Search

The observation of the electroweak production of a W boson and a photon in association with two jets, using pp collision data at the Large Hadron Collider at a centre of mass energy of s = 13 TeV, is reported. The data were recorded by the ATLAS experiment from 2015 to 2018 and correspond to an integrated luminosity of 140 fb - 1 . This process is sensitive to the quartic gauge boson couplings via the vector boson scattering mechanism and provides a stringent test of the electroweak sector of the Standard Model. Events are selected if they contain one electron or muon, missing transverse momentum, at least one photon, and two jets. Multivariate techniques are used to distinguish the electroweak W γ j j process from irreducible background processes. The observed significance of the electroweak W γ j j process is well above six standard deviations, compared to an expected significance of 6.3 standard deviations. Fiducial and differential cross sections are measured in a fiducial phase space close to the detector acceptance, which are in reasonable agreement with leading order Standard Model predictions from MadGraph5+Pythia8 and Sherpa. The results are used to constrain new physics effects in the context of an effective field theory. [ABSTRACT FROM AUTHOR]

Extensions of the Standard Model with masses at or below the GeV scale are motivated by searches for dark matter and precision measurements in the quark and lepton flavour sectors, including that of the muon anomalous magnetic moment. An excellent experimental environment to test such light new physics is given by the Belle II experiment, which foresees to take up to 50 ab−1 of data. Here we consider a model with an additional gauged U 1 L μ − L τ symmetry that introduces a neutral gauge boson, a Dark Photon, with possibly large couplings to muon- and tau-flavored leptons, including neutrinos. Dark Photon mixing with the Standard Model photon is loop induced, allowing it to couple to electrically charged fermions other than muons and taus. We systematically investigate the possible search strategies for Dark Photons with four fermion final states. We identified search channels with muons as the most promising ones, and we analyse the kinematic distributions to obtain cuts that optimise the sensitivity of Belle II searches for the Dark Photon. Summarising the sensitivities from the most promising search channels we provide a comprehensive overview of future searches at Belle II. [ABSTRACT FROM AUTHOR]

This paper aims to explore the implications of U (1) L e − L α gauge symmetries, where α = τ , μ , in the neutrino sector through type-(I+II) seesaw mechanisms. To achieve such a hybrid framework, we include a scalar triplet and three right-handed neutrinos. The model can successfully account for the active neutrino masses, mixing angles, mass squared differences, and the CP-violating phase within the 3 σ bounds of NuFit v5.2 neutrino oscillation data. The presence of a new gauge boson at the MeV scale provides an explanation for the muon and electron (g − 2) within the confines of their experimental limits. Furthermore, we scrutinize the proposed models in the context of upcoming long-baseline neutrino experiments such as DUNE, P2SO, T2HK, and T2HKK. The findings reveal that P2SO and T2HK have the ability to probe both models in their 5 σ -allowed oscillation parameter region, whereas DUNE and T2HKK can conclusively test only the model with U (1) L e − L μ -symmetry within the 5 σ parameter space if the true values of the oscillation parameters remain consistent with NuFit v5.2. [ABSTRACT FROM AUTHOR]

Axion-like particles (ALPs), which are pseudo-scalar particles, appear in various new physics models with the spontaneous global symmetry breaking. The difference between ALPs and axion models is that for the former both masses and couplings of ALPs are free parameters. It appears that the ALPs with masses above 1 GeV are beyond the reach of low-energy accelerators, existing cosmological and astrophysical constraints, while high-energy colliders provide unique possibilities to explore such particles. With the establishment of the International Muon Collider Collaboration, muon colliders have been widely concerned. In general, ALPs are mainly produced at muon colliders through the μ + μ − annihilation and electroweak vector-boson-fusion (VBF) processes. In this paper, we study the prospect of the production of heavy ALPs with mass greater than 10 GeV via the massless γ γ -fusion process at the multi-TeV muon collider. Focusing on the couplings of ALPs to the Standard Model gauge bosons, we obtain the excluding and discovering capabilities for ALPs at the 3 TeV and 10 TeV muon colliders. Our numerical results suggest that the multi-TeV muon collider may be more sensitive to ALPs with the mass of 35–400 GeV than LHC, and can provide the possibility to search for ALPs with masses greater than 3 TeV. In addition, we also discuss the effect of narrow width approximation on the ALP search sensitivity. [ABSTRACT FROM AUTHOR]

In this work manifestations of physics beyond the Standard Model are parameterized with higher-dimension operators and Wilson coefficients using effective field theory. In order to set more stringent experimental limits on the Wilson coefficients it is crucial to use new methods of sensitivity increasing that work independently with luminosity growth. Method of composite anomalous signal allows one to set the limits on Wilson coefficients more precisely and stringent by accounting for impact of EFT operators on background processes in addition to the conventional anomalous contribution from the signal process. This work presents aforementioned methodology applied to the production, that is sensitive to the neutral triple couplings of gauge bosons and . It is found that the main background BSM contribution comes from background. Improvement of the limits on the Wilson coefficients due to this background depends on the coefficient and is up to 57.5 (59.1 ) for one- (two-) dimensional limits in linear quadratic effective field theory model and up to 94.4 for one-dimensional limits in linear effective field theory model. [ABSTRACT FROM AUTHOR]

