Search

We consider a neutrinophilic $U(1)$ extension of the standard model (SM) which couples only to SM isosinglet neutral fermions, charged under the new group. The neutral fermions couple to the SM matter fields through Yukawa interactions. The neutrinos in the model get their masses from a standard inverse-seesaw mechanism while an added scalar sector is responsible for the breaking of the gauged $U(1)$ leading to a light neutral gauge boson ($Z'$) which has minimal interaction with the SM sector. We study the phenomenology of having such a light $Z'$ in the context of neutrinophilic interactions as well as the role of allowing kinetic mixing between the new $U(1)$ group with the SM hypercharge group. We show that current experimental searches allow for a very light $Z'$ if it does not couple to SM fields directly and highlight the search strategies at the LHC. We observe that multi-lepton final states in the form of $(4\ell + \mET)$ and $(3\ell + 2j + \mET)$ could be crucial in discovering such a neutrinophilic gauge boson lying in a mass range of $200$--$500$ GeV.

In a topological description of elementary matter proposed by Bilson-Thompson, the leptons and quarks of a single generation, together with the electroweak gauge bosons, are represented as elements of the framed braid group of three ribbons. By identifying these braids with emergent topological excitations of ribbon networks, it has been possible to encode this braid model into the framework of quantum geometry provided by loop quantum gravity. One major hurdle in this promising approach to unifying matter and space-time has been the difficulty in implementing any dynamics that reflects observed particle interactions. In the case of trivalent networks, it has not been possible to generate particle interactions, because the braids correspond to noiseless subsystems, meaning they commute with the evolution algebra generated by the local Pachner moves. In the case of tetravalent networks, interactions are only possible when the model's original simplicity, in which interactions take place via the composition of braids, is sacrificed. The main result of the present paper is to demonstrate that it is possible to preserve both the original classification of fermions, as well as their interaction via the braid product, if we embed the braid in a trivalent scheme and supplement the local Pachner moves, with a nonlocal and graph-changing one-handle attachment. Moreover, we use Kauffman-Lins recoupling theory to obtain invariants of braided networks that distinguish topological configurations associated to particles in the Bilson-Thompson model.

Hamiltonian formulation of lattice gauge theories (LGTs) is the most natural framework for the purpose of quantum simulation, an area of research that is growing with advances in quantum-computing algorithms and hardware. It, therefore, remains an important task to identify the most accurate, while computationally economic, Hamiltonian formulation(s) in such theories, considering the necessary truncation imposed on the Hilbert space of gauge bosons with any finite computing resources. This paper is a first step toward addressing this question in the case of non-Abelian LGTs, which further require the imposition of non-Abelian Gauss's laws on the Hilbert space, introducing additional computational complexity. Focusing on the case of SU(2) LGT in 1+1 D coupled to matter, a number of different formulations of the original Kogut-Susskind framework are analyzed with regard to the dependence of the dimension of the physical Hilbert space on boundary conditions, system's size, and the cutoff on the excitations of gauge bosons. The impact of such dependencies on the accuracy of the spectrum and dynamics is examined, and the (classical) computational-resource requirements given these considerations are studied. Besides the well-known angular-momentum formulation of the theory, the cases of purely fermionic and purely bosonic formulations (with open boundary conditions), and the Loop-String-Hadron formulation are analyzed, along with a brief discussion of a Quantum Link Model of the same theory. Clear advantages are found in working with the Loop-String-Hadron framework which implements non-Abelian Gauss's laws a priori using a complete set of gauge-invariant operators. Although small lattices are studied in the numerical analysis of this work, and only the simplest algorithms are considered, a range of conclusions will be applicable to larger systems and potentially to higher dimensions., Comment: 41 pages, 30 figures, 5 tables, one Mathematica Notebook as Supplemental Material

Motivated by the growing evidence for the possible lepton flavor universality violation after the first results from Fermilab's muon $g\ensuremath{-}2$ measurement, we revisit one of the most widely studied anomaly free extensions of the standard model namely, gauged ${L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}$ model, to find a common explanation for muon $g\ensuremath{-}2$ as well as baryon asymmetry of the universe via leptogenesis. The minimal setup allows TeV scale resonant leptogenesis satisfying light neutrino data while the existence of light ${L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}$ gauge boson affects the scale of leptogenesis as the right handed neutrinos are charged under it. For ${L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}$ gauge boson mass at GeV scale or above, the muon $g\ensuremath{-}2$ favored parameter space is already ruled out by other experimental data while bringing down its mass to sub-GeV regime leads to vanishing lepton asymmetry due to highly restrictive structures of lepton mass matrices at the scale of leptogenesis. Extending the minimal model with two additional Higgs doublets can lead to a scenario consistent with successful resonant leptogenesis and muon $g\ensuremath{-}2$ while satisfying all relevant experimental data.

Semileptonic flavor-changing neutral-current transitions with a pair of neutrinos in the final state are very accurately determined in the Standard Model (SM) and thus provide an accurate and sensitive probe for physics beyond the SM. Until recently, the poor tagging efficiency for the $B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ modes made them less advantageous as a probe of new physics (NP) compared to the charged lepton counterparts. The most recent Belle II result on $B\ensuremath{\rightarrow}K\ensuremath{\nu}\overline{\ensuremath{\nu}}$ uses an innovative inclusive tagging technique, resulting in a higher tagging efficiency; this together with previous BABAR and Belle results indicates a possible enhancement in the branching fraction of ${B}^{+}\ensuremath{\rightarrow}{K}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$. A reanalysis of the full Belle dataset together with the upcoming Belle II dataset is expected to result in a much more precise measurement of this mode. If the branching ratio is indeed found to be enhanced with improved measurements, this would provide an unambiguous signal of NP without uncertainties due to long-distance nonfactorizable effects or power corrections (in contrast to $B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\ell}\ensuremath{\ell}$). We have explored the possibilities of such an enhancement as a signal of NP within several scenarios, which can also explain some of the other tensions observed in neutral- as well as charged-current $B$ decays. In an effective field theory approach, with the most general dimension-6 Hamiltonian including light right-handed neutrinos, we explore the viability of all scalar and vector leptoquarks, as well as the parameter space possible with a generic vector gauge boson ${Z}^{\ensuremath{'}}$ model, assuming minimal new particle content. While being consistent with all data, correlations between the observed intriguing discrepancies in $B$ decays are also obtained, which will discriminate between the various NP scenarios.

