the hall a neutron transversity experiment

The Hall A Neutron Transversity Experiment

Andrew Puckett, LANL (JLab Hall A/E06-010 Collaborations)

Presented to the Hall A Collaboration Meeting6/9/2011

Hall A Collaboration Meeting 2

Outline• Introduction: brief review of SIDIS formalism,

transverse SSA physics• Status of transverse SSAs and TMDs in SIDIS• Status of JLab/Hall A experiment E06-010:

neutron transversity• Final results and discussion of the data• Conclusions

6/9/2011


Semi-Inclusive Deep Inelastic Scattering• In addition to usual DIS observables, SIDIS reaction N(e,e’h)X provides access to:• quark flavor• quark transverse motion• quark transverse spin

• Extra degrees of freedom relative to inclusive DIS more numerous and complicated structure functions • TMD approach: beyond collinear factorization, 8 leading-twist TMDs

6/9/2011


SIDIS Kinematic Definitions• Incident (scattered) lepton four-momentum: l = (E,k), l’ = (E’,k’)• Scattered hadron four-momentum Ph = (Eh, ph)• Azimuthal angles defined according to Trento convention (right)

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Transverse Single-Spin Asymmetries

FNAL E704: PLB 264, 462 (1991)

Large left-right single-spin asymmetry (SSA) first observed in inclusive pion

production in pp collisions.

SSA in naive parton model approach ~αSmq/Q; could not be reconciled with this

observation

6/9/2011


Transverse SSAs in SIDIS

Transverse target spin-dependent cross section for SIDIS

• Collins effect—chiral-odd quark transversity DF; chiral-odd Collins FF• Sivers effect—access to quark OAM and QCD FSI mechanism• “Pretzelosity” or Mulders-Tangerman function—access to wavefunction components differing by 2 units of OAM

Different TMD contributions isolated via azimuthal modulations

6/9/2011


Physics of Transverse SSAs—Sivers Effect

6/9/2011

• Sivers function is a correlation between kT of unpolarized quarks and nucleon transverse spin;• Connected to quark OAM• Generates left-right asymmetry in the SIDIS cross section (polarization normal to hadron production plane):

• Naive T-odd: presence requires a phase; generated (in SIDIS) by QCD FSI (Brodsky, Hwang, Schmidt) • Based on gauge invariance, QCD predicts sign change of Sivers function between SIDIS and Drell-Yan production• Needs experimental verification!

YD

qTSIDIS

qT ff

11

• Crucial test for TMD factorization approach to SSAs


Physics of Transverse SSAs—Collins Effect

6/9/2011

• Transversity distribution expresses the correlation between quark and nucleon transverse polarization.• Accessible in SIDIS by coupling to spin-dependent Collins fragmentation function:

• For non-relativistic quarks, h1 = g1, difference between helicity and transversity is a signature of relativistic effects• First moment of h1 = tensor charge; calculable in lattice QCD

• Gluon transversity vanishes due to helicity conservation quark transversity is “valence-like”• Soffer bound:


Transversity and Collins FFs from SIDIS and e+e- Data

6/9/2011

• NPB 191, 98 (2009): Phenomenological global fit of quark transversity distributions and Collins FFs to latest HERMES proton + COMPASS deuteron SIDIS data and BELLE e+e- data• Data favor opposite sign u and d quark transversity, constraints from pre-2007 data are limited• Latest fit favors h1

d close to Soffer limit.

u and d quark transversity Favored/Unfavored Collins FFs


Sivers Functions from SIDIS Data

6/9/2011

• EPJ A, 39, 89 (2009)• Extraction and flavor separation of Sivers functions for all light-quark/antiquark flavors using phenomenological ansatz• u and d quark Sivers of opposite sign, similar magnitude • Large K+ Sivers moments appear to require a positive anti-s Sivers function• ubar, s, not presently distinguishable from zero• Negative dbar favored


E06-010 in Jefferson Lab Hall A

6/9/2011

InstitutionsCMU, Cal-State LA, Duke, Florida International, Hampton, UIUC, JLab, Kharkov, Kentucky, Kent State, Kyungpook National South Korea, LANL, Lanzhou Univ. China, Longwood Univ. Umass, Mississippi State, MIT, UNH, ODU, Rutgers, Syracuse, Temple, UVa, William & Mary, Univ. Sciences & Tech China, Inst. of Atomic Energy China, Seoul National South Korea, Glasgow, INFN Roma and Univ. Bari Italy, Univ. Blaise Pascal France, Univ. of Ljubljana Slovenia, Yerevan Physics Institute Armenia.

