Photoproduction and Gluonic Excitations

Meson 2002

Photoproduction and Gluonic ExcitationsQNP

Photoproduction and Gluonic ExcitationsCAP

Ref

eren

ces

Design Report can bedownloaded from the

Hall D website.

Nov 2000

Sept/Oct 2000

Feb 2001

Sept 2000

JLab whitepaper canalso be linked to from

the Hall D website.

Cover story articleon exotics and Hall D.

Articleon exotics and Hall D.

Both can also bedownloaded from

the Hall D website.

Flux Tubes andConfinement

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

mesons

Flux Tubes andConfinement

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

mesons

Lattice QCD

Flux tubes realized

Flux

tube

forms

between

qq

linear potential

0.4 0.8 1.2 1.6

1.0

2.0

0.0

r/fm

Vo(

r)

[GeV

]

From G. Bali

Hybrid Mesons

Confinement arises from flux tubes and their excitation leads to a new spectrum of mesons

1 GeV mass difference (/r)

Hybrid mesons

Normal mesons

Normal Mesons

Normal mesons occur when theflux tube is in its ground state

LS

S

1

2

S = S + S1 2

J = L + S

C = (-1)L + S

P = (-1)L + 1

Spin/angular momentum configurations& radial excitations generate our knownspectrum of light quark mesons

Nonets characterized by given JPC

Not allowed: exoticcombinations:

JPC = 0-- 0+- 1-+ 2+- …

Excited Flux Tubes

How do we look for gluonicdegrees of freedom in spectroscopy?

First excited state of flux tube has J=1 and when combined with S=1 for quarksgenerates:

JPC = 0-+ 0+- 1+- 1-+ 2-+ 2+-

exotic

Exotic mesons are not generated when S=0

Mas

s (G

eV)

1.0

1.5

2.0

2.5

qq Mesons

L = 0 1 2 3 4

Each 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

Meson Map

Pion Production

Exotic hybrids suppressed

Extensive search butlittle evidence

Quark spins anti-aligned

Photoproduction

Production of exotichybrids favored.

Almost no data available

Quark spins already aligned

E852 Results p p

At 18 GeV/c

to partial wave analysis

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

suggests

p 0 p

p

dominates

Results of Partial Wave Analysis

a1

a2

Benchmarkresonances

2

An Exotic Signal in E852

LeakageFrom

Non-exotic Wavedue to imperfectly

understood acceptance

ExoticSignal

1

Correlation ofPhase

&Intensity

M( ) GeV / c2

a2 1320 o

a2 1320

ao 980

System

p 0 n

p p

P-wave exotic reported at1400 MeV/c2

Confirmed by Crystal Barrel

Analysis in progress

P-wave not consistent withB-W parameterization

Compare p and p Data

p p

BNL

@ 18 GeV

Compare statistics and shapes

ca. 1998

28

4

Eve

nts

/50

MeV

/c2

SLAC

p n

@ 19 GeV

SLAC

1.0 2.52.01.5

ca. 1993

M(3) GeV / c2

What is Needed?

PWA requires that the entire event be identified - all particles detected, measured and identified.

The detector should be hermetic for neutral and charged particles, with excellent resolution and particle ID capability.

The beam energy should be sufficiently high to produce mesons in the desired mass range with excellent acceptance.

Too high an energy will introduce backgrounds, reduce cross-sections of interest and make it difficult to achieve above experimental goals.

PWA also requires high statistics and linearly polarized photons.

Linear polarization will be discussed. At 108 photons/sec and a 30-cm LH2 target a 1 µb cross section will yield 600M events/yr. We want sensitivity to sub-nanobarn production cross-sections.

Linear Polarization

Linear polarization is:

Essential to isolate the production mechanism (M) if X is known

A JPC filter if M is known (via a kinematic cut)

Related to the fact that states of linear polarization are eigenstates ofparity. States of circular polarization are not.

M

Optimal Photon Energy

Figure of merit based on:

1. Beam flux and polarization2. Production yields3. Separation of meson/baryon production

Optimum photon energyis about 9 GeV

flu

x

photon energy (GeV)

12 GeV electronsCoherent Bremsstrahlung

This technique provides requisite energy, flux and

polarization

collimated

Incoherent &coherent spectrum

tagged

with 0.1% resolution

40%polarization

in peak

electrons in

photons out

spectrometer

diamondcrystal

JLab Facility

Hall D will belocated here

CHL-2CHL-2

Upgrade magnets Upgrade magnets and power and power suppliessupplies

Upgrade Plan

Detector

Lead GlassDetector

Solenoid

Electron Beam from CEBAF

Coherent BremsstrahlungPhoton Beam

Tracking

Target

CerenkovCounter

Time ofFlight

BarrelCalorimeter

Note that tagger is80 m upstream of

detector

http://dustbunny.physics.indiana.edu/HallD

Detector

Solenoid & Lead Glass Array

At SLAC

At LANL

Now at JLab

-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

Acceptance

500

400

300

200

100

0

1.81.61.41.2

PWA fit

500

400

300

200

100

0

1.81.61.41.2

Mass (3 pions) (GeV)

events/20 MeV generated

Finding an Exotic Wave

Mass

Input: 1600 MeV

Width

Input: 170 MeV

Output: 1598 +/- 3 MeV

Output: 173 +/- 11 MeV

Double-blind M. C. exercise

An exotic wave (JPC = 1-+) was generated at level of 2.5 % with 7 other waves. Events were smeared, accepted, passed to PWA fitter.

Statistics shown here correspondto a few days of running.