The Gamma Factory is a proposal to back-scatter laser photons off a beam of partially-stripped ions at the LHC, producing a beam of $\sim 10$ MeV to $1$ GeV photons with intensities of $10^{16}$ to $10^{18}~\text{s}^{-1}$. This implies $\sim 10^{23}$ to $10^{25}$ photons on target per year, many orders of magnitude greater than existing accelerator light sources and also far greater than all current and planned electron and proton fixed target experiments. We determine the Gamma Factory's discovery potential through "dark Compton scattering," $\gamma e \to e X$, where $X$ is a new, weakly-interacting particle. For dark photons and other new gauge bosons with masses in the 1~to~100 MeV range, the Gamma Factory has the potential to discover extremely weakly-interacting particles with just a few hours of data and will probe couplings as low as $\sim 10^{-9}$ with a year of running. The Gamma Factory therefore may probe couplings lower than all other terrestrial experiments and is highly complementary to astrophysical probes. We outline the requirements of an experiment to realize this potential and determine the sensitivity reach for various experimental configurations., Comment: 20 pages, 9 captioned figures. Version accepted in PRD

In the framework of singlet vectorlike lepton (VLL) model, we study a search for VLL in the semileptonic channel at high energy ${e}^{+}{e}^{\ensuremath{-}}$ colliders. According to the different decay modes of the electroweak gauge bosons, we divide the signal into two modes, that is mode A and mode B. We performed a detailed detector simulation and displayed the excluding and discovering capability of VLL at different colliders. Compared to the mode B, we find that it is more promising to exclude and discover the VLL in mode A.

We identify potential sources of decoherence for $U(1)$ gauge bosons from a cosmological standpoint. Besides interactions with different species in the cosmological medium, we also consider effects due to the expansion of the Universe, which can produce particles (especially scalars) than can potentially interact with the photon in a quantum state. We look in particular at the case of axion-like particles and their predicted decay channels in our analysis. These interactions are shown to have a negligible effect as far as decoherence goes. Interaction rates with CMB radiation or through Thomson scattering are small, so that the interstellar medium remains the biggest decoherence factor. Thus, quantum teleportation experiments with photon energies in the range $1$-$10$ keV should be feasible at cosmological distances up to the galaxy formation epoch or beyond ($z \sim 100$)., Comment: 11 pages

We study electroweak symmetry breaking in minimal composite Higgs models $SU(4)/Sp(4)$ with purely fermionic UV completions based on a confining Hypercolor gauge group and find that the extra Higgs potential from the underlying preon mass can destruct the correlation between the mass of Higgs and composite partners. Thus the composite partners can be very heavy for successful electroweak symmetry breaking without enhancing the separation between the new physical scale and Higgs VEV. So this kind of model can be easily realized by ordinary strong dynamics theories without artificial assumptions and more likely consistent with lattice simulations. The UV completion of partial compositeness predicts a light singlet Goldstone boson which interacts with QCD and electroweak gauge bosons through Wess-Zumino-Witten terms. It can be produced through gluon fusion at LHC and decay into gauge boson pairs. We briefly discuss its phenomenology and derive its bounds from LHC searches., 11 pages, four figures

In the framework of classical scale invariance, we consider quadratic gravity in the Palatini formalism and investigate the inflationary predictions of the theory. Our model corresponds to a two-field scalar-tensor theory, that involves the Higgs field and an extra scalar field stemming from a gauge $U(1)_X$ extension of the Standard Model, which contains an extra gauge boson and three right-handed neutrinos. Both scalar fields couple nonminimally to gravity and induce the Planck scale dynamically, once they develop vacuum expectation values. By means of the Gildener-Weinberg approach, we describe the inflationary dynamics in terms of a single scalar degree of freedom along the flat direction of the tree-level potential. The one-loop effective potential in the Einstein frame exhibits plateaus on both sides of the minimum and thus the model can accommodate both small and large field inflation. The inflationary predictions of the model are found to comply with the latest bounds set by the Planck collaboration for a wide range of parameters and the effect of the quadratic in curvature terms is to reduce the value of the tensor-to-scalar ratio., Comment: matches version to be published in PRD

We propose a self-interacting inelastic dark matter (DM) scenario as a possible origin of the recently reported excess of electron recoil events by the XENON1T experiment. Two quasi-degenerate Majorana fermion DM interact within themselves via a light hidden sector massive gauge boson and with the standard model particles via gauge kinetic mixing. We also consider an additional long-lived singlet scalar which helps in realising correct dark matter relic abundance via a hybrid setup comprising of both freeze-in and freeze-out mechanisms. While being consistent with the required DM phenomenology along with sufficient self-interactions to address the small scale issues of cold dark matter, the model with GeV scale DM can explain the XENON1T excess via inelastic down scattering of heavier DM component into the lighter one. All these requirements leave a very tiny parameter space keeping the model very predictive for near future experiments., Comment: 34 pages, 14 figures, version accepted for publication in PRD

We investigate a model of dark sector based on non-Abelian $SU(2{)}_{D}$ gauge symmetry. This dark gauge symmetry is broken into discrete ${Z}_{2}$ via vacuum expectation values of two real triplet scalars, and an $SU(2{)}_{D}$ doublet Dirac fermion becomes ${Z}_{2}$---odd particles whose lighter component makes stable dark matter candidate. The standard model and dark sector can be connected via the scalar mixing and the gauge kinetic mixing generated by higher dimensional operators. We then discuss relic density of dark matter and implications to collider physics in the model. The most unique signatures of this model at the LHC would be the dark scalar (${\mathrm{\ensuremath{\Phi}}}_{1}^{{(}^{\ensuremath{'}})}$) productions where it subsequently decays into: (1) a fermionic dark matter (${\ensuremath{\chi}}_{l}$) and a heavy dark fermion (${\ensuremath{\chi}}_{h}$) pair, ${\mathrm{\ensuremath{\Phi}}}_{1}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{\overline{\ensuremath{\chi}}}_{l}{\ensuremath{\chi}}_{h}({\overline{\ensuremath{\chi}}}_{h}{\ensuremath{\chi}}_{l})$, followed by ${\ensuremath{\chi}}_{h}$ decays into ${\ensuremath{\chi}}_{l}$ and non-Abelian dark gauge bosons (${X}_{i}$'s) which decays into SM fermion pair ${\overline{f}}_{\mathrm{SM}}{f}_{\mathrm{SM}}$ resulting in the reaction $pp\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Phi}}}_{1}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{\overline{\ensuremath{\chi}}}_{h}{\ensuremath{\chi}}_{l}({\overline{\ensuremath{\chi}}}_{l}{\ensuremath{\chi}}_{h})\ensuremath{\rightarrow}{f}_{\mathrm{SM}}{\overline{f}}_{\mathrm{SM}}{\ensuremath{\chi}}_{l}{\overline{\ensuremath{\chi}}}_{l}$, (2) a pair of ${X}_{i}$'s followed by ${X}_{i}$ decays into a DM pair or the SM fermions resulting in the reaction, $pp\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Phi}}}_{1}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{X}_{i}{X}_{i}\ensuremath{\rightarrow}{\overline{\ensuremath{\chi}}}_{l}{\ensuremath{\chi}}_{l}{f}_{\mathrm{SM}}{\overline{f}}_{\mathrm{SM}}$ or even number of ${f}_{\mathrm{SM}}{\overline{f}}_{\mathrm{SM}}$ pairs.