There is growing interest in the development of a muon collider that would make it possible to produce lepton collisions at energies of several TeV. Among others, there can be significant contributions to electroweak gauge boson, Higgs boson, and top quark physics. In this work, we pay attention to the latter, in particular, effective flavor‐changing (FC) top‐quark interactions. We discuss the flavor‐changing tq¯q=u,c production processes that can be a good probe of the dimension‐six top quark four‐fermion and fermion‐boson operators in the SMEFT. We consider all sixteen operators that can generate flavor‐changing top quark couplings. After comparing with the current LHC bounds, we find potential limits three or four orders of magnitude stronger for four‐fermion operators. Concerning fermion‐boson couplings, for the tensor operators QuW and QuB, we obtain the highest sensitivity. We also observe that the effective W approximation (EWA) does not apply with QuB. [ABSTRACT FROM AUTHOR]

I consider the electro-weak (EW) masses and interactions generated by photons using vacuum expectation values of Stueckelberg and Higgs fields. I provide a prescription to relate their parametric values to a cosmological range derived from the fundamental Heisenberg uncertainty principle and the Einstein–de Sitter cosmological constant and horizon. This yields qualitative connections between microscopic ranges acquired by W ± or Z 0 gauge Bosons and the cosmological scale and minimal mass acquired by g-photons. I apply this procedure to an established Stueckelberg–Higgs mechanism, while I consider a similar procedure for a pair of Higgs fields that may spontaneously break all U(1) × SU(2) gauge invariances. My estimates of photon masses and their additional parity-breaking interactions with leptons and neutrinos may be detectable in suitable accelerator experiments. Their effects may also be observable astronomically through massive g-photon condensates that may contribute to dark matter and dark energy. [ABSTRACT FROM AUTHOR]

We discuss gravitational waves (GWs) in an electroweakly interacting vector dark matter (DM) model. In the model, the electroweak gauge symmetry is extended to SU(2) |$_0 \times$| SU(2) |$_1 \times$| SU(2) |$_2 \times$| U(1) |$_Y$| and spontaneously broken into SU(2) |$_L \times$| U(1) |$_Y$| at TeV scale. The model has an exchange symmetry between SU(2) |$_0$| and SU(2) |$_2$|⁠. This symmetry stabilizes some massive vector bosons associated with the spontaneous symmetry breaking described above, and an electrically neutral one is a DM candidate. In a previous study, it was found that the gauge couplings of SU(2) |$_0$| and SU(2) |$_1$| are relatively large to explain the measured value of the DM energy density via the freeze-out mechanism. With the large gauge couplings, the gauge bosons potentially have a sizable effect on the scalar potential. In this paper, we focus on the phase transition of SU(2) |$_0 \times$| SU(2) |$_1 \times$| SU(2) |$_2 \rightarrow$| SU(2) |$_L$|⁠. We calculate the effective potential at finite temperature and find that the phase transition is first-order and strong in a wide range of the parameter space. The strong first-order phase transition generates GWs. We calculate the GW spectrum and find that it will be possible to detect the GWs predicted in the model by future space-based GW interferometers. We explore the regions of the parameter space probed by the GW detection. We find that the GW detection can probe the region where the mass of |$h^{\prime }$|⁠ , a CP-even scalar in the model, is a few TeV. [ABSTRACT FROM AUTHOR]

The one-loop contributions to the flavor-changing neutral current decays of the top quark into a light quark and a gauge boson or Higgs boson, namely, t → q V , q h , with q being u or c, and V being γ , g, or Z, are analyzed in this study within the framework of the minimal R-symmetric supersymmetric standard model. The charginos in this model have been separated into two sets, i.e. χ -chargino and ρ -chargino. The numerical results reveal that gluino or ρ -chargino predominantly dictate the predictions for BR (t → q V , q h), while the impact of neutralino or χ -chargino contributions is insignificant. By incorporating the constraints imposed by the squark mixing parameters from B ̄ → X s γ and B d , s 0 → μ + μ − , the theoretical predictions for BR(t → q g) can be significantly augmented to approximately (1 0 − 5 − 1 0 − 6). On the other hand, the values of BR(t → q γ , q Z , q h) are predicted to be at least four orders of magnitude below the current experimental limits. [ABSTRACT FROM AUTHOR]

In this work we explore the phenomenological implications at future e + e - colliders of assuming anomalous couplings of the Higgs boson to gauge bosons HVV and HHVV (V = W , Z) given by the κ -modifiers with respect to the Standard Model couplings, κ V and κ 2 V , respectively. For this study we use the Higgs Effective Field Theory (HEFT) where these two κ parameters are identified with the two most relevant effective couplings at leading order, concretely a = κ V and b = κ 2 V. Our focus is put on these two couplings and their potential correlations which we believe carry interesting information on the underlying ultraviolet theory. The particular studied process is e + e - → H H ν ν ¯ , where the vector boson scattering subprocess W W → H H plays a central role, specially at the largest planned energy colliders. Our detailed study of this process as a function of the energy and the angular variables indicates that the produced Higgs bosons in the BSM scenarios will have in general a high transversality as compared to the SM case if κ V 2 ≠ κ 2 V. In order to enhance the sensitivity to these HEFT parameters κ V and κ 2 V and their potential correlations we propose here some selected differential cross sections for the e + e - → H H ν ν ¯ process, where different kinematic properties of the BSM case with respect to the SM are manifested. Finally, we will focus on the dominant Higgs decays to b b ¯ pairs leading to final events with 4 b-jets and missing transverse energy from the undetected neutrinos and will provide the expected accessibility to the (κ V , κ 2 V) effective couplings and their potential correlations. In our study we will consider the three projected energies for e + e - colliders of 500 GeV, 1000 GeV and 3000 GeV. [ABSTRACT FROM AUTHOR]

