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1 Neutron Transversity at Jefferson Lab Introduction SIDIS measurements at JLab JLab Hall-A neutron transversity experiment Other transverse spin experiments.

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Presentation on theme: "1 Neutron Transversity at Jefferson Lab Introduction SIDIS measurements at JLab JLab Hall-A neutron transversity experiment Other transverse spin experiments."— Presentation transcript:

1 1 Neutron Transversity at Jefferson Lab Introduction SIDIS measurements at JLab JLab Hall-A neutron transversity experiment Other transverse spin experiments Other planned SIDIS experiments Summary Jian-ping Chen, Jefferson Lab Transversity Workshop, Como, Italy, Sept. 7-10, 2005

2 Introduction/motivation

3 3 Transversity Three twist-2 quark distributions: –Momentum distributions: q(x,Q 2 ) = q (x) + q (x) –Longitudinal spin distributions: Δq(x,Q 2 ) = q (x) - q (x) –Transversity distributions: δq(x,Q 2 ) = q (x) - q (x) Some characteristics of transversity: –δq(x) = Δq(x) for non-relativistic quarks –δq and gluons do not mix Q 2 -evolution for δq and Δq are different –Chiral-odd not accessible in inclusive DIS It takes two chiral-odd objects to measure transversity –Semi-inclusive DIS Chiral-odd distributions function (transversity) Chiral-odd fragmentation function (Collins function)

4 4 Leading-Twist Quark Distributions No K dependence K - dependent, T-odd K - dependent, T-even ( A total of eight distributions)

5 5 Eight Quark Distributions Probed in SIDIS Unpolarized Polarized target Polarzied beam and target S L and S T : Target Polarizations; λe: Beam Polarization Sivers Transversity

6 6 A UT sin( ) from transv. pol. H target Simultaneous fit to sin( + s ) and sin( - s ) `Collins moments Non-zero Collins asymmetry Assume q(x) from model, then H 1 _unfav ~ -H 1 _fav Need independent H 1 (BELLE) `Sivers moments Sivers function nonzero ( + ) orbital angular momentum of quarks Regular flagmentation functions

7 7 Collins asymmetry from COMPASS COMPASS data: ~ factor of 12 in statistics hep-ex/ Transversely polarized 6 LiD target Cover smaller x Consistent with 0

8 8 Current Status Collins Asymmetries - sizable for proton large at high x large for - - consistent with 0 for deuteron - cancellation between p and n? Sivers Asymmetries - non-zero for p+ from proton - consistent with zero all other channels. Fit by Anselmino et al. and other groups Data on neutron at high x complementary and very helpful

9 SIDIS measurements at JLab

10 10 Thomas Jefferson Accelerator Facility 6 GeV polarized CW electron beam (P = 85%, I = 180 A) 3 halls for fixed target experiments Hall A: 2 high resolution spectrometer Polarized 3 He, L=10 36 cm -2 s -1 Hall B: large acceptance spectrometer Polarized p/d, L=10 34 cm -2 s -1 Hall C: 2 spectrometers Polarized p/d, L=10 35 cm -2 s -1

11 11 Jefferson Lab

12 12

13 13 SIDIS at JLab Extensive SIDIS program with 12 GeV upgrade Starting with 6 GeV running with optimized kinematics High luminosity compensates low rate at larger scattering angle to reach large Q 2 Comparable Q 2 range as HERMES Access high x region Factorization? experimental tests.

14 14 Preliminary results of factorization test from JLab for semi-inclusive pion production Data are well described by calculations assuming factorization Similar z-dependence for different x-bins Hall-C E00-108CLAS 5.7GeV data Recent theory work on SIDIS factorization (hep-ph )

15 Planned neutron transversity experiment at JLab

16 16 JLab Hall-A E Experiment High luminosity (10 36 s -1 ) –15 μA electron beam on 10-atm 40-cm 3 He target Measure neutron transversity –Sensitive to δd, complementary to HERMES Disentangle Collins/Sivers effects Probe other K -dependent distribution functions Single Target-Spin Asymmetry in Semi- Inclusive Electroproduction on a Transversely Polarized 3 He Target Argonne, CalState-LA, Duke, E. Kentucky, FIU, UIUC, JLab, Kentucky, Maryland, UMass, MIT, ODU, Rutgers, Temple, UVa, W&M, USTC-China, CIAE-China, Glasgow-UK, INFN-Italy, U. Ljubljana-Slovenia, St. Marys- Canada, Tel Aviv-Israel, St. Petersburg-Russia Spokespersons: J.-P. Chen (JLab), X. Jiang (Rutgers), J. C. Peng (UIUC)

