Hadronization and Quark Propagation in Nuclear Medium

Jian-ping Chen, Jefferson LabINT09 on JLab 12 GeV, Oct.26-30, 2009

Introduction

Hadronization and Nuclear medium effects

Current status of nuclear SIDIS to study hadronization

JLab 12 GeV program on hadronization

CLAS12 (large acceptance) (Will Brook’s talk)

SHMS+HMS (high luminosity/small acceptance)

What can high luminosity/small acceptance measurements contribute?

Opportunity with SoLID (high luminosity/large acceptance)

Summary

Acknowledgement: Thanks to A. Accardi, K. Wang and B. Norum for providing plots

and nice pictures. Also “borrowed” from colleague’s talks.

Introduction

Nuclear Medium as a Laboratory to Study QCD

Strong Interaction and QCD• Strong interaction, running coupling ~1 -- QCD: accepted theory for strong interaction -- asymptotic freedom (2004 Nobel) perturbation calculation works at high energy -- interaction significant at intermediate energy quark-gluon correlations -- interaction strong at low energy confinement -- gluons self interacting

• A major challenge in fundamental physics: -- Understand QCD in all regions, including strong

(confinement) region

• Fundamental degrees of freedom: quarks, gluons Natural effective degrees of freedom: hadrons -- transition and relation between two pictures E

s

Confinement and Nucleon

• Colors are confined in hadronic system• Can not directly detect quarks/gluons (colored objects)• Only hadron (color singlet) properties are observables • Observables are gauge invariant

• Both nucleon and nucleus are good laboratories to study QCD• Nucleon: simpler, often can use fundamental DOF to describe processes

• pQCD, description of hadronic properties in terms of quarks/gluons• It is only an approximation at any finite Q2

• power (twist) corrections and order (as) corrections• Multi-parton correlations• Partons in-separable from gluon field due to gauge invariance • Beyond co-linear factorization • Multi-dimensional structure and distributionsTransverse dimension is crucial for complete understanding QCD

Confinement and Hadronization

• Confinement from a simple experimentalist point of view:• DIS directly probe partons, which always hadronize on the

way out can not directly detect partons

• Hadronization is one of the fundamental processes in QCD• Colored objects always interact with gluon field/sea to

become color neutral before being detected• Nuclear medium provides a natural laboratory to study

hadronization• Understanding cold matter quark propagation important for

hot matter study

QCD and Nuclei

• Most of the strong interaction confined in nucleon, only residual strong interaction remains among nucleons in a nucleus (exponential tail?)• Effective N-N interaction with meson exchange

• Study QCD with nuclei• Short range not well understood: Short range correlations• Nuclei at extreme conditions: QGP, CGC (gluon saturation)• Nuclear medium effects

• EMC effect• Coulomb Sum Rule quenching(?)• Form Factor Modification(?) in 4He• Color Transparency • Quark propagation in cold and hot nuclear matter

Short-Range Correlation Pair Factions

R. Subedi et al., Science 320 (2008) 1476).

7

Short Range Correlations and Cold Dense Matter

Mean field

MF+2-N SRC

MF+multinucleon SRC

• SRC accessible at 12 GeV reach baryon densities comparable to neutron stars

CDR

Nuclear Medium Effects (I)

• EMC effect, shielding and anti-shielding

J. Ashman et al., Z. Phys. C57, 211 (1993)

J. Gomez et al., Phys. Rev. D49, 4348 (1994)

Polarized EMC effect

(Ian Cloet,

Wolfgang Bentz,

Tony Thomas)

p

A

gg

1

1

p

A

F

F

2

2

EMC Effect in PVDIS: CSV in Heavy Nuclei

Can be measured with SoLID (Cloet, Bentz,

and Thomas)

5%

Nuclear Medium Effects (II) Coulome Sum Rule

Probing a nucleon inside a nucleus

Possible modification of thenucleons’ property inside nuclei

E01-015

Precision Measurement of Coulomb Sum at q=0.5-1 GeV/c

Spokespersons: J. P. Chen, S. Choi and Z. E. MezianiPhD students: Y. Oh, H. Yao, X. Yan,

• New NaI detector for

background control

• Data taking last year

• Analysis well underway

• Expect preliminary results in a few

months

Nuclear Medium Effects (III)GE/GM with polarization transfer in 4He

Nuclear Medium Effects (IV)Color Transparency

• 12C(e,e’p)

Nuclear Medium Effects (V)

• Quark propagation in cold and hot matter

SIDIS A-A Collision

Eh = z~ 2 - 20 GeV Eh = pT ~ 2 – 20 GeV(HERMES/JLab) (RHIC)

Nuclei as Laboratories to Study Hadronization

What have we learned?

