Searching for new forms of hadronic matter Stephen L. Olsen University of Hawai’i & 高能物理所 北京 Wuhan 武汉 10/15/07

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

Hadron “zoo” mesons baryons No “economy”

Constituent Quark Model: 1964 (& 3 antiquarks) Mesons: qq p: u +2/3 p: u -2/3 +:+: d -1/3 u +2/3 d +1/3 u -2/3 d +1//3 u +2/3 -:-: d -1/3 u -2/3 d +1/3 s +1/3 u +2/3 d -1/3 s -1/3 Gell-Mann 3 quarks Zweig Baryons: qqq

Constituent Quark Model: 2007 (& 6 antiquarks) Mesons: qq c:c: c +2/3 c:c: C -2/3  + : s -1/3 s +1/3 c -2/3 u -2/3 b +1//3 u +2/3  - : b -1/3 S =1/3 b +1/3 t -2/3 c +2/3 b -1/3 t +2/3 6 quarks Baryons: qqq u -2/3 d +1/3 s +1/3 u +2/3 d -1/3 s -1/3

Fabulously successful at bringing order to the hadron “zoo” mesons baryons q q q q q “economy”is recovered

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

 s -1/3 three s-quarks in the same quantum state 禁止

The “charge” for the strong force is a 3-dim spinor Y. Nambu O. Greenberg s -1/3 the 3 s -1/3 quarks in the  - have different color charges & evade Pauli -- Each quark can have 3 different “color” charges

QCD: Gauge theory for color charges generalization of QED    + i e A    + i  i G i QED gauge Xform QCD gauge Xform eight 3x3 SU(3) matrices 8 vector fields (gluons) 1 vector field (photon) scalar charge: e triplet charge: erebegerebeg QED QCD Yang Mills Nambu Fritzsch & GellMann

Attractive configurations  ijk e i e j e k i ≠ j ≠ k  ij e i ejej same as the rules for combining colors to get white : add 3 primary colors or add color+complementary color antiquarks:  anticolor charges Hence the name: Quantum Chromodynamics quarks: e i e j e k  color charges ejej eiei ekek

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

Test QCD with 3-jet events (& deep inelastic scattering) rate for 3-jet events should decrease with E cm gluon ss ss  Energy dist

“running”  s Winners of the 2004 Nobel Prize

Running as tests QCD at short distances only  distance The long-distance regime, where the matter we are made of exists, remains untested.

Are there other color-singlet arrangements? Pentaquarks: e.g. an S=+1 baryon (only anti-s quark has S=+1) Glueballs: gluon-gluon color singlet states Multi-quark mesons: qq-gluon hybrid mesons uc u c cc u d u s d Non-quark model states expected in QCD

Spring8 electron Ring in Japan

A pentaquark? T.Nakano et al (LEPS) PRL (2003)  742 citations!!  + (1530)? M(K + n) s +1//3 u +2/3 d -1/3 S=+1 baryon: impossible with only qqq  + n  K - K + n

Experimental situation is messy (some contradictory experiments) SAPHIR (2004) 4.8  M(nK + )(GeV) Counts/4 MeV nKKγp   s CLAS (2005) Same reaction

Some groups contradict themselves 5.2  CLAS-D (2003) no  signal CLAS-D (2005) ??? d+K-K+nd+K-K+n

Pentaquark Scoreboard Positive signals Negative results Also: Belle Compass L3 CLAS Yes: 17 No: 18

Status in 2006 “The conclusion that pentaquarks in general, and the   in particular, do not exist, appears compelling.” - George Trilling LBL

This is a risky business You never know if nature is smiling at you or something else

Another approach: look for non-qq mesons cc uc u c 4 (& 6) quark states “hybrid” qq-gluon states u u u u d d theory: mc 2 >4.2 GeV

The Beijing Electron Positron Collider (BEPC) e+e+ e-e- 高能物理研究所

Beijing Spectrometer (BES)

e + e - annihilation cross section s c b E cm (GeV) q q BES Energy Range

J/    pp C -2//3 c +2/3 p p  u u u u d d

J/    pp This is the  c  pp the J/  ’s well known S=0 partner What is this??? M(pp) GeV BESII J.Z. Bai et al. (BESII) PRL (2003)

Fit the M(pp) distribution Best fit to this peak is a resonance with peak mass below the pp mass threshold M= ± 6.7 MeV/c 2  < 153 MeV/c 2 (90% CL) matches to no known state.

A pp bound state (baryonium)? p npp deuteron: loosely bound 3-q 3-q color singlets with M d = 2m p -  baryonium: loosely bound 3-q 3-q color singlets with M b = 2m p -  ? attractive nuclear force attractive force? There is lots & lots of literature about this possibility

An old idea

Fermi & Yang in 1949 (7 years before p discovery): If NN potential is attractive, they could bind to form  -like states.

