Transition from QES to DIS at x>1
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Transition from QES to DIS at x>1 (Jlab Experiment 02-019). Nadia Fomin University of Tennessee Hall C Summer Workshop August 27 th , 2010. E02-019 Overview.

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Transition from QES to DIS at x>1 (Jlab Experiment 02-019)

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Transition from qes to dis at x 1 jlab experiment 02 019

Transition from QES to DIS at x>1

(Jlab Experiment 02-019)

Nadia Fomin

University of Tennessee

Hall C Summer Workshop

August 27th, 2010


Transition from qes to dis at x 1 jlab experiment 02 019

E02-019 Overview

  • Inclusive Scattering only the scattered electron is detected, cannot directly disentangle the contributions of different reaction mechanisms.

  • Inclusive Quasielastic and Inelastic Data allows the study of a wide variety of physics topics

    • Duality

    • Scaling (x, y, ξ, ψ)

    • Short Range Correlations – NN force

    • Momentum Distributions

    • Q2 –dependence of the F2 structure function


A long long time ago in hall c at jefferson lab

A long, long time ago….in Hall C at Jefferson Lab

  • E02-019 ran in Fall 2004

  • Cryogenic Targets: H, 2H, 3He, 4He

  • Solid Targets: Be, C, Cu, Au.

  • Spectrometers: HMS and SOS (mostly HMS)

  • Concurrent data taking with E03-103 (EMC Effect – Jason Seely & Aji Daniel)


Transition from qes to dis at x 1 jlab experiment 02 019

The inclusive reaction

e-

e-

e-

e-

M*A-1

M*A-1

MA

MA

Same initial state

Different Q2 behavior

DIS

QES

W2=Mn2

W2≥(Mn+Mπ)2

Spectral function

3He


Transition from qes to dis at x 1 jlab experiment 02 019

Inclusive Electron Scattering

(x>1)x=1 (x<1)

The quasi-elastic contribution dominates the cross section at low energy loss, where the shape is mainly a result of the momentum distributions of the nucleons

As ν and Q2 increase, the inelastic contribution grows

A useful kinematic variable:

JLab, Hall C, 1998

Fraction of the momentum carried by the struck parton

A free nucleon has a maximum xbj of 1, but in a nucleus, momentum is shared by the nucleons, so 0 < x < A


Transition from qes to dis at x 1 jlab experiment 02 019

Deuterium

  • Usually, we look at x>1 results in terms of scattering from the nucleon in a nucleus and they are described very well in terms of y-scaling (scattering from a nucleon of some momentum)

    • Quasielastic scattering is believed to be the dominant process

Deuterium


Transition from qes to dis at x 1 jlab experiment 02 019

Short Range Correlations => nucleons with high momentum

Independent Particle Shell Model :

For nuclei, Sα should be equal to 2j+1 => number of protons in a given orbital

However, it as found to be only ~2/3 of the expected value

The bulk of the missing strength it is thought to come from short range correlations

  • NN interaction generates high momenta (k>kfermi)

  • momentum of fast nucleons is balanced by the correlated nucleon(s), not the rest of the nucleus


Transition from qes to dis at x 1 jlab experiment 02 019

Short Range Correlations

2N SRC

Deuteron

3N SRC

Carbon

NM


Transition from qes to dis at x 1 jlab experiment 02 019

Short Range Correlations

  • To experimentally probe SRCs, must be in the high-momentum region (x>1)

  • To measure the probability of finding a correlation, ratios of heavy to light nuclei are taken

  • In the high momentum region, FSIs are thought to be confined to the SRCs and therefore, cancel in the cross section ratios

P_min (GeV/c)

x


Transition from qes to dis at x 1 jlab experiment 02 019

Short Range Correlations – Results from CLAS

Egiyan et al, Phys.Rev.C68, 2003

No observation of scaling for Q2<1.4 GeV2

Egiyan et al, PRL 96, 2006


E02 019 2n correlations in ratios to deuterium

E02-019: 2N correlations in ratios to Deuterium

18° data

Q2=2.5GeV2


E02 019 2n correlations in ratios to deuterium1

E02-019: 2N correlations in ratios to Deuterium

18° data

Q2=2.5GeV2

R(A, D)


A d ratios previous results

A/D Ratios: Previous Results

18° data

Q2=2.5GeV2

4He

R E02-019 NE3

3.92±0.14

56Fe

5.10±0.07

5.42±0.19

Plots by D. B. Day


E02 019 2n ratios

E02-019 2N Ratios

3He

3He

12C

12C


2n correlations in ratios to 3 he

2N correlations in ratios to 3He

Hall B (statistical errors only)

E02-019


Transition from qes to dis at x 1 jlab experiment 02 019

Connection between EMC effect and SRC ratios?