17 Jefferson Lab Hall A Experimental Setup for polarized n ( 3 He) Experiments BigBite

18 18 Hall A

19 19 Experimental Setup for 3 He (e,eπ - )x Beam –6 GeV electron, 15 μA Target –Optically pumped Rb spin-exchange 3 He target, 50 mg/cm 2, ~40% polarization, transversely polarized with tunable direction Electron detection –BigBite spectrometer, Solid angle = 60 msr, θ Lab = 30 0 Charged pion detection –HRS spectrometer, θ Lab = 16 0

20 Hall A polarized 3 He target Both longitudinal and transverse Luminosity=10 36 (1/s) High in-beam polarization Effective polarized neutron target Caltech, Duke/MIT, JLab, Kentucky, Temple, UVA/Princeton, W&M 6 completed experiments 4 approved

21 21 Transversely polarzied 3 He target Target polarization orientation can be rotated to increase the coverage in Ф S l

22 22 Kinematic acceptance Hall-A : x: 0.19 – 0.34, Q 2 : 1.8 – 2.7 GeV 2, W: 2.5 – 2.9 GeV, z: 0.37 – 0.56 HERMES: = 2.5 GeV 2

23 23 Disentangling Collins and Sivers Effects Collins angle: Ф C =Ф h l + Ф S l Sivers angle: Ф S =Ф h l - Ф S l Coverage in Ф S l is increased by rotating target polarization

24 24 Model Predictions for δq and A UT A UT for favored quark fragmentation (dashed) and favored + unfavored (solid) at Q 2 = 2.5 GeV 2 and integrated over z A UT is large, increasing with x A UT π+ (p): dominated by δu A UT π- (n): both δu and δd contribute Quark – diquark model (solid) and pQCD-based model (dashed) B. –Q. Ma, I. Schmidt and J. –J. Yang, PRD 65, (2002)

25 25 Expected Statistical Sensitivities Comparison with HERMES projection

26 26 Expected Statistical Sensitivities JLab E Projection 3 He (e,e -) HERMES p (e,e )

27 27 Status and Schedule Polarized 3 He: need to add a set of vertical coils fast polarization flip is being tested BigBite spectrometer used in SRC experiment new detectors will be used for G E n experiment HSR is ready, excellent PID - part is approved and scheduled to run in fall of proposal is being developed K +/- got for free

28 Other transverse spin experiments Proton transversity g 2 /d 2 : twist-3 Target SSA: access GPD

29 29 From X. Jiang

30 g 2 : twist-3, q-g correlations experiments: transversely polarized target SLAC E155x, JLab Hall A g 2 leading twist related to g 1 by Wandzura-Wilczek relation g 2 - g 2 WW : a clean way to access twist-3 contribution (q-g correlations) h 1 term suppressed by quark mass

31 31 Jefferson Lab Hall A E Precision Measurement of g 2 n (x,Q 2 ): Search for Higher Twist Effects T. Averett, W. Korsch (spokespersons) K. Kramer (Ph.D. student) Improve g 2 n precision by an order of magnitude. Measure higher twist quark-gluon correlations. Accepted by PRL, K. Kramer et al., nucl-ex/

32 32 E results: g 2 n vs. Q 2 measured g 2 n consistently higher than g 2 ww : positive twist-3 higher twist effects significant below Q 2 =1 GeV 2 Models (color curves) predict small or negative twist-3

33 Second Moment: d 2 n E SLAC (high Q 2 ) E (low Q 2 ) Twist-3 matrix element ChPT (low Q 2 ) MAID model Lattice QCD (high Q 2 ) other models

34 GPD moment with target SSA with 2 effect JLab E05-015: Spokespersons: T. Averett, J.P. Chen, X. Jiang


36 Other SIDIS experiments Sea asymmetry Spin-flavor decomposition

37 37 A Hall-A proposal PR Semi-inclusive pion and kaon production using Bigbite and HRS spectrometers Projected sensitivity for

38 38 A Hall-C proposal PR Large acceptance BETA detector and the HMS spectrometer

39 39 Other planned experiments and outlook Approved SIDIS proposal in Hall B (H. Avakian) A new proposal with polarized 3 He (n) for spin-flavor decomposition. Other measurements under consideration. SIDIS with JLab 12 GeV upgrade: Transversity Transverse momentum dependent parton distributions Spin-flavor decomposition Sea asymmetry

40 40 Summary With high luminosity and moderate energy, factorization seems reasonable for JLab SIDIS. JLab experiment E will measure neutron SSA using transversely polarized 3 He target. Experimental preparation underway data taking in fall Other transverse spin experiments. Other SIDIS experiments at JLab and 12 GeV.

41 41

42 42 Collins Effect at 12 GeV Upgrade UT ~ Collins Study the Collins fragmentation for all 3 pions with a transversely polarized target and measure the transversity distribution function. JLAB12 cover the valence region. From H. Avakian

43 43 Kaon fragmentation functions KKP global fit: This implies: Connections between the parton distribution and fragmentation functions?

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