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]

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]

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]

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]

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]

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]

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]

We discuss the discovery potential of a promising signals, 3 × μ + μ - at a μ + μ - collider and μ + μ + μ + μ + μ - μ - at a μ + μ + collider, that are obtained via production of Z ′ and a new scalar boson ϕ in a spontaneously broken local U (1) L μ - L τ model. We consider the Z ′ associated production from the process μ + μ - → ϕ Z ′ in addition to a muonphilic Z ′ fusion process μ + μ ± → ϕ μ + μ ± . The scalar boson is associated with U (1) L μ - L τ symmetry breaking and dominantly decays into Z ′ Z ′ mode. We carry out numerical simulation analysis for signal and background processes to estimate a discovery significance for different benchmark points. It is shown that our signal can be observed with integrated luminosity less than O (100) fb - 1 for both μ + μ - and μ + μ + colliders with more than 5- σ significance. [ABSTRACT FROM AUTHOR]

Quantum entanglement of weak interaction gauge bosons produced at colliders can be explored by computing the corresponding polarization density matrix. To this end, we consider the Higgs boson decays H → W W ∗ and H → Z Z ∗ , in which W ∗ and Z ∗ are off-shell states, and the WW, WZ and ZZ di-boson production in proton collisions. The polarization density matrix of the di-boson state is determined by the amplitude of the production process and can be experimentally reconstructed from the angular distribution of the momenta of the final states into which the gauge bosons decay. We show that a suitable instance of the Bell inequality is violated in H → Z Z ∗ to a degree that can be tested at the LHC with future data. The same Bell inequality is violated in the production of WW and ZZ boson pairs for invariant masses above 900 GeV and scattering angles close to π / 2 in the center of mass frame. LHC data in this case are not sufficient to establish the violation of the Bell inequality. We also analyze the prospects for detecting Bell inequality violations in di-boson final states at future e + e - and muon colliders. A further observable that provides a lower bound on the amount of polarization entanglement in the di-boson system is computed for each of the examined processes. The analytic expressions for the polarization density matrices are presented in full in an Appendix. We also provide the unitary matrices required in the optimization procedure necessary in testing the Bell inequalities. [ABSTRACT FROM AUTHOR]

The existence of dark matter is explained by a new, massive, neutral, non-symmetric, rank-2 tensor gauge boson ( Z μ ν -boson). The Z μ ν -boson can be predicted by the tensor gauge boson extension of the Electro Weak (EW) theory, proposed by Savvidy (Phys Lett B 625:341, 2005). The non-symmetric rank-2 tensor Z μ ν can be decomposed into a symmetric ( Z (μ ν) ) and anti-symmetric ( Z [ μ ν ] ) part. Based on the non-Lagrangian formulation for the free sector of the R 2 -theory proposed recently by Criado et al. (Phys Rev D 102:125031, arXiv:2010.02224, 2020), our massive anti-symmetric tensor field Z [ μ ν ] corresponds to the massive symmetric spinor field Z α β γ δ in the (2,0) irrep. For the massive Z α β γ δ with the Z 2 -symmetric Higgs portal couplings to a Standard Model (SM) particle, we compute the self-annihilation cross-section of the Z α β γ δ dark matter and calculate its relic abundance. We also study the SM-SM particle scattering due to the exchange of the massive- Z (μ ν) symmetric field at a high energy scale. This proposition may have far reaching applications in astrophysics and cosmology. [ABSTRACT FROM AUTHOR]

We investigate the effects of the transitional magnetic dipole type interactions of the active-to-heavy-neutrino associated with a new neutral gauge boson Z ′ on neutrino-nucleon scattering at the ForwArd Search ExpeRiment- ν (FASER ν ). We consider the neutral-current neutrino-nucleon scattering ( ν A → N A ′ , where A ′ denotes the disintegrated nuclei) as the production mechanism of the heavy neutrino N at FASER ν and estimate the sensitivity reach on the magnetic-type dipole coupling ω ν α for a range of heavy neutrino mass ( 1 GeV < M N < 70 GeV ). In this study, we consider three benchmark models, in which the heavy neutrino is coupled to L e , L μ or L τ doublet, respectively. [ABSTRACT FROM AUTHOR]

