Seema Dhamijafor the GLUEX collaboration
Florida International UniversityFlorida International University
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Physics Goals
Meson Spectroscopy
Gluonic Excitations
Current Evidence
The Next Generation Experiment
Jlab Upgrade and GlueX
Summary
Physics Goals
Meson Spectroscopy
Gluonic Excitations
Current Evidence
The Next Generation Experiment
Jlab Upgrade and GlueX
Summary
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
The goal of the GlueX experiment is to map out the spectrum of exotic hybrid mesons In the light quark sector. The experimental information about this spectrum is essentialIn addressing one of the fundamental issues in physics :
A detailed understanding of the nature of the confinement of quarks and gluons in QCD.
Flux tubes lead to a linear, confining potential.
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
→ → →S = S1 + S2
→ → →J = L + S
P = (-1)L+1
C = (-1)L+S
JPC = 0-+ : π, K JPC = 1-- : ρ, K* , γ
With three light quarksthe conventional mesons form flavor nonets – for each JPC
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
How do we look for gluonic degrees of freedom in spectroscopy?
The flux tube model provides us with a framework within which we can understand gluonic excitations and their properties.
When the flux tube is in its ground state – conventional mesons occur.When the flux tube is excited, hybrid mesons result.
Normal mesons:glue is passive
Hybrid mesons:glue is excited
First excited state :Two degenerate transverse modes with J = 1(clockwise and counter-clockwise)Linear combinations lead to JPC = 1-+ or JPC = 1 +-
for excited flux tube
The quantum numbers of the excitedflux tube, when combined with those of the quarks can lead to exotic quantum numbers.
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
JPC = 1-- or 1++
L = 0, S = 0
JPC = 0-+, 1+-, 2-+
JPC = 0+-, 1-+, 2+-
L = 0, S = 1exotic
Photoproduction more likelyto produce exotic hybrids
JPC = 0-+ : π, K Ground State JPC = 1-- : ρ, K* , γ
Excited StateJPC = 1+- or 1-+
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Flux – tube model: 8 degenerate nonets1++, 1- - 0-+, 0+-, 1-+, 1+-, 2-+, 2+- ~ 1.9 GeV/c2
S=0 S=1
Lattice calculations --- 1-+ nonet is the lightest
Collab. 1-+ Mass (GeV/c2)
UKQCD (97) 1.87 ± 0.20
MILC (97) 1.97 ± 0.30
MILC (99) 2.11 ± 0.10
SESAM (98) 1.9± 0.20
Mei(03) 2.01 ± 0.10
Bernard (04) 1.79 ± 0.14
~ 2.0 GeV/c2
1-+
0+-
2+-
Splitting ≈ 0.20
→GlueX wants to map out the hybrid mesons ←Measurement of the excited QCD potential
The ‘S+P’ selection rule for hybrid decaysleads to complicated decay modes of hybrids-which could explain why they have not been seen earlier.
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Have gluonic excitations been observed?
π1(1400) : π – p → η π – p (18 GeV) (E852) Crystal Barrel : antiproton-neutron annihilation Same strength as the a2.
PDG value M = 1376 ± 17 MeV, Г = 300 ± 40 MeV. Decays: only ηπ
Π1(1600) : π – p → ρp → π+ π – π – p (E852) Decays ρπ, η’π, f1π, b1π Only seen in πp production, (E852+VES) PDG value M= 1596 MeV, Г = 312 MeV.
Π1 (2000) : Weak evidence in preferred hybrid modes f1π and b1π Needs confirmation.
These states are not without controversy and thedecay modes are not what is expected.
Revisiting π1 (1600) → ρπDzierba et al. PRD 73 (2006)No evidence for the π1(1670).
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Evidence is tantalizing but not strong.
In a nonet, there should only be one π1 state.
Unambiguous discovery of exotic hybrid mesons requires a detailed knowledge
of the full meson spectrum and understanding of multiple decay modes.
Exotic states are expected to be relatively broad.
Identify the JPC of a meson
Determine production amplitudes & mechanisms
Include polarization of beam, target, spin and parity of
resonances and daughters, relative angular momentum
Assumptions in amplitude analyses must be well understood and controlled.
