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Future Directions in studying QCD aspects of Nuclear Physics.  + (1540). Gerard van der Steenhoven (NIKHEF/KVI). International Nuclear Physics Conference, Götenburg, Sweden, July 2 nd , 2004. What remains to be discovered ? (*). WMAP satellite: 70% dark energy 25% dark matter

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Future directions in studying qcd aspects of nuclear physics
Future Directions in studying QCD aspectsof Nuclear Physics

+(1540)

Gerard van der Steenhoven

(NIKHEF/KVI)

International Nuclear Physics Conference,

Götenburg, Sweden, July 2nd, 2004


What remains to be discovered
What remains to be discovered ?(*)

  • WMAP satellite:

    • 70% dark energy

    • 25% dark matter

    • 5% visible matter

  • The task of LHC:

    • Unravel the Higgs Mechanism

      ~ 2% of the visible universe

  • The task of QCD nuclear physics:

    → Unravel the origin of 98% of

    the mass of the visible universe

(*) After: J. Maddox, What Remains to be Discovered?, XXXX Press, 2000


The qcd structure of the nucleon
The QCD structure of the nucleon

  • Lattice QCD calculations:

  • Deep-Inelastic Scattering:

(From: G. Bali, Glasgow)

The nucleon contains a large

amount of quark-antiquark

pairs and gluons.

gluon

Quark-antiquark pair


The challenges of qcd
The challenges of QCD

  • Extrapolate s to the size

  • of the proton, 10-15 m:

  • For s > 1 perturbative expansions fail………

  •  Non-perturbative QCD:

    • Proton structure & spin

    • Confinement

    • Nucleon-Nucleon forces

    • Hadron spectroscopy…..

Lattice QCD

simulations…


Future directions
Future directions

  • Hadronic form factors

    • Transition to pQCD, strangeness

  • Hadron spectroscopy

    • Pentaquarks, hybrids, glueballs,...

  • Spin structure

    • Gluons, transversity

  • Generalized parton distributions

    • Partonic correlations, orbital motion

  • Future facilities

MAMI-C


1 hadronic form factors
1. Hadronic Form Factors

  • Physics issues:

    • Proton: new data onGEp(Q2)/GMp(Q2)

    • Pion: transition to pQCD?

    • Axial form factors: role strangeness in proton

    • Kaon and hyperon form factors: hadron size

  • Relevant new facilities:

    • MAMI-C…………………… 2005

    • 12 GeV @ JLab …………. 2010

    • PAX @ GSI ……………… 2012 (Letter of Intend)



Time like form factors
Time-Like Form Factors

  • Measure single-spin asymmetry in :

    → Relative phase ofGMandGE

  • Entirely new concept:

    (F. Rathmann et al., LOI – 2004)

Polarized anti-protons in

the HESR ring @ FAIR:

- The PAX project -


Mami facility
MAMI facility

  • MAMI-C:

  • Emax→1500 MeV

  • Starting in 2005


2 hadron spectroscopy
2. Hadron spectroscopy

Harvest in 2003:

  • Allowed multi-q states in QCD:

    • states  mesons

    • states  baryons

    • states pentaquarks?

Discovery

Discovery

CLAS

Discovery


New narrow d sj states
New Narrow DsJ-states

  • BaBar studied decay

  • Two new mesons ?

  • The K+K-+-spectrum:

1+ @ 2.46 GeV

0+ @ 2.32 GeV


New charmed baryons
New charmed baryons

  • SELEX experiment at FermiLab (E781)

    • 600 GeV/c π/Σ beam

    • Decay schematic:

    • Discoveries:


New narrow s 1 states
New narrow S=+1 states

Chiral-Soliton mod.

prediction in 1997

by Diakonov, Petrov

and Polyakov (97):

Spring-8

H1

NA49


Accumulating experimental evidence

  • Results of three more experiments:

  • In all cases: a narrow peak near 1535 MeV/c2

HERMES

CLAS

SAPHIR


Overview of 1535 data
Overview of +(1535) data

  • Averaged mass value:

    • 1536.2 ± 2.6 MeV

    • /dof = 12.4/6

    • Conf. level = 0.053

  • Measured FHWMs:

    • in most cases consistent with exp. resolution

    • HERMES data:

HERMES paper:A. Airapetian et al, Physics Letters B 585 (2004) 213


Glueballs and hybrids
Glueballs and Hybrids

  • Partonic systems predicted in QCD:

  • “What remains to

    be discovered”:

    • Tetraquarks

    • Glueballs

    • Hybrids

    • ……….?


