Accessing(Polarized(SeaFlavor(Asymmetry(( through...

Accessing Polarized Sea Flavor Asymmetry through Semi-‐Inclusive DIS at JLab-‐12GeV and EIC

Xiaodong Jiang, Los Alamos NaGonal Laboratory June 26th, 2014 @ EIC User MeeGng

•  SIDIS double-‐spin asymmetry Ah1N provides access to

•  Three independent methods of SIDIS spin-‐flavor decomposiGon •  NLO global fit. •  Leading-‐order “purity” method as in HERMES and COMPASS. •  Leading-‐order and NLO Christova-‐Leader method:

•  Example-‐I:JLab-‐12GeV, Hall A on polarized neutron (3He) target . •  Example-‐II: EIC

Polarized Sea Flavor Asymmetry 1

∆u =? 0,∆d =? 0,∆u−∆d =? 0

An Electron-‐Ion Collider is a machine of discovery: to discover new phenomena in the structure of nucleon and nucleus.

∆q,∆q

Flavor Asymmetry in Unpolarized Nucleon Sea

2

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

CTEQ5MMRSTGRV98

E866/NuSeaHermes

Systematic Uncertainty

x

d_ - u_

Polarized Sea Flavor Asymmetry

Nucleon sea polarized ? Flavor symmetric ? ∆u =? 0,∆d =? 0,∆u−∆d =? 0


! lepton -2 -1 0 1 2

-0.5

0

0.5

= 2% error2"/2"#DSSV08 L0

-W

+W

$ + ± e% ± W%+p p=510 GeVs < 50 GeV

e

T25 < E

LA

Rel lumisyst

3.4% beam pol scale uncertainty not shown

+W

-W

STAR Data CL=68%

DSSV08 RHICBOSDSSV08 CHE NLO

LSS10 CHE NLO

STAR CollaboraGon

DeviaGon from DSSV08 (sea pol. ~ 0 )


STRA W data introduced shibs to sea polarizaGon in NLO global fit (DSSV)


NNPDF arXiv:1406.5539

STRA W data introduced shibs to sea polarizaGon in NLO global fit (NNPDF)


StaGsGcal Model predicGon. Bourrely, Buccella, Soffer PLB 726, 296 (2013)

∆q

q

0.1~0.2

-‐0.1~-‐0.2

JLab-‐12 GeV Future EIC

StaGsGcal Model

BBS2008: a rather large sea polarizaGon 10~20%, strong flavor dependency.

Flavor Tagging Through SIDIS and Leading-‐Order “Purity” Method

8 Polarized Sea Flavor Asymmetry

Effects of non-‐vanishing sea polarizaKons will show up in SIDIS asymmetries.


!0.2

0

0.2

0.4

0.6

0.8 +!

1,pA

!0.2

0

0.2

0.4

0.6

0.8 K+1,p

A

!210 !110

!0.2

0

0.2

0.4

0.6

0.8 !!

1,pA

x!210 !110

K!1,pA

COMPASS

HERMES

!0.2

0

0.2

0.4 +!

1,dA K+1,dA

!!

1,dA K!1,dA

!0.2

0

0.2

0.4

!210 !110 x!210 !110


0

0.2

0.4

-0.2

0

-0.1

0

0.1

-0.1

0

0.1

HERMESSMCCOMPASSx

u(x)

x d(

x)x

u(x)

x d(

x)

x

x s(

x)

0

0.1

10 -2 10 -1 1

HERMES and COMPASS Leading-‐Order extracGons

Flavour Asymmetry


(leading-‐order “purity” method)

Caveat: assuming precision knowledge of quark to hadron fragmentaGon funcGons.

∆u−∆d

Strangeness polarizaGon


0

0.1

10!2

10!1

x

x!

s COMPASS

HERMES

Caveat: assuming precision knowledge of quark to hadron fragmentaGon funcGons.

