Large Scalar Couplings Research Articles

On the validity of perturbative studies of the electroweak phase transition in the Two Higgs Doublet model

Making use of a dimensionally-reduced effective theory at high temperature, we perform a nonperturbative study of the electroweak phase transition in the Two Higgs Doublet model. We focus on two phenomenologically allowed points in the parameter space, carrying out dynamical lattice simulations to determine the equilibrium properties of the transition. We discuss the shortcomings of conventional perturbative approaches based on the resummed effective potential — regarding the insufficient handling of infrared resummation but also the need to account for corrections beyond 1-loop order in the presence of large scalar couplings — and demonstrate that greater accuracy can be achieved with perturbative methods within the effective theory. We find that in the presence of very large scalar couplings, strong phase transitions cannot be reliably studied with any of the methods.

Unusually large scalar coupling between geminal protons in a saturated pyrimidine

AbstractAn unusually large geminal coupling has been observed in a stereochemically rigid system that permits a favorable coupling alignment between the methylene protons and an adjacent carbon‐carbon double bond. Such couplings have been found to depend on both the alignment of a line connecting the geminal hydrogens and the nodal plane of the adjacent double bond, and the orientation of lone‐pair electrons on adjacent heteroatoms. Electron withdrawal from symmetrical bonding orbitals results in more slightly positive geminal coupling constants while that from antisymmetrical bonding orbitals produces more negative coupling constants, which has been found to be very large in certain rigid systems.

Electroweak baryogenesis in a scalar-assisted vectorlike fermion model

We extend the standard model to a scalar-assisted vector-like fermion model to realize electroweak baryogenesis. The extended Cabbibo-Kobayashi-Maskawa matrix, due to the mixing among the vector-like quark and the standard model quarks, provides additional sources of the CP violation. Together with the enhancement from large vector-like quark mass, a large enough baryon-to-photon ratio could be obtained. The strongly first-order phase transition could be realized via the potential barrier which separate the broken minimum and the symmetric minimum in the scalar potential. We investigate in detail the one-loop temperature-dependent effective potential, and perform a random parameter scan to study the allowed parameter region that satisfies the strongly first order phase transition criteria $v_c \ge T_c$. Several distinct patterns of phase transition are classified and discussed. Among these patterns, large trilinear mass term between the Higgs boson and the scalar is preferred, for it controls the width of the potential barrier. Our results indicate large quartic scalar couplings, and moderate mixing angle between the Higgs boson and the new scalar. This parameter region could be further explored at the Run 2 LHC.

Three loop neutrino model with isolatedk±±

We propose a three loop radiative neutrino mass scenario with an isolated doubly charged singlet scalar $k^{\pm\pm}$ without couplings to the charged leptons, while two other singly charged scalars $h_1^\pm$ and $h_2^\pm$ attach to them. In this setup, the lepton flavor violation originating from $k^{\pm\pm}$ exchanges is suppressed and the model is less constrained, where some couplings can take sizable values. As reported in our previous work, the loop suppression factor at the three loop level would be too strong and realized neutrino masses in a three loop scenario could be smaller than the observed minuscule values. The sizable couplings can help us to enhance neutrino masses without drastically large scalar trilinear couplings appearing in a neutrino mass matrix, which tends to drive the vacuum stability to become jeopardized at the one loop level. Now the doubly charged scalar $k^{\pm\pm}$ has less constraint via lepton flavor violation and the vacuum can be quite stable, and thus a few hundred GeV mass in $k^{\pm\pm}$ is possible, which is within the LHC reach and this model can be tested in the near future. Note that the other $h_1^\pm$ and $h_2^\pm$ should be heavy at least around a few TeV. We suitably arrange the charges of an additional global $U(1)$ symmetry, where the decay constant of the associated Nambu-Goldstone boson can be around a TeV scale consistently. Also, this model is indirectly limited through a global analysis on results of the LHC Higgs search and issues on a dark matter candidate, the lightest Majorana neutrino. After $h_1^\pm$ and $h_2^\pm$ are decoupled, this particle couples to the standard model particles only through two charge parity even scalars in theory and thus information on this scalar sector is important. Consistent solutions are found, but a part of them is now on the edge.

