Massive Gauge Bosons Research Articles

Leptogenesis constraints on the mass of right-handed gauge bosons

We discuss leptogenesis constraints on the mass of the right-handed $W$ boson (${W}_{R}$) in a TeV-scale left-right seesaw model for neutrino masses. For generic Dirac mass of the neutrinos, i.e. with all Yukawa couplings $\ensuremath{\lesssim}1{0}^{\ensuremath{-}5.5}$, it has been pointed out that successful leptogenesis requires a lower bound of 18 TeV on the ${W}_{R}$ mass, pushing it beyond the reach of the LHC. Such TeV-scale left-right seesaw model must, however, be parity asymmetric for type-I seesaw to give the observed neutrino masses. This class of models can accommodate larger Yukawa couplings, which give simultaneous fits to charged-lepton and neutrino masses, by invoking either cancellations or specific symmetry textures for Dirac (${M}_{D}$) and Majorana (${M}_{N}$) masses in the seesaw formula. We show that in this case the leptogenesis bound on ${M}_{{W}_{R}}$ can be substantially weaker, i.e. ${M}_{{W}_{R}}\ensuremath{\gtrsim}3\text{ }\text{ }\mathrm{TeV}$ for ${M}_{N}\ensuremath{\lesssim}{M}_{{W}_{R}}$. This happens due to considerable reduction of the dilution effects from ${W}_{R}$-mediated decays and scatterings, while the washout effects due to inverse decays are under control for certain parameter ranges of the Yukawa couplings. We also show that this model is consistent with all other low-energy constraints, such as lepton flavor violation and neutrinoless double beta decay. Thus, a discovery of the right-handed gauge bosons alone at the LHC will not falsify leptogenesis as the mechanism behind the matter-antimatter asymmetry in our Universe.

Scalar dark matter with CERN-LEP data andZ′search at the LHC in anU(1)′model

In the framework of an nonuniversal $U(1)'$ extension of the standard model, we propose an scalar candidate for cold dark matter which exhibits interactions with ordinary matter through Higgs and gauge bosons. Using limits from low energy observables, we find constraints on the new physics parameters of the model associated to the extra abelian symmetry, in particular, the mass of the additional neutral gauge boson $Z'$ and the new gauge coupling constant. We found that for the lower experimental limit $M_{Z'}=3$ TeV constrained by direct research at LHC, the ratio between the $U(1)'$ and $SU(2)_L$ gauge coupling constants is around $0.4$. Taking into account this limit and the observable relic density of the Universe, we search for new constraints on the mass of the dark matter particle of the model. We found that for a higgsphobic model, the mass of the scalar dark matter must be $M_{\sigma}=70$ GeV. We also found different kinematical threshold and resonances that enhance the dispersion of dark matter into ordinary matter for different regions of the space of parameters of the model, obtaining masses as low as $1.3$ GeV and as large as $125$ GeV with not allowed intermediate regions due to resonances.

Lowest limits on the doubly charged Higgs boson masses in the minimal left-right symmetric model

The doubly charged Higgs bosons ${H}_{1,2}^{\ifmmode\pm\else\textpm\fi{}\ifmmode\pm\else\textpm\fi{}}$ would undoubtedly be clear messengers of the new physics. We discuss their mass spectrum and show how experimental data and relations between scalar masses put limits on it. In particular, both the masses of the particles ${H}_{1}^{0}$, ${A}_{1}^{0}$ that play a crucial role in flavor changing neutral current effects and the masses of the additional gauge bosons ${W}_{2}$, ${Z}_{2}$ are notably important. For instance, if ${M}_{{H}_{1}^{0},{A}_{1}^{0}}\ensuremath{\simeq}15\text{ }\text{ }\mathrm{TeV}$ and ${M}_{{W}_{2}}\ensuremath{\simeq}3.76\text{ }\text{ }\mathrm{TeV}$, then the lowest mass of ${H}_{1}^{\ifmmode\pm\else\textpm\fi{}\ifmmode\pm\else\textpm\fi{}}$ is 465 GeV. In contrast, because of the freedom in the parameter space of the full scalar potential, there is no lowest limit on the mass of ${H}_{2}^{\ifmmode\pm\else\textpm\fi{}\ifmmode\pm\else\textpm\fi{}}$. It is shown to which signals at hadron colliders such relatively light doubly charged scalars might correspond. LHC working at $\sqrt{s}=14\text{ }\text{ }\mathrm{TeV}$ will enter into the region where the existence of such particles with minimal masses can be thoroughly explored for a much wider parameter space of the minimal and manifest version of the left-right symmetric model (MLRSM). Taking into account our considerations and present ATLAS and CMS exclusion limits on ${M}_{{H}^{\ifmmode\pm\else\textpm\fi{}\ifmmode\pm\else\textpm\fi{}}}$, there exist already first partial bounds on some of the MLRSM scalar potential parameters.