We propose an anomaly free gauged U(1) extension of the SM where three right handed heavy neutrinos, being charged under the general U(1) gauge group, are introduced to explain the origin of the tiny neutrino mass through the seesaw mechanism after the general U(1) symmetry is broken. Due to the breaking of the general U(1) symmetry a neutral beyond the standard model gauge boson Z ′ acquires mass. There are two Higgs doublets in this model where one interacts with the SM fermions and the other one interacts with the right handed heavy neutrinos and charged leptons. The charged multiplet of the second Higgs can completely decay into the heavy neutrinos and charged lepton in the neutrinophilic limit of the model parameters. The charged Higgs pair production can be influenced due to presence of the Z ′ boson at the High Luminosity LHC (HL-LHC) in addition to the neutral SM gauge bosons. The pair produced charged Higgs bosons decay into SM charged leptons and heavy neutrinos. Following the leading decay modes of the heavy neutrinos into charged leptons and W boson we study the 5 and 6 lepton final states after the leptonic and hadronic decay of the W bosons considering solely muons and electrons in the final state. Combining the electron and muon final states we estimate the significance of the 5 and 6 charged lepton processes in the m H ± - m N plane for different benchmark points of m Z ′ . It is found that the 5 (6) charged lepton processes could be probed at the High Luminosity LHC (HL-LHC) with at least 5 (3) σ significance and there are parameter regions where the significance could be larger. [ABSTRACT FROM AUTHOR]

With the grand desert hypothesis, we have proposed to probe the supersymmetric Grand Unified Theories (GUTs) at the future proton–proton (pp) colliders and Hyper-Kamiokande experiment previously. In this paper, we study the supersymmetric GUTs with gravity mediated supersymmetry breaking in details. First, considering the dimension-six proton decay via heavy gauge boson exchange, we point out that we can probe the supersymmetric GUTs with GUT scale M GUT up to 1.778 × 10 16 GeV at the Hyper-Kamiokande experiment. Second, for the supersymmetric GUTs with M GUT ≥ 1.0 × 10 16 GeV and M GUT ≥ 1.2 × 10 16 GeV, we show that the upper bounds on the universal gaugino mass are 7.2 TeV and 3.5 TeV, respectively, and thus the corresponding upper bounds on gluino mass are 15 TeV and 8 TeV, respectively. Also, we shall study the masses for charginos, neutralinos, squarks, sleptons, and Higgs particles in details. In particular, the supersymmetric GUTs with M GUT ≤ 1.2 × 10 16 GeV can be probed at the Hyper-Kamiokande experiment, and the supersymmetric GUTs with M GUT ≥ 1.2 × 10 16 GeV can be probed at the future 100 TeV pp collider experiments such as the FCC hh and SppC via gluino searches. Thus, the supersymmetric GUTs with gravity mediation can be probed by the FCC hh , SppC, and Hyper-Kamiokande experiments. In our previous study, we have shown that the supersymmetric GUTs with anomaly and gauge mediated supersymmetry breakings are well within the reaches of these experiments. Therefore, our proposal provides the concrete scientific goal for the FCC hh , SppC, and Hyper-Kamiokande experiments: probing the supersymmetric GUTs. [ABSTRACT FROM AUTHOR]

The pair annihilation of neutrinos (ν ν ¯ → e + e -) can energize violent stellar explosions such as gamma ray bursts (GRBs). The energy in this neutrino heating mechanism can be further enhanced by modifying the background spacetime over that of Newtonian spacetime. However, one cannot attain the maximum GRB energy (∼ 10 52 erg) in either the Newtonian background or Schwarzschild and Hartle–Thorne background. On the other hand, using modified gravity theories or the Quintessence field as background geometries, the maximum GRB energy can be reached. In this paper, we consider extending the standard model by an extra U (1) B - L gauge group and augmenting the energy deposition by neutrino pair annihilation process including contributions mediated by the Z ′ gauge boson belonging to this model. From the observed energy of GRB, we obtain constraints on U (1) B - L gauge coupling in different background spacetimes. We find that the bounds on gauge coupling in modified gravity theories and quintessence background are stronger than those coming from the neutrino-electron scattering experiments in the limit of small gauge boson masses. Future GRB observations with better accuracy can further strengthen these bounds. [ABSTRACT FROM AUTHOR]

Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum statistics we do a model-independent study of effects of possible non-standard couplings of (Dirac and Majorana) neutrinos. The study is sensitive to the different quantum statistical properties of the Dirac and Majorana neutrinos which, contrary to neutrino-mediated processes of lepton number violation, could lead to observable effects not suppressed by the small ratios of neutrino and heavier particle masses. For processes with a neutrino-antineutrino pair of the same flavor in the final state, we formulate the "Dirac Majorana confusion theorem (DMCT)" showing why it is normally very difficult to observe the different behaviour of both kinds of neutrinos in experiments if they have only the standard model (SM)-like left-handed vector couplings to gauge bosons. We discuss deviations from the confusion theorem in the presence of non-standard neutrino interactions, allowing to discover or constrain such novel couplings. We illustrate the general results with two chosen examples of neutral current processes, Z → ν ν ¯ and P i → P f ν ν ¯ (with P i , f denoting pseudoscalar mesons, such as B , K , π ). Our analysis shows that using 3-body decays the presence of non-standard interactions can not only be constrained but one can also distinguish between Dirac and Majorana neutrino possibilities. [ABSTRACT FROM AUTHOR]

We discuss the sensitivity of theoretical predictions of observables used in searches for new physics to parton distributions (PDFs) at large momentum fraction x. Specifically, we consider the neutral-current Drell–Yan production of gauge bosons with invariant masses in the TeV range, for which the forward–backward asymmetry of charged leptons from the decay of the gauge boson in its rest frame is a traditional probe of new physics. We show that the qualitative behaviour of the asymmetry depends strongly on the assumptions made in determining the underlying PDFs. We discuss and compare the large-x behaviour of various different PDF sets, and find that they differ significantly. Consequently, the shape of the asymmetry observed at lower dilepton invariant masses, where all PDF sets are in reasonable agreement because of the presence of experimental constraints, is not necessarily reproduced at large masses where the PDFs are mostly unconstrained by data. It follows that the shape of the asymmetry at high masses may depend on assumptions made in the PDF parametrization, and thus deviations from the traditionally expected behaviour cannot be taken as a reliable indication of new physics. We demonstrate that forward–backward asymmetry measurements could help in constraining PDFs at large x and discuss the accuracy that would be required to disentangle the effects of new physics from uncertainties in the PDFs in this region. [ABSTRACT FROM AUTHOR]

We study the CDF W-mass, muon g - 2 , and dark matter observables in a local U (1) L μ - L τ model in which the new particles include three vector-like leptons ( E 1 , E 2 , N ), a new gauge boson Z ′ , a scalar S (breaking U (1) L μ - L τ ), a scalar dark matter X I and its partner X R . We find that the CDF W-mass disfavors m E 1 = m E 2 = m N or s L = s R = 0 where s L (R) is mixing parameter of left (right)-handed fields of vector-like leptons. A large mass splitting between E 1 and E 2 is favored when the differences between s L and s R becomes small. The muon g - 2 anomaly can be simultaneously explained for appropriate difference between m E 1 (s L) and m E 2 (s R) , and some regions are excluded by the diphoton signal data of the 125 GeV Higgs. Combined with the CDF W-mass, muon g - 2 anomaly and other relevant constraints, the correct dark matter relic density is mainly obtained in two different scenarios: (i) X I X I → Z ′ Z ′ , S S for m Z ′ (m S) < m X I and (ii) the co-annihilation processes for m i n (m E 1 , m E 2 , m N , m X R) close to m X I . Finally, we use the direct searches for 2 ℓ + E T miss event at the LHC to constrain the model, and show the allowed mass ranges of the vector-like leptons and dark matter. [ABSTRACT FROM AUTHOR]

There are two sources that help to explain the R K , R K ∗ anomalies in the MF331 model. The first is non-LFUV couplings of the new neutral gauge boson Z ′ with leptons, g Z ′ (e) ≠ g Z ′ (μ , τ) , which causes the R K , R K ∗ anomalies via Z ′ -penguin diagrams involving newly charged gauge bosons X μ ± , and exotic U-quarks. The second is the contribution from the box diagram only for the first generation of leptons. We show that the penguin diagrams can not explain R K , R K ∗ anomalies, and that the box diagram is required. The experimental constraints for R K and R K ∗ result in new particle mass degeneracy. The contributions of NP to the branching ratios Br (B s → μ + μ -) , Br (b → s γ) predict results that agree with the experimental limits in the allowed region of the NP scale. [ABSTRACT FROM AUTHOR]