We investigate self-conjugate Dark Matter (DM) particles that primarily interact with Standard Model (SM) electroweak gauge bosons within an effective field theoretical framework. Our analysis focuses on effective contact interactions, invariant under the SM gauge group, between Majorana fermions, and real scalar DM, with SM neutral electroweak gauge bosons. We calculate the Wilson coefficients for interaction terms up to dimension-8 and establish constraints on the theory's parameters. These constraints are derived from the observed relic density, and indirect detection observations. We discuss the potential for DM–nucleon scattering in direct detection experiments. Additionally, we utilize low-energy Large Electron–Positron (LEP) data to assess sensitivity to the pair production of low-mass (≤ 8 0 GeV) DM particles. Furthermore, we highlight the potential of the proposed International Linear Collider (ILC) in probing effective operators through the pair production of DM particles with masses ≥ 5 0 GeV in association with mono-photons. [ABSTRACT FROM AUTHOR]

Despite the discovery of the Higgs boson, the Higgs sector of the standard model is still not fully established. In particular, the self-couplings of the Higgs boson, and its couplings with gauge bosons, are still to be fully determined. We consider electroweak corrections to the process H → ν e ν ̄ e ν μ ν ̄ μ . The corrections depend on the H H H and Z Z H H couplings. We investigate this dependence in κ -framework. We find that the width depends on H H H coupling significantly. The dependence on Z Z H H coupling is only marginal. We also discuss the dependence on Z Z W W coupling. [ABSTRACT FROM AUTHOR]

Carrollian holography is supposed to describe gravity in four-dimensional asymptotically flat space-time by the three-dimensional Carrollian CFT living at null infinity. We transform superstring scattering amplitudes into the correlation functions of primary fields of Carrollian CFT depending on the three-dimensional coordinates of the celestial sphere and a retarded time coordinate. The power series in the inverse string tension is converted to a whole tower of both UV and IR finite descendants of the underlying field-theoretical Carrollian amplitude. We focus on four-point amplitudes involving gauge bosons and gravitons in type I open superstring theory and in closed heterotic superstring theory at the tree-level. We also discuss the limit of infinite retarded time coordinates, where the string world-sheet becomes celestial. [ABSTRACT FROM AUTHOR]

We revisit the gauged U(1)B−L explanation of the ATOMKI nuclear anomalies, in which the new gauge boson is the hypothetical X(17) particle. It is known that the vanilla B − L scenario is unable to account for appropriate couplings, namely the suppression of the couplings of X(17) to neutrinos, which motivates adding vector-like leptons. The simplest case, in which the new fields have B − L charges equal to 1, is highly disfavoured since it requires large mixing with the Standard Model fields. One solution recently put forward is to consider large B − L charges to counterbalance small mixing. We show that, in this scenario, and after taking into account several phenomenological constraints, the dominant contribution to the muon anomalous magnetic moment (g − 2)μ is expected to be extremely large and with a negative sign, being thus excluded by experiment. [ABSTRACT FROM AUTHOR]

Proton-proton collisions at the LHC generate a high-intensity collimated beam of neutrinos in the forward (beam) direction, characterised by energies of up to several TeV. The recent observation of LHC neutrinos by FASER ν and SND@LHC signifies that this previously overlooked particle beam is now available for scientific investigation. Here we quantify the impact that neutrino deep-inelastic scattering (DIS) measurements at the LHC would have on the parton distributions (PDFs) of protons and heavy nuclei. We generate projections for DIS structure functions for FASER ν and SND@LHC at Run III, as well as for the FASER ν 2, AdvSND, and FLArE experiments to be hosted at the proposed Forward Physics Facility (FPF) operating concurrently with the High-Luminosity LHC (HL-LHC). We determine that up to one million electron-neutrino and muon-neutrino DIS interactions within detector acceptance can be expected by the end of the HL-LHC, covering a kinematic region in x and Q 2 overlapping with that of the Electron-Ion Collider. Including these DIS projections in global (n)PDF analyses, specifically PDF4LHC21, NNPDF4.0, and EPPS21, reveals a significant reduction in PDF uncertainties, in particular for strangeness and the up and down valence PDFs. We show that LHC neutrino data enable improved theoretical predictions for core processes at the HL-LHC, such as Higgs and weak gauge boson production. Our analysis demonstrates that exploiting the LHC neutrino beam effectively provides CERN with a "Neutrino-Ion Collider" without requiring modifications in its accelerator infrastructure. [ABSTRACT FROM AUTHOR]

A non-Abelian theory of fermions interacting with gauge bosons, the constrained system, is studied. The equations of motion for a singular system are obtained as total differential equations in many variables. The integrability conditions are investigated, and the set of equations of motion is integrable. The Senjanovic and the canonical methods are used to quantize the system, and the integration is taken over the canonical phase space coordinates. [ABSTRACT FROM AUTHOR]

Universal factors associated with the emission of a soft boson in gauge theories and gravity, formulated in the light‐cone gauge, are presented. The inverse‐soft method, for constructing higher‐point amplitudes from lower‐point ones, using these factors is reviewed. These ideas are then examined in (light‐cone) superspace and applied to both the N=4$\mathcal {N}=4$ super Yang–Mills and N=8$\mathcal {N}=8$ supergravity theories. One highlight is a compact result for the quartic interaction vertex in N=8$\mathcal {N}=8$ supergravity, a crucial ingredient for finiteness analyses. Universal factors associated with the emission of a soft boson in gauge theories and gravity, formulated in the light‐cone gauge, are presented. The inverse‐soft method, for constructing higher‐point amplitudes from lower‐point ones, using these factors is reviewed. These ideas are then examined in (light‐cone) superspace and applied to both the N=4$\mathcal{N} = 4$ super Yang–Mills and N=8$\mathcal{N} = 8$ supergravity theories. One highlight is a compact result for the quartic interaction vertex in N=8$\mathcal{N} = 8$ supergravity, a crucial ingredient for finiteness analyses. [ABSTRACT FROM AUTHOR]