Influence of gauge boson mass on the staggered spin susceptibility

Based on the study of the linear response of the fermion propagator in the presence of an external scalar field, we calculate the staggered spin susceptibility in the low-energy limit in the framework of the Dyson-Schwinger approach. We analyze the effect of a finite gauge boson mass on the staggered spin susceptibility in both the Nambu phase and the Wigner phase. It is found that the gauge boson mass suppresses the staggered spin susceptibility in the Wigner phase. In addition, we try to give an explanation for why the antiferromagnetic spin correlation increases when the doping is lowered.

Higgs-flavon mixing and LHC phenomenology in a simplified model of broken flavor symmetry

The LHC phenomenology of a low-scale gauged flavor symmetry model with inverted hierarchy is studied, through introduction of a simplified model of broken flavor symmetry. A new scalar (a flavon) and a new neutral top-philic massive gauge boson emerge with mass in the TeV range along with a new heavy fermion associated with the standard model top quark. After checking constraints from electroweak precision observables, we investigate the influence of the model on Higgs boson physics, notably on its production cross section and decay branching fractions. Limits on the flavon $\varphi$ from heavy Higgs boson searches at the LHC at 7 and 8 TeV are presented. The branching fractions of the flavon are computed as a function of the flavon mass and the Higgs-flavon mixing angle. We also explore possible discovery of the flavon at 14 TeV, particularly via the $\varphi \rightarrow Z^0Z^0$ decay channel in the $2\ell2\ell'$ final state, and through standard model Higgs boson pair production $\varphi \rightarrow hh$ in the $b\bar{b}\gamma\gamma$ final state. We conclude that the flavon mass range up to $500$ GeV could probed down to quite small values of the Higgs-flavon mixing angle with 100 fb$^{-1}$ of integrated luminosity at 14 TeV.

PolarizedWWscattering on the Higgs pole

The Higgs discovery has given us the Higgs-gauge sector as a new handle to search for physics beyond the Standard Model. This includes physics scenarios originally linked to massive gauge boson scattering at high energies. We investigate how one can separately probe the Higgs couplings to the longitudinal and transverse parts of the massive gauge bosons away from this high-energy limit. Deviations from the Standard Model could originate from higher-dimensional operators, compositeness, or even more fundamentally from a violation of gauge invariance. The signature we propose is the tagging jet kinematics in weak boson scattering for scattering energies close to the Higgs resonance. During the upcoming LHC run at 13 TeV we will be able to test these couplings at the 20% level.

Kinetic mixing and symmetry breaking dependent interactions of the dark photon

We examine spontaneous symmetry breaking of a renormalisable U(1)×U(1) gauge theory coupled to fermions when kinetic mixing is present. We do not assume that the kinetic mixing parameter is small. A rotation plus scaling is used to remove the mixing and put the gauge kinetic terms in the canonical form. Fermion currents are also rotated in a non-orthogonal way by this basis transformation. Through suitable redefinitions the interaction is cast into a diagonal form. This framework, where mixing is absent, is used for subsequent analysis. The symmetry breaking determines the fermionic current which couples to the massless gauge boson. The strength of this coupling as well as the couplings of the massive gauge boson are extracted. This formulation is used to consider a gauged model for dark matter by identifying the massless gauge boson with the photon and the massive state to its dark counterpart. Matching the coupling of the residual symmetry with that of the photon sets a lower bound on the kinetic mixing parameter. We present analytical formulae of the couplings of the dark photon in this model and indicate some physics consequences.

