High-Energy Scattering Research Articles

Color Fluctuations in the Nucleon in High-Energy Scattering

We study quantum fluctuations of the nucleon's parton densities by combining QCD factorization for hard processes with the notion of cross section fluctuations in soft diffraction. The fluctuations of the small-x gluon density are related to the ratio of inelastic and elastic vector meson production in ep scattering. A simple dynamical model explains the HERA data and predicts the x and Q2 dependence of the ratio. In pp/p[over ]p scattering, fluctuations enhance multiple hard processes (but cannot explain the Tevatron CDF data), and reduce gap survival in central exclusive diffraction.

High-energy string scatterings of compactified open string

We calculate high-energy massive string scattering amplitudes of compactified open string. We derive infinite linear relations, or stringy symmetries, among soft high-energy string scattering amplitudes of different string states in the Gross kinematic regime (GR). In addition, we systematically analyze all hard power-law and soft exponential fall-off regimes of high-energy compactified open string scatterings by comparing the scatterings with their 26D noncompactified counterparts. In particular, we discover the existence of a power-law regime at fixed angle and an exponential fall-off regime at small angle for high-energy compactified open string scatterings. The linear relations break down as expected in all power-law regimes. The analysis can be extended to the high-energy scatterings of the compactified closed string, which corrects and extends the previous results in [J.C. Lee, Y. Yang, Linear relations and their breakdown in high energy massive string scatterings in compact spaces, Nucl. Phys. B 784 (2007) 22].

Development of the very low angle detector for epithermal neutron scattering at low momentum transfers

The design and prototype tests of the Very Low Angle Detector (VLAD) for epithermal neutron scattering at low momentum transfers are presented. The detector will be installed on the VESUVIO spectrometer at the ISIS spallation neutron source for so-called High-energy Inelastic Neutron Scattering (HINS) experiments. It will consist of an array of Resonant Detectors (RD) covering the scattering range 1/spl deg/-5/spl deg/. The results of prototype tests with a reduced set of RD units demonstrate the feasibility of the measurement in the adverse environmental conditions of ISIS. Simulations of particle interactions using the GEANT4 code show that the envisaged detector design can meet the requirements in terms of efficiency, cross-talk between detection channels and neutron scattering events in the detector.

From Target to Projectile and Back Again: Self-Duality of High-Energy Scattering Evolution in QCD

We prove that the complete kernel for the high-energy evolution in QCD must be self-dual. The relevant duality transformation is formulated in precise mathematical terms and is shown to transform the charge density into the functional derivative with respect to the single-gluon scattering matrix. This transformation interchanges the high and the low density regimes. We demonstrate that the original Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner kernel, valid at large density, is indeed dual to the low density limit of the complete kernel derived recently in hep-ph/0501198.

Quantization and high energy unitarity of 5D orbifold theories with brane kinetic terms

Five-dimensional field theories compactified on an ${S}^{1}/{\mathbb{Z}}_{2}$ orbifold naturally include local brane kinetic terms at the orbifold fixed points at the tree as well as the quantum level. We study the quantization of these theories before the Kaluza-Klein reduction and derive the relevant Ward and Slavnov-Taylor identities that result from the underlying gauge and Becchi-Rouet-Stora symmetries of the theory. With the help of these identities, we obtain a generalization of the equivalence theorem, where the known high-energy equivalence relation between the longitudinal Kaluza-Klein gauge modes and their respective would-be Goldstone bosons is extended to consistently include the energetically suppressed terms in the high-energy scatterings. Demanding perturbative unitarity, we compute upper limits on the number of the Kaluza-Klein modes. We find that these limits weakly depend on the size of the brane kinetic terms.

