Symmetries of Two Higgs Doublet Model and CP violation

We use the invariance of physical picture under a change of Lagrangian, the reparametrization invariance in the space of Lagrangians and its particular case -- the rephrasing invariance, for analysis of the two-Higgs-doublet extension of the SM. We found that some parameters of theory like tan beta are reparametrization dependent and therefore cannot be fundamental. We use the Z2-symmetry of the Lagrangian, which prevents a phi_1 phi_2 transitions, and the different levels of its violation, soft and hard, to describe a physical content of the model. In general, the broken Z2-symmetry allows for a CP violation in the physical Higgs sector. We argue that the 2HDM with a soft breaking of Z2-symmetry is a natural model in the description of EWSB. To simplify an analysis we choose among different forms of Lagrangian describing the same physical reality a specific one, in which the vacuum expectation values of both Higgs fields are real. A possible CP violation in the Higgs sector is described by using a two-step procedure with the first step identical to a diagonalization of mass matrix for CP-even fields in the CP conserved case. We find very simple necessary and sufficient condition for a CP violation in the Higgs sector. We determine the range of parameters for which CP violation and Flavor Changing Neutral Current effects are naturally small,what corresponds to a small dimensionless mass parameter nu= Re m_{12}^2/(2v1v2). We discuss how for small nu some Higgs bosons can be heavy, with mass up to about 0.6 TeV, without violating of the unitarity constraints. We discuss main features of the large nu case, which corresponds for nu -> infty to a decoupling of heavy Higgs bosons.Comment: 27 pages, extended discussion, references added, one figure, Revtex

Differential operators and Cherednik algebras

We establish a link between two geometric approaches to the representation theory of rational Cherednik algebras of type A: one based on a noncommutative Proj construction, used in [GS]; the other involving quantum hamiltonian reduction of an algebra of differential operators, used in [GG]. In the present paper, we combine these two points of view by showing that the process of hamiltonian reduction intertwines a naturally defined geometric twist functor on D-modules with the shift functor for the Cherednik algebra. That enables us to give a direct and relatively short proof of the key result, [GS, Theorem 1.4] without recourse to Haiman's deep results on the n! theorem. We also show that the characteristic cycles defined independently in these two approaches are equal, thereby confirming a conjecture from [GG].Comment: 37 p

Evolution of Universe to the present inert phase

We assume that current state of the Universe can be described by the Inert Doublet Model, containing two scalar doublets, one of which is responsible for EWSB and masses of particles and the second one having no couplings to fermions and being responsible for dark matter. We consider possible evolutions of the Universe to this state during cooling down of the Universe after inflation. We found that in the past Universe could pass through phase states having no DM candidate. In the evolution via such states in addition to a possible EWSB phase transition (2-nd order) the Universe sustained one 1-st order phase transition or two phase transitions of the 2-nd order.Comment: 19 pages, 3 figure

Oscillon resonances and creation of kinks in particle collisions

We present a numerical study of the process of production of kink-antikink pairs in the collision of particle-like states in the one-dimensional $\phi^4$ model. It is shown that there are 3 steps in the process, the first step is to excite the oscillon intermediate state in the particle collision, the second step is a resonance excitation of the oscillon by the incoming perturbations, and finally, the soliton-antisoliton pair can be created from the resonantly excited oscillon. It is shown that the process depends fractally on the amplitude of the perturbations and the wave number of the perturbation. We also present the effective collective coordinate model for this process.Comment: 4 pages, 4 figures, revtex

Determining Sneutrino Masses and Physical Implications

In some areas of supersymmetry parameter space, sneutrinos are lighter than the charginos and the next-to-lightest neutralino, and they decay into the invisible neutrino plus lightest-neutralino channel with probability one. In such a scenario they can be searched for in decays of charginos that are pair-produced in e+e- collisions, and in associated sneutrino-chargino production in photon-electron collisions. The sneutrino properties can be determined with high accuracy from the edges of the decay energy spectra in the first case and from threshold scans in the second. In the final part of the report we investigate the mass difference of sneutrinos and charged sleptons between the third and the first two generations in seesaw-type models of the neutrino/sneutrino sector. For a wide range these mass differences are sensitive to the seesaw scale.Comment: 20 p

