11/26/2010 ICHEP 2008 1

Light Hadron Spectroscopy and

Charmonium

ICHEP 2008Philadelphia, Pennslyvania

July 29 – Aug. 5, 2008

Frederick A. HarrisBESUniversity of Hawaii

11/26/2010 ICHEP 2008 2

Ben Franklin (1706 – 1790)• A Great American:founding father, founder of the

University of Pennsylvania, author, printer, inventor, statesman, diplomat, scientist, …

“Beer is living proof that God loves us and wants us to be happy.”

“All wars are follies, very expensive and very mischievous ones. “

“An investment in knowledge pays the best interest.”

“They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.”

11/26/2010 ICHEP 2008 3

OUTLINEIntroduction“Classical” charmoniumY(2175)Belle 2γISR at BaBarAnomalous hadronic line shape around ψ(3770)BEPCII and BESIIISummary

Apology: There are too many results to cover in a shorttalk. I apologize to everyone for all the topics that I donot cover.

11/26/2010 ICHEP 2008 4

Charmonium Spectroscopy• Galina Pakhlova covered exotic cc states

(X, Y, Z, etc.)• I will cover “classic charmonium”; much

progress from BES, CLEOc, B-factories, etc. Much from CLEOc this year.

• Importance of charmonium:– Provide detailed information on QCD in

the perturbative and non-perturbativeregions.

– Provide laboratory for precision tests of lattice QCD and effective field theory calculations.

Thanks to:Chengping ShenXiaoyan Shen

Selina LiRyan Mitchell –see his reviewtalk oncharmonium.

11/26/2010 ICHEP 2008 5

Charmonium spectrum below open charm

Only J/ψ and ψ′ produced directly in e+ e- collisions, but statesbelow ψ′ produced through radiative and hadronic transitions.

11/26/2010 ICHEP 2008 6

Important Processes• e+e- annihilation

• B decay

• ISR • e+e- radiate one or more photons.• Measure σ over range of energies.

• 2 photon• even spin mesons• anti glueball filter.

c

c

e+

e-

High luminosities at B factories allowuse of ISR and 2 photon processes.

b

q

cc

sB

(*)Kq

W

ce-

e-e+ c

11/26/2010 ICHEP 2008 7

BESII(1996 – 2004)

(2003 – 2008)

Belle (1998 - )

CLEOc

(1998 - 2008)

e+e- Excellent photon resolution.

11/26/2010 ICHEP 2008 8

CLEOc: Ψ(2S) → J/Ψ transitions• 27 M Ψ(2S) events obtained in 2006.• Use J/Ψ→ ee, μμ to identify J/Ψ• example Ψ(2S) → ππ J/Ψ, J/Ψ→ ee, μμ

π+π-

πoπo

11/26/2010 ICHEP 2008 9

CLEOc: Ψ(2S) → J/Ψ transitionsChannel B(%) CLEOc B(%) PDG07π+π-J/Ψ 35.04 ± 0.07 ± 0.77 32.3 ± 0.9πoπoJ/Ψ 17.69 ± 0.08 ± 0.53 16.68 ± 0.34ηJ/Ψ 3.43 ± 0.04 ± 0.09 3.13 ± 0.08πoJ/Ψ 0.133 ± 0.008 ± 0.003 0.126 ± 0.0013γ(χc0 → γJ/Ψ) 0.125 ± 0.007 ± 0.013 0.122 ± 0.010γ(χc1 → γJ/Ψ) 3.56 ± 0.03 ± 0.12 3.14 ± 0.08γ(χc2 → γJ/Ψ) 1.95 ± 0.02 ± 0.07 1.64 ± 0.04any + J/Ψ 62.54 ± 0.16 ± 1.55 56.9 ± 0.9χc0 → γJ/Ψ 1.35 ± 0.07 ± 0.14 ± 0.06 1.32±0.11χc1 → γJ/Ψ 40.5 ± 0.3 ± 1.4 ± 1.8 35.9±1.9

χc2 → γJ/Ψ 24.1 ± 0.2 ± 0.9 ± 1.2 20.3±1.0

H. Mendes et al., PRD 78, 011102 (2008).

11/26/2010 ICHEP 2008 10

ηc ProblemPrecise measurement of ηc mass provides information on the hyperfine (spin-spin) splitting of ηc and J/Ψ.

Γtot(ηc)even worse!M(ηc) status

For Ψ(1S,2S) → γηc, average = 2977.3 ± 1.3 MeV/c2.For γγ or pp production, average = 2982.6 ± 1.0 MeV/c2.3 σ difference.