Left Right Symmetric Model (LRSM) being an extension of the Standard model of particle physics incorporates within itself Type-I and Type-II seesaw mass terms naturally. Both the mass terms can have significant amount of contribution to the resulting light neutrino mass within the model and hence on the different phenomenology associated within. In this paper, we have thoroughly analyzed and discussed the implications of specifying different weightages to both the mass terms and also the study has been carried out for different values of which is mass of the right-handed gauge boson. This paper also gives a deeper insight into the new physics contributions of Neutrinoless Double Beta Decay (0νββ) and their variations with the net baryon asymmetry arising out of the model. Therefore, the main objective of the present paper rests on investigating the implications of imposing different weightage to the type-I and type-II seesaw terms and different values of on the new physics contributions of 0νββ and net baryon asymmetry arising out as a result of resonant leptogenesis. LRSM in this work has been realized using modular group of level 3, Γ(3) which is isomorphic to non-abelian discrete symmetry group A4, the advantage being the non-requirement of flavons within the model and hence maintaining the minimality of the model. [ABSTRACT FROM AUTHOR]

Flavour changing neutral current (FCNC) processes are described by loop diagrams in the Standard Model (SM), while in 331 models, based on the gauge group SU (3) C × SU (3) L × U (1) X , they are dominated by tree-level exchanges of a new heavy neutral gauge boson Z ′ . By exploiting this feature, observables related to FCNC decays of K, B d and B s mesons can be considered in several variants of 331 models. The variants are distinguished by the value of a parameter β that plays a key role in this framework. Imposing constraints on the Δ F = 2 observables, we select possible ranges for the mass of the Z ′ boson in correspondence to the values β = ± k / 3 , with k = 1 , 2 . The results are used to determine the impact of 331 models on b → s processes and on the correlations among them, in the light of new experimental data recently released. [ABSTRACT FROM AUTHOR]

We consider a minimal renormalizable non-supersymmetric E 6 Grand Unified Theory using fundamental representation 27 for fermions and scalars. The scalar with adjoint representation 78 is also taken for direct breaking of E 6 to SM. The proposed model, guided by TeV-scale vector-like fermions and scalar leptoquark, offers successful gauge unification even in the absence of any intermediate symmetry. Embedded with threshold corrections, it is shown to be compatible with the present experimental limit on proton decay lifetime. The unique feature of the model shows that the GUT threshold corrections to the unification mass is controlled by superheavy gauge bosons only, thereby minimizing the uncertainty of the GUT predictions. The scalar leptoquark and vector-like fermions residing in 27 representation can explain flavor physics anomalies like R D (∗) as reported by the LHCb collaboration and the muon anomalous magnetic moment reported by the recent muon g − 2 experiment at Fermilab. The model can also predict a sub-eV scale neutrino at one-loop level via exchange of W and Z gauge bosons through MRIS mechanism. [ABSTRACT FROM AUTHOR]

While the third run of the Large Hadron Collider (LHC) is ongoing, the underlying theory that extends the Standard Model remains so far unknown. Left-Right Models (LRMs) introduce a new gauge sector, and can restore parity symmetry at high enough energies. If LRMs are indeed realized in nature, the mediators of the new weak force can be searched for in colliders via their direct production. We recast existing experimental limits from the LHC Run 2 and derive generic bounds on the masses of the heavy LRM gauge bosons. As a novelty, we discuss the dependence of the WR and ZR total width on the LRM scalar content, obtaining model-independent bounds within the specific realizations of the LRM scalar sectors analysed here. These bounds avoid the need to detail the spectrum of the scalar sector, and apply in the general case where no discrete symmetry is enforced. Moreover, we emphasize the impact on the WR production at LHC of general textures of the right-handed quark mixing matrix without manifest left-right symmetry. We find that the WR and ZR masses are constrained to lie above 2 TeV and 4 TeV, respectively. [ABSTRACT FROM AUTHOR]

We consider an extension of the Standard Model of particle physics with an additional SU(2) gauge sector along with an additional scalar bidoublet and a non-linear sigma field. The neutral components of the bidoublet serve as dark matter candidates by virtue of the bidoublet being odd under a Z 2 symmetry. Generic beyond Standard Model constraints like vacuum stability, invisible decay of Higgs, Higgs alignment limit and collider constraints on heavy gauge bosons restrict the parameter space of this model. In this multicomponent dark matter scenario, we investigate the interplay between the annihilation and co-annihilation channels originating from the new gauge sector as those contribute to the relic abundance. We also inspect the direct detection constraints on scattering cross-sections of the dark matter particles with the detector nucleons and present our observations. [ABSTRACT FROM AUTHOR]

