The Hunt for Glueballs, Hybrids and other QCD exotics Ulrich Wiedner Uppsala University XIV Nordic Meeting on Intermediate and High Energy Nuclear Physics Gr‰ ftÂvallen, Jan 4-10, 2002
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The Hunt for Glueballs, Hybridsand other QCD exotics
Ulrich WiednerUppsala University
XIV Nordic Meeting on Intermediateand High Energy Nuclear PhysicsGr‰ftÂvallen, Jan 4-10, 2002
The theory of strong interaction, QCD, has twoimportant ingredients:
1) asymptotic freedom perturbative QCD
2) confinement formation of hadrons
Ulrich Wiedner
QCD at short distances αS << 1
Quantitative description of the experimental cross section over 10 orders of magnitude by perturbative QCD
transverse jet energy
Perturbative QCD is extremely successful:
Jet production in pp-collisions at = 1.8 TeV s
Ulrich Wiedner
αS (Q2) → 1 for Q2 → 1 GeV2
10-18 10-17 10-16 10-15distance [m]
QCD at large distances
Ulrich Wiedner
The Experimental and Theoretical Challenge
Understand non-perturbative phenomena like:
confinement
chiral symmetry breaking
Ulrich Wiedner
masses
L=0
L=0
QCD
Baryon (qqq)
Glueball (gg)
Meson (qq)
Hybrid (qqg)
Ulrich Wiedner
Gluons exist:
Ulrich Wiedner
L
p
p
p
p
Meson Production("Gluon-rich" processes)
Radiative J/Ψ decays
Central Production
WA 79, WA 102
Doublepomeron
exchange?
J/Ψ
pp Annihilation
Mark III,DM2,BES
ASTERIX,Crystal Barrel,OBELIX
c
c
L
L
Ulrich Wiedner
π˚π˚π˚ Dalitz plot
f0(975) f0(1370)f0(1500)
f2(1565)
f2(1270)
m(π°1π°3)2 / [MeV/c2]2
m(π
° 1π°
2)2
/ [M
eV/c
2 ]2
700,000 events = 6 × 700,000 entries
pp 6γ
0
0
1
1
2
2
3 GeV2
3
mποπο2
mπο
πο2
712,000 eventspp → ποποπο (at rest)
f2(1565)
mηπο2
mηπ
ο2
0.6
0.6
0.8
1.0
1.2
1.4
1.6
0.8 1.0 1.2 1.4 1.6 GeV2
pp → ποηη (at rest)
m2(π0 KLmiss)
m2( π
0K
Lseen
)
0.4
0.6
0.8
1
1.2
1.4
1.8
2
0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 GeV2
fo (1500)• K
LK
L
pp • πoKLK
L
37.500 events
1.2 1.3 1.4 1.5 1.6 1.7 GeV2
2.4
2.6
2.8
3.0
M2πη’
M2 ηη
’
f0(1500)
pp π°ηη'pp 5 π°
Phase
Spac
e
1000 1200 1400 1600
2000
4000
6000
CB Data
M4πο
Ulrich Wiedner
Decay properties
3
4
1
0
? ?
f0(1500)
K
ηη
π
π
ηη'
K
3
0.7 ± 0.3
0.8 ± 0.3
0.6 ± 0.3
L=0
π
π
ηη
K
K
Glueball
ηη'
Ulrich Wiedner
Ulrich Wiedner
Can this decay pattern be explained ?
Glueball-meson mixing
Interpretation difficult !
Help from theory ?
J. Sexton et al., Phys.Rev.Lett. 75, 4563 (1995):
C. Amsler, F. Close, Phys.Rev. D53, 295 (1996); F. Close, LEAP96:
G G
q
q
f0(1370) = -0.50 |G> + 0.13 |ss> + 0.86 |1/√2 (uu+dd)>
f0(1500) = 0.61 |G> - 0.61 |ss> + 0.43 |1/√2 (uu+dd)>
f0(1710) = 0.60 |G> - 0.76 |ss> + 0.22 |1/√2 (uu+dd)>
f0(1710) = 0.88 |G> + 0.33 |ss> + 0.34 |1/√2 (uu+dd)>
f0(1500) = -0.22 |G> + 0.91 |ss> – 0.36 |1/√2 (uu+dd)>
f0(1370) = -0.43 |G> + 0.25 |ss> + 0.87 |1/√2 (uu+dd)>
Ulrich Wiedner
Crystal Barrel sees a new isovector state:a0(1450): M = 1450 ± 40 MeV πη
Γ = 270 ± 40 MeV
The old possible nonet of scalar mesons:
A new possible nonet:
S
I3
a0(980)a0(980) a0(980)
K0(1430)K0(1430)
K0(1430)K0(1430)
0*
0*–*
+*
+–
f0(980) ?