We investigate the cosmological stability of light bosonic dark matter carrying a tiny electric charge. In the wave-like regime of high occupation numbers, annihilation into gauge bosons can be drastically enhanced by parametric resonance. The millicharged particle can either be minimally coupled to photons or its electromagnetic interaction can be mediated via kinetic mixing with a massless hidden photon. In the case of a direct coupling current observational constraints on the millicharge are stronger than those arising from parametric resonance. For the (theoretically preferred) case of kinetic mixing large regions of parameter space are affected by the parametric resonance leading at least to a fragmentation of the dark matter field if not its outright destruction., 14 pages, 3 figures. v2: minor corrections

The physics reach of a low threshold (100 eV) scintillating argon bubble chamber sensitive to Coherent Elastic neutrino-Nucleus Scattering (CE$\nu$NS) from reactor neutrinos is studied. The sensitivity to the weak mixing angle, neutrino magnetic moment, and a light $Z'$ gauge boson mediator are analyzed. A Monte Carlo simulation of the backgrounds is performed to assess their contribution to the signal. The analysis shows that world-leading sensitivities are achieved with a one-year exposure for a 10 kg chamber at 3 m from a 1 MW$_{th}$ research reactor or a 100 kg chamber at 30 m from a 2000 MW$_{th}$ power reactor. Such a detector has the potential to become the leading technology to study CE$\nu$NS using nuclear reactors., Comment: 9 pages, 5 figures. v2: figures added, minor changes. Matches published version

Extensions of the Standard Model with an Abelian gauge group are constrained by gauge anomaly cancellation, so that only a limited number of possible charge assignments is allowed without the introduction of new chiral fermions. For flavor universal charges, couplings of the associated hidden photon to Standard Model fermions are flavor conserving at tree level. We show explicitly that even the flavor-specific charge assignments allowed by anomaly cancellation condition lead to flavor-conserving tree-level couplings of the hidden photon to quarks and charged leptons if the Cabibbo-Kobayashi-Maskawa or Pontecorvo-Maki-Nakagawa-Sakata matrix can be successfully reconstructed. Further, loop-induced flavor-changing couplings are strongly suppressed. As a consequence, the structure of the Majorana mass matrix is constrained and flavor-changing tree-level couplings of the hidden photon to neutrino mass eigenstates are identified as a means to distinguish the U(1)B−L gauge boson from any other anomaly-free extension of the Standard Model without new chiral fermions. We present a comprehensive analysis of constraints and projections for future searches for a U(1)B−3Li gauge boson, calculate the reach of resonance searches in B meson decays and comment on the implications for nonstandard neutrino interactions.

Lepton flavor universality can be tested through the ratio of semileptonic $B$ meson decays and leptonic $\mathrm{\ensuremath{\Upsilon}}$ meson decays, with $\mathrm{\ensuremath{\Upsilon}}\ensuremath{\equiv}\mathrm{\ensuremath{\Upsilon}}(nS)$ ($n=1$, 2, 3). For the charged-current transitions $b\ensuremath{\rightarrow}c\ensuremath{\tau}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$, discrepancies between the experiment and the Standard Model (SM) have been observed in recent years by different flavor facilities such as BABAR, Belle, and LHCb. While for the neutral-current transitions $b\overline{b}\ensuremath{\rightarrow}\ensuremath{\tau}\overline{\ensuremath{\tau}}$, the BABAR experiment reported recently a new measurement of leptonic decay ratio ${R}_{\mathrm{\ensuremath{\Upsilon}}(3S)}=\mathrm{BR}(\mathrm{\ensuremath{\Upsilon}}(3S)\ensuremath{\rightarrow}\phantom{\rule{0ex}{0ex}}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}})/\mathrm{BR}(\mathrm{\ensuremath{\Upsilon}}(3S)\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$, showing an agreement with the SM at the $1.8\ensuremath{\sigma}$ level. In light of this new BABAR result and regarding the connection between new physics (NP) interpretations to the charged-current $b\ensuremath{\rightarrow}c\ensuremath{\tau}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ anomalies and neutral-current $b\overline{b}\ensuremath{\rightarrow}\ensuremath{\tau}\overline{\ensuremath{\tau}}$ processes, in this study, we revisit the NP consequences of this measurement within a simplified model with extra massive gauge bosons that coupled predominantly to left-handed leptons of the third generation. We show that the BABAR measurement of ${R}_{\mathrm{\ensuremath{\Upsilon}}(3S)}$ cannot easily be accommodated (within its experimental $1\ensuremath{\sigma}$ range) together with the other $b\ensuremath{\rightarrow}c\ensuremath{\tau}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ data, hinting toward a new anomalous observable.