We perform a collider search for fatjet signals originating from boosted heavy neutral and charged leptons with masses between a few hundred GeV to a TeV. These heavy leptons originate from the decay of heavy gauge bosons with masses above 4 TeV in a left-right symmetric extension of the Standard Model (SM), which considers a universal seesaw mechanism for the generation of all the SM fermion masses. The fatjet signals arise naturally in this model due to the presence of heavy seesaw partners of the SM fermions which decay to SM gauge bosons carrying large boosts. We employ substructure based variables lepton sub-jet fraction (LSF) and lepton mass drop (LMD) together with kinematic variables of fatjets to look for fatjet signals associated with non-isolated leptons. These variables help in reducing the SM backgrounds while retaining enough statistics for signal events, which leads to a robust discovery potential at the high-luminosity Large Hadron Collider (HL-LHC). [ABSTRACT FROM AUTHOR]

In the "Domain-Wall Standard Model," all the Standard Model (SM) fields are localized in certain domains in a non-compact 5D space-time. While the SM is realized as a 4D effective theory at low energies, the model involves Kaluza–Klein (KK) modes of the SM particles. In this paper we introduce two simple solvable examples which lead to domain-wall configurations for the SM particles and their KK-modes. Based on the examples, we address a variety of phenomenologies of the Domain-Wall SM, such as the KK-mode gauge boson phenomenology at the Large Hadron Collider (LHC), the effect of the KK-mode SM fermions on Higgs boson phenomenology, and the KK-mode fermion search at the LHC with its decay into a corresponding SM fermion and a Nambu–Goldstone boson associated with a spontaneous breaking of the translational invariance in the 5th dimension. We also propose a simple unified picture of localizing all the SM fields. [ABSTRACT FROM AUTHOR]

It is essential to directly investigate the self-couplings of gauge bosons in the Standard Model (SM) due to its non-Abelian nature, as these couplings play a significant role in comprehending the gauge structure of the model. The discrepancies between the Standard Model's expectations and the measured value of gauge boson self-couplings serve as strong evidence for new physics phenomena extending beyond the Standard Model. Such deviations provide valuable insights into the nature of new physics and potentially lead to a deeper understanding of fundamental particles and their interactions. This study examines the sensitivities of anomalous couplings associated with dimension-8 operators that affect the γ γ γ γ and Z γ γ γ quartic vertices. The study focuses on the process e - γ → e - γ γ with the incoming photon under Weizsäcker-Williams approximation at the stage-3 scenario of Compact Linear Collider (CLIC) that refers to a CoM energy of 3 TeV. Due to the CLIC options, we take into account both unpolarized and ∓ 80 % polarized electron beam with the related integrated luminosities of L = 5 , 4 , 1 ab - 1 under the systematic uncertainties of δ sys = 0 , 3 , 5 . Obtained sensitivities on the anomalous quartic gauge couplings (aQGCs) for the process e - γ → e - γ γ at s = 3 TeV and various polarizations are improved by a factor of 2–200 times better for the couplings f T , j / Λ 4 compared with the experimental results reported by CMS Collaboration in Tumasyan et al. (JHEP 10:174, 2021). [ABSTRACT FROM AUTHOR]

The rho meson has long been successfully identified with a dynamical gauge boson of Hidden Local Symmetry (HLS) H local in the non-linear sigma model G / H gauge equivalent to the model having the symmetry G global × H local , with G = [ S U (2) L × S U (2) R ] ≃ O (4) , H = S U (2) V ≃ O (3) . However, under a hitherto unproven assumption that its kinetic term is dynamically generated, together with an ad hoc choice of the auxiliary field parameter " a = 2 ", we prove this assumption, thereby solving the long-standing mystery. The rho meson kinetic term is generated simply by the large N limit of the Grassmannian model G / H = O (N) / [ O (N − 3) × O (3) ] gauge equivalent to O (N) global × [ O (N − 3) × O (3) ] local , extrapolated to N = 4 , O (4) global × O (3) local , with all the phenomenologically successful " a = 2 results", i.e., ρ -universality, KSRF relation, and the Vector Meson Dominance, realized independently of the parameter "a". This in turn establishes validity of the large N dynamics at the quantitative level directly by the experiments. The relevant cutoff reads Λ ≃ 4 π F π for N = 4 , which is regarded as a matching scale of the HLS as a "magnetic dual" to QCD. Skyrmion is stabilized by such a dynamically generated rho meson without recourse to the underlying QCD, a further signal of the duality. The unbroken phase with a massless rho meson may be realized as a novel chiral-restored hadronic phase in the hot/dense QCD. [ABSTRACT FROM AUTHOR]

We elaborate the possibility of using the atomic radiative emission of neutrino pair (RENP) to probe the neutrino electromagnetic properties, including magnetic and electric dipole moments, charge radius, and anapole. With the typical O (eV) momentum transfer, the atomic RENP is sensitive to not just the tiny neutrino masses but also very light mediators to which the massless photon belongs. The neutrino EM properties introduce extra contribution besides the SM one induced by the heavy W/Z gauge bosons. Since the associated photon spectrum is divided into several sections whose boundaries are determined by the final-state neutrino masses, it is possible to identify the individual neutrino EM form factor elements. Most importantly, scanning the photon spectrum inside the particular section with deviation from the SM prediction once observed allows identification of the neutrino EM form factor type. The RENP provides an ultimate way of disentangling the neutrino EM properties to go beyond the current experimental searches or observations. [ABSTRACT FROM AUTHOR]

