y(3940)

45 Back-up slides

46 244 fb -1 e + e - B + B - K - X 0 Jon Coleman Moriond-QCD March 2005 Can measure absolute B.F. s of B - K - X 0 Lower limit on BF(X J/ψππ) > 90% C.L χ c2 χ c1 χ c0 J/ψ χ c2,χ c0 <<χ c1 X(3872) production much lower than for other Charmonium states: can set lower limit on B.F. Very clear J/ψ and η c signals N J/ψ= N η c =

47 e + E cm /2 Kinematic variables CM energy difference: E = E + E E / 2 Beam-constrained mass: 2 r r m = E 2) ( p + p bc ϒ(4S) B B K E cm /2 e γj / ψ cm ( CM K γj / ψ ) 2 B K γj/ψ E B K γj/ψ M bc

48 1 ++ : sin 2 θ l sin 2 χ 1 ++ compute angles in X(3872) restframe χ 2 /dof = 11/9 θ l K cosθ l χ χ 2 /dof = 5/ looks okay! cosχ

49 M(γJ/ψ) look-back plot

50 cosθ lπ Fit cosθ lπ with 1 ++ MC χ 2 /dof=11.9/9