JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Poster
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
The GlueX Experiment
Curtis A. MeyerCarnegie Mellon University
Jefferson Lab HallD
q
q
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Outline
Glue and Confinement
Normal and Hybrid Mesons
Photoproduction
Evidence for Exotic Mesons
Partial Wave Analysis
Summary
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Flux Tubes
Color Field: Because of self interaction, confining flux tubes form between static color charges
Notion of flux tubes comes about from model-independentgeneral considerations. Idea originated with Nambu in the ‘70s
and Confinement
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
linear potential
Flux
tube
forms
between
From G. Bali
Lattice QCD Flux tubes realized
Confinement arises from flux tubes and
their excitation leads to a new
spectrum of mesons
š/r
ground state
transverse phonon modesHybrid mesons
Normal mesons
1 GeV mass difference
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
What role do gluons play in the mesonspectrum?
Lattice calculations predict a spectrumof glueballs. The lightest 3 have JPC
Quantum numbers of 0++ , 2++ and0-+.
The lightest is about 1.6 GeV/c2
Glueball Mass Spectrum
Morningstar et al.f0(980)
f0(1500)
f0(1370)
f0(1710)
a0(980)
a0(1450) K*0(1430)
QCDA Theory of Quarks and Gluons
mixing!
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
quark-antiquark pairs
ud
s u d
s
J=L+S
P=(-1) L+1
C=(-1) L+S
G=C (-1) I
(2S+1) L J
1S0 = 0 -+
3S1 = 1--,K*’,KL=0
1--
0-+
a2,f2,f’2,K2
a1,f1,f’1,K1
a0,f0,f’0,K0
b1,h1,h’1,K1
L=1
2++
1++
0++
1+-
3,3,3,K3
2,2,2,K2
1,1,1,K1
2,2,’2,K2
L=2
3--
2--
1--
2-+
radial
orbital
Non-quark-antiquark0-- 0+- 1-+ 2+- 3-+ …
Normal Mesons
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Hybrid Mesons
m=0 CP=(-1) S+1
m=1 CP=(-1) S
Flux-tube Model
ground-state flux-tube m=0
excited flux-tube m=1
built on quark-model mesons
CP={(-1)L+S}{(-1)L+1} ={(-1)S+1}
S=0,L=0,m=1
J=1 CP=+
JPC=1++,1--
(not exotic)
S=1,L=0,m=1
J=1 CP=-
JPC=0-+,0+-
1-+,1+-
2-+,2+-exotic
normal mesons
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
linear potential
QCD Potential
ground-state flux-tube m=0
excited flux-tube m=1
Gluonic Excitations provide anexperimental measurement of the excited QCD potential.
Observations of exotic quantum number nonets are thebest experimental signal of gluonic excitations.
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
1.0
1.5
2.0
2.5
qq Mesons
L = 0 1 2 3 4
SpectrumEach box correspondsto 4 nonets (2 for L=0)
Radial excitations
(L = qq angular momentum)
exoticnonets
0 – +
0 + –
1 + +
1 + –
1– +
1 – –
2 – +
2 + –2 + +
0 – +
2 – +
0 + +
Glueballs
Hybrids
Lattice 1-+ 1.9 GeV2+- 2.1 GeV0+- 2.3 GeV
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Why Photoproduction
A pion or kaon beam, when scattering occurs,
can have its flux tube excitedor
beam
Quark spins anti-aligned
Much data in hand with some evidence for gluonic excitations
(tiny part of cross section)
q
q
befo
req
qaft
er
q
q
aft
er
q
q
befo
re
beamAlmost no data in hand
in the mass regionwhere we expect to find exotic hybrids
when flux tube is excited
Quark spins aligned
__
__
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Very little photoproduction data exist. What little there is hint at a different resonance structure than what is seen in pion production.
In one year of initialrunning, expect 100times pion statistics
In one year of initialrunning, expect 100times pion statistics
Existing Data
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Exotics
N N
e
X
,,
1 IG(JPC)=1-(1-+)
’1 IG(JPC)=0+(1-+)
1 IG(JPC)=0+(1-+)
K1 IG(JPC)= ½ (1-)
1
1 b1 ,
’1
Couple to V.M + e
in Photoproduction1-+ nonet
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
p 0na2 1320
a2 1320 1
data
theory
@ 5 GeV
8 GeV
From A. Szczepaniak
Photoproduction
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
a2 1320
From A. Szczepaniak
a2 1320 1
@ 18 GeV
Pion-Induced Production
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
0+- and 2+- Exotics
N N
e
X
b0 IG(JPC)=1+(0+-)
h0 IG(JPC)=0-(0+-)
h’0 IG(JPC)=0-(0+-)
K0 I(JP)=½(0+)
b2 IG(JPC)=1+(2+-)
h2 IG(JPC)=0-(2+-)
h’2 IG(JPC)=0-(2+-)
K2 I(JP)= ½(2+)
a1,f0,f1
f0,f1,a1
f0,f1,a1
, a1,f0,f1
f0,f1,a1
f0,f1,a1
In photoproduction, couple to , or ?
“Similar to 1 ”
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
pp (18 GeV)
The a2(1320) is the dominantsignal. There is a small (few %)exotic wave.
Interference effects showa resonant structure in .(Assumption of flat backgroundphase as shown as 3.)