LHC accessible second Higgs boson in the left-right model

A second Higgs doublet arises naturally as a parity partner of the standard model (SM) Higgs, once the SM is extended to its left-right symmetric version (LRSM) to understand the origin of parity violation in weak interactions, as well as to accommodate small neutrino masses via the seesaw mechanism. The flavor-changing neutral Higgs (FCNH) effects in the minimal version of this model (LRSM), however, push the second Higgs mass to more than 15 TeV, making it inaccessible at the LHC. Furthermore, since the second Higgs mass is directly linked to the ${W}_{R}$ mass, discovery of a ``low'' mass ${W}_{R}$ (${M}_{{W}_{R}}\ensuremath{\le}5--6\text{ }\text{ }\mathrm{TeV}$) at the LHC would require values for some Higgs self-couplings larger than 1. In this paper we present an extension of LRSM by adding a vectorlike $SU(2{)}_{R}$ quark doublet which weakens the FCNH constraints, allowing the second Higgs mass to be near or below the TeV range and a third neutral Higgs below 3 TeV for a ${W}_{R}$ mass below 5 TeV. It is then possible to search for these heavier Higgs bosons at the LHC without conflicting with FCNH constraints. A right-handed ${W}_{R}$ mass in the few TeV range is quite natural in this class of models without having to resort to large scalar coupling parameters. The CKM mixings are intimately linked to the vectorlike quark mixings with the known quarks, which is the main reason why the constraints on the second Higgs mass are relaxed. We present a detailed theoretical and phenomenological analysis of this extended left-right model and point out some tests as well as its potential for discovery of a second Higgs at the LHC. Two additional features of the model are a $5/3$-charged quark and a fermionic top partner with masses in the TeV range.

Gravitating axially-symmetric monopole-antimonopole configurations

We discuss static axially symmetric solutions of SU(2) Einstein-Yang-Mills-Higgs theory. These regular asymptotically flat solutions represent monopole-antimonopole chain and vortex ring solutions, as well as new configurations, present only for larger values of the scalar coupling λ. When gravity is coupled to the Yang-Mills-Higgs system, branches of gravitating solutions emerge from the flat-space solutions, and extend up to critical values of the gravitational coupling constant. For small scalar coupling only two branches of gravitating solutions exist, where the second branch connects to a generalized Bartnik-McKinnon solution. For large scalar coupling, however, a plethora of gravitating branches can be present and indicate the emergence of new flat-space branches.

Gravitating monopole-antimonopole systems at large scalar coupling

We discuss static axially symmetric solutions of SU(2) Einstein-Yang-Mills-Higgs theory for large scalar coupling A. These regular asymptotically flat solutions represent monopole-antimonopole chain and vortex ring solutions, as well as new configurations, present only for larger values of A. When gravity is coupled to the Yang-Mills-Higgs system, branches of gravitating solutions emerge from the flat-space solutions, and extend up to critical values of the gravitational coupling constant. For small scalar coupling only two branches of gravitating solutions exist, where the second branch connects to a generalized Bartnik-McKinnon solution. For large scalar coupling, however, a plethora of gravitating branches can be present and indicate the emergence of new flat-space branches.

Fractional 13C enrichment of isolated carbons using [1-13C]- or [2-13C]-glucose facilitates the accurate measurement of dynamics at backbone Cα and side-chain methyl positions in proteins

A simple labeling approach is presented based on protein expression in [1-(13)C]- or [2-(13)C]-glucose containing media that produces molecules enriched at methyl carbon positions or backbone C(alpha) sites, respectively. All of the methyl groups, with the exception of Thr and Ile(delta1) are produced with isolated (13)C spins (i.e., no (13)C-(13)C one bond couplings), facilitating studies of dynamics through the use of spin-spin relaxation experiments without artifacts introduced by evolution due to large homonuclear scalar couplings. Carbon-alpha sites are labeled without concomitant labeling at C(beta) positions for 17 of the common 20 amino acids and there are no cases for which (13)C(alpha)-(13)CO spin pairs are observed. A large number of probes are thus available for the study of protein dynamics with the results obtained complimenting those from more traditional backbone (15)N studies. The utility of the labeling is established by recording (13)C R (1rho) and CPMG-based experiments on a number of different protein systems.

Novel strategy for cerebral 13C MRS using very low RF power for proton decoupling

One of the major difficulties of in vivo 13C MRS is the need to decouple the large, one-bond, 1H-13C scalar couplings in order to obtain useful signal-to-noise ratios (SNRs) and spectral resolution at magnetic field strengths that are accessible to clinical studies. In this report a new strategy for in vivo cerebral 13C MRS is proposed. We realized that the turnover kinetics of glutamate (Glu) C5 from exogenous [2-(13)C]glucose (Glc) is identical to that of Glu C4 from exogenous [1-(13)C]Glc. The carboxylic/amide carbons are only coupled to protons via very weak long-range 1H-13C scalar couplings. As such, they can be effectively decoupled at very low RF power. Therefore, decoupling of the large 1H-13C scalar couplings can be avoided by the use of [2-(13)C]Glc. An additional advantage of this strategy is the lack of contamination from subcutaneous lipids because there are no overlapping fat signals in the vicinity of the Glu C5 and glutamine (Gln) C5 peaks. The feasibility of this strategy was demonstrated using 13C MRS on rhesus monkey brains at 4.7T.

