Forward-backward correlations in pp interactions in a dual model

Forward-backward correlations in lepton and hadron induced processes are compared according to the dual model. It is indicated that the effect of the chain energy spread in hadron processes is important. After including this effect the model is shown to explain the forward-backward correlations in pp data assuming no dynamical correlations within a single chain.     

Deep inelastic scattering from the nuclear medium

We reexamine deep inelastic scattering from nuclei under assumptions commonly employed in the literature: that quarks remain confined in hadronic constituents of nuclei, that the nuclear cross section is the average of the free-space cross section of hadron i weighted by the probability of finding i in the nucleus, and that there are no final state interactions between the debris of hadron i and the rest of the nucleus. We develop a cluster expansion for the cross section of deep inelastic lepton scattering and the Drell-Yan process on nuclei. Using the “instant” from of dynamics, we find that large contributions to these processes arise from nuclear interactions and correlations. However, our theory differs in detail from other approaches, and we find that binding alone is unlikely to explain the EMC effect. Also, in contrast to many recent papers on the subject, we conclude that the contribution of pions (and other nonnucleonic consistuents of the nucleus) is strongly suppressed.     

Problems of Deep Inelastic Lepton-Nucleus Interaction

The deep inelastic scattering of electrons (muons) and neutrinos on the nuclei and the process of lepton pair production in hadron-nucleus collisions are considered. The expressions for the corresponding differential cross-sections are derived provided the final lepton and the spectator fragment of the initial nucleus are detected in coincidence. The structure functions of the processes under consideration are analysed by the principle of automodelity. Some scale-invariant regularities are established for them. In the framework of “light front” formalism for many-body systems the relations of these structure functions to the usual structure functions of the deep inelastic lepton hadron interaction are obtained. A hypothesis is put forward on the scale invariance of structure functions with respect to the ξ-variable which is some complicated dimensionless combination of kinematic invariants.     

New experimental and simulated results on nuclear media effects in meson photoproduction off nuclei

New experimental approach to study meson photoproduction in nuclei is discussed. It is based on the measurement of the recoil nucleon as a tagger for identification of the initial step of reaction. Propagation of mesons and nucleons within a nucleus is described by the Intra-Nuclear Cascade (INC) model. Simulations and preliminary experimental data for the deuteron target obtained at GRAAL are presented.     

巨共振激发的相对论效应

在相对论量子场论(QHD)的框架下,得到了相对论线性Vlasov方程.基此计算了球形核¹⁶O、⁴⁰Ca、⁹⁰Zr及²⁰⁸Pb的巨偶极共振的强度函数分布.计算得到的巨共振中心能量,与实验结果比较有较好的符合.对计算结果作了简要的讨论,发现核子有效质量m^*和平均场自旋轨道耦合力对巨共振能量有着重要的效应.     

Nucleon momentum distribution of ~(56)Fe from the axially deformed relativistic mean-field model with nucleon-nucleon correlations

Nucleon momentum distribution(NMD), particularly its high-momentum components, is essential for understanding the nucleonnucleon(NN) correlations in nuclei. Herein, we develop the studies of NMD of ~(56)Fe from the axially deformed relativistic mean-field(RMF) model. Moreover, we introduce the effects of NN correlation into the RMF model from phenomenological models basing on deuteron and nuclear matter. For the region k k_F, the effects of deformation on the NMD of the RMF model are investigated using the total and single-particle NMDs. For the region k k_F, the high-momentum components of the RMF model are modified by the effects of NN correlation, which agree with the experimental data. Comparing the NMD of relativistic and non-relativistic mean-field models, the relativistic effects on nuclear structures in momentum space are analyzed. Finally, by analogizing the tensor correlations in deuteron and Jastrow-type correlations in nuclear matter, the behaviors and contributions of NN correlations in ~(56)Fe are further analyzed, which helps clarify the effects of the tensor force on the NMD of heavy nuclei.     

