Spin Physics in Jefferson Lab s Hall C Frank R. Wesselmann Norfolk State University
Outline Introduction Jefferson Lab, Hall C Concepts & Definitions Experiments & Measurements Spin as Goal Spin as Tool Summary & Outlook
CEBAF: Continuous Electron Beam Accelerator Facility at the Thomas Jefferson National Accelerator Facility Newport News, Virginia, USA
Introduction Hall C 2 Spectrometer High Momentum Spectrometer, Short Orbit Spectrometer Cryogenic Target:,, solids or: UVa Polarized Target, other options Møller Polarimeter for Beam Compton Polarimeter being added target & detectors
High Momentum Spectrometer movable: 1 dipole magnet, 3 quadrupoles acceptance Q1 Q2 Q3 Dipole 27m shielded detector package scintillator hodoscopes, wire drift chambers gas Cerenkov, segmented Pb glass calorimeter well-studied tracking, reconstruction provides electron ID, event time, momentum & energy determines track position & direction at target
UVa Polarized Target frozen NH, ND He evaporation refrigerator polarizing field remotely movable insert, LiD dynamic nuclear polarization driven by microwaves NMR system for polarization measurement e Beam 4-94 LN 2 Microwave Input To Pumps Magnet Liquid Helium Target (inside coil) 1 K NMR Signal Out NMR Coil B 5T Refrigerator To Pumps Liquid Helium Signal LN 2 7656A1 Frequency
Spin Experiments in Hall C Two Basic Categories of Experiments: Spin is the Goal Polarization Measurements ( ) Spin Structure Functions (RSS, SANE) Spin is a Tool Form Factor Measurements ( Parity Experiments (, ), ) omitting some subjects, e.g. spin-dependent transitions in hyperon nuclear spectroscopy (E-89-009, E-01-011)
Experiments Spin as Goal (E-94-018): Deuteron Tensor Polarization published RSS (E-01-006): Resonance Region Spin Structure Functions ongoing analysis SANE (E-03-109): Spin Asymmetries of the Nucleon Experiment planned, 2007?
E-94-018: Measurement of the Deuteron Tensor Polarization at Large Momentum Transfers in Scattering Ran in 1997 published Coincidence Measurement of Deuteron Tensor Polarization Observables, and Used Target, HMS & Custom Polarimeter Via Analyzing Interaction Target in Secondary Relate to Deuteron Form Factors (monopole), (magnetic dipole) and (quadrupole)
E-94-018: : Measurement via Efficiency of Analyzing Interaction independently from SATURNE and polarization direction of Analyzing Power
Setup: POLDER
Results NRIA NRIA+MEC+RC - Relativistic I - - - - Relativistic II pqcd I - - - - - pqcd II
Results
E-01-006: RSS Nucleon Spin Structure in the Resonance Region Inclusive Scattering, Polarized Beam & Target Proton & Deuteron, & or & or consistent setup, minimal model input ran January March 2002 Dependence Polarized Local Duality GDH Sum Rule Higher Twist Effects &
Asymmetries and Spin Structure #" $ % & ' $ ( ) #* +, - ( ) #* +., / - 021 354 6 798 : 6 3; 8 < = 1 0 > 8 3; 8?1 8 @ A 6 4 6 7B8 C 1 D E 3; 8 F > 8 G > 1 H I > J > 1 @ A K A L 4 3 1 MN O P MN K A @ A QSR TU > P V > Q
RSS Kinematics Example: longitudinal
RSS Results " 0.4 0.3 PRELIMINARY (Uncorrected) RSS A 0.2 0.1 0.0-0.1 deuterons protons -0.2 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 x charge normalized: 0.2 0.1 PRELIMINARY (Uncorrected) RSS A _ _ 0.0-0.1-0.2-0.3 deuterons protons #%$ & Beam Polarization Target Polarization Dilution Factor Radiative Corrections -0.4 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 x
RSS Results based on Hall C fits for and
E-03-109: SANE Spin Asymmetries of the Nucleon Experiment Proton SSF at Large for Resonance Region Systematically Related, Kinematic Dependence Polarized Local Duality Twist-3 Contributions
SANE Proton vs.
