Xe/D sub 2 cross-section ratios at low X sub Bj from muon scattering at 490 GeV/c Page: 5 of 6

                                
4

4 Corrections and Systematic Errors
The data have been corrected for target acceptance, reconstruction efficiency of the scattered muon,
empty target subtraction, and radiative events (unless the electromagnetic calorimeter was used to
cut these events). Radiative corrections represent the largest correction to the raw ratio (- 25% at
auf = 0.001). Using the electromagnetic calorimeter, EBBS has been able to compare the results
of radiative corrections from the two methods mentioned above, showing that they are consistent
within statistical errors. The following table shows current estimates of the systematic errors due
to the above corrections as well as from beam normalization and target density.
Summary of Systematic Errors
Source         Estimate   Source          Estimate    Source          Estimate
Beam Norm.     0.7 %      Trigger Acc.    2.8 %      MT Target Sub. 1.0 9
Target Density  0.4 %     Radiative Corr. 1.4 %      i Recon.         4.0 %
5    Results
Figure 5 shows the ratio Oxa/aDZ as a function of aBJ. The data show that the cross-section per
1.2
1.1            *  E665 r,./
A   NA28 F0''/F+
0.9                                                                    I
0.8
0.7
0.6      -    Real v scattering from xenon at xq  0
0.5
10-3                               10-Z                               10-'
Figure 5: ETA/ffDs Vs flj
nucleon for muon scattering on Xe is suppressed relative to that for D2 in the region 0.001 < aB <
0.1. This phenomena, called "shadowing", has been seen in 7 - nucleus scattering at high energies
[4] as well as in virtual photon scattering at low and high energies (5,6]. Recently, CERN experiment
NA28 [61 has made measurements on carbon and calcium nuclei in much the same kinematic region
as in this analysis. In Figure 5, data from E665 xenon and NA28 calcium are shown with statistical
error bars only, indicating agreement between the two results in the shadowing region, and showing
that E665 extends the kinematical range studied by NA28. Note that the data are consistent with
an estimated real photon point (0.6 for xenon for A'/' = 1310-) [4].
In Figure 6, the Q2 variation of Oxt/UDZ for two aBj regions is presented with a comparison of
NA28 calcium data. Once again, only statistical error bars are shown. The E665 data significantly
extend the Q2 range, and show that there is no Q2 dependence of the eX. /0n2 ratio. This behavior
indicates that the shadowing phenomenon observed is not consistent with naive vector dominance,
but rather witli models which predict shadowing as a result of parton recozzbination in heavy nuclei
at low 2Bj [7] or with genertdized vector dominance models [8].