27 Settembre 2013
XCIX Congresso SIF 2013 – Trieste
G.M. Urciuoli, M. Battaglieri
L’esperimento JLAB12
 The Jefferson Laboratory and the Italian collaboration
 Physics (excerpt)
• Nucleon Structure (Form Factor and Quark Distribution)
• Parity Violation Experiments
• Hypernuclei
• Nuclear Structure
 Technological Developments
• HD Polarized Target
• Photon Tagger
• RICH/Clas12
• GEM/SiD Trackers
IFAE 2012 / Ferrara
E. Cisbani / Experimental Physics at JLab
1
Thomas Jefferson National Laboratory
• Newport News / Virginia / USA (3 ore da
Washington DC)
• DOE funding + Local Universities and
Organizations
• Director: H. E. Montgomery (ex-associate
director for research al Fermilab)
• 2000 International Users
more than
• Fundamental Research by electron
accelerator on 3+1 experimental Halls
• Applied research by FEL and other facilities
• Web site: www.jlab.org
2
CEBAF accelerator
• Linear Recirculating eAccelerator with
superconductive cavities
• Polarized beam
• High current (200 mA)
• Max. energy 6 GeV
• 100% duty factor
• Beam released
simultaneously on three
experimental Halls: A, B
and C
Arc
Arc
Injector
A
B
C
3
Current Experimental Halls
Hall A
Hall B/CLAS
Hall C
Two High Momentum
Resolution + one
large angular
acceptance
spectrometers
Dedicated neutron and
gamma detectors
Large acceptance
High multiplicity
reconstruction
Six coils Toroidal
field
Two asymmetric
spectrometers
High momentum
range and high
resolution
Dedicated detectors
High beam currents
(>100 mA), lumi 1037
cm-2 s-1
Tagged real
photons beam
High beam currents
(>100 mA), lumi 1037
cm-2 s-1
3He
NH3/ND3 Polarized
long. target
NH3/ND3 Polarized long.
target, high flexibility
unpol. from H to Pb
Large and flexible
installations
4p coverage
Moderately large and
flexible installations
T/L Polarized
target, high flexibility
unpol. from H to Pb
4
CEBAF after 2013
add Hall D
(and beam line)
6 GeV CEBAF (< 2013)
Max Current: 200 mA
Max Energy: 0.8 - 5.7 GeV
Long. Polarization: 75-85%
Upgrade magnets
and power
supplies
CHL-2
12 GeV CEBAF
(>2013)
Max Current: 90 mA
Max Energy Hall A,B,C: 10.9 GeV
Max Energy Hall D: 12 GeV
Long. Polarization: 75-85%
5
Experimental Halls after 2014
Hall A
Hall B/CLAS12
+ 1 large angular and
momentum, high lumi
spectrometer with
hadron ID
+ Solid detector
+ Möller detector
New beam line
New ~2p toroid
detector with
extended hadron ID
+ lumi 1038 cm-2 s-1
+ forward tagger for
quasi-real
photons
+ targets with large
thickness
+ long/trans
polarized H/D
target
hallaweb.jlab.org
www.jlab.org/Hall-B
Hall C
+ “super high”
momentum
spectrometer
+ dedicated equipment
Hall D/GLUEX
Excellent hermetic
coverage,
Solenoid field
High multiplicity
reconstruction
108 linearly
polarized <12 GeV
real photons/s
www.jlab.org/Hall-C
www.jlab.org/Hall-D
www.gluex.org
6
JLab physics
• Origin of quark and gluon confinement (B & D)
– Gluonic excitations - existence and properties of exotic mesons (and baryons)
– Heavy baryon and meson spectroscopy
• Structure of the Hadrons (A,B and C)
– Parton Distributions Functions (and Fragmentation Functions)
– New view of nucleon structure via the Generalized Parton Distributions (GPDs)
accessed in Exclusive Reactions
– Form Factors - improve knowledge of charge and current in the nucleons;
constraints on the GPDs
– Quark propagation and hadron formation
• Dynamics of the nucleons in the nuclei (A, B and C)
– The Quark Structure of Nuclei (resolving the EMC effect)
– The Short-Range Behavior of the N-N Interaction and its QCD Basis
– Cold nuclear matter
• Electroweak Interaction (A and C)
– High Precision Tests of the Standard Model at low energies via Parity-Violating
Electron Scattering Experiments
– Measure nuclear properties by weak interaction
7
Esperimento INFN formalmente attivo
dal 2009 per 7 anni, nasce dalla
sinergia delle ex sigle AIACE + LEDA
per sfruttare al meglio le opportunità
sperimentali offerte
dall’aggiornamento a 12 GeV
Intensa attività sperimentale al JLab/6 GeV (prevalentemente in sala A e B)
Forte coinvolgimento negli sviluppi legati al raddoppio di energia del fascio e
aggiornamento degli apparati nelle sale sperimentali
Sezioni INFN partecipanti (BA, CA, CT, GE, FE, ISS, LNF, PD, RM, RM2, TO):
Ricercatori + Tecnologi: ~ 60 (41.2 FTE)
8
TMD’s latest results at JLab
n - Collins small, largely compatible to 0; Sivers negative (?) for p+, zero for p-
First ‘direct’ measurement on neutron
Adapted from A. Puckett, JLab 2011
Collins Moment = h1  Collins FF
 Clean probe of relativistic effects
Sivers Asymmetry = f1T TMD  Unpol. FF
 Link to quark Orbital Angular Momentum
Experimental limits:
Modest statistics, integrated on the relevant kinematical variables (x,z,pT),
no access to large x, valence region, no clean interpretation of the data.
