The equivalent vector boson approximation for intermediate mass Higgs boson production

We consider the equivalent vector boson approximation (EVBA) for the processqq→qqWW→qqH andqq→qqZZ→qqH. It is shown that the contributions σT and σL, of the transversely and longitudinally polarized vector bosonsV respectively, are comparable with each other for intermediate values ofm _H viz. 0.3 TeV to 0.6 TeV. σT can be as large as 1.5–2 times σL in this mass range. As a result the leading EVBA for σ=σL+σT overestimates the exact total cross-section by a factor, upto 2–3 even, at high energies. σT is negligible with respect to the leading contribution σL only form _H≧0.6 TeV, where EVBA is correct within 15–20%. Further the effect of the corrections to EVBA, which are naively of nonleading order, on these conclusions in the framework of the EVBA is discussed.     

Vector boson decays of the Higgs boson

We derive the width of the Higgs boson into vector bosons. General formulas are derived both for the on–shell decay as well for the off–shell decays, and , where . For the off-shell decays the width of the decaying vector boson is properly included. The formulas are valid both for the Standard Model as well as for arbitrary extensions. As an example we study in detail the gauge-invariant effective Lagrangian models where we can have sizable enhancements over the Standard Model that could be observed at LEP. Received: 31 July 1998 / Revised version: 23 September 1998 / Published online: 6 November 1998     

Higgs boson production and weak boson structure

The influence of the QCD structure of the weak bosons on the Higgs boson production ine-p scattering is studied. The energy and Higgs boson mass dependence of the cross-section, following from the new contributions, is calculated. Work supported by the Polish State Committee for Scientifić Research (grant No. 2 P03B 081 09) and the Volkswagen-Stiftung     

Reweighing the evidence for a light Higgs boson in dileptonic W boson decays

We reconsider observables for discovering and measuring the mass of a Higgs boson via its dileptonic decays h → W W* → ?ν?ν. We define an observable generalizing the transverse mass that takes into account the fact that one of the intermediate W bosons is likely to be on shell. We compare this new variable with existing ones and argue that it gives a significant improvement for discovery in the region mh < 2 mW.     

Prospects for the search for a standard model Higgs boson in ATLAS using vector boson fusion

The European Physical Journal C - The potential for the discovery of a Standard Model Higgs boson in the mass range m H &lt; 2 m Z in the vector boson fusion mode has been studied for the ATLAS...     

Searching for a light Higgs boson

The Lindé-Weinberg bound [1] on the mass of the Higgs boson does not apply if one of the fermions of the standard model is very massive [2] or in non-standard models with multiple Higgs particles [1]. We consider both the standard model and a common extension thereof to two or more Higgs doublets. If the Higgs responsible for lepton masses is very light, one reliable method for indirectly detecting it would be a more careful measurement of g − 2 for the muon. More direct is the search for Higgs particles detected in association with τ pairs in existing or defunct e⁺e⁻ colliders operating well below the Z mass. We analyze both methods in detail, and find that data from several existing colliders could eliminate large portions of parameter space - or, perhaps, find the Higgs boson.     

Composite boson many-body theory for Frenkel excitons

We present a many-body theory for Frenkel excitons which takes into account their composite nature exactly. Our approach is based on four commutators similar to the ones we previously proposed for Wannier excitons. They allow us to calculate any physical quantity dealing with N excitons in terms of “Pauli scatterings” for carrier exchange in the absence of carrier interaction and “interaction scatterings” for carrier interactions in the absence of carrier exchange. We show that Frenkel excitons have a novel “transfer assisted exchange scattering”, specific to these excitons. It comes from indirect Coulomb processes between localized atomic states. These indirect processes, commonly called “electron-hole exchange” in the case of Wannier excitons and most often neglected, are crucial for Frenkel excitons, as they are the only ones responsible for the excitation transfer. We also show that in spite of the fact that Frenkel excitons are made of electrons and holes on the same atomic site, so that we could naively see them as elementary particles, they definitely are composite objects, their composite nature appearing through various properties, not always easy to guess. The present many-body theory for Frenkel excitons is thus going to appear as highly valuable to securely tackle their many-body physics, as in the case of nonlinear optical effects in organic semiconductors.     