S
I3
a0(1450)a0(1450) a0(1450)
K0(1430)K0(1430)
K0(1430)K0(1430)
0*
0*–*
+*
+–
? ?
Isoscalar 0++ resonances seen by Crystal Barrel
+ other experiments:
Too many resonances
f0(1450): M = 1446 ± 5 MeV 4πΓ = 56 ± 12 MeV
f0(1590): M = 1581 ± 10 MeV ηη' ηη 4πΓ = 180 ± 17 MeV
f0(1525): M = 1525 MeV ΚΚΓ = 90 MeV
fJ(1710): M = 1709 ± 5 MeV ΚΚ ππΓ = 140 ± 12 MeV
f0(975): M = 980 ± 20 MeV ππΓ = 100 ± 20 MeV
f0(1370): M = 1365 ± 50 MeV ππ ηη 4πΓ = 270 ± 80 MeV
f0(1500): M = 1511 ± 8 MeV ππ ηη ηη'Γ = 116 ± 17 MeV KK
Decay mode
Ulrich Wiedner
Ulrich Wiedner
Interpretation of the results:
f0(980), a0(980): KK-molecules
f0(1370): Nonet member
f0(1525), f0(1710): Nonet member
f0(1500) = f0(1590) = f0(1450): Exotic
Why is the f0(1500) an exotic?
Can we learn something from thedecay width ?
Quark models and other nonets:
287±14
MeV270±40
MeV
Γ (K*) < Γ (a0) < Γ ss) < Γ (nn)
Γ (f0(1500)) ηη, ηη ', KK ~ 15 MeV
Γ (f0(1500)) 4π, ππ ~ 100 MeV
Γ (f0(1500)) ππ ~ 20 - 30 MeV
no ss state
no nn state
The width of the f0(1500)Γ = 116±17 MeV
does not fit into the 0++ nonet
Ulrich Wiedner
Meson Productionin
γγ Collisions
... acts as an "Anti-Glueball Filter".
e+
e–
Coupling toelectric charges
Ulrich Wiedner
γγ Collisions from ALEPH
(Anti-Glueball Filter)
no f0(1500)
upper limit:Γ(γγ → f0(1500)) • BR(f0(1500) → π+π−) < 0.31 keV
Phys. Lett. B472 (2000) 189.
Ulrich Wiedner
Glueball – meson mixing occurs when both decayinto the same final states.
The light scalar (0++) glueball can decay solelyinto pseudoscalar mesons and ρρ, just like anyother light quark meson.
mixing unavoidable
Solution:
Understand the complete light-quark mesonspectrum experimentally and theoretically.
Ulrich Wiedner
N 2S+1LJ
1 1S0
1 3S1
1 1P1
1 3P0
1 3P1
1 3P2
1 1D2
1 3D1
1 3D2
1 3D3
1 3F4
2 1S0
2 3S1
2 3P2
3 1S0
JPC
0–+
1––
1+–
0++
1++
2++
2–+
1––
2––
3––
4++
0–+
1––
2++
0–+
I = 1
π
ρ
b1(1235)
a0(1450)∗
a1(1260)
a2(1320)
π2(1670)
ρ(1700)
ρ3(1690)
a4(2040)
π(1300)
ρ(1450)
π(1800)
I = 0
η, ηη'
ω, φφ
h1(1170), h1(1380)
f0(1370)∗ , f0(1710)∗
f1(1285), f1(1420)
f2(1270), f2'(1525)
η2(1645), η2(1870)
ω(1650)
ω3(1670), φφ3(1850)
f4(2050), f4(2220)
η(1295), ηη(1440)
ω(1420), φφ(1680)
f2(1810), f2(2010)
η(1760)
I = 1/2
K
K*(892)
K1B†
K0*(1430)
K1A†
K2*(1430)
K2(1770)
K*(1680)‡
K2(1820)
K3* (1780)
K4*(2045)
K(1460)
K*(1410)‡
K2* (1980)
K(1830)
ud, uu, dd uu, dd, ss su, sd
Review of Particle Physics 2000
contributions from LEAR experiments
Ulrich Wiedner
Higher mass glueballs (e.g. 2++) can have decaymodes that are OZI suppressed for (u and d) mesonslike φφ or φη.
