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Measurement of R = sigma_L / sigma_T and the Separated Longitudinal and Transverse Structure Functions in the Nucleon Resonance Region

The Jefferson Lab Hall C E94-110 Collaboration, :, Y. Liang, V. Tvaskis, M. E. Christy, A. Ahmidouch, C. S. Armstrong, J. Arrington, R. Asaturyan, S. Avery, O. K. Baker, D. H. Beck, H. P. Blok, C. W. Bochna, W. Boeglin, P. Bosted, M. Bouwhuis, H. Breuer, D. S. Brown, A. Bruell, R. D. Carlini, J. Cha, N. S. Chant, A. Cochran, L. Cole, S. Danagoulian, D. B. Day, J. Dunne, D. Dutta, R. Ent, H. C. Fenker, B. Fox, L. Gan, H. Gao, K. Garrow, D. Gaskell, A. Gasparian, D. F. Geesaman, R. Gilman, P. L. J. Gu`eye, M. Harvey, R. J. Holt, X. Jiang, M. Jones, C. E. Keppel, E. Kinney, W. Lorenzon, A. Lung, D. J. Mack, P. Markowitz, J. W. Martin, K. McIlhany, D. McKee, D. Meekins, M. A. Miller, R. G. Milner, J. H. Mitchell, H. Mkrtchyan, B. A. Mueller, A. Nathan, G. Niculescu, I. Niculescu, T. G. O'Neill, V. Papavassiliou, S. F. Pate, R. B. Piercey, D. Potterveld, R. D. Ransome, J. Reinhold, E. Rollinde, O. Rondon, P. Roos, A. J. Sarty, R. Sawafta, E. C. Schulte, E. Segbefia, C. Smith, S. Stepanyan, S. Strauch, V. Tadevosyan, L. Tang, R. Tieulent, A. Uzzle, W. F. Vulcan, S. A. Wood, F. Xiong, L. Yuan, M. Zeier, B. Zihlmann, V. Ziskin

Abstract

We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q^2 < 5.5 GeV^2. The data have been used to accurately perform 167 Rosenbluth-type longitudinal / transverse separations. The precision R = sigma_L / sigma_T data are presented here, along with the first separate values of the inelastic structure functions F_1 and F_L in this regime. The resonance longitudinal component is found to be significant, both in magnitude and in the existence of defined mass peaks. Additionally, quark-hadron duality is here observed above Q^2 = 1 GeV^2 in the separated structure functions independently.

Measurement of R = sigma_L / sigma_T and the Separated Longitudinal and Transverse Structure Functions in the Nucleon Resonance Region

Abstract

We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q^2 < 5.5 GeV^2. The data have been used to accurately perform 167 Rosenbluth-type longitudinal / transverse separations. The precision R = sigma_L / sigma_T data are presented here, along with the first separate values of the inelastic structure functions F_1 and F_L in this regime. The resonance longitudinal component is found to be significant, both in magnitude and in the existence of defined mass peaks. Additionally, quark-hadron duality is here observed above Q^2 = 1 GeV^2 in the separated structure functions independently.

Paper Structure

This paper contains 2 equations, 3 figures.

Figures (3)

  • Figure 1: Representative Rosenbluth plots for the kinematics indicated.
  • Figure 2: Measurements of $R=\sigma_L/\sigma_T$, as a function of $W^2$, for the $Q^2$ values indicated. The error bars shown represent both the statistical and uncorrelated systematic uncertainties, with the former negligible in comparison to the latter. The shaded band below the offset zero represents the total scale uncertainty. The locations of the three prominent resonances observed in the unseparated cross section measurements are labeled at the top.
  • Figure 3: The longitudinal structure function $F_L$ (top), and transverse nucleon structure function $2xF_1$ (bottom), measured in the resonance region (triangles) as a function of $x$, compared with existing DIS measurements from SLAC (diamonds). The curves are from MAID (bottom middle, dot-dashed), Alekhin (dashed), and MRST with (solid) and without (dotted) target mass effects included. The three prominent resonance mass regions observed in the inclusive cross section are indicated by arrows, and labeled in the top plots. The error bars shown represent both the statistical and systematic uncertainties, with the latter being dominant.