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The hidden charm of hadrons Stephen L. Olsen University of Hawai’i Representing Belle Invited talk at the Tampa APS/DPF meeting, April 19, 2005
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test of QCD: “running” s
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Probe QCD from other directions non-qq or non-qqq hadron spectroscopies: Pentaquarks: e.g. an S=+1 baryon Glueballs: gluon-gluon color singlet states Multi-quark mesons: qq-gluon hybrid mesons uc u c cc u d u s d
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This talk: search for non-standard mesons with “hidden charm” standard cc mesons are: –best understood theoretically –narrow & non overlapping c + c systems are commonly produced in B meson decays. b c c s V cb cos C CKM favored W-W- cc uc u c (i.e containing c & c)
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Thanks to KEKB, Belle has lots of B mesons (>1M BB pairs/day) >1fb -1 /day Design: 10 34
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Is the X(3872) non-standard? B K J/ M( J ) –M(J/ ) ’ J/ X(3872) J/
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Its existence is well established seen in 4 experiments X(3872) CDF X(3872) D0 hep-ex/0406022 9.4 11.6
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Is it a cc meson? These states are already identified 3872 MeV Could it be one of these?
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no obvious cc assignment 3872 c ” h c ’ c1 ’ 2 c2 3 M too low and too small angular dist’n rules out 1 J/ way too small c too small;M( ) wrong c & DD) too small c should dominate SLO hep-ex/0407033
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go back to square 1 Determine J PC quantum numbers of the X(3872) with minimal assumptions
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J PC possibilities (for J ≤ 2) 0 -- exotic violates parity 0 -+ ( c ” ) 0 ++ DD allowed ( c0 ’ ) 0 +- exotic DD allowed 1 - - DD allowed ( (3S)) 1 -+ exotic DD allowed 1 ++ ( c1 ’ ) 1 +- (h c ’ ) 2- -(2)2- -(2) 2 - + ( c2 ) 2 ++ DD allowed c2 ’ ) 2 +- exotic DD allowed
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J PC possibilities 0 -- ruled out; J P =0 +,1 - & 2 + unlikely 0 -- exotic violates parity 0 -+ ( c ” ) 0 ++ DD allowed ( c0 ’ ) 0 +- exotic DD allowed 1 - - DD allowed ( (3S)) 1 -+ exotic DD allowed 1 ++ ( c1 ’ ) 1 +- (h c ’ ) 2- -(2)2- -(2) 2 - + ( c2 ) 2 ++ DD allowed c2 ’ ) 2 +- exotic DD allowed
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Areas of investigation Search for radiative decays Angular correlations in X J/ decays Fits to the M( ) distribution Search for X(3872) D 0 D 0 0
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Search for X(3872) J/
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Kinematic variables CM energy difference: Beam-constrained mass: B K J B K J B B ϒ (4S) E cm /2 ee ee M bc EE
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Select B K J/ B K c1 ; c1 J/ X(3872)? 13.6 ± 4.4 X(3872) J/ evts (>4 significance) M( J/ ) Bf(X J/ ) Bf(X J/ ) =0.14 ± 0.05 M bc
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Evidence for X(3872) J/ reported last summer hep-ex/0408116) 12.4 ± 4.2 evts B-meson yields vs M( ) Br(X 3 J/ ) Br(X 2 J/ ) = 1.0 ± 0.5 Large (near max) Isospin violation!! A virtual (782)?
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C=+1 is established X J/ only allowed for C=+1 same for X ” ”J/ (reported earlier) M( ) for X J/ looks like a CDF
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J PC possibilities (C=-1 ruled out) 0 -- exotic Violates parity 0 -+ ( c ” ) 0 ++ DD allowed ( c0 ’ ) 0 +- exotic DD allowed 1 - - DD allowed ( (3S)) 1 -+ exotic DD allowed 1 ++ ( c1 ’ ) 1 +- (h c ’ ) 2 - - ( 2 ) 2 - + ( c2 ) 2 ++ DD allowed c2 ’ ) 2 +- exotic DD allowed
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Angular Correlations K J/ J=0 X 3872 J z =0 z Rosner (PRD 70 094023) Bugg (PRD 71 016006) Suzuki, Pakvasa (PLB 579 67)
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Use 253 fb -1 ~275M BB prs exploit the excellent S/N Signal (47 ev) Sidebands (114/10 = 11.4 ev) X J/ ’ J/
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0 ++ ll In the limit where X(3872), , & J/ rest frames coincide: d /dcos l sin 2 l rule out 0 ++ |cos l | 2 /dof = 34/9
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0 -+ 0 -+ : sin 2 sin 2 safe to rule out 0 -+ |cos | |cos | 2 /dof=34/9 2 /dof=18/9
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1 ++ ll 1 ++ : sin 2 l sin 2 K 1 ++ looks okay! compute angles in X(3872) restframe |cos l | 2 /dof = 11/9 |cos | 2 /dof = 5/9
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J PC possibilities (0 -+ & 0 ++ ruled out) 0 -- exotic violates parity 0 -+ ( c ” ) 0 ++ DD allowed ( c0 ’ ) 0 +- exotic DD allowed 1 - - DD allowed ( (3S)) 1 -+ exotic DD allowed 1 ++ ( c1 ’ ) 1 +- (h c ’ ) 2 - - ( 2 ) 2 - + ( c2 ) 2 ++ DD allowed c2 ’ ) 2 +- exotic DD allowed