9
TMDs @ JLab 12 GeV
F
D
Hall B
Hall A
SBS/SOLID
CLAS12
HALL C
HMS+SHMS
E12-09-017: p/k
C12-11-102 p0
E12-06-112: p
E12-09-008: k
E12-07-107: p
E12-09-009: k
E12-11-107: p
E12-09-018: p/k
E12-10-006: p
C12-11-111: p/k
C12-11-108: p
H2, NH3, D2, ND3
HD
3He
NH3
H2, D2
Adapted from P. Rossi, JLab 2012
A Multi-Hall TMDs program
- Large variety of targets
- Different species of detected hadrons
-High luminosity experiments
- Extended phase space
1
0
Proton Form Factors
e + p → e’ + p’
d
 2
2
 GEp
 GMp
d

Rosenbluth Separation: assume
single photon approximation
Prior to JLab, expectations were that
Gep/GMp was fairly constant with Q2
e→ + p → e’ + p →’
m
GEp
GMp
 m
Pt ( Ebeam  Ee )

tan e
Pl
2M p
2
Polarization transfer from the incident
electron to the scattered proton
At JLab, new class of experiments show
GE/GMp decreasing linearly with Q2
New focus on nucleon structure and description of elastis scattering (two
photon exchange); possible role of quark OAM
1
1
Electromagnetic Nucleon Form Factors @12GeV
E-12-07-109: Polarization transfer
E-12-09-019: Cross section ratio
E-12-09-016: Double polarization
Extended measurements of p/n form
factors at high Q2
 Test different models (including
different contributions from the quark
OAM)
 Investigate the transition region
(perturbative / non perturbative)
 Constraint the H and E GPDs
1
2
Esperimenti di Violazione della Parità
• Misura accurata della asimmetria nei processi elastici (e DIS) di elettroni
polarizzati longitudinalmente su nucleone/nucleo non polarizzato
2


e
+
Z0
e
• Accesso alle costanti di accoppiamento deboli elettroni-quark (u/d) delle
correnti neutre, ovvero alla corrente debole del protone, ovvero all’angolo
di mixing debole
• Pone limiti su esistenza di nuova fisica (PVDIS, QWeak, Möller)
• Ha permesso la misura del contributo dei quark s ai fattori di forma del
nucleone (HAPPEX, G0)
• Permette la misura di importanti grandezze nucleari soppressi nei
processi elettromagnetici  PREX
1
3
Lead (208Pb) Radius Experiment: PREX
E = 850 MeV, =6° electrons on lead
A neutron skin established at ~93 % CL
Pins down the symmetry energy (1
parameter)
Neutron Radius = RN = 5.78 + 0.15 - 0.17 fm
Neutron Skin = RN - RP = 0.33 + 0.16 - 0.18 fm
PREX-II
Approved by PAC
First direct measurement
of the neutron skin
(Aug 2011)
1
4
15
Future equipment for PaVi experiments at Jlab/Hall A
SOLID (PV e- - q scattering + SIDIS)
- PV e-quark
- High precision TMD
Parity Violation Physics to test the SM at low energy: require high luminosity and
precise control of the systematics
Hypernuclei at JLab
Study -N Interaction potential
Experimental requirements:
- Excellent Energy Resolution
- Detection at very forward angles (6°→septum
magnets)
- Excellent PId for kaon selection →RICH
- High luminosity
Experiment E94-107
Hypernuclear spectroscopy
9Be (e,e’k+) 9 Li reaction
Λ
Published
Reactions Investigated:
9Be→9Li (3 spin doublets, information on Δ)
Λ
12C→12B (evidence of excited core states →
Λ
sN contribution)
16O→16N (unmatched peak may indicate
Λ
large sΛ term)
H →Λ,Σ0 (elementary process)
Analisi dell’esperimento sulla produzione di ipernuclei a Jlab completamente in mano alla
collaborazione italiana:
- M. Iodice, F. Cusanno et al., Phys. Rev. Lett. 99, 052501 (2007) (ipernucleo 12ΛB)
- F. Cusanno, G.M. Urciuoli et al., Phys Rev. Lett. 103 202501 (2009) (ipernucleo 16ΛN)
- G.M. Urciuoli, F. Cusanno, S. Marrone et al. Sottomesso a PHYS REV C
16
RM1, ISS
Thanks to energy resolution improvements a clear
three peak structure appears in the excitation energy
spectrum.
