Determination of the Higgs-boson couplings and H-A mixing in the generalized SM-like Two Higgs Doublet Model

The feasibility of measuring the Higgs-boson properties at the Photon Collider at TESLA has been studied in detail for masses between 200 and 350 GeV, using realistic luminosity spectra and detector simulation. We consider the Two Higgs Doublet Model (II) with SM-like Yukawa couplings for h, parametrized by only one parameter (tan(beta)). The combined measurement of the invariant-mass distributions in the ZZ and W+W- decay-channels is sensitive to both the two-photon width Gamma_{gamma gamma} and phase Phi_{gamma gamma}. From the analysis including systematic uncertainties we found out that after one year of Photon Collider running with nominal luminosity the expected precision in the measurement of tan(beta) is of the order of 10%, for both light (h) and heavy (H) scalar Higgs bosons. The H-A mixing angle Phi_{HA}, characterizing a weak CP violation in the model with two Higgs doublets, can be determined to about 100 mrad, for low tan(beta).Comment: 17 pages, 9 figures; published versio

Precision Mass Determination of the Higgs Boson at Photon-Photon Colliders

We demonstrate a measurement of the Higgs boson mass by the method of energy scanning at photon-photon colliders, using the high energy edge of the photon spectrum. With an integrated luminosity of 50 $\rm{fb^{-1}}$ it is possible to measure the standard model Higgs mass to within 110 MeV in photon-photon collisions for m_h=100 GeV. As for the total width of the Higgs boson, the statistical error $\Delta\Gamma_h/\Gamma_{h \rm{SM}}=0.06$ is expected for m_h=100 GeV, if both $\Gamma(h\to\gamma\gamma)$ and $\Gamma(h\to b\bar{b})$ are fixed at the predicted standard model value.Comment: 7 pages, 4 figures, Given at 3nd International Workshop on Electron-Electron Interactions at TeV Energies, Dec 10-12, Santa Cruz, California, 199

Study of the Higgs-boson decays into WW and ZZ at the Photon Collider

Production of the Standard Model Higgs-boson at the Photon Collider at TESLA is studied for the Higgs-boson masses above 150 GeV. Simulation of signal and background processes takes into account realistic luminosity spectra and detector effects. In the considered mass range, large interference effects are expected in the W+W- decay channel. By reconstructing W+W- and ZZ final states, not only the h->gamma gamma partial width can be measured, but also the relative phase of the scattering amplitude. This opens a new window for the precise determination of the Higgs-boson couplings. Models with heavy, fourth-generation fermions and with enlarged Higgs sector (2HDM (II)) are considered.Comment: 19 pages, 18 figures; updated version with improved precision of estimate

Discovery limits for Techni-Omega production in eγe\gamma Collisions

In a strongly-interacting electroweak sector with an isosinglet vector state, such as the techni-omega, $\omega_T$, the direct $\omega_T Z \gamma$ coupling implies that an $\omega_T$ can be produced by $Z \gamma$ fusion in $e \gamma$ collisions. This is a unique feature for high energy $e^+e^-$ or $e^-e^-$ colliders operating in an $e\gamma$ mode. We consider the processes $e^- \gamma \to e^- Z\gamma$ and $e^- \gamma \to e^- W^+ W^- Z$, both of which proceed via an intermediate $\omega_T$. We find that at a 1.5 TeV $e^+e^-$ linear collider operating in an $e\gamma$ mode with an integrated luminosity of 200 fb$^{-1}$, we can discover an $\omega_T$ for a broad range of masses and widths.Comment: To appear in the Proceedings of the 29th International Conference on High Energy Physics, Vancouver, July 1998, 5 pages, Latex, 7 postscript figure

Partially composite two-Higgs doublet model

In the extra dimensional scenarios with gauge fields in the bulk, the Kaluza-Klein (KK) gauge bosons can induce Nambu-Jona-Lasinio (NJL) type attractive four-fermion interactions, which can break electroweak symmetry dynamically with accompanying composite Higgs fields. We consider a possibility that electroweak symmetry breaking (EWSB) is triggered by both a fundamental Higgs and a composite Higgs arising in a dynamical symmetry breaking mechanism induced by a new strong dynamics. The resulting Higgs sector is a partially composite two-Higgs doublet model with specific boundary conditions on the coupling and mass parameters originating at a compositeness scale $\Lambda$. The phenomenology of this model is discussed including the collider phenomenology at LHC and ILC.Comment: 20 pages, 7 figure