DSSVDNSGRSV (val)

QSM

CTEQ x(d–-u

–)

DSSV 2=1DSSV 2/ 2=2%

x( u– - d

–)

x

-0.05

0

0.05

0.1

10 -3 10 -2 10 -1 1

13

Accessing Polarized Sea Flavor Asymmetry: NLO Global Fit (DSSV2008)


At NLO, also requires knowledge of gluon density and gluon to hadron fragmentaGon funcGons.


NLO QCD global fit needs inputs of: •  quark and gluon densiGes •  quark to hadron fragmentaGon funcGons •  gluon to hadron fragmentaGon funcGons

There’s an alternaGve method to avoid these complicaGons…


Without the complicaGon of FragmentaGon FuncGons.

SIDIS Using BigBite and SBS in Hall A

19

•  Spectrometer layout of SIDIS •  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

An JLab-‐12GeV Example: PR12-‐14-‐008


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


Projected Neutron Asymmetry Precision—1D for all hadrons

21

•  Projected asymmetry precisions (stat. only) in A1n

h vs x, integrated over z, pT, compared to prediction of “DSSV+” NLO global fit, arXiv:1108.3955


π+ π- π0

K+ K-

Projected Asymmetry Precision, 2D (x,z), E = 11 GeV


•  High precision measurements on a dense grid of (x, z). •  Consistent deviations from NLO QCD prediction ?

π+ π-

K+ K-

Physics Impacts


•  Impacts through NLO Global fit, DSSV2008. •  Impacts through leading-‐order purity method. •  Impacts through leading-‐order Christova-‐Leader method.

Impacts to sea quark polarizaGon: through NLO Global fit DSSV2008

25

Results of a DSSV study, impacts on error bands of sea quark polarization: •  Slight reduction on ubar •  Very significant reduction on dbar •  Noticeable reduction on s=sbar

Black: width of parabolas at a 2% increase of the DSSV χ2 (~ 1σ). Red: when including new data of this experiment.


Leading-‐Order “Purity” Method as in HERMES and COMPASS


SensiGvity to Strangeness PolarizaGon


0

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6x

x(s+

s)-

Statistical Model

COMPASSHERMES

This experimentE0=11 GeVE0=8.8 GeV

Leading-‐Order “Purity” Method

Leading-‐Order Christova-‐Leader Method:I



-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

CTEQ5MMRSTGRV98

E866/NuSeaHermes

Systematic Uncertainty

x

d_ - u_

Polarized sea flavor asymmetry: non-‐perturbaGve in nature, intrinsic property of nucleon.

Example-‐II: “Chinese EIC” e+p Case


A very preliminary study

Pe=3 GeV, pol.=0.85 Pp=12 GeV, pol.=0.60 “A diluGon free COMPASS experiment”. Integrated Luminosity=3.5 v-‐1 (200 days, @50% machine_up*exp_up ) Inclusive DIS A1p SIDIS Ah

1p h=π+, π-‐, K+, K-‐, charged-‐parGcle only. 50% PID*reconstrucGon_eff. SIDIS kinemaGcs cut: y cut: 0.05<y<0.9 Q2 cut: 1.0<Q2 W cut: 2.0<W in SIDIS 0.3<z<0.7


Leading-‐Order “Purity” Method Only shown ~1/5 of (x, Q2) bins. Integrated over z at each (x, Q2)

Very sensiGve to u-‐quark, ubar quark Less sensiGve to d-‐quark, dbar quark Need both proton and 3He beam

A very preliminary study

Need to feed the dense grid of “projected precision” to DSSV for an impact study.

Summary


∆u =? 0,∆d =? 0,∆u−∆d =? 0

An Electron-‐Ion Collider is a machine of discovery: to discover new phenomena in the structure of nucleon and nucleus.

We will make SIDIS measurements at JLab-‐12GeV Hall A for spin-‐flavor decomposiGon: •  High precision over a dense kinemaGc grid, constrain Δu, Δd •  Consistent deviaGon from DSSV2008 predicGon -‐> sea polarizaGon.

•  Check consistency between different extracGon methods. •  Set limits on the size of higher-‐twist/higher-‐order terms. A tesGng ground for EIC experiments.

Backup Slides


Gluon densiGes and gluon fragmentaGon funcGons vanish in π+ -‐ π-‐


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