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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 2002-2004 data: ~ factor of 12 in statistics hep-ex/0503002 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-ph0404183)

15 Planned neutron transversity experiment at JLab

16 16 JLab Hall-A E03-004 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, 034010 (2002)

25 25 Expected Statistical Sensitivities Comparison with HERMES projection

26 26 Expected Statistical Sensitivities JLab E03-004 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 2007 + 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 E97-103 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/0506005

32 32 E97-103 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 E99-117+SLAC (high Q 2 ) E94-010 (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

35

36 Other SIDIS experiments Sea asymmetry Spin-flavor decomposition

37 37 A Hall-A proposal PR-04-114 Semi-inclusive pion and kaon production using Bigbite and HRS spectrometers Projected sensitivity for

38 38 A Hall-C proposal PR-04-113 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 E03-004 will measure neutron SSA using transversely polarized 3 He target. Experimental preparation underway data taking in fall 2007. 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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