The intermediate weak boson and weak interactions at high energy

The high-energy pire-leptonic weak interaction is investigated based on the assumption of the existence of a charged vector boson which mediates the weak processes. With the aid of the fixed-t dispersion relation the following relation is obtained: The weak boson mass m_W should satisfy $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{? G}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, with G the Fermi coupling constant, if the asymptotic value of the cross section becomes of the order of the strong interaction in the energy region observable in cosmic rays, etc.The scattering processes $\text{e}\text{+ν→}\text{e}\text{+ν}\text{and}\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ are examined by the aid of the N/D method. For a large vector-boson mass $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{?100}\text{GeV}$, an S-wave resonance should exist for the process e+ν→e+ν while for $\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ there should exist a P-wave resonance which corresponds to the intermediate weak boson. The neutral current is then estimated. It is shown that the neutral current produced as a higher-order effect is not inconsistent with the present experiments on the pure-leptonic weak interaction if m_W?1 TeV.     

Hadron production at supercolliders in the two component dual parton model and the smallx behaviour of the structure functions

Models which contain a semihard component sensitively depend on the smallx region of the structure functions. Within the framework of a two component dual parton model the effect of recently proposed steeper structure functions is investigated. Drastic changes which appear in the bare scattering amplitudes get significantly reduced by unitarization. For presently available energies the semihard component seems still too small to allow for clear cut conclusions about the correctness of the various proposed structure functions. However, the predictions for SSC or LHC energies depend on the choice of the structure function quite decisively, resulting in a substantial uncertainty in the extrapolations. The uncertainty is reduced to a less worrisome level if the consideration is restricted to the strongly shadowed parton distribution.     

Dual parton model and the photoproduction of pseudoscalar and vector mesons in the high energy region

On the basis of the dynamical dual model of strong interactions followed from the parton model of hadrons as discussed in an earlier paper, we study here the photo-production of pseudoscalar and vector mesons in the high energy region. To incorporate the concept of duality, it is taken that any two spin $\text{1}\text{2}$ pointlike constituents (partons) can form a π-meson cluster in the structure of a nucleon and the basic interaction involved in MB scattering is the interaction of the incident meson with the π meson in the structure of the nucleon. In this scheme, the amplitudes for the photoproduction of mesons such as γN → Nπ, γN → N?, and γN → Nω in the high energy region can be related with the amplitudes for the process γπ → ππ, γπ → π?, and γπ → πω, respectively. To calculate the amplitudes for the relevant process we also consider a factor corresponding to the structural rearrangement of partons involved in duality diagrams. To obtain the cross sections, we take into account the photon-vector meson analogy, though the naive form of the vector dominance model (VDM) has not been considered here. From a knowledge of the coupling constants $\text{γ?}{}^2\text{4π}$, $\text{γω}{}^2\text{?π}$, , and we obtain the differential cross sections which are in excellent agreement with experimental results. Also we obtain a good fit for the scattering process γN → Nπ at backward angles. For the vector meson production processes, we have contributions from the diffraction mechanism also apart from the amplitudes considered here. In the region where the contribution from the diffraction part is negligible, we obtain the relation

which is in nice agreement with experiments. Finally, it is shown that, though the vector meson dominance is not considered here, the universality of the vector meson coupling with hadrons follows directly from the present model.     

Single diffractive hadron-nucleus interactions within the dual parton model

Single diffractive hadron-nucleus interactions are studied within the framework of the dual parton model. Introducing a diffractive component into the Monte-Carlo event generator DTUNUC we investigate particle production and the dependence of the diffractive cross section on the atomic number of the target nucleus. A comparison of the numerical results with recent experimental data is presented. We furthermore introduce hadronic cross section fluctuations and discuss their influence on diffractive proton-nucleus cross sections.     

Radiatively generated parton distributions for high energy collisions

The gluon and antiquark distributions of the nucleon are generated radiatively using the assumption that at some low resolution scale the nucleon consists entirely of valence quarks and valence-like gluons. The agreement between the uniquely predicted gluon and sea distributions and the available data on deep inelastic structure functions (including also recent low-Q ² measurements) and direct-photon production is demonstrated and discussed in detail. Simple parametrizations of the resulting (positive definite!) parton distributions are presented in the range 10^?4?x≦1 and 0.2?Q ²?10⁶ GeV² as obtained according to the leading- and higher-order renormalization group evolution equations.     

Dynamically generated parton distributions for high energy collisions

The parton distributions of the nucleon are evaluated dynamically using the assumption that at some low resolution scale the nucleon consists entirely of valence quarks. A simple parametrization of the resulting gluon distribution is presented, forx? 10^?5 up toQ ²?10⁶ GeV². This gluon distribution is predicted dicted to be much steeper and larger in the very smallx region (x<10^?2) than usually assumed. Applications to deep inelastic scaling violations and heavy quark (c, b, t) contribution are discussed and presented as well as hadronic heavy quark production at SSC/LHC energies. For example, the \(b\bar b\) production rate at 40 TeV is predicted to be about an order of magnitude larger than that estimated with other gluon distributions so far.     