Unitarity of Little Higgs models signals new physics of UV completion

The “Little Higgs” opens up a new avenue for natural electroweak symmetry breaking in which the standard model Higgs particle is realized as a pseudo-Goldstone boson and thus is generically light. The symmetry breaking structure of the Little Higgs models predicts a large multiplet of (pseudo-)Goldstone bosons and their low energy interactions below the ultraviolet (UV) completion scale Λ∼4πf∼O(10) TeV, where f is the Goldstone decay constant. We study unitarity of the Little Higgs models by systematically analyzing the high energy scatterings of these (pseudo-)Goldstone bosons. We reveal that the collective effect of the Goldstone scatterings via coupled channel analysis tends to push the unitarity violation scale ΛU significantly below the conventional UV scale Λ∼4πf as estimated by naive dimensional analysis (NDA). Specifically, ΛU∼(3–4)f, lying in the multi-TeV range for f∼1 TeV. We interpret this as an encouraging sign that the upcoming LHC may explore aspects of Little Higgs UV completions, and we discuss some potential signatures. The meanings of the two estimated UV scales ΛU (from unitarity violation) and Λ (from NDA) together with their implications for an effective field theory analysis of the Little Higgs models are also discussed.

Nucleon-Nucleon High-Energy Scattering

The high energy pn charge exchange and pp elastic scattering reactions are studied in an effective hadron model for the energy range of s ~ 50 to 400 GeV2. The main features of the observed differential cross section of the pn charge exchange reaction, the forward peak and the scaling behavior over the large energy range, are well reproduced by a combination of π-, ρ-exchange and a 4-Nucleon contact term. The latter acts as a background field which turns out to be naturally suppressed in elastic N N scattering but contributes significantly to the charge-exchange reaction.

What Can High-Energy Elastic Scattering Tell Us About Nucleon Structure?

Basic assumptions used in the analysis of elastic differential cross section data will be discussed and the arguments for the transparency of nucleons will be analyzed. It will be shown that the transparency of nucleon is a direct consequence when a weak t dependence of hadronic amplitude phase is used in analogy with optics. The phase t dependence may be hardly uniquely determined from elastic scattering data, being only partially limited by the Coulomb-hadronic interference existing in a very narrow region of small |t| values. The given situation will be demonstrated with the help of data for \(\bar pp\) collisions at 541 GeV; nucleons being transparent or having hard cores may be admitted by the elastic data themselves. However, when further characteristic of inelastic and elastic processes are compared, the nucleon with hard core should be preferred. The most probable characteristics of nucleon structure derived from the data will be presented.

High-energy Scattering in Gauge Theories and Integrable Spin Chains

In the leading log approximation and at large NC the interaction of two fermionic and one gluonic reggeons is described by an integrable system corresponding to an open spin chain.

Nuclear Structure in High Energy Scattering Processes

We suggest that in hard scattering processes the nuclear medium can be viewed as a background parton sea where the bound nucleons are “soaked”. The quark and gluon distributions in nuclei are investigated under this assumption. The comparisons of this model with the experimental data of the structure function ratio from charged lepton deep inelastic scattering, the gluon momentum distribution ratio from inelastic production, and the dimuon yield ratio from Drell–Yan dimuon production are present.

Factorization for High-Energy Scattering

I demonstrate that the amplitude of the high-energy scattering can be factorized in a product of two independent functional integrals over "fast" and "slow" fields which interact by means of Wilson-line operators -- gauge factors ordered along the straight lines.

Fractal Geometry of Helicity Amplitude

Fractal geometry is in use to get lucid and visual explanation of many a natural and complex phenomena. High Energy Scattering process is quite complex a happening in science. Several methods are available to explain the events linked with high energy scattering. Mohanty et al.4 have tried using a method named Optimized Polynomial Expansion Technique to study the characteristics of hyperon-nucleon scattering. The present paper attempts to study the same in analysing its mathematical function as a fractal exposition. Here the analyticity property of helicity amplitude is treated using fractal theory and it is found that the function is analytic and the domain of analyticity is also an ellipse. The fractal geometry of this function presents a typical Julia Dragon set which looks like a San Marcos Dragon as per Mandelbrot6 and has Mandelbrot-like sets as well as Julia sets carved inside it.

