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Hadrons and Cold Nuclear Matter Rapporteur Presentation. Donald Geesaman JLAB PAC 36 24 August 2010. A person appointed by a deliberative body to investigate an issue or a situation and report to that body. History – as started by Mont in his ascent to Nuclear Physics.

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hadrons and cold nuclear matter rapporteur presentation

Hadrons and Cold Nuclear MatterRapporteur Presentation

Donald Geesaman

JLAB PAC 36

24 August 2010

A person appointed by a deliberative

body to investigate an issue or a situation

and report to that body

history as started by mont in his ascent to nuclear physics
History – as started by Mont in his ascent to Nuclear Physics

1983- EMC - Ratio of iron to deuterium

Note systematic errors are large and don’t show up on

electronic archive

1984-EMC- virtual photon energy dependence of leading hadron multiplicities

questions
Questions
  • Do we understand nuclei when probed at the partonic level?
  • Is the nucleon modified in the nuclear medium?
  • Are there other particles than nucleons in the nucleus?
  • Short range correlations emphasis pairs of nucleons that are close together. Is this the most likely place to see medium modifications?
    • Do we really understand short-range correlations in nuclei?
    • Do we understand transition from hadron picture to quark-gluon picture?
  • How do rapidly moving quarks become hadrons?

The Essence of Confinement

  • How does the nuclear medium affect the passage of fast quarks?
  • Can we use nuclear interactions to understand the space-time evolution of hadronic states and the cross section for interactions of short-lived particles with nucleons?
  • How are the hyperon-nucleon interactions and nucleon-nucleon reactions related in a QCD description?
our visual images of a nucleus

average spacing at ρnm ~ 1.8 fm

Radius of a nucleon ~ 0.8 fm

Radius of heavy nucleus at ~ 6 fm

Our visual images of a nucleus

OR

“nucleons” held apart by short range repulsion

but even in 208Pb, half the nucleons are in the surface

OR ???

we want to describe a nucleus
We want to describe a nucleus
  • Pure QCD Description
    • what are the clusters of quarks in a nucleus?
    • know the parton distributions change
      • EMC effect
      • shadowing
      • x>1
  • One problem is always whether our description of a bare proton is good enough. The second is how to actually calculate many body effects beyond mean field?
  • Hadronic Description
    • exemplified by ab initio calculations with potentials
      • NN
      • NNN + NNNN +
      • Bare form factors
      • Meson exchange currents
  • Past two decades have shown this is remarkably successful

One of my criteria for a successful theoretical description is multiple phenomena should be described, both at the hadronic and parton levels.

experiments

Experiments where I am on proposal

Experiments
  • Quark structure and short range correlations
    • E12-06-105 Inclusive scattering from nuclei with x>1 in the quasielastic and deeply inelastic regimes
    • E12-10-008 Detailed studies of nuclear dependence of F2 in light nuclei
    • PR12-10-012 Precision measurement of nucleon and nuclear structure functions to constrain gluon distributions
    • P12-10-004 Hard photodisintegration of a proton pair
    • E12-10-003 Deuteron electro-disintegration at very high missing momentum
  • Color Transparency
    • E12-06-106 Study of color transparency in exclusive vector meson production off nuclei
    • E12-06-107 The search for color transparency at 12 GeV
  • Hadronization
    • E12-06-117 Quark propagation and hadron formation
  • Hyperon interactions and other effects
    • E12-10-001 Study of light hypernuclei by pionic decay at JLab
related measurements
Related measurements
  • E12-06-113 Bonus12 The structure of the free neutron at large x-Bjorken
  • MeAsurement of the Fn2 /Fp2 , d/u RAtios and A=3 EMC Effect in deep inelastic electron scattering off the tritium and helium mirror nuclei.
nuclear modifications of parton distributions
Nuclear modifications of parton distributions

