Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 2008"

Direct Production of Photons and Dileptons in Thermodynamical Models of Multiple Hadron Production

Abstract: The thermodynamical picture of a hot lump of hadronic matter («clusters», high-density gluonic clouds and especially suitable cases of hydrodynamical theories of Heisenberg and Landau) naturally leads to direct production of gamma quanta («black-body radiation») and—in the next order ine2—of lepton pairs. At largepT their spectra reproduce the main features of the pionic spectrum. The intensity of γ’s exceedse2 times that of the π’s, due to the relatively large volume of the radiating system and to the long duration of its expansions. However, since the dynamics of the heated hadronic vacuum is not known, pre-exponential factors cannot be safely calculated. All this is expected to hold for the overall c.m.s. energy\(\sqrt 8 \sim \left( {10 \div 10^2 } \right)\) GeV. For even higher energies with a correspondingly increasing mass of the lump (if such lumps exist), probably at\(\sqrt 8 > 10^3 \) GeV, γ quanta (and for even larger lumps,\(\sqrt 8 \sim 10^4 \) GeV, leptons as well) may become equal partners to hadrons in thermodynamical equilibrium. Almost all the results were published by the present author about 15 years ago in Russian (and only briefly mentioned in some of his review papers in English). In this paper they are somewhat extended and discussed in more detail in the light of new experiments on large-pT leptons and of the quark-gluon ideas.

A new look at solid-state fractures, particle emission and «cold» nuclear fusion

Abstract: The well-known phenomenon of high-energy particle emission from newly created fractures in solid materials is seen to have a natural explanation in terms of the ponderomotive forces exerted by the coherent e.m. fields associated with the «superradiant» motions of the charged plasmas of solids. The possible role of these fields to produce the neutron bursts that have been recently observed concomitantly with «crack» formation in Ti-deuterides is briefly discussed.

Excited quarks and new hadronic states

Abstract: We develop the phenomenology of excited quarks q*. We describe the spectroscopy of new \(q\bar q*\) mesonic states and calculate the cross-sections of various production mechanisms in e+e-, γγ, lepton-hadron and hadron-hadron collisions.

The Photon in Pseudoclassical Mechanics

Abstract: We describe a massless particle belonging to the D1,0 ⊕ D0,1 representation ofSL2,C by means of pseudoclassical mechanics, starting by a set of first-class constraints. By canonical quantization one obtains the one-photon wave functions in the Lorentz gauge, whereas by path integral quantization one finds the noncovariant transverse free propagator. In the reduced phase space, the canonical variables are manifestly covariant only under02 ⊠ R4 and can be quantized by using the Angelopoulos-Bayen-Flato operators. By means of a distribution function g on the Grassmann variables we obtain the description of a classical ray of light with the associated Stokes parameters. The quantization of ρ gives the quantum Stokes parameters.

The neutron-proton interaction energy of the valence nucleons

Abstract: For a great number of nuclei, it is now possible to calculate the value of the neutron-proton interaction energy of the valence nucleons using experimental mass data. The total n-p interaction energyEnp of the valence shells of,e.g., an odd-odd nucleus can be calculated from partial interaction energies {su\fk}{inn-p}, {su\fk}{inn-2p}{ini}, {su\fk}{inp-2n}{inj},{su\fk}{in2p}{ini}-{in2n}{inJ} which are the interaction energy of the last couple of nucleons or nucleon pairs in this nucleus and in its various underlying nuclei. {su\fk}{inn-p}, defined asEnp divided byNpNn, the product of the valence proton and neutron numbers, is only a mean value of the n-p interaction energy per n-p couple in a given nucleus. Tables ofEnp and {su\fk}{inn-p} values, and of,{su\fk}{inn-p} , {su\fk}{inn-2p} , {su\fk}{inp-2n} and {su\fk}{in2p-2n} values, are given for the 1d5/2, 2s1/2 and 1d3/2 valence shells of the doubly magic16O nucleus. Nucleon pairing is found to play an eminent role. The n-p interaction energy is almost unchanged if every neutron is converted into a proton and vice versa, and is extremely dependent on the rank of the nucleons in their shell, being maximum if they have the same rank. The n-p interaction energy is strongly enhanced at each subshell closure.

