Physics Goals & Overview K. Slifer, UNH April 18, 2011 E08-027/007 Collaboration meeting

Inclusive Scattering ° * Q 2 : 4-momentum transfer X : Bjorken Scaling var W : Invariant mass of target Kinematics 1 st order Feynman diagram

Inclusive Scattering ° * Inclusive Cross Section deviation from point-like behavior characterized by the Structure Functions 1 st order Feynman diagram Q 2 : 4-momentum transfer X : Bjorken Scaling var W : Invariant mass of target

Inclusive Scattering ° * When we add spin degrees of freedom to the target and beam, 2 Addiitonal SF needed. Inclusive Polarized Cross Section SFs parameterize everything we don’t know about proton structure

E : Proton g2 Structure Function Physics Goals : Proton g 2 structure function has never been measured at low or moderate Q 2. Primary Motivation Determine this fundamental quantity to the lowest possible Q 2 at JLab. Use this new data to clarify several outstanding puzzles Hydrogen HyperFine Splitting : Lack of knowledge of g 2 at low Q 2 is one of the leading uncertainties. Proton Charge Radius : also one of the leading uncertainties in extraction of from  H Lamb shift. A - rating by PAC33 A. Camsonne, D. Crabb, J.P. Chen, K. Slifer (contact)

Structure dependent effects in Q.E.D. Hydrogen Hyperfine Structure Proton Charge Radius Systematic uncertainty In Measurements of Measure of QCD complexity Ideal place to test ÂPT calcs Spin Polarizability SUM Rules Extended GDH SUM BC SUm Rule ELT SUM Rule

Spin Polarizabilities Major failure (>8  of  PT for neutron  LT. Need g 2 isospin separation to solve. this is the region we should start to be able to trust  PT

Spin Polarizabilities Major failure (>8  of  PT for neutron  LT. this is the region we should start to be able to trust  PT similar problem for proton  0

Burkhardt Cottingham Sum Rule predicted to vanish for all Q 2 = 0

BC Sum Rule P N 3 He BC satisfied w/in errors for 3 He BC satisfied w/in errors for Neutron (But just barely in vicinity of Q 2 =1!) BC satisfied w/in errors for JLab Proton 2.8  violation seen in SLAC data 0<x<1

E : Proton g 2 Structure Function Fundamental spin observable has never been measured at low or moderate Q 2 BC Sum Rule : violation suggested for proton at large Q 2, but found satisfied for the neutron & 3 He. Spin Polarizability : Major failure (>8  of  PT for neutron  LT. Need g 2 isospin separation to solve. Hydrogen HyperFine Splitting : Lack of knowledge of g 2 at low Q 2 is one of the leading uncertainties. Proton Charge Radius : also one of the leading uncertainties in extraction of from  H Lamb shift. A - rating by PAC33 Camsonne, Crabb, Chen, Slifer* nucleus ≈ Atom ≈ The finite size of the nucleon (QCD) plays a small but significant role in calculating atomic energy levels in QED.

Proton Charge Radius from  P lamb shift disagrees with eP scattering result by about 6% = ± fm Lamb shift in muonic hydrogen = ± fm World analysis of eP scattering = ± fm CODATA world average R. Pohl et.al Nature, July 2010 I. Sick PLB, 2003

Proton Charge Radius from  P lamb shift disagrees with eP scattering result by about 6% = ± fm Lamb shift in muonic hydrogen = ± fm World analysis of eP scattering = ± fm CODATA world average R. Pohl et.al Nature, July 2010 I. Sick PLB, 2003 Possible Implications : Some experimental mistake ? Fairly straightforward spectroscopy. Rydberg constant off by 5  ? Really unlikely. We don’t know how to calculate in QED ? Missing some terms? Something about muons we don’t understand ? Underestimating finite size effect uncertainties?

Polarizability : Integrals of g 1 and g 2 weighted by 1/Q 4 Zemach radius : Integral of G E G M weighted by 1/Q 2 Dominated by Kinematic region of E and E08-007

Experimental Technique Inclusive measurement of Polarized Cross section differences Need polarized beam polarized target small angle to reach lowest Q 2

Accessing the polarized SFs − P P

−− P P P P

Local dump Floor Layout

Upstream chicane Septa Local dump Polarized NH 3 target Not meant to be a factual representation Floor Layout

5 T field Split Helmholtz pair superconduct magnet 1K 4 He evaporation refrigerator Cooling power: about 1 W Microwave Power 1W at 140 GHz to pump electrons Insulated cryostat 85 L Liquid He resevoir 57 L Liquid N shield (300K BB shield) Dynamic Nuclear Polarization of NH 3

