slide1
Download
Skip this Video
Download Presentation
x>1: Short Range Correlations and “Superfast” Quarks Jlab Experiment 02-019

Loading in 2 Seconds...

play fullscreen
1 / 41

x>1: Short Range Correlations and “Superfast” Quarks Jlab Experiment 02-019 - PowerPoint PPT Presentation


  • 103 Views
  • Uploaded on

x>1: Short Range Correlations and “Superfast” Quarks Jlab Experiment 02-019. Nadia Fomin University of Tennessee User Group Meeting Jefferson Lab June 9 th , 2010. E02-019 Overview.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' x>1: Short Range Correlations and “Superfast” Quarks Jlab Experiment 02-019' - teenie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

x>1: Short Range Correlations and “Superfast” Quarks

Jlab Experiment 02-019

Nadia Fomin

University of Tennessee

User Group Meeting

Jefferson Lab

June 9th, 2010

slide2

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 jlab
A long, long time ago….in Hall C at JLab
  • 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)
slide4

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

slide5

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

slide6

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
slide7

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
slide8

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
slide9

Short Range Correlations

2N SRC

Deuteron

3N SRC

Carbon

NM

slide10

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

slide11

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

a d ratios previous results
A/D Ratios: Previous Results

18° data

Q2=2.5GeV2

4He

R E02-019 NE3

3.87±0.12

56Fe

5.38±0.17

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

Can extract value of plateau – abundance of correlations compared to 2N correlations in 3He

slide17

2N correlations in ratios to 3He

A measure of probability of finding a 2N correlation:

Recently learned that this correction is probably not necessary (pn >>pp)

In the example of 3He:

Hall B results (2003) E02-019

statistical errors only

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, take shifts on 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
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)
slide21

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.
  • 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
slide22

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
slide24

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

Following analysis discussion focuses on carbon data

slide25

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
slide26

CCFR

BCDMS

slide27

How do we get to SFQ distributions

  • We want F2(0), the massless limit structure function as well as its Q2dependence

Schienbein et al, J.Phys, 2008

iterative approach
Iterative Approach
  • Step 1 – obtain F2(0)(x,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 QCD evolution of F2(0)
    • Fit the evolution of the existing data for fixed values of ξ (no good code exists for nuclear structure evolution, it seems)
slide29

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)

slide30

Fit log(F20) vs log(Q2) for fixed values of ξ to

  • p2,p3 fixed
  • p1 governs the “slope”, or the QCD evolution.
  • fit p1 vs ξ

ξ=0.5

ξ=0.75

Q2

  • Use the QCD evolution to redo the F20 fit at fixed Q2 and to add more data (specifically SLAC)
slide31

P1 parameter vs ξ, i.e. the QCD evolution

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

Final fit at Q2=7 GeV2

slide32

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

E02-019 carbon

SLAC deuterium

BCDMS carbon

slide33

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

E02-019 carbon

SLAC deuterium

BCDMS carbon

| CCFR projection

(ξ=0.75,0.85,0.95,1.05)

slide34

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)

slide36

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