THE EXPERIMENT
Curtis A. Meyer Carnegie Mellon
The GlueX Collaboration Arizona State, Athens, Carnegie Mellon, Catholic University, Univ. of Connecticut, Florida International, Florida State, George Washington, Glasgow, GSI, Indiana University, ITEP, Jefferson Lab, U. Mass Amherst, MIT, MePhi, Norfolk State, North Carolina A&T, Univ. North Carolina Wilmington, Northwestern, Santa Maria, University of Regina, Tomsk and Yerevan Physics Institute. Over 120 collaborators from 24 institutions with others joining and more are welcome.
June 4, 2016 Meson 2016 - C.A. Meyer 2
Outline • The GlueX physics program. • The GlueX experiment and its performance during commissioning.
• Expected initial physics from GlueX. • Future plans and other physics. • Summary.
June 4, 2016 Meson 2016 - C.A. Meyer 3
12-GeV beam, Dec.2015
Quantum Chromo Dynamics June 4, 2016 Meson 2016 - C.A. Meyer 4
QCD describes the interactions of quarks and gluons and should predict the spectrum of bound-state baryons ( ) and mesons ( ). There should also be mesons in which the gluonic field contributes directly to the JPC quantum numbers of the states --- hybrid mesons. Some are expected to have ``exotic’’ quantum numbers.
qqqqq
Lattice QCD calculation of the light-quark meson spectrum. ``Constituent gluon’’: JPC = 1+-
mass of 1-1.5 GeV. The lightest hybrid nonets 1--, (0-+,1-+, 2-+)
0.5
1.0
1.5
2.0
2.5
exotics
isoscalar
isovector
YM glueball
negative parity positive parity
? ud
ss
uu
2.0GeV
0+- 2+- 1-+
2.5Gev
Lattice QCD June 4, 2016 Meson 2016 - C.A. Meyer 5
0.5
1.0
1.5
2.0
2.5
exotics
isoscalar
isovector
YM glueball
negative parity positive parity
Light-quark Mesons (u,d,s)
1p2
�uu� dd
� 1p2
�uu+ dd
�(ss)
PRD83, 111502 & PRD88, 094505
Lattice QCD June 4, 2016 Meson 2016 - C.A. Meyer 6
0.5
1.0
1.5
2.0
2.5
exotics
isoscalar
isovector
YM glueball
negative parity positive parity
Light-quark Mesons (u,d,s)
1p2
�uu� dd
� 1p2
�uu+ dd
�(ss)
States with non-trivial gluonic fields. Fj,µ⌫ F
µ⌫j
1--
0-+
2-+ 1-+
1--, 0-+ , 1-+ , 2-+
Supermultiplet
PRD83, 111502 & PRD88, 094505
June 4, 2016 Meson 2016 - C.A. Meyer 7
QCD Exotics
π1 IG(JPC)=1-(1-+)
η’1 IG(JPC)=0+(1-+)
η1 IG(JPC)=0+(1-+)
K1 IG(JPC)= ½ (1-)
La#ceQCDsuggests5nonetsofmesonswithexo7cquantumnumber: 1nonetof0+-exo7cmesons2nonetsof1-+exo7cmesons2nonetsof2+-exo7cmesons
⇡1
⌘1
Experimentalevidenceexistsforπ1states.
``Constituent gluon’’ behaves like JPC = 1+- with a mass of 1-1.5 GeV The lightest hybrid nonets: 1--, (0-+,1-+, 2-+)
0.5
1.0
1.5
2.0
2.5
exotics
isoscalar
isovector
YM glueball
negative parity positive parity
? ud
ss
uu
2.0GeV
0+- 2+- 1-+
2.5Gev
Kaon states do not have exotic QNs
PRD84, 074023
Photoproduction Mechanisms June 4, 2016 Meson 2016 - C.A. Meyer 8
ρ,ω,φγ
p N
X
π,η,ρ,ω,P,...
Simple quantum number counting for production: (IG)JPC up to L=2
ρπ,ρω π1ωω,ρρ η1
ωω,ρρ,φω η’1 ρP b0 ωP h0 ωP, φP h’0 ωπ,ρη,ρP b2 ρπ,ωη,ωP h2 ρπ,ωη,φP h’2
ρπ is charge-exchange only
Can couple to all the lightest exotic hybrid nonets through photo- production and VMD. Linear polarization is a filter on the naturality of the exchanged particle.