Experiment E06-007
208Pb(e,e’p)207Tl
and 209Bi(e,e’p)207Pb cross sections at true quasielastic
kinematics (xB=1, q=1 GeV/c, ω=0.433 GeV/c ) and at both sides of q
Never been done before for A>16 nucleus
★
★
★
RM1, ISS
Determine the spectroscopic factors dependence with Q2
Long range correlations: not needed!
Relativistic effect in nuclei: needed!
Search for dark force: HPS in Hall-B
18
HPS Projected results
-----------1 week 1.1 GeV
-----------1 week 2.2 GeV
Phase 1
expected
2014/15
Bump hunting
Bump hunting
+ vertexing
3 months 2.2 GeV
3 months 6.6 GeV
Phase 2
2015 or
later
1
9
JLab12
12 GeV era / Equipment
•
HD Target,
•
Forward Tagger,
•
RICH,
•
High Lumi Tracker
HD-ice: polarized frozen spin HD target
Polarized target of high dilution factor, made of solid Deuterium-Hydride:
Longitudinal and Transverse Polarizations: up to 75% H and 40% D
Relaxation time: > 1 year
Target cell
Polarization procedure » 3 months
Data taking: » months
Wide acceptance
INFN contribution:
• Dilution Refrigerator
• Contribution to the construction of the new InBeam Dilution Refrigerator Cryostat
• Raman analysis of ortho-hydrogen and paradeuterium contents in HD gas
• Magnetic Vari-Temp Cryostat for HD
condensation
and
NMR
polarization
measurements
Target
Transfer
 Run with polarized deuterons from HDice & circularly polarized photons
started on Dec. 2011: D polarization 27%
 Run with polarized deuterons from HDice & linearly polarized photons started
on April 2012: D polarization 30%
Test of HD-ice & electron beam
performed in February: on-going analysis
In-beam
cryostat
Comparison of signal
over background ratio:
HD versus conventional
polarized target
2
1
The Forward Tagger for CLAS12
Forward
Tagger
CLAS12
e-
*
New system to detect electrons at small angle and
perform quasi-real photo-production experiments
ep
Calorimeter
Calorimeter
electron energy/momentum
Photon energy (ν=E-E')
Polarization ε-1 ≈1 + ν2/2EE’
PbWO4 crystals with
APD/SiPM readout
Tracker
HTCC Moller cup
Scintillation Hodoscope
veto for photons
Scintillator tiles with WLS
readout,…
Tracker
electron angles
Polarization scattering plane
MicroMegas detectors
22
Scintillation
Hodoscope
Moller Shield
GEMC implementation
2
2
Adapted from M. Battaglieri, Genova 2012
RICH Conceptual Design
Proximity Focusing RICH + Mirrors
Aerogel
+ Planar
mirrors
Elliptical
mirrors
Photodetectors
Goal: reduce the photon detection area of
MA-PMTs H8500 to ~ 1m2/sector
Elliptical and planar mirrors to focus the
Cherenkov light of particles emitted at angles  > 12°
8 R8900
-Test with hadron beam at CERN with a
prelininary RICH prototype (summer 2011)
10
H8500
number of Np.e obtained for direct ring in consistent
with simulations
- Test with electron beam at LNF (july 2012)
- test of full prototype with p/K beam at CERN
(august 2012)
2
3
SBS Spectrometer in Hall A
High luminosity ~1039/s/cm2
Moderate acceptance
Forward angles
Reconfigurable detectors
High photons up to 250 MHz/cm2 and
electrons 160 kHz/cm2 background
Uva
JLab
INFN
Rutgers U.