SANE Expectations
SANE Setup UVa Polarized Target Big Electron Telescope Array HMS only for Background Studies
BigCal 1744 Pb Glass Blks, 56 Rows @ Event Time, Energy & Position
Experiments: Spin as Tool Form Factor Measurements Neutron E-93-026 (Gen98, Gen01), E-93-038 published Proton E-01-109 (GEp-III), E-04-019 ( ) planned Parity Experiments E-00-006 ( ) ongoing analysis, more planned E-02-020 ( planned )
Form Factors Spacial Extent of Charge & Current (Sub-Structure) Anomalous Magnetic Moment Fundamental Quantities Test of QCD Required for Study of Other Physics e.g. Few-Body Structure Functions
Form Factor Measurements Traditional Methods: Cross Section Based Rosenbluth Separation Highly Sensitive to Wavefunction Models Spin-Based Methods: Polarization Observables (asymmetry, LT-ratio) Complex Setups Asymmetry Measurements Require Absolute Polarization
Formalism Sachs Form Factors for Elastic Scattering Intuitive Interpretation ) point-like probe ( " " Breit frame (NR limit) Fourier Transform of Charge, Current Distribution
" & Basic Approximation: Dipole Fit Phys. Rev. 139, B458 (1965) Based on Exponential Charge Distribution FT fitted to Data: " +-, *) (' "$#% corresp. to
Structure Functions * Form Factors for Elastic Scattering Only More General: Structure Functions and In the Limit of Elastic Scattering ( ):
: Neutron Charge Form Factor " E-93-026 ran in 1998 (Gen98) and in 2001 (Gen01) doubly polarized quasi-elastic scattering: polarized off polarized in measured at and E-93-038 ran in 2000 recoil polarization: polarized scattering off measured at, " and "
*,+ *,+ 1 0 Asymmetry Measurement Formalism - (*) %'& $ #* " * - / - )., 2*5 243 Measurement via Vector Asymmetry 275 263
Asymmetry Measurement Formalism " " " for quasi-free, u y Spin Orientation Plane LAB Frame: ( and ) in scattering plane ( ), k θe k Q= h e Scattering Plane (ω, q) P t θ* φ * u z (along q)
1 0 at QE Kinematics 1 0 For Scattering Quasi-Elastically off Deuterium: 0.1 0.05 G E n =0.5 Galster G E n =1.0 Galster G E n =1.5 Galster 0.1 0.05 Born N N+MEC N+MEC+IC N+MEC+IC+REL 0 0-0.05-0.05-0.1-0.1-0.15 0 50 100 150 200 250 300 350-0.15 100 120 140 160 180 200 220 240 Large Sensitivity to Small Model Dependence Based on Calculations by H. Arenhövel
Gen01 Neutron Detector High Momentum Spectrometer Polarized Target Incoming Beam Line, Chicane Magnet
Gen98, Gen01 Neutron Detector 3 * segmented scintillator 2 VETO layers 6 conversion layers high rate: Protons vertically extended for symmetric proton acceptance (2001) provides 3 space coords, time & energy Beam Height Neutrons 11cm 10 cm 1.0 cm 10 cm (length:160cm) 1998 2001
Recoil Polarimetry Formalism " " Electron scattering plane e e' θ e n t Secondary scattering plane n(p) l θ φ Direct measurement of form factor ratio by measuring the ratio of the transfered polarization and
+ Recoil Polarimetry E93-038 Top Rear Array Bottom Rear Array Front Veto/Tagger Rear Veto/Tagger Lead Curtain Front Array Charybdis To HMS e e Target LD2, LH2 rotate longitudinal pol with Charybdis magnet want to determine and at target polarimeter sensitive to transverse pol only 90 deg. P X = PL, P L, Z (Momentum Direction) δ P, S Polarization Vector + 90 deg. P + X = P, L X
Results G E n 0.1 0.05 E93-026 (01) E93-026 (98) E93-038 Sick and Schiavilla Golak et al (01) Bermuth (00) Ostrick (99) Galster 0 0 0.5 1 1.5 Q 2 (GeV/c) 2 Plans for recoil polarization up to
E-01-109: GEp-III Measurement of Recoil Polarization Expands on Hall A Work: Higher :,, ' Different Systematics Planned 2005/2006
E-01-109: GEp-III Measurement of Recoil Polarization Expands on Hall A Work: Higher :,, ' Different Systematics Planned 2005/2006
in Hall A
Recoil Polarimetry E01-109 Detect Scattered in BigCal Protons in HMS with new Focal Plane Polarimeter HMS Dipole Rotates Polarization Vector y z B χ P fpp x y x P z
E-04-019: TPEX Measurement of the Two-Photon Exchange Contribution in Elastic Scattering Using Recoil Polarization Resolve pol unpol Discrepancy Generalization of Form Factors Examine -Dependence at Fixed Significant New Theory To Run after GEp-III (same setup)
" " " # * 5 E-04-019: TPEX Recoil Polarization: Traditional Extended for TPEX: $ % $ #*
" Form Factors Current Status Data: All Form Factors Measured (,,, ) Models: Several QCD-based Models Vector Meson Dominance pqcd light front CQM, Goldstone Boson Exchange CQM Solitons None Well Describe all Form Factors over Entire Measured Range
G p M / µg D G n M / µg D 1.1 1 0.9 0.8 0.7 10-1 1 10 Q 2 [GeV 2 ] 1.1 1 0.9 VMD + pqcd (Lomon 2002) Soliton (Holzwarth b1) Soliton (Holzwarth b2) µg p E /G p M G n E 1.5 1 0.5 0.1 0.075 0.05 0.025 0 2 4 6 8 Q 2 [GeV 2 ] PFSA CQM GBE LF CQM qff (Cardarelli) LF CQM π (Miller) 10-1 1 Q 2 [GeV 2 ] 0 0 0.5 1 1.5 2 Q 2 [GeV 2 ]
Parity Experiments Theory Include Weak Interaction in Scattering:,,, Cross Section Interference Term Violates Parity *
Parity Experiments Theory " " " " With Measurements at 2 Different, can Extract and Separately 5 %
" Flavor Singlet " " Assuming Isospin Symmetry, get Weak Part of Quark Form Factors in Proton:
Expectations
E-02-020: The Experiment A Search for Physics at the TeV Scale Via a Measurement of the Proton s Weak Charge Recall Polarized Scattering Asymmetry: For Forward Scattering (, ", " ): "
Expectations " " SLAC E158 Result for
Setup
Summary & Outlook Hall C Well Situated & Equipped to Utilize Jefferson Lab s Polarized CW Beam Extensive Experimental Program Measuring & Using Spin: Deuteron Tensor Polarization Spin Structure Functions Proton & Neutron Form Factors Ongoing Efforts and Planned Measurements: up to ', up to Measure TPEX, Resolve pol unpol Ground-Breaking Parity Experiments Planned and Upgrade to Accelerator...