The full ATLAS run 2 dataset with a time-integrated luminosity of $139\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ in the diboson and dilepton channels is used to probe benchmark models with extended gauge sectors: the ${E}_{6}$-motivated grand unification models, the left-right symmetric model, and the sequential standard model [extended gauge model (EGM)]. These all predict neutral ${Z}^{\ensuremath{'}}$ vector bosons, decaying into lepton pairs $\ensuremath{\ell}\ensuremath{\ell}$ or into electroweak gauge boson pairs $WW$, where one $W$ in turn decays semileptonically. The 95% C.L. exclusion limits on the ${Z}^{\ensuremath{'}}$ resonance production cross section times the branching ratio to electroweak gauge boson pairs and to lepton pairs in the mass range of $\ensuremath{\sim}1$ to 6 TeV are converted to constraints on the $Z\text{\ensuremath{-}}{Z}^{\ensuremath{'}}$ mixing parameter and the heavy resonance mass. We present exclusion regions on the parameter space of the ${Z}^{\ensuremath{'}}$ which are significantly extended compared to those obtained from the previous analyses performed with LHC data collected at 7 and 8 TeV in run 1 as well as at 13 TeV in run 2 at a time-integrated luminosity of $36.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ and are the most stringent bounds to date. Also presented, from a similar analysis of electrically charged ${W}^{\ensuremath{'}}$ bosons arising in the EGM, which can decay through ${W}^{\ensuremath{'}}\ensuremath{\rightarrow}WZ$ and ${W}^{\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\ell}\ensuremath{\nu}$, are limits on the $W\text{\ensuremath{-}}{W}^{\ensuremath{'}}$ mixing parameter and the charged ${W}^{\ensuremath{'}}$ vector boson mass.

A theory of gravity is deduced from the axioms of the premetric program. The starting point is the conservation of energy and momenta, and the equivalence of gravitation and inertia. The latter is what leads to the framework of the so-called purified gravity. The local and linear constitutive relation has 14 components when it is assumed to be metrical, but the compatibility of the constitutive relation with an action principle fixes uniquely the theory of coincident general relativity. The premetric formalism of purified gravity has a direct analogy with massive electromagnetism, the Planck mass corresponding to the Proca mass of the gauge boson. The metric emerges as a Stueckelberg field, and the graviton as a Goldstone boson of the broken symmetry.

Composite Higgs models can be extended to the Planck scale by means of the partially unified partial compositeness (PUPC) framework. We present in detail the Techni-Pati-Salam model, based on a renormalizable gauge theory SU(8)PS×SU(2)L×SU(2)R. We demonstrate that masses and mixings for all generations of standard model fermions can be obtained via partial compositeness at low energy, with four-fermion operators mediated by either heavy gauge bosons or scalars. The strong dynamics is predicted to be that of a confining Sp(4)HC gauge group, with hyperfermions in the fundamental and two-index antisymmetric representations, with fixed multiplicities. This is motivation for lattice studies of the infrared near-conformal walking phase, with results that may validate or rule out the model. This is the first complete and realistic attempt at providing an ultraviolet completion for composite Higgs models with top partial compositeness. In the baryon-number conserving vacuum, the theory also predicts a dark matter candidate, with a mass in the few TeV range, protected by semi-integer baryon number.

In models of baryogenesis based on Grand Unified Theories (GUTs), the baryon asymmetry of the universe is generated through the CP and baryon number violating, out-of-equilibrium decays of very massive gauge or Higgs bosons in the very early universe. Recent constraints on the scale of inflation and the subsequent temperature of reheating, however, have put pressure on many such models. In this paper, we consider the role that primordial black holes may have played in the process of GUT baryogenesis. Through Hawking evaporation, black holes can efficiently generate GUT Higgs or gauge bosons, regardless of the masses of these particles or the temperature of the early universe. Furthermore, in significant regions of parameter space, the black holes evaporate after the electroweak phase transition, naturally evading the problem of sphaleron washout that is normally encountered in GUT models based on $SU(5)$. We identify a wide range of scenarios in which black holes could facilitate the generation of the baryon asymmetry through the production and decays of GUT bosons., 12 pages, 4 figures, 1 appendix

The most statistically significant hints for new physics in the flavor sector are discrepancies between theory and experiment in $B$ decays to lepton pairs ($b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$) and a deficit in the unitarity constraints to the 1st row of the Cabibbo-Kobayashi-Maskawa matrix (the Cabibbo angle anomaly). We propose that these anomalies can be reconciled by a simplified model with massive gauge bosons transforming in the adjoint representation of $SU(2{)}_{L}$. After calculating the impact of this model on $B$ decays, observables testing charged current lepton flavor universality (LFU), electro-weak precision observables and LHC searches we perform a global fit to all available data. We find that our model can provide a consistent common explanation of both anomalies and that the fit to the data is more than $7\ensuremath{\sigma}$ better than the fit of the Standard Model. The model also predicts interesting correlations between LFU violation in the charged current and $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ data which can be tested experimentally in the near future.

We show that the nonperturbative decay of ultralight scalars into Abelian gauge bosons, recently proposed as a possible solution to the Hubble tension, produces a stochastic background of gravitational waves which is constrained by the cosmic microwave background. We simulate the full nonlinear dynamics of resonant dark photon production and the associated gravitational wave production, finding the signals to exceed constraints for the entire parameter space we consider. Our findings suggest that gravitational wave production from the decay of early dark energy may provide a unique probe of these models., Comment: 5 pages + appendices, 5 figures; matches published version

We investigate the minimal $U(1{)}_{{L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}}$ model with extra heavy vectorlike leptons or charged scalars. By studying the kinetic mixing between $U(1{)}_{{L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}}$ gauge boson ${Z}^{\ensuremath{'}}$ and standard model photon, which is absent at tree level and will arise at one-loop level due to $\ensuremath{\mu}$, $\ensuremath{\tau}$, and new heavy charged leptons or scalars, the interesting behavior is shown. It can provide the possibility for visible signatures of new heavy particles. We propose to search for ${Z}^{\ensuremath{'}}$ at electron collider experiments, such as Belle II, BESIII, and future Super Tau Charm Factory (STCF), using the monophoton final state. The parameter space of ${Z}^{\ensuremath{'}}$ is probed and scanned by its gauge coupling constant ${g}_{{Z}^{\ensuremath{'}}}$ and mass ${m}_{{Z}^{\ensuremath{'}}}$. We find that electron colliders have sensitivity to the previously unexplored parameter space for ${Z}^{\ensuremath{'}}$ with MeV--GeV mass. Future STCF experiments with $\sqrt{s}=2--7\text{ }\text{ }\mathrm{GeV}$ can exclude the anomalous muon magnetic moment favored area when ${m}_{{Z}^{\ensuremath{'}}}l5\text{ }\text{ }\mathrm{GeV}$ with the luminosity of $30\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$. For ${m}_{{Z}^{\ensuremath{'}}}l2{m}_{\ensuremath{\mu}}$, ${g}_{{Z}^{\ensuremath{'}}}$ can be down to $4.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at 2 GeV STCF.

