seema dhamija for the gluex collaboration florida international university seema dhamija qnp09,...

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


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.


→ → →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


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.


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-+


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.


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).


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


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-, …….


-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


•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


~100metersConstruction has recently begun and will be completed Fall 2011. (Buildings only, detectors will follow)


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


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


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


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.


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


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


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


5/29/09 CIPANP 2009 -- The GlueX Detector -- David Lawrence (JLab) 23Page 23

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

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


X = Y = 0, Z = 65 cmX = Y = 0, Z = 65 cm

Electromagnetic Background

Hadronic Events

Signal Events

Electromagnetic Background

Hadronic Events

Signal Events


Hit MultiplicityHit Multiplicity


Hit OccupancyHit Occupancy


Total Rate10.5 MHz – 1cm3.7 MHz – 2 cm

Total Rate10.5 MHz – 1cm3.7 MHz – 2 cm


Studied SC acceptancefor events produced byordinary photoproductionProcesses (PYTHIA)


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


Proton required to have a hit in the SCProton required to have a hit in the SC


seema dhamija for the gluex collaboration florida international university seema dhamija qnp09,...

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