1 / 54

Semi-Inclusive DIS Experiments Using BigBite and Super BigBite Spectrometers in Hall A

Semi-Inclusive DIS Experiments Using BigBite and Super BigBite Spectrometers in Hall A. Andrew Puckett University of Connecticut and Jefferson Lab SBS Collaboration Meeting July 7, 2014. Outline. Introduction—Semi-Inclusive DIS, TMDs, flavor tagging

elle
Télécharger la présentation

Semi-Inclusive DIS Experiments Using BigBite and Super BigBite Spectrometers in Hall A

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Semi-Inclusive DIS Experiments Using BigBite and Super BigBite Spectrometers in Hall A Andrew Puckett University of Connecticut and Jefferson Lab SBS Collaboration Meeting July 7, 2014

  2. Outline • Introduction—Semi-Inclusive DIS, TMDs, flavor tagging • SIDIS studies using BigBite and Super BigBite in Hall A • Approved experiment E12-09-018 (neutron transversity): Collins/Sivers effects in SIDIS on transversely polarized 3He • New Hall A Collaboration Proposal to PAC42—SIDIS on longitudinally polarized 3He, high-statistics measurements of A1nhin n(e,e’h)X • Expected results and impact on nucleon spin-flavor decomposition • Summary and conclusions July 2014 SBS Collaboration Meeting

  3. Semi-Inclusive Deep Inelastic Scattering • Detecting leading (high-energy) hadrons in DIS, N(e,e’h)X reaction provides sensitivity to additional aspects of the nucleon’s partonic structure not accessible in inclusive DIS: • quark flavor • quark transverse motion • quark transverse spin • Goal of SIDIS studies is (spin-correlated) 3D imaging of nucleon’s quark structure in momentum space. • Transverse Momentum Dependent (TMD) PDF formalism: Bacchetta et al. JHEP 02 (2007) 093, Boer and Mulders, PRD 57, 5780 (1998), etc, etc... July 2014 SBS Collaboration Meeting

  4. SIDIS Kinematics—Notation and Definitions July 2014 SBS Collaboration Meeting

  5. General Expression for SIDIS Cross Section: Bacchetta et al. JHEP 02, 093 (2007) • SIDIS structure functions F depend on x, Q2, z, pT • U, L, T subscripts indicate unpolarized, longitudinally and transversely polarized beam, target, respectively • S = nucleon spin • λ = lepton helicity • Eight terms survive at leading twistlarge Q2 crucial for “clean” interpretation • Sivers • Collins • “Pretzelosity” July 2014 SBS Collaboration Meeting

  6. Quark-parton Model Interpretation of SIDIS: Transverse Momentum Dependent PDFs (TMDs) July 2014 SBS Collaboration Meeting

  7. SIDIS Structure Functions in Terms of TMDs • Only f1, g1, h1survive integration over quark kT • All eight leading-twist TMDs are accessible in SIDIS with polarized beams/targets via azimuthal angular dependence of the SIDIS cross section • Physical observables are convolutions over two (unobserved) transverse momenta: • Initial quark kT • Hadron pT relative to recoiling quark, generated during fragmentation July 2014 SBS Collaboration Meeting

  8. JLab 11/8.8 GeV DIS Kinematics W > 2 GeV • Optimal orientation of hadron arm is along virtual photon direction—q-direction varies linearly with x for fixed electron scattering angle • Need forward-angle hadron detection capability! • To reach high x in the DIS regime, need large scattering angles/high-Q2 July 2014 SBS Collaboration Meeting

  9. July 2014 SBS Collaboration Meeting

  10. SIDIS Using BigBite and SBS in Hall A SIDIS w/BB 30 deg, SBS 14 deg. • 60 cm polarized 3He • 10.5 atm • Ibeam ≥ 40 μA • Above: Schematic of SIDIS experiment(s) • Independent electron and hadron arms: • Large momentum bite • Moderate solid angle • High-rate capability • Excellent PID • h+/h- symmetric acceptance SIDIS w/BB 30 deg, SBS 10 deg. BigBite (SBS) as electron (hadron) arm July 2014 SBS Collaboration Meeting

  11. <Q2> of SBS+BB SIDIS: > HERMES, < COMPASS July 2014 SBS Collaboration Meeting

  12. SIDIS Kinematic Coverage • Distributions of SIDIS kinematic variables—normalized to 10 (5) days at each SBS angle setting for E = 11 (8.8) GeV • θSBS = 10 deg; θSBS = 14 deg July 2014 SBS Collaboration Meeting

