We report new results on a precision measurement of the ratio R=σLσT and the structure function F2 for deep-inelastic electron-nucleon scattering in the kinematic range 0.2≤x≤0.5 and 1≤Q2≤10 (GeV/c)2. Our results show, for the first time, a clear falloff of R with increasing Q2. Our R and F2 results are in good agreement with QCD predictions only when corrections for target-mass effects are included.
2.6 pct rad length target.
2.6 pct rad length target.
2.6 pct rad length target.
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Cross sections for deep-inelastic electron scattering from liquid deuterium, gaseous He4, and solid Be, C, Al, Ca, Fe, Ag, and Au targets were measured at the Stanford Linear Accelerator Center using electrons with energies ranging from 8 to 24.5 GeV. These data cover a range in the Bjorken variable x from 0.089 to 0.8, and in momentum transfer Q2 from 2 to 15 (GeV/c)2. The ratios of cross sections per nucleon (σAσd)is for isoscalar nuclei have been extracted from the data. These ratios are greater than unity in the range 0.1<x<0.3, while for 0.3<x<0.8 they are less than unity and decrease logarithmically with atomic weight A, or linearly with average nuclear density. No Q2 dependence in the ratios was observed over the kinematic range of the data. These results are compared to various theoretical predictions.
Additional overall systematic error of 2.1 pct plus a target to target systematic error of 1 pct.
Additional overall systematic error of 2.1 pct plus a target to target systematic error of 2.1 pct.
Additional overall systematic error of 2.1 pct plus a target to target systematic error of 0.6 pct.
This paper presents our first measurement of the F 2 structure function in neutral-current, deep inelastic scattering using the ZEUS detector at HERA, the ep colliding beam facility at DESY. The data correspond to an integrated luminosity of 24.7 nb −1 . Results are presented for data in range of Q 2 from 10 GeV 2 to 4700 GeV 2 and Bjorken x down to 3.0 × 10 −4 . The F 2 structure function increases rapidly as x decreases.
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We report results on a precision measurement of the ratio R=σLσT in deep inelastic electron-nucleon scattering in the kinematic range 0.2≤x≤0.5 and 1≤Q2≤10 (GeV/c)2. Our results show, for the first time, a clear falloff of R with increasing Q2. Our R results are in agreement with QCD predictions only when corrections for target mass effects and some additional higher twist effects are included. At small x, the data on R favor structure functions with a large gluon contribution. We also report results on the differences RA−RD and the cross section ratio σAσD between Fe and Au nuclei and the deuteron. Our results for RA−RD are consistent with zero for all x, Q2 indicating that possible contributions to R from nuclear higher twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The ratios σAσD from all recent experiments, at all x, Q2 values, are now in agreement.
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The ZEUS detector has been used to measure the proton structure functionF2. During 1993 HERA collided 26.7 GeV electrons on 820 GeV protons. The data sample corresponds to an integrated luminosity of 0.54 pb−1, representing a twenty fold increase in statistics compared to that of 1992. Results are presented for 7<Q2<104 GeV2 andx values as low as 3×10−4. The rapid rise inF2 asx decreases observed previously is now studied in greater detail and persists forQ2 values up to 500 GeV2.
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The gluon momentum density xg ( x , Q 2 ) of the proton was extracted at Q 2 = 20 GeV 2 for small values of x between 4 × 10 −4 and 10 −2 from the scaling violations of the proton structure function F 2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F 2 at low x constrained by measurementsfrom NMC at larger x ; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x .
Values of F2 and slope of F2 obtained from fits to the ZEUS paper used in the extraction of the gluon momentum distributions.
Gluon momenta distribution at Q**2 = 20.
The inclusive A(e,e') cross section for $x \simeq 1$ was measured on $~2$H, C, Fe, and Au for momentum transfers $Q~2$ from 1-7 (GeV/c)$~2$. The scaling behavior of the data was examined in the region of transition from y-scaling to x-scaling. Throughout this transitional region, the data exhibit $\xi$-scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.
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This paper presents an analysis of the inclusive properties of diffractive deep inelastic scattering events produced in $ep$ interactions at HERA. The events are characterised by a rapidity gap between the outgoing proton system and the remaining hadronic system. Inclusive distributions are presented and compared with Monte Carlo models for diffractive processes. The data are consistent with models where the pomeron structure function has a hard and a soft contribution. The diffractive structure function is measured as a function of $\xpom$, the momentum fraction lost by the proton, of $\beta$, the momentum fraction of the struck quark with respect to $\xpom$, and of $Q~2$. The $\xpom$ dependence is consistent with the form \xpoma where $a=1.30\pm0.08(stat)~{+0.08}_{-0.14}(sys)$ in all bins of $\beta$ and $Q~2$. In the measured $Q~2$ range, the diffractive structure function approximately scales with $Q~2$ at fixed $\beta$. In an Ingelman-Schlein type model, where commonly used pomeron flux factor normalisations are assumed, it is found that the quarks within the pomeron do not saturate the momentum sum rule.
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We report on a measurement of the proton structure function $F_2$ in the range $3.5\times10~{-5}\leq x \leq 4\times10~{-3}$ and 1.5 ${\rm GeV~2} \leq Q~2 \leq15$ ${\rm GeV~2}$ at the $ep$ collider HERA operating at a centre-of-mass energy of $\sqrt{s} = 300$ ${\rm GeV}$. The rise of $F_2$ with decreasing $x$ observed in the previous HERA measurements persists in this lower $x$ and $Q~2$ range. The $Q~2$ evolution of $F_2$, even at the lowest $Q~2$ and $x$ measured, is consistent with perturbative QCD.
Data from shifted vertex analysis. Overall normalization error of 3% is notincluded.
Data from shifted vertex analysis. Overall normalization error of 3% is notincluded.
Data from shifted vertex analysis. Overall normalization error of 3% is notincluded.
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