Excitation of states of medium-mass nuclei in the region of giant resonances in inelastic deuteron scattering

Results are presented that were obtained by measuring a continuum in the inelastic scattering of 37-MeV deuterons on ¹²C, ⁴⁸Ti, and ^58,64Ni nuclei in the angular range 16° ≤ θ ≤ 61°. Broad excitation maxima are found for deuteron scattering angles in the range θ ≤ 21°. The region of a broad maximum includes giant resonances of target nuclei, whose levels are excited quite readily at E _d = 37 MeV. Summation of the inelastic-scattering cross sections over all final states of the excited| nucleus and the use of completeness of the wave functions for these states make it possible to express the total cross section for inelastic (incoherent) deuteron scattering only in terms of the wave functions for the ground state of the target nucleus. The corresponding quasielastic-scattering amplitude is taken in the diffraction approximation. Nucleon correlations in the target nucleus are disregarded. Upon disregarding a small contribution of multiple quasielastic scattering at small scattering angles, the cross section for incoherent deuteron scattering is represented approximately as the product of known factors—the square of the absolute value of the amplitude for diffractive quasielastic scattering and the effective number of target nucleons scattering deuterons. The results of these calculations agree qualitatively with experimental data.     

Detector Effects on the Response of a Highly Granular Hadron Calorimeter to Single Hadrons

In the detectors currently being developed for experiments on the next-generation lepton colliders, highly granular calorimeters are to be used. In particular, the hadron calorimeter is planned to be assembled from scintillation cells with direct readout of light by silicon photomultipliers. According to the results of experimental measurements of the light collection in a cell developed for the CALICE prototype hadron calorimeter, when detecting minimum ionizing particles, an estimate of the detector effects was obtained. The detector effect on the resolution of the ILD hadron calorimeter was studied by modeling the response of the detector to single neutral kaons. It was shown that the contribution of experimentally measured detector effects to the resolution for single particles is on the order of 0.5–1% in the range of hadron energy of 5–60 GeV.     

Photon + hadron production in high energy deuteron (proton)–nucleus collisions

We apply the color glass condensate formalism to photon + hadron production cross section in high energy deuteron (proton)–gold collisions at RHIC. We investigate the dependence of the production cross section on the angle between the produced hadron and photon for various rapidities and transverse momenta. It is shown that the angular correlation between the produced hadron and photon is a sensitive probe of the saturation dynamics.     

Relativistic approaches to investigation of few-nucleon systems

Theoretical approaches used in investigation of relativistic effects in high energy lepton and hadron collisions with few-nucleon systems are analyzed. The Bethe-Salpeter formalism for describing interacting systems of two spinor particles both in the continuum and bound state is described in detail. Special attention is paid to partial expansions, taking into account the analytic properties of Bethe-Salpeter amplitudes and unitary transformations correlating different representations of partial amplitudes. Mathematical methods of numerical solution of equations are considered. Results of calculation of relativistic corrections and effects of interaction in the final state in particular reactions with participation of the deuteron, namely, in elastic pD backward scattering and in reactions of deuteron break-up with production of correlated pairs, are presented.     

能量损失效应引起的核Drell-Yan微分截面比的压低

核环境中夸克的能量损失可以通过高能核Drell-Yan过程的核依赖进行测量. 利用文献中给出的夸克能量损失公式和从轻子－原子核深度非弹性散射实验数 据得到的束缚核子中的部分子分布函数, 计算了FNAL E772 800GeV的质子打击不同原子核的Drell-Yan过程截面比, 发现考虑能量损失的计算结果与FNAL E772实验数据符合甚好. 建议在利用核Drell-Yan过程实验数据抽取束缚核子内部分子分布函数时应该考虑能量损失效应.     

Two-photon collisions in deep inelastic lepton-nucleon and lepton-nucleus scattering

We have calculated the μ-pair production via photon-photon collisions in deep-inelastic charged lepton scattering on proton and nuclei, using the equivalent photon approximation. Specific parametrizations were assumed for the proton and the nuclei form factors and the QED photon structure function. Results are given for lepton energies below 300 GeV and virtual photon massesQ ² less than 50 GeV², as functions of the μ-pair mass, the scaling variablex and the electric chargeZ of the hadron target. Using a photon structure function derived from QPM and VDM we also estimate the contribution of γγ collisions to hadron production in these deep inelastic processes.     

Evidence for multiple parton interactions from the observation of multi-muon events in Drell-Yan experiments

We calculate the production of two lepton pairs via the Drell-Yan mechanism. To establish the existence of multiple parton interactions in a single hadron collision, lepton pair production is superior to jet production from the theoretical, phenomenological and experimental points of view. The calculated rate agrees with the previously unexplained four-muon events observed in πp and pp interactions. Our results lend support to a recent analysis of ISR four-jet events and we discuss some implications of this study.     