  13. SIDIS Phase Space Coverage July 2014 SBS Collaboration Meeting

  14. Charged Hadron PID—SBS RICH Detector • Re-use HERMES dual-radiator RICH detector • Aerogel n=1.0304 • C4F10 gas n=1.00137 • NIM A 479, 511 (2002) • Above: RICH schematic • Top right: HERMES RICH implemented in SBS GEANT4 • Bottom right: actual and reconstructed θC from GEANT4 “True” Reconstructed July 2014 SBS Collaboration Meeting

  15. Expected PID performance (IRT algorithm) 5 GeV pion 5 GeV kaon • MC PID results include acceptance effects—showing RICH geometry is well-matched to SBS magnet/tracker acceptance July 2014 SBS Collaboration Meeting

  16. SBS+BB Resolution—Charged Hadrons • SBS+BB resolution more than adequate for SIDIS on 3He—kinematic bin migration/resolution dominated by Fermi-smearing. • Bin migration due to kinematic smearing becomes significant for ΔxBj < ~0.1 July 2014 SBS Collaboration Meeting

  17. Neutral pion detection—Acceptance comparison • π0 detected in HCAL via two high-energy hits separated by at least one pixel • Apertures of GEM/RICH limit useful area of HCAL for π0 detection • Pixel size 15 x 15 cm2 limits coord. resolution for EM showers to 15 cm/sqrt(12) = 4.3 cm • Estimated HCAL resolution for EM showers is dE/E ~ 14%/sqrt(E in GeV) July 2014 SBS Collaboration Meeting

  18. SBS+BB Resolution—Neutral Pions • π0 kinematic resolution dominated by HCAL coordinate/energy resolution—two-photon invariant mass resolution ~21 MeV • To-do—full MC study of accidental/combinatorial background for π0 reconstruction. July 2014 SBS Collaboration Meeting

  19. Unique Advantages of SBS+BB for SIDIS Physics • The combination of moderate solid angle, large momentum acceptance and high-rate capability at forward angles is ideal for high-luminosity experiments (e.g., polarized 3He), SIDIS at high Q2 • For polarized proton SIDIS at lower luminosity, competitiveness of SBS+BB less clear; large acceptance detectors have a bigger advantage • Independent electron and hadron arms—straight-line tracking in “field-free” regions behind dipole magnets • Simple, reliable reconstruction and data analysis • Change magnet polarity of e(h) arm without changing h(e) acceptance: • Most accurate possible measurement of pair-production background in BigBite (important background for 3He targets w/thick glass walls, especially at low x) • SBS polarity reversals to increase ϕh coverage and make h+/h- acceptances identical • Ability to measure K and π0 simultaneously in addition to charged pions • Excellent systematics control for charge-sum and difference asymmetries used to separate valence/sea quark polarizations • Complementarity with CLAS12/SOLID/Hall C experiments—precise, timely neutron data w/unique kinematic coverage; can run within first five years of 12 GeV July 2014 SBS Collaboration Meeting

  20. Transverse target spin effects 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 • “Transversal helicity” g1T—real part of S wave-P wave interference (Sivers = imaginary part) (requires polarized beam) • “Pretzelosity” or Mulders-Tangerman function—interference of wavefunction components differing by 2 units of OAM July 2014 SBS Collaboration Meeting

  21. The Sivers Effect: a Probe of Quark OAM • Proton spin is along +y axis (up) • Proton momentum into screen • Regions of higher/lower quark density in transverse momentum space x = 0.2 A. Prokudin • Sivers effect: a left-right asymmetry in the transverse momentum distribution of unpolarized quarks in a transversely polarized nucleon P-25 Seminar, LANL

  22. JLab Experiment E12-09-018 • Primary physics goal: measure transverse target SSA in 3He(e, e’h)X in SIDIS kinematics in the valence region • Extract neutron SSAs from Helium-3 using effective polarization approximation—relatively small theoretical uncertainty • Wide, multi-dimensional kinematic coverage • Detect π±/0 and K± simultaneously in identical acceptance/kinematics (for charged hadrons) • First precision SSA data in a multi-dimensional phase space • Main experiment parameters: • Electron-polarized neutron luminosity: • Helium-3 target polarization: 60% • Electron beam polarization: 80-85% • Approved by JLab PAC38 for 64 beam-days, including: • 40 beam-days production at Ebeam = 11 GeV • 20 beam-days production at Ebeam = 8.8 GeV • 4 beam-days for calibrations, configuration changes E12-09-018, E=11 GeV E12-09-018, E=8.8 GeV E06-010, E=5.9 GeV July 2014 SBS Collaboration Meeting

