Inclusive Scattering from Nuclei at x>1 and High Q2 with a 6 GeV Beam

E02-019 Analysis Update

Nadia Fomin

University of Tennessee

Hall C Users Group Meeting

January 22st, 2010

A long, long time ago….in Hall C

E02-019 ran in Fall 2004 Cryogenic Targets: H, 2H, 3He, 4He Solid Targets: Be, C, Cu, Au. Spectrometers: HMS and SOS (mostly HMS)

Introduction

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

Introduction

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

This talk: Focus on superfast quarks via ξ-scaling

Au

Jlab, Hall C, 2004

xbj ξ

F2A

)4

11(

2

2

22

QxM

x

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

2.5<Q2<7.4

)]2/(cos),()2/(sin),(2['4

'22

222

14

223

QWQW

Q

E

ddE

d

In the limit of high (ν,Q2), the structure functions simplify to functions of xbj, becoming

independent of ν,Q2

2.5<Q2<7.4

F2A for all settings and most nuclei for E02-019

ξ-scaling sure is pretty, but what does it mean?

Improved scaling with x ξ, but the implementation of TMCs leads to worse scaling by reintroducing the Q2 dependence

Rest of the talk deals only with carbon data

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11(

2

2

22

QxM

x

Can we get to SFQs? Yes we can! (Or so we think)

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

– both fit F2 to exp(-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

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

– Can’t have large higher twist contributions

CCFR

BCDMS

)(12

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44

242

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232

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grQ

xMh

rQ

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xQxF TMC

Schienbein et al, J.Phys, 2008

1

2

2)0(22

2

),(),(

u

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),()(),(

v

QvFvdvQg

• We want F2(0), the massless limit structure function as well as it’s Q2

dependence

How do we get to SFQ distributions

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)

– First naively tried using proton PDFs to map out the QCD evolution, but it didn’t work.

Iterative Approach

• We do okay at Q2<10 Gev/C2 with QCD evolution based on proton PDFs, but cannot use it for any sort of global model

• Solid black lines correspond to calculated F20,

using above mentioned inadequate QCD evolution

E02-019 carbon

SLAC deuterium

CERN Carbon

BCDMS carbon

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)

– First naively tried using proton PDFs to map out the QCD evolution, but it didn’t work.

– Fit the evolution of the existing data for fixed values of ξ (no good code exists for nuclear structure evolution, it seems)

Q2

• 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

3/)log(2 2

211)log(0 pQeppQp

• Use the QCD evolution to redo the F2

0 fit at fixed Q2 and to add more data (specifically SLAC)

F20 fit with a subset of

E02-019 and SLAC data

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

• 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

Putting it all Together

Final step: fit exp(-sξ) to F20 and

compare to BCDMS and CCFR

s=14.31±0.17

Fit region: 1.0 < ξ < 1.25

CCFR - (Q2=125 GeV/c2)s=8.3±0.7

BCMDS – (Q2: 52-200 GeV/c2)

s=16.5±0.5

Summary

• Once we account for TMCs and extract F20 – we believe 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 – finish analysis of other targets

• see if the “s” slope varies with nuclei