Collaboration members K. Allada, K. Aniol, J.R.M. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, P.C. Bradshaw, P. Bosted, A. Camsonne, M.

Canan, G.D. Cates, C. Chen, , J.-P. Chen (Co-SP), W. Chen, K. Chirapatpimol, E. Chudakov, , E. Cisbani(Co-SP), J. C. Cornejo, F. Cusanno, M. Dalton, W. Deconinck, C. de Jager, R. De Leo, X. Deng, A. Deur, H. Ding, C. Dutta, C. Dutta, D. Dutta, L. El Fassi, S. Frullani, H. Gao(Co-SP), F. Garibaldi, D. Gaskell, S. Gilad, R. Gilman, O. Glamazdin, S. Golge, L. Guo, D. Hamilton, O. Hansen, D.W. Higinbotham, T. Holmstrom, J. Huang, M. Huang, H. Ibrahim, M. Iodice, X. Jiang (Co-SP), G. Jin, M. Jones, J. Katich, A. Kelleher, A. Kolarkar, W. Korsch, J.J. LeRose, X. Li, Y. Li, R. Lindgren, N. Liyanage, E. Long, H.-J. Lu, D.J. Margaziotis, P. Markowitz, S. Marrone, D. McNulty, Z.-E. Meziani, R. Michaels, B. Moffit, C. Munoz Camacho, S. Nanda, A. Narayan, V. Nelyubin, B. Norum, Y. Oh, M. Osipenko, D. Parno, , J. C. Peng(Co-SP), S. K. Phillips, M. Posik, A. Puckett, X. Qian, Y. Qiang, A. Rakhman, R. Ransome, S. Riordan, A. Saha, B. Sawatzky,E. Schulte, A. Shahinyan, M. Shabestari, S. Sirca, S. Stepanyan, R. Subedi, V. Sulkosky, L.-G. Tang, A. Tobias, G.M. Urciuoli, I. Vilardi, K. Wang, Y. Wang, B. Wojtsekhowski, X. Yan, H. Yao, Y. Ye, Z. Ye, L. Yuan, X. Zhan, Y. Zhang, Y.-W. Zhang, B. Zhao, X. Zheng, L. Zhu, X. Zhu, X. Zong.

Ph.D. thesis students, Co-spokespersons


Experiment Setup

6/9/2011

Beam Polarimetry(Møller + Compton)

LuminosityMonitor

• 3He(e,e’π±)X in JLab Hall A• Transversely polarized 3He target through spin-exchange optical pumping of hybrid-alkali (Rb-K) mixture. • World record polarized 3He figure-of-merit: ~60% average polarization @ 12 μA avg. beam current• Electrons in BigBite spectrometer at 30°• Hadrons in High Resolution Spectrometer (HRS) at 16°


Polarized 3He Target

6/9/2011

~87% ~8% ~1.5%

Polarized 3He as effective polarized neutron target

Effective nucleon polarization approach:

Scopetta, PRD 75, 054005 (2007)

~10 atm 3He = ~1036 cm-2s-1 en luminosity

Final target chamber <P> = (55.4 ± 2.8)%


BigBite Spectrometer

6/9/2011

BigBite Spectrometer

• 1.2 Tesla dipole magnet in front of detector stack• Positioned to subtend ~64 msr solid angle• Large out-of-plane angle acceptance (~±240 mrad), essential to maximize ϕ coverage, separate Collins/Sivers effects• Three drift chambers for tracking• Shower+Preshower for electron PID• Scintillator for timing