College WM
U. of Glasgow
Norfolk State U.
Carnegie Mellon U.
U. of New Hampshire
SiD
40x150 cm2 GEM Tracker
70 mm spatial resolution
2
4
Spare
E
C
x
DC
R3
R2
R1
GeV/
c
1
p/K
TOF
p/p
TOF
K/p
RICH
HTCC
2
3
4
5
LTCC
LTCC
TOF
6
7
8
9
10
HTCC
HTCC
full pion / kaon / proton separation in
2–8 GeV/c range
p/K separation of 4-5  @ 8 GeV/c for a
rejection factor ~1000
Solenoid
PCAL
Torus
Aerogel mandatory to separate hadrons in the 2-8
GeV/c momentum range  collection of visible
Cherenkov light  use of MA-PMTs
INSTITUTIONS
ARGONNE NL
INFN
Bari, Ferrara, Genova,
Frascati, Roma/ISS
E. Cisbani / La Sperimentazione al JLab
TOF
SIF 2011 / L'Aquila
RICH detector for CLAS12
GLASGOW U.
JLAB
Option under investigation:
proximity focusing RICH + mirrors (innovative geometry)
U. CONN
UTFSM (Chile)
2
6
p/K
p/p
K/p
e/p
2
3
TOF
TOF
TOF
HTCC
4
5
6
LTCC
RICH
LTCC
LTCC
RICH
7
8
10
HTCC
HTCC
HTCC
LTCC
RICH
LTCC
EC/PCAL
4-5  p/K separation @ 8 GeV/c
Aerogel mandatory to separate hadrons in the 2-8
GeV/c momentum range  collection of visible
Cherenkov light  use of PMTs
9
E. Cisbani / Experimental Physics at JLab
GeV/c 1
IFAE 2012 / Ferrara
CLAS12 PID
Challenging project, crucial to minimize Detector area
Option under investigation: proximity focusing RICH + mirrors
Adapted from P. Rossi, JLab 2012
2
7
SIF 2011 / L'Aquila
E. Cisbani / La Sperimentazione al JLab
New RICH geometry
Adapted from L. Pappalardo Roma 2011
Aerogel
Flat Mirror + Aerogel
Active Photon Detector
2
8
RICH preliminary prototype
8
R8900
MA-PMTs
Aerogel
Electronics
Maroc2 front end electronics
developed for nuclear medicine
• preamplifier, adjustable from 1/8 to 4
• ADC, about 80fC per channel
10
H8500
SIF 2011 / L'Aquila
Hit distributions
aerogel n=1.05
2cm
3cm
aerogel n=1.03
Ebeam
(GeV)
Aerogel
<d>
(cm)
<R(p)>
cm
t (cm)
n
10
1
1.05
35.1
11.2
10
2
1.05
34.6
11.1
10
3
1.05
34.1
10.9
10
3
1.03
48.8
12.0
4
1
1.03
49.8
12.2
N.B. 1 and 2 cm means 2 or 3 blocks of 1 cm
3cm
integrated
distributions
of hits above
threshold
E. Cisbani / La Sperimentazione al JLab
1cm
3
0
Photo-production is the ideal tool:
• linearly polarized photon beam (NEW!)
