Radiatively generated maximal mixing scenario for the Higgs boson mass and the least fine-tuned minimal supersymmetric standard model

We argue that given the experimental constraints on the Higgs boson mass the least fine-tuned parameter space of the minimal supersymmetric standard model is with negative top-squark masses squared at the grand unification scale. While the top-squark mass squared is typically driven to positive values at the weak scale, the contribution to the Higgs boson mass squared parameter from the running can be arbitrarily small, which reduces the fine-tuning of electroweak symmetry breaking. At the same time the top-squark mixing is necessarily enhanced and the maximal mixing scenario for the Higgs boson mass can be generated radiatively even when starting with negligible mixing at the unification scale. This highly alleviates constraints on possible models for supersymmetry breaking in which fine-tuning is absent.     

Search for the Higgs boson in events with missing transverse energy and b quark jets produced in pp collisions at square root(s)=1.96 TeV

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use approximately 1 fb(-1) integrated luminosity of pp collisions at square root(s)=1.96 TeV recorded by the Collider Detector at Fermilab II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248+/-43 (14.4+/-2.7) are expected from standard model background processes. We observe no significant excess over the expected background and thus set 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 to 140 GeV/c(2). For a mass of 115 GeV/c(2), the observed (expected) limit is 20.4 (14.2) times the standard model prediction.     

The weak bound state with the non-zero charge density as the LHC 126.5 GeV state

The self-consistent model of classical field interactions formulated as the counterpart of the quantum electroweak model leads to homogeneous boson ground state solutions in presence of non-zero extended fermionic charge density fluctuations. Two different types of electroweak configurations of fields are analyzed. The first one has non-zero electric and weak charge fluctuations. The second one is electrically uncharged but weakly charged. Both types of configurations have two physically interesting solutions which possess masses equal to 126.67 GeV at the value of the scalar fluctuation potential parameter λ equal to ~0.0652. The spin zero electrically uncharged droplet formed as a result of the decay of the charged one is interpreted as the ~126.5 GeV state found in the Large Hadron Collider (LHC) experiment. (The other two configurations correspond to solutions with masses equal to 123.7 GeV and λ equal to ~0.0498 and thus the algebraic mean of the masses of two central solutions, i.e., 126.67 GeV and 123.7 GeV, is equal to 125.185 GeV.) The problem of a mass of this kind of droplets will be considered on the basis of the phenomenon of the screening of the fluctuation of charges. Their masses are found in the thin wall approximation.     

First-order electroweak phase transition powered by additional F-term loop effects in an extended supersymmetric Higgs sector

We investigate the one-loop effect of new charged scalar bosons on the Higgs potential at finite temperatures in the supersymmetric standard model with four Higgs doublet chiral superfields as well as a pair of charged singlet chiral superfields. In this model, the mass of the lightest Higgs boson h is determined only by the D-term in the Higgs potential at the tree-level, while the triple Higgs boson coupling for hhh can receive a significant radiative correction due to nondecoupling one-loop contributions of the additional charged scalar bosons. We find that the same nondecoupling mechanism can also contribute to realize stronger first order electroweak phase transition than that in the minimal supersymmetric standard model, which is definitely required for a successful scenario of electroweak baryogenesis. Therefore, this model can be a new candidate for a model in which the baryon asymmetry of the Universe is explained at the electroweak scale.     

A minimalSU(2)×U(1)×U(1) electroweak model with mirror fermions

We present a minimal extension of the standard electroweak model, which accommodates mirror fermions, based onSU(2)×U(1)×U(1). Mirror mixing happens through sterile neutrino states and induces radiative mixing for charged leptons. Quarks and mirror quarks are not mixed with each other, consistent with the suppression of flavour changing neutral currents. Higgs sector, fermion masses and neutral currents are discussed. In this scheme there can be a secondZ boson as light as 0.2TeV.     

Integrating out the standard Higgs field in the path integral

We integrate out the Higgs boson in the electroweak standard model at one loop and construct a low-energy effective Lagrangian assuming that the Higgs mass is much larger than the gauge-boson masses. Instead of applying diagrammatical techniques, we integrate out the Higgs boson directly in the path integral, which turns out to be much simpler. By using the background-field method and the Stueckelberg formalism, we directly find a manifestly gauge-invariant result. The heavy-Higgs effects on fermionic couplings are derived, too. At one loop the log M_H terms of the heavy-Higgs limit of the electroweak standard model coincide with the UV-divergent terms in the gauged non-linear σ-model, but vertex functions differ in addition by finite constant terms. Finally, the leading Higgs effects to some physical processes are calculated from the effective Lagrangian.     