High Energy Scattering of Non-Critical Strings

We summarize recent work, in which we consider scattering amplitudes of non-critical strings in the limit where the energy of all external states is large compared to the string tension. We show that the high energy limit is dominated by a saddle point that can be mapped onto an electrostatic equilibrium configuration of an assembly of charges associated with the external states, together with a density of charges arising from the Liouville field. The Liouville charges accumulate on line segments, which produce quadratic branch cuts on the worldsheet. The electrostatic problem is solved for string tree level in terms of hyperelliptic integrals and is given explicitly for the 3- and 4-point functions. For generic values of the central charge, the high energy limit behaves in a string-like fashion, with exponential energy dependence.

Cut diagrams for high energy scatterings.

A new approach is introduced to study QCD amplitudes at high energy and comparatively small momentum transfer. Novel cut diagrams, representing the resummation of Feynman diagrams, are used to simplify the calculation and to avoid delicate cancellations encountered in the usual approach. An explicit calculation to the sixth order is carried out to demonstrate the advantage of cut diagrams over Feynman diagrams.

High energy scattering beamlines at European Synchrotron Radiation Facility

The scientific background and scope of research at the High Energy Scattering Beamlines of the European Synchrotron Radiation Facility are reviewed briefly. The beamline has two different insertion devices (IDs), a permanent magnet multipole wiggler and a superconducting wavelength shifter. The IDs can be used alternatingly, and both provide circularly polarized radiation off the orbit plane up to energies of several hundreds of keV. Measurements of the spectral brightness and the polarization components by energy dispersive powder diffraction and Compton scattering from iron in an alternating magnetic field are presented and compared with calculations based on source parameters. The beamline optics are based on use of horizontally reflecting bent Si crystals. These provide various focusing geometries, and the calculated flux of monochromatic radiation is given at energies between 30 and 175 keV. The maximum of 2×1012 photons/s is reached at 80 keV. The main experimental apparatus in the initial operation includes a high-resolution three-axis diffractometer, and a scanning-type Compton spectrometer.

High-energy scatterings of many electroweak gauge bosons

We present an application of the equivalence theorem and the multispinor representation of gauge fields to the standard model of electroweak interactions at very high energies. The equivalence theorem allows us to efficiently treat the longitudinal vector bosons while the multispinor formalism makes the transverse vector bosons easy to handle. We generalize the work of Berends and Giele to derive a recursion relation for a current consisting of a pair of longitudinal vector bosons plus any number of transverse vector bosons. It is shown that for certain helicity configurations this current is related to a corresponding current involving only transverse vector bosons. Consideration of a U( N), rather than an SU( N), gauge theory enables us to incorporate the mixing in the SU(2) × U(1) electroweak theory and to derive certain sum rules for the currents for transverse gauge bosons. We also give explicit expressions for four-particle and five-particle scattering amplitudes involving a pair of longitudinal vector bosons.

A High-Energy Scattering Approximation

A High-Energy Scattering Approximation

Study of the High-Energy Scattering Approximation

Study of the High-Energy Scattering Approximation

High Energy Scattering Theory and Collective Coordinate

In this paper, by the collective coordinate of A. Bohr, the scattering amplitudes of two composite many-particle systems can be obtained. And the collective excitation for two complex many-particle systems in the scattering process is discussed.

High Energy Scattering Theory of Many-Particle System

Within the framework of the Glauber Theory, we divide the many-particle system into two subsystems, formed by the “Valence” particles and the “sea” particles respectively. Then the multiple scattering amplitudes can also be divided into “sea” - “sea”, “sea” - “Valence”, “Valence” - “sea”, and “Valence”- “Valence” multiple scattering amplitudes. For the calculation of these different amplitudes, different effective approximate methods are proposed. Finally, the S matrix for the “sea” - “sea”, “sea” - “Valence”;“Valence” - “sea” and “Valence” - “Valence” processes is, obtained which is physically clear and convenient in calculation.