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 AAndrew Puckett

University of Connecticut and Jefferson LabSBS Collaboration Meeting

July 7, 2014

July 2014 SBS Collaboration Meeting 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 A1n

h in n(e,e’h)X• Expected results and impact on nucleon spin-flavor decomposition

• Summary and conclusions

7/7/2014


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...

7/7/2014


SIDIS Kinematics—Notation and Definitions

7/7/2014


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 twistlarge Q2 crucial for “clean” interpretation

• Sivers• Collins• “Pretzelosity”

7/7/2014


Quark-parton Model Interpretation of SIDIS: Transverse Momentum Dependent PDFs (TMDs)

7/7/2014

Quark polarization

Unpolarized(U)

Longitudinally Polarized (L)

Transversely Polarized (T)

Nucleon Polarization

U

L

T


SIDIS Structure Functions in Terms of TMDs• Only f1, g1, h1 survive 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

7/7/2014


JLab 11/8.8 GeV DIS Kinematics

7/7/2014

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 97/7/2014


SIDIS Using BigBite and SBS in Hall A

7/7/2014

• 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 14 deg.

SIDIS w/BB 30 deg, SBS 10 deg.

• 60 cm polarized 3He• 10.5 atm• Ibeam ≥ 40 μA

BigBite (SBS) as electron (hadron) arm


<Q2> of SBS+BB SIDIS: > HERMES, < COMPASS

7/7/2014


SIDIS Kinematic Coverage

7/7/2014

• 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


SIDIS Phase Space Coverage

7/7/2014


Charged Hadron PID—SBS RICH Detector

7/7/2014

• 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

http://www.sciencedirect.com/science/article/pii/S0168900201009329


Expected PID performance (IRT algorithm)

7/7/2014

5 GeV pion 5 GeV kaon

• MC PID results include acceptance effects—showing RICH geometry is well-matched to SBS magnet/tracker acceptance


SBS+BB Resolution—Charged Hadrons

7/7/2014

• 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


Neutral pion detection—Acceptance comparison

7/7/2014

• 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)


SBS+BB Resolution—Neutral Pions

7/7/2014

• 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.


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

7/7/2014


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

7/7/2014

P-25 Seminar, LANL 21

The Sivers Effect: a Probe of Quark OAM

10/24/2011

x = 0.2

A. Prokudin• Sivers effect: a left-right asymmetry in the transverse momentum distribution of unpolarized quarks in a transversely polarized nucleon

• Proton spin is along +y axis (up)• Proton momentum into screen• Regions of higher/lower quark density in transverse momentum space


JLab Experiment E12-09-018

7/7/2014

• 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


E12-09-018: Vast Improvement over Current Knowledge

7/7/2014

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


E12-09-018: First Precision Multi-Dimensional Analysis

7/7/2014

• 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

Uncertainty in this x, z bin ~ 0.6%

Large neutron π+ asymmetry expectation at high z, large

uncertainty


E12-09-018: Fully Differential Analysis

7/7/2014

Increasing z

In

crea

sing

pT

Sivers AUT, n(e,e’π+)X vs. x, 40 days @ 11 GeV

• 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%


New Proposal to PAC42—PR12-14-008

7/7/2014

Measurements of Semi-Inclusive DIS Double-Spin Asymmetrieson a Longitudinally Polarized 3He Target

A Hall A Collaboration Proposal


PR12-14-008 Collaboration—Author list as of 6-1-2014

7/7/2014


Proton Spin Crisis/Puzzle

“Crisis”: EMC collaboration, NPB 328, 1 (1989)

• 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

7/7/2014


Polarized DIS and Nucleon Spin Structure

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

7/7/2014

July 2014 SBS Collaboration Meeting 307/7/2014


PR12-14-008: Projected Precision vs x for all hadrons

7/7/2014

• Projected asymmetry precisions (stat. only) in A1n

h vs 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/

http://arxiv.org/abs/1108.3955




https://userweb.jlab.org/~puckett/PAC42_deltad/projections/





PR12-14-008: Projected Precision vs (x,z), E = 11 GeV

7/7/2014

• 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








Impacts on Nucleon Spin-Flavor Decomposition

7/7/2014

• 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

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.80.034030




Impacts on Spin-Flavor decomposition, II

7/7/2014

• 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


Impact on Spin-Flavor Decomposition, III

7/7/2014

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


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)

7/7/2014

SBS SIDIS experiments (approved and proposed), are very challenging—SIDIS

requirements need more attention/consideration in SBS design efforts, especially if PAC42 proposal

approved!


