Impact of nuclear dependence ofR=σL/σTon antishadowing in nuclear structure functions

Abstract

We study the impact of the nuclear dependence of R = σL/σT on the extraction of the F A 2 /F D 2 and F A 1 /F D 1 structure function ratios from the data on the σ A /σ D cross section ratios. Guided by indications of the nuclear dependence of R from the world data, we examine selected sets of EMC, BCDMS, NMC and SLAC data and find thatIn particular, we observe that the nuclear enhancement (antishadowing) for F A 1 /F D 1 in the interval 0.1 < x < 0.3 becomes significantly reduced or even disappears, which indicates that antishadowing is dominated by the longitudinal structure function FL. We also argue that precise measurements of nuclear modifications of R and F A L have the potential to constrain the poorly known gluon distribution in nuclei over a wide range of x.

Recent Developments in Neutrino/Antineutrino-Nucleus Interactions

“…Should subsequent experimental results confirm the rather substantial difference between chargedlepton and neutrino scattering in the shadowing region at low-Q 2 it is interesting to speculate on the possible cause of the difference. A recent study of EMC, BCDMS and NMC data by a Hampton University -Jefferson Laboratory collaboration [125] suggests that anti-shadowing in charged-lepton nucleus scattering may be dominated by the longitudinal structure function F L . As a by-product of this study, their figures hint that shadowing in the data of EMC, BCDMS and NMC µ A scattering was being led by the transverse cross section with the longitudinal component crossing over into the shadowing region at lower x compared to the transverse.…”

Nuclear shadowing in electro-weak interactions

“…Should subsequent experimental results confirm the difference between charged-lepton and neutrino scattering in the shadowing region at low-Q 2 , it is interesting to speculate on the possible cause of the difference. A recent study of EMC, BCDMS and NMC data by a Hampton University -Jefferson Laboratory collaboration [241] suggests that anti-shadowing in charged-lepton nucleus scattering may be dominated by the longitudinal structure function F L . As a by-product of this study, their figures hint that shadowing in the data of EMC, BCDMS and NMC µ A scattering was being led by the transverse cross section with the longitudinal component crossing over into the shadowing region at lower x compared to the transverse.…”

The challenge of the EMC effect: Existing data and future directions

“…It has been demonstrated, 113 however, that the precision of the existing data for R A − R D is not sufficient to rule out a nuclear dependence that could result in, for example, the small enhancement of the nuclear ratios in the anti-shadowing region being absent for the ratio of F 1 structure functions and manifesting only in the ratio F A 2 /F D 2 . Since F 1 contains contributions only from transverse virtual photons, while F 2 contains contributions from both transverse and longitudinal photons, such a non-zero R A − R D implies that anti-shadowing may be a manifestation of a modification of σ L only, i.e., not necessarily due to modifications of the quark distributions.…”