Transition from qes to dis at x 1 jlab experiment 02 019

Connection between EMC effect and SRC ratios?

  • Very similar behavior with A, including 9Be

  • Future experiments will further fill in this map


E02 019 ratios

Q2 (GeV2)

CLAS: 1.4-2.6

E02-019: 2.5-3

E02-019 Ratios

  • Excellent agreement for x≤2

  • Very different approaches to 3N plateau, later onset of scaling for E02-019

  • Very similar behavior for heavier targets


E02 019 ratios1

Q2 (GeV2)

CLAS: 1.4-2.6

E02-019: 2.5-3

E02-019 Ratios

For better statistics at x>2.5, take shifts on Jlab E08-014

  • Excellent agreement for x≤2

  • Very different approaches to 3N plateau, later onset of scaling for E02-019

  • Very similar behavior for heavier targets


Coming soon to hall a x 2

Coming soon to Hall A: x>2

  • 2H

  • 3He

  • 4He

  • 12C

  • 40Ca

  • 48Ca


E02 019 kinematic coverage

E02-019 Kinematic coverage

  • E02-019 ran in Fall 2004

  • Cryogenic Targets: H, 2H, 3He, 4He

  • Solid Targets: Be, C, Cu, Au.

  • Spectrometers: HMS and SOS (mostly HMS)

  • Concurrent data taking with E03-103 (EMC Effect – Jason Seely & Aji Daniel)


Transition from qes to dis at x 1 jlab experiment 02 019

On the higher Q2 side of things

2.5<Q2<7.4

2.5<Q2<7.4

Au

Jlab, Hall C, 2004

F2A

x

ξ

  • In the limit of high (ν, Q2), the structure functions simplify to functions of x, becoming independent of ν, Q2 – incoherent sum of quark distributions

  • As Q2∞, ξx, so the scaling of structure functions should also be seen in ξ, if we look in the deep inelastic region.

  • However, the approach at finite Q2 will be different.

  • It’s been observed that in electron scattering from nuclei, the structure function F2, scales at the largest measured values of Q2 for all values of ξ


Transition from qes to dis at x 1 jlab experiment 02 019

SLAC, NE3

Jlab, E89-008

Q2 -> 0.44 - 2.29 (GeV/c2)

Q2 -> 0.44 – 3.11(GeV/c2)


Scaling is it a coincidence or is there meaning behind it

ξ-scaling: is it a coincidence or is there meaning behind it?

  • Interested in ξ-scaling since we want to make a connection to quark distributions at x>1

  • Improved scaling with x->ξ, but the implementation of target mass corrections (TMCs) leads to worse scaling by reintroducing the Q2 dependence


Transition from qes to dis at x 1 jlab experiment 02 019

ξ-scaling: is it a coincidence or is there meaning behind it?

  • Interested in ξ-scaling since we want to make a connection to quark distributions at x>1

  • Improved scaling with x->ξ, but the implementation of target mass corrections (TMCs) leads to worse scaling by reintroducing the Q2 dependence

  • TMCs – accounting for subleading 1/Q2 corrections to leading twist structure function


Transition from qes to dis at x 1 jlab experiment 02 019

From structure functions to quark distributions

  • 2 results for high x SFQ distributions (CCFR & BCDMS)

    • both fit F2 to e-sx, where s is the “slope” related to the SFQ distribution fall off.

    • CCFR: s=8.3±0.7 (Q2=125 GeV/c2)

    • BCMDS: s=16.5±0.5 (Q2: 52-200 GeV/c2)

  • We can contribute something to the conversation if we can show that we’re truly in the scaling regime

    • Can’t have large higher twist contributions

    • Show that the Q2 dependence we see can be accounted for by TMCs and QCD evolution


Transition from qes to dis at x 1 jlab experiment 02 019

CCFR

BCDMS


Transition from qes to dis at x 1 jlab experiment 02 019

How do we get to SFQ distributions

Measured structure function

  • We want F2(0), the scaling limit (Q2→∞)structure function as well as its Q2dependence

Schienbein et al, J.Phys, 2008


Iterative approach

Iterative Approach

  • Step 1 – obtain F2(0)(ξ,Q2)

    • Choose a data set that maximizes x-coverage as well as Q2

    • Fit an F2(0), neglecting g2 and h2 for the first pass

    • Use F2(0)-fit to go back, calculate and subtract g2,h2, refit F2(0), repeat until good agreement is achieved.

