Jefferson Lab and the 12GeV Upgrade

Nuclear Physics UK Community MeetingCosener’s House 11th & 12th June 2009

Ken Livingston, University of Glasgow

• Overview of Jefferson Lab and the 12 GeV upgade programme

• CLAS Spectrometer (Hall B)

• Latest results from the measurement of polarisation obresvables

• CLAS12

• BigBite (Hall A)

• Latest results on Gen - neutron electric form factor

• Super BigBite

• GlueX (Hall D)

Missing resonances and resonance spectroscopy

• Cross sections not enough to separate broad, overlapping resonances

• Angular distributions and polarization observables.

Polarization observables

+ N → m

Linear Polarisation

Circular polarisation

Nucleon recoil polarimiter x →

Y

Hyperons are “self analysing”

Transverse polarized nucleon targets ?

Longitudinally polarized nucleon targets

Polarization observables in pseudoscalar meson production

g target recoil Observable

4 Complex amplitudes - 16 real polarization observables.

A complete measurement from 8 carefully chosen observables.

I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).

Polarization observables - a simple example,

• Systematics of detector acceptance cancel out.

• Only need to know Plin, the degree of linear polarization.

CLAS data

SAID

High statistics. Good agreement with previous measurement.

Data set extends to photon energy up to 2.1GeV

g8b: July 2005 Polarized photon energy range: 1.3 – 2.1 GeV

Events (single charged particle in CLAS): 10 billion

preliminary results:p+n.Mike Dugger, ASU

g8b preliminary results:p’pMike Dugger, ASU

High stats for .

Good agreement with previous measurements.

Data set extends to photon energy up to 2.1GeV

First measurement of for ’

2 E bins

SAIDMAIDNakayama and Haberzettleffective lagrangian model

g8b preliminary results - and

Craig Paterson, Glasgow

pppp

Single polarization observablesPhoton asymmetryP Recoil polarization (induced pol. along y)T Target asymmetry

Double polarization observablesOx Polarization transfer along xOz Polarization transfer along z

figure by R.Schumacher, CMU

g8b preliminary results -

Results compared with previous results from GRAAL7, 50MeV Energy bins

1175 -> 1475MeV

Good agreement with previous results

PREL

IMIN

ARY

g8b preliminary results -

Results compared with previous results from LEPS6, 100MeV Energy bins

1550 -> 2050MeV

More bins for our data

Increase the angular coverage to backward angles

PREL

IMIN

A

RY

g8b preliminary results -

Ox/O

z extracted from fit to 2d asymmetry

T Target asymmetry from 2d asymmetry (not shown)

P Recoil pol. from acceptance corrected proton dist.

G8bGRAALCLAS J.W.C. McNabb, et al. (CLAS) Phys. Rev. C 69, 042201(R) (2004).

g8b preliminary results - Double polarization ovservable Ox

Results compared with Regge-Plus-Resonance model from Gent group

- Large Polarizations!

- Some evidence for an important role for missing D

13(1900)

state

- Poor agreement at low energy

PREL

IMIN

A

RY

g8b preliminary results - Full lamba polarization ?

With circularly polarized photons – “fully polarized lambda”

R. Bradford et al. (The CLAS Collaboration), Phys. Rev. C 75, 035205 (2007).

- Full polarization at forward angles

- Not repeated over full kinematic range

- More relations can be tested

PREL

IMIN

A

RY

(P

2 +

Ox2 +

Oz2 )

1/2

g13 meson photoproduction, polarized photons on LD2

n (p)ppDaria Sokhan, Edinburgh

MAIDSAID

Previous data

g13 meson photoproduction, polarized photons on LD2

p (n)nRussell Johnstone, Glasgow

n (p)s p

Neil Hassall, Glasgow

Meson photoproduction with linearly and circularly polarized photons on polarized target