Necessity of mixed kinetic term in the description of general system with identical fields

Most general renormalizable interaction in the system with a set of scalar fields having identical quantum numbers generates naturally mixed kinetic terms in the Lagrangian. Taking into account these terms leads to modification both the renormalization group equations and the tree level analysis as compare with many published results. We obtain conditions for non-appearance of such a running mixing in some important cases.Comment: 12 pages, 3 figure

Large contribution of virtual Delbrueck scattering to the emission of photons by relativistic nuclei in nucleus-nucleus and electron-nucleus collisions

Delbrueck scattering is an elastic scattering of a photon in the Coulomb field of a nucleus via a virtual electron loop. The contribution of this virtual subprocess to the emission of a photon in the collision of ultra-relativistic nuclei Z_1 Z_2 -> Z_1 Z_2 gamma is considered. We identify the incoming virtual photon as being generated by one of the relativistic nuclei involved in the binary collision and the scattered photon as being emitted in the process. The energy and angular distributions of the photons are calculated. The discussed process has no infrared divergence. The total cross section obtained is 14 barn for Au-Au collisions at the RHIC collider and 50 barn for Pb-Pb collisions at the LHC collider. These cross sections are considerably larger than those for ordinary tree-level nuclear bremsstrahlung in the considered photon energy range m_e << E_\gamma << m_e gamma, where gamma is the Lorentz factor of the nucleus. Finally, photon emission in electron-nucleus collisions e Z -> e Z gamma is discussed in the context of the eRHIC option.Comment: 10 pages; 7 figure

Inverse Neutrinoless Double Beta Decay Revisited

We critically reexamine the prospects for the observation of the $\Delta L=2$ lepton-number-violating process \eeWW using the $e^-e^-$ option of a high-energy $e^+e^-$ collider (NLC). We find that, except in the most contrived scenarios, constraints from neutrinoless double beta decay render the process unobservable at an NLC of $\sqrt{s}<2$ TeV. Other $\Delta L=2$ processes such as \ggllww, \egnllw, \eennll ($\ell=\mu,\tau$), and \egeww, which use various options of the NLC, require a $\sqrt{s}$ of at least 4 TeV for observability.Comment: paper in LATEX, 24 pages, 10 figures in separate uuencoded psfile. Complete psfile available via anonymous ftp at ftp://lapphp0.in2p3.fr/pub/preprints-theorie/doublebeta.uu or via www at http://lapphp0.in2p3.fr/preplapp/psth/doublebeta.ps.g

Using Scalars to Probe Theories of Low Scale Quantum Gravity

Arkani-Hamed, Dimopoulos and Dvali have recently suggested that gravity may become strong at energies near 1 TeV which would remove the hierarchy problem. Such a scenario can be tested at present and future colliders since the exchange of towers of Kaluza-Klein gravitons leads to a set of new dimension-8 operators that can play important phenomenological roles. In this paper we examine how the production of pairs of scalars at $e^+e^-$, $\gamma \gamma$ and hadron colliders can be used to further probe the effects of graviton tower exchange. In particular we examine the tree-level production of pairs of identical Higgs fields which occurs only at the loop level in both the Standard Model and its extension to the Minimal Supersymmetric Standard Model. Cross sections for such processes are found to be potentially large at the LHC and the next generation of linear colliders. For the $\gamma\gamma$ case the role of polarization in improving sensitivity to graviton exchange is emphasized.Comment: 32 pages, 12 figures, latex, remarks added to tex

ZZγZZ\gamma and ZγγZ\gamma\gamma couplings in γe\gamma e collision with polarized beams

The potential of $\gamma$e mode of linear $e^{+}e^{-}$ collider to probe $ZZ\gamma$ and $Z\gamma\gamma$ vertices is investigated through the Z boson production from the procees $\gamma e\to Z e$. Considering the longitudinal and transverse polarization states of the Z boson and incoming polarized beams we find the 95% C.L. limits on the form factors $h_{3}^{Z}$, $h_{4}^{Z}$, $h_{3}^{\gamma}$ and $h_{4}^{\gamma}$ with integrated luminosity 500$fb^{-1}$ and $\sqrt{s}=$0.5, 1, 1.5 TeV energies. It is shown that the polarization can improve sensitivities by factors 2-3 depending on the energy.Comment: 12 pages, 8 EPS figure