High energy single top photoproduction at the LHC

Abstract: High-energy photon-proton interactions at the LHC offer interesting possibilities for the study of top properties. Using a fast simulation of a LHC-like detector, first results on the measurement of the |V_{tb}| matrix element using Wt photoproduction are presented. Anomalous photoproduction of single top due to Flavour-Changing Neutral Currents permits to improve the current limits on the coupling parameters, k_{tu\gamma} and k_{tc\gamma} after only 1 fb^{-1}. Comment: 8 pages, 5 tables, 1 figure. Presented at the International Workshop on Top Quark Physics (TOP2008), La Biodola, Isola d'Elba, Italy, May 2008. To be published in "Il nuovo cimento"

Status of the Standard Model at the LHC Start

Abstract: I present a concise review of where we stand in particle physics today. First, I will discuss QCD, then the electroweak sector and finally the motivations and the avenues for new physics beyond the Standard Model.

Monte Carlo generators for top-quark physics at the LHC

Abstract: B.S. Acharya(), F. Cavallari(), G. Corcella(3)(4)(∗), R. Di Sipio() and G. Petrucciani() () Abdul Salam International Center for Theoretical Physics and INFN, Sezione di Trieste, Italy () INFN, Sezione di Roma, Italy () Museo Storico della Fisica e Centro Studi e Ricerche E. Fermi, Roma, Italy () Scuola Normale Superiore and INFN, Sezione di Pisa, Italy () Università di Bologna and INFN, Sezione di Bologna, Italy

Asymptotics of total cross-sections and ultimate temperature of hadronic systems

Abstract: Within the framework ofS-matrix formulation of statistical mechanics the connection between the properties of the hadronic system and the asymptotic behaviour of total cross-sections is studied; it is found that the hadronic system has an ultimate temperature if the total crosssection decreases, or it tends to a constant value from above, while the indefinite growth of the total cross-section or its approach to a limit from below means that the hadronic system allows an unlimited heating. Moreover, the density of state of the hadronic matter, the equation of state of a hadronic system and the multiplicity of produced particles are obtained.

Signatures of new physics at 14-TeV

Abstract: I give an overview of the ideas and of the problems that orient the expectations for new physics at the Large Hadron Collider and, whenever I can, I describe the corresponding signals.

A test of the Δ S =Δ Q selection rule in K μ3 0 decay

Abstract: A test of the ΔS=ΔQ selection rule in K μ3 0 decay was performed using optical spark chambers. K0-mesons were produced by 3 GeV/c π− in the reaction π−p→ΛK0. 100 events with proper decay times between 0.5 and 6.5 K 0 lifetimes were analysed to give a ratio of the ΔS=−ΔQ to ΔS=ΔQ amplitudes Rex′=0.04 −0.13 +0.10 , Imx′=0.12 −0.16 +0.17 .

Transport-theoretical unification of field equations

Abstract: A general transport equation is formulated as a generalization of Newton’s first law and the concept of contact forces, and it is shown how one can interpret the Maxwell equations, the inhomogeneous wave equations for the Lorentz-gauge potentials, and the Dirac equation as describing certain underlying transport phenomena in the strong-scattering limit.

Higgs at LHC

Abstract: An overview of recent theoretical results on the Higgs boson and its discovery strategy at ATLAS and CMS will be presented, focusing on the main Higgs analysis effective with low integrated luminosity (less than 30 fb^-1).

A canonical description of the solitary quantum decay

Abstract: A quantum picture of solitary motion is presented. Time evolution of a quantumN-soliton is described as a transition through infinitely many unitarily inequivalent representations of the canonical commutation relations. The statistical nature and the irreversibility of the process naturally emerge. Their origin is found in the nonunitary character of the transformation among the unitarily inequivalent representations.

Superfield actions forN=4 and 8 degenerate central-charge multiplets

Abstract: We evaluate the component contributions in the superfield action for degenerate central-charge multiplets ofN=4 and 8 supersymmetry. Some of the formulae are checked by the aid of the algebraic manipulation programme STENSOR. The final result is that the action for eachN is a higher-order total derivative in the central-charge directions. The resulting relation between the particle spectrum and the region of integration in the central-charge directions is described.

Vacuum Energy inR1×S3

Abstract: ζ-function regularization is used to evaluate the vacuum energy and pressure in a space-time with topologyR1×S3. We study conformally invariant field theories,i.e. conformally coupled massless scalars, minimally coupled electromagnetic and neutrino fields. We obtain finite results without introducing any arbitrary wave-length cut-off or subtraction prescription. They agree with previous calculations.