X(exotic) 3

Review

David Cassel Cornell (chair)Frank Close RutherfordJohn Domingo JLabBill Dunwoodie SLACDon Geesaman ArgonneDavid Hitlin CaltechMartin Olsson WisconsinGlenn Young ORNL

The Committee

Executive Summary Highlights:

The experimental program proposed in the Hall D Project is well-suited for definitive searches of exotic states that are required according to our current understanding of QCD

JLab is uniquely suited to carry out this program of searching for exotic states

The basic approach advocated by the Hall D Collaboration is sound

CollaborationUS Experimental Groups

A. Dzierba (Spokesperson) - IUC. Meyer (Deputy Spokesperson) - CMUE. Smith (JLab Hall D Group Leader)

L. Dennis (FSU) R. Jones (U Conn)J. Kellie (Glasgow) A. Klein (ODU)G. Lolos (Regina) (chair) A. Szczepaniak (IU)

Collaboration Board

Carnegie Mellon University

Catholic University of America

Christopher Newport University

University of Connecticut

Florida International University

Florida State University

Indiana University

Jefferson Lab

Los Alamos National Lab

Norfolk State University

Old Dominion University

Ohio University

University of Pittsburgh

Renssalaer Polytechnic Institute

University of Glasgow

Institute for HEP - Protvino

Moscow State University

Budker Institute - Novosibirsk

University of Regina

CSSM & University of Adelaide

Carleton University

Carnegie Mellon University

Insitute of Nuclear Physics - Cracow

Hampton University

Indiana University

Los Alamos

North Carolina Central University

University of Pittsburgh

University of Tennessee/Oak Ridge

Other Experimental Groups

Theory Group

90 collaborators25 institutions

LRP

www.nscl.msu.edu/future/lrp2002.html

NSAC Long Range

Plan

LRP

www.nscl.msu.edu/future/lrp2002.html

LRP

ConclusionIn the last decade we have seen much theoretical progress – especially in LGT

Low energy data on gluonic excitations are needed to understand the nature of confinement in QCD.

Recent data in hand provide hints of these excitations - but a detailed map of the hybrid spectrum is essential.

Photoproduction promises to be rich in hybrids – starting with those possessing exotic quantum numbers – and little or no data exist.

The energy-upgraded JLab will provide photon beams of the needed flux, duty factor, polarization along with a state-of-the-art detector to collect high-quality data of unprecedented statistics and precision.

If exotic hybrids are there - we will find them.

E852 Experiment at BNL

p p

After PWA:

Conclusion: an exotic signal atA mass of 1400 MeV and widthOf about 300 MeV

Controversy

E852 Experiment at BNL

p p 18 GeV/c

If resonates in a P-wave - the resonance has exotic QN

0 Analysis - S & D Waves

Robert LindenbuschMaciej Swat

0 Analysis

No P-wave

P-wave exotic

Final state interactions

Fixing D-wave (a2) and then fitting intensity and

phase yields P-wave mass of 1.3 GeV and a width of 750 MeV

0 Analysis

(Exotic) Meson Spectroscopy : Role of Final State Interactions (IU experimentalists meet IU theorists)

• What is the nature of the P+ (JPC=1-+, wave in

Resonance such as (770) Rescattering such as (400-1200)

vs•Quark based interactions, •Meson exchange, interactions(Isgur, Speth)

• 3spectrum ( JPC=1-+,

vs

• Study of P-wave mesons ( f0(980), a0(980), a2(1300) ) : E852 : amplitude analysis + production characteristics (t-dependence)

•Dispersion relations•Feddeev equations(Ascoli, Wyld)

*

Linear Polarization - I

V = vectorphoton

for X, J = 0

Center of Mass of X

Y11 , sine i

Y1 1 , sin e i

m = 1

m = -1

R

L

Vector 2 PS

Suppose we produce a vector via exchangeof spin 0 particle and then V SS

For circular polarization

W , sin2

x R L

2 sincos

y iR L

2 sinsin

For linear polarization

Px: W , sin2 cos2

Py: W , sin2 sin2

Loss in degreeof polarization

requires correspondingincrease in stats

V

J=0

Linear Polarization - II

photon

for X, J = 0

Center of Mass of V

X = exchange particle

L 0, 1, or 2

PV P PX 1 L

Suppose we want to determineexchange: O+ from 0- or AN from AU

V = vectorphoton

m = 1

m = -1

R

L

AN AU

AN AU

Parity conservation implies:

With linear polarizationwhich is sum or diff ofR and L we can separateLinear Polarization Essential

X J=0– or 0+

V

a2 1320

Pion-Induced Production

From A. Szczepaniak

a2 1320 1

@ 18 GeV

Photoproduction

p 0na2 1320

a2 1320 1

data

theory

@ 5 GeV

8 GeV

From A. Szczepaniak

Add Arc

Add Cryomodules

Add Cryomodules

The Upgrade Plan

More on Monday fromKees deJager from JLab

http://dustbunny.physics.indiana.edu/HallD

Radphi @ JLab

p p

fo oo

a o o

5

Rare radiative decays of the meson

Complementary to factory measurements

200

150

100

50

0

2.01.81.61.41.21.00.80.6

M() GeV

Cut-away of Radphi Detectorlocated in Hall B

p Vp

Rare Radiative Decaysof the meson

Events

/10

MeV

Phi decaysPhi experiment

data from Summer, 2000

Craig Steffen

Radphi @ JLab p b1 1235 p

b1 1235 0

00 5

0 00

b1 1235 Craig Steffen

Hall D at JLab

$35M

$50M

$15M

$12M

$12MConstruction start - 2006Physics - 2009

Strongly RecommendedBuild it Soon !

NSAC - March 2001

Solenoid

Before After

February 2002