The observation of such decay modes makes astrong case for a glueball appearance.
Glueballs with exotic quantum numbers do notmix with mesons and should be narrow (bumphunting).
Lattice based calculations:
NO light mesons may exist > 3.2 GeV(string breaking and color screaning)
M. Brisodova et al., Phys. Lett. B460, 1 (1999)M. Brisudova et al., Phys. Rev. D61, 054013 (200)
Higher-mass Glueballs
ANY glueball could be narrow if MG > 3.2 GeVand
ANY signal (besides cc states) could be a glueballor exotic
Ulrich Wiedner
C. Morningstar, M. Peardon; Phys. Rev. D 60 (1999) 034509
Charmonium
4000
2000
0++2++ 1+– 2-+ 3++ 1++ 1-- 3--
0-+ 0+- 1-+ 2+- 2-- 0-- 3-+3+-
JPC
UKQCD Collaboration, G. S. Bali et al., Phys. Lett. B309 (1993) 378.
6000
[MeV]
Ulrich Wiedner
Charmonium States and PredictedGlueballs
0.5 1.0 1.5 2.0 2.5 3.0
0.5
1.0
1.5
2.0
2.5
3.0
1
10
100
a2(1320)
a2(1320)
ρ–(770)
ρ(1400)
52,576 events
m2 (η
π−)
[G
eV/c
2 ]2
m2(ηπ−) [GeV/c2]2
pd π–π η + pspectator
(<100 MeV/c)
Ulrich Wiedner
Decay: (ηπ)L=1
Mass: 1400 ± 30 MeV
Width: 310 ± 70 MeV
Quantum Numbers: JPC = 1–+ (I =1)
not possible from qq
Properties of the ρ(1400)
Previous indications of this resonance:
P = (–)L+1
C = (–)L+S
J = L + S
π–p (π η)n (GAMS/CERN, 100 GeV/c, 1988)π–p (π η)n (VES/Serpukhov, 100 GeV/c, 1993)π–p (π η)n (E852/Brookhaven, 18 GeV/c, 1997)
M: 1300 – 1400 MeV, G: 150 – 400 MeV
Ulrich Wiedner
• Complicated analysis (x 10 more amplitudes for high L-waves, exchange)• Dominant a2(1320); feedthrough to P+ wave, background (few percent) • Phase motion relative to a2(1320) indication of resonance
D+
P+
1.0
5000
10000
15000
1.2 1.4 1.6 GeV
1.0 1.2 1.4 1.6 1.8
Eve
nts
/ 0
.04
Ge
V
a2(1320)
ρ(1320)
Ph
ase
Diff
ere
nce
[ra
d]
∆φ (D
+ -
P+)
0.5
0.
1.0
1.5
exotic wave
mηπ
Phase [rad]
vs. production in 18 GeV/c π− beam (BNL-E852)
Hybrid production in pp annihilation
Ulrich Wiedner
1 32 GeV2
a2(1320)
ρ(1400)
A second exotic particle (JPC=1–+)
Crystal Barrel:
pp π+π–η'
π1(1600): M = 1563 ± 30 MeV/c2Γ = 195 ± 50 MeV/c2
preliminary, LEAP2000 conference
BNL (E852):
π–p ρπ–p
π1(1600): M = 1593 ± 8 MeV/c2Γ = 168 ± 20 MeV/c2
Phys. Rev. Lett. 81 (1998) 5760
Ulrich Wiedner
preliminary, Joerg Reinhardt, Bonn
()S a2(1320) a0(1450) 1 lnL
(1585,160)
22.72 77.28 - - - 164.2
18.68 80.78 0.53 - - 158.31
33.75 40.35 0.01 25.9 - 134.1
24.26 64.0 1.23 2.39 8.04 126.63
22.72 77.28 - - - 164.2
18.68 80.78 0.53 - - 158.31
27.15 64.7 1.33 - 6.82 127.83
24.26 64.0 1.23 2.39 8.04 126.63
(1567.7,158.2)
26.93 64.5 1.28 - 7.08 127.28
(1563,195.0)
23.64 61.3 1.24 3.76 10.1 125.86
Fit of Dalitz plot
Ulrich Wiedner
Two-BodyThresholds
ΣcΣc
ΛcΛc
ΩsΩs
ΞsΞs
DD
ΣsΣs
ΛsΛs
ΞcΞc
LEAR
p M
omen
tum
[GeV
/c]
ΩcΩc
Mesons and Exotics
6
3
4
2
1