Detector Hut

D1Q1 Q2 Q3

DetectorPackage

High Resolution Spectrometer

6/9/2011

• Gas Cherenkov+Lead-glass for e/π separation• Coincidence Vertex + TOF w/ Bigbite suppress random coinc.• Aerogel+RICH+TOF: π/K separation >10:1 K rejection factor


Kinematic and Azimuthal Coverage

6/9/2011

Q2, W, z, W’ vs. x

z, pT for different x bins, π±

Collins/Sivers angle coverage, x bins 1-4, different target spin states

z pTπ+

π-

Collins Sivers


ANALYSIS HIGHLIGHTS

6/9/2011


Analysis: Target Single-Spin AsymmetryTarget single-spin asymmetry from normalized yields, need to consider :beam charge, target density, DAQ life time, detector efficiency etc.

Automatic target spin flip once every 20 minutes.

2845 target spin “local pairs”

Beam Charge + vs Beam Charge -

Beam charges are well-balanced between the pairs

6/9/2011


SSA check: HRS single-arm 3He SSA(Witness channels on 3He, not corrected for target polarization and dilution)

False asymmetry < 0.1%

K. Allada Univ. of Kentucky2010.

6/9/2011


Results—3He Collins+Sivers Moments

6/9/2011

• 3He π± Collins/Sivers moments <5% asymmetry magnitude• Collins consistent with zero, except at highest x, >2.3σ below zero• π+ Sivers moments favor negative values• Systematics:• “Experimental” includes

contamination/dilution/acceptance/target density/yield drift/etc...

• “Fit” results from neglecting other allowed azimuthal modulations of the SIDIS cross section

E06-010 Results, 3HeDraft publication submitted to PRL!

PRELIMIN

ARY


Comparison with World Data

6/9/2011


Results—Neutron Collins/Sivers Moments

6/9/2011

• Neutron extracted from 3He using: • Nucleon effective polarization• Proton dilution from

measured cross-section ratio of 1H2/3He

• FSI: spin-independent(spin-dependent) estimated at <3.5 (dilution)% (<1% (asymmetry))

• Results compared to:• Global fit prediction• quark/diquark model (DQM):

PRD 83, 037502 (2011)• Light-cone quark model

(LCQM): PRD 79, 094012 (2009) and PRD 78, 034025 (2008)

PRELIMIN

ARY

E06-010 results, neutronDraft publication submitted to PRL!


Best Neutron Measurements at High x

6/9/2011


Paper posted on arxiv:1106.0363Submitted to PRL

6/9/2011


3He double-spin asymmetry ALT

• First observation of a non-zero ALT.

• First measurement on neutron(3He).• Relate to quark TMD g1T(x, kT).

• The real part of quark L=0✖L=1 interference, “twin-brother” of Sivers.

Ph.D. thesis of J. Huang (MIT 2011).

down-quark’s g1T(x) is rather small at low-x, negative at high-x.up-quark’s g1T(x) is not small, positive in sign.

ALT on proton should be noticeable.

Preliminary

6/9/2011


Status of Ongoing Efforts• Detailed results/kinematics tables, plots:

– https://hallaweb.jlab.org/experiment/transversity/E06010/• Long analysis note (in progress):

– http://www.jlab.org/~kalyan/longnote/• ALT paper drafted, under revision in core analysis group• Long paper drafting started• Inclusive (e,e’) and inclusive hadron (e,h) asymmetries • Kaon results

6/9/2011

https://hallaweb.jlab.org/experiment/transversity/E06010/

http://www.jlab.org/~kalyan/longnote/


Conclusions• Successful execution and data analysis of E06-

010, results submitted to PRL• Best measurement of neutron Collins/Sivers

moments in the valence quark region• Largely consistent with expectations from

HERMES/COMPASS data• Laid the foundation for high-precision neutron

TMD measurements in multi-dimensional kinematic coverage @ JLab 12 GeV.