P = Pomeron exchange
June 4, 2016 Meson 2016 - C.A. Meyer 9
Hybrid kaons do not have exotic QN’s
Decay Modes of Exotic Hybrids π1 → πρ, πb1 , πf1,πη’, ηa1 η1 → ηf2,a2π,ηf1, ηη’,π(1300)π, a1π, η1’→ K*Κ, Κ1(1270)Κ, Κ1(1410)Κ , ηη’
b2 → ωπ, a2π, ρη, f1ρ, a1π, h1π, b1η h2 → ρπ,b1π,ωη, f1ω h’2 → Κ1(1270)Κ, Κ1(1410)Κ, K2
*Κ, φη, f1φ
b0 → π(1300)π , h1π, f1ρ, b1ηh0 → b1π , h1η h’0 → K1(1270)Κ, Κ(1460)Κ, h1η
Early Reach With Statistics Hard Models suggest narrower states are in the spin-1 and spin-2 nonets, while the spin-0 nonets are broad.
The GlueX Experiment June 4, 2016 Meson 2016 - C.A. Meyer 10
barrelcalorimeter
time-of-flight
forward calorimeter
photon beam
electronbeamelectron
beam
superconductingmagnet
target
tagger magnet
tagger to detector distanceis not to scale
diamondwafer
GlueX
central driftchamber
forward driftchambers
Photo Production of Hybrids, Light-quark Mesons and Strangeonium States
Initial Physics in 2016
BaBar DIRC Bars
The GlueX Experiment June 4, 2016 Meson 2016 - C.A. Meyer 11
75 m
Collimator select � < 25 �r
polarized photons Hall-D
Diamond Radiator "↑− "%→&"↑− %
Tagger Area
Photon Tagger Pair Spectrometer
GlueX Spectrometer
Photon Beam Dump
Electron Beam Dump East ARC
North LINAC
• 12 GeV e- beam up to 2.2 µA. • Linearly polarized photons (Pɣ≈40%) from
coherent bremsstrahlung on thin diamond radiator.
• Polarization parallel and perpendicular to floor.
• Design intensity of 108 ɣ/s in coherent peak (Eɣ = 8.4-9 GeV)
Polarimeter
Goniometer with diamonds
The GlueX Experiment June 4, 2016 Meson 2016 - C.A. Meyer 12
75 m
Collimator select � < 25 �r
polarized photons Hall-D
Diamond Radiator "↑− "%→&"↑− %
Tagger Area
Photon Tagger Pair Spectrometer
GlueX Spectrometer
Photon Beam Dump
Electron Beam Dump East ARC
North LINAC
Polarimeter
GlueX Commissioning June 4, 2016 Meson 2016 - C.A. Meyer 13
Generated: April 25, 2016
Integrated Beam Time [Days]1050 15
Num
ber o
f Eve
nts C
olle
cted
/ 10
9
0
10
20
30
TotalUnpolarized|| Polarization⊥ Polarization
Spring 2016 run with 12-GeV electrons on thin diamond radiators. Linear polarization, both perpendicular and parallel to the earth, collected.