5
Light Mesonsπ,η,ω,φ,ρ,f,a,h,K
Charmed MesonsD, Ds
CharmoniumJ/Ψ, χ, Ψ(2S)
Bottom MesonsB, Bs
ssgddguug
ccgccqq
qqqq
Predicted "Exotics"qq Mesons
Mas
s [G
eV/c2
]
ggggg
at rest
2
4
6
8
10
12
1415
Ulrich Wiedner
DissociationEnergy
23S1
11S0
21P1
21S0
13S1
23P1
23S1 23P2
23P0
n = 1
n = 2
Rel
ativ
e E
nerg
y (e
V)
Positronium
7
6
5
4
3
2
1
0
L = 0Singlet Triplet
L = 1Singlet Triplet
Charmonium
23S1 ψ'
23P1 χ1
23P2 χ221P1 hc
21S0 η'c
11S0 ηc
13S1 ψ
Rel
ativ
e E
nerg
y (M
eV)
Qua
si-b
ound
sta
tes
Bou
nd s
tate
s
DD threshold
23P0 χ0
L = 0Singlet Triplet
L = 1Singlet Triplet
1000
900
800
700
600
500
400
300
200
100
0
–100
Ulrich Wiedner
Ulrich Wiedner
ηc'
ηc
χ2
χ1 χ0
χ0,1,2 γJ/ψ
Charmonium Spectrum
Ulrich Wiedner
Singlet Triplet Singlet Triplet Singlet Triplet
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
Mas
s [G
eV]
L = 0 L = 1 L = 2
ηc
χ1
J/ψ
ηc'
ψ'
χ0
χ2hc
1D23D2
DD threshold
0–+
0–+
1--
1--
1+– 2++
1++
0++
2–+ 2--
(13.2)
(0.09)
(13.5)
(0.88)(<1.1)
(<8)
(0.27)
(2.0)
Charmonium spectrum ...
... "clean" and understood.
Identification of additional states easier than inthe light meson sector.
e+
e–
e+
e–
JPC = 1–– J = 0, 2C = +
p
p
p
p
J = 0, 2, ... J = 1C = + C = –
Meson production: e+e– vs. pp
2-γ experiments difficult, since it is mostly1-γ annihilation restricted q.n. (1––).
All quantum numbers possible all mesons can be produced directly.
Ulrich Wiedner
Production:Crystal Ball
γ e+e–
γ J/ψ
pp χ1,2
Formation:
σm (beam) = 0.5 MeV
E 760 (Fermilab)
γ γ e+e–
γ γ J/ψ
e+e– ψ'
γ χ1,2
Ulrich Wiedner
Decay of charmed hybrids
c
cg
µ+
µ−
cc
Decay of charm into leptons provides a clean "tag".
Charmonium
Charmed Hybrid
η
Ulrich Wiedner
Glueball Production in ccg Decays
Charmed Hybrid
Charmed Hybrid
Charmonium
Glueball
Glueball
Glueball
Ulrich Wiedner
Cascade decay
C = +
Same C parity µ+
µ−
Decay by annihilation
C = –(suppressed by αs)
Indications for a J/ψφ resonances?
BABAR can expect ~300 events within 5 years.
M2 (J
/)(
GeV
2 /c4 )
M2( K)(GeV2/c4)
2031099-00424.0
2.016.0
17.0
18.0
19.0
20.0
21.0
22.0
23.0
5.04.54.03.53.02.5
4.35 GeV/c24.5 GeV/c2
New Results from CLEO
Phys. Rev. Lett. 84, 1393 (2000)
B J/ψφK
4.7 GeV/c2
Ulrich Wiedner
The new GSI Accelerator Complex
Par
alle
l Ope
rati
on o
f B
eam
s
e – cooling
HE
SR
Mom
entum Spread:
δp/p ≥ 7×10
–6
Max. L
uminosity:
2×10
32 cm–2 s
–1
Max. M
agnetic Rigidity:
50 Tm
( ⇔ 15 G
eV/c p )
Circulating p: ≤ 2×
1012
Beam
radius at target:0.03 m
m
Ulrich W
iedner
Universal Detector
Detector features:tracking of charged particles measurement and identification of γ, e±, µ±, π±, K±, p, p high rate capability sophisticated and fast trigger scheme
Ulrich Wiedner
JPCFermion-Antifermion
Ulrich Wiedner
How to make resonances?