Resummation of angular dependent corrections in spontaneously broken gauge theories

Recent investigations of electroweak radiative corrections have revealed the importance of higher order contributions in high energy processes, where the size of typical corrections can exceed those associated with QCD considerably. Beyond one loop, only universal (angular independent) corrections are known to all orders except for massless processes, where also angle dependent corrections exist in the literature. In this paper we present general arguments for the consistent resummation of angle dependent subleading (SL) logarithmic corrections to all orders in the regime where all invariants are still large compared to the gauge boson masses. We discuss soft isospin correlations, fermion mass and gauge boson mass gap effects, the longitudinal and Higgs boson sector as well as mixing contributions including CKM effects for massive quarks. Two loop results for the right handed Standard Model are generalized in the context of the high energy effective theory based on the standard model Lagrangian in the symmetric basis with the appropriate matching conditions to include the soft QED regime. The result is expressed in exponentiated operator form in a CKM extended isospin space in the symmetric basis. Thus, a full electroweak SL treatment based on the infrared evolution equation method is formulated for arbitrary high energy processes at future colliders. Comparisons with known results are presented. Received: 12 February 2002 / Revised version: 7 March 2002 / Published online: 8 May 2002     

Indirect bounds on heavy scalar masses of the two-Higgs-doublet model in light of recent Higgs boson searches

We study an upper bound on masses of additional scalar bosons from the electroweak precision data and theoretical constraints such as perturbative unitarity and vacuum stability in the two-Higgs-doublet model taking account of recent Higgs boson search results. If the mass of the Standard-Model-like Higgs boson is rather heavy and is outside the allowed region by the electroweak precision data, such a discrepancy should be compensated by contributions from the additional scalar bosons. We show the upper bound on masses of the additional scalar bosons to be about 2 (1) TeV for the mass of the Standard-Model-like Higgs boson to be 240 (500) GeV.     

Effects of a non-standardW ± magnetic moment inW ± production via deep inelastice −P scattering

We calculate the production of charged bosons in deep inelastice ^?P scattering in the context of an electroweak model in which the vector boson self interactions may be different from those prescribed by the electroweak standard model. We present results which show the dependence of the cross section on the anomalous magnetic dipole moment κ of theW ^±. We find for energies available at HERA that even small deviations from the standard model value of κ imply observable deviations in theW ^± production rates. We also show that the contributions from heavy boson exchange diagrams are very important.     

Six-quark decays of the Higgs boson in supersymmetry with R-parity violation

Both electroweak precision measurements and simple supersymmetric extensions of the standard model prefer a mass of the Higgs boson less than the experimental lower limit (on a standard-model-like Higgs boson) of 114 GeV. We show that supersymmetric models with R parity violation and baryon-number violation have a significant range of parameter space in which the Higgs boson dominantly decays to six jets. These decays are much more weakly constrained by current CERN LEP analyses and would allow for a Higgs boson mass near that of the Z. In general, lighter scalar quark and other superpartner masses are allowed. The Higgs boson would potentially be discovered at hadron colliders via the appearance of new displaced vertices.     

Modified Yang-Mills Theory and Electroweak Interactions

Since the Higgs boson of the standard electroweak model has not been detecteddespite many experimental attempts, nonstandard electroweak models notincluding the Higgs boson may be worthy of consideration; one of them isproposed here. This new model of electroweak interactions is based on theYang-Mills theory completed by a nontrivial condition at infinity for theYang-Mills potentials corresponding to the zero-field intensities. It is shown thatwithin the framework of this model the three vector potentials of the Yang-Millstheory allow one to describe both the Maxwell electromagnetic interactions andthe Fermi weak interactions and to obtain the known value of the Z ⁰ boson mass.     

Lepton mixing matrix in standard model extended by one sterile neutrino

We consider the simplest extension of the standard electroweak model by one sterile neutrino that allows for neutrino masses and mixing. We find that its leptonic sector contains much less free physical parameters than previously realized. In addition to the two neutrino masses, the lepton mixing matrix in charged current interactions involves (n-1) free physical mixing angles for n generations. The mixing matrix in neutral current interactions of neutrinos is completely fixed by the two masses. Both interactions conserve CP. We illustrate the phenomenological implications of the model by vacuum neutrino oscillations, tritium β decay and neutrinoless double β decay. It turns out that, due to the revealed specific structure in its mixing matrix, the model with any n generations cannot accommodate simultaneously the data by KamLAND, K2K and CHOOZ. PACS 14.60.Pq; 14.60.St; 23.40.-s     

Higgs and neutrino sector,EDM and ε<Subscript>K</Subscript> in a spontaneously CP and R-parity breaking supersymmetric model

We construct an extension of the supersymmetric standard model where both CP symmetry and R-parity are spontaneously broken. We study the electroweak symmetry breaking sector of the model and find minima consistent with the experimental bounds on Higgs boson masses. Neutrino masses and mixing angles are generated through both seesaw and bilinear R-parity violation. We show that the hierarchical mass pattern is obtained, and mixings are consistent with measured values. Due to the spontaneous CP and R-parity violation, the neutrino sector is CP violating, and we calculate the corresponding phase. We further restrict the parameter space to agree with the limits on the electric dipole moment of the neutron. Finally, we study the CP violation parameter ε_K in the kaon system and show that we obtain results consistent with the experimental value.     