Renormalization group equation for weakly power-counting renormalizable theories

We study the renormalization group flow in weak power counting (WPC) renormalizable theories. The latter are theories which, after being formulated in terms of certain variables, display only a finite number of independent divergent amplitudes order by order in the loop expansion. Using as a toolbox the well-known SU(2) non linear sigma model, we prove that for such theories a renormalization group equation holds that does not violate the WPC condition: that is, the sliding of the scale $\mu$ for physical amplitudes can be reabsorbed by a suitable set of finite counterterms arising at the loop order prescribed by the WPC itself. We explore in some detail the consequences of this result; in particular, we prove that it holds in the framework of a recently introduced beyond the Standard Model scenario in which one considers non-linear St\"uckelberg-like symmetry breaking contributions to the fermion and gauge boson mass generation mechanism.

One-loop radiative correction to Kaluza-Klein masses in S2/Z2 universal extra-dimensional model

We investigate a radiative correction to the masses of Kaluza-Klein(KK) modes in a universal extra dimensional model which are defined on a six-dimensional spacetime with extra space as a two-sphere orbifold $S^2/Z_2$. We first define the Feynman rules which are necessary for the calculation. We then calculate the one-loop diagrams which contribute to the radiative corrections to the KK masses, and obtain one-loop corrections to masses for fermions, gauge bosons and scalar bosons. We estimate the one-loop corrections to KK masses for the first KK modes of standard model particles as a function of momentum cut-off scale, and we determine the lightest KK particle which would be a promising candidate of a dark matter.

NMSSMCALC: A program package for the calculation of loop-corrected Higgs boson masses and decay widths in the (complex) NMSSM

We present the program package NMSSMCALC for the calculation of the loop-corrected NMSSM Higgs boson masses and decay widths in the CP-conserving and CP-violating NMSSM. The full one-loop corrections to the Higgs boson masses are evaluated in a mixed renormalisation scheme of on-shell and DR¯ conditions. The Higgs decay widths include the dominant higher order QCD corrections, and the decays into bottom quarks, strange quarks and τ leptons are supplemented by higher order SUSY corrections through effective couplings. All relevant off-shell decays into two massive gauge bosons, gauge and Higgs boson and Higgs pair final states as well as into heavy quark pairs are computed. The input and output files feature the SUSY Les Houches Accord so that the program can easily be linked with existing computer tools. Program summaryProgram title: NMSSMCALCCatalogue identifier: AEUE_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEUE_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 53070No. of bytes in distributed program, including test data, etc.: 329132Distribution format: tar.gzProgramming language: Fortran77.Computer: Any with a Fortran77 system.Operating system: Linux, Unix.RAM: 0.5MBClassification: 11.1.Nature of problem:Computation of the NMSSM Higgs mass spectrum including higher order corrections in a mixed renormalisation scheme of on-shell and DRbar conditions, and numerical calculation of the decay widths and branching ratios, both in the CP-conserving and in the CP-violating NMSSM. The decay widths include the dominant higher order QCD corrections and, for the neutral Higgs boson decays into a bottom quark pair, the higher order SUSY–QCD and the approximate SUSY–electroweak (elw) corrections up to one-loop accuracy. The decays into a strange quark pair include the dominant resummed SUSY–QCD corrections and the one into a τ pair the dominant resummed SUSY–elw corrections. Analogously for the charged Higgs boson the higher order SUSY corrections have been implemented for the decays into fermion pairs. In the real NMSSM, the decays into stop and sbottom pairs, respectively, contain the SUSY–QCD corrections. All relevant off-shell decays into massive gauge bosons, into gauge and Higgs bosons, into Higgs pairs and into heavy quark pairs have been taken into account. The input and output files feature the SUSY Les Houches Accord (SLHA).Solution method:The necessary input values are set in the two input files inp.dat (in the SLHA format) and bhdecay.in. The file inp.dat, where the choice between the real and the complex NMSSM can be made, is read in by CalcMasses.F, which calculates the one-loop corrected NMSSM Higgs mass spectrum. CalcMasses.F writes out all necessary parameters, masses and mixing angles in an SLHA format file slha.in, which is read in by bhdecay.f (by bhdecay c.f in the complex case). This Fortran routine then computes the decay widths and branching ratios and writes them out in an SLHA format file slha decay.out. Furthermore it writes out all parameters and mixing angles.Restrictions:At present the NMSSM Higgs spectrum is calculated at one-loop accuracy, the Higgs self-couplings at leading order, and no renormalisation group running of the input parameters is included. However, we are about to implement the two-loop corrections to the NMSSM Higgs boson masses and the Higgs self-couplings. Furthermore, the renormalisation group equations for the input parameters shall be provided in the near future. The program does not provide any distributions.Running time:Less than one second per point