Hadron production in proton-proton interactions at medium energies

Hadron production in proton-proton interactions is described in the framework of a collision model, which aims at describing simultaneously all reaction channels in a wide energy region. An empirical matrix element based on the present knowledge of the partonic structure of hadrons is combined with the concept of intermediate subsystems and the calculation of modified statistical weights of the various final states. It is demonstrated that the energy dependence of total cross sections between threshold and about 50 GeV incident energy can be satisfactorily reproduced. This is the basis for considering theoretical and experimental problems ofK ^?, η andη′ production in more detail.     

Hadron production in lepton-nucleus interactions at high energies: Monte carlo generator HARDPING 2.0

Hadron production in lepton-nucleus interactions at high energies is considered in the framework of developing Monte Carlo event generator HARDPING (HARD Probe INteraction Generator). Such effects as formation length, energy loss and multiple rescattering for produced hadrons and their constituents are implemented in the HARDPING 2.0 generator. Available data from HERMES collaboration on hadron production in lepton-nucleus collisions are described by the present version of the HARDPING generator in a reasonable agreement.     

On the free parton model for weak semileptonic decays of charmed particles

It is argued that the fitted charmed quark mass and Fermi momentum in the free parton model for semileptonic decays of charmed particles, are unreasonably large. Furthermore, the charmed quark mass needed to explain the estimated semileptonic width of charmed particles is also too large (～2 GeV). It is reasoned that the failure of the free parton picture is due to strong initial and final state binding effects.     

Probing small parton densities in ultraperipheral A A and pA collisions at the CERN large Hadron Collider

We calculate photoproduction rates for several hard processes in ultraperipheral proton-lead and lead-lead collisions at the CERN Large Hadron Collider (LHC) with square root of sNN = 8.8 and 5.5 TeV, respectively, which could be triggered in the large LHC detectors. We use ATLAS as an example. The lead ion is treated as a source of (coherently produced) photons with energies and intensities greater than those of equivalent ep collisions at the DESY collider HERA. We find very large rates for both inclusive and diffractive production that will extend the HERA x range by nearly an order of magnitude for similar virtualities. We demonstrate that it is possible to reach the kinematic regime where nonlinear effects are larger than at HERA.     

Hadronic matter at high energy density and the search for the hadron–parton QCD phase transition

Recent progress is reviewed concerning the evidence for a phase change in strongly interacting matter, as predicted by Lattice QCD theory to occur at an energy density of about 2–3 GeV per cubic fermi. Experiments at the CERN SPS with Lead (208 Pb) beams show that such densities have been reached, and suggest a set of observable quantities to bear first evidence concerning the transition.     

Hadron fragmentation at high energies and quark constituents

The systematics of particle ratios in high-energy pp collisions suggest that the same constituent partons are active in the production of particles at small and large transverse momentum p_T. We relate various features of the pion spectra at small p_T in the fragmentation region and in the central region of pp collisions to corresponding features observed in ep and en collisions assuming that the dissociation of the proton into quark partons is the common underlying process.     

Strong and electroweak corrections to the production of a Higgs boson+2 jets via weak interactions at the Large Hadron Collider

Radiative corrections of strong and electroweak interactions are presented at next-to-leading order for the production of a Higgs boson plus two hard jets via weak interactions at the CERN Large Hadron Collider. The calculation includes all weak-boson fusion and quark-antiquark annihilation diagrams as well as the corresponding interferences. The electroweak corrections, which are discussed here for the first time, reduce the cross sections by 5% and thus are of the same order of magnitude as the QCD corrections.     

Final state interactions in the parton model and massive lepton pair production

A scheme of assignments for the 0⁺ nonet is proposed with the S¹ (1000) effect corresponding to resonance poles both on Sheet II and Sheet III, and with the ? located somewhere above 1100 MeV, e.g. at 1300 MeV. A tentative fit of the decay characteristics of these and the other nonet condidates, δ(970) and κ(～1200) is achieved with the mixing angle given by cos²θ_S～ 0.13 instead of the ‘ideal’ value of $\text{2}\text{3}$.     

A confining model of the weak interactions

The weak interactions are analyzed as the low-energy effective interactions of a strong coupling gauge theory whose scale is $\text{G}{}_{\mathrm{<mtext>F</mtext>}}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$. The light fermions are shown to be bound states obeying 't Hooft's consistency conditions. The symmetries of the theory are used to analyzed the low-energy interactions. Instanton mediated baryon violations are discussed and experimental signatures at high energy are presented.     

Hadron production inpBe interactions at 14.6 GeV/c

Invariant cross sections for the production of ^±,K ^±,p, andd inpBe interactions at 14.6 GeV/c are well reproduced by calculations carried out in the framework of the Rossendorf collision model.Communicated by: F. Lenz     

Clan structure and intermittency in proton-nucleus interactions at high energy

In this paper we examine the similarity between clan structure and self-similar cascading in high energy proton-nucleus interactions at 70 GeV/c in emulsion. The investigation shows that the negative bionomial fitting parameterk can be used for the evaluation of factorial moments in intermittency studies and that these exhibit similar behaviour with those derived from nonstatistical procedure. The results of our study signify compatibility between clan cascading and self-similar cascading in soft hadroization processes.