  23. E12-09-018: Vast Improvement over Current Knowledge 1D binned neutron precision ~0.2% π± , K± Sivers compared to HERMES, COMPASS, theory fit FOM: Improvement on existing data by 2+ orders of magnitude • E12-09-018 will achieve statistical FOM for the neutron ~100X better than HERMES proton data and ~1000X better than E06-010 neutron data. • Kaon and neutral pion data will aid flavor decomposition, and understanding of reaction-mechanism effects. • Provide precise data in the unexplored region x > 0.3  valence-dominated July 2014 SBS Collaboration Meeting

  24. E12-09-018: First Precision Multi-Dimensional Analysis Uncertainty in this x, z bin ~ 0.6% Large neutron π+ asymmetry expectation at high z, large uncertainty • 2D Extraction: Sivers AUT in n(e,e’π+)X, 6 x bins 0.1<x<0.7, 5 z bins 0.2<z<0.7 • Curves are theory predictions (Anselmino et al.) with central value and error band July 2014 SBS Collaboration Meeting

  25. E12-09-018: Fully Differential Analysis Increasing z  • 6 (0.1 < x < 0.7) × 5 (0.2 < z < 0.7) × 6 (0 < pT (GeV) < 1.2) 3D binning • Q2 dependence with E = 11 and 8.8 GeV data gives fully-differential analysis • Typically 120 bins with good stats per beam energy • Statistical precision: • 83% of 3D bins have separated Collins/Sivers neutron asymmetry error of less than 5% (absolute) • Average stat. err ~4% • Most probable stat. err ~1.5%  Increasing pT Sivers AUT, n(e,e’π+)X vs. x, 40 days @ 11 GeV July 2014 SBS Collaboration Meeting

  26. New Proposal to PAC42—PR12-14-008 Measurements of Semi-Inclusive DIS Double-Spin Asymmetries on a Longitudinally Polarized 3He Target A Hall A Collaboration Proposal July 2014 SBS Collaboration Meeting

  27. PR12-14-008 Collaboration—Author list as of 6-1-2014 July 2014 SBS Collaboration Meeting

  28. Proton SpinCrisis/Puzzle • 1989: Fraction of proton spin carried by quarks is “small”—“crisis” for the parton model • Modern (DSSV2008) value of ΔΣ ≈ 0.24-0.37, depending on (controversial) behavior of strange sea polarization Δs • Remaining ~70% of nucleon spin distributed among gluon spin and orbital motion of quarks/gluons; poorly known but much recent progress both theoretically and experimentally “Crisis”: EMC collaboration, NPB 328, 1 (1989) July 2014 SBS Collaboration Meeting

  29. Polarized DIS and Nucleon Spin Structure PDG2010 compilation of g1 data DSSV NLO global fit: PRD 80, 034030 (2009) July 2014 SBS Collaboration Meeting

  30. July 2014 SBS Collaboration Meeting

  31. PR12-14-008: Projected Precision vs x for all hadrons • Projected asymmetry precisions (stat. only) in A1nhvs x, integrated over z, pT, compared to prediction of “DSSV+” NLO global fit: http://arxiv.org/abs/1108.3955 • Fit includes COMPASS 2010 p and d data: http://arxiv.org/abs/1007.4061 • <Q2> between HERMES and COMPASS • More details, numerical tables available at: https://userweb.jlab.org/~puckett/PAC42_deltad/projections/ July 2014 SBS Collaboration Meeting

  32. PR12-14-008: Projected Precision vs (x,z), E = 11 GeV • Left-right, top-bottom: π+, π-, π0, K+, K-. • Curves: “DSSV+”: http://arxiv.org/abs/1108.3955 • More details including numerical tables at: https://userweb.jlab.org/~puckett/PAC42_deltad/projections/ • Relatively weak z dependence of DSSV+ curves is a NLO QCD effect. • Strong hadron dependence of A1nh clear indication of flavor sensitivity of SIDIS July 2014 SBS Collaboration Meeting

  33. Impacts on Nucleon Spin-Flavor Decomposition • Left: Projected precision of five-flavor Δq/q extraction using LO “purity” method • Excellent precision/sensitivity to d and dbar, as expected. • Below: existing data, from DSSV2008 analysis: http://journals.aps.org/prd/abstract/10.1103/PhysRevD.80.034030 July 2014 SBS Collaboration Meeting

  34. Impacts on Spin-Flavor decomposition, II • Left: valence d polarization from Helium-3 charge-difference asymmetries using LO Christova-Leader method. • Below: polarized sea asymmetry assuming proton data of comparable precision to this proposal July 2014 SBS Collaboration Meeting

