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
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