We compute mixed QCD-electroweak corrections to the fully-differential production of an on-shell $W$ boson. Decays of $W$ bosons to lepton pairs are included in the leading order approximation. The required two-loop virtual corrections are computed analytically for arbitrary values of the electroweak gauge boson masses. Analytic results for integrated subtraction terms are obtained within a soft-collinear subtraction scheme optimized to accommodate the structural simplicity of infra-red singularities of mixed QCD-electroweak contributions. Numerical results for mixed corrections to the fiducial cross section of $pp \to W^+ \to l^+ \nu$ and selected kinematic distributions in this process are presented., Comment: 40 pages; 5 appendices

In this work, we study the Higgs boson decays into two photons and into one photon and one $Z$ gauge boson within the context of the nonlinear effective field theory called the electroweak chiral Lagrangian (EChL). We present a detailed computation of the corresponding amplitudes to one-loop level in the covariant ${R}_{\ensuremath{\xi}}$ gauges. We assume that the fermionic loop contributions are as in the Standard Model and focus here just in the computation of the bosonic loop contributions. Our renormalization program and the anatomy of the various contributions participating in the ${R}_{\ensuremath{\xi}}$ gauges are fully explored. With this present computation, we demonstrate the gauge invariance of the EChL result, not only for the case of on-shell Higgs boson, but also for the most general and interesting case of off-shell Higgs boson. We finally analyze and conclude on the special relevance of the Goldstone boson loops, in good agreement with the expected chiral loops behavior in chiral Lagrangians. We perform a systematic comparison with the corresponding computation of the Standard Model in the ${R}_{\ensuremath{\xi}}$ gauges and with the previous EChL results in the unitary gauge. This work represents the first computation within the EChL of these observables to one loop, for both on- and off-shell Higgs boson, in the most general ${R}_{\ensuremath{\xi}}$ gauges and with a full renormalization program description, not yet fully explored in the previous literature and which is different to the most frequently used in the linear effective field theory.

We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e-→γa, a→γγ in the mass range 0.2

We address the issue of radiative corrections to Kaluza-Klein (KK) masses in five-dimensional QED supplemented by aether Lorentz-violating terms. Specifically, we compute the corrections to the KK photon masses from one fermion loop. In general, the KK masses receive radiative corrections due to breaking the five-dimensional Lorentz invariance by compactification. As we show, the presence of the additional Lorentz violating factor - an aether background, leads to the non-trivial modification of these corrections. This model may be of interest in addressing important phenomenological issues such as the relation between radiative corrected KK mass splitting of a particular mode and uncertainties in the measurements and/or possible spatial variation of the fine-structure constant. For the recent data on the fine-structure constant, we find a KK mass splitting of magnitude $\sim 0.01$ MeV for the first excited Kaluza-Klein gauge boson at TeV scale. On the other hand, the large KK modes limit displays a very interesting phenomenon, showing the very special role of the aether in protecting the higher modes from the quantum corrections., 13 pages, 3 diagrams

We report on an analysis of the decay J/ψ→γπ0η′ using a sample of (1310.6±7.0)×106J/ψ events collected with the BESIII detector. We search for the CP-violating process ηc→π0η′ and a dark gauge boso ...

We investigate constraints on the new $B-L$ gauge boson ($Z_{BL}$) mass and coupling ($g_{BL}$) in a $U(1)_{B-L}$ extension of the standard model (SM) with an SM singlet Dirac fermion ($\zeta$) as dark matter (DM). The DM particle $\zeta$ has an arbitrary $B-L$ charge $Q$ chosen to guarantee its stability. We focus on the small $Z_{BL}$ mass and small $g_{BL}$ regions of the model, and find new constraints for the cases where the DM relic abundance arises from thermal freeze-out as well as freeze-in mechanisms. In the thermal freeze-out case, the DM coupling is given by $g_{\zeta}\equiv g_{BL}Q\simeq0.016\sqrt{m_\zeta[{\rm GeV}]}$ to reproduce the observed DM relic density and $g_{BL}\geq 2.7 \times 10^{-8} \sqrt{m_\zeta[{\rm GeV}]}$ for the DM particle to be in thermal equilibrium prior to freeze-out. Combined with the direct and indirect DM detection constraints, we find that the allowed mass regions are limited to be $m_\zeta \gtrsim 200$ GeV and $M_{Z_{BL}} \gtrsim 10$ GeV. We then discuss the lower $g_{BL}$ values where the freeze-in scenario operates and find the following relic density constraints on parameters depending on the $g_{BL}$ range and dark matter mass: Case (A): for $g_{BL}\geq 2.7\times10^{-8}\sqrt{m_\zeta[{\rm GeV}]}$, one has $g^2_\zeta\,g^2_{BL}+\frac{0.82}{1.2}\,g^4_\zeta\simeq 8.2\times10^{-24}$ and Case (B): for $g_{BL} < 2.7 \times 10^{-8} \sqrt{m_\zeta[{\rm GeV}]}$, there are two separate constraints depending on $m_\zeta$. Case (B1): for $m_\zeta\lesssim 2.5{\rm TeV}$, we find $g_\zeta^2\,g_{BL}^2\simeq 8.2\times10^{-24}\,\left( \frac{m_\zeta}{2.5\,{\rm TeV}} \right)$ and case (B2): for $m_\zeta \gtrsim 2.5$ TeV, we have $g_\zeta^2 \, g_{BL}^2 \simeq 8.2 \times 10^{-24}$. For this case, we display the various parameter regions of the model that can be probed by a variety of ``Lifetime Frontier" experiments such as FASER, FASER2, Belle II, SHiP and LDMX., Comment: 27 pages, 8 figures, the version to be published in Phys. Rev. D

We propose the $SU(3{)}_{C}\ifmmode\times\else\texttimes\fi{}SU(3{)}_{L}\ifmmode\times\else\texttimes\fi{}U(1{)}_{X}$ model arising from $SU(6)$ breaking. One family of the Standard Model (SM) fermions arises from two $\overline{6}$ representations and one 15 representation of $SU(6)$ gauge symmetry. To break the $SU(3{)}_{C}\ifmmode\times\else\texttimes\fi{}SU(3{)}_{L}\ifmmode\times\else\texttimes\fi{}U(1{)}_{X}$ gauge symmetry down to the SM, we introduce three $SU(3{)}_{L}$ triplet Higgs fields, where two of them come from the $\overline{6}$ representation while the other one from the 15 representation. We study the gauge boson masses and Higgs boson mass in detail, and find that the vacuum expectation value (VEV) of the Higgs field for $SU(3{)}_{L}\ifmmode\times\else\texttimes\fi{}U(1{)}_{X}$ gauge symmetry breaking is around 10 TeV. The neutrino masses and mixing can be generated via the littlest inverse seesaw mechanism. In particular, we have normal hierarchy for neutrino masses and the lightest active neutrino is massless. Also, we consider constraints from the charged lepton flavor changing decays as well. Furthermore, introducing two $SU(3{)}_{L}$ adjoint fermions, one $SU(3{)}_{C}$ adjoint scalar, and one $SU(3{)}_{L}$ triplet scalar, we can achieve gauge coupling unification within 1%. These extra particles can provide a dark matter candidate as well.