E02-112: γp→KY (K+Λ, K+Σ0, K0Σ+)E03-105/E04-102: γp→π0p, π+n E05-012: γp→ηpE06-013: γp→π+π-p

g9a running conditions

November 3, 2007– February 12, 2008Longitudianally polarized targetCircularly and linearly polarized photon beam 0.5-2.4 GeVTrigger: at least one charged particle in CLAS

g9 FROST – FROzen Spin Target

butanol 12C CH2

Helicity asymmetry E Raw asymmetry

g9aFROST sample analysis of gp+n Eugene Pasyuk, ASU

•Select + applying cut on vs. p•Vertex cuts•Select missing neutron

Based on ~2% of statisticsPrelim

inarybutanol 12C CH2

• Circularly polarized photon beam on longitudinally polarized targetE P, Lx/Lz, Cx/Cz

• Linearly polarized photon beam on longitudinally polarized target, G, P, (Tx/Tz) Ox/Oz

• Circularly polarized photon beam on transversely polarized targetT, F, P, Tx/Tz, Cx/Cz

• Linearly polarized photon beam on transversely polarized target, H, T, P, (Lx/Lz)

Upon completion of g9b for the first time we will have complete set of observables in Kaon photoproduction and nearly complete for all other mesons, which will allow model independent extraction of the amplitude for subsequent extraction of baryon resonances and their properties.

g9a Complete

g9b scheduled for 2010

g9 FROST outlook

Recoil polarimetry possibilities (D. Watts, Edinburgh)

+ p → + n with (n,p) scatter (detect +p)

Mx(p→++X)

+

n

p

Use reaction with a known photon asymmetry

• Can be high statistics

• Very good relative monitor of polarization

• Combined beam, target polarization.

• Non-indpendent – depends on specific expt

• Need very good systematics or calibration

• Awaiting MAMI polarized target and polarised photon beam in 2nd half of 2007

Polarimetry: from hadronic reactionR. Beck, Mainz -> Bonn

Recent preliminary results from JLab (g8b)

• Proton target

• Back to back charge particles in Start Counter

• Atomic or hardonic ?

• Asymmetry from ~20mins DAQ data

• Constant with E from 1.3GeV – 1.9GeV

Measurements with photon beam profile detectorD. Glazier, Glasgow

1st Measurement of 2D photon enhancement for coherent bremsstrahlung (MAMI,Mainz) paper in preparation

• Good agreement with coherent bremstrahlung calculations

• Improvements in incoherent component, collimation + multiple scattering.

• No evidence of high energy photons from quasi channeling.

• Investigation of 2D strip detector for polarimetry

Coherent peak at 300Mev, MAMI electron beam energy 855MeV

below peak coherent peak above peak

• Tagging spectrometer with high rate, good energy and timing resolution

• High precision goniometer (GWU)

• High quality, thin diamond (Glasgow)

• Tight photon beam collimation (ISU)

• Polarimetry

“A device called a goniometer tilts the diamond, much like a lady turning her hand to admire the sparkle of a new ring.” - JLAB On Target Magazine

Peak > 90% pol.

CLAS coherent bremsstrahlung facility

Photo

n

ener

gy

P > 90%

Photon Asymmetry, , extracted from cos(2) fit to azimuthal kaon distribution

Fits shown for 1 energy bin

340 (20E, 17) kinematic bins

Almost full angular coverage

g8b preliminary results -

g8b preliminary results -

Results compared with previous results from GRAAL7, 50MeV Energy bins

1175 -> 1475MeV

Good agreement with previous results

PREL

IMIN

A

RY

Results compared with previous results from LEPS6, 100MeV Energy bins

1550 -> 2050MeV

More bins for our data!!!

Increase the angular coverage to backward angles

PREL

IMIN

A

RY

g8b preliminary results -

• Pair production simulations by Kharkov group

• Polarimeter built and tested at Sping8, recently tested at Jlab

e+

e-

• Polarimeter to be based on Jlab design

• Microstrip detectors, or pixel detectors (Atlas group)

• Bonn student completed 10 months exchange in Glasgow now to be full time in Bonn.

Polarimetry: from pair (e+,e-) productionH.Schmieden, Bonn

• Well described by QED, but experimentally difficult – small opening angle

PRELIMINARY

J.Santoro, CUA

Peak > 90% pol.

K.Livingston, Glasgow