Source(%) Cross Section5-7 Target Polarization3 Beam Polarization3 Radiative Corrections3 Parallel Contribution<1 Total7-9 Systematic Error Budget

BC Sum Rule Spin Polarizability  LT Projected Results

Projected Kinematics EG4: g1pE : g2p 0.02 < Q 2 < 0.5 GeV 2 Resonance Region

Projected Kinematics The proposal kinematics were modified to allow for use of room temperature septa (co-existence with QWeak). This lead to a small gap in coverage at large Q 2, but the min Q 2 was still about 0.02 GeV 2

Projected Kinematics The proposal kinematics were modified to allow for use of room temperature septa (co-existence with QWeak). This lead to a small gap in coverage at large Q 2, but the min Q 2 was still about 0.02 GeV 2

But....., the 5T magnet field wreaks havoc with the scattering plane. especially at low momentum RECENT DEVELOPMENTS

But....., the 5T magnet field wreaks havoc with the scattering plane. especially at low momentum Effect discovered by Jixie Zhang (Geant4). confirmed by Min Huang (Snake) RECENT DEVELOPMENTS

This pushes all the low momentum data to higher Q 2 Out of plane scattering angle correction

Proposed Solution run the two lowest energies with only 2.5 T target field & Elevate the target 9 cm above nominal scattering plane.

Proposed Solution run the two lowest energies with only 2.5 T target field & Elevate the target 9 cm above nominal scattering plane.

Proposed Solution get back to about 0.03 GeV 2 run the two lowest energies with only 2.5 T target field & Elevate the target 9 cm above nominal scattering plane. but 2.5T => P T = 40%

Proposed Solution get back to about 0.03 GeV 2 run the two lowest energies with only 2.5 T target field & Elevate the target 9 cm above nominal scattering plane. but 2.5T => P T = 40% can regain some stat by changing from 0.5 cm target to 3 cm. but still expensive (more later)

These new degrees of freedom would allow us to manipulate the kin coverage in ways usually impossible option GeV 2.5 T 9cm

option GeV 5.0 T 9cm

option GeV 5.0 T 0cm

Bottom Line All the physics proposal goals appear to still be attainable. Net result is a shift of lowest Q 2 from 0.02 to 0.03 GeV 2 Assuming that the following are all feasible: -We can polarize efficiently at 2.5T (~40%). (equipment available, swapping out during run, lifetime....) -The radiative corrections are not too horrible for a 3 cm cell instead of the previously planned short cell. -We can elevate the target by 9 cm and switch back (only once) during the experiment.

UNH Physics Manpower Post-Docs James Maxwell : Finishing thesis work. Will be onsite fulltime for entire experimental run. Will participate in all major target work before run. Sarah Phillips : partime. Many other obligations, but has volunteered as R.C. Graduate Students Ryan Zielinski (UNH) : onsite fulltime starting June 1 Tobias Badman (UNH): onsite fulltime starting June 1 Faculty Karl Slifer : onsite fulltime summer and fall. onsite fullttime every other week in spring. Undergraduate Student John Donaghy (UNH) : Developing target expert (NMR/Labview)

Rates / Schedule assuming option GeV 5.0 T 9cm (rates code update with help from Ryan Zielinski.)

g2p Runplan (assuming option 2)

g2p Runplan (assuming option 2)

g2p Runplan (assuming option 2)

g2p Runplan (assuming option 2)

Overhead Assumptions ~22 days

g2p and Gep allocation as of Nov. 17 (Kees estimate) E0 (GeV) Angle (deg) Calendar days allocated 2.2 commis Septa Removal no commis Total77

g2p and Gep allocation as of Nov. 17 (Kees estimate) E0 (GeV) Angle (deg) Calendar days allocated g2p needed gep needed 2.2 commis Septa Removal no commis Total

g2p and Gep allocation as of Nov. 17 (Kees estimate) E0 (GeV) Angle (deg) Calendar days allocated g2p needed gep needed 2.2 commis Septa Removal no commis Total summary We need something like 119 days to meet the proposal goals. We are allocated 77 Need to optimize physics Need to optimize overhead

Major Milestones May 6, 2011 : g2p/gep readiness review: Readiness review in 19 days May 14, 2011 : Start of 6 month down. Installation begins in 27 days. Nov 19, 2011 : Beam to hall. Commissioning begins in 216 days. Dec 03, 2011 : Production 6 degrees. Jan 23-Mar 16, 2012 : Septa removed. Mar 17, 2012 : Start Production 12.5 degrees. April 26, 2012 : Completion of production data. May 14, 2012 : Start of 12 month upgrade.