A search for a new massive charged gauge boson, W′, is performed with the ATLAS detector at the LHC. The dataset used in this analysis was collected from proton-proton collisions at a centre-of-mass energy of s = 13 TeV, and corresponds to an integrated luminosity of 139 fb−1. The reconstructed tb invariant mass is used to search for a W′ boson decaying into a top quark and a bottom quark. The result is interpreted in terms of a W′ boson with purely right-handed or left-handed chirality in a mass range of 0.5–6 TeV. Different values for the coupling of the W′ boson to the top and bottom quarks are considered, taking into account interference with single-top-quark production in the s-channel. No significant deviation from the background prediction is observed. The results are expressed as upper limits on the W′ → tb production cross-section times branching ratio as a function of the W′-boson mass and in the plane of the coupling vs the W′-boson mass. [ABSTRACT FROM AUTHOR]

The QED hadronic vacuum polarization function plays an important role in the determination of precision electroweak observables and of the anomalous magnetic moment of the muon. These contributions have been computed from data, by means of dispersion relations affecting the electron positron hadronic cross sections, or by first principle lattice-QCD computations in the Standard Model. Today there is a discrepancy between the two approaches for determining these contributions, which affects the comparison of the measurement of the anomalous magnetic moment of the muon with the theoretical predictions. In this article, we revisit the idea that this discrepancy may be explained by the presence of a new light gauge boson that couples to the first generation quark and leptons and has a mass below the GeV scale. We discuss the requirements for its consistency with observations and the phenomenological implications of such a gauge extension. [ABSTRACT FROM AUTHOR]

Pair production of heavy vector bosons is a key process at colliders: it allows to test our understanding of the Standard Model and to explore the existence of new physics through precision measurements of production rates and differential distributions. New physics effects can be subtle and often require observables specifically designed for their detection. In this study, we focus on quantum information observables that characterise the spin states of the final diboson system. We analyse concurrence bounds, purity, and Bell inequalities for a bipartite qutrit system representing two massive gauge bosons. Our findings show that quantum spin observables can serve as complementary probes for heavy new physics as parametrised by higher dimensional operators in the Standard Model effective field theory. In particular, we find that these observables offer increased sensitivity to operators whose contributions do not interfere with the Standard Model amplitudes at the level of differential cross sections. [ABSTRACT FROM AUTHOR]

We study the phenomenology of leptophilic Z′ gauge bosons at the future high-energy e+e− and μ+μ− colliders, as well as at the gravitational wave observatories. The leptophilic Z′ model, although well-motivated, remains largely unconstrained from current low-energy and collider searches for Z′ masses above O (100 GeV), thus providing a unique opportunity for future lepton colliders. Taking U 1 L α − L β (α, β = e, μ, τ) models as concrete examples, we show that future e+e− and μ+μ− colliders with multi-TeV center-of-mass energies provide unprecedented sensitivity to heavy leptophilic Z′ bosons. Moreover, if these U(1) models are classically scale-invariant, the phase transition at the U(1) symmetry-breaking scale tends to be strongly first-order with ultra-supercooling, and leads to observable stochastic gravitational wave signatures. We find that the future sensitivity of gravitational wave observatories, such as advanced LIGO-VIRGO and Cosmic Explorer, can be complementary to the collider experiments, probing higher Z′ masses up to O (104 TeV), while being consistent with naturalness and perturbativity considerations. [ABSTRACT FROM AUTHOR]

The defect of the angular momentum of an electron under cyclotron (synchrotron) radiation, including in terms of its spatial orientation, as well as the spatial orientation of the emitted photon, is considered. The possibility of the compatibility of the idea of the photon as a gauge boson, which can exist only in two spin states, ±1, with a linearly polarized photon, i.e., having no spin, has been studied. It is established that photons have no spin. The angular momentum defect can carry away a spinless photon. As applied to the angular momentum defect, the photon momentum arm is equal to its reduced wavelength. [ABSTRACT FROM AUTHOR]

A search for heavy right-handed Majorana or Dirac neutrinos N R and heavy right-handed gauge bosons W R is performed in events with energetic electrons or muons, with the same or opposite electric charge, and energetic jets. The search is carried out separately for topologies of clearly separated final-state products ("resolved" channel) and topologies with boosted final states with hadronic and/or leptonic products partially overlapping and reconstructed as a large-radius jet ("boosted" channel). The events are selected from pp collision data at the LHC with an integrated luminosity of 139 fb - 1 collected by the ATLAS detector at s = 13 TeV. No significant deviations from the Standard Model predictions are observed. The results are interpreted within the theoretical framework of a left-right symmetric model, and lower limits are set on masses in the heavy right-handed W R boson and N R plane. The excluded region extends to about m (W R) = 6.4 TeV for both Majorana and Dirac N R neutrinos at m (N R) < 1 TeV. N R with masses of less than 3.5 (3.6) TeV are excluded in the electron (muon) channel at m (W R) = 4.8 TeV for the Majorana neutrinos, and limits of m (N R) up to 3.6 TeV for m (W R) = 5.2 (5.0) TeV in the electron (muon) channel are set for the Dirac neutrinos. These constitute the most stringent exclusion limits to date for the model considered. [ABSTRACT FROM AUTHOR]

We perform a detailed study of the b → c τν and b → sl + l − processes in a minimal flipped 331 model based on the SU (3) C × SU (3) L × U (1) X gauge symmetry. The non-universal SU (3) L × U (1) X symmetry in the lepton sector gives rise to non-universal neutral and charged currents involving heavy non-SM gauge bosons and SM leptons that yield radiative contributions to the b → s, b → c, s → u , and d → u transitions arising from one-loop-level penguin and box diagrams. We find that the observables related to these transitions agree with their experimental values in a region of parameter space that includes TeV-scale exotic up-type quarks, within the reach of the Large Hadron Collider. [ABSTRACT FROM AUTHOR]

