# Presentation: 491023

## A Precise Measurement of the EMC Effect in Light Nuclei

- Dave Gaskell
- Jefferson Lab
- PANIC
- October 24, 2005

-  Motivation and existing data
-  JLab Experiment E03-103
-  Preliminary Results

## The EMC Effect

- Measurements of
-     (EMC, SLAC, BCDMS) have demonstrated modification of quark distributions in nuclei
- Magnitude of effect depends on A, but not the shape

-   Typically broken in 3 regions
-          x<0.1: shadowing
-   0.1<x<0.3: small enhancement (nuclear pions?)
-          x>0.3: suppression -> “EMC Effect”
-   Fourth region at x>0.7 -> ratio increases, crosses 1.0
- - Attributed to Fermi smearing

## Explaining the EMC Effect

- Conventional Models
- Some combination of Fermi
-   motion and binding
-  Fermi motion + binding +
-    nuclear pions

- Exotic Models
-  Dynamical rescaling
-  Multiquark clusters

- K.E. Lassila and U.P. Sakhatme
- Phys. Lett. B209, 343 (1988)

- Benhar, Pandharipande, and Sick
- Phys. Lett. B410, 79 (1997)

## Existing EMC Data 

- SLAC E139 probably the most extensive data set for x>0.2
- Measured A/D for  A=4 to 197
- 4He, 9Be, C, 27Al, 40Ca, 56Fe, 108Ag, and 197Au
- Size at fixed x varies with A, but shape is nearly constant
- Data set could be improved with
- Higher precision data for 4He
- Addition of 3He data
- Precision data at large x

- SLAC E139

## A-Dependence of the EMC Effect

- Existing 4He data  cannot distinguish between log(A) and  dependence of EMC Effect
- Increased precision on 4He, addition of 3He will clearly put new constraints on parameterizations of A dependence

- E139
- x=0.6

## EMC Effect in Light Nuclei

- Measurement of EMC effect for very light nuclei (A=3 and 4) will allow comparison with exact nuclear calculations
- With the “conventional” nuclear physics under control, it will be easier to rule out or support more exotic explanations

- 3He

- 4He

## JLab Experiment E03-103

**JLab Experiment E03-103**

- Ran in Hall C at JLab summer and fall 2004
- Concurrent with E02-019 (measured inclusive cross sections at x>1)
- Measured A(e,e’) at 5.77 GeV from H, 2H, 3He, 4He, Be, C, Al, Cu, and Au at 18, 22, 26, 32, 40, and 50 degrees

- Took additional data at     5 GeV on Carbon and Deuterium to investigate Q2 dependence
- In canonical DIS region (W>2 GeV) up to x=0.6
- Large Q2 at x>0.6 suggests we may be able to extract meaningful EMC ratios up to x ~ 0.85

## E03-103 and E02-019 Analysis 

- Analysis still ongoing
- “Data processing” pretty much final
- Track reconstruction
- Efficiencies
- Charge symmetric backgrounds
- 1st pass cross sections  will be used to iterate:
- Radiative corrections
- Bin-centering corrections
- To do – Coulomb corrections

##  Carbon EMC Ratio

-  Existing precision Carbon data serves as a nice cross-check
-  Points include 1.5% point-to-point systematic uncertainty (radiative corrections, bin centering)
-  3% normalization uncertainty (target thickness, radiative and bin centering corrections)

## 4He EMC Ratio

-  Projected final uncertainties will be 0.7% point-to-point, 1.5% normalization (compare to 1.6% and 2.2% respectively for E139)

## Projected Uncertainties for 3He

-  Normalization uncertainty will be a little larger – 1.9% mostly due to 3He thickness (large temperature and pressure derivatives)
-  Extraction of 3He ratio made more difficult due to
-  larger target boiling corrections
-  zeroth-order model deficiencies (bin centering, radiative corrections)

## Measuring the EMC Effect at Large x

- For x>0.6, E03-103 data at W<4 GeV (resonance region)
- Recent data from JLab suggests that even in the resonance region inclusive cross sections scale
- Earlier Hall C data taken at 4 GeV, sees no apparent deviation (at the 10% level) from scaling for W2>2 GeV2 (for Q2 > 3 GeV2)

- E89008 – 4 GeV

## EMC Measurements at W<2 GeV

- EMC ratio extracted using resonance region data from E89-008
- 1.2<W2<3.0 GeV2 at
-     Q2≈4 GeV2
- Where there is overlap, JLab resonance data agrees well with SLAC (DIS) results
- E03-103 has data at W2>2 GeV2 at Q2=6 GeV2 (x=0.82)
- Data at smaller angles will allow us to put quantitative limits on deviation from scaling in the cross sections AND ratios

## Summary

- Study of the EMC effect in light nuclei will help us more cleanly separate “conventional nuclear physics” contributions to the cross section ratios from more exotic explanations
- JLab E03-103 will increase the precision of 4He ratios, and be the first precise measurement for 3He at x>0.4
- Observation of cross section scaling in deuterium for W2>2 GeV2 and agreement of “resonance region EMC ratio” with DIS results gives us confidence that we will be able to extract precise ratios up to x~0.85
- Stay tuned – final results soon

## E03-103 Collaboration

- J. Arrington (spokesperson), L. El Fassi, K. Hafidi, R. Holt,
- D.H. Potterveld, P.E. Reimer, E. Schulte, X. Zheng
*Argonne National Laboratory, Argonne, IL*
- B. Boillat, J. Jourdan, M. Kotulla, T. Mertens, D. Rohe, G. Testa,
- R. Trojer
*Basel University, Basel, Switzerland*
- B. Filippone
*California Institute of Technology, Pasadena, CA*
- C. Perdrisat
*College of William and Mary, Williamsburg, VA*
- D. Dutta, H. Gao, X. Qian
*Duke University, Durham, NC*
- W. Boeglin
*Florida International University, Miami, FL*
- M.E. Christy, C.E. Keppel, S. Malace, E. Segbefia, L. Tang,
-  V. Tvaskis, L. Yuan
*Hampton University, Hampton, VA*
- G. Niculescu, I. Niculescu
*James Madison University, Harrisonburg, VA*
- P. Bosted, A. Bruell, V. Dharmawardane, R. Ent, H. Fenker,
-  D. Gaskell (spokesperson),  M.K. Jones, A.F. Lung, D.G. Meekins, J. Roche, G. Smith, W.F. Vulcan, S.A. Wood
*Jefferson Laboratory, Newport News, VA*

- B. Clasie, **J. Seely**
*Massachusetts Institute of Technology, Cambridge, MA*
- J. Dunne
*Mississippi State University, Jackson, MS*
- V. Punjabi
*Norfolk State University, Norfolk, VA*
- A.K. Opper
*Ohio University, Athens, OH*
- H. Nomura
*Tohoku University, Sendai, Japan*
- M. Bukhari, **A. Daniel**, N. Kalantarians, Y. Okayasu, V. Rodriguez
*University of Houston, Houston, TX*
- F. Benmokhtar, T. Horn
*University of Maryland, College Park, MD*
- D. Day, N. Fomin, C. Hill, R. Lindgren, P. McKee, O. Rondon,
- K. Slifer, S. Tajima, F. Wesselmann, J. Wright
*University of Virginia, Charlottesville, VA*
- R. Asaturyan, H. Mkrtchyan, T. Navasardyan, V. Tadevosyan
*Yerevan Physics Institute, Armenia*
- S. Connell, M. Dalton, C. Gray
*University of the Witwatersrand, Johannesburg, South Africa*