New types of sub-atomic particles

Transcription

1 New types of sub-atomic particles Stephen L. Olsen University of Hawai i u u d d s u c c u c c

2 History: (hadrons) 1930 s: proton & neutron..all we need??? chadwick 1950 s: π,ρ,κ,σ,λ,ξ Had I foreseen that, I would have gone into botany Fermi 1960 s: The 8-fold way 3 quarks for Müster Mark 1970 s add charmed particles Gell-Mann Zweig Fermi 1980 s & beauty Richter Ting Lederman 1990 s & (finally?) top Peters Jones

3 Hadron zoo mesons baryons

4 Quarks restore economy (& rescue future Fermis from Botany?) M. Gell-Mann 3 quarks u +2/3 d -1/3 s -1/3 (& 3 antiquarks) u -2/3 d +1/3 s +1/3 Zweig Baryons: qqq Mesons: q q p: p: u +2/3 d -1/3 u +2/3 u -2/3 π+ : u -2/3 u +2/3 d +1//3 π - : u +2/3 d +1/3 u -2/3

5 Fabulously successful, but quarks are not seen why only qqq and qq combinations? What about spin-statistics?

6 Ω s -1/3 s -1/3 s -1/3 2 of these s-quarks are in the same quantum state Das ist verboten!!

7 The strong interaction charge of each quark comes in 3 different varieties Y. Nambu O. Greenberg Ω - s -1/3 s -1/3 s -1/3 the 3 s -1/3 quarks in the Ω - have different color charges & evade Pauli

8 QCD: Gauge theory for color charges Nambu Gell-Mann & Fritzsch generalization of QED QED QCD e r scalar charge: e isovector charge: e b QED gauge Xform e g + i e A 1 vector field (photon) QCD gauge Xform + i α λ i G i eight 3x3 SU(3) matrices 8 vector fields (gluons)

9 Hence the name: Quantum Chromodynamics Attractive configurations ε ijk e i e j e k i j k δ ij e i e j same as the rules for combining colors to get white: add 3 primary colors or add color+complementary color quarks: e i e j e k color charges antiquarks: e i e j e k anticolor charges

10 Difference between QED & QCD QED: photons have no charge QCD: gluons carry color charges gluons interact with each other

11 QED QCD difference Coupling strength α distance

12 Test QCD with 3-jet events (& deep inelastic scattering) α s gluon rate for 3-jet events should decrease with E cm

13 running α s Why are these people smiling?

14 Probe QCD from other directions non-qq or non-qqq hadron spectroscopies: Pentaquarks: e.g. an S=+1 baryon (only anti-s quark has S=+1) u u d d s Glueballs: gluon-gluon color singlet states Multi-quark mesons: u c c u qq-gluon hybrid mesons c c

15 Pentaquarks Seen in many experiments but not seen in just as many others BES Belle BaBar CDF High interest: 1 st pentaquark paper has ~500 citations

16 Experimental situation is messy (many contradictory results) NA49 E cm =17 GeV (fixed tgt) (PRL92, : 237+ citations!) Ξ(1862): qqssd COMPASS E µ =160 GeV (fixed tgt) 1862 ± 2 MeV FWHM = 17 MeV σ = s of Ξ(1530)s but no hint of Ξ(1862) hep-ex/

17 Pentaquark Scoreboard Positive signals Negative results Also: Belle Compass L3 Yes: 17 No: 17

18 Existence of Pentaquarks is not yet established

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

20 Thanks to KEKB we have lots of B mesons (>1M BB pairs/day) >1fb -1 /day Design: 10 34

21 Is the X(3872) non-standard? B K π + π J/ψ ψ π + π J/ψ X(3872) π + π J/ψ S.K. Choi et al PRL 91, M(ππJ/ψ)

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

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

24 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/

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

26 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

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

28 Areas of investigation Search for radiative decays Angular correlations in X ππj/ψ decays Fits to the M(ππ) distribution Search for X(3872) D 0 D 0 π 0

29 Search for X(3872) γ J/ψ

30 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

31 Select B Kγ J/ψ B Kχ c1 ; χ c1 γ J/ψ X(3872)? M(γJ/ψ) 13.6 ± 4.4 X(3872) γj/ψ evts (>5σ significance) M bc M bc Bf(X γj/ψ) =0.14 ± 0.05 Bf(X ππj/ψ)

32 Evidence for X(3872) π + π π 0 J/ψ (reported last summer hep-ex/ ) 12.4 ± 4.2 evts B-meson yields vs M(π + π π 0 ) Br(X 3πJ/ψ) Br(X 2πJ/ψ) = 1.0 ± 0.5 Large (near max) Isospin violation!!

