Homeless mesons Stephen L Olsen University of Hawaii

Homeless mesons Stephen L. Olsen University of Hawai’i X 38 72 Y 4260 Y 3940

History: (sub-atomic particles) 1932: proton & neutron. . all we need? ? ? Joliet-Curie 1937: muon “Who ordered that? ” Rabi 1947: pion predicted in 1935 Yukawa Fermi 1950’s: , , , … “Had I foreseen that, I would have gone into botany” – Fermi Peters Jones Ting chadwick

Hadron “zoo” mesons baryons

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

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

W- s-1/3 three s-quarks in the same quantum state Das ist verboten!!

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

QCD: Gauge theory for color charges Yang Mills QED Nambu Fritzsch & Gell. Mann generalization of QED scalar charge: e QCD isotriplet charge: QED gauge Xform +ie. A 1 vector field (photon) er eb eg QCD gauge Xform + i a li Gi eight 3 x 3 SU(3) matrices 8 vector fields (gluons)

Attractive configurations eijk eiejek i≠ j≠k dij ei ej same as the rules for combining colors to get white: add 3 primary colors or add color+complementary color quarks: eiejek color charges antiquarks: ei ej ek anticolor charges Hence the name: Quantum Chromodynamics

Difference between QED & QCD QED: photons have no charge QCD: gluons carry color charges gluons interact with each other a Coupling strengths distance

Test QCD with 3 -jet events (& deep inelastic scattering) as gluon rate for 3 -jet events should decrease with Ecm

“running” as Why are these people smiling?

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

Pentaquarks “Seen” in many experiments but not seen in just as many others Belle BES Ba. Bar CDF High interest: 1 st pentaquark paper has ~500 citations

Experimental situation is messy (some contradictory experiments) + ® γp Ks K n Counts/4 Me. V SAPHIR (2004) 4. 8 CLAS (2005) Same reaction M(n. K+)(Ge. V)

Some groups contradict themselves CLAS-D (2003) CLAS (2005) 5. 2 ? ? ? no signal

Pentaquark Scoreboard Positive signals Negative results Also: Belle Compass L 3 CLAS Yes: 17 No: 18

Plenary speaker at LP 05 Volker D Burkert Jefferson Lab “The Q pentaquark is not in good health, but it is still alive. ” -

This talk: non-standard mesons u c c u with “hidden charm” (i. e containing c & c) c c • standard cc mesons are: – best understood theoretically – narrow & non overlapping • c + c systems are commonly produced in B meson decays. c Vcb c b W- cosq. C CKM favored s

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

Primer on Charmonium

Charmonium mesons formed from c- and c-quarks c r c c-quarks are heavy: mc ~ 1. 5 Ge. V 2 mp velocities small: v/c~1/4 non-relativistic QM applies

QM of cc mesons c r c What is V(r) ? ? derive from QCD quantum chromodynamics

“Cornell” potential c r ~0. 1 fm c slope~1 Ge. V/fm “confining” large distance component V(r) G. S. Bali hep-ph/0010032 2 parameters: slope & intercept 1/r “coulombic” short distance component

Charmonium spectrum

1 -- Charmonium states Directly accessible via e+e- annihilation e+ e- J/ ’ (e+e- hadrons) ” “narrow” “wide” (G~300 Ke. V) (G~100 Ke. V) (G~25 Me. V) D-meson + anti-D meson mass threshold ” DD decay channel is open G(DD) 25 Me. V

P-wave states Gamma energy spectrum from ’ g X decays accessible via E 1 transitions from ’ Gaiser et al (Crystal Ball) PRD 34 711 E 1 Transition Partial width G ” ke. V 23 S 1 ( ’) 13 P 2 (cc 2) les 17 ts p i n c e in rem prc 1 23 S 1 ( ’) 13 Pst 1 (c a)su 24 ke. V 1 ” e rom 3 ith m f 3 2 Sb 1 le( ’) 1 24 ke. V w P 0 (cc 0) t a n cul eeme l a C r 3 g. P (c ) 13 S (J/ ) a 1 420 ke. V 2 c 2 1 ood 13 P 1 (cc 1) 13 S 1(J/ ) 290 ke. V 13 P 0 (cc 0) 13 S 1(J/ ) 120 ke. V

