December 17, 2004 JLab Hall A Upgrade 1 Semi-Inclusive DIS --opportunities at JLab upgrade Feng Yuan RBRC, Brookhaven National Laboratory.

December 17, 2004 JLab Hall A Upgrade 1

Semi-Inclusive Semi-Inclusive DISDIS

--opportunities at JLab --opportunities at JLab upgradeupgradeFeng Yuan Feng Yuan

RBRC, Brookhaven National RBRC, Brookhaven National LaboratoryLaboratory

December 17, 2004 2JLab Hall A Upgrade

OutlineOutline IntroductionIntroduction Low PLow P?? SIDIS (TMD) SIDIS (TMD)

High PHigh P?? SIDIS (Quark-gluon SIDIS (Quark-gluon correlations)correlations)

Integrated SIDIS (Flavor Integrated SIDIS (Flavor decomposition)decomposition)

SummarySummary


Inclusive and Inclusive and Semi-inclusive DISSemi-inclusive DIS

Inclusive DIS:Partonic Distribution depending on the longitudinal momentum fraction

Semi-inclusive DIS:Probe additional information includingthe transverse distribution


Different Different PP?? Region Region

Integrate out Integrate out PP??

-- normal factorization, similar to -- normal factorization, similar to inclusive DISinclusive DIS

Large Large PP? ? ((ÀÀQCDQCD))

-- hard gluon radiation, can be calculated -- hard gluon radiation, can be calculated from perturbative QCD, factorization from perturbative QCD, factorization similar to inclusive DISsimilar to inclusive DIS

Low Low PP? ? ((»»QCDQCD))

-- nonperturbative information: new -- nonperturbative information: new factorization formulafactorization formula

? ! 12GeV

12GeV

12GeV


Semi-Inclusive DIS at Semi-Inclusive DIS at Low PLow P??

Transverse Momentum Dependent Transverse Momentum Dependent (TMD) Parton Distributions(TMD) Parton Distributions

Novel Single Spin AsymmetriesNovel Single Spin Asymmetries


TMD Parton TMD Parton DistributionsDistributions

The gauge invariant definitionThe gauge invariant definition

Belitsky, Ji, Yuan (03)


Polarized TMD Quark Polarized TMD Quark DistributionsDistributions

Quark

Nucleon

Unpol.

Long.

Trans.

Unpol. Long. Trans.

q(x, kq(x, k┴┴)) qqTT(x, k(x, k┴┴))

ΔqΔqLL(x, k(x, k┴┴)) ΔqΔqTT(x, k(x, k┴┴))

δq(x, kδq(x, k┴┴)) δqδqLL(x, k(x, k┴┴)) δqδqTT(x, k(x, k┴┴) ) δqδqTT'(x, k(x, k┴┴))

Boer, Mulders, Tangerman (96&98)


The Physics We can learn The Physics We can learn from TMDfrom TMD

Internal structure, transverse momentum dis.Internal structure, transverse momentum dis. Quark Orbital Angular MomentumQuark Orbital Angular Momentum

e.g, Siver’s function ~ the wave function e.g, Siver’s function ~ the wave function amplitude with orbital angular momentum!amplitude with orbital angular momentum! Vanishes if quarks only in s-state!Vanishes if quarks only in s-state!

Friends: Friends: Pauli Form Factor FPauli Form Factor F22(t)(t) Spin-dependent structure function gSpin-dependent structure function g22(x)(x) Generalized Parton Distribution E(x, Generalized Parton Distribution E(x, ξξ, t), t)


Connection between TMD Connection between TMD and GPDand GPD

Wigner distributionsWigner distributions

After integrating over After integrating over rr, one , one gets TMDgets TMD

After integrating over After integrating over kk, one , one gets Fourier transform of GPDsgets Fourier transform of GPDs

Ji: PRL91,062001(2003)


SIDIS Cross SectionSIDIS Cross Section At leading power of 1/Q

The structure functions depend on Q2, xB, z, Ph?


Low PLow P?? SIDIS SIDIS FactorizationFactorization

Ji, Ma, Yuan, hep-ph/0404183,hep-ph/0405085


SIDIS: at Large PSIDIS: at Large P??

Large Large PP?? SIDIS can be calculated from SIDIS can be calculated from perturbative QCDperturbative QCD

Polarized scattering will provide information Polarized scattering will provide information on the quark-gluon correlations in the on the quark-gluon correlations in the nucleonnucleon

Single Spin Asymmetry at large PSingle Spin Asymmetry at large P?? is not is not suppressed by suppressed by 1/Q1/Q, but by , but by 1/P1/P??

With enough luminosities, we could measure With enough luminosities, we could measure these asymmetries at large these asymmetries at large PP?? at JLab at JLab 12GeV12GeV??


SSA at Large PSSA at Large P??

Qiu-Sterman mechanismQiu-Sterman mechanism

It is suppressed by It is suppressed by 1/P1/P??

Efremov & Teryaev: 1982 & 1984Qiu & Sterman: 1991 & 1999

Quark-gluon correlations


Transition from Transition from Perturbative region to Perturbative region to

Nonperturbative region?Nonperturbative region? Compare different region of PCompare different region of P??

Nonperturbative TMD Perturbative region


SIDIS: Integrated over PSIDIS: Integrated over P??

The factorization formulas are much The factorization formulas are much simplersimpler

Flavor decomposition for (polarized) Flavor decomposition for (polarized) PDFPDFFrankfurt et al 89; Melnitchouk et al 98, HERMES, EMC…Frankfurt et al 89; Melnitchouk et al 98, HERMES, EMC…

NLO: de Florian et al 96-98; Leader et al 01; Kretzer 04NLO: de Florian et al 96-98; Leader et al 01; Kretzer 04

Altarelli et al 79 (NLO)Altarelli et al 79 (NLO)


Flavor Decomposition for Flavor Decomposition for PDFPDF

(Leading Order)(Leading Order) In the valence region (large x),In the valence region (large x),

Isospin relation,Isospin relation,

DDuu++=D=Ddd

--, favored, favored; ; DDuu--=D=Ddd

++, , unfavoredunfavored; ;

DDuu--<< << DDuu

++


“favored”

“unfavored”

Well described by leading particle ansatz

Stefan Kretzer


Continue,Continue,

Similarly, from the polarized Similarly, from the polarized scattering,scattering,

d/u at large x!!


SummarySummary

Semi-inclusive DIS at JLab upgrade Semi-inclusive DIS at JLab upgrade provides various opportunities to study provides various opportunities to study nucleon structurenucleon structure

Low Low PP?? probes TMD parton distributions probes TMD parton distributions

High High PP?? probes quark-gluon correlations probes quark-gluon correlations ??

Integrated Integrated PP?? probes flavor decomposition probes flavor decomposition of PDFs, especially for of PDFs, especially for large xlarge x quark and quark and helicity distributions.helicity distributions.

December 17, 2004 JLab Hall A Upgrade 1 Semi-Inclusive DIS --opportunities at JLab upgrade Feng Yuan RBRC, Brookhaven National Laboratory.

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