The QED hadronic vacuum polarization function plays an important role in the determination of precision electroweak observables and of the anomalous magnetic moment of the muon. These contributions have been computed from data, by means of dispersion relations affecting the electron positron hadronic cross sections, or by first principle lattice-QCD computations in the Standard Model. Today there is a discrepancy between the two approaches for determining these contributions, which affects the comparison of the measurement of the anomalous magnetic moment of the muon with the theoretical predictions. In this article, we revisit the idea that this discrepancy may be explained by the presence of a new light gauge boson that couples to the first generation quark and leptons and has a mass below the GeV scale. We discuss the requirements for its consistency with observations and the phenomenological implications of such a gauge extension. [ABSTRACT FROM AUTHOR]

We present a detailed study of the production of dark matter in the form of a sterile neutrino via freeze-in from decays of heavy right-handed neutrinos. Our treatment accounts for thermal effects in the effective couplings, generated via neutrino mixing, of the new heavy neutrinos with the Standard Model gauge and Higgs bosons and can be applied to several low-energy fermion seesaw scenarios featuring heavy neutrinos in thermal equilibrium with the primordial plasma. We find that the production of dark matter is not as suppressed as to what is found when considering only Standard Model gauge interactions. Our study shows that the freeze-in dark matter production could be efficient. [ABSTRACT FROM AUTHOR]

The bootstrap approach (demanding consistency conditions to scattering amplitudes) has shown to be quite powerful to tightly constrain gauge theories at large Nc. We extend previous analysis to scattering amplitudes involving pions and external gauge bosons. These amplitudes allow us to access the chiral anomaly and connect low-energy physical quantities to UV properties of the theory. In particular, we are able to obtain an analytic bound on the chiral anomaly coefficient as a function of the pion dipole polarizabilities. This bound can be useful for holographic models whose dual UV completions are not known, and provide a consistency condition to lattice simulations. [ABSTRACT FROM AUTHOR]

The flavour puzzle is one of the greatest mysteries in particle physics. A 'flavour deconstruction' of the electroweak gauge symmetry, by promoting at least part of it to the product of a third family factor (under which the Higgs is charged) times a light family factor, allows one to address the flavour puzzle at a low scale due to accidentally realised U(2)5 flavour symmetries. The unavoidable consequence is new heavy gauge bosons with direct couplings to the Higgs, threatening the stability of the electroweak scale. In this work, we propose a UV complete model of flavour based on deconstructing only hypercharge. We find that the model satisfies finite naturalness criteria, benefiting from the smallness of the hypercharge gauge coupling in controlling radiative Higgs mass corrections and passing phenomenological bounds. Our setup allows one to begin explaining flavour at the TeV scale, while dynamics solving the large hierarchy problem can lie at a higher scale up to around 10 TeV — without worsening the unavoidable little hierarchy problem. The low-energy phenomenology of the model is dominated by a single Z′ gauge boson with chiral and flavour non-universal couplings, with mass as light as a few TeV thanks to the U(2)5 symmetry. The natural parameter space of the model will be probed by the HL-LHC and unavoidably leads to large positive shifts in the W-boson mass, as well as an enhancement in B (Bs,d → μ+μ−). Finally, we show that a future electroweak precision machine such as FCC-ee easily has the reach to fully exclude the model. [ABSTRACT FROM AUTHOR]

The T2K experiment is one of the most powerful long-baseline experiments to investigate neutrino oscillations. The off-axis near detector called ND280 is installed 280 m downstream from the neutrino production target to measure the neutrino energy spectrum. In this paper, we study the capability of the ND280 detector to search for the dark photon produced through the meson rare decay and proton bremsstrahlung processes at the proton beam dump. We find that the ten-year operation of T2K with the ND280 detector excludes the unexplored parameter region for the dark photon mass and kinetic mixing. We also show that a broader parameter region can be searched by the ND280 in the future T2K operation for dark photon as well as U(1)B−L gauge boson. [ABSTRACT FROM AUTHOR]

We study axion-like particle contributions to the Higgs boson decays. The particle is assumed to couple with the standard model electroweak gauge bosons. Although direct productions of axion-like particles have often been discussed, we investigate indirect contributions to the Higgs boson decays into fermions, photons, W, and Z bosons at the one-loop level. It is found that the corrections to the fermions are suppressed, whereas precise measurements of the di-photon channel of the Higgs boson decay can provide a significant probe of the model especially when the axion-like particle is heavy and its coupling to di-photon is suppressed. [ABSTRACT FROM AUTHOR]

In this work, we obtain the current limits on the pair production of vectorlike leptons decaying to a Standard Model gauge boson and a lepton in the second generation using the Run-2 data at the LHC. Since there is no dedicated search out of Run-2 data, we recast the ATLAS analyses searching for the type-III seesaw heavy leptons in the multi-lepton channels. There is no limit for the SU(2)L singlet vectorlike lepton beyond about 100 GeV, while the limit is about 780 GeV for the doublet one. Thus, dedicated searches for the vectorlike leptons are necessary, especially for the singlet one. We also study the general cases of the vectorlike lepton decays and future sensitivities at the HL-LHC. [ABSTRACT FROM AUTHOR]