GlueX Calorimeter Performance
June 4, 2016 Meson 2016 - C.A. Meyer 14
Mγγ [GeV/c2]0.00 0.05 0.10 0.15 0.20 0.25 0.30
Cand
idat
es /
2 M
eV/c
2
0
50
100
150
200
250
0
50
100
150
200
250
300
0.00 0.05 0.10 0.15 0.20 0.25 0.30
Cand
idat
es /
2 M
eV/c
2
Mγγ [GeV/c2]
Design Goal Design Goal
Forward Lead Glass Calorimeter Barrel Lead-Scintillating Fiber Calorimeter
GlueX Tracking Performance June 4, 2016 Meson 2016 - C.A. Meyer 15
Track to Wire Distance (d) [mm]0 1 2 3 4 5 6 7 8
Stra
w E
ffici
ency
0.0
0.2
0.4
0.6
0.8
1.0
d
8 mm
Central Drift Chamber (CDC)
0 1 2 3 4
140
160
180
200
220
240
260
Wire
Pos
ition
Res
olut
ion
[µm
]
Track to Wire Distance [mm]
Forward Drift Chamber (FDC)
Design Resolution for Cathodes and Wires: 200 µm
Achieved CathodeResolution: 150 µm
Posit
ion
Reso
lutio
n [µ
m]
200
400
600
800
0
Design Resolution: 150 µm
1000
Track to Wire Distance (d) [mm]0 1 2 3 4 5 6 7 8 9 10
x Coordinate [mm]-400 -200 0 200
0.82
0.86
0.90
0.94
0.983D
Rec
onst
ruct
ion
Effici
ency
400
Colors Index Chambers in the Third Package
GlueX Particle Identification June 4, 2016 Meson 2016 - C.A. Meyer 16
Track Momentum [GeV/c]0.0 0.5 1.0 1.5 2.0 2.5 3.0
β fro
m T
ime
of F
light
0.0
0.2
0.4
0.6
0.8
1.0
1
10
102
Positively Charged Particles
0.0 0.5 1.0 1.5 2.0 2.5 3.00.0
0.2
0.4
0.6
0.8
1.0
1
10
102
Track Momentum [GeV/c]
β fro
m T
ime
of F
light
Negatively Charged Particles
0 2 4 6 8 10 120.0
0.5
1.0
1.5
2.0
2.5
050100150200250300350400450
FCAL
Ene
rgy
/ Tra
ck M
omen
tum
Track Polar Angle [degrees]0.0 0.5 1.0 1.5 2.0 2.5 3.0
CDC
dE/dx
[keV
/cm
]
0
2
4
6
8
10
12
14
1
10
102
103
104
Positively Charged Particles
Track Momentum [GeV/c]
e+/e-
hadrons
p
π/K/e
pKπ
eKπ
e
Incorrect RF Bunch
Start of Physics in GlueX • Initial reactions will be polarization transfer and beam asymmetry measurements.
• Spin-density matrix elements to understand production mechanisms.
• Opportunistic results from data exploration. • Cross section measurements. • Identify known mesons in PWA. • Move on to the search for exotic hybrids.
June 4, 2016 Meson 2016 - C.A. Meyer 17
�p ! (⇡0, ⌘, ⌘0)p �p ! (⇢0,!,�)p
Early Physics in GlueX • Initial reactions will be polarization transfer and beam asymmetry measurements.
• Spin-density matrix elements to understand production mechanisms.
• Opportunistic results from data exploration. • Cross section measurements. • Identify known mesons in PWA. • Move on to the search for exotic hybrids.
June 4, 2016 Meson 2016 - C.A. Meyer 18
�p ! (⇡0, ⌘, ⌘0)p �p ! (⇢0,!,�)p
Deg
ree
of P
olar
izat
ion
0.0
0.2
0.4
0.6
0.8
1.0
Energy [MeV]0 2000 4000 6000 8000 10000 12000
Model Fit to Coherent Enhancement
Beam Asymmetry in ρ PhotoproductionJune 4, 2016 Meson 2016 - C.A. Meyer 19
-150 -100 -50 0 50 100 150φ [degrees]
dN/d
φ [A
rbitr
ary
Uni
ts]
-150 -100 -50 0 50 100 150
⊥ Polarization || Polarization
φ [degrees]Lab
Floor
ρ Deca
y Plane
ρ
π+
π−
Photon Beam
Polarizat
ion Planeφ
|| Polarization
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
-150 -100 -50 0 50 100 150φ [degrees]
Asym
met
ry
d�? / 1� P?⌃ cos 2� d�k / 1 + Pk⌃ cos 2�P⌃ cos 2� =
Nk �N?
Nk +N?
~40% Polarization
Large polarization transfer to the ρ
Between 100 and 1000 times the 3000 existing events from SLAC. Working with JPAC on models for analysis
Acceptance errors not included
20
π0 beam asymmetry Beam asymmetry Σ provides insight into dominant production mechanism
Understanding production mechanism critical to disentangling JPC of observed states in exotic hybrid search.
From experimental standpoint easily extended to ɣp→η where there are no previous measurements!