Elastic hadron scattering on Li isotopes at intermediate energies

The elastic scattering of hadrons (protons, charged pions, and positively charged kaons) on ^6,7,8Li nuclei is analyzed on the basis of Glauber-Sitenko diffraction theory. A few nuclear-wave-function versions found within two-and three-particle potential cluster models are used in the calculations. It is shown that the application of these wave functions in diffraction theory makes it possible to describe adequately the experimental differential cross sections and analyzing powers in hadron scattering at intermediate energies. In this study, particular attention is given to a comparison of the scattering of different particles on the same target nucleus, as well as to a comparison of scattering of particles of the same sort on different target nuclei.     

Possible interpretation of the „anomalous“ behaviour of the proton spectrum at 0° from the deuteron fragmentation at 9 GeV/c

The momentum spectra of protons, produced at 0° as a result of fragmentation of relativistic deuterons on nuclei, are analyzed. Possible causes of the existing discrepancy of the data on the 0° proton spectrum from the¹ H(d,p)X reaction at 9.1 GeV/c with results of the impulse approximation calculations are considered. It is shown that taking into account the finite angular resolution of the experimental setup and the corresponding renormalization of the experimental data, on the one hand, and also the inclusion of the additional (to stripping) contribution of protons from the scattering of deuteron nucleons by target protons, on the other, make it possible to match these data with the results of calculations within the framework of the relativistic impulse approximation using the deuteron wave function for the Paris potential.     

Review of Deep Inelastic Charged Lepton Scattering

The present situation in deep inelastic lepton-nucleon scattering is reviewed from an experimenter's point of view. After describing, in some detail, the quark-parton model (QPM) predictions the basic ideas of Quantum Chromodynamics (QCD) are illustrated. The perturbative QCD predictions for deep inelastic scattering are summarised discussing also their theoretical uncertainties of today. Past and present experiments on deep inelastic electron and muon scattering are compared regarding their ability to test these predictions. It is shown that all data is in very good agreement with the QPM and fully consistent with perturbative QCD. New results on lepton scattering off nuclei are discussed and confronted to recently invented phenomenological models.     

TWO TEMPERATURES EMISSION OF RELATIVISTIC α-PARTICLES IN HIGH-ENERGY HEAVY-ION COLLISIONS

We have performed an experimental study of the α-fragments emitted from collisions between emulsion nuclei and heavy-ion projectiles at beam energies beyond 1A GeV. It is shown that the transverse momentum distributions of relativistic α-particles give evidence for two effective temperatures emission in high-energy heavy-ion collisions. The data might take on a new signature for the phase transition from hadron matter to quark matter.     

Point-like configurations in hadrons and nuclei and deep inelastic reactions with leptons: EMC and EMC-like effects

We estimate the suppression of point-like configurations in bound nucleons which can well explain the EMC effect at x>0.3, leads to small ( 1–3%) nucleon swelling, small ( 3%) non-nucleon components in the nucleus wave function, noticeably increases the magnetic moment of the deuteron. Several feasible experiments for probing point-like configurations in hadrons in hA collisions with the Drell-Yan lepton pair trigger are suggested. It is also demonstrated that the Drell-Yan pair production processes provide an effective way of measuring the superfast quark distribution up to x 2.     

Intrinsic transverse momentum and structure function evolution in deep inelastic lepton hadron scattering

A model is constructed that allows to implement intrinsic transverse momentum and target mass in the QCD analysis ofQ ²-evolution of structure functions in deep inelastic lepton hadron scattering without losing the factorization property of mass singularities. The modified evolution equations are integrated numerically and the results are compared to experimental data. It turns out that no further higher twist contributions are required.     

Deuteron production and space-time characteristics of high-energy hadron-nucleus reactions

The contribution of the coalescence mechanism to deuteron production is discussed on the basis of data on inclusive deuteron and proton production in hadron-nucleus interactions. The angular dependence and theA dependence of the coefficient of twonucleon coalescence into a deuteron are analysed for 7.5 GeV/c pA and 5 GeV/cπ ^? A interactions. The results suggest an elongated shape of the interaction region along the trajectory of the incident hadron and a successive knock-out of nucleons during propagation of the incident particle through a nucleus.