A model of multiparticle final states in hadronic and current-induced reactions

Abstract: A constituent multichain model in the (1+1) dimension is presented which gives exclusive and inclusive distribution functions of multimeson final states in hadronic soft collisions, in e+e− annihilations and in deep inelastic electroproductions. Scaling behaviour of inclusive quantities in hadronic and deep inelastic phenomena is unifiedly understood as due to a balance between tension and fragility of the constituent chain, on the basis of a two-phase picture of constituent urbaryons. The extension of the model to full dimensions and other ingredients towards the real world are discussed, and remarks on related approaches are given.

Interaction-mediating vector bosons as collective oscillations of the vacuum

Abstract: A theory of quantum mechanics underlying the current theory is proposed. Every state—including the vacuum—must satisfy the linear equationOΨ=0. Ψ is a sum of products of spin-1/2 kets.O is a linear operator invariant under the inhomogeneous Lorentz group and the unitary group (U(n). It is modelled after the integral of the Lagrangian density in quantum field theory, and is expressed in terms of spin-1/2 kets and bras. Interaction-mediating vector bosons enter as collective oscillations of the vacuum. The direct four-fermion interaction inO can be re-expressed as a fermion-boson interaction. The form of the boson creation, operators is derived from gauge transformation arguments. The additional assumption of a very small structure constant for the vacuum leads to an understanding of the ∂θ/∂xμ term which is added to the boson potential by a gauge transformation. The possible forms and effects of spontaneous symmetry breaking of the vacuum are discussed.

An interpretation of inelastic hadron-nucleus interactions

Abstract: A simple model of hadron-nucleus interactions is proposed. The mass number dependence of incoherent-interaction cross-sections, the multiplicity distribution, the rapidity distribution of secondary particles and the excitation energy of the residual nucleus are calculated. The cross-section is simply explained by the concept of probability. The rapidity and multiplicity distributions are given by superposition of elementary processes. The distribution of the number of heavily ionizing tracks (Nh) and theNh-dependence of the average multiplicaties of charged secondaries are derived from the excitation energy of the residual nucleus. Comparison of calculated quantities with experimental data shows satisfactory agreement.

Statistical bootstrap model and phase transition from hadron matter to quark gluon plasma

Abstract: We analyse three models for hadron matter, based on the statistical bootstrap model for extended hadrons, with volumes treateda la Van der Waals. The models, describing the hadronic system as an ideal gas of fireballs (or clusters), differ from each other in the interpretation of the factor 2V.p/(2π)3 which multiplies the mass spectrum: this factor is totally dynamical in model 2, partially (only the volumeV) in model 1 and kinematical in model 0. Consequently, three different critical curves bound the hadronic phase. If we take into account the description of the quark-gluon plasma by a simple model, we find that:a) all three models exhibit features typical of a phase transition between the hadronic phase and the quark-gluon plasma phase;b) applying the Maxwell construction leads to a finite region of co-existence between these two phases. In model 0, it depends on parameters (like the bag constant) whether the phase transition is of first or second order; in the other two models, it is of first order.

Re-discovery of the top quark at the LHC and first measurements.

Abstract: This paper describes the top quark physics measurements that can be performed with the first LHC data in the ATLAS and CMS experiments.

The differential approach to spinors and their symmetries

Abstract: A formulation of spinor analysis in space-time is given in terms of smooth sections of a real Clifford bundle. Its relation to the two-component complex calculus for spinor components is elucidated. Treating spinors in terms of inhomogeneous differential forms carryingPIN 3,1 andSPIN 3,1 representations enables the discrete covariances of the Maxwell-Dirac system to be induced naturally from smooth isometries of the space-time metric. Attention is drawn to the distinction between the Dirac and Kahler equations in curved space when expressed in this geometric formulation.

The four site Higgsless model at the LHC

Abstract: We consider the four-site Higgsless model, which predicts the existence of four charged and two neutral extra gauge bosons, $W_{1,2}^\pm$ and $Z_{1,2}$. In contrast to other Higgsless models, characterized by fermiophobic extra gauge bosons, here sizeable fermion-boson couplings are allowed by the electroweak precision data. We thus analyse the prospects of detecting the new predicted particles in the mostly favored Drell-Yan channel at the LHC.