  35. Impact on Spin-Flavor Decomposition, III Preliminary results of DSSV impact study indicate dramatic impact of PR12-14-008 to dbar polarization (and very significant impacts to ubar, sbar) Flavor-separated SIDIS data important cross-check to RHIC W asymmetry data July 2014 SBS Collaboration Meeting

  36. SBS+BB SIDIS: Challenges/Status/Future Plans • “Dependencies”: • High-luminosity polarized 3He target w/flexible spin orientation (transversity) • Design shielding of SBS stray field • RICH detector: • Require TDC readout to reduce effective occupancy • Gas handling system in Hall A: availability of C4F10 or its equivalent (e.g., C4F8O)? • GEM occupancies and tracking: • SIDIS luminosity ~= GEP luminosity/40, but: • No exclusivity constraint on track search area • HCAL coordinate info can help • Need realistic MC • Background rates: • RICH—new estimates with fully detailed MC for approved and proposed SIDIS expt’s. • GEMs—define BB+SBS tracker geometry for SIDIS—demonstrate tracking feasibility for SIDIS • Beamline backgrounds  shielding design • 3He target in vacuum? • Trigger & DAQ: • Desired trigger thresholds for SIDIS: • BigBite: Electron p > 1 GeV • SBS: Hadron p > 2 GeV • Online trigger rate for SBS 14 deg. SIDIS configuration estimated at ~18 kHz in PR12-09-018 @PAC38 (dominated by accidentals) • ECAL-only trigger for BB assumed—includes ~90% photon-induced triggers • Need estimate for 10 deg. setting—may require higher threshold, higher minimum z (z >? 0.3) SBS SIDIS experiments (approved and proposed), are very challenging—SIDIS requirements need more attention/consideration in SBS design efforts, especially if PAC42 proposal approved! July 2014 SBS Collaboration Meeting

  37. Summary and Conclusions • The BigBite-SBS spectrometer pair in Hall A is ideally suited for high-luminosity polarized (and unpolarized) SIDIS experiments: • BigBite as electron arm as in several other 12 GeV expt’s. • SBS as hadron arm, equipped with existing RICH for high-performance PID • Experiment E12-09-018 (transversity) already approved for 64 beam-days, A- rating by PAC38 • New proposal PR12-14-008 (A1nh SIDIS) submitted to PAC42 for 33 beam-days, high-impact data for nucleon spin-flavor decomposition, relevant to future EIC program • SBS+BB SIDIS, with unique kinematic coverage and excellent systematics control, is complementary to other approved polarized SIDIS experiments such as CLAS12, SOLID, etc. • Impact studies of proposed measurements to NLO global QCD analysis are underway by Dr. R. Sassot of DSSV group. July 2014 SBS Collaboration Meeting

  38. Acknowledgements • Thanks to all who contributed to successful development/submission of new proposal • PR12-14-008 Spokespeople: • X. Jiang (contact), N. Liyanage • Hall A Collaborators/reviewers • SBS Collaborators • R. Sassot for grid of DSSV+ predictions and forthcoming impact studies. • S. Riordan for development of GEANT4 framework for SBS/BB MC simulations July 2014 SBS Collaboration Meeting

  39. Backup Slides July 2014 SBS Collaboration Meeting

  40. Major Systematic Uncertainties • See proposal for additional details: https://userweb.jlab.org/~puckett/PAC42_deltad/submitted_Deltaq.pdf Identical phase space for π+, π-leads to excellent systematic control of ratio r: July 2014 SBS Collaboration Meeting

  41. Comparison With Other Approved Experiments • Naive FOM comparison from basic experiment parameters • Generally: High-luminosity 3He in Hall A roughly 10-100X higher FOM for neutron than CLAS12 ND3 (kinematics-dependent) • At same kinematics, SBS+BB and SOLID FOM are of the same order-of-magnitude • SBS+BB higher luminosity partially offsets SOLID advantage in solid-angle July 2014 SBS Collaboration Meeting

  42. SBS+BB vs. SOLID: Complementarity of kinematic coverages • Left: Q2-x of SBS+BB vs. SOLID: SBS+BB reaches higher Q2 at similar x due to larger electron scattering angles. • Right: theta-vs.-phi coverage between SBS+BB and SOLID July 2014 SBS Collaboration Meeting