Spontaneously broken gauge theories and the coset construction

The methods of non-linear realizations have proven to be powerful in studying the low energy physics resulting from spontaneously broken internal and spacetime symmetries. In this paper, we reconsider how these techniques may be applied to the case of spontaneously broken gauge theories, concentrating on Yang-Mills theories. We find that coset methods faithfully reproduce the description of low energy physics in terms of massive gauge bosons and discover that the St\"uckelberg replacement commonly employed when treating massive gauge theories arises in a natural manner. Uses of the methods are considered in various contexts, including generalizations to $p$-form gauge fields. We briefly discuss potential applications of the techniques to theories of massive gravity and their possible interpretation as a Higgs phase of general relativity.

Neutral Current in Reduced Minimal 3-3-1 Model

This work is devoted for gauge boson sector of the recentlyproposed model based on \(\mathrm{SU}(3)_C\otimes \mathrm{SU}(3)_L\otimes \mathrm{U}(1)_X\) group with minimal content of leptons andHiggses. The limits on the masses of the bilepton gauge bosons andon the mixing angle among the neutral ones are deduced. Using theFritzsch anzats on quark mixing, we show that the third family ofquarks should be different from the first two. We obtain a lowerbound on mass of the new heavy neutral gauge boson as 4.032 TeV.Using data on branching decay rates of the \(Z\) boson, we can fix the limit to the \(Z\) and $Z^\prime$ mixing angle\(\phi\) as \(-0.001\le\phi\le 0.0003\).

Constraining the $$Z^{\prime }$$ Z ′ mass in 331 models using direct dark matter detection

We investigate a so-called 331 extension of the Standard Model gauge sector which accommodates neutrino masses and where the lightest of the new neutral fermions in the theory is a viable particle dark matter candidate. In this model, processes mediated by the additional $Z^{\prime}$ gauge boson set both the dark matter relic abundance and the scattering cross section off of nuclei. We calculate with unprecedented accuracy the dark matter relic density, including the important effect of coannihilation across the heavy fermion sector, and show that indeed the candidate particle has the potential of having the observed dark matter density. We find that the recent LUX results put very stringent bounds on the mass of the extra gauge boson, $M_{Z^{\prime}} \gtrsim 2$~TeV, independently of the dark matter mass. We also comment on regime where our bounds on the $Z^{\prime}$ mass may apply to generic 331-like models, and on implications for LHC phenomenology.

A compact 341 model at TeV scale

We build a gauge model based on the SU(3)c⊗SU(4)L⊗U(1)X symmetry where the scalar spectrum needed to generate gauge boson and fermion masses has a smaller scalar content than usually assumed in literature. We compute the running of its abelian gauge coupling and show that a Landau pole shows up at the TeV scale, a fact that we use to consistently implement those fermion masses that are not generated by Yukawa interactions, including neutrino masses. This is appropriately achieved by non renormalizable effective operators, suppressed by the Landau pole scale. Also, SU(3)c⊗SU(3)L⊗U(1)N models embedded in this gauge structure are bound to be strongly coupled at this same energy scale, contrary to what is generally believed, and neutrino mass generation is rather explained through the same effective operators used in the larger gauge group. Besides, their nice features, as the existence of cold dark matter candidates and the ability to reproduce the observed standard model Higgs-like phenomenology, are automatically inherited by our model. Finally, our results imply that this model is constrained to be observed or discarded soon, since it must be realized at the currently probed energy scale in LHC.

Search at the Mainz Microtron for light massive gauge bosons relevant for the muon g-2 anomaly.