We consider a U (1) B - L model with a Z ′ portal Dirac fermion dark matter (DM) χ of low mass which couples very weakly to the B - L gauge boson Z ′ . An arbitrary B - L charge Q ≠ ± 1 , ± 3 of the DM χ ensures its stability. Motivated by the sensitivity reach of forthcoming "Lifetime Frontier" experiments, we focus on the Z ′ mass, m Z ′ , in the sub-GeV to few GeV range. To evaluate the DM relic abundance, we examine both the freeze-out and freeze-in DM scenarios. For the freeze-out scenario, we show that the observed DM abundance is reproduced near the Z ′ resonance, m χ ≃ m Z ′ / 2 , where m χ is the DM mass. For the freeze-in scenario, we focus on m χ ≪ m Z ′ . We show that for a fixed value of m Z ′ , g BL values roughly scale as 1/Q to reproduce the observed DM abundance. For various Q values in the range between 10 - 6 and 10 2 , we show that the gauge coupling values g BL needed to reproduce the observed DM abundance lie in the search reach of future planned and/or proposed experiments such as FASER, Belle-II, LDMX, and SHiP. In the freeze-in case, the Q values to realize observable g BL values are found to be much smaller than that in the freeze-out case. [ABSTRACT FROM AUTHOR]

We study the low energy implications of a trinification model based on the gauge symmetry G = S U (3) c × S U (3) L × S U (3) R , without imposing gauge coupling unification. A minimal model requires two Higgs multiplets that reside in the bi-fundamental representation of G, and this is shown to be adequate for accommodating the Standard Model (SM) fermion masses and generate, via loop corrections and seesaw mechanism, suitable masses for the heavy neutral leptons as well as the observed SM neutrinos. We estimate a lower bound of around 15 TeV for the masses of the new down- type quarks that are required by the S U (3) L × S U (3) R symmetry. We examine the resonant production at the LHC of the new gauge bosons, which leads to a lower bound of 16 TeV for the symmetry breaking scale of G. We also show how the muon g - 2 anomaly can be resolved in the presence of these new gauge bosons and the heavy charged leptons present in the model. Finally, the model predicts the presence of a topologically stable monopole carrying three quanta (6 π / e) of Dirac magnetic charge and mass ≳ 160 TeV. If new matter fields lying in the fundamental representations of G are included, the model predicts the presence of exotic leptons, mesons and baryons carrying fractional electric charges such as ± e / 3 and ± 2 e / 3 , fully compatible with the Dirac quantization condition. [ABSTRACT FROM AUTHOR]

As shown in Allanach et al. (Global fits of third family hypercharge models to neutral current B-anomalies and electroweak precision observables. arXiv:2103.12056), the Third Family Hypercharge ( Y 3 ) Model changes the Standard Model prediction for M W whilst simultaneously explaining anomalies in b → s ℓ ℓ transitions via a heavy Z ′ gauge boson which is spawned by a spontaneously broken gauged U (1) Y 3 symmetry. The 2022 CDF II measurement of M W , which is far from the Standard Model prediction in the statistical sense, somewhat disfavours the Y 3 model. Here, we generalise the gauge charge assignments to the anomaly-free combination s Y 3 + t (B 3 - L 3) and show that incorporating the 2022 CDF II measurement of M W selects a viable domain of integers s and t. For example, s = 1 , t = - 3 yields a p value of.08 in a two-parameter global fit to 277 electroweak and flavour changing b data, much improving a SM p value of 1 × 10 - 6 . [ABSTRACT FROM AUTHOR]