Expectation for pp bound state meson m p +m p Above threshold X  pp ~100% below-threshold p and p annihilate to mesons I=0, J PC =0 -+ init. state: pp       ’ is common Ding & Yan Phys.Rev.C72:015208,2005.

BES looked at J/        ’ M(      ’) M=1833 MeV  70MeV m p +m p These values match those for the pp peak (as predicted by Ding&Yan) BESII M. Ablikim et al. (BESII) PRL 95, (2005)

X(1835): a“6-quark” meson? 3 quarks + 3 antiquarks Need to confirm J PC of the      ’ peak is 0 -+ Need to find it in other common 0 -+ pp annihilation channels job for BESIII u u u u d d

Move over to Japan Tsukuba Mountain KEK laboratory KEKB Collider

International Collaboration Belle

e + e - annihilation cross section s c b E cm (GeV) q q KEK B-factory

B meson decays u -2/3 b -1/3 C -2/3 C +2/3 u -2/3 S -1/3 W-W- K-K- “Charmonium”

Primer on Charmonium

Charmonium r mesons formed from c- and c-quarks c-quarks are heavy: m c ~ 1.5 GeV  2m p velocities small: v/c~1/4 non-relativistic QM applies cc

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

“Cornell” potential ~0.1 fm G.S.Bali hep-ph/ “confining” large distance component slope~1GeV/fm 1/r “coulombic” short distance component cc r V(r) 2 parameters: slope & intercept

Charmonium spectrum All of these states are well established J/  ’’ cc c’c’  c   ’’ hchc

Study B  K -     J/  u -2/3 b -1/3 C -2/3 C +2/3 u -2/3 S -1/3 W-W- look here   J  KK

The X(3872) B  K     J/  M(  J  ) – M(J/  )  ’      J/  X(3872)      J/  S.K. Choi et al PRL 91,

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?

The J PC quantum numbers of the X(3872) are 1 ++ From studying different decay processes & angular correlations among decay products

can it be the 1 ++ cc state? 1 ++   c1 ’ (the only charmonium possibility) 3872  X      J/  decay is a forbidden decay (Isospin violating) M=3872 MeV is low,  Allowed E1 transition 2 3 P 1 cc state

Intriguing fact M X3872 = ± 0.5 MeV m D0 + m D0* = ± 0.4 MeV lowest mass charmed meson lowest mass spin=1 charmed meson DD* 2 loosely bound qq color singlets with M = m D + m D* -   u c u c one  exchange attractive for 1 ++ Tornqvist PLB 590, 209 (2004) Braaten et al, PRL 93, Deuson? deuteron-like DD* bound state?

Another old idea DeRujula, Georgi,Glashow, PRL 38, 317 (1977) X(3872)??

X(3872) summary –Existence well established –J PC = 1 ++ –Br(X      J/  ) too high for charmonium –Mass too low for hybrid Four years after discovery, theorists are still puzzling over what it may be

Next, California Stanford Linear Accelerator Ctr BaBar Detector

Radiative return s c b E cm (GeV) GeV  B-factory energies 3~5 GeV

J/  sideband Well above DD & DD* threshold but wide & found in a suppressed mode?? M=4259  8 MeV  = 88  23 MeV B. Aubert et al. (BaBar) PRL (2005) Y(4260) GeV 4.26 GeV not seen in  (e + e -  hadrons) at Ecm =4.26 GeV J.Z. Bai et al. (BESII) PRL BES Y(4260)  (e + e -  hadrons)

a 1 -- cc slot for the Y(4260)? 4260 X.H. Mo et al, hep-ex/ J.Z. Bai et al. (BESII) PRL no cc slot for it!

Theorist’s favorite interpretation cc “hybrid” qq-gluon states just about the right mass for theory

A      ’ peak at 4325MeV Nbkg = 3.1  1.0 Nevt = 68 (<5.7 GeV/c 2 )  2 -prob < 5.7 GeV/c 2 Y(4260) 6.5   (4415)1.2  Y(4320)29% e + e -   ISR      ’ M=4324  24 MeV  = 172  33 MeV S.W.Ye QWG-2006 June 2006 Not Compatible with the Y(4260) D1DD1D D2DD2D 298 fb -1 (BaBar) hep-ex/ BaBar PRL (2007)

New results on the      ’ peak from Belle 548 fb -1 X.L. Wang et al (Belle) arXiv: It is really two peaks! M=4664  11 ± 5 MeV  = 48  15 ± 3 MeV M=4361  9 ± 9 MeV  = 74  15 ± 10 MeV (both relatively narrow) (neither one consistent with 4260) 4260

Need 2 more 1 -- cc slots for Y(4630) & Y(4660) 4260 X.H. Mo et al, hep-ex/ Excited hybrid states? cc

Latest News electrically charged!!