PDG06 PDG06

11/26/2010 ICHEP 2008 11

ηC

PDG: 1.27 ± 0.36%

• Magnetic dipole transitions (M1).• Important to check recent lattice QCD.• Important for normalizing ηc BRs.

J/Ψ and Ψ(2S) → γηc important:

Recent Lattice QCD results[Dudek et al., PRD73, 07450 (2006)]

Br(J/Ψ γηc) is off too!

Γγηc = (2.0 ± 0.1 ± 0.4) keVorB(J/Ψ → γηc ) = (2.1 ± 0.1 ± 0.4) %

ηc Problem

11/26/2010 ICHEP 2008 12

CLEOc: J/Ψ and Ψ(2S) → γηc• 24.5 M Ψ(2S) decays.• Use 12 ηc exclusive decays

to determine γ line shape inJ/Ψ → γηc.

• Shape can not be explained by simple BW + resolution.

• Use empirical form.• Uncertainty prohibits

precision mass and width measurements.

• May explain 3σ difference with mass from γγ fusion and p-pbar annihilation.

ExclusiveJ/Ψ → γηc

Xi = 2(π+π-), 3(π+π-),2(π+π-πo), π±K- Ko

S, etc.+

Exclusive:Ψ(2S) → π+ π- J/Ψ;J/Ψ → γηc; ηc → Xi

11/26/2010 ICHEP 2008 13

CLEOc: J/Ψ and Ψ(2S) → γηc• Measure 3 samples:

1. Ψ(2S) → γηc inclusive2. Ψ(2S) → π+ π- J/Ψ; J/Ψ → γηc; ηc → Xi3. Ψ(2S) → γηc; ηc → Xi

EXCSN1EXCSN 2

INCSN 2

Will affect all ηc branching ratios.B(1S) now agrees with Lattice QCD: arXiv:0805.0252 [hep-ex];

submitted to PRL

)2(2

2))2((S

INCS

INCS

c NN

SBψε

ηγψ =→

CLEOc PDGB(Ψ(2S) → γηc) (4.32 ± 0.16 ± 0.60) x 10-3 (2.6 ± 0.4) x 10-3

B(J/Ψ → γηc) (1.98 ± 0.09 ± 0.30) % (1.3 ±0.4) %

ππεεηγψηγψ

BNN

SBJB

EXCS

EXCS

EXCS

EXCS

c

c

)/())2(()/(

212

1=→→

B(J/Ψ → γηc ) = 2.1 ± 0.1 ± 0.4) %

11/26/2010 ICHEP 2008 14

CLEOc: J/Ψ and Ψ(2S) → γηc

If CLEOc fits mass:M(ηc) = 2976.7 ± 0.6 MeV/c2 (unmodified BW)M(ηc) = 2982.2 ± 0.6 MeV/c2 (modified BW according to line shape. )

Understanding the energy dependence of theΨ(1S, 2S) → γηc matrix element is crucial forunderstanding radiative decays.

arXiv:0805.0252 [hep-ex]; submitted to PRL

11/26/2010 ICHEP 2008 15

From Christine Davies’ talk

Expect for 3 MeV/c2 shift?latt/expt ≈ 116/119 = 0.97

11/26/2010 ICHEP 2008 16

CLEOc: Mass of hc(1P1)• 1st seen by E835

and CLEO in 2005• 25 M Ψ(2S) events

Inclusive

• Exclusive: reconstruct15 ηc hadronic decays.

M(hC) = 3525.28 ± 0.19 ± 0.12 MeV/c2

tag with hc → γηc photon

11/26/2010 ICHEP 2008 17

CLEOc: Mass of hc(1P1)

M(hC)AVG = 3525.20 ± 0.18 ± 0.12 MeV/c2

(B1 x B2)AVG = (4.16 ± 0.30 ± 0.37) x 10-4

Combining with earlier results:

Using the spin weighted centroid of 3PJ states, <M(3PJ)>, to represent M(3PJ): ΔMhf(1P) = <M(3PJ)> - M(1P1) = +0.08 ±0.18 ± 0.12 MeVConsistent with lowest order expectation of 0.

M(hC)AVG important to learn about hyperfine (spin-spin) interaction of P wave states.

arXiv:0805.4599 [hep-ex]; submitted to PRL

11/26/2010 ICHEP 2008 18

CLEOc: χcJ → γ γ• χcJ(3pJ) → γγ (QCD)

analogous to triplet decays of positronium (QED).