Hadronic transitions G( ’ + -J/ ) 70 ke. V n ee w t be t en eory m + G( ” gre e J/ ) ke. V th 50 155 & a 1 nt PRD 4 e” l “allowed” e b na urem Yan o s a as ang & e e r “ m. Ku G( ’ h. J/ ) 5 ke. V “allowed” c. f SUF(3) violating +0 h G( ’ 0 J/ ) 0. 3 ke. V isospin violating

Recent results 21 S 0 found by Belle S. K. Choi et al PRL 89 102001 properties as expected 23 P 2 found by Belle hep-ex/0507033 properties as expected 11 P 1 found by CLEO hep-ex/0508037 properties as expected 13 D 1 g 13 P 1 seen by CLEO hep-ex/0509030 G(meas) = 75 18 ke. V G(theor) 59~77 ke. V

The potential model for cc charmonium mesons is robust and reliable

The X(3872) Study + -J/ produced in B K + - J/ decays ? ?

The X(3872) B K + -J/ ’ + -J/ X(3872) + -J/ S. K. Choi et al PRL 91, 262001 M( J/ )

Its existence is well established seen in 4 experiments CDF 9. 4 11. 6 X(3872) D 0 X(3872)

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

no obvious cc assignment 3872 hc ” M too low and G too small hc’ angular dist’n rules out 1+- cc 1’ G(g. J/ ) way too small 2 G(gcc 1) too small; M( + -) wrong h 2 hc should dominate 3 G( gcc 2 & DD) too small SLO hep-ex/0407033

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

PC J possibilities (for J ≤ 2) -0 -+ 0 +0 exotic violates parity (hc”) DD allowed exotic DD allowed 1 -+ 1 +1 DD allowed ( (3 S)) exotic DD allowed (cc 1’) (hc’) 2 ++ 2 +2 ( 2) (hc 2) DD allowed exotic DD allowed (cc 0’) (cc 2’)

JPC possibilities 0 -- ruled out; JP=0+, 1 - & 2+ unlikely 0 -- -+ 0 +0 (hc”) DD allowed exotic DD allowed 1 -+ 1 +1 DD allowed ( (3 S)) exotic DD allowed (cc 1’) (hc’) 2 ++ 2 +2 ( 2) (hc 2) DD allowed exotic violates parity (cc 0’) (cc 2’)

Strong evidence for C=+1 X(3872) g. J/ X(3872) + - 0 J/ virtual w(782)? M( + - 0) 13. 6 ± 4. 4 X(3872) g. J/ evts (>4 significance) Bf(X g. J/ ) Bf(X J/ ) Br(X 3 J/ ) Br(X 2 J/ ) = 1. 0 ± 0. 5 X(3872) + -J/ =0. 14 ± 0. 05 Fits to (760) M( + -)

JPC possibilities (C=-1 ruled out) 0 -exotic Violates parity 1 - DD allowed ( (3 S)) 2 - - ( 2) -+ 0 ++ 0 (hc”) DD allowed 0+exotic DD allowed (cc 0’) -+ 1 ++ 1 exotic DD allowed (cc 1’) + 2 ++ 2 (hc 2) DD allowed (cc 2’) 1+(hc’) 2+exotic DD allowed

Angular Correlations + z Rosner (PRD 70 094023) Bugg (PRD 71 016006) Suzuki, Pakvasa (PLB 579 67) Jz=0 X 3872 J=0 K J/ m+m- (e+e-)

0++ e e. J/ 0 -+ k (e xe. J/ ) ql c 2/dof=34/9 c 2/dof = 34/9 |cosq| |cosql | rule out 0++ & 0 -+ |cos |