Nuclei: Laboratories to study Hadornization

• Use different size of nuclei to filter hadronization

SIDIS to study hadronization

• Quark propagation

Mechanism for Quark Propagation

• Non-perturbative in nature• Models: Accardi et al., Wang et al., Kopeliovich, et al.

Attenuation in SIDIS

• HERMES results help to sort out models and to understand mechanisms

• Energy loss (gluon bremsstrahlung)

Hadronization outside

• Pre-hadron absorption Color neutralization inside)

-Scaling

Pre-hadron absorption

> 0

Energy loss

< 0

PT - broadening

PT-broadening help to study production time, multiple scattering and beyond.

A, z, , Q2 dependence

PT-Broadening

Summary of Current Status

• HERMES results have made an impact in the study of a hadronization

• Clear attenuation in nuclear medium

• Scaling (prefer absorption mechanism?)

• PT-broadening: study production/formation length, multiple scattering, …

• Preliminary JLab CLAS 6 data: multi-variable binning

• What’s next?

Planned 12 GeV Measurements

CLAS12 (Hall B) and SHMS+HMS (Hall C)

12 GeV Upgrade Kinematical Reach

• Reach a broad DIS region • Precision SIDIS for

hadronization study

• Many other opportunities

(Valence quark, TMDs, GPDs)

Planned 12 GeV Measurements

• CLAS12 measurements (Will Brooks’ talk)

Large acceptance, extensive coverage

• HMS/SHMS measurements • High luminosity, small acceptance• E12-07-101, conditional approval• At selected kinematics, precision study

• What should be the choice of kinematics?

E12-07-101

• Overview: • SIDIS, A(e,e’/K+-)X• Targets: 1H, 2H, 12C, 64Cu and 184W• Q2: 2.5 – 6 GeV2, focus on high Q2

• = 6 GeV

• PT up to 0.8 GeV/c

• z ~ 0.5-0.9, focus on large z• Good PID for pions and Kaons

• Study Q2 dependence

PT/z dependence at high Q2

A dependence

Spokespersons: J. P. Chen, H. Lu, B. Norum, K. Wang

E12-07-101

• Accessible phase space with HMS/SHMS

PT-broadening

• PT broadening provides (almost direct) information on formation length (Kopeliovich model)

sensitive to z (at large z)

and A

E12-07-101 Projection

• Projected RM vs. z for + and proton on 3 targets

12C, 64Cu,184W

E12-07-101 Projection

• Projected RM vs. PT for 3 bins of z

Z=0.65, 0.75, 0.85

Discussion

• HMS/SHMS (High luminosity, small acceptance) measurements complementary to large acceptance CLAS12 measurements

• What should be the choice of kinematics?• need inputs

A new possibility

Solenoid Detector for SIDIS in Hall A

Solenoid detector for SIDIS at 11 GeVProposed for PVDIS at 11 GeV

FGEMx4

LGEMx4 LSGas Cherenkov

HG

Aerogel

GEMx2

SH

PS

Z[cm]

Y[cm

]

Yoke

Coil

3HeTarget

Power of SOLid for Sivers

Discussion• Large acceptance (~700 msr) and high luminosity (1037) provide

the unprecedented precision to map multi-variable dependence of nuclear SIDIS for hadronization study• RM and <PT>

• +, - and K+, K- and other particles

• Measure A, Q2, , PT and z dependence• Extract production length and formation length• Understand mechanisms: energy loss, absorption, … • Study current fragmentation and target fragmentation• Isolate different effects, differentiate models • Gain solid understanding of quark propagation in cold matter, forming a

baseline for hot matter study

• Shed light on fundamental processes of QCD: effects due to gluon field, sea (QCD vacuum) and confinement.

Summary

• Hadronization is a fundamental process of QCD Non-perturbative effect Related to QCD gluon field/sea/vacuum and confinement Nuclear medium is an idea lab to study hadronization

• Current status Our understanding is still primitive, a lot to be learned Many models, different mechanisms HERMES results provide valuable information and constraints to models CLAS 6 GeV started to provide precision measurements with multi-variables

• JLab 12 GeV SHMS/HMS, small acceptance with high luminosity complementary to CLAS12

large acceptance measurements• Needs input to optimize choice of kinematics

An opportunity for high-precision multi-variable measurements with SOLID (large acceptance and high luminosity)

• Help understanding fundamental QCD processes Lead to breakthrough ?