Kyungsik Kang

Benchmarks for the forward observables at RHIC, the Tevatron-run II, and the LHC

We present predictions on the total cross sections and on the rho parameter for present and future pp and (-)pp colliders, and on total cross sections for gammap-->hadrons at cosmic-ray energies and for gammagamma-->hadrons up to sqrt[s]=1 TeV. These predictions are based on an extensive study of possible analytic parametrizations invoking the largest hadronic dataset available at t=0. The uncertainties on total cross sections reach 1.9% at the Relativistic Heavy Ion Collider, 3.1% at the Tevatron, and 4.8% at the Large Hadron Collider, whereas those on the rho parameter are, respectively, 5.4%, 5.2%, and 5.4%.

Hadronic scattering amplitudes: Medium-energy constraints on asymptotic behavior

We consider several classes of analytic parametrisations of hadronic scattering amplitudes, and compare their predictions to all available forward data (p p, pbar p, pi p, K p, gamma p, gamma gamma, Sigma p). Although these parametrisations are very close for sqrt(s) > 9 GeV, it turns out that they differ markedly at low energy, where a universal pomeron term ~log^2(s) enables one to extend the fit down to sqrt(s)=4 GeV.

Bounds on the Soft Pomeron Intercept

The Donnachie-Landshoff fit of total cross sections has now become a standard reference for models of total, elastic and diffractive cross-sections. Adopting their philosophy that simple-pole exchanges should account for all data to present energies, we assess the uncertainties on their fits, and show that the pomeron intercept which controls total cross sections and the real part of the elastic amplitude, can lie anywhere between 1.07 and 1.1, with a preferred value 1.094. supported in part by the USDOE contract DE-FG02-91ER 40688-Task A. supported in part by the Korea Science and Engineering Foundation through the Center for Theoretical Physics, Seoul National University, and by the Ministry of Education through contract BSRI-95-2427.Abstract The Donnachie-Landshoff fit of total cross sections has now become a standard reference for models of total, elastic and diffractive cross-sections. Adopting their philosophy that simple-pole exchanges should account for all data to present energies, we assess the uncertainties on their fits. Our best estimate for the pomeron intercept is 1.096−0.009+0.012, but several models have a good χ2 for intercepts in the range [1.07,1.11].

Heisenberg saturation of the Froissart bound from AdS-CFT

Abstract In a previous paper, we have analyzed high energy QCD from AdS-CFT and proved the saturation of the Froissart bound (a purely QCD proof of which is still lacking). In this Letter we describe the calculation in more physical terms and map it to QCD language. We find a remarkable agreement with the 1952 Heisenberg description of the saturation (pre-QCD!) in terms of shockwave collisions of pion field distributions. It provides a direct map between gauge theory physics and the gravitational physics on the IR brane of the Randall–Sundrum model. Saturation occurs through black hole production on the IR brane, which is in QCD production of a nonlinear pion field soliton of a Born–Infeld action in the hadron collision, that decays into free pions.

Planckian scattering effects and black hole production in low M(Pl) scenarios

We reanalyze the question of black hole creation in high energy scattering via shock wave collisions. We find that string corrections tend to increase the scattering cross section. We analyze corrections in a more physical setting, of Randall-Sundrum type and of higher dimensionality. We also analyze the scattering inside anti-de Sitter backgrounds.

New class of quark mass matrix and calculability of the flavor mixing matrix

We discuss a new general class of mass matrix {ital Ansatz} that respects the fermion mass hierarchy and {ital calculability} of the flavor mixing matrix. This is a generalization and justification of the various specific forms of the mass matrix by successive breaking of the maximal permutation symmetry. By confronting the experimental data, a large class of the mass matrices are shown to survive, while certain specific cases are phenomenologically ruled out. Also the CP violation turns out to be maximal, when the phase of the (1,2) element of the mass matrix is {pi}/2. {copyright} {ital 1997} {ital The American Physical Society}

Matter effects in four-neutrino mixing

The evidence in favor of neutrino oscillations implies the existence of at least three independent neutrino mass-squared differences. If the Liquid Scintillation Neutrino Detector (LSND) results are confirmed, transitions into active and sterile neutrinos can take place simultaneously for both solar and atmospheric neutrinos. In this paper we present a formalism for the calculation of the transition probabilities into active and sterile neutrinos for solar {nu}{sub e}s and atmospheric {nu}{sub {mu}}s, taking into account the matter effects in the Sun and in the Earth. We find that the solar neutrino transition probabilities depend on just one single additional parameter compared to that of the standard two-generation analysis, while for atmospheric neutrinos two additional mixing angles are necessary to analyze the data in addition to those of the usual two-generation analysis. (c) 2000 The American Physical Society.

Forward scattering at collider energies and eikonal unitarization of the odderon

Abstract The continuing increase of hadron total cross sections up to the highest energies currently available can most naturally be understood through an eikonal mechanism, leading to the saturation of the Froissart bound. This picture can be motivated in a nonperturbative treatment of QCD, e.g., in the large- N limit. It is then natural to ask whether this same mechanism would lead to the maximal allowed behavior for the difference of the particle-particle and antiparticle-particle cross section, i.e., the “maximal odderon”. We shall show in this paper that, using eikonals which are dynamically meaningful for high-energy hadron-hadron scattering at collider energies, this behavior is not possible.

Almost Maximally Broken Permutation Symmetry for Neutrino Mass Matrix

Assuming three light neutrinos are Majorana particles, we propose mass matrix ansatz for the charged leptons and Majorana neutrinos with family symmetry S3 broken into S1 and S2, respectively. Each matrix has three parameters, which are fixed by measured charged lepton masses, differences of squared neutrino masses relevant to the solar and the atmospheric neutrino puzzles, and the masses of three light Majorana neutrinos as a candidate for hot dark matter with ∑|mν|~ 6 eV. The resulting neutrino mixing is compatible with the data for the current upper limit, th <0.7 eV, of neutrino-less double beta decay experiments, and the current data for various types of neutrino oscillation experiments. One solution of our model predicts that νμ→ντ oscillation probability is about < 0.008 with Δm2 ~ 10-2eV2, which may not be accessible at CHORUS and other on-going experiments.

Charm and fancy changing neutral currents with five quarks

Abstract We propose a five-quark weak interaction model based on the SU(2) × U(1) × U(1)′ gauge group. The fifth quark f with fancy flavor has electric charge 2 3 . The model induces the charm and fancy changing neutral currents in a natural fashion which are responsible for substantial D0 − D 0 mixing to explain the observed wrong-sign dimuon events. However, these flavor changing neutral currents do not couple to leptons, thus forbidding trimuons to appear as the experiments indicate thus far. We discuss in addition how our model can be extended to a vector-like theory.