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 (A1n

h 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.

7/7/2014


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

7/7/2014


Backup Slides

7/7/2014


Major Systematic Uncertainties

7/7/2014

• 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:

https://userweb.jlab.org/~puckett/PAC42_deltad/submitted_Deltaq.pdf

https://userweb.jlab.org/~puckett/PAC42_deltad/submitted_Deltaq.pdf


Comparison With Other Approved Experiments

7/7/2014

• 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


SBS+BB vs. SOLID: Complementarity of kinematic coverages

7/7/2014

• 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


Detailed FOM comparison—SBS+BB vs. SOLID

7/7/2014


Experiment design considerations

7/7/2014

Azimuthal coverage: full coverage of Sivers and Collins angles Charged and neutral pions and kaonsFlavor 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


Electron Arm—BigBite Spectrometer

7/7/2014

BigBite @ 6 GeV (E06-010 transversity expt):• 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


Hadron Arm—Super BigBite Spectrometer

7/7/2014

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

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

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

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

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


High-luminosity polarized 3He target

7/7/2014

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


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)7/7/2014


Acknowledgements

• E12-09-018 co-spokespeople:• Gordon Cates (UVA), Evaristo Cisbani (INFN), Gregg

Franklin (CMU), Bodgan Wojtsekhowski (JLab)• E12-09-018 collaboration• SBS collaboration• A. Prokudin (for phenomenological model fit

results and “theoretical” uncertainty projections)• US DOE

7/7/2014


Electron-Nucleon Scattering: Kinematics

7/7/2014

Incident electron four-momentumScattered 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


Kinematic coverage from simulation

7/7/2014

BB+SBS solid angle coverage

Direction of q vs Bjorken x @ 11 GeV

Above: azimuthal coverage vs pT, Below: Kinematic coverage

Transversity 2014 52

Accessible phase space in fixed-target at 11 GeV

Above: phase space with SIDIS cuts (before considering any detector acceptances), E=11 GeV

6/12/2014


Transverse spin dynamics in eqeq

7/7/2014

• Magnitude of quark normal and in-plane transverse polarization components is reduced by a factor of • Dnn = (1-y)/(1-y+y2/2), where y = (1 - cosθCM)/2 is invariant (y=(ν/E)LAB).

• Direction of normal polarization is unchanged• In-plane transverse polarization component in the cms rotates with quark momentum vector—corresponds

to a spin flip in target rest frame (P, q collinear)• Simplified view—ang. mom. conservation requires spin flip for quark to absorb transverse virtual

photon• DNN, an inherent feature of the hard partonic subprocess, suppresses the observable SSA corresponding

to Collins effect, esp. at large y!


Where do the azimuthal dependences come from?• Sivers effect is due to the correlation between unpolarized quark kT and nucleon transverse polarization:

• Collins effect is due to the left-right asymmetry in the fragmentation of a transversely polarized quark.• The observable asymmetry results from the convolution of the transversity distribution and the Collins fragmentation function.

• The modified azimuthal dependence of the Collins SSA relative to Sivers is due to a spin-flip of the in-plane component of the quark’s transverse polarization component by the virtual photon (ang. mom. conservation)

7/7/2014

semi-inclusive dis experiments using bigbite and super bigbite spectrometers in hall a

Documents

sbs collaboration meeting

sidis kinematicsnotation

collaboration proposal

sidis structure functions

polarized beamstargets

polarized 3he10

super bigbite spectrometers

hall a772014july