Exchange JPC
Mathieu et al. PRD 92, 074013
Data at different beam energies
June 4, 2016 Meson 2016 - C.A. Meyer
See Adam Szczepaniak’s talk on JPAC
21
π0 model: integration with JPAC
Similar to ρ0 model, simply calculate intensity based on JPAC provided function
Generate ɣp→π0p events and process through full detector simulation and reconstruction
Before Spring 2016 run estimated yields for 12 hours of beam; evaluated statistical precision
Actually collected >10x more data!
Simulation from JPAC Model
V. Mathieu (JPAC) PRD 92, 074013 A Donnachie PRC 93, 025203
12 hours of beam: statistical errors only Σ
June 4, 2016 Meson 2016 - C.A. Meyer
Pseudoscalar Beam Asymmetries
June 4, 2016 Meson 2016 - C.A. Meyer 22
�p ! ⇡0p
�p ! ⌘p
Preliminary
Preliminary
⇠ P⌃⇡0cos 2�
⇠ P⌃⌘ cos 2�
From a subset of all available data. Polarization not yet determined.
Physics Opportunities June 4, 2016 Meson 2016 - C.A. Meyer 23
ρ’?
SLAC:
PRL 53, 751 (1984)
In the ρ event sample, we can look for higher-mass vector mesons. We observe an enhancement around 1.6 GeV with significantly more statistics than existed and we should be able to measure polarization observables.
m⇡+⇡� [GeV/c2]
Four photon final states June 4, 2016 Meson 2016 - C.A. Meyer 24
M(4γ) [GeV/c2]0.0 0.5 1.0 1.5 2.00
100
200
300
400
500
020406080
100120140160180200220
Cand
idat
es /
10 M
eV/c
2
0.0 0.5 1.0 1.5 2.0 2.5M(4γ) [GeV/c2]
Cand
idat
es /
10 M
eV/c
2
π0π0 Region ηπ0 Regionf2(1270)
σ/f0(980)
a0(980)
a2(1320)
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1
10
210
310
M(γγ) for Pair 1 [GeV/c2]
M(γ
γ) fo
r Pai
r 2 [G
eV/c
2 ]
ηπ0
ηπ0
π0π0
�p ! p����
⇡0⇡0
⌘⇡0
⇡0⌘
⌘⌘
About 6% of the spring 2016 statistics from early in the run and using a very preliminary production run. Clear signals for σ, f0(980), f2(1270), a0(980) and a2(1320).
Forward Kaon Identification
June 4, 2016 Meson 2016 - C.A. Meyer 25
Beam Axis
Bar Boxes
FocusingBox andReadout
Existing GlueX Forward Carriage
GlueX DIRCSupport Structure
Time of Flight andForward Calorimeter
• Four of the BaBar DIRC bar boxes will be installed in front of the TOF wall.
• This combined with the other PID systems in GlueX will allow us to fully study final states with strange quarks.
• Strangeonium mesons and hybrids can be studied.
• Hyperon and cascade baryons can be studied. Expected in 2018/2019
GlueX Experiments June 4, 2016 Meson 2016 - C.A. Meyer 26
GlueX—Hybrid mesons/spectroscopy PR-06-102, PR-12-002 & PR-13-003 GlueX—PrimEx-eta PR-10-011 (calorimeter plug) GlueX—Pion polarizability PR-13-008 (forward muon detector) GlueX—JEF: Rare eta decays PR14-004 (calorimeter upgrade)
A rating 340-540 PAC days A- rating 79 PAC Days A- rating 25 PAC Days Conditionally Approved
GlueX Experiments June 4, 2016 Meson 2016 - C.A. Meyer 27
GlueX—Study of ω photoproduction on nuclei. Workshop held in February 2016 https://www.jlab.org/conferences/kl2016/ GlueX—Physics opportunities with a secondary KL beam Workshop held in April 2016 https://www.jlab.org/conferences/photoproduction16/
LOI 2015 LOI 2015
Summary • GlueX is installed, commissioned and ready to start physics running in Fall 2016.
• All detector systems are near design specifications. • We are aggressively moving ahead on our first physics measurements.
• The broader program of exotic mesons is in sight. • Addition of kaon identification and five-times higher intensity is planned in 2018 to allow us to cover all parts of the GlueX exotic hybrid program.
• We have an extensive program beyond exotic hybrids and are excited to have new ideas and new collaborators.
June 4, 2016 Meson 2016 - C.A. Meyer 28