Dynamics of metastable vacua in the early universe

We study the question whether a possible metastable vacuum state is actually populated in a phase transition in the early universe, as is usually assumed in the discussion of vacuum stability bounds e.g. for Standard Model parameters. A phenomenological (3+1)-dimensional Langevin equation is solved numerically for a toy model with a potential motivated by the finite temperature 1-loop effective potential of the Standard Model including additional non-renormalizable operators from an effective theory for physics beyond the Standard Model and a time dependent temperature. It turns out that whether the metastable vacuum is populated depends critically on the value of the phenomenological parameter η for small scalar couplings. For large enough scalar couplings and with our specific form of the non-renormalizable operators the system (governed by the Langevin equation) always ends up in the metastable minimum.

Scalar-gauge dynamics in (2+1) dimensions at small and large scalar couplings

We present the results of a detailed calculation of the excitation spectrum of states with quantum numbers J PC = 0 ++, 1 −− and 2 ++ in the three-dimensional SU(2) Higgs model at two values of the scalar self-coupling and for fixed gauge coupling. We study the properties of Polyakov loop operators, which serve to test the confining properties of the model in the symmetric phase. At both values of the scalar coupling we obtain masses of bound states consisting entirely of gauge degrees of freedom (glueballs), which are very close to those obtained in the pure gauge theory. We conclude that the previously observed, approximate decoupling of the scalar and gauge sectors of the theory persists at large scalar couplings. We study the crossover region at large scalar coupling and present a scenario how the confining properties of the model in the symmetric phase are lost inside the crossover by means of flux tube decay. We conclude that the underlying dynamics responsible for the observed dense spectrum of states in the Higgs region at large couplings must be different from that in the symmetric phase.

Relativistic transport theory ofN,Δ, andN*(1440) interacting throughσ,ω, andπmesons

A self-consistent relativistic integral-differential equation of the Boltzmann-Uehling-Uhlenbeck-type for the $N^{*}$(1440) resonance is developed based on an effective Lagrangian of baryons interacting through mesons. The closed time-path Green's function technique and semi-classical, quasi-particle and Born approximations are employed in the derivation. The non-equilibrium RBUU-type equation for the $N^{*}$(1440) is consistent with that of nucleon's and delta's which we derived before. Thus, we obtain a set of coupled equations for the $N$, $\Delta$ and $N^{*}$(1440) distribution functions. All the $N^{*}$(1440)-relevant in-medium two-body scattering cross sections within the $N$, $\Delta$ and $N^{*}$(1440) system are derived from the same effective Lagrangian in addition to the mean field and presented analytically, which can be directly used in the study of relativistic heavy-ion collisions. The theoretical prediction of the free $pp \to pp^{*}(1440)$ cross section is in good agreement with the experimental data. We calculate the in-medium $N + N \to N + N^{*}$, $N^{*} + N \to N + N$ and $N^{*} + N \to N^{*} + N$ cross sections in cold nuclear matter up to twice the nuclear matter density. The influence of different choices of the $N^{*}N^{*}$ coupling strengths, which can not be obtained through fitting certain experimental data, are discussed. The results show that the density dependence of predicted in-medium cross sections are sensitive to the $N^{*}N^{*}$ coupling strengths used. An evident density dependence will appear when a large scalar coupling strength of $g_{N^{*}N^{*}}^{\sigma}$ is assumed.

The Structure of Lyotropic Nematic Decylammoniumchloride and Bromide Systems by PMR of Monomethyltin Complexes and by Microscopic Studies

Abstract The pmr spectrum of methyltintrichloride in aqueous micellar solutions of decylammoniumchloride and KCl, and of decylammoniumbromide and KBr was investigated. The large scalar SnH couplings of 134.0 Hz and 130.2 Hz respectively indicate the formation of six coordination complexes CH3SnCl5 - - and CH3SnBr5 - - in the micellar solutions, but the geometrical structure of the CH3Sn moiety is little affected by the complex formation. The complexes orient with their symmetry axis preferably parallel to the nematic axis. In microscopic studies on selected mixtures a reversible first order phase transition was observed between nematic and isotropic micellar solution at about 45°C and a reversible transition between a lamellar smectic phase and the nematic phase at about 30°C that appears to be of second order. The optical observations and the orientation of the methyltin complex indicate that the nematic solutions have micelles of a bilayer structure.