• large acceptance detector (CLAS12)
Forward Tagger
E’
0.5-4.5 GeV
n
7-10.5 GeV
q
2.5-4.55 deg
Q2
0.007 – 0.3 GeV2
W
3.6-4.5 GeV
Photon Flux
5 x 107 /s @ Le=1035
E. Cisbani / La Sperimentazione al JLab
The study of the light-quark meson spectrum
and the search for exotic quark-gluon
configurations is crucial to reach a deep
understanding of QCD:
• identify relevant degrees of freedom
• understand the role of gluons and the origin of
confinement
Quasi-real photoproduction with CLAS12
(Low Q2 electron scattering)
Forward
Tagger
CLAS12
e-
γ*
eAdapted from R. De Vita, Roma/2011
p
Tracker
Electron angle
Hodoscope
Photon veto
Calorimeter
SIF 2011 / L'Aquila
Meson Spectroscopy in CLAS12
Electron Momentum/Energy
3
1
High Background Rate (up to):
(low energy  and e) 1 MHz/cm2
Drift
NO
MPGD
Silicon
MHz/mm2 MHz/mm2
High Resolution (down to):
Achievable
70 mm
50 mm
30 mm
Large Area:
from 40×150 to 80×300 cm2
Doable
Very
Expensive
… and modular: reuse in
different geometrical
configurations
YES
GEM
E. Cisbani / La Sperimentazione al JLab
System Requirements
Tracking Technology
SIF 2011 / L'Aquila
Choice of the technology
mMs
Flexibility in readout geometry
and lower spark rate
3
2
GEM foil: 50 mm Kapton + few
mm copper on both sides with
70 mm holes, 140 mm pitch
SIF 2011 / L'Aquila
GEM working principle
Ionization
E. Cisbani / La Sperimentazione al JLab
Multiplication
Multiplication
Multiplication
Readout
Strong electrostatic
field in the GEM holes
Recent technology: F. Sauli, Nucl. Instrum. Methods A386(1997)531
Readout independent from ionization and multiplication stages
3
3
GEp(5) SBS
Front Tracker
Geometry
SIF 2011 / L'Aquila
SBS Tracker GEM Chambers configuration
E. Cisbani / La Sperimentazione al JLab
x6
 Modules are composed to form larger
chambers with different sizes
 Electronics along the borders and
behind the frame (at 90°) – cyan
and blue in drawing
 Carbon fiber support frame around
the chamber (cyan in drawing);
dedicated to each chamber
configuration
X(4+4)
Back Trackers Geometry
3
4
SIF 2011 / L'Aquila
MonteCarlo + Digitazation + Tracking
High  + e background hits
 MHz/cm2
Bogdan Wojtsekhowski + Ole Hansen
+ Vahe Mamyan et al.
(Signal is red)
E. Cisbani / La Sperimentazione al JLab
6 GEM chambers with x/y readout
Use multisamples (signal shape)
for background filtering
3
5
SIF 2011 / L'Aquila
Assembling the first 40x50 cm2 module
Stretching
E. Cisbani / La Sperimentazione al JLab
Stretcher design
from LNF /
Bencivenni et al.
Use stretching and spacers
to keep foil flat
Foil Tension:
T = 2 kg/cm
Spacer Sector: S = 170 cm2
Expected maximum pressure
on foil
P  10 N/m2

Maximum foil deformation:
u  0.0074 * P * S / T = 6.4 mm
Gluing the next
frame with
spacers
3
6
E. Cisbani / La Sperimentazione al JLab
SIF 2011 / L'Aquila
Beam test @ DESY / Full Module Size 40x50 cm2
3
7
GEM  FEC  MPD  DAQ
SIF 2011 / L'Aquila
Electronics Readout (GEM and SiD)
Up to 10m
twisted,
shielded
copper cable
(HDMI)
75 mm
Passive backplane
(optional)
Main features:
• Use analog readout APV25 chips (analog and time information)
• 2 “active” components: Front-End card and VME64x custom module
• Copper cables between front-end and VME
• Optional backplane (user designed) acting as signal bus, electrical
shielding, GND distributor and mechanical support
E. Cisbani / La Sperimentazione al JLab
49.5 mm
2D Readout
8 mm
3
8
Chamber doublet
Dipole
Track
E. Cisbani / La Sperimentazione al JLab
SD
(x/y)
SIF 2011 / L'Aquila
+ Small Silicon Detector
Angular Range
3
9
21 Set 2009 / CSN III
JLab12 - E. Cisbani
39
6.5mm
5mm
10mm
8.5mm
8.5mm
A
5mm
B
Disegno custom per JLAB12
da un wafer di 6” (152mm)
D
A
B
C
103500
10mm
D
C
4
0
Fan Out PCB
E. Cisbani / La Sperimentazione al JLab
23 cm
41
SIF 2011 / L'Aquila
fori di fissaggio
30 cm
4
1
Si
Detector
X
X
Form
Factors
X
X
Parity
Violating
Electron
Scattering
X
TMDs,
nucleon
spin
structure
Meson
Study
HD
Target
RICH
X
X
Forward
Tagger
X
SIF 2011 / L'Aquila
GEM
Tracker
Equipment
Physics
E. Cisbani / La Sperimentazione al JLab
Equipment / Physics Matrix @ 12 GeV
Intensa attività di sviluppo tecnologico per un esteso programma di fisica
4
2
The “ultimate” description of the nucleon
4
3
3D view of the nucleon
Transverse Momentum Dependent (TMD) parton
distribution and fragmentation functions
• Describe correlations between the transverse
momentum of quarks/gluons and spin
• 3D picture of nucleon in momentum space
Information on: nucleon spin origin, quark orbital angular momentum,
relativistic effects in QCD, quark/gluon Q2 evolution,
QCD gauge invariances ...
