Electroweak and Bottom Quark Contributions to Higgs Boson plus Jet Production

This paper presents predictions for jet pseudorapidity (eta) and transverse momentum (p_T) distributions for the production of the Standard Model Higgs boson in association with a high-p_T hadronic jet. We discuss the contributions of electroweak loops and of bottom-quark parton processes to the cross section. The latter arise in the five-flavour scheme. Predictions for the Tevatron and the Large Hadron Collider with 10 TeV collision energy are presented. For Higgs boson masses of 120 GeV, 160 GeV and 200 GeV, we find the maximal effects of the electroweak contributions to the Higgs plus jet p_T and eta distribution to be -14 % and -5.3 %, respectively, for the Tevatron, and -3 % and -2 %, respectively, for the LHC. For the maximal contribution of bottom-quark parton processes to the p_T and eta distribution, we find +3 % and + 2.5 %, respectively, for the Tevatron, and +3.5 % and +3 %, respectively, for the LHC. A separate study of the Higgs + b-jet cross section demonstrates that a calculational approach which respects the hierarchies of Yukawa couplings yields a leading order cross section prediction which is more accurate in the high-p_T regime than conventional approaches.Comment: 25 pages, 14 figure

On topological defect formation in the process of symmetry breaking phase transitions

By resorting to some results in quantum field theories with spontaneous breakdown of symmetry we show that an explanation based on microscopic dynamics can be given of the fact that topological defect formation is observed during the process of non-equilibrium phase transitions characterized by a non-zero order parameter. We show that the Nambu-Goldstone particle acquires an effective non-zero mass due to the boundary (finite volume) effects and this is related with the size of the defect. We also relate such volume effect with temperature effect.Comment: 12 pages, no figure

Bloch-Nordsieck Violation in Spontaneously Broken Abelian Theories

We point out that, in a spontaneously broken U(1) gauge theory, inclusive processes, whose primary particles are mass eigenstates that do not coincide with the gauge eigenstates, are not free of infrared logarithms. The charge mixing allowed by symmetry breaking and the ensuing Bloch-Nordsieck violation are here analyzed in a few relevant cases and in particular for processes initiated by longitudinal gauge bosons. Of particular interest is the example of weak hypercharge in the Standard Model where, in addition, left-right mixing effects arise in transversely polarized fermion beams.Comment: 4 pages, 1 figur

A viability criterion for modified gravity with an extra force

A recently proposed theory of modified gravity with an explicit ``anomalous'' coupling of the Ricci curvature to matter is discussed, and an inequality is derived which expresses a necessary and sufficient condition to avoid the notorius Dolgov-Kawasaki instability.Comment: 4 latex pages, to appear in Phys. Rev.

Gravitation Interaction and Electromagnetic Interaction in the Relativistic Universe with Total Zero and Local Non-Zero Energy

In the model of flat expansive homogeneous and isotropic relativistic universe with total zero and local non-zero energy the gravitation energy of bodies and the elecromagnetic energy of charged bodies can be localised.Comment: LaTeX, 10 pages, 1 figur

Quantum Oscillator on \DC P^n in a constant magnetic field

We construct the quantum oscillator interacting with a constant magnetic field on complex projective spaces \DC P^N, as well as on their non-compact counterparts, i. e. the $N-$dimensional Lobachewski spaces ${\cal L}_N$. We find the spectrum of this system and the complete basis of wavefunctions. Surprisingly, the inclusion of a magnetic field does not yield any qualitative change in the energy spectrum. For $N>1$ the magnetic field does not break the superintegrability of the system, whereas for N=1 it preserves the exact solvability of the system. We extend this results to the cones constructed over \DC P^N and ${\cal L}_N$, and perform the (Kustaanheimo-Stiefel) transformation of these systems to the three-dimensional Coulomb-like systems.Comment: 9 pages, 1 figur

Possibility of the new type phase transition

The scalar field theory and the scalar electrodynamics quantized in the flat gap are considered. The dynamical effects arising due to the boundary presence with two types of boundary conditions (BC) satisfied by scalar fields are studied. It is shown that while the Neumann BC lead to the usual scalar field mass generation, the Dirichlet BC give rise to the dynamical mechanism of spontaneous symmetry breaking. Due to the later, there arises the possibility of the new type phase transition from the normal to spontaneously broken phase. The decreasing in the characteristic size of the quantization region (the gap size here) and increasing in the temperature compete with each other, tending to transport the system in the spontaneously broken and in the normal phase, respectively. The system evolves with a combined parameter, simultaneously reflecting the change in temperature and in the size. As a result, at the critical value of this parameter there occurs the phase transition from the normal phase to the spontaneously broken one. In particular, the usual massless scalar electrodynamics transforms to the Higgs model

Probing the Higgs mechanism via γγ→W+W−\gamma\gamma\to W^+W^-

We investigate the sensitivity of the reaction $\gamma\gamma\to W^+W^-$ to the Higgs sector based on the complete one-loop corrections in the minimal Standard Model and the gauged non-linear $\sigma$-model. While this sensitivity is very strong for the suppressed cross-section of equally polarized photons and longitudinal W bosons, it is only marginal for the dominant mode of transverse polarizations. The corrections within the $\sigma$-model turn out to be UV-finite in accordance with the absence of \log\MH terms in the Standard Model with a heavy Higgs boson.Comment: 12 pages uuencoded postscrip

The Triple Higgs Boson Self-Coupling at Future Linear e+e- Colliders Energies: ILC and CLIC

We analyzed the triple Higgs boson self-coupling at future $e^{+}e^{-}$ colliders energies, with the reactions $e^{+}e^{-}\to b \bar b HH, t \bar t HH$. We evaluate the total cross-sections for both $b\bar bHH$ and $t\bar tHH$, and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple coupling $\kappa\lambda_{3H}$ within the range $\kappa=-1$ and +2. The numerical computation is done for the energies expected to be available at a possible Future Linear $e^{+}e^{-}$ Collider with a center-of-mass energy $800, 1000, 1500$ $GeV$ and a luminosity 1000 $fb^{-1}$. Our analysis is also extended to a center-of-mass energy 3 $TeV$ and luminosities of 1000 $fb^{-1}$ and 5000 $fb^{-1}$. We found that for the process $e^{+}e^{-}\to b \bar b HH$, the complete calculation differs only by 3% from the approximate calculation $e^{+}e^{-}\to ZHH(Z\to b\bar b)$, while for the process $e^{+}e^{-}\to t \bar tHH$, the expected number of events, considering the decay products of both $t$ and $H$, is not enough to obtain an accurate determination of the triple Higgs boson self-coupling.Comment: 19 pages, 12 figure

Higgs Radiation off Top Quarks at the Tevatron and the LHC

Higgs bosons can be searched for in the channels $p\bar p/pp\to t\bar tH+X$ at the Tevatron and the LHC. We have calculated the QCD corrections to these processes in the Standard Model at next-to-leading order. The higher-order corrections reduce the renormalization and factorization scale dependence considerably and stabilize the theoretical predictions for the cross sections. At the central scale $\mu=(2m_t+M_H)/2$ the properly defined $K$ factors are slightly below unity for the Tevatron ($K \sim 0.8$) and slightly above unity for the LHC ($K \sim 1.2$).Comment: 5 pages, latex, 2 figure