Most models have limited x

ranges

Either constructive

interference or other hadrons

exaggerated

EMC region

L short

Either f(y) peaks below 1

or F2N modified in nucleus

Nuclear motion

or short-range

corrections

As x-> 2 ratio goes to ~6

Shadowing

L ~ 2ν/Q2 ~ 1/x >2 fm

Destructive interference

or gluon recombination

slide9
Many of the general features of the A dependence of parton distributions are experimentally known. How do we progress?
  • Are binding effects included correctly? Look at light nuclei where structure changes rapidly and, in principle, can be calculated.
  • Nuclei with large isospin variation.
  • Can we tag hole state in A-1 nucleus?
  • Do we know neutron structure functions well enough?
  • Most of data emphasizes isoscalar effects. Can we isolate isovector effects?
  • Is there a correlation between short range correlations measured at x>1 and average medium modification of nucleon parton distributions
    • Can we correlate this with other measurements of short range correlations
  • Can we determine A dependence of different quark flavors – flavor tagging semi-inclusive DIS
  • Can we look for other observables that are sensitive to changes in nucleon structure?
    • (e,e’p)
    • Spin structure functions in nuclei.
examples of model trade offs
Examples of model trade offs
  • QMC - mean field model. f(y) peaks near 1. Large medium modifications are necessary to explain EMC effect. Dirac structure leads to effects in spin.
  • Kulagin and Petti work to cover entire x range. Yes!
    • Large binding effects
    • Still need medium/off-shell modifications to fit EMC region, assumed to vary like binding
    • Shadowing due to hadronic component of the photon- leads to Q2 dependence
    • Also include meson contributions. Small effect in Drell-Yan
    • Not clear if neutral current and charged current neutrino DIS are consistent
can we measure binding energy and spectator momentum dependence
Can we measure binding energy and spectator momentum dependence?
  • Test technical issue of how to include binding in calculation
  • Do we see nuclear dependence change for high momentum spectators which involve short distance interactions- Spectator tagging?

SLAC fit to heavy nuclei

(scaled to 3He)

JLab Data

Black points 3He

Benhar and Pandharipande 3He

Calculations by Pandharipande and Benhar for 3He and 4He

Magenta points 4He

I don’t like presenting

Isoscalar corrected ratio

Benhar and Pandharipande 4He

isovector emc effect is not well tested
Isovector EMC effect is not well tested

Kulagin and Petti (ArXiv:1004.3062v1) find in their model NMC d/p and JLab 3He/D give different F2n/F2p ratios. They advocate a 5% renormalization (~3 times published systematic error) of JLab data. I advocate reexamining isovector dependence of EMC effect.

nuclear effects in spin dependence
Nuclear Effects in Spin Dependence
  • Why its big?
    • Quark-Meson Coupling model:
    • Lower Dirac component of confined light quark modified most by the scalar field
slide15

If one understands parton propagation in nuclei, semi-inclusive DIS and flavor tagging could give insight into flavor dependence of EMC effect as it has for spin.HERMES has a new slant on the strange quark sea distributions. A. Airapetian et al Phys. Lett. B 666, 446 (2008)

Usually s(x)+sbar(x) ~ κ (ubar+ dbar) with κ~ 0.5

Best handle has been considered to be multi-muon events in neutrino scattering.

HERMES looks at DIS on deuterium and compares inclusive with semi-inclusive kaon multiplicities

hermes sees little strange quark content for x 0 1 and s x sbar x ubar x dbar x at x 0 03
HERMES sees little strange quark content for x>0.1 and s(x)+sbar(x) ~ ubar(x)+dbar(x) at x< 0.03!

A. Airapetian et al Phys. Lett. B 666, 446 (2008) Q2=2.5 GeV2

how is this consistent with years of neutrino multi muon data s c
How is this consistent with years of neutrino multi-muon data? ν + s → μ+ + c →μ-

NUTEV, PRD 64 112006(2001)

CTEQ, JHEP 42, 89 (2007) Q2=1.69

Note

5/3

comparison of ubar dbar s sbar with dbar ubar
Comparison of ubar+dbar-s-sbar with dbar-ubar

vs 0.25 *HERMES

Based on the HERMES result and assuming the strange quark distribution represents the gluon-splitting induced distribution, the shape of the non-perturbative

is similar to

can jlab probe the glue
Can JLab probe the glue?
  • dF2(Sn)/dx / dF2(C)/dx vs Q2
  • R = σL / σT

The primary question is can this precision be achieved.

Double ratios reduce systematics for measurements in two different spectrometers

is shadowing q2 dependent have to look at x 0 05
Is shadowing Q2 dependent? Have to look at x<0.05!

Q2 < 1at JLab12 in shadowing region.

Kulagin and Petti

(1004.3062) take difference between NMC and HERMES as evidence of Q2 dependence from vector dominance description of shadowing

relation between short range correlations and medium modifications emc effect
Relation between short range correlations and medium modifications/EMC effect?

Stolen from John Arrington

direct measurements of short range correlations in deuterium
Direct measurements of short range correlations in deuterium
  • D(e.e’p)n to high missing momentum
  • Is kinematics chosen to

emphasize/mimimize FSI and MEC?

pp quark counting rules vs rescattering
(γ,pp) Quark Counting rules vs Rescattering?

d(,p) scales at E>1 GeV

pp(,p) may scale at E>2.5 GeV

Oscillation signal rescattering picture

Does not require 12 GeV

slide24

Using secondary interactions in a nuclear target to study cross sections for short lived objects to interact with nucleons and to determine time scales in strong interaction dynamics

  • Hadronization
  • Color Transparency
hadronization the fundamental realization of confinement
Hadronization – the fundamental realization of confinement

Mostly taken from Accardi et al. RIVISTA DEL NUOVO CIMENTO   32, 439-553 (2009)