JPC possibilities (0 -+ & 0++ ruled out) 0 -exotic violates parity 1 - - DD allowed ( (3 S)) 2 - ( 2) 0+- 0 -+ 0++ (hc”) DD allowed (cc 0’) exotic DD allowed -+ 1 ++ 1 1+- exotic DD allowed (cc 1’) + 2 ++ 2 (hc 2) DD allowed (cc 2’) (hc’) 2+exotic DD allowed

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

M( ) can distinguish -J/ S- & P-waves S-wave: c 2/dof = 43/39 (CL= 28%) P-wave: c 2/dof = 71/39 (CL=0. 1%) q* roll-off Shape of M( ) distribution near the kinematic limit favors S-wave q*3 roll-off

Possible JPC values (J-+ ruled out) 0 -exotic violates parity 0 -+ (hc”) 1 - - 1 -+ DD allowed ( (3 S)) exotic DD allowed 2 - ( 2) 2 - + (hc 2) 0++ DD allowed (cc 0’) ++ 1 0+exotic DD allowed 1+(hc’) (cc 1’) ++ 2 DD allowed (cc 2’) 2+exotic DD allowed

0 0 0 X(3872) D D ? D*0 D 0 0? • 1++ : DD* in an S-wave q* • 2++ : DD in a D-wave q*5 Strong threshold suppression M(D 0 D 0 0) 11. 3± 3. 6 sig. evts (>4 ) Bf(B KX)Bf(X DD )=2. 2± 0. 7± 0. 4 x 10 -4

Possible JPC values (2++ ruled out) 0 -- 0+- exotic violates parity 0 -+ 0++ (hc”) DD allowed 1 - - 1 -+ DD allowed ( (3 S)) exotic DD allowed ++ 1 (hc’) 2 - ( 2) 2 - + (hc 2) 2++ 2+- DD allowed exotic DD allowed (cc 0’) ++ 1 (cc 1’) (cc 2’) exotic DD allowed 1+-

can it be a ++ 1 cc state? 1++ cc 1’ (the only possibility) 3872 M=3872 Me. V is too low, especially now that we know that M(cc 2’)=3931 4 Me. V Bf(X + - J/ )>4% + (Isospin violating) is very large for an isospin-violating channel

Expectations for c’c 1 G(c’c 1 g J/ ) 11 ke. V Barnes Godfrey PRD 69 054008 G(c’c 1 + - J/ ) = G( ’ ? 0 J/ ) 0. 3 ke. V (“educated” guess? ) Expect: Meas: Bf(X g. J/ ) Bf(X J/ ) 30 ~ 40 >200 x discrepancy =0. 14 ± 0. 05 can our “education” really be this bad? cc 1’ component of X(3872) is few% (at most? )

Intriguing fact MX 3872 =3872 ± 0. 6 ± 0. 5 Me. V m. D 0 + m D 0* = 3871. 2 ± 1. 0 Me. V lowest mass spin=1 charmed meson Deuson? deuteron-like DD* bound state? c Du c D*u one exchange attractive for 1++ 2 loosely bound qq color singlets with M = m. D + m. D* - d Tornqvist PLB 590, 209 (2004)

X(3872) = D 0 D*0 bound state? • JPC = 1++ is favored • M ≈ m. D 0 + m. D 0* Tornqvist PLB 590, 209 (2004) • Large isospin violation is natural (& |D 0 D*0> = 1/ 2(|10> was predicted): - |00>) Equal mixture of I=1 & I =0 Swanson PLB 588, 189 (2004) • G(X g. J/ ) < G(X J/ ) was predicted • G(X D 0 D 0 0) too large? Swanson PLB 598, 197 (2004) • Bf(B 0 K 0 X 3872)/Bf(B+ K+X 3872) too large? Braaten & Kusunoki PR D 71, 074005 predict: Ba. Bar measurement (hep-ex/0507090): <0. 08 0. 5 0. 3

diquark-antidiquark? Maiani etal predict a doublet of states PRD 71, 014028 (2005) X u= u c c u B+ K+Xu Ba. Bar X d= d c c d B 0 K 0 Xd Ba. Bar Maiani et al predict: DM = M(Xu) – M(Xd) = 8 3 Me. V Ba. Bar (hep-ex/0507090) reports: DM = 2. 7 1. 3 0. 2 Me. V