• For R = Γ(3p2 → γγ)/Γ(3p0 →γγ), even differences due to different masses and wave functions cancel and for both

R = 4/15 ≈ 0.27.(V. A. Novikov et al., Phys. Rep. 41, (1978).

• Departures are from strong radiative corrections and relativistic effects.

Potential model predictions:

24.5 M Ψ(2S) events.E(γ1) (MeV)

Ψ(2S) → γ1χcJ, χcJ → γ2γ3Ψ(2S) → γ1χc1 forbidden by Landau-Yang Theorem

11/26/2010 ICHEP 2008 19

CLEOc: χcJ → γ γ

• For αS = 0.32,RTh = (4/15)[1-1.76 αS] = 0.12(Voloshin:hep-ph/0711.4556)

• Confirms inadequacy of 1st

order radiative corrections.

<R> = 0.20 ± 0.02Average with previous experiments:

Γγγ(χc0) = 2.53±0.37±0.11±0.24 keVΓγγ(χc2) = 0.60±0.06±0.03±0.05 keVR = 0.237±0.043±0.015±0.031

Belle γγ → χc0,2

Measure Γγγx B(χc0,2 → X)and divide by known BRs.

Belle: arXiv:0706.3955, EPJ C53,1 (2008).

arXiv:0803.2869 [hep-ex]submitted to PRL

11/26/2010 ICHEP 2008 20The Y(2175)

11/26/2010 ICHEP 2008 21

• A structure at 2175MeV was observed in

e+e- γ ISR φf0(980), e+e- γISR K+K-f0(980)

MeV201658MeV15102175

±±=Γ±±=M

Observation of a new 1-- resonance Y(2175) at BaBar

Phys. Rev. D 74 (2006) 091103(R)

Y(2175)

6.2 σ

Speculation: may be ss-bar version of Y(4260) since 1--

and similar decay. [BaBar PRL95, 142001 (2005).]

11/26/2010 ICHEP 2008 22

J/ψ → ηφf0(980)

η

φ

f0(980)

Final states: η γγ, φ K+K-, f0(980) π+π-

Define η, φ, f0(980) signal and sideband regions.

BESII58 M J/ψ

Y(2175)

11/26/2010 ICHEP 2008 23

0

5

10

15

1.9 2 2.1 2.2 2.3 2.4 2.5 2.6

EntriesMean

152 2.262

M(φf0(980))(GeV/c2)

even

ts/20

MeV

M(φf0(980)) GeV/c2

0

0.01

0.02

0.03

0.04

1.9 2 2.1 2.2 2.3 2.4 2.5

EntriesMean

468140 2.313

35.63 / 25P1 -1.960 0.1958E-02P2 2.011 0.1130E-02P3 -0.4012 0.5356E-03P4 -0.1461 0.2239E-03P5 0.4498E-01 0.7800E-04

M(φf0(980))(GeV/c2)

ε%

efficiency curve

phase space

0

5

10

15

1.9 2 2.1 2.2 2.3 2.4 2.5 2.6

EntriesMean

152 2.262

m(φf0(980))(GeV/c2)

even

ts/20

MeV

A peak around 2175 MeV/c2 is observed.

Backgrounds from sideband estimation

BESII J/ψ → ηφf0(980) Y(2175)

11/26/2010 ICHEP 2008 24

Fit with one resonance:5.5 σ

M(φf0(980)) GeV/c2

Simultaneous fit to signal and sideband events withBW +p3

BESII J/ψ → ηφf0(980) Y(2175)

Note:Fitting two peaks does notchange mass or width.

Mass (GeV/c2) Width (GeV/c2)

BES 2.186±0.010±0.006 0.065±0.023±0.017

BABAR 2.175±0.010±0.015 0.058±0.016±0.020

40

0

10)73.075.023.3())980((

))980()2175(())2175(/(−−+ ×±±=→

•→•→

ππ

ϕηψ

fB

fYBYJB

11/26/2010 ICHEP 2008 25

Y(2175)e+e- γISR φf0(980) → γISR KKππlum = 673 fb-1 preliminary

φ fo

φ(1680)

11/26/2010 ICHEP 2008 26

M(Y(2175))=(2133 +69-115) MeV/c2,

Γ(Y(2175))=(169 +105-92) MeV/c2.

M(φ(1680))=(1687 ± 21) MeV/c2 ,Γ(φ(1680))= (212 ± 29) MeV/c2

■ Fit with one BW interfering with a non-resonant as used by Babar’s (PRD 74, 091103(R), 2006).