The B-L symmetric SUSY model (B-LSSM) introduces a new Z ′ gauge boson and two singlet scalars, which indicates there are more neutralinos in the B-LSSM comparing with the minimal SUSY extension of standard model (MSSM). These new neutralinos provide more dark matter (DM) candidates in the B-LSSM, we find that the super partner of the new scalar singlet can serve as the lightest supersymmetric particle (LSP) and be considered as a DM candidate. The properties of this new DM candidate are analyzed in this work. Taking into account the experimental constraints on Higgs boson mass, B meson rare decays and muon anomalous magnetic dipole moment, the numerical results are obtained and presented. The properties of new DM candidate in the B-LSSM satisfy the observed relic density Ω h 2 and comply with the latest upper bounds on σ SI χ 1 0 - n , and its mass is expected to greater than 80 GeV approximately. [ABSTRACT FROM AUTHOR]

The bootstrap approach (demanding consistency conditions to scattering amplitudes) has shown to be quite powerful to tightly constrain gauge theories at large Nc. We extend previous analysis to scattering amplitudes involving pions and external gauge bosons. These amplitudes allow us to access the chiral anomaly and connect low-energy physical quantities to UV properties of the theory. In particular, we are able to obtain an analytic bound on the chiral anomaly coefficient as a function of the pion dipole polarizabilities. This bound can be useful for holographic models whose dual UV completions are not known, and provide a consistency condition to lattice simulations. [ABSTRACT FROM AUTHOR]

We investigate a local SU(3)F flavour symmetry for its viability in generating the masses for the quarks and charged leptons of the first two families through radiative corrections. Only the third-generation fermions get tree-level masses due to specific choice of the field content and their gauge charges. Unprotected by symmetry, the remaining fermions acquire non-vanishing masses through the quantum corrections induced by the gauge bosons of broken SU(3)F. We show that inter-generational hierarchy between the masses of the first two families arises if the flavour symmetry is broken with an intermediate SU(2) leading to a specific ordering in the masses of the gauge bosons. Based on this scheme, we construct an explicit and predictive model and show its viability in reproducing the realistic charged fermion masses and quark mixing parameters in terms of not-so-hierarchical fundamental couplings. The model leads to the strange quark mass, ms ≈ 16 MeV at MZ, which is ~2.4σ away from its current central value. Large flavour violations are a generic prediction of the scheme which pushes the masses of the new gauge bosons to 103 TeV or higher. [ABSTRACT FROM AUTHOR]

Weyl conformal geometry is a gauge theory of scale invariance that naturally brings together the Standard Model (SM) and Einstein gravity. The SM embedding in this geometry is possible without new degrees of freedom beyond SM and Weyl geometry, while Einstein gravity is generated by the broken phase of this symmetry. This follows a Stueckelberg breaking mechanism in which the Weyl gauge boson becomes massive and decouples, as discussed in the past [1–3]. However, Weyl anomaly could break explicitly this gauge symmetry, hence we study it in Weyl geometry. We first note that in Weyl geometry metricity can be restored with respect to a new differential operator ( ∇ ̂ ) that also enforces simultaneously a Weyl-covariant formulation. This leads to a metric-like Weyl gauge invariant formalism that enables one to do quantum calculations directly in Weyl geometry, rather than use a Riemannian (metric) geometry picture. The result is the Weyl-covariance in d dimensions of all geometric operators ( R ̂ , etc) and of their derivatives ( ∇ ̂ μ R ̂ , etc), including the Euler-Gauss-Bonnet term. A natural (geometric) Weyl-invariant dimensional regularisation of quantum corrections exists and Weyl gauge symmetry is then maintained and manifest at the quantum level. This is related to a non-trivial current of this symmetry, the divergence of which cancels the trace of the energy-momentum tensor. The "usual" Weyl anomaly and Riemannian geometry are recovered in the (spontaneously) broken phase. The relation to holographic Weyl anomaly is discussed. [ABSTRACT FROM AUTHOR]

In models with a U(1) gauge extension beyond the Standard Model, one can derive sum rules for the couplings of the theory that are a consequence of tree-level unitarity. In this paper, we provide a comprehensive list of coupling sum rules for a general SU 2 L × U 1 Y × U 1 Y ′ gauge theory coupled to an arbitrary set of fermion and scalar multiplets. These results are of particular interest for models of dark matter that employ an extended gauge sector mediated by a new (dark) Z′ gauge boson. For the case of a minimal extension of the Standard Model with a U 1 Y ′ gauge boson, we clarify the definitions of the weak mixing angle and the electroweak ρ parameter. We demonstrate the utility of a generalized ρ parameter (denoted by ρ′) whose definition naturally follows from the unitarity sum rules developed in this paper. [ABSTRACT FROM AUTHOR]

'Internal spacetime' is a modification of general relativity that was recently introduced as an approximate spacetime geometric model of quantum nonlocality. In an internal spacetime, time is stationary along the worldlines of fundamental (dust) particles. Consequently, the dimensions of tangent spaces at different points of spacetime vary, and spin wavefunction collapse is modeled by the projection from one tangent space to another. In this paper, we develop spinors on an internal spacetime, and construct a new Dirac-like Lagrangian ℒ = ψ ̄ (i ∂ / − ω ̂) ψ whose equations of motion describe their couplings and interactions. Furthermore, we show that hidden within ℒ is the entire standard model: ℒ contains precisely three generations of quarks and leptons, the electroweak gauge bosons, the Higgs boson, and one new massive spin- 2 boson; gluons are considered in a companion paper. Specifically, we are able to derive the correct spin, electric charge, and color charge of each standard model particle, as well as predict the existence of a new boson. [ABSTRACT FROM AUTHOR]