  43. Detailed FOM comparison—SBS+BB vs. SOLID July 2014 SBS Collaboration Meeting

  44. Experiment design considerations • Azimuthal coverage: full coverage of Sivers and Collins angles • Charged and neutral pionsand kaonsFlavor decomposition of PDF and FF • As large as possible Q2: DIS regime, factorization • Low-to-moderate pT: ΛQCD ~< pT << Q  Applicability of TMD formalism • Wide, independent coverage of xBj,z = p/n: factorization • Reach high x ~ 0.5-0.7, where observable asymmetries are expected to be large • Challenges: • A high performance polarized target • Low event rates at high Q2 and high xBj—high luminosity. • High-performance particle ID—separate different hadron species • Proton and neutron targets—flavor decomposition • Non-SIDIS backgrounds: • Radiative tails of exclusive and resonant electroproduction • Charge-symmetric (e+/e- pair-production) background Below: Zhongbo Kang seminar, LANL, 4/2011 July 2014 SBS Collaboration Meeting

  45. Electron Arm—BigBite Spectrometer • BigBite@ 6 GeV(E06-010 transversityexpt): • Three MWDCs for tracking (18 wire planes) • Pre-shower/shower calorimeter for trigger and PID • Scintillator hodoscope for timing • Dipole magnet: • BigBite @ 12 GeV: • Detector upgrades including: • GEM chambers for high-rate, high-resolution tracking (resolve higher electron momenta at same field integral) • Gas Cherenkov for higher-fidelity e/π separation • New detector support frame • BigBite parameters in E12-09-018: • Central angle = 30 deg. • Target to magnet yoke distance = 1.5 m July 2014 SBS Collaboration Meeting

  46. Hadron Arm—Super BigBite Spectrometer • SBS main parameters for E12-09-018: • Central angle = 14 deg. • Target to magnet yoke distance ~ 2.5 m • Solid angle ~40 msr • Momentum acceptance: p > 1 GeV • More info: http://hallaweb.jlab.org/12GeV/SuperBigBite • Super BigBite Spectrometer • Originally designed for nucleon elastic form factor measurements at large Q2. • 48D48 magnet: acquired from BNL by JLab, Bdl ~ 2 Tm. • Flexible, modular design w/ basic detector package consisting of: • GEMs • HCAL • Suitable for SIDIS with modest addition: • Re-use RICH detector from HERMES for hadron PID • HERMES RICH performance characteristics • π/K/p separation from 2-15 GeV using dual-radiator (aerogel + heavy gas) design • RICH details: NIM A 479 (2002) 511 July 2014 SBS Collaboration Meeting

  47. High-luminosity polarized 3He target • Basic Target Parameters in E12-09-018 • Polarization: 60-65% based on alkali-hybrid spin-exchange optical pumping technology • Beam current: 40 μA • Target cell length along beam-line: 60 cm • Electron-polarized neutron luminosity: • Luminosity * Pol.2 capability upgraded (relative to previous targets) by using convection-driven circulation of gas between “pumping chamber” and “target chamber” (already demonstrated in bench tests) and metal end-windows to prevent cell rupture (under development) • Spin orientation in “any” direction; holding field ~25 G • Fast spin rotation: Change spin orientation every ~120 s. Conceptual design of SIDIS target w/metal end windows July 2014 SBS Collaboration Meeting

  48. Experiment status, future plans, conclusion • Experiment E12-09-018 represents an exciting near-term opportunity to elucidate neutron transverse spin structure. • Super BigBite Spectrometer (SBS) recently funded by DOE, construction underway, with contributions from INFN (GEM), UVA (GEM), CMU (HCAL), JLab (Magnet, infrastructure, program management, etc.) and others. Exciting program of high-impact approved experiments: • Nucleon elastic Form Factors at large Q2—GMn, GEn, GEp • Neutron transversity in SIDIS on Helium-3 • Custody of half of HERMES RICH detector (and all aerogel) transferred to JLab, currently in controlled storage at UVA, plan to start refurbishment at UConn soon. • Many exciting physics opportunities beyond initial approved program (if beam time in Hall A is available) July 2014 SBS Collaboration Meeting

  49. Acknowledgements • E12-09-018 co-spokespeople: • Gordon Cates (UVA), EvaristoCisbani (INFN), Gregg Franklin (CMU), BodganWojtsekhowski (JLab) • E12-09-018 collaboration • SBS collaboration • A. Prokudin (for phenomenological model fit results and “theoretical” uncertainty projections) • US DOE July 2014 SBS Collaboration Meeting

  50. Electron-Nucleon Scattering: Kinematics Incident electron four-momentum Scattered electron four-momentum Initial nucleon four-momentum Squared Momentum Transfer Energy Transfer (nucleon rest frame) Bjorken “x” variable Fractional electron energy loss (nucleon rest frame) Invariant mass of virtual-photon + initial nucleon system July 2014 SBS Collaboration Meeting

More Related