  • Step 2 – figure out Q2 dependence of F2(0)

    • Fit the evolution of the existing data for fixed values of ξ


Transition from qes to dis at x 1 jlab experiment 02 019

θHMS

Q2(x=1)

Cannot use the traditional W2>4GeV/c2 cut to define the DIS region

Don’t expect scaling around the quasielastic peak (on either side of x=1)


Transition from qes to dis at x 1 jlab experiment 02 019

  • Fit log(F20) vs log(Q2) for fixed values of ξto

  • p2,p3 fixed

  • p1 governs the “slope”, or the QCD evolution.

  • fit p1 vs ξ

ξ=0.5

ξ=0.75

Q2

  • Use the extracted Q2 dependence to redo the F20 fit at fixed Q2 and to add more data (specifically SLAC)


Transition from qes to dis at x 1 jlab experiment 02 019

P1 parameter vs ξ, i.e. the Q2 dependence

F20 fit with a subset of E02-019 and SLAC data

Final fit at Q2=7 GeV2


Transition from qes to dis at x 1 jlab experiment 02 019

E02-019 carbon

SLAC deuterium

BCDMS carbon

| CCFR projection

(ξ=0.75,0.85,0.95,1.05)

Putting it all Together

  • With all the tools in hand, we apply target mass corrections to the available data sets

  • With the exception of low Q2 quasielastic data – E02-019 data can be used for SFQ distributions

Submitted to Phys.Rev. Lett

[arXiv:1008.2713]


Transition from qes to dis at x 1 jlab experiment 02 019

Final step: fit exp(-sξ) to F20 and compare to BCDMS and CCFR

BCDMS

CCFR

CCFR – (Q2=125GeV2)

s=8.3±0.7

BCDMS – (Q2: 52-200 GeV2)

s=16.5±0.5

s=15.05±0.5


Analysis repeated for other targets

Analysis repeated for other targets

All data sets scaled to a common Q2 (at ξ=1.1)

Submitted to Phys.Rev. Lett

[arXiv:1008.2713]


X 1 at 12 gev e12 06 105

x >1 at 12 GeV (E12-06-105)

  • 2H

  • 3He

  • 4He

  • 6,7Li

  • 9Be

  • 10,11B

  • 12C

  • 40Ca

  • 48Ca

  • Cu

  • Au


Transition from qes to dis at x 1 jlab experiment 02 019

Summary

  • Short Range Correlations

    • ratios to deuterium for many targets with good statistics all the way up to x=2

    • different approach to scaling at x>2 in ratios to 3He than what is seen from CLAS

    • Future: better/more data with 3He at x>2 in Hall A (E08-014)

  • “Superfast” Quarks

    • Once we account for “TMCs” and extract F20 – we find our data is in the scaling regime and can be compared to high Q2 results of previous experiments

    • appears to support BCDMS results

    • TO DO: check our Q2 dependence against pQCD evolution (in progress)

    • Follow-up experiment approved with higher energy (E12-06-105)


Transition from qes to dis at x 1 jlab experiment 02 019

Connection between EMC effect and SRC ratios?


Transition from qes to dis at x 1 jlab experiment 02 019

Connection between EMC effect and SRC ratios?


Transition from qes to dis at x 1 jlab experiment 02 019

Greater disagreement in ratios of heavier targets to 3He

Show?


Transition from qes to dis at x 1 jlab experiment 02 019

F2A for all settings and most nuclei for E02-019


Transition from qes to dis at x 1 jlab experiment 02 019

  • Usually, we look at x>1 results in terms of scattering from the nucleon in a nucleus and they are described very well in terms of y-scaling (scattering from a nucleon of some momentum)

    • Quasielastic scattering is believed to be the dominant process


Transition from qes to dis at x 1 jlab experiment 02 019

Deuterium

  • Usually, we look at x>1 results in terms of scattering from the nucleon in a nucleus and they are described very well in terms of y-scaling (scattering from a nucleon of some momentum)

    • Quasielastic scattering is believed to be the dominant process

Deuterium


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