Need PWANeed PWA
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
DetectorDetector•Large & uniform acceptance•Good calorimetry•(multiple γs )•Good momentum resolution•Charged particle ID•Handle high luminosity
γ- beam (σexotic -meson)γ- beam (σexotic -meson)•High enough in energy (to produce hybrids)•High luminosity•Linearly polarized (parity)•Diffractive production N: JP = 0+, 1-, 2+, …….•Exotic production•U: JP = 0-, 1+, 2-, …….
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
-why is the photon so special?
Π beam•Π with excited flux tube : m=1, S=0, L=0, J=1 JPC = 1++ 1--
•Quark spin flip → exotic hybrids BUT σexotic-meson reduced (« σmeson )•Lot of data but little evidence for hybrids
γ beam•qq with excited flux tube : m=1, S=, L=0, J=0,1,2 JPC = 0-+ 0+- 1-+ 1+- 2-+ 2+-
• σexotic-meson ≈ σmeson •Almost no data available
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
•Continuous-wave
(1497 MHz, 2ns bunch structure
In halls)
•Polarized electron beam
•Upgrading to 12 GeV
(from 6 GeV)
•70 μA max @ 12 GeV
(200 μA max @ 6GeV)
Electron beam acceleratorElectron beam accelerator
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
~100metersConstruction has recently begun and will be completed Fall 2011. (Buildings only, detectors will follow)
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
4
1.5T dipole magnet
12m long vacuum chamber
e-
20m diamond radiator
photon energy (GeV)
coherent bremstrahlung spectrum
Microscope:• Movable to cover different energy ranges• 100 x 5 scintillating fibers (2mm x 2mm)• 800MeV covered by whole microscope• 100MHz tagged /sec on target• ~8MeV energy bite/column
Fixed array hodoscope:• 190 scintillators• 50% coverage below 9GeV • 100% coverage above 9GeV • Tags 3.0-11.7 GeV• ~30MeV energy bite/counter• 3.5 – 17 MHz/counter
Photon Polarization:• 20 m diamond radiator• Coherent peak is linearly polarized• ~40% polarization with peak @ 9GeV• Peak location tunable with diamond angle
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
2.2 TeslaSolenoid •2.2 T superconducting solenoidal magnet
•Fixed target (LH2)•108 tagged γ/s (8.4-9.0 GeV)•hermetic
Charged particle tracking• Central drift chamber (straw tube)• Forward drift chamber (cathode strip)
Calorimetry• Barrel Calorimeter (lead, fiber sandwich)• Forward Calorimeter (lead-glass blocks)
PID• Time of Flight wall (scintillators)• Start counter• Barrel Calorimeter
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Electronics• All digitization electronics are fully pipelined (VME64x-VXS)
F1TDC (60 ps, 32 ch. or 115 ps 48 ch.)125 MHz fADC (12 bit, 72 ch.)250 MHz fADC (12 bit, 16 ch.)
• Trigger latency ~3 s• 3GB/s readout from front end• 300MB/s to mass storage•3PB/yr to tape
Offline software• C++ object oriented framework (JANA)• Multi-threaded event processing• Highly modular through use of templates
Crate Trigger Processor
F1TDC
Level 1 trigger test stand
Signal distribution board
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Understanding confinement requires an understanding of the glue that bindsquarks into hadrons.
Hybrid mesons are perhaps the most promising laboratory.
Future studies with the GlueX experiment at Jlab, provide the hope for improvedexperimental results and interpretations.
Photoproduction promises to be rich in hybrids, starting with those having exotic quantum numbers where little or no data exist.
The GlueX experiment will provide for the detailed spectroscopy necessary to map out the hybrid meson spectrom.