Glueball searches
Glueball searches

  • Lattice QCD: flux tubes

  • Normal mesons:

  • JPC = 0-+1+-2-+

  • Flux tubes (J=1, S=1):

  • JPC = 0-+0+- 1+-1-+2-+2+-

exotic (mass ~ 1.7 – 2.3 GeV)

  • Real photons couple to exotics via -VM transition


Hall d the gluex detector

CHL-2

Hall D: the GlueX detector

  • At JLab 12 GeV beam:

    • coherent  beam

    • new exp. Hall (D)

    • GlueX detector

Photon Flux 108g/s

Charged Particles

coverage 1° - 170°

momentum reso 1 - 2%

position reso 150 µm

vertex reso 500 µm

Photons

energy measured 1° - 120°

Pb glass reso 2 + 5%/√E

barrel reso 4.4%/√E

Trigger level 1 rate 20 kHz


Hybrid searches
Hybrid searches

  • Antiproton annihiliation: gluon rich

  • Production mechanism:

    • Charmonium production

    • Clear signature/tag

    • Not so many states


What is to be expected
What is to be expected?

  • First glimpse ??


Panda @ fair
PANDA @ FAIR*

: pellet target, particle ID, ~4

(*) Facility for Anti-proton and Ion Research


3. Search the carriers of proton spin

  • Three possible sources:

    • quarks:

      • valence quarks

      • sea quarks

    • gluons

    • orbital momentum

  • Mathematically:

½ = ½ Sq + DG + Lq

EMC: q ~ 10%

~ 20  10 %

?

?


How to probe the quark polarization
How to probe the quark polarization?

Polarized

deep

inelastic

electron

scattering

Measure yield asymmetry:

Parallel electron & proton spins

Anti-parallel electron & proton spins

In the Quark-Parton Model:

Spin-dependent Structure Function


Qcd analysis of world data 03
QCD analysis of world data (’03)

  • Next-to-Leading-Orderanalysis of -data

Excellent data forx > 0.01


Polarized parton densities
Polarized Parton Densities

  • First moments:

    • input scale

    • pol. singlet density:

    • pol. gluon density:

There must be other sources of angular momentum in the proton


Future data on and
Future data on and

  • Assume 400 pb-1 collected at e-RHIC:

Domains of existing precision data


Flavour decomposition of spin
Flavour decomposition of spin

  • Semi-inclusive deep

    inelastic lepton scattering

  • Hadron tags flavour of

    struck quark

  • Derive purity of tag from unpolarized data

Key issue: role of sea quarks in nucleon spin


Sea quark polarization
Sea quark polarization

  • Up and down quarks haveopposite spins

  • Sea is unpolarized...

  • First dataon :

[HERMES, hep-ex/0307064]

Chiral Quark Soliton Model


Future data on s and q valence
Future data on s and qvalence


Gluon polarization
Gluon polarization

  • High-pTpion pair production:

’99: First direct evidence for

non-zero gluon polarization

Curves consistent with


New experiments

 or 

photon

 or 

New experiments

  • Photon-gluon fusion:

    • COMPASS:

      • Open charm production:

      • HighpT–pairs (> 1 GeV)

  • Prompt photons (RHIC):


The compass experiment

Beam:160 GeV µ+

2 . 108 µ/spill (4.8s/16.2s)

Muon filter 2

MWPCs

ECal2 & Hcal2

~50m

SM2

Muon filter 1

ECal1 & Hcal1

RICH

GEM & MWPCs

SciFi

SM1

GEM & MWPCs

Silicon

SciFi

Scintillating

fibers

  • Polarization:

  • Beam: ~80%

  • Target:<50%>

GEM & Straws

Micromegas &Drift chambers

Polarized

target

The COMPASS experiment


First compass data
First COMPASS data

  • Tagging of D*→D0:

    • y-axis: MK - MK - m 

    • x-axis: MK - mD0

80% 2002 data

317 D0

MKp -mD0 [MeV/c2]


 or 

photon

 or 

 or 

(heavy flavor)

 or 

Gluon Polarization at RHIC

  • Longitudinal double spin asymmetry in :

  • Dominant processes:

Direct photon production

Di-jet production


Polarized protons at rhic

Absolute Polarimeter (H jet)