A massive, but light, Abelian U(1) gauge boson is a well-motivated possible signature of physics beyond the standard model of particle physics. In this Letter, the search for the signal of such a U(1) gauge boson in electron-positron pair production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron is described. Exclusion limits in the mass range of 40 MeV/c^{2} to 300 MeV/c^{2}, with a sensitivity in the squared mixing parameter of as little as ε^{2}=8×10^{-7} are presented. A large fraction of the parameter space has been excluded where the discrepancy of the measured anomalous magnetic moment of the muon with theory might be explained by an additional U(1) gauge boson.

Neutrino mass and mixing in the 3-3-1 model and S 3 flavor symmetry with minimal Higgs content

A new S3 flavor model based on the SU(3)C ⊗ SU(3)L ⊗ U(1)X gauge symmetry responsible for fermion masses and mixings different from our previous work [14, 17] is constructed. The new feature is a two-dimensional representation of a Higgs anti-sextet under S3, which is responsible for neutrino masses and mixings. The neutrinos acquire small masses from only an anti-sextet of SU(3), which is in a doublet under S3. If the difference of components of the anti-sextet is regarded as a small perturbation, S3 is equivalently broken into identity, the corresponding neutrino mass mixing matrix acquires the most general form, and the model can fit the latest data on neutrino oscillations. This way of symmetry breaking helps us reduce a content in the Higgs sector, to only one anti-sextet instead of two as in our previous work [14]. Our results show that the neutrino masses are naturally small and a small deviation from the tri-bimaximal neutrino mixing form can be realized. The Higgs potential of the model as well as the minimization conditions and gauge boson masses and mixings are also considered.

Higgs mass and the Stueckelberg mechanism in supersymmetry

We investigate a class of theories where the mass of the lightest Higgs boson of the Minimal Supersymmetric Standard Model (MSSM) can be larger than the Z gauge boson mass at tree level. In this context the MSSM fields feel a new force, whose corresponding gauge boson attains its mass through the Stueckelberg mechanism. We show how one can achieve a Higgs mass around 126 GeV without assuming a heavy stop spectrum or a large stop trilinear term. The application of this class of models to the conservation of R-parity is also discussed.

Light third-generation squarks from flavour gauge messengers

We study models of gauge-mediated supersymmetry breaking with a gauged horizontal SU(3)_F symmetry acting on the quark superfields. If SU(3)_F is broken non-supersymmetrically by F-term vacuum expectation values, the massive gauge bosons and gauginos become messengers for SUSY breaking mediation. These gauge messenger fields induce a flavour-dependent, negative contribution to the soft masses of the squarks at one loop. In combination with the soft terms from standard gauge mediation, one obtains large and degenerate first- and second-generation squark masses, while the stops and sbottoms are light. We discuss the implications of this mechanism for the superparticle spectrum and for flavour precision observables. We also provide an explicit realization in a model with simultaneous SUSY and SU(3)_F breaking.

The road of gaining mass for gauge boson: interpretation of Nobel Prize in physics 2013

The road of gaining mass for gauge boson: interpretation of Nobel Prize in physics 2013

Radion/dilaton-Higgs mixing phenomenology in light of the LHC

Motivated by the bulk mixing $\xi R_5 H^{\dagger}H$ between a massive radion and a bulk scalar Higgs in warped extra dimensions, we construct an effective four dimensional action that---via the AdS/CFT correspondence---describes the most general mixing between the only light states in the theory, the dilaton and the Higgs. Due to conformal invariance, once the Higgs scalar is localized in the bulk of the extra-dimension the coupling between the dilaton and the Higgs kinetic term vanishes, implying a suppressed coupling between the dilaton and massive gauge bosons. We comment on the implications of the mixing and couplings to Standard Model particles. Identifying the recently discovered 125 GeV resonance with the lightest Higgs-like mixed state $\phi_{-}$, we study the phenomenology and constraints for the heaviest radion-like state $\phi_{+}$. In particular we find that in the small mixing scenario with a radion-like state $\phi_{+}$ in the mass range [150,250] GeV, the diphoton channel can provide the best chance of discovery at the LHC if the collaborations extend their searches into this energy range.