1Elton S. Smith University of Virginia October 25, 2005

OverviewBremsstrahlung Tagging Spectrometer

and Photon Beam Review

Elton S. Smith

Jefferson Lab

RequirementsSummary of beamline and ratesStatus of project

2Elton S. Smith University of Virginia Oct 25, 2005

Normal mesons:glue is passive

Hybrid mesons:glue is excited

qq

q q

The physics goal of GlueX is to map the spectrum of hybrid mesons starting with those with the unique signature of exotic JPC .

Identifying JPC requires an amplitude analysis which in turn requires• linearly polarized photons• detector with excellent acceptance and resolution• sensitivity to a wide variety of decay modes which include photon and charged particles

This, coupled with a hybrid mass reach up to 2.5 GeV, requires 9 GeV photons produced using coherent bremsstrahlung from 12 GeV electrons.

Physics goals and key features

3Elton S. Smith University of Virginia Oct 25, 2005

The GlueX Detector Design has been driven by the need to carry out Amplitude analysis.

p

X

n,p

Photoproduction

1 → a+1 → ()() →

h0 → bo1→ () →

Final state particles ± K± p n KL

h’2 → K+1K− → o K+ K− → +−K+K−

1 1 ’1 b2 h2 h’2 b0 h0 h’0

all charged

many photons

strange particles

1−+ 2+− 0+−

Search for QCD Exotics

4Elton S. Smith University of Virginia Oct 25, 2005

Mass Predictions

Lowest mass expected to be 1(1−+) at 1.9±0.2 GeV

Lattice 1-+ 1.9 GeV2+- 2.1 GeV0+- 2.3 GeV

5Elton S. Smith University of Virginia Oct 25, 2005

Line shape distortion

M=2.5 GeV M=2.8 GeV

MX (GeV)

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p p

M

J=0– or 0+

V

X

photon

for X, J = 0

Center of Mass of V

X = exchange particle

L 0, 1, or 2

PV P PX 1 L

V = vectorphoton

m = 1

m = -1

R

L

AN AU

Parity conservation implies:

are sensitive to production mechanism

V = vectorphoton

m = 1

m = -1L AN AU

7Elton S. Smith University of Virginia Oct 25, 2005

Strategy for Exotic Meson Discovery Use 8 – 9 GeV polarized photons (12 GeV electron beam)

─ Sensitivity to mesons masses up to 2.5 GeV

─ Expect production of hybrids to be comparable to normal mesons

─ Dearth of experimental data

Use hermetic detector with large acceptance

─ Decay modes expected to have multiple particles

─ hermetic coverage for charged and neutral particles

─ high data acquisition rate to enable amplitude analysis

Perform partial-wave analysis

─ identify quantum numbers as a function of mass

─ check consistency of results in different decay modes

8Elton S. Smith University of Virginia Oct 25, 2005

Requirements for photon beam

Coherent peak ~ 8.4 ─ 9 GeV

Linear polarization

High rates

─ Initial running at 107 /s in the coherent peak

─ Design system with a clear path to 108 /s

9Elton S. Smith University of Virginia Oct 25, 2005

6 GeV CEBAF

CHL-2CHL-2

Upgrade magnets Upgrade magnets and power and power suppliessupplies

12

Enhance equipment in Enhance equipment in existing hallsexisting halls

add Hall D (and beam line)

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Hall D Complex

Accelerator East Arc

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Top View

75 m

Tagger Area

ExperimentalHall D

Electron beam

Coherent Bremsstrahlungphoton beam

Solenoid-Based detectorCollimator

PhotonBeam dump

East arc

North linac

Tagger area

Hall D

ElectronBeam dump

Photon beam and experimental area

12Elton S. Smith University of Virginia Oct 25, 2005

GlueX / Hall D Detector

Electron Beam from CEBAF

Lead GlassDetector

Solenoid

Coherent BremsstrahlungPhoton Beam

Tracking

TargetCerenkovCounter

Time ofFlight

BarrelCalorimeter

Note that tagger is80 m upstream of

detector

Detector ReviewOct 20-22, 2004

13Elton S. Smith University of Virginia Oct 25, 2005

GlueX detectorCapability Quantity Range

Charged particles Coverage 1o < < 170o

Momentum Resolution (5o-140o) p/p = 1 − 2%

Position resolution = 150-200 m

dE/dx measurements 20 < < 140o

Time-of-flight measurements t = 60 ps

Cerenkov and /K separation < 14o

Barrel time resolution t < (150 + 50 /√E) ps

Photon detection Energy measurements 2 < < 120o

Veto capability > 120o

Barrel energy resolution (E > 20 MeV) E/E = (2 + 5/√E)%

Lead glass energy resolution (E > 100 MeV) E/E = (3.6 + 7.3/√E)%

Barrel position resolution z ~ 4 cm

Lead glass position resolution x,y = 0.7 cm

DAQ/trigger Level 1 200 kHz at 108/s

Level 3 event rate to tape 15 kHz

Data rate 100 MB/s

Electronics Fully pipeline Flash ADCs, multi-hit TDCs

Photon Flux Tagged rate Initially: 107 /s, Final: up to 108 /s

14Elton S. Smith University of Virginia Oct 25, 2005

The GlueX collaboration has designed and optimized the detector to study gluonic excitations. Many university groups have contributed to the R&D and development of major subsystems.