Mass = 1370 +-16+50
-30 MeV/c2
Width= 385 +- 40+65-105 MeV/c2
a2
E852 Results
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
(1400)
antiproton-neutron annihilation
Mass = 1400 +- 20 +- 20 MeV/c2
Width= 310+-50+50-30 MeV/c2
Same strength as the a2.
Produced from states with one unit
of angular momentum.Without 1 2/ndf = 3, with = 1.29
Crystal Barrel Results
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
p p
At 18 GeV/c
suggests p 0 p
p
to partial wave analysis
M( ) GeV / c2 M( ) GeV / c2
E852 Results
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
LeakageFrom
Non-exotic Wavedue to imperfectly
understood acceptance
ExoticSignal
1
Correlation ofPhase
&Intensity
M( ) GeV / c2
1(1600)
3 m=1593+-8+28-47 =168+-20+150
-12
’ m=1597+-10+45-10 =340+-40+-50
An Exotic Signal in E852
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Detector designed to do
Double blind studies of 3 final states
p
n
X
Linear Polarization
m [GeV/c2]
GJ
a2
Partial Wave Analysis
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
GlueX will be sensitive to a wide variety of decay modes - the measurements of which will be compared against theory predictions.
To certify PWA - consistency checks will be made among different final states for the same decay mode, for example:
b1 0 3
0 2
Should givesame results
Gluonic excitations transfer angular momentum in their decays tothe internal angular momentum of quark pairs not to the relative angularmomentum of daughter meson pairs - this needs testing.
X b1For example, for hybrids: favored
not-favoredX Measure many decay modes!
Hybrid Decays
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Acceptance-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Cos(GJ)
5 GeV
Mass(X) = 1.4 GeV
Mass(X) = 1.7 GeV
Mass(X) = 2.0 GeV
-3 -2 -1 0 1 2 30
0.2
0.4
0.6
0.8
1
GJ
-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Cos(GJ)
8 GeV
Mass(X) = 1.4 GeV
Mass(X) = 1.7 GeV
Mass(X) = 2.0 GeV
-3 -2 -1 0 1 2 30
0.2
0.4
0.6
0.8
1
GJ
-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Cos(GJ)
12 GeV
Mass(X) = 1.4 GeV
Mass(X) = 1.7 GeV
Mass(X) = 2.0 GeV
-3 -2 -1 0 1 2 30
0.2
0.4
0.6
0.8
1
GJ
p -> n
-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Cos(GJ)
5 GeV
Mass(X) = 1.4 GeV
Mass(X) = 1.7 GeV
Mass(X) = 2.0 GeV
-3 -2 -1 0 1 2 30
0.2
0.4
0.6
0.8
1
GJ
-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Cos(GJ)
8 GeV
Mass(X) = 1.4 GeV
Mass(X) = 1.7 GeV
Mass(X) = 2.0 GeV
-3 -2 -1 0 1 2 30
0.2
0.4
0.6
0.8
1
GJ
-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Cos(GJ)
12 GeV
Mass(X) = 1.4 GeV
Mass(X) = 1.7 GeV
Mass(X) = 2.0 GeV
-3 -2 -1 0 1 2 30
0.2
0.4
0.6
0.8
1
GJ
p -> p p Xn n
p Xn 00n
Acceptance in
Decay Angles
Gottfried-Jackson frame:
In the rest frame of Xthe decay angles aretheta, phi
assuming 9 GeVphoton beam
Mass [X] = 1.4 GeV
Mass [X] = 1.7 GeV
Mass [X] = 2.0 GeV
Acceptance is high and uniform
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Leakage
An imperfect understanding of thedetector can lead to “leakage” of strength from a strong partial waveinto a weak one.
STRONG: a1(1260) (JPC=1++)
Break the GlueX Detector (in MC).
Look for Signal strength in Exotic 1-+
Under extreme distortions, ~1% leakage!
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Three Day Workshop on partial wave analysis held atCarnegie Mellon University last week. 35 Participants fromEurope and North America, about 50% theorists and 50%Experimentalists. About equal numbers of “Baryon” and “Meson” people.
Proceedings will be published late this year.
PWA Workshop
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
CLAS PWA
p p +- (~5GeV Photons)
PRELIMINARY g6c Results
m+-) [GeV/c2]
Presented by Paul Eugenio
m+-) [GeV/c2]
PWA
0(770)
f2(1270)
JP=1- (m=+-1)
JP=1- (m=0)
(10% of exclusive events)
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
Other Physics
4 detector built to do PWA
Normal Meson Spectroscopy come for free.
Strangonium states (ss) are not well known.
Non-exotic Hybrids states (mixed).
Threshold KK physics (lower beam energy).
Baryons, particularly Hyperons (lower beam energy)
For 5GeV photons, can achieve ~70% polarization.
…
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
SummaryQCD predicts a spectrum of states directly associated with the gluonic degree of freedom and confinement. Exotic Quantum numbers are a definitive signature.Experiments have started to observe states with exotic quantum numbers, but the observations are few, and not in agreement with theoretical expectations.Photoproduction is expected (vector meson beams) are expected be a very good, yet unexplored way to produce these states.
GlueX will be able to map out a detailed picture of these states and their decays with statistics 100 times better than current pion experiments. Such information will yield important data on the dynamics of glue and its role in QCD.
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
CHL-2CHL-2
Upgrade magnets Upgrade magnets and power and power suppliessupplies
JLab Users Group Meeting Curtis A. Meyer
http://www.GlueX.org/
CHL-2CHL-2
Upgrade magnets Upgrade magnets and power and power suppliessupplies