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 h J/ B K w J/

B K w. J/ in Belle “Y(3940)” M≈3940 ± 11 Me. V G≈ 92 ± 24 Me. V Mbc Mbc M(w. J/ ) Me. V S. K. Choi & S. L. Olsen et al. (Belle), PRL 94, 182002 (2005)

Y(3940): What is it? • Charmonium? eg. Brambilla et al (QWG) hep-ph/0412158 – Conventional wisdom: (SU(3)-violating) w. J/ decay should not be a discovery mode for a cc state with mass above DD & DD* threshold! • cc-gluon hybrid? – predicted by QCD, Horn & Mandula PRD 17 898 – decays to DD and DD* are suppressed (“open-charm” thresh = m. D + m D** = 4. 3 Ge. V) – large hadron+J/ widths can occur – masses expected to be 4. 3 ~ 4. 4 Ge. V (higher than what we see) others

Ba. Bar’s Y(4260) 10. 58 Ge. V 4. 26 Ge. V M=4259 8 Me. V G = 88 23 Me. V Y(4260) J/ sideband B. Aubert et al. (Ba. Bar) hep-ph/0506081 (e+e- hadrons) not seen in (e+e- hadrons) at Ecm =4. 26 Ge. V BES J. Z. Bai et al. (BESII) PRL 88 101802 Well above DD & DD* threshold but wide & found in a suppressed mode? ?

summary • X(3872): of r o t c – Existence well established a fa n 200! y ha t b re – JPC = 1++ mo – Br(X + - J/ ) too high for charmonium – Br(X D 0 D 0 0) too high for molecule – Br(B 0 KSX 3872) also too high for molecule(? ) – DM too small for diquarks? still under study (M(Xu) (from B+ K+Xu) - M(Xd) (from B 0 KSXd) – Mass too low for hybrid The more we learn more about it the more puzzling it becomes.

other odd-balls • Y(3940) Belle – G( Y 3940 w. J/ ) too high for charmonium – Mass too low for a hybrid by factors of ~103 • Y(4260) Ba. Bar – G(y 4260 + -J/ ) also way too high – 1 --, but not seen in e+e- hadrons

Looking for a home: Isospin violators not welcome Fussy! 3872 Charmonium chalet Y 3940 Y 4260

Molecule Manors rats! DD 3872 Y 3940 Y 4260

M<4. 2 Ge. V need not apply Fat Cats! 3872 Hydrid heaven Y 394 0 Y 4260

*#!? &%$! Doublets only no singlets! 3872 Diquark dives Y 4260 Y 3940

Conclusion • either: – The “standard model” for charmonium mesons needs major revision • or: – There is a new hadron spectroscopy in the 3. 5~4. 5 Ge. V mass region Opportunities for CLEO-c & BES-III ? ? ?

Back-up slides

Xu – Xd Mass difference? : Belle: MXu – M ’ = 185. 7 0. 6 Me. V m i l e in y r a r P MXd – M ’ = 184. 0 1. 3 Me. V M(Xu) – M(Xd) = 0. 8 1. 4 Me. V

Another one? • e+e- J/ + X >4 )peak at M=3940 11 Me. V N=148 33 evts Width consistent w/ resolution (= 32 Me. V) What is it? c‘c 0 ? h‘c hc cc 0 h‘c h“c ? ?

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

( ) Look at M(DD * ) 3940 Me. V DD* 9. 9 ± 3. 3 evts (4. 5 ) cc 0 ‘ DD* DD 4. 1 ± 2. 2 evts (2. 1 ) h“c DD

Other hadronium states? fitted peak location J/ gpp in the BES expt J. Z. Bai PRL 91, 022001(2003) +3 +5 M=1859 -10 -25 Me. V/c 2 G < 30 Me. V/c 2 (90% CL) c 2/dof=56/56 0 0. 1 0. 2 M(pp)-2 mp (Ge. V) 0. 3 acceptance