Non-leading corrections to the Drell-Yan cross section at small transverse momentum

The production of Drell-Yan lepton pairs at small transverse momentum is analyzed to second order in QCD perturbation theory. By calculating exactly all terms involving powers of the large logarithm ln $\text{(}\text{Q}{}^2\text{q}{}_{\mathrm{<mtext>T</mtext>}}{}^2$), we are able to confront the predictions of “soft gluon” cross sections in which these logarithms are summed to all orders. Our results confirm the factorization properties of these cross sections, and yield new information on previously undetermined coefficients.     

Photoproduction of the omega meson on the proton at large momentum transfer

The differential cross section, dsigma/dt, for omega meson exclusive photoproduction on the proton above the resonance region (2.6相似文献   

截面依赖动量转移条件下屏蔽效应的理论研究

利用BBK模型及修正方案, 对电子入射电离氦原子(e,2e)反应过程中截面依赖动量转移条件下的三重微分散射截面(TDCS)进行了理论计算, 把计算结果与实验测量结果进行比较, 分析了截面结构, 并研究了末通道屏蔽效应对三重微分截面所产生的影响.     

Absolute electron-proton cross sections at low momentum transfer measured with a high pressure gas target system

Absolute differential cross sections for elastic electron-proton scattering have been measured in a four-momentum transfer range up to 1.4 fm^?2. Using a high pressure gas target system, we have obtained highly accurate data with a small normalization error of 0.5%. The electromagnetic form factors G_E and G_M have been extracted and the rms charge radius has been determined to be $\text{〈r}{}^2{}_{\mathrm{<mtext>E</mtext>}}\text{〉}{}_{\mathrm{<mtext>p</mtext>}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.862±0.012}\text{fm}$. The shape of the isovector spectral function near threshold shows a significant non-resonant contribution of the two-pion state. This enhancement is so strong that the derivative at q² = 0 differs considerably from the usual vector meson dominance model value. This result is in good agreement with theoretical predictions.     

Deuteron electrodisintegration at high energy and momentum transfer

Inelastic electron-deuteron scattering has been calculated at backward angles for energy transfers up to 50 MeV and momentum transfers up to 60 fm^?2. Exchange currents from the pion, vector mesons and mixed ?πγ and ωπγ were taken into account. The effect of the meson-nucleon form factor is studied, and various approximations of the mesonic currents are discussed. Baryon resonance configurations in the wave function have been used to calculate the Δ-resonance currents. We show that the effect from meson-nucleon form factors, the ?πγ, ωπγ and Δ currents cancels almost exactly against the vector meson contribution at low momentum transfer. Thus the pure pionic current defines a reasonable choice. In the high momentum region this approximation breaks down.     

Deuteron electrodisintegration near threshold at high momentum transfer

In view of recent experimental results on d(e, é)np near the break-up threshold at high momentum transfer various theoretical calculations of exchange effects giving different answers are analysed. It is shown that a gauge-invariant choice of electromagnetic nucleon form factors is crucial. Furthermore, the contradictive rôle of ρ-exchange, the potential dependence and MEC involving Δ-isobar configurations is investigated. The latter are shown to be as important as the isobar currents at high momentum transfer.     

Total photoproduction cross section at very high energy

In this paper we apply to the photoproduction total cross section a model we have proposed for purely hadronic processes and which is based on QCD mini-jets and soft gluon re-summation. We compare the predictions of our model with the HERA data as well as with other models. For cosmic rays, our model predicts substantially higher cross sections at TeV energies than models based on factorization, but lower than models based on mini-jets alone, without soft gluons. We discuss the origin of this difference.     

Proton-nucleus inelastic cross section at ultra high energy

Energy dependence of proton-nucleus reaction cross section at very high energy is discussed. It is stressed that depending on the gluon distribution near the nuclear surface, proton-nucleous total cross section increases much more rapidly compared to the usual Glauber independent nucleon estimate. The recent observation of smaller X _max than the expected value at UHECR domain can be an indication for such a mechanism.     

Determining the inelastic proton–proton cross section at the large hadron collider using minimum bias events

In this paper a new method is described for determining the non-diffractive part of the inelastic proton–proton cross section, at the LHC centre of mass energy of 14 TeV. The method is based on counting the number of inelastic proton–proton interactions in the collision regions. According to a preliminary investigation, this measurement will be best suited for the initial low luminosity phase of the LHC. Knowledge of the proton–proton luminosity is likely to dominate the measurement uncertainty. PACS 13.85.Hd     

Photoproduction of straight phi(1020) mesons on the proton at large momentum transfer

The cross section for straight phi meson photoproduction on the proton has been measured for the first time up to a four-momentum transfer -t = 4 GeV2, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. At low four-momentum transfer, the differential cross section is well described by Pomeron exchange. At large four-momentum transfer, above -t = 1.8 GeV2, the data support a model where the Pomeron is resolved into its simplest component, two gluons, which may couple to any quark in the proton and in the straight phi.     

Rise of proton proton total cross section and inclusive spectra

The origin of the rise of p-p total cross section (σ_t(pp)) is investigated by making use of the inclusive sum rule. The contribution to the rise of σ_t(pp) from the development of sharp peak near the kinematical boundary in the process p+p→p+ “anything” is almost completely canceled out by the decrease of the cross section in other x-region between s=45 (GeV/c)² and s=2820 (GeV/c)². Then the net contribution to the rise of σ_t(pp) from the process p+p→p+ “anything” is very likely to be zero. The true origin of the rise of σ_t(pp) is found to be the increase of inclusive cross sections at x ? 0 between PS and ISR energies. The contribution from the process p+p→π+ “anything” at x ? 0 to the rise of σ_t(pp) is estimated to be 3.2 mb, that from the process p+p→K + “anything”, 0.71 mb and that from the process p+p→$\text{p}$ “anything”, 0.62 mb. According to our conclusion we expect that all total cross sections will rise with energy at high energy.     

Some comments on the total γγ → hadron cross section at high energy

For the γγ→h total cross section we suggest approximations for the Q² dependence and the energy dependence, which are better founded than those applied nowadays. This considerably changes the results obtained in PETRA and thier relation to the Regge-pole model.     

Differential production cross section of Z bosons as a function of transverse momentum at sqrt

We present a measurement of the transverse momentum distribution of Z bosons produced in p&pmacr; collisions at sqrt[s] = 1.8 TeV from data collected by the DO experiment at the Fermilab Tevatron Collider. We find good agreement between our results and current resummation calculations, and also use our data to extract nonperturbative parameters for a particular version of the resummation formalism. The resulting values are significantly more precise than obtained in previous determinations.     

Nucleon form factors for elastic electron-deuteron scattering at high momentum transfer

Elastic electron-deuteron scattering at high momentum transfer is investigated within the Bethe-Salpeter approach. The relativistic covariant Graz II separable kernel of nucleon-nucleon interactions is used to analyze the deuteron structure functions, form factors, and tensor of polarization components. The modern data for the electromagnetic structure of nucleons from the double polarization experiments, as well as some other models of the nucleon form factors, are considered.