Edward E. Boos

Minimal supersymmetric standard model Higgs bosons in the intense-coupling regime

We perform a comprehensive study of the Higgs sector of the Minimal Supersymmetric extension of the Standard Model in the case where all Higgs bosons are rather light, with masses of O(100 GeV), and couple maximally to electroweak gauge bosons and strongly to standard third generation fermions, i.e. for large values of the ratio of the vacuum expectation values of the two Higgs doublet fields, tan β. We first summarize the main phenomenological features of this “intense–coupling” scenario and discuss the available constraints from direct searches of Higgs bosons at LEP2 and the Tevatron as well as the indirect constraints from precision measurements such as the ρ parameter, the Zbb̄ vertex, the muon (g − 2) and the decay b → sγ. We then analyze the decay branching fractions of the neutral Higgs particles in this regime and their production cross sections at the upcoming colliders, the Tevatron Run II, the LHC, a 500 GeV e+e− linear collider (in the e+e− and γγ options) as well as at a μ+μ− collider.

Detection of the neutral MSSM Higgs bosons in the intense-coupling regime at the LHC

Abstract We analyse the prospects to detect at the LHC the neutral Higgs particles of the Minimal Supersymmetric Standard Model, when the masses of the two CP-even h , H and of the CP-odd A boson are close to one another, and the value of tan β is large. In this “intense-coupling regime”, the Higgs bosons have strongly enhanced couplings to isospin down-type fermions and large total decay widths, so that the γγ,WW ∗ and ZZ ∗ decay modes of the three Higgs bosons are strongly suppressed. We advocate the use of the decays into muon pairs, h , H , A → μ + μ − , to resolve the three Higgs boson peaks: although the branching ratios are small, O (10 −4 ) , the resolution on muons is good enough to allow for their detection, if the mass splitting is large enough. Using an event generator analysis and a fast detector simulation, we show that the process pp→b b μ + μ − , when at least one of the b -quarks is detected, is viable.

Effective Lagrangians for physical degrees of freedom in the Randall–Sundrum model

We derive the second variation Lagrangian of the Randall–Sundrum model with two branes, study its gauge invariance and diagonalize it in the unitary gauge. We also show that the effective four-dimensional theory looks different on different branes and calculate the observable mass spectra and the couplings of the physical degrees of freedom of five-dimensional gravity to matter.

PHYSICAL DEGREES OF FREEDOM IN STABILIZED BRANE WORLD MODELS

We consider brane world models with interbrane separation stabilized by the Goldberger–Wise scalar field. For arbitrary background, or vacuum configurations of the gravitational and scalar fields in such models, we construct the second variation Lagrangian, study its gauge invariance, find the corresponding equations of motion and decouple them in a suitable gauge. We also derive an effective four-dimensional Lagrangian for such models, which describes the massless graviton, a tower of massive gravitons and a tower of massive scalars. It is shown that for a special choice of the background solution the masses of the graviton excitations may be of the order of 1 TeV, the radion mass of the order of 100 GeV, the inverse size of the extra dimension being 1 TeV. In this case the coupling of the radion to matter on the negative tension brane is approximately ten times weaker than in the unstabilized model with the same values of the fundamental five-dimensional energy scale and the interbrane distance.

MINIMAL GAUGE INVARIANT CLASSES OF TREE DIAGRAMS IN GAUGE THEORIES

We describe the explicit construction of groves, the smallest gauge invariant classes of tree Feynman diagrams in gauge theories

Testing extra dimensions below the production threshold of Kaluza-Klein excitations

We consider a stabilized Randall Sundrum 1 model in the energy range below the direct production of Kaluza-Klein (KK) states. In this range, we work out the effective Lagrangian due to exchange of heavy KK tensor graviton and scalar radion states and compute explicitly the corresponding effective coupling constants. As an example, the Drell-Yan lepton pair production at the Tevatron and the LHC is analyzed in two situations, when the first KK resonance is too heavy to be directly detected at the colliders, and when the first KK resonance is visible, but other states are still too heavy. It is shown that in both cases the contribution from the KK invisible tower leads to a modification of final particles distributions. In particular, for the second case a nontrivial interference between the first KK mode and the rest KK tower takes place. Expected 95% C.L. limits for model parameters for the Tevatron and the LHC are given. In the Appendix, useful formulas for the cross sections and distributions of various new 2{yields}2 processes via heavy KK tower exchange are presented, the new formulas containing nonzero particle masses for final state fermions and bosons. The formulas and numerical results are obtained bymorexa0» means of the CompHEP code, in which all new effective interactions are implemented providing a tool for simulation of corresponding events and a more detailed analysis.«xa0less

Higgs-radion mixing in stabilized brane world models

We consider a quartic interaction of the Higgs and Goldberger-Wise fields, which connects the mechanism of the extra dimension size stabilization with spontaneous symmetry breaking on our brane and gives rise to a coupling of the Higgs field to the radion and its KK tower. We estimate a possible influence of this coupling on the Higgs-radion mixing and study restrictions on model parameters from the LHC data.

Vector leptoquark pair production in e+e− annihilation

The cross section for vector leptoquark pair production in e + e annihilation is calculated for the case of finite anomalous gauge boson couplings �,Z and �,Z. The minimal cross section is found to behave ∝ � 7 , leading to weaker mass bounds in the threshold range than in models studied previously.

ON A POSSIBLE CORRESPONDENCE OF THE NEW NARROW RESONANCES IN CHARGED PARTICLE SYSTEMS TO THE RELATIVISTIC COULOMB LEVELS IN CONTINUUM

In the paper the existence of new quasi-stationary levels in the relativistic Coulomb problem is predicted and their positions are calculated on the basis of the numerical solution of the quasi-potential equation. The results obtained are used for interpretation of the narrow electron-positron resonances revealed in heavy ions collisions and of the diproton resonances observed in neutron-proton interactions. The close relationship of the observed states with the von Neumann-Wigner levels embedded in the continuum, is indicated.

Top quarks at photon colliders

A review of results on top quark physics expected at the Photon Linear Colliders is presented.Abstract A review of results on top quark physics expected at the photon linear colliders is presented.