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Fits to the M( ) Distribution X J/ has a q* (2l+1) centrifugal barrier X J/ q*
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M( ) can distinguish -J/ S- & P-waves S-wave: 2 / dof = 43/39 P-wave: 2 / dof = 71/39 q* roll-off q* 3 roll-off (CL=0.1%) (CL= 28%) Shape of M( ) distribution near the kinematic limit favors S-wave
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Possible J PC values (J -+ ruled out) 0 -- exotic violates parity 0 -+ ( c ” ) 0 ++ DD allowed ( c0 ’ ) 0 +- exotic DD allowed 1 - - DD allowed ( (3S)) 1 -+ exotic DD allowed 1 ++ ( c1 ’ ) 1 +- (h c ’ ) 2 - - ( 2 ) 2 - + ( c2 ) 2 ++ DD allowed c2 ’ ) 2 +- exotic DD allowed
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Search for X(3872) D 0 D 0 0
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Select B K D 0 D 0 0 events | E| 11.3±3.6 sig.evts (5.6 ) Bf(B KX)Bf(X DD )=2.2 ± 0.7 ± 0.4x10 -4 Preliminary D *0 D 0 0 ? M(D 0 D 0 0 )
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X(3872) DD rules out 2 ++ 1 ++ : DD* in an S-wave q* 2 ++ : DD in a D-wave q* 5 Strong threshold suppression
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Possible J PC values (2 ++ ruled out) 0 -- exotic violates parity 0 -+ ( c ” ) 0 ++ DD allowed ( c0 ’ ) 0 +- exotic DD allowed 1 - - DD allowed ( (3S)) 1 -+ exotic DD allowed 1 ++ ( c1 ’ ) 1 +- (h c ’ ) 2 - - ( 2 ) 2 - + ( c2 ) 2 ++ DD allowed c2 ’ ) 2 +- exotic DD allowed 1 ++
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can it be a 1 ++ cc state? 1 ++ c1 ’ –Mass is ~100 MeV off – c1 ’ J/ not allowed by isospin. Expect: Bf( c1 ’ J/ )<0.1% BaBar measurement: Bf(X J/ )>4% 3872 - ( c1 ’ J/ ) / ( c1 ’ J/ ) Expect: ~ 40 ( X 3872 J/ ) / ( X 3872 J/ ) Measure: 0.14 ± 0.05 c1 ’ component of X(3872) is ≤few %
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Intriguing fact M X3872 =3872 ± 0.6 ± 0.5 MeV m D0 + m D0* = 3871.2 ± 1.0 MeV lowest mass charmed meson lowest mass spin=1 charmed meson X(3872) is very near DD* threshold. is it somehow related to that?
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D 0 D* 0 bound state (deuson)? pn DD* deuteron: 2 loosely bound qqq color singlets with M d = m p +m n - deuson: 2 loosely bound qq color singlets with M = m D + m D* - attractive nuclear force attractive force?? N. Tornqvist hep-ph/0308277 u c u c
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X(3872) = D 0 D* 0 bound state? J PC = 1 ++ is favored M ≈ m D0 + m D0* 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>) (X J/ ) < (X J/ ) was predicted Equal mixture of I=1 & I =0 Swanson PLB 598, 197 (2004) Tornqvist PLB 590, 209 (2004) Swanson PLB 588, 189 (2004)
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X(3872) conclusion J PC = 1 ++ cc content is small matches all(?) expectations for a D 0 D* 0 bound state CC u c u c a non-qq meson
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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/ B K J/ B K J/ B K J/
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B K J/ in Belle “Y(3940)” M≈3940 ± 11 MeV ≈ 92 ± 24 MeV M bc S.K. Choi et al hep-ex/0408126 to appear in PRL
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Y(3940): What is it? Charmonium? –Conventional wisdom: J/ should not be a discovery mode for a cc state with mass above DD & DD* threshold! Some kind of -J/ threshold interaction? –the J/ is not surrounded by brown muck; can it act like an ordinary hadron? J/ Brambilla et al (QWG) hep-ph/0412158
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Y(3940): What is it (cont’d) ? another tetraquark? –M ≈ 2m Ds –not seen in Y J/ ( contains ss) –width too large?? –no exchange for D S D S s c s c ?? PRL 93, 041801 M( J/ )
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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/ widths are predicted –masses expected to be 4.3 ~ 4.4 GeV (higher than what we see) cc Horn & Mandula PRD 17 898 (1974) + (many) others
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Summary X(3872): –J PC established as 1 ++ –cc component is small (≤ few %) –all properties consistent with a D 0 D* 0 bound state uc u c a non-standard meson Y(3940): –No obvious cc assignment –tetraquark seems unlikely –cc-gluon hybrid? cc ????? - Lots to do: determine J PC ; find other modes (DD*, D s D s, …?)
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Mahalo
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Back-up slides
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c2, c0 << c1 X(3872) production much lower than for other Charmonium states: can set lower limit on B.F. Can measure absolute B.F.’s of B - K - X 0 e + e - B + B - K - X 0 Lower limit on BF(X J/ ) > 4.3% @ 90% C.L 244 fb -1 Very clear J/ and c signals N J/ =258+- 42 N c =266 +-42 c2 c1 c0 J/ Jon Coleman Moriond-QCD March 2005
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M( J/ ) look-back plot
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Fit cos l with 1 ++ MC |cos l | 2 /dof=11.9/9
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