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BACKUP SLIDES

6/9/2011


Nature of E06-010 Results, I

6/9/2011

Down quark dominates n(e,e’π+)X cross section

E06-010 n(e,e’π+)X Sivers result strongly

suggests d quark Sivers < 0, consistent with

expectation from HERMES+COMPASS

fit


Nature of E06-010 Results, II

6/9/2011

arXiv:0812.4366v1

• Updated transversity and Collins FF fit: arXiv:0812.4366v1 to include new data from HERMES/COMPASS• Soffer bound enforced in model/fitting; • Current fit favors a result bumping up against the Soffer bound for d-quark transversity.• Small Collins moments predicted for n(e,e’π±)X due mainly to Soffer bound• High-x neutron π+ Collins moment tantalizingly large; a violation? But more precision needed to conclude anything...

?


BigBite Performance: I

6/9/2011

BigBite Sieve Slit

Angle calibration using sieve slit:• Angular resolution: <10 mr

Vertex calibration using multi-foil Carbon target:

• Vertex resolution: ~7 mm


BigBite Performance, II

6/9/2011

Momentum calibration using 1H(e,e’p) at two beam energies:

Resolution dp/p ~1%

PID using preshower/shower: π- contamination <2%


• ∝ Worm-gear TMD, g1T D⊗ 1

– Dominated by L=0 (S) and L=1 (P) interference.• Consist with model in sign.

suggest a larger asymmetry.

Neutron Double-Spin Asymmetry ALT

Preliminary

6/9/2011


SIMC: E06-010 Monte Carlo

6/9/2011

Successful asymmetry extraction from simulated data

Test bias and efficiency of MLE method at E06-010 statistics


NSAC Milestone 2010-2015: HP13 “Test unique QCD predictions for relations between single-spin phenomena in p-p scattering and those observed in deep-inelastic scattering”.

Estimated statistical uncertainties of 3-year running at FNAL following E906

• A new 10 cm long vertically polarized NH3 target. PT=0.80.• Frequent target spin flip to reduce systematic uncertainties.

6/9/2011

Hall A Collaboration Meeting 366/9/2011

Layout of experiment• Electron arm (BigBite) at 30° • Hadron arm (SBS) at 14°• Upgraded high-luminosity 3He target, 60 cm long; target spin can be oriented in 8 transverse directions• 10X larger angular acceptance compared to 6 GeV transversity

• BigBite effective solid angle for 60 cm target = 45 msr; ~5/1 vertical/horizontal aspect ratio• SBS solid angle = 50 msr; 4/1 vertical/horizontal aspect ratio• “Super-Big” momentum bite for h arm: 2 GeV < ph < full beam energy


Impact of E06-010 Results on World Data

6/9/2011

E06-010 3He and COMPASS p/d E06-010 n vs COMPASS d-p• E06-010 Helium-3 results are comparable in precision and complementary in x coverage (high-x/valence region) compared to COMPASS p/d• E06-010 neutron results provide the best constraint on neutron Sivers moments in the valence region, and comparable to COMPASS for neutron Collins moments after correcting for kinematic suppression Dnn


Hadron arm: Super BigBite Spectrometer (SBS) • http://hallaweb.jlab.org/12GeV/SuperBigBite/• Warm dipole magnet 48D48, Bdl = 2 Tm; cut in yoke for passage of beam pipe, reach to very forward angles. (Lambertson magnet, familiar concept in accelerator physics).

Detectors for SIDIS• GEMs: high-rate capability, high-resolution tracking; momentum/angle/vertex/RICH, resolution• HCAL: Iron-scint hadronic calorimeter; trigger + timing + coordinate measurement+reduce search area for high-rate tracking• HERMES RICH: Hadron PID, full π/K/p separation 2 GeV<p<15 GeV

http://hallaweb.jlab.org/12GeV/SuperBigBite/


Electron arm: BigBite Spectrometer• Already used successfully in a large number of experiments, including E06-010 (transversity)

Detectors for SIDIS• Lead-glass preshower/shower for trigger and offline pion rejection; threshold = 1 GeV• GEM chambers (INFN) instead of MWDC: • Increase rate capability in high-luminosity environment• Improve resolution