Higgs boson cosmology

The discovery of the Standard Model Higgs boson opens up a range of speculative cosmological scenarios, from the formation of structure in the early universe immediately after the big bang, to relics from the electroweak phase transition one nanosecond after the big bang, on to the end of the present-day universe through vacuum decay. Higgs physics is wide ranging, and gives an impetus to go beyond the Standard Models of particle physics and cosmology to explore the physics of ultra-high energies and quantum gravity.     

Normal forms for classical and boson systems

The group of Bogoliubov transformations of annihilation and creation operators is a subgroup of U(n,n) where n is the number of distinct pairs of annihilation and creation operators. Here, it is established that this subgroup of U(n,n) is isomorphic to Sp(2n,$\text{R}$), which appears in classical dynamics as the group of linear canonical transformations on a 2n-dimensional phase space. Well-known results in classical dynamics are then to used to deduce the full set of normal forms for Boson Hamiltonians. These are classified using a para-eigenvalue notation applicable to both classical and Bose field systems. A simple sufficient condition is given for the non-removability of pairs of creation operators. Explicit normal forms have not previously been given for Hamiltonians with this pathology, which may occur even when the corresponding classical Hamiltonian can be diagonalized.     

A new boson expansion for odd-particle systems

The Beliaev-Zelevinsky boson expansion is extended to include systems with odd particle number. Closed forms, valid to all orders, are given for the particle-boson as well as boson-boson interaction.     

Compact boson stars

We consider compact boson stars that arise for a V-shaped scalar field potential. They represent a one parameter family of solutions of the scaled Einstein–signum–Gordon equations. We analyze the physical properties of these solutions and determine their domain of existence. Along their physically relevant branch emerging from the compact Q-ball solution, their mass increases with increasing radius. Employing arguments from catastrophe theory we argue that this branch is stable, until the maximal value of the mass is reached. There the mass and size are on the order of magnitude of the Schwarzschild limit, and thus the spiraling respectively oscillating behaviour, well known for compact stars, sets in.     

Dyson-type boson mapping and SU(6) boson model

The Dyson-type boson mapping is applied to realistic cases to show that it is a very promising method for describing nuclear collective motion. Eigenvectors are obtained in the corresponding hermitian boson theory from the results of right- and left-hand-side eigenvalue problems in the Dyson boson theory. The numerical results are compared with those of the SU(6) boson model and exact quasiparticle shell-model calculations within the multi-phonon subspace.     

Search for Z* boson at ATLAS detector

We present the results of the search for new excited Z* boson at ATLAS detector in 2011. Results are based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb^?1 in the dielectron channel and 5.0 fb^?1 in the dimuon channel. Since good agreement between experimental data and expectation of the Standard Model is observed in both channels, the existence of Z* is excluded with 95 percent confidence level for all masses below 2.20 TeV. The plans for Z* search in 2012 are discussed.     

Interacting boson approximation for two-quasiparticle and collective states

The boson-fermion mapping problem is investigated for the case when pure collective quadrupole and two-quasiparticle modes are considered. Approximate expressions of the boson images of the fermion operators are derived.Dedicated to the memory of M. Gmitro.     

Correlation functions for a strongly correlated boson system

The correlation functions for a strongly correlated exactly solvable one-dimensional boson system on a finite chain as well as in the thermodynamic limit are calculated explicitly. This system, which we call the phase model, is the strong coupling limit of the integrable q-boson hopping model. The results are presented as determinants.     

非线性两模玻色子系统的Majorana表象

利用Majorana表象,从平均场模型和二次量子化模型两方面研究了非线性双模玻色子系统的动力学问题.得到了Majorana点在球面上的运动方程,分析了平均场模型和二次量子化模型之间的区别及其在Majorana点运动方程中的体现.研究了二次量子化模型中量子态在少体和多体情况下的动力学演化及其与平均场量子态的区别和联系.以平均场模型和二次量子化模型量子态之间的保真度和Majorana点之间的关联为手段,讨论了在不同玻色子间相互作用强度、不同玻色子数下量子态的演化及相应的自囚禁效应.