http:// g/ jlab users group meeting curtis a. meyer poster

JLab Users Group Meeting Curtis A. Meyer

http://www.GlueX.org/

Poster



The GlueX Experiment

Curtis A. MeyerCarnegie Mellon University

Jefferson Lab HallD

q

q



Outline

Glue and Confinement

Normal and Hybrid Mesons

Photoproduction

Evidence for Exotic Mesons

Partial Wave Analysis

Summary



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



linear potential

Flux

tube

forms

between

qq

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



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!



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



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



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.



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



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

__

__



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



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



p 0na2 1320

a2 1320 1

data

theory

@ 5 GeV

8 GeV

From A. Szczepaniak

Photoproduction



a2 1320

From A. Szczepaniak

a2 1320 1

@ 18 GeV

Pion-Induced Production



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 ”



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



(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



p p

At 18 GeV/c

suggests p 0 p

p

to partial wave analysis

M( ) GeV / c2 M( ) GeV / c2

E852 Results



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



Detector designed to do

Double blind studies of 3 final states

p

n

X

Linear Polarization

m [GeV/c2]

GJ

a2

Partial Wave Analysis



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



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



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!



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



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)



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.

…



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.



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