• Gas Cherenkov: trigger and pion rejection [experience in hand, planned improvements]• Charge tagger: possible supplement to GC for neutral trigger suppression

Charge Tagger = GEM with pad readout


• History of FOM increases in JLab polarized 3He experiments (top right)• New design with convection-driven flow • Fast replacement of polarized gas • Tolerate higher beam currents—support

up to 60 μA, 60 cm long cell• Decouple location of target chamber and

pumping chamber; decouple magnetic field directions

• Concept already demonstrated in bench tests• Fast spin orientation: ~every 2 minutes• Metal target cell in vacuum: reduce non-3He material on beamline—reduce background rates

High Luminosity Polarized 3He Target

Schematic of target chamber in vacuum Bench test of convection flow


SOLID: Solenoid Detector for TMD Studies


Inclusive DIS and PDFs

• Deep-inelastic lepton-nucleon scattering N(e,e’)X (DIS) is the richest source of information on nucleon structure• Greatest triumph of pQCD; factorization, universality, scale evolution of PDFs

HERA F2p

arXiv:hep-ex/0211051v1

MSTW2008 NNLO PDFs: arXiv:0901.0002v3

6/9/2011

http://arxiv.org/abs/hep-ex/0211051v1

http://arxiv.org/abs/0901.0002v3


Polarized DIS and Helicity PDFs

PDG2010 compilation of g1 data DSSV NLO global fit: PRD 80, 034030 (2009)

6/9/2011


Physics of transverse target SSACollins Effect• Transversity distribution;

correlation of transverse quark/nucleon polarization.

• First moment = tensor charge; test of lattice QCD prediction

• Chiral-odd; access in SIDIS combined with chiral-odd Collins FF. Strongly suppressed in inclusive DIS

• Soffer bound:

Sivers Effect• Correlation between quark transverse

momentum and nucleon transverse spin

• “Naive T-odd”—presence requires interference between S-wave and P-wave light-cone WF components

• In SIDIS: QCD FSI between struck quark and target remnant generates required phase.

• In Drell-Yan: QCD ISI between active partons and spectator nucleons

• Fundamental QCD prediction (based on gauge invariance):

6/9/2011


Status of Experimental Data: Transverse Target SSAs in SIDIS

6/9/2011


HERMES: Sivers Effect in Proton SIDIS• Sivers moments in e± SIDIS on transversely polarized protons (HERMES Collaboration): • PRL 103, 152002 (2009)

• Key observations: • π+/K+ Sivers moments “large”

and positive• π-/K- ≈ 0

• Suggests strong flavor dependence; partial cancellation between u and d quark Sivers functions.• Increases with transverse momentum pT; “saturation” above 0.4 GeV.

6/9/2011


COMPASS: Sivers Effect in Deuteron SIDIS

6/9/2011

• COMPASS Collaboration: Sivers moments in muon SIDIS on transversely polarized deuterons: • PLB 673, 127 (2009)

• COMPASS deuteron Sivers data for all measured hadron species ~0; • Combined with HERMES proton data, suggest a cancellation between proton and neutron; u/d quarks


HERMES: Collins Effect in Proton SIDIS

6/9/2011

• Collins moments in e± SIDIS on transversely polarized protons:• PLB 693, 11 (2010)

• Positive asymmetries for π+ and K+

• Negative asymmetries for π-

• K- ~ 0• “Unfavored” Collins FF could be comparable to “favored” based on similar size of π+/π- asymmetries (consistent with BELLE e+e- annihilation data: PRL 96, 232002 (2006) )


COMPASS: Collins Effect in Deuteron SIDIS

6/9/2011

• Collins effect in muon SIDIS on transversely polarized deuterons: • PLB 673, 127 (2009)

• All asymmetries compatible with zero; as in Sivers case, suggesting a cancellation between p/n and u/d quarks


COMPASS Proton Data—PLB 692, 240 (2010)

6/9/2011

the hall a neutron transversity experiment

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