It has been recently shown that the discrepancy between the theoretical and experimental values of the anomalous magnetic moment of the muon can be fully accommodated by considering the contribution of few Kaluza–Klein (KK) states of the gauged lepton number with masses lighter than the LEP energy, consistently with present experimental limits. In this article, we construct the minimal embedding of the Standard Model (SM) into D-brane configurations with a gauged lepton number. In order to give rise to such KK modes, the lepton number gauge boson must live on an abelian U (1) L brane extended along at least one "large" extra dimension in the bulk, with a compactification scale M L ∼ O (10 - 10 2 GeV) for a string scale M s ≳ 10 TeV . As a consequence, U (1) L cannot participate to the hypercharge linear combination. We show that the minimal realisation of this framework contains five stacks of branes: the SM color U (3) c , weak U (2) w and abelian U(1) stacks extended effectively only in four dimensions, the bulk U (1) L , as well as a fifth U (1) ′ brane. With these five abelian factors, one finds besides the hypercharge a second anomaly-free linear combination which does not couple to the SM spectrum, both in the non-supersymmetric case as well as in the minimal supersymmetric extension of the model. It is also shown how the right-handed neutrino can be implemented in the spectrum, and how fermions arising from the two non-SM branes and coupled to the SM through the U (1) L KK modes can provide Dark Matter candidates. Finally, the possibility of breaking Lepton Flavour Universality is studied by replacing U (1) L with a brane gauging only the muonic lepton number, avoiding most experimental constraints and enlarging the parameter space for explaining the discrepancy on the muon magnetic moment. [ABSTRACT FROM AUTHOR]

In the 5-dimensional braneworld cosmology, the Friedmann equation of our 4-dimensional universe on a brane is modified at high temperatures while the standard Big Bang cosmology is reproduced at low temperatures. Based on two well-known scenarios, the Randall–Sundrum and Gauss–Bonnet braneworld cosmologies, we investigate the braneworld cosmological effect on the relic density of a non-thermal dark matter particle whose interactions with the Standard Model particles are so weak that its relic density is determined by the freeze-in mechanism. For dark matter production processes in the early universe, we assume a simple scenario with a light vector-boson mediator for the dark matter particle to communicate with the Standard Model particles. We find that the braneworld cosmological effect can dramatically alters the resultant dark matter relic density from the one in the standard Big Bang cosmology. As an application, we consider a right-handed neutrino dark matter in the minimal B - L extended Standard Model with a light B - L gauge boson ( Z ′ ) as a mediator. We find an impact of the braneworld cosmological effect on the search for the long-lived Z ′ boson at the planned/proposed Lifetime Frontier experiments. [ABSTRACT FROM AUTHOR]

Experimental hints for lepton-flavor universality violation in the muon's magnetic moment as well as neutral- and charged-current B-meson decays require Standard-Model extensions by particles such as leptoquarks that generically lead to unacceptably fast rates of charged lepton flavor violation and proton decay. We propose a model based on a gauged U (1) L μ - L τ that eliminates all these unwanted decays by symmetry rather than finetuning and efficiently explains (g - 2) μ , R K (∗) , R D (∗) , and neutrino masses. The U (1) L μ - L τ furthermore acts as a stabilizing symmetry for dark matter and the light Z ′ gauge boson mediates velocity-dependent dark-matter self-interactions that resolve the small-scale structure problems. Lastly, even the Hubble tension can be ameliorated via the light Z ′ contribution to the relativistic degrees of freedom. [ABSTRACT FROM AUTHOR]

We investigate herein the phenomenology of μ → e γ decay in a scenario of the class of extended models with non-sterile right-handed (RH) neutrinos at electroweak (EW) scale proposed by P. Q. Hung. The field content of the standard model (SM) is increased by introducing for each SM fermion a corresponding mirror partner with the same quantum numbers along with opposite chirality. Light neutrino masses are generated via the type I seesaw mechanism, and it is also proved to be relevant to low energy within the EW scale of RH neutrino masses. We introduce the model and derive the branching ratio of the μ → e γ decay at one-loop approximation with the participation of W gauge boson and neutral and singly charged Higgs scalars. We then set constraints on relevant parameters and predict the sensitivity of the decay channel under the present and future experiments. [ABSTRACT FROM AUTHOR]

General one-loop contributions to the decay processes H → f f ¯ γ and its applications are presented in this paper. We consider all possible contributions of the additional heavy vector gauge bosons, heavy fermions, and charged (also neutral) scalar particles propagating in Feynman loop diagrams. Therefore, analytic results are valid in a wide class of models beyond the Standard Model. Analytic formulas for the form factors are expressed in terms of Passarino-Veltman functions in the standard notations of LoopTools. Hence, the decay rates can be evaluated numerically by using this package. The computations are then applied to the cases of the Standard Model, U (1) B - L extension of the Standard Model as well as Two Higgs Doublet Model. Phenomenological results for all the above models are studied. We observe that the effects of new physics are sizable contributions and these can be probed at future colliders. [ABSTRACT FROM AUTHOR]

