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

test of QCD: “running”  s

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

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)

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

Is the X(3872) non-standard? B  K     J/  M(  J  ) –M(J/  )  ’      J/  X(3872)      J/ 

Its existence is well established seen in 4 experiments X(3872) CDF X(3872) D0 hep-ex/  11.6 

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

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/

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

J PC possibilities (for J ≤ 2) 0 -- exotic violates parity 0 -+ (  c ” ) 0 ++ DD allowed (  c0 ’ ) 0 +- exotic DD allowed DD allowed (  (3S)) 1 -+ exotic DD allowed 1 ++ (  c1 ’ ) 1 +- (h c ’ ) 2- -(2)2- -(2) (  c2 ) 2 ++ DD allowed  c2 ’ ) 2 +- exotic DD allowed

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 DD allowed (  (3S)) 1 -+ exotic DD allowed 1 ++ (  c1 ’ ) 1 +- (h c ’ ) 2- -(2)2- -(2) (  c2 ) 2 ++ DD allowed  c2 ’ ) 2 +- exotic DD allowed

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

Search for X(3872)   J/ 

Kinematic variables CM energy difference: Beam-constrained mass:  B  K  J  B  K  J  B   B ϒ (4S) E cm /2 ee ee M bc EE

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

Evidence for X(3872)        J/   reported last summer hep-ex/ ) 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)?

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

J PC possibilities (C=-1 ruled out) 0 -- exotic Violates parity 0 -+ (  c ” ) 0 ++ DD allowed (  c0 ’ ) 0 +- exotic DD allowed DD allowed (  (3S)) 1 -+ exotic DD allowed 1 ++ (  c1 ’ ) 1 +- (h c ’ ) (  2 ) (  c2 ) 2 ++ DD allowed  c2 ’ ) 2 +- exotic DD allowed

Angular Correlations K  J/  J=0 X 3872 J z =0 z Rosner (PRD ) Bugg (PRD ) Suzuki, Pakvasa (PLB )

Use 253 fb -1  ~275M BB prs exploit the excellent S/N Signal (47 ev) Sidebands (114/10 = 11.4 ev) X       J/   ’      J/ 

0 ++ ll 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

: sin 2  sin 2  safe to rule out 0 -+   |cos  | |cos  |  2 /dof=34/9  2 /dof=18/9

1 ++ ll  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

J PC possibilities (0 -+ & 0 ++ ruled out) 0 -- exotic violates parity 0 -+ (  c ” ) 0 ++ DD allowed (  c0 ’ ) 0 +- exotic DD allowed DD allowed (  (3S)) 1 -+ exotic DD allowed 1 ++ (  c1 ’ ) 1 +- (h c ’ ) (  2 ) (  c2 ) 2 ++ DD allowed  c2 ’ ) 2 +- exotic DD allowed

Fits to the M(  ) Distribution X   J/  has a q* (2l+1) centrifugal barrier X J/   q*

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

Possible J PC values (J -+ ruled out) 0 -- exotic violates parity 0 -+ (  c ” ) 0 ++ DD allowed (  c0 ’ ) 0 +- exotic DD allowed DD allowed (  (3S)) 1 -+ exotic DD allowed 1 ++ (  c1 ’ ) 1 +- (h c ’ ) (  2 ) (  c2 ) 2 ++ DD allowed  c2 ’ ) 2 +- exotic DD allowed

Search for X(3872)  D 0 D 0  0

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 )

X(3872)  DD  rules out : DD* in an S-wave  q* 2 ++ : DD  in a D-wave  q* 5 Strong threshold suppression

Possible J PC values (2 ++ ruled out) 0 -- exotic violates parity 0 -+ (  c ” ) 0 ++ DD allowed (  c0 ’ ) 0 +- exotic DD allowed DD allowed (  (3S)) 1 -+ exotic DD allowed 1 ++ (  c1 ’ ) 1 +- (h c ’ ) (  2 ) (  c2 ) 2 ++ DD allowed  c2 ’ ) 2 +- exotic DD allowed 1 ++

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%   (  c1 ’   J/  ) /  (  c1 ’   J/  ) Expect: ~ 40  ( X 3872   J/  ) /  ( X 3872   J/  ) Measure: 0.14 ± 0.05  c1 ’ component of X(3872) is ≤few %

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 X(3872) is very near DD* threshold. is it somehow related to that?

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/ u c u c

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)

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

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/ 

B  K  J/  in Belle “Y(3940)” M≈3940 ± 11 MeV  ≈ 92 ± 24 MeV M bc S.K. Choi et al hep-ex/ to appear in PRL

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/

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, M(  J/  )

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 (1974) + (many) others

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, …?)

Mahalo

Back-up slides

 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/  ) > 90% C.L 244 fb -1 Very clear J/  and  c signals N J/  = N  c =  c2  c1  c0 J/  Jon Coleman Moriond-QCD March 2005

M(  J/  ) look-back plot

Fit cos  l  with 1 ++ MC |cos  l  |  2 /dof=11.9/9