Quark
• Describe correlations between the transverse
coordinates of quarks and spin
• 3D picture of nucleon in mixed momentum and
transverse space
Adapted from P. Rossi, JLab 2012
Nucleon
Generalized Parton Distribution functions (GPD)
4
4
Some TMDs projections
e3He →e’p+/-X
e p →e’K+/-X
longitudinally polarized target
E12-09-009
6 GeV data
SBS: e3He →e’K+/- X(transverse target)
E12-11-007
Adapted from P. Rossi. JLab 2012
E12-09-018
4
5
Luminosity
(s·cm2)-1
Tracking Area
(cm2)
GMn - GEn
up to 7·1037
GEp(5)
SIDIS
Resolution
Angular
(mrad)
Vertex
(mm)
Momentum
(%)
40x150
and 50x200
<1
<2
0.5%
up to
8·1038
40x120,
50x200 and
80x300
<0.7
~1.5
~1
0.5%
up to 2·1037
40x120,
40x150 and
50x200
Large
Area
~ 0.5
~1
<1%
High
Rates
SIF 2011 / L'Aquila
Experiments
E. Cisbani / La Sperimentazione al JLab
Different (e,e’h) experimental configurations
Down to ~ 70 mm
spatial resolution
Maximum reusability: same trackers in different setups
4
6
Confinement
Mechanism
(hadronization and
spectroscopy)
4
7
Hadronization of quarks
How hadrons form in
scattering processes ?
Transverse momentum distributions in
hadronization may be flavor dependent
Employ nuclei as analyzers of
hadronization processes, to probe:
- The hadronization formation length
(0-10 fm)
- The time scale on which a qq pair
becomes dressed with its own
gluonic field
Study the SIDIS reaction on nuclei;
observables:
H. Matevosyan et al., Phys. Rev. D85 (2012) 014021
- The hadronic multiplicity ratio
- The transverse momentum
broadening
Adapted from P. Rossi, JLab 2012
4
8
Beyond the quark model: hybrids and exotics
Quarks are confined inside colorless hadrons
they combine to 'neutralize' color force
q
q
q
q
q
mesons
baryons
Other quark-gluon configuration can give colorless objects
q q
q
q
molecules
q
q
q
q
q
q
pentaquarks
glueball mesons
q
hybrid mesons
QCD does not prohibit such states but not yet unambiguously observed
4
9
Adapted from M. Battaglieri, Genova 2012
QCD Lattice calculations
Lattice-QCD predictions
for the lowest exotics
states:
0+- 1.9 GeV
1-+ 1.6 GeV
Standard
mesons
Exotics
Hybrid mesons and
glueballs mass range
1.4 – 3.0 GeV
ρ
J.Dudek et al Phys.Rev.D82 (2010) 034508
This mass range is accessible in photoproduction experiments with a
beam energy in the range 5 GeV < E <12 GeV
Perfectly matched to JLab12 energy!
Adapted from M. Battaglieri, Genova 2012
5
0
Meson spectroscopy with photons at JLab
Search for mesons with 'exotic' quantum numbers
(not compatible with quark-model)
S=S1+S2 J= L+S
L+S
Not-allowed:
P = (-1) L+1
C= (-1)
JPC = 0-- , 0+- , 1-+ , 2+- ...
Unambiguous experimental signature for the presence of
gluonic degrees of freedom in the spectrum of mesonic states
Normal meson:
flux tube in
ground state
m=0
CP=(-1) S+1
Hybrid meson:
flux tube in
excited state
m=1
CP=(-1) S
Flux tube
JPC 1-+ , 1+-
Combine excited glue
quantum number with
those of the quarks
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Adapted from M. Battaglieri, Genova 2012
Meson spectroscopy with photons at JLab-12 GeV
• Determination of JPC of meson states requires PWA
• Decay and production of exclusive reactions
• Good acceptance, energy resolution, particle identification
Hall-D - GlueX Detector
• Good hermeticity
• Uniform acceptance
• Limited resolution
• Limited pID
• Good resolution
• Good pID
• Reasonable hermeticity
• Un-uniform acceptance
Adapted from M. Battaglieri, Genova 2012
Hall-B - CLAS12 Detector
Forward Tagger
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