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Barrel Calorimeter:• 191 layer Pb-scintillating fiber sandwich (15.5Xo)• 12.5% sampling fraction• 1152 + 192 = 1344 readout sections/end•E/E= (5.54/√E 1.6) %•z = 5mm/√E•t = 74ps/√E 33ps• angular coverage 11o<< 120o
Forward Calorimeter:• 2800 F8-00 and F108 (center) Pb-glass blocks• 4cm x 4cm x 45cm•E/E= (5.7/√E 2.0) %•xy = 6.4mm/√E• angular coverage 2o<< 11o
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Central Drift Chamber:• 3522 straw tubes (1.6cm diameter)• 12 axial layers, 16 stereo layers (6o)•dE/dx for p< 450 MeV/c•r = 150m• angular coverage 6o<<155o
Forward Drift Chamber:• 4 packages, 6 planes/package, 96 wires/plane (2304 sense wires)• cathode strip readout (48 planes x 216 strips/plane = 10,368 strips)•r = ~200m perpendicular to wire (drift time)•s = ~200m along wire (cathode strips)• angular coverage 1o<<30o
p/p : 1.5 - 3.0%
: 1 - 8 mrad
: 2 – 3 mrad
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
diff
(ps)
•p separation <450MeV/c•K separation <275MeV/c
Barr
el C
alor
imet
erFo
rwar
d TO
F
diff
(ns)
~200 ps
~80 ps
CDC
dE/d
x
• 40 scintillators• 300 ps (w/tracking)• Used for start-up
Star
t Cou
nter
Particle ID is done primarily through time of flight with some help from dE/dx in chambers. Space is left in design for a future PID detector.
Beam Test Data Expected Separation
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
5/29/09 CIPANP 2009 -- The GlueX Detector -- David Lawrence (JLab) 23Page Page 2323
CapabilityCapability QuantityQuantity RangeRange
Charged particlesCharged particles CoverageCoverage 11oo<<< 160< 160oo
Momentum Resolution (5Momentum Resolution (5oo-140-140oo)) pp/p = 1 /p = 1 − − 3%3%
Position resolutionPosition resolution ~ 150-200 ~ 150-200 mm
dE/dx measurementsdE/dx measurements 20 <20 << 160< 160oo
Time-of-flight measurementsTime-of-flight measurements ToFToF ~ 60 ps; ~ 60 ps; BCal BCal ~ 200ps~ 200ps
Barrel time resolutionBarrel time resolution t t < (74 /< (74 /√E 33) ps√E 33) ps
Photon detectionPhoton detection Energy measurementsEnergy measurements 22oo<<< 120< 120oo
LGD energy resolution (E > 60 MeV)LGD energy resolution (E > 60 MeV) EE/E = (5.7//E = (5.7/√E 2.0)%√E 2.0)%
Barrel energy resolution (E > 60 MeV)Barrel energy resolution (E > 60 MeV) EE/E =(5.54//E =(5.54/√E 1.6)%√E 1.6)%
LGD position resolutionLGD position resolution x,y,x,y, ~ 0. 64 cm/√E ~ 0. 64 cm/√E
Barrel position resolutionBarrel position resolution zz ~ 0.5cm / ~ 0.5cm /√E√E
DAQ/triggerDAQ/trigger Level 1Level 1 < 200 kHz< 200 kHz
Level 3 event rate to tapeLevel 3 event rate to tape ~ 15 kHz~ 15 kHz
Data rateData rate 300 MB/s300 MB/s
ElectronicsElectronics Fully pipelinedFully pipelined 250 / 125 MHz fADCs, TDCs250 / 125 MHz fADCs, TDCs
Photon FluxPhoton Flux Initial: 10Initial: 1077/s/s Final: 10Final: 1088/s/s
Hall D: Detector Design ParametersHall D: Detector Design Parameters
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Start Counter• Which tagged e- belongs to γ?
• Level-1 hardware trigger
•Array of ~ 40 scintillators with bent ends
•Read out by high field (fine mesh) PMT
•500 mm Straight + 100 mm bended (35o)
•Maximal solid angle coverage
•High rate capability
•Energy and timing measurements
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
X = Y = 0, Z = 65 cmX = Y = 0, Z = 65 cm
Electromagnetic Background
Hadronic Events
Signal Events
Electromagnetic Background
Hadronic Events
Signal Events
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Hit MultiplicityHit Multiplicity
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Hit OccupancyHit Occupancy
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Total Rate10.5 MHz – 1cm3.7 MHz – 2 cm
Total Rate10.5 MHz – 1cm3.7 MHz – 2 cm
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Studied SC acceptancefor events produced byordinary photoproductionProcesses (PYTHIA)
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Start counter hit multiplicityas a function of photon beam energy Start counter hit multiplicityas a function of photon beam energy
SC hit multiplicity , Eγ > 8 GeVSC hit multiplicity , Eγ > 8 GeV
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Proton required to have a hit in the SCProton required to have a hit in the SC
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009
Seema DhamijaQNP09, IHEP, Beijing – 22/09/2009