Produktion experiments:
Formation experiments:
all quantum numbers possible
identical quantum numbers
P = (–)L+1
C = (–)L+S
J = L + S
Signal in production but no signal in formation
Production vs. Formation
Formation experiments cannot produce exotic JPC.
Production experiments can produce exotic JPC.
A detector should be suited for both:
production and formation
very interesting
Ulrich Wiedner
The HESR is not only a unique facility, it is theonly one that allows to study:
Hybrids in e+e–:
Glueballs, Hybrids, Hadrons
Lattice:WEAK direct production even of 1–– states,since wavefunction at the origin is small.
B-decays lack statistics.
Central production in pp collisions:
Difficult to see even normal charmonium states.
C. Michael, Nucl. Physt. A655, 12c (1999)
Ulrich Wiedner
* For selected decay mode
** L = 2×1032 cm–2s–1, 50 % detection and accelerator efficency Integrated luminosity = 4 pb–1/ day
*** 1% B.R. for this decay mode
Charmonium Production in pp
cc JPC M [MeV]Γtot
[MeV]Decay mode
σ(M)* [pb]
Events/day**
ηc 0–+ 2980 13.2 γγ 550 4400
ηc 0–+ 2980 13.2 φφ 3100 24800
ηc' ??? 0–+ 3594 γγ 120 960
J/ψ 1–– 3097 0.087 e+e–/µ+µ– 630000 5040000
ψ' 1–– 3686 0.277 e+e–/µ+µ– 4480 35840
ψ' 1–– 3686 0.277 J/ψ X 17600 140800
χc0 0++ 3415 14 γγ 30 240
χc0 0++ 3415 14 γ J/ψ 52 416
χc1 1++ 3511 0.88 γ J/ψ 3600 28800
χc2 2++ 3556 2.0 γ J/ψ 3700 29600
χc2 2++ 3556 2.0 γγ 220 1760
ccg 1–– (4100) (0.2) (J/ψη***) (120) (960)
ccg 1–+ (4000) ??? (J/ψ ω,φ,γ) (9) (75)
Ulrich Wiedner
D mesons interactwith rest nucleus
pA ψ + (A–1)
D
p3.5 – 4.5 GeV
ψ (cc) decays into DD
D
p – Nucleus Interaction
Ulrich Wiedner
ψ(3770)
ψ(3770)
ψ(4160)
D–= dc
D+= dc
D0= uc
D0= uc–Ds = sc
+Ds = sc
quark – nucleusinteraction
=d (or d) – nucleus
interaction*
quark – nucleusinteraction
=u (or u) – nucleus
interaction*
quark – nucleusinteraction
=s (or s) – nucleus
interaction*
* ignoring c (or c) – nucleus interaction
Ulrich Wiedner
• rate at different nuclear targets
• angular distributions
• comparison to hydrogen
Experimental techniques:
• wire targets (like in HERAb)
• pellet targets (like in WASA-CELSIUS)
• D – triggers
Ds can be distinguished from D by theirdistinct decay into φ + anything (18 %).
± ±
Measurements:
Ulrich Wiedner
Topics not mentioned
Baryon Pair Production:
charmed: study threshold production for understanding ofc production mechanism
strange: ΩΩ produced via triple kaon exchange?comparison of production rates: ΩΩ vs. φφφ
CP Violation
Charm Physics in Nuclei:
J/Ψ - N cross section: color transparency?
exotic states of nuclear matter?
charmonium nucleus bound states?
mass shift of charmonium states in nuclear matter:( charmonium states are narrow below DD threshold!)
Ulrich Wiedner
Summary
The first QCD exotics have been found in highstatistics and high precision 4π experiments.
Other glueballs and hybrids must exist.
Studying the charmonium energy rangesimplifies life (small, well known states).
Many issues in normal charmonium spectroscopyare still unsettled.
Charmed hybrids (< 4.3 GeV) show up asadditional small states.
A dedicated accelerator with excellent beamproperties designed together with a highstatistics, high precision experiment is aworld class facility for hadron physics.
Their production rate is comparable to those ofnormal mesons in pp annihilations.
Ulrich Wiedner
E760/E835 has prooven how well suited pp isfor precision spectroscopy.
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