The Third Family Hypercharge Model predicts a Z ′ gauge boson with flavour dependent couplings which has been used to explain anomalies in meson decay processes which involve the b → s μ + μ - transition. The model predicts that a TeV-scale Z ′ should decay to particle-antiparticle pairs of muons, taus, top quarks and bottom quarks with appreciable branching ratios. We reinterpret various ATLAS and CMS search limits for Z ′ production followed by such decays at the LHC over a parameter space of the model that results from a successful combined fit to the b → s l + l - data and precision electroweak observables. Current exclusions in parameter space and expected sensitivities of the various different channels in the high-luminosity run are compared. We find that the high-luminosity run of the LHC will significantly increase the sensitivity to the model beyond the existing empirical limits, which we find to be surprisingly weak. [ABSTRACT FROM AUTHOR]

We study scenarios where Dark Matter is a weakly interacting particle (WIMP) embedded in an ElectroWeak multiplet. In particular, we consider real SU(2) representations with zero hypercharge, that automatically avoid direct detection constraints from tree-level Z-exchange. We compute for the first time all the calculable thermal masses for scalar and fermionic WIMPs, including Sommerfeld enhancement and bound states formation at leading order in gauge boson exchange and emission. WIMP masses of few hundred TeV are shown to be compatible both with s-wave unitarity of the annihilation cross-section, and perturbativity. We also provide theory uncertainties on the masses for all multiplets, which are shown to be significant for large SU(2) multiplets. We then outline a strategy to probe these scenarios at future experiments. Electroweak 3-plets and 5-plets have masses up to about 16 TeV and can efficiently be probed at a high energy muon collider. We study various experimental signatures, such as single and double gauge boson emission with missing energy, and disappearing tracks, and determine the collider energy and luminosity required to probe the thermal Dark Matter masses. Larger multiplets are out of reach of any realistic future collider, but can be tested in future γ -ray telescopes and possibly in large-exposure liquid Xenon experiments. [ABSTRACT FROM AUTHOR]

We analyse the Higgs sector of an S 3 model with three Higgs doublets and no CP violation. After electroweak breaking there are nine physical Higgs bosons, one of which corresponds to the Standard Model one. We study the scalar and gauge sectors of this model, taking into account the conditions set by the minimisation and stability of the potential. We calculate the masses, trilinear and quartic Higgs-Higgs, and Higgs-gauge couplings. We consider two possible alignment scenarios, where only one of the three neutral scalars has couplings to the gauge bosons and corresponds to the SM Higgs, and whose trilinear and quartic couplings reduce exactly to the SM ones. We also obtain numerically the allowed parameter space for the scalar masses in each of the alignment scenarios. We use the calculated trilinear and quartic couplings to find the analytical structure of the one-loop neutral scalar mass matrix, without fermionic contributions. We show that it is possible to have a compact mass spectrum where the contribution to the oblique parameters might be small. We explore some scenarios for the loop contributions to the neutral scalar masses. [ABSTRACT FROM AUTHOR]

In the present work, we have extended the standard model by an abelian U (1) X gauge group and additional particles. In particular, we have extended the particle content by three right handed neutrinos, two singlet scalars and two vectors like leptons. Charged assignments under different gauge groups are such that the model is gauge anomaly free and the anomaly contributions cancel among generations. Once the symmetry gets broken then three physical Higgses are produced, one axion like particle (ALP), which also acts as the keV scale FIMP dark matter is produced and the remaining component is absorbed by the extra gauge boson. Firstly, we have successfully generated neutrino mass by the type-I seesaw mechanism for normal hierarchy with the 3 σ bound on the oscillation parameters. The ALP in the present model can explain the Xenon-1T electron recoil signal at keV scale through its coupling with the electron. We have shown that ALP can be produced from the right handed neutrino decay through the freeze in mechanism. Electron and tauon get masses from dimensional-5 operators at the Planck scale and if we consider the vevs v 1 , 2 ≃ 10 12 GeV then we can obtain the correct value of the electron mass but not the tauon mass. The vector like leptons help in getting the correct value of the tauon mass through another higher dimensional operator which also has a role in DM production by the 2 → 2 process, giving the correct ballpark value of relic density for suitable reheat temperature of the Universe. We have shown that the ALP production by the higher dimensional operator can explain the electron, tauon mass and Xenon-1T signal simultaneously whereas the decay production can not explain all of them together. [ABSTRACT FROM AUTHOR]