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

Observation of Coherently-Enhanced Tunable Narrow-Band Terahertz Transition Radiation from a Relativistic Sub-Picosecond Electron Bunch Train

We experimentally demonstrate the production of narrow-band ($\delta f/f \simeq20$% at $f\simeq 0.5$ THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.Comment: 3 pages, 6 figure

Origin of Orthorhombic Transition, Magnetic Transition, and Shear Modulus Softening in Iron Pnictide Superconductors: Analysis based on the Orbital Fluctuation Theory

The main features in iron-pnictide superconductors are summarized as (i) the orthorhombic transition accompanied by remarkable softening of shear modulus, (ii) high-Tc superconductivity close to the orthorhombic phase, and (iii) stripe-type magnetic order induced by orthorhombicity. To present a unified explanation for them, we analyze the multiorbital Hubbard-Holstein model with Fe-ion optical phonons based on the orbital fluctuation theory. In the random-phase-approximation (RPA), a small electron-phonon coupling constant ($\lambda ~ 0.2$) is enough to produce large orbital (=charge quadrupole) fluctuations. The most divergent susceptibility is the $O_{xz}$-antiferro-quadrupole (AFQ) susceptibility, which causes the s-wave superconductivity without sign reversal (s_{++}-wave state). At the same time, divergent development of $O_{x2-y2}$-ferro-quadrupole (FQ) susceptibility is brought by the "two-orbiton process" with respect to the AFQ fluctuations, which is absent in the RPA. The derived FQ fluctuations cause the softening of $C_{66}$ shear modulus, and its long-range-order not only triggers the orthorhombic structure transition, but also induces the instability of stripe-type antiferro-magnetic state. In other words, the condensation of composite bosons made of two orbitons gives rise to the FQ order and structure transition. The theoretically predicted multi-orbital-criticality presents a unified explanation for abovementioned features of iron pnictide superconductors.Comment: 19 pages, 15 figure

Vortex Origin of Tricritical Point in Ginzburg-Landau Theory

Motivated by recent experimental progress in the critical regime of high-$T_c$ superconductors we show how the tricritical point in a superconductor can be derived from the Ginzburg-Landau theory as a consequence of vortex fluctuations. Our derivation explains why usual renormalization group arguments always produce a first-order transition, in contrast to experimental evidence and Monte Carlo simulations.Comment: 4 pages,1 figur

O(αs){\cal O}(\alpha_{s}) QCD and O(αew){\cal O}(\alpha_{ew}) electroweak corrections to ttˉh0t\bar{t}h^0 production in γγ\gamma \gamma collision

We calculate the ${\cal O}(\alpha_{s})$ QCD and ${\cal O}(\alpha_{{\rm ew}})$ electroweak one-loop corrections in the Standard Model framework, to the production of an intermediate Higgs boson associated with $t\bar{t}$ pair via $\gamma \gamma$ fusion at an electron-positron linear collider (LC). We find the ${\cal O}(\alpha_{s})$ QCD corrections can be larger than the ${\cal O}(\alpha_{{\rm ew}})$ electroweak ones, with the variations of the Higgs boson mass $m_{h}$ and $e^+e^-$ colliding energy $\sqrt{s}$. Both corrections may significantly decrease or increase the Born cross section. The numerical results show that the relative corrections from QCD to the process \eep may reach 34.8%, when $\sqrt{s}=800$ GeV and $m_h=200$ GeV, while those from electroweak can be -13.1%, -15.8% and -12.0%, at $\sqrt{s} = 800$ GeV, 1 TeV and 2 TeV respectively.Comment: 38 pages, 16 figure