The production of $W^{\pm}H$, $ZH$, $W^+W^-$, and $W^\pm Z$ pairs probes non-Standard-Model interactions of quarks, gauge bosons, and the Higgs boson. New effects can be parameterized in terms of an effective field theory (EFT) where the Lagrangian is expanded in terms of higher-dimension operators suppressed by increasing powers of a high scale $\Lambda$. We examine the importance of including next-to-leading-order QCD corrections in global fits to the coefficients of the EFT. The numerical implications on the fits due to different approaches to enforcing the validity of the EFT are quantified. We pay particular attention to the dependence of the fits on the expansion in $1/\Lambda^2$ since the differences between results calculated at ${\cal {O}}(1/\Lambda^2)$ and ${\cal{O}}(1/\Lambda^4)$ may give insight into the possible significance of dimension-8 effects.

Despite great agreement with experiment, the Standard Model (SM) of particle physics lacks a viable Dark Matter (DM) candidate and sufficient amount of CP-violation to account for the observed baryon excess in the universe. Non-minimal Higgs frameworks are economic extensions of the SM which could remedy these shortcomings. Within the framework of a three Higgs doublet model, we introduce an extended dark sector which accommodates both DM and CP-violation. Such dark sources of CP-violation do not contribute to the Electric Dipole Moments and are therefore unconstrained. We present a novel mechanism in which the CP-violating dark particles only interact with the SM through the gauge bosons, primarily the $Z$ boson. Such $Z$-portal dark CP violation is realised in the regions of the parameter space where Higgs-mediated (co)annihilation processes are sub-dominant and have negligible contributions to the DM relic density. We show that such $Z$-portal CP violating DM can still thermalise and satisfy all experimental and observational bounds and discuss the implications of such phenomena for electroweak baryogenesis.

We study the anomalous $W^+W^-V$ ($V=\gamma,Z$) couplings in $e^+e^-\to W^+W^-$ using the complete set of polarization observables of $W$ boson with longitudinally polarized electron ($e^-$) and positron ($e^+$) beams. For the effective $W^+W^-V$ couplings, we use the most general Lorentz invariant form factor parametrization as well as $SU(2)\times U(1)$ invariant dimension-$6$ effective operators. We estimate simultaneous limits on the anomalous couplings using the Markov-Chain--Monte-Carlo (MCMC) method for an $e^+e^-$ collider running at center of mass energy of $\sqrt{s}=500$ GeV and the integrated luminosity of ${\cal L}=100$ fb$^{-1}$, $3.2$ ab$^{-1}$ and $4$ ab$^{-1}$. The best limits on the anomalous couplings are obtained for $e^-$ and $e^+$ polarization being $(\pm 0.8,\mp 0.6)$ for both $100$ fb$^{-1}$ and $3.2$ ab$^{-1}$ of luminosity.

In a model with an extra $U(1)$ gauge to SM gauge group, we have shown the allowed region of masses of extra gauge boson and the dark matter which is the lightest one among other right-handed Majorana fermions present in the model. To obtain this region, we have used bounds coming from constraints on active-sterile neutrino masses and mixing from various oscillation experiments, constraint on dark matter relic density obtained by PLANCK together with the constraint on the extra gauge boson mass and its gauge coupling recently obtained by ATLAS Collaboration at LHC. From the allowed regions, it is possible to get some lower bounds on the masses of the extra gauge boson and the dark matter and considering those values it is possible to infer what could be the spontaneous symmetry breaking scale of an extra $U(1)$ gauge symmetry.

We introduce a scenario for CP-violating (CPV) dark photon interactions in the context of non-Abelian kinetic mixing. Assuming an effective field theory that extends the Standard Model (SM) field content with an additional U(1) gauge boson (X) and a SU(2)L triplet scalar, we show that there exist both CP-conserving and CPV dimension five operators involving these new degrees of freedom and the SM SU(2)L gauge bosons. The former yields kinetic mixing between the X and the neutral SU(2)L gauge boson (yielding the dark photon), while the latter induces CPV interactions of the dark photon with the SM particles. We discuss experimental probes of these interactions using searches for permanent electric dipole moments (EDMs) and dijet correlations in high-energy pp collisions. It is found that the experimental limit on the electron EDM currently gives the strongest restriction on the CPV interaction. In principle, high-energy pp collisions provide a complementary probe through azimuthal angular correlations of the two forward tagging jets in vector boson fusion. In practice, observation of the associated CPV asymmetry is likely to be challenging.

We demonstrate that the classification of boosted, hadronically decaying, weak gauge bosons can be significantly improved over traditional cut-based and boosted decision tree-based methods using deep learning and the jet charge variable. We construct binary taggers for ${W}^{+}$ vs ${W}^{\ensuremath{-}}$ and $Z$ vs $W$ discrimination, as well as an overall ternary classifier for ${W}^{+}/{W}^{\ensuremath{-}}/Z$ discrimination. Besides a simple convolutional neural network, we also explore a composite of two simple convolutional neural networks, with different numbers of layers in the jet ${p}_{T}$ and jet charge channels. We find that this novel structure boosts the performance particularly when considering the $Z$ boson as a signal. The methods presented here can enhance the physics potential in Standard Model measurements and searches for new physics that are sensitive to the electric charge of weak gauge bosons.