M(  ±  ’) from B  K  ±  ’ K. Abe et al (Belle) arXiv: M(  ’ ) GeV 6.5  M = 4433 ± 4 ±1 MeV  tot = MeV Nsig =124 ± 31evts

Can’t be a cc meson or a hybrid No charged cc hybrid states gluons have zero charge C +2/3 C -2/3

Summary Mesons with no qq assignment: M(pp) GeV X(1835) M(  J  ) – M(J/  ) X(3872)      J/  Y(4260) 548 fb -1 Y(4660) Y(4360) M(  J  ) M(  ’ ) GeV Z ± ( 4430) Y(3940) M(  J/  ) MeV BESII

Concluding remarks A number of “mysterious” mesons that don’t fit into the simple quark model picture have been found If they are related to each other, these particles can’t be the hybrid states predicted by QCD Are these curiosities, each with its own story? … or are they 1 st signs of a spectroscopy of new forms of hadronic matter? Hopefully, time, & more experimentation, will tell

謝謝

Thank you

Back-up slides

Conclusion either: –The constituent quark model for mesons needs major revision or: –There is a new, non-qq, hadron spectroscopy, maybe more than one.

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

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

The LEPS observation of  + (1530) n  K-K- n K+K+  + n  K - K + n M(K + n) s +1//3 u +2/3 d -1/3   (1530) Physical Review Letters, 91, (2003)  + n  K -  +  K - K + n S=+1

Charmonium state?  (e + e -  hadrons) No sign of it  (e + e -  hadrons) at Ecm =4.26 GeV BES 4260 J.Z. Bai et al. (BESII) PRL No place for it!

Actual fit M= ± 6.7 MeV/c 2  < 153 MeV/c 2 (90% CL) J/    pp in the BES expt  2 /dof=56/56 fitted peak location

A pp bound state (baryonium)? p npp deuteron: loosely bound 3-q 3-q color singlets with M d = 2m p -  baryonium: loosely bound 3-q 3-q color singlets with M b = 2m p -  ? attractive nuclear force attractive force? There is lots & lots of literature about this possibility E. Fermi, C.N. Yang, Phys. Rev. 76, 1739 (1949) Y.Nambu, G. Jona-Lasinio Phys Rev 122, 345 (1961) … I.S. Shapiro, Phys. Rept. 35, 129 (1978) C.B. Dover, M. Goldhaber, PRD 15, 1997 (1977) … A.Datta, P.J. O’Donnell, PLB 567, 273 (2003)] M.L. Yan et al., hep-ph/ B. Loiseau et al., hep-ph/ … These are very famous papers !!!

The X(3872) ???? Study     J/  produced in B  K     J/  decays

hadronic molecules a new spectroscopy? may be more particles to find

summary X(1835): – Existence well established – J PC = 0 -+ – Br(X  pp) too high for qq meson – X       ’ is expected for sub-thresh pp state

ll |cos  l  |  2 /dof = 34/9  |cos  | |cos  |  2 /dof=34/ rule out 0 ++ & 0 -+     J  k    x  J   Ruled out by Belle

C=+1 is established X(3872)   J/  seen in: & Belle PRL M(  looks like a  X(3872)  ”  ”J/  seen CDF Belle hep-ex/

Angular analysis from CDF CDF Collab. PRL 98, (2007) 1 ++ or 2 -+

Use Angular Correlations to determine J & P K  J/         e  e   J=0 X 3872 J z =0 z Rosner (PRD ) Bugg (PRD ) Suzuki, Pakvasa (PLB )

Possible J PC values 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 ++

X(3872) = D 0 D* 0 bound state? J PC = 1 ++ is favored M ≈ m D0 + m D0* Large isospin violation is natural ( & was predicted) :  |D 0 D* 0 > = 1/  2 (|10> - |00>)  (X   J/  ) <  (X   J/  ) was predicted  (X  D 0 D 0  0 ) too large? Bf(B 0  K 0 X 3872 )/Bf(B +  K + X 3872 ) too large? Equal mixture of I=1 & I =0 Swanson PLB 598, 197 (2004) Tornqvist PLB 590, 209 (2004) Swanson PLB 588, 189 (2004) Braaten & Kusunoki PR D71, predict: < 0.08 BaBar measurement (hep-ex/ ): 0.5  0.3

Y(3940) in B  K  J/  M≈3940 ± 11 MeV  ≈ 92 ± 24 MeV Belle PRL94, (2005) M(  J/  ) MeV M 2 (K  ) GeV 2 M 2 (  J  ) GeV 2

If not charmonium, what? cc “hybrid” cc-gluon state? But why does it decay to     J/ , and not to D and D* mesons?

Y(4260) summary – Existence well established – J PC = 1 -- –  (X      J/  ) too high for charmonium – Br(X  D ( * ) D ( * ) ) too low for hybrid Another mystery!!

J/    pp C -2//3 c +2/3 u +2/3 u -2/3 d -1/3 u +2/3 d +1/3 u -2/3 p p 