33 C=+1 is established B γ J/ψ only allowed for C=+1 same for X ω J/ψ (reported earlier) M(ππ) for X π + π J/ψ looks like a ρ

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

35 Angular Correlations ρ J z =0 X 3872 J=0 J=0 z K J/ψ

36 Strategy: for each J PC, find a distrib 0 if we see any events there, we can rule it out Rosner (PRD ) Bugg (PRD ) Suzuki, Pakvasa (PLB )

37 Use 250 fb -1 ~275M BB prs exploit the excellent S/N ψ π + π J/ψ X(3872) π + π J/ψ Signal Sidebands (47 ev) (114/10 = 11.4 ev)

38 : sin 2 θ sin 2 ψ χ 2 /dof=18/9 θ cosθ χ 2 /dof=34/9 ψ safe to rule out 0 -+ cosψ

39 θ lπ 0 ++ In the limit where X(3872), ππ, & J/ψ rest frames coincide: dγ/dcosθ lπ sin 2 θ lπ χ 2 /dof = 41/9 rule out 0 ++ cosθ lπ

40 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

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

42 Fits to the M(ππ) Distribution ρ q* X J/ψ q* X ρj/ψ in P-wave has a q* 3 centrifugal barrier

43 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

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

45 Search for XÆD D π

46 Select B KD 0 D 0 π 0 events D *0 D 0 π 0? M(D 0 D 0 π 0 ) 11.3±3.6 sig.evts (5.6σ) Bf(B KX)Bf(X DDπ)=2.2±0.7±0.4x10-4 Preliminary E E

47 X DDπ rules out : DD in an S-wave q* 2 ++ : DDπ in a D-wave q* 5 Strong threshold suppression

48 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

49 can it be a 1 ++ cc state? 1 ++ χ c1 Mass is ~100 MeV off χ c1 ρ J/ψ not allowed by isospin. Expect: Bf(χ c1 ππj/ψ)<0.1% BaBar measurement: Bf(X ππj/ψ)>4% Γ(χ c1 γj/ψ) / Γ(χ c1 ππj/ψ) Theory: ~ 40 Expt: 0.14 ± 0.05 χ c1 component of the X(3872) is few %

50 Intriguing fact M X3872 =3872 ± 0.6 ± 0.5 MeV lowest mass charmed meson m D0 + m D0* = ± 1.0 MeV lowest mass spin=1 charmed meson X(3872) is very near DD* threshold. is it somehow related to that?

51 hh bound states (hadronium)? There is lots of literature about this possibility deuteron: attractive nuclear force hadronium (dueson): attractive force?? p π n D D* c u π c N. Tornqvist hep-ph/ u 2 loosely bound qqq color singlets with M d = m p +m n - ε 2 loosely bound qq color singlets with M= m D+ m D* - δ

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

53 X(3872) conclusion Not a cc state C C Matches all(?) expectations for a D 0 D* 0 bound state 1 st clear example of a non-qq meson u c u c

54 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

55 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/ PRL

56 Y(3940): What is it? 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

57 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?? need to search for Y(3949) D S D S

58 Y(3940): What is it (cont d)? cc-gluon hybrid? predicted by QCD, decays to DD and DD* are suppressed 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)

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

60 Mahalo

61 Back-up slides

62 Difference between QED & QCD QED: photons have no charge QCD: gluons carry color charges gluons interact with each other

63 Vacuum polarization QED vs QCD 2n f 11C A in QCD: C A =3, & this dominates

64 QED QCD difference Coupling strength α distance

65 Testing the Standard Model QCD X Electro-Weak X QED decrease in α s with distance W, Z & t masses Z width sin 2 θ W Asymmetries Cross-sections Lamb-shift g-2 Atomic spectra

66 Tests of QED and EW sectors QED ppb) Example: Electro-Weak sector ~0.01% level) (g-2)/2 electron Expt: 1,159,652,188.4(4.3)x10-12 Theory: 1,159,652,201.4(28)x10-12

67 M(γJ/ψ) look-back plot

68 e + e - J/ψ + X Another one? >4σ)peak at M=3940±11 MeV N=148±33 evts Width consistent w/ resolution (= 32 MeV) η c η c χ c0 η c What is it? χ c0? η c??

69 Look at e + e - J/ψ D(D ( * ) ) Reconstruct a J/ψ & a D use D 0 K - π + & D + K - π + π + Determine recoil mass

70 Look at M(DD ( * ) ) 3940 MeV DD* 9.9 ± 3.3 evts (4.5 σ) χ c0 DD* DD 4.1 ± 2.2 evts (2.1 σ) η c DD

71 Other hadronium states? fitted peak location J/ψ γpp in the BES expt J.Z.Bai PRL 91,022001(2003) M=1859 MeV/c 2 Γ < 30 MeV/c 2 (90% CL) χ 2 /dof=56/ M(pp)-2m p (GeV) acceptance