We explore the generation of the baryon asymmetry in an extension of the Standard Model where the lepton number is promoted to a $U(1)_\ell$ gauge symmetry with an associated $Z^\prime$ gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. \cite{Carena:2018cjh}. Extra fermionic degrees of freedom - including a fermionic dark matter $\chi$ - are introduced in the dark sector for anomaly cancellation. Lepton number is spontaneously broken at high scale and the effective theory, containing the Standard Model, the $Z^\prime$, the fermionic dark matter, and an additional complex scalar field $S$, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for $\chi$, which in turn creates a chemical potential for the Standard Model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic $Z^\prime$, the dark matter candidate, the Higgs boson and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number $U(1)_B$ is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology., Comment: 44 pages, 12 figures, 1 table. v2 matches the published version

We present the first results for the $\mathcal{O}(\ensuremath{\alpha}{\ensuremath{\alpha}}_{s})$ corrections to the total partonic cross section of the process $q\overline{q}\ensuremath{\rightarrow}Z+X$, with the complete set of contributions, that include photonic and massive weak gauge boson effects. The results are relevant for the precise determination of the hadronic $Z$ boson production cross section. Virtual and real corrections are calculated analytically using the reduction to the master integrals and their evaluation through differential equations. Real corrections are dealt with using the reverse-unitarity method. They require the evaluation of a new set of two-loop master integrals, with up to three internal massive lines. In particular, three of them are expressed in terms of elliptic integrals. We verify the absence, at this perturbative order, of initial-state mass singularities proportional to a weak massive virtual correction to the quark-gluon splitting.

New gauge bosons at the MeV scale with tiny gauge couplings (so-called dark photons) can be responsible for the freeze-in production of dark matter and provide a clear target for present and future experiments. We study the effects of thermal mixing between dark photons and Standard Model gauge bosons and of the resulting plasmon decays on dark matter production before and after the electroweak phase transition. In the parameter regions preferred by the observed dark matter relic abundance, the dark photon is sufficiently long-lived to be probed with fixed-target experiments and light enough to induce direct detection signals. Indeed, current limits from XENON1T already constrain Dirac fermion dark matter in the GeV to TeV range produced via the freeze-in mechanism. We illustrate our findings for the case of a $U(1{)}_{B\ensuremath{-}L}$ gauge extension and discuss possible generalizations.

We consider the associated production of electroweak gauge bosons and charm or beauty quark jets at the LHC using the kT-factorization framework. We apply the transverse momentum dependent (TMD) parton distributions in a proton obtained from the parton branching (PB) method as well as from the Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation. For the PB approach, our prescription merges the standard leading order O(ααs) kT-factorization calculations with several tree-level next-to-leading order O(ααs2) off-shell production amplitudes. For the CCFM scenario, our consideration is based on the O(ααs2) off-shell gluon-gluon fusion subprocess g*g*→Z/W+QQ¯ and some O(ααs2) subprocesses involving quark interactions, taken into account in conventional (collinear) QCD factorization. We find that the W+c and Z+b cross sections, calculated within the PB and CCFM-based schemes with the proper choice of leading and next-to-leading subprocesses, are in good agreement with each other, thus establishing a correspondence between these two scenarios. A comparison with the latest LHC experimental data is given and the necessity for the proper off-shell treatment of the production amplitudes in determination of the parameters of the TMD parton density is demonstrated.

We propose a chiral Pati-Salam theory based on the gauge group $SU(4{)}_{C}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{L}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{R}$. The left-handed quarks and leptons are unified into a fundamental representation of $SU(4{)}_{C}$, while right-handed quarks and leptons have a separate treatment. The deviations measured in the rare semileptonic decays $B\ensuremath{\rightarrow}{D}^{(*)}\ensuremath{\tau}\overline{\ensuremath{\nu}}$ are explained by a scalar leptoquark which couples to right-handed fields and is contained in the $SU(4{)}_{C}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{R}$-breaking scalar multiplet. The measured deviation of lepton flavor universality in the rare decays $\overline{B}\ensuremath{\rightarrow}{\overline{K}}^{(*)}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$, $\ensuremath{\ell}=\ensuremath{\mu}$, $e$ is explained via the $SU(4{)}_{C}$ leptoquark gauge boson. The model predicts a new sub-GeV scale sterile neutrino which participates in the anomaly and can be searched for in upcoming neutrino experiments. The theory satisfies the current most sensitive experimental constraints and its allowable parameter regions will be probed as more precise measurements from the LHCb and Belle II experiments become available.

The nature of dark matter (DM) and how it might interact with the particles of the Standard Model (SM) is an ever-growing mystery. It is possible that the existence of new `dark sector' forces, yet undiscovered, are the key to solving this fundamental problem, and one might hope that in the future such forces might even be `unified' with the ones we already know in some UV-complete framework. In this paper, following a bottom-up approach, we attempt to take the first steps in the construction of such a framework. The much-discussed possibility of the kinetic mixing (KM) of the `dark photon' with the hypercharge gauge boson of the SM via loops of portal matter (PM) fields, charged in both sectors, offers an attractive starting point for these efforts. Given the anticipated finite strength of the KM in a UV-complete theory, the absence of anomalies, and the lifetime constraints on the PM fields arising from CMB and nucleosynthesis constraints, PM must behave as vector-like copies of the known SM fermion fields, such as those which appear naturally in $E_6$-type models. Within such a setup, the SM and their corresponding partner PM fields would be related by a new $SU(2)_I$ gauge symmetry. With this observation as a springboard, we construct a generalization of these ideas where $SU(2)_I$ is augmented by an additional $U(1)_{I_Y}$ factor so that the light dark photon is the result of a symmetry breaking analogous to the SM, \ie, $SU(2)_I\times U(1)_{I_Y}\to U(1)_D$, but with $U(1)_D$ now also broken at the $\lesssim$ GeV scale. While SM fields are $U(1)_D$ singlets, as in the conventional dark photon approach, they transform nontrivially under the full $SU(2)_I\times U(1)_{I_Y}$ gauge group. This approach leads to numerous interesting signatures, both at low energies and at colliders, and can be viewed as an initial step in the construction of a more UV-complete framework., Comment: 35 pages, 14 figures

We investigate the role of anomalous gauge boson and fermion couplings in the production of $WZ$ and ${W}^{+}{W}^{\ensuremath{-}}$ pairs at the LHC to next-to-leading-order (NLO) QCD in the Standard Model effective field theory (SMEFT), including dimension-six operators. Our results are implemented in a publicly available version of the powheg-box. We combine our $WZ$ results in the leptonic final state $e\ensuremath{\nu}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ with previous ${W}^{+}{W}^{\ensuremath{-}}$ results to demonstrate the numerical effects of NLO QCD corrections on the limits on effective couplings derived from ATLAS and CMS 8 and 13 TeV differential measurements. Our study demonstrates the importance of including NLO QCD SMEFT corrections in the $WZ$ analysis, while the effects on $WW$ production are smaller. We also show that the $\mathcal{O}(1/{\mathrm{\ensuremath{\Lambda}}}^{4})$ contributions dominate the analysis, where $\mathrm{\ensuremath{\Lambda}}$ is the high-energy scale associated with the SMEFT.