Y(2175)

■ Fit to with two BWs interfering with a non-resonant. 2.0σ significanceFinal Results: Take simple average of fits and enlarge errors:

preliminaryarxiv:0808.0006 [hep-ex]

φf0(980)

★★ φ(1680) : First observed byDM1 25 years ago. Recently by BaBar in e+e- → φ η and K*K ISR modes (PRD77, 092002).

e+e- γISR φf0(980) → γISR KKππ

11/26/2010 ICHEP 2008 27

What is Y(2175)?Many theoretical interpretations:

An ss analogue of Y(4260).A ssg hybrid [G.J. Ding and M.L. Yan, PLB 650, 390 (2007)].A 23 D1 ss state [G.J. Ding and M.L. Yan, PLB 657, 49 (2007)].A ssss tetraquark state [Z.G. Wang, Nucl. Phys. A791, 106 (2007)].A ΛΛ bound state [E. Klempt, A. Zaitsev, Phys. Rep.454, 1 (2007)].A conventional ss state?

Y(2175)

★★ The Belle Y(2175) width tends to be larger than previous measurements.★★ The widths of the φ(1680) and Y(2175) are similar; is Y(2175) a φ excited state?

More experimental information needed: BES working onJ/ψ→ηK*K*, ηΛΛ, ηKK, …

11/26/2010 ICHEP 2008 28

• 2γ collisions provide valuable information on light and heavy quark resonances.

• Coupling to spin 0, 2, 4… mesons by Yang’s Theorem.• Studied 2γ production of πoπo and π+π-.

Belle: 2γ physics

γγ → π+π-

newγγ → πoπo

95 fb-1

arXiv:0704.3538 (2007).

11/26/2010 ICHEP 2008 29

• Do partial wave analysis of differential cross section: S, D0, D2 (low mass region).

• Fit f0(980), f0(Y), f2(1270), f’2 (1525). r is ratio of helicity 0 to helicity 2 of f2(1270).

• Use known parameters forf2(1270), f’2 (1525).

• f0(Y) could be f0(1370) and/or f0(1500).

• Fit with f0(Y) strongly favored.

γγ → πoπo

11/26/2010 ICHEP 2008 30

BESII in J/Ψ→γππ finds a scalar with

m = 1466 ± 6 ± 20 MeV/c2

Γ = 108 +14-11 ± 25 MeV/c2

γγ → πoπo

PLB 642, 441 (2006).

arXiv 0805.3387 (2008)accepted by PRD

BESII

11/26/2010 ICHEP 2008 31

ISR Studies at EnergiesISR Studies at Energies• ISR physics gives access to:

Hadronic cross sections (e+e−→ hadrons)

Hadron spectroscopy for GeVTime-like form factor measurements

• Features/Strategies:– Tag (detect) ISR γ

• Forces the recoil hadronic system to be within fiducial detector region

• BaBar detects ~10% of ISR γ– Fully reconstruct the hadronic final states

51 << s

11/26/2010 ICHEP 2008

• Dalitz plots: dominated by K*(890)

• Cross sections:

32

e+e− → K+K−π0, KSK−π+

PRD 77, 092002 (2008)

Isoscalar Isovector

φ(1680) ρ(1450)

232 fb-1

Can use ISR tomeasure σ(e+e- → hadrons)at low energy.

11/26/2010 ICHEP 2008 33

BESII

accepted by PRL

11/26/2010 ICHEP 2008 34

BEPCII & BESIII

11/26/2010 ICHEP 2008 35

BEPCII: a high luminosity double–ring collider

SC RF

Beam magnets

Luminosity: 1 x 1033 cm-2s-1 @ 1.89 GeVCM Energy: 2 – 4.4 GeV Uses 93 bunches

and SC mini-beta.

11/26/2010 ICHEP 2008 36

BESIII Detector

Be beam pipe

SC magnetMuon Counter

Drift Chamber

CsI(Tl) calorimeter

TOF

11/26/2010 ICHEP 2008 37

BESIII DetectorBerylium beam pipeSmall-celled, helium-based MDC:

|cos θ| < 0.83 (all layers), < 0.93 (20 layers)σp/p = 0.5 % at 1 GeV/c; σdE/dx /dE/dx = 6% at 1 GeV/c

TOF (2 layers in barrel; 1 layer endcap)σT = 100 ps barrel; σT = 110 ps endcap

CsI electromagnetic calorimetercrystal length: 28 cm (15 X0)energy: 2.5%, space 0.6 cm at 1 GeV

Superconducting Magnet – 1 TMuon Counter

9 layers of RPCs in barrel; 8 in endcap

10 billion J/Ψ per year.