RHIC pC CNI Polarimeters

BRAHMS

PHOBOS

RHIC

s = 50 - 500 GeV

PHENIX

STAR

Siberian Snakes

Spin Rotators

Partial Solenoid Snake

LINAC

BOOSTER

Partial Helical Snake

Pol. Source

500 mA, 300 ms

AGS

AGS pC CNI Polarimeter

AGS Quasi-Elastic Polarimeter

200 MeV Polarimeter

Rf Dipoles

Polarized Protons at RHIC


Anticipated improvement in xG(x)

  • Present QCD analysis

  • Expected STAR data

M. Hirai, H.Kobayashi, M. Miyama et al.- preliminary


What is transversity
What is transversity?

transverse quark spin, dS

  • Three leading order quark distributions:

    momentum carried by quarks

    longitudinal quark spin,DS

  • Gluons don’t contribute toh1(x) - dominant in g1(x):

    •  Study nucleon spin while switching off the gluons

  • New QCD tests: Q2evolution h1(x); dS > DS(lattice)


Measuring transversity
Measuring transversity

-

+

quark flip

target flip

-

+

  • The relevant diagram:

    • helicity flip of quark & target

    • chirally odd process

  • Consequences:

    • no gluon contributions….

… & measure single-spin asymmetries:


Single spin asymmetries
Single – Spin Asymmetries

  • Sivers effect: AUT driven by

    orbital motion

    struck quark:

    measure L

  • Collins effect: AUT driven by

    fragmentation

    process: measure

    transversity


First data on transversity
First data on transversity

‘Collins’:

‘Sivers’:

First evidence for non-zero Collins and Sivers effects


Future options compass
Future options - COMPASS

  • First results based on 2002 data

  • Future:

    • Particle ID, more statistics, data on AUT for Collins/Sivers

    • Comparison HERMES data: measure Q2 evolution


Future options pax

l+

q2=M2

l-

q

qT

p

p

qL

Future options - PAX

[email protected]

  • Polarized antiproton beam x polarized target:

  • Double transverse spin asymmetry:

  • Key issue: amount of -polar.:

    • Concept proven in FILTEX exp.

    • Separate -ring being studied

Panda

anti-P


4 generalized parton distributions
4. Generalized Parton Distributions

  • Consider exclusive processes:

    • Deeply virtual Compton scatt.

    • Exclusive vector meson prod.

  • Collins et al. proved factorization theorem (1997):

GPD

Distribution amplitude

(meson) final state

Hard scattering

coefficient (QCD)

Generalized Parton

Distribution (GPD)

(Nasty: x = xBj for quarks and x = -xBj for antiquarks → x  [-1,1])


The remarkable properties of gpds

GPDs give access toOrbital Angular Momentum of Quarks

The remarkable properties of GPDs

  • Integration over x gives Proton Form Factors:

Dirac

Axial vector

Pauli

Pseudoscalar

  • The forward limit:

  • Second moment (X. Ji, PRL 1997):


Applying the gpd framework
Applying the GPD framework

  • GPDs enter description of different processes:

  • Take Fourier transform of leading GPD:

As Jq = ½q + Lqinformation on Jqgives data on Lq.

GPDs

Spatial distribution of quarks in the perpendicular direction


A 3d view of partons in the proton
A 3D-view of partons in the proton

Form Factor

Parton Density

Gen. Parton Distribution

A.V. Belitsky, D. Muller, NP A711 (2002) 118c


Experimental access to gpds

Key

differences

Experimental access to GPDs

  • Exclusive meson electroproduction:

    • Vector mesons (0):

    • Pseudoscalar mesons ():

  • Deeply virtual Compton scattering:

    • Beam charge asymmetry:

    • Beam spin asymmetry:

    • Longitudinal target spin asymmetry:


Selected dvcs results
Selected DVCS results

  • Azimuthal dependence

    beam-spin asymmetry:

  • Beam-charge and target spin asymmetries……..


Future data on dvcs at jlab
Future data on DVCS at JLab

  • 2000 hr data taking in upgraded CLAS detector


Prospects short term future 04 09
Prospects: short-term future ’04-’09

  • The spin structure of the proton:

    • Gluon polarization DG: COMPASS (& HERMES & RHIC)

    • Exploring transversity h1(x): HERMES, COMPASS (& RHIC)

    • GPDs: HERMES & JLab

  • Hadron spectroscopy

    • Pentaquarks: JLab

    • Heavier hadrons: COMPASS

  • RHIC spin:

    • Optimizing polarization

    • First double-spin asymm.