Five-dimensional domain walls in gauged $SU(5)$ generate a position-dependent symmetry breaking pattern along the additional dimension. We analize the perturbative stability and the 4D spectrum of these walls in the self-gravitating case, in terms of diffeomorphism- and Lie algebra gauge-invariant field fluctuations. We show that tachyonic modes are absent, ensuring perturbative stability. As expected, gravitational tensor and vector fluctuations behave like its counterparts in the standard $Z_2$ domain walls. All the Lie algebra valued fluctuations exhibit towers of 4D massive modes which propagate in the bulk, with a continuous spectrum starting from zero. All the would-be 4D Nambu-Goldstone fields, which are gravitationally trapped in the case of a global symmetry, are non-trivially absent. However we find no localizable 4D gauge bosons, either massless or massive. Instead, quasi-localizable discrete 4D massive modes for the gauge field fluctuations are found, along the spontaneously broken directions.

There are many hints that gravity is asymptotically safe. The inclusion of gravitational corrections can result in the ultraviolet fundamental standard model and constrain the Higgs mass to take the smallest value such that electroweak vacuum is stable. Taking into account the current top quark mass measurements, this value is mH≈130 GeV. This article considers the predictions of the Higgs mass in two minimal Beyond standard model scenarios, where the stability is improved. One is the sterile quark axion model, while the other is the U(1)B−L gauge symmetry model introducing a new massive Z′ gauge boson. The inclusion of Z′ boson gives the correct prediction for this mass, while inclusion of sterile quark(s) gives only a slight effect. Also a new, gravitational solution to the strong charge parity problem is discussed.

We derive general properties of the scale-dependent effective spectral dimensions of non-perturbative gauge boson propagators as they appear as solutions from different methods in Yang-Mills theories. In the ultraviolet and for short time scales the anomalous dimensions of the propagators lead to a slight decrease of the spectral dimension as compared to the one of a free propagator. Lowering the momentum scale, the spectral dimension decreases further. The class of propagators which display a maximum at Euclidean momenta, and thus violate positivity, always approaches a spectral dimension of one for large times. We also show that the longest time intervals are not related to the deep infrared but to the momentum scale defined by the position of the maximum., 12 pages, 8 figures; v2: added proofs in App. C, agrees with published version

We propose models for neutrino masses and mixing in the framework of low scale $U(1{)}_{{L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}}$ gauge extension of the standard model. The models are designed to spontaneously break $U(1{)}_{{L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}}$ so that the $U(1{)}_{{L}_{\ensuremath{\mu}}\ensuremath{-}{L}_{\ensuremath{\tau}}}$ gauge boson acquires an MeV scale mass, which is required to solve the longstanding problem of muon anomalous magnetic moment. Tiny neutrino masses are obtained by simultaneously invoking the linear and the inverse seesaw mechanism, and we succeed in realizing two types of one-zero textures in the active neutrino mass matrix. Both of the obtained textures favor inverted neutrino mass ordering and are testable in next generation experiments of neutrinoless double beta decay. We also show that some of extra scalar bosons can have MeV scale masses and would have significant impacts on observations of high energy cosmic neutrinos.

Author(s): Abazajian, Kevork N; Kusenko, Alexander | Abstract: We discuss numerous mechanisms for production of sterile neutrinos, which can account for all or a fraction of dark matter, and which can range from warm to effectively cold dark matter, depending on the cosmological scenario. We investigate production by Higgs boson decay, $(B-L)$ gauge boson production at high temperature, as well as production via resonant and nonresonant neutrino oscillations. We calculate the effects on structure formation in these models, some for the first time. If two populations of sterile neutrinos, one warm and one cold, were produced by different mechanisms, or if sterile neutrinos account for only a fraction of dark matter, while the remainder is some other cold dark matter particle, the resulting multi-component dark matter may alleviate some problems in galaxy formation. We examine the X-ray constraints and the candidate signal at 3.5 keV. Finally, we also show that the $\sigma_8$ problem can be a signature of fractional dark matter in the form of sterile neutrinos in several mechanisms.

We study a classically scale-invariant model with an electroweak singlet complex scalar mediator together with an anomaly free set of two fermionic dark matters. We introduce $U(1)_X$ gauge symmetry with a new charge $X$ in the dark sector in order to stabilize the mass of the scalar singlet with a new gauge boson. Our conformally invariant scalar potential generates the electroweak symmetry breaking via the Coleman-Weinberg mechanism, and the new scalar singlet acquires its mass through radiative corrections of the fermionic dark matters and the new gauge boson as well as of the SM particles. Taking into account the collider bounds, we present the allowed region of new physics parameters satisfying the recent measurement of relic abundance. With the obtained parameter sets, we predict the elastic scattering cross section of the new singlet fermions into target nuclei for a direct detection of the dark matter. We also discuss the collider signatures and future discovery potentials of the new scalar and gauge boson., Comment: 12 pages, 11 figures, journal version including minor corrections. arXiv admin note: text overlap with arXiv:1904.10209

The standard wisdom on the origin of massless bosons in the spectrum of a Quantum Field Theory $(QFT)$ describing the interaction of gauge fields coupled to matter fields is based on two well known features: gauge symmetry, and spontaneous symmetry breaking of continuous global symmetries. However we will show in this article how the topological properties, that originate the $U(1)_A$ axial anomaly in a $QFT$ which describes the interaction of fermion matter fields and gauge bosons, are the basis of an alternative mechanism to generate massless bosons in the chiral limit, if the non-abelian $SU(N_f)_A$ chiral symmetry is fulfilled in the vacuum. We will also test our predictions with the results of a well known two-dimensional model, the two-flavour Schwinger model, which was analyzed by Coleman long ago, and will give a reliable answer to some of the questions he asked himself on the spectrum of the model in the strong-coupling (chiral) limit. We will also analyze what are the expectations for the $U(N)$ gauge-fermion model in two dimensions, and will discuss on the impact of our results in the chirally symmetric high temperature phase of $QCD$, which was present in the early universe, and is expected to be created in heavy-ion collision experiments.