For details, see talk by F. Harris atMeson2008.

11/26/2010 ICHEP 2008 38

Status

First collisions with detector in July.Commissioning going well.

BESIII at IP~June 1

11/26/2010 ICHEP 2008 39

First Hadron Event July 19, 2008

11/26/2010 ICHEP 2008 40

• Many new precision charmonium results. Need help from theorists.

• ηc problem may be understood. Need energy dependence of matrix element.

• Y(2175) seen by many experiments. What is it?

• ISR and 2 photon physics at B-factories are producing many interesting results.

• BEPCII/BESIII commissioning started. Data this fall. Expect many new BESIII results at ICHEP2010.

Summary

11/26/2010 ICHEP 2008 41

11/26/2010 ICHEP 2008 42

Physics Topics at BES3Open charm factory :

• Absolute BR measurements of D and Ds decays• Rare D decay• D0 - D0bar mixing• CP violation, strong phase.• f D+, fDs form factors in semi-leptonic D decays• precise measurement (1.6% stat.) of CKM (Vcd, Vcs)• light meson spectroscopy in D0 and D+ Dalitz plot analyses.

11/26/2010 ICHEP 2008 43

Physics Topics at BESIII• Light hadron spectroscopy.• Charmonium: J/ψ, ψ(2S), ηC(1S), χC{0,1,2} , ηC(2S), hC(1P1), ψ(1D), etc. • New Charmonium states above open charm threshold.• Exotics : hybrids, glueballs, and other exotics in J/ψ and ψ(2S)

radiative decays.• Baryons and excited baryons in J/ψ and ψ(2S) hadronic decays.• Mesons and mixing of quark and gluon in J/ψ and ψ(2S) decays.• Electromagnetic form factors and QCD cross section (R values).• tau mass and tau physics near the threshold.• Search for new physics.

Very rich and interesting energy region.10 billion J/Ψ per year.

11/26/2010 ICHEP 2008 44

Fit with two non-interfering resonances• BG shape is fixed to sideband BG• the mass and width of the second peak are fixed to those of from BaBar.

5.8 σ

0 04

B(J/ψ ηY(2175)B(Y(2175) φf (980))B(f (980) π π )

(2.92 0.87( )) 10stat

+ −

−

→ → → =

± ×

2.5 σM =2.186±0.010GeV/c2

Γ= 0.065±0.022GeV/c2

N1 events= 47±14N2 events= 22±11

BESII J/ψ → ηφf0(980) Y(2175)

11/26/2010 ICHEP 2008

■ Fit to with three coherent BWs. C.L.=62%2.5 σ significance

M(x(2360))=(2360 ±46) MeV/c2,Γ(x(2360))= (124 ±105) MeV/c2.

45

Fit σ(e+e-→ φππ) with two coherent BWs. CL = 25%M(φ(1680))=(1687 ±7) MeV/c2, Γ(φ(1680))= (212 ±17) MeV/c2

M(Y(2175))=(2103 ±17) MeV/c2,Γ(Y(2175))=(212 ±22) MeV/c2

For the first time, φ(1680) parameters in φππ mode aremeasured!

Y(2175)

★★ φ(1680) : First observed by DM1 25 years ago. Recently by BaBar in e+e- → φ η and K*K ISR modes (PRD77,092002).

e+e- γISR φf0(980) → γISR KKππlum = 673 fb-1

preliminary

11/26/2010 ICHEP 2008 46

• COM important in decays of P-wave charmonium. Used to explain large pp rate.

H.-W. Huang and K.-T. Chao, Phys. Rev. D54, 6850 (1996).

J. Bolz et al., Phys. Lett. B392, 198 (1997).• BES found large χcJ → ΛΛ decay.• CLEOc uses 26 M Ψ(2S) events to study

to BB-bar.• Predictions:

BB-bar decays of χcJ

S. M. Wong, Eur. Phys.J. C14, 643 (2000)

arXiv: 0806.1715 [hep-ex];accepted by PRD(R).

11/26/2010 ICHEP 2008 47

BB-bar decays of χcJ BF in units of 10-5

χc0 χc1 χc2RB PDG06 1.96 ± 0.71 3.58 ± 1.52 4.09 ± 1.99RB CLEOc 1.32 ± 0.22 1.28 ± 0.27 2.21 ± 0.46

RB COM - 0.598 0.449

B(χcJ → ΛΛ)B(χcJ → pp)RB=

RB smaller for CLEOc but still agrees poorly with theory.

CLEOc has many more χc results – see Ryan Mitchell’s talk.