Quantum corrections from nonresonant WW scattering

An estimate is presented of the leading radiative corrections to low energy electroweak precision measurements from strong nonresonant WW scattering at the TeV energy scale. The estimate is based on a novel representation of nonresonant scattering in terms of the exchange of an effective scalar propagator with simple poles in the complex energy plane. The resulting corrections have the form of the corrections from the standard model Higgs boson with the mass set to the unitarity scale for strong WW scattering.     

Superconformal technicolor

In supersymmetric theories with a strong conformal sector, soft supersymmetry breaking at the TeV scale naturally gives rise to confinement and chiral symmetry breaking at the same scale. We consider two such scenarios, one where the strong dynamics induces vacuum expectation values for elementary Higgs fields, and another where the strong dynamics is solely responsible for electroweak symmetry breaking. In both cases, the mass of the Higgs boson can exceed the LEP bound without tuning, solving the supersymmetry naturalness problem. A good precision electroweak fit can be obtained, and quark and lepton masses are generated without flavor-changing neutral currents. In addition to standard supersymmetry signals, these models predict production of multiple heavy standard model particles (t, W, Z, and b) from decays of resonances in the strong sector.     

Subgroup alignment in hypercolor theories

To analyze the physical consequences of a dynamically broken theory of the weak interactions, we must know how the weak gauge group is aligned in an approximate flavor-symmetry group. For a large class of models, spectral-function sum rules enables us to determine this alignment explicitly. We work out the pattern of the electroweak symmetry breakdown for several sample models. Critical values of weak mixing angles are found at which the breakdown pattern changes discontinously. We compute pseudo-Goldstone boson masses, and find that some models contain unusually light charged or colored pseudo-Goldstone bosons.     

The polarization-asymmetry correlation of107In and parity violation

We report on the first measurements of the longitudinal polarization of positrons emitted by polarized nuclei, using cryogenically polarized¹⁰⁷In. This so-called polarization-asymmetry correlation is very sensitive to the mass of a possible right-handed gauge boson, which is invoked by parity symmetric extensions of the standard V-A electroweak model to explain the experimentally observed strong violation of parity which, however, may not be complete. The positron polarization is deduced from the time-resolved decay spectrum of positronium hyperfine states. Our preliminary result points to a lower limit of about 210 GeV for the mass of an eventual right-handed charged W gauge boson. This result can still be improved.     

Electroweak precision constraints on vector-like fermions

We calculate the oblique electroweak corrections and confront them with the experiments in an extension of the standard model. The new fields added are a vector-like weak doublet and a singlet fermion. After electroweak symmetry breaking there is a mixing between the components of the new fields, but there is no mixing allowed with the standard fermions. Four electroweak parameters, , , W and Y, are presented in the formalism of Barbieri et al.; these are the generalization of the Peskin–Takeuchi S, T and U. The vector-like extension is slightly constrained. requires the new neutral fermion masses not to be very far from each other, allowing for higher mass differences for higher masses and smaller mixing. , W and Y give practically no constraints on the masses. This extension can give a positive contribution to , allowing for a heavy Higgs boson in electroweak precision tests of the standard model.     

Natural electroweak breaking from a mirror symmetry

We present "twin Higgs models," simple realizations of the Higgs boson as a pseudo Goldstone boson that protect the weak scale from radiative corrections up to scales of order 5-10 TeV. In the ultraviolet these theories have a discrete symmetry which interchanges each standard model particle with a corresponding particle which transforms under a twin or a mirror standard model gauge group. In addition, the Higgs sector respects an approximate global symmetry. When this global symmetry is broken, the discrete symmetry tightly constrains the form of corrections to the pseudo Goldstone Higgs potential, allowing natural electroweak symmetry breaking. Precision electroweak constraints are satisfied by construction. These models demonstrate that, contrary to the conventional wisdom, stabilizing the weak scale does not require new light particles charged under the standard model gauge groups.     

Nambu's Nobel Prize,the meson and the mass of visible matter

The electroweak Higgs boson has been discovered in ongoing experiments at the LHC, leading to a mass of this particle of 126 GeV. This Higgs boson mediates the generation of mass for elementary particles, including the mass of elementary (current) quarks. These current‐quark masses leave 98% of the mass of the atom unexplained. This large fraction is mediated by strong interaction, where instead of the Higgs boson the σ meson is the mediating particle. Though already introduced in 1957 by Schwinger, the σ meson has been integrated out in many theories of hadron properties because it had not been observed and was doubted to exist. With the observation of the σ meson in recent experiments on Compton scattering by the nucleon at MAMI (Mainz) it has become timely to review the status of experimental and theoretical researches on this topic.