Other complications

Resonance decay

Overlap of target and projectile fragmentation regions at low z

with so many unknowns what can we vary or measure
With so many unknowns, what can we vary or measure?
  • Photon Energy
  • Nucleus – length of nuclear material for re-interaction
  • Hadron species
  • Fractional energy of the hadron, z
    • <tpreh>=f(z) (1-z) zν/Kstr
  • Transverse momentum
    • Gluon radiation or multiple scattering
  • Good news
    • energy loss effects are larger fractionally at low energy
    • Resolution is better at low energy
  • Need very differential cross section to try to separate these effects.
    • Hermes was first to see clear z dependence in nuclear ratios - EMC, E665 no z dependence
    • JLab offers much better statistics that can be sliced and diced in many ways
  • Essential for validating use of SIDIS
  • Interesting physics of confinement
  • Potentially valuable for comparison to hot nuclear matter
  • Data driven
  • Will there ever be serious theoretical predictions???
slide27

Jlab has the luminosity to slice and dice this:CLAS12: 12-06-117Likely not have the ν range to reach non-interacting limit to separate energy loss from attenuation?

color transparency

lf

lc

Color Transparency
  • Need
    • Compact size initial state
    • Small cross section with compact size
    • Evolution to full size take few fm
  • Diffractive Vector meson prepares

small size q-qbar pair with small color dipole

  • Must pay attention to coherence length

to measure formation length/transparency

effects

  • Solid 5 GeV results
  • 12 GeV results extend kinematic range in

both Q2 and range of formation and coherence

length

slide29

In non-diffractive channels, compact size of elementary interaction is still an issue.Many consider it a necessary condition for GPD applicability

Babar *→π0

  • Protons

No clear effect so far

Extend to Q2=16 GeV2 at 12 GeV

I am betting on no effect to higher Q2,

but it has to be measured.

  • Pions

First hint in non-diffractive production

Extend to Q2~9 GeV2

study of light hypernuclei by pionic decay at jlab
Study of light hypernuclei by pionic decay at JLab
  • Relationship of hyperon-nucleon interaction to N-N interaction remains an important clue in understanding low-energy baryon-baryon interaction
  • Also has impact on neutron star structure
  • My opinion is we have to get

past the exploratory phase and

into a production phase for this

to realize its promise, i.e. not study

one or two levels but many.

  • Pionic decay offers this promise if count rate and resolution is sufficient
pion decay spectra
Pion decay spectra

JLab goal

Finuda Results

summary
Summary
  • JLab12 can make significant contributions to understanding the implications of the quark structure of nuclei on nuclear structure
  • I believe one needs to see consistent effects at the quark and the hadron level to believe we truly understand what is happening.
  • Short-range correlations may show particular sensitivity to hadron structure in the nuclear medium. We need to correlate both direct and indirect (x>1) measurements.
  • The space-time evolution of hadronization requires 2-3 fold differential studies that have not been possible in the past.
  • The lower energy at JLab emphasizes energy loss and reinteraction effects compared to high energy measurements
  • SIDIS may provide new insight into nuclear dependence once propagation effects are quantified.
slide33
Most of the information on the sea came from deep-inelastic lepton scattering, especially charged current neutrino experiments

Q2 = (k-k’)2 = mass2 of the virtual boson

x= Q2/(2m) is the fractional momentum nucleon carried by the parton

  • = Ebeam- Escattered y =  / Ebeam

muon and electron scattering~

 charge current scattering ~

anti- c. c. scattering~

parity violating  scattering, F3~

parity violating anti- scattering~

The high statistics experiments are all done on nuclear targets

nuclear corrections in charged lepton and neutrino scattering are different
Nuclear corrections in charged lepton and neutrino scattering are different

Schienbein et al.

Charged lepton Fe/D

Neutrino Fe/D

F2(Fe from neutrinos)/F2(D determined w/o neutrino data)

experiments1

Experiments where I am on proposal

Experiments
  • Quark structure and short range correlations
    • E12-06-105 Inclusive scattering from nuclei with x>1 in the quasielastic and deeply inelastic regimes
    • E12-10-008 Detailed studies of nuclear dependence of F2 in light nuclei
    • PR12-10-012 Precision measurement of nucleon and nuclear structure functions to constrain gluon distributions
    • P12-10-004 Hard photodisintegration of a proton pair
    • E12-10-003 Deuteron electro-disintegration at very high missing momentum
  • Color Transparency
    • E12-06-106 Study of color transparency in exclusive vector meson production off nuclei
    • E12-06-107 The search for color transparency at 12 GeV
  • Hadronization
    • E12-06-117 Quark propagation and hadron formation
    • E12-07-101 Hadronization in nuclei by deep inelastic scattering
  • Other Nuclear effects
    • E12-07-106 The A Dependence of J/Psi Photoproduction near Threshold
    • E12-10-001 Study of light hypernuclei by pionic decay at JLab
j production near threshold

lc and lfchosen small

J/ψ Production Near Threshold
  • Exploratory experiment
  • Cross section near threshold poorly known
  • Small size leads to interesting dynamics
  • Extracting J/ψ-nucleon cross section through A dependence is of considerable interest, but handling nuclear corrections requires care because σγ→J/ψ is has strong energy dependence at ~11 GeV.