  • Mainz:

    • starting MAMI-C


Prospects long term future 2010

ELIC @ JLab with e-A coll

at 4 x 65 GeV2 & 1034 cm2/s

Prospects: long-term future ( 2010)

  • Design, construction and commissioning of various new QCD facilities in Europe and/or the US:

    • JLab 12 GeV upgrade (glueballs, high-x physics, GPDs)

    • PANDA (hybrids, GPDs)

    • PAX (transversity, FFs)

    • COMPASS-X10

    • eRHIC/ELIC

    • ………

EIC @ BNL

e-p coll at 10 x 250 GeV2 &1033 cm2/s


Conclusion
Conclusion

  • Major progress in understanding the QCD structure of nucleons

  • Many new results anticipated in the coming years

  • Many new facilities in construction or under design (in EU and US)

    QCD develops into a key area

    of research for nuclear, particle

    and astrophysics alike.


ELIC @ JLab with e-A coll

at 4 x 65 GeV2 & 1034 cm2/s


Key qcd successes
Key QCD successes

  • Data on the DIS structure

  • function F2(x,Q2):

  • The energy (or distance) dependence of s:


Pion form factor
Pion Form Factor

  • Pion Form Factor:

    • simple quark structure

    • pQCD prediction:

Search transition to pQCD regime !


Upgrade magnets and power supplies

CHL-2

Enhance equipment in existing halls

Add new hall

11

6 GeV CEBAF

12


u

u

d

d

u

d

d

u

u

u

u

u

u

d

d

d

d

d

d

u

a) Five quarks in a s-

state configuration.

b) Five quarks in a K+ -n

molecular configuration.

Pentaquark models….....

c) Five quarks in a strong

diquark correlation state.

d) Collective excitation of

a multiquark configuration.


Why is transversity important
Why is transversity important?

  • Third leading order quark distribution:

    • required for complete knowledge of the nucleon

  • Helicity conservation:

    • gluons don’t contribute toh1(x), while they dominateg1(x):

       study nucleon spin while switching off the gluons

  • Novel testable QCD predictions:

    • Tensor charge(dS)much larger than axial charge(DS):

       Lattice QCD:dS= 0.56 (9), whileDS= 0.18 (10)

    • Q2evolution ofh1(x) is much weaker than that ofg1(x)

       Novel test of DGLAP equations


What is the diagram
What is the diagram?

-

-

+

+

+

+

+

+

+

-

-

+

+

-

+

+

+

+

-

+

quark flip

target flip

-

+

  • Label the quark helicities:

Transversity: helicity flip of quark and target


Frequently asked questions
Frequently asked questions

  • Operator structure:

  • What happens in the non-relativistic limit?

  • Why no gluon contribution?

    • gluon helicity flip:

    • nucleon helicity flip:

+

-

+

-


How to measure h 1 x
How to measure h1(x)?

  • Drell-Yan & related reactions:

  • Semi-inclusive deep-inelastic scattering:

-

+

+

-

Chiral-odd fragmentation process

+

-

+

-


Measuring transverse asymmetries
Measuring transverse asymmetries

  • Evaluate the azimuthal asymmetry wrtStarget:

  • Semi-inclusive DIS with a transversely polarized H target:

Transverse Target Magnet at HERMES


Extraction of sin moments
Extraction of sin() moments:

  • Define azimuthal angles:

    • azimuthal spin orientationfs

    • azimuthal hadron anglefh

  • Amplitude of sin(+x) dependence

  • containsrelevant physics:

  • Longitudinal polarized target: fs= 0 → no distinction

“Collins”

“Sivers”


First rhic results
First RHIC results

  • Forward0prod. at STAR:

  • Single spin-asymmetry in

  • Relevance: transverse spin

  • Red curve: Collins effect

    (~ transversity)

  • Blue curve: Sivers effect

    (~ pT-dependence of PDF)

  • Green curve: Twist-3 eff.


Generalized parton distributions
Generalized Parton Distributions

Pseudovector GPDs

Pseudoscalar GPDs

  • Four independent Generalized Parton Distributions:

  • Some GPD properties:

    • Non-pQCD object

    • Not calculable from first principles

    • Unifies description of ALL reactions with hadrons

    • Gives access to spatial distributionof quarks

Spin independent GPDs

Spin dependent GPDs

GPDs are a probe of correlations between partons


Orbital angular momentum
Orbital angular momentum

½ = ½ Sq + DG + Lq

  • The origin of proton spin:

  • A new idea: azimuthal asymmetry in0production

Inclusive data:0.2

High pT pairs:1.0

Orb. ang. mom.: -0.6 ?

Ju = Su + Lu


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