• Solenoid JLab

• Detectors• Tracking Carnegie Mellon, Ohio U, Florida International U

• Calorimetry U of Regina, Florida State, Indiana U, Inst for High Energy Physics (Protvino), U of Athens

• PID Indiana U, Inst for High Energy Physics, U of Tenn, ORNL

• Computing JLab, U of Regina, Indiana U, Carnegie Mellon, U Connecticut, Christopher Newport U

• Electronics Indiana U, JLab, U of Alberta, Indiana U Cyclotron

• Beamline Catholic U of America, Glasgow U, U of Connecticut

• Infrastructure JLab

Institutional Responsibilities

15Elton S. Smith University of Virginia Oct 25, 2005

Interface between accelerator and Hall D

The accelerator will be responsible for the electron beamline, and Hall D will be responsible for the photon beam. This is the nominal breakdown of responsibilities, with additional clarification in the next two paragraphs.

The accelerator will deliver and monitor the 12 GeV electron beam to the radiator immediately upstream of the tagger magnet. The accelerator will also be responsible for steering the beam to the electron beam dump. Some monitoring of the electron beam at the dump may be required to insure accurate delivery.

Hall D will be responsible for purchasing and qualifying the crystal radiators, all aspects of the tagger magnet and hodoscope systems, collimation of the photon beam immediately upstream of the photon hall, and monitoring of the photon beam from the radiator to the photon beam dump behind the GlueX detector.

16Elton S. Smith University of Virginia Oct 25, 2005

flu

x

photon energy (GeV)

12 GeV electrons

This technique provides requisite energy, flux

and polarization

collimated

Incoherent &coherent spectrum

tagged

0.1% resolution

40%polarization

in peak

electrons in

photons out

spectrometer

diamondcrystal

Coherent Bremsstrahlung

Hadronic Backgrounds

17Elton S. Smith University of Virginia Oct 25, 2005

High sensitivity → high rates

Start with

8.4 - 9.0 GeV Tagged

107 / s

current 300 nA

radiator 10 4

No 2 108 / s

30 cm targetcross section = 120 µb

R taggedhadronic 1.4 kHz R total

hadronic 37 kHzlow-rate

high-rates: multiply by factor of 10

18Elton S. Smith University of Virginia Oct 25, 2005

peak energy 8 GeV 9 GeV 10 GeV 11 GeV

N in peak 185 M/s 100 M/s 45 M/s 15 M/s

peak polarization 0.54 0.41 0.27 0.11 (f.w.h.m.) (1140 MeV) (900 MeV) (600 MeV) (240 MeV)

peak tagging eff. 0.55 0.50 0.45 0.29 (f.w.h.m.) (720 MeV) (600 MeV) (420 MeV) (300 MeV)

total hadronic rate 385 K/s 365 K/s 350 K/s 345 K/s(in tagged peak) (26 K/s) (14 K/s) (6.3 K/s) (2.1 K/s)

1. Total hadronic rate is dominated by the resonance region

2. For a given electron beam and collimator, background is almostindependent of coherent peak energy, comes mostly from incoherent part.

3. The following assumes a 12GeV electron beam energy.

Photon Beam Rates and Backgrounds

19Elton S. Smith University of Virginia Oct 25, 2005

Today’s presentations

Photon beam

Electron beam

4. Tagger magnet design5. Spectrometer optics

Vacuum chamber

75 m

Electron beamDetectorCollimator

PhotonBeam dump

Hodoscope:6. Fixed array and beam monitoring7. Tagger Microscope

1. Overview2. Photon beam3. Simulation and backgrounds

20Elton S. Smith University of Virginia Oct 25, 2005

Architect’s rendering of Hall D complex

Service Buildings

Hall D

Cryo Plant

Counting House

22Elton S. Smith University of Virginia Oct 25, 2005

JLab 12 GeV Upgrade Project Status

Successful Project Review (Jul 2005), CD-1 expected soon

Four-year construction project planned to start in FY08

Review of Science program for the 12-GeV Upgrade (Apr 2005)From the Executive Summary: “After a decade of research, we should know whether the formation of flux tubes by the gluon fields is the mechanism of confinement…”

Highlight in the 20-year plan of the Office of Science (2003)

What’s New: “New supercomputing studies indicate that force fields called “flux-tubes” may be responsible [for the mechanism that confines quarks], and that exciting these should lead to the creation of never-before-seen particles.”

Determination of “Mission Need” CD-0 (Apr 2004)

23Elton S. Smith University of Virginia Oct 25, 2005

GlueX Reviews

December 1999: PAC Requested Review of the GlueX ProjectD. Cassel (chair), J. Domingo, W. Dunwoodie, D. Hitlin, G. Young.

April 2001: NSAC Long Range Plan Committee.

July 2003: Electronics Review of the GlueX ProjectJ. Domingo, A. Lankford, G. Young (chair)

October 2004: Detector ReviewM. Albrow, J. Alexander (Chair), W. Dunwoodie, B. Mecking.

December 2004: Solenoid AssessmentJ. Alcorn, B. Kephart (Chair), C. Rode.

All of these review committees have both identified areas that were unsettled and made excellent suggestions for improvements

24Elton S. Smith University of Virginia Oct 25, 2005

Hall D Organizational Chart

Proposal for mergingGlueX collaboration with12-GeV Upgrade ProjectOrganization reflectsthe WBS outline

25Elton S. Smith University of Virginia Oct 25, 2005

Summary Mapping the spectrum of hybrid mesons provides essential

experimental data on the physics of the strong interactions at low energies in the region of confinement.

This unique experimental program is possible now due to

─ increases in computational power

─ new developments in detector readout technology

─ to high quality electron beam at the 12-GeV CEBAF Upgrade

─ technology to produce thin diamond crystals

You are asked today to review the conceptual design of the Hall D tagger spectrometer and the design parameters of the photon beam for use in this experimental program.