The dark photon is a new gauge boson which arises from an extra U ′ (1) gauge symmetry. In this paper, a novel dark photon production mechanism based on MeV-scale γ – γ collider is considered: γ γ → γ A ′ . With the aid of PACKAGE-X, differential cross section of γ γ → γ A ′ is obtained, as a function of the kinetic mixing parameter ε and dark photon mass m A ′ . Taking the light-by-light scattering as background, the constraints on the dark photon parameter space for different time intervals in a MeV-scale γ – γ collider are also given. [ABSTRACT FROM AUTHOR]

The one-loop contributions to the trilinear neutral gauge boson couplings Z Z V ∗ ( V = γ , Z , Z ′ ), parametrized in terms of one CP-conserving f 5 V and one CP-violating f 4 V form factors, are calculated in models with CP-violating flavor changing neutral current couplings mediated by the Z gauge boson and an extra neutral gauge boson Z ′ . Analytical results are presented in terms of Passarino-Veltman scalar functions. Constraints on the vector and axial couplings of the Z gauge boson g VZ tu < 0.0096 and g VZ tc < 0.011 are obtained from the current experimental data on the t → Z q decays. It is found that in the case of the Z Z γ ∗ vertex the only non-vanishing form factor is f 5 γ , which can be of the order of 10 - 3 , whereas for the Z Z Z ∗ vertex both form factors f 5 Z and f 4 Z are non-vanishing and can be of the order of 10 - 6 and 10 - 5 , respectively. Our estimates for f 5 γ and f 5 Z are smaller than those predicted by the standard model, where f 4 Z is absent up to the one loop level. We also estimate the Z Z Z ′ ∗ form factors arising from both diagonal and non-diagonal Z ′ couplings within a few extension models. It is found that in the diagonal case f 5 Z ′ is the only non-vanishing form factor and its real and imaginary parts can be of the order of 10 - 1 – 10 - 2 and 10 - 2 – 10 - 3 , respectively, with the dominant contributions arising from the light quarks and leptons. In the non-diagonal case f 5 Z ′ can be of the order of 10 - 4 , whereas f 4 Z ′ can reach values as large as 10 - 7 – 10 - 8 , with the largest contributions arising from the Z ′ t q couplings. [ABSTRACT FROM AUTHOR]

We consider a model with gauged L μ - L τ symmetry in which the symmetry is spontaneously broken by a scalar field. The decay of the scalar boson into two new gauge bosons is studied as a direct consequence of the spontaneous symmetry breaking. Then, a possibility of searches for the gauge and scalar bosons through such a decay at the LHC experiment is discussed. We consider the case that the mass range of the gauge boson is O (10) GeV, which is motivated by anomalies reported by LHCb. We will show that the signal significance of the searches for the gauge boson and scalar boson reach to 3 and 5 for the scalar mixing 0.012 and 0.015, respectively. [ABSTRACT FROM AUTHOR]

The standard model leptons can be gauged in an anomaly free way by three possible gauge symmetries namely L e - L μ , L e - L τ , and L μ - L τ . Of these, L e - L μ and L e - L τ forces can mediate between the Sun and the planets and change the perihelion precession of planetary orbits. It is well known that a deviation from the 1 / r 2 Newtonian force can give rise to a perihelion advancement in the planetary orbit, for instance, as in the well known case of Einstein's gravity (GR) which was tested from the observation of the perihelion advancement of the Mercury. We consider the long range Yukawa potential which arises between the Sun and the planets if the mass of the gauge boson is M Z ′ ≤ O (10 - 19) eV . We derive the formula of perihelion advancement for Yukawa type fifth force due to the mediation of such U (1) L e - L μ , τ gauge bosons. The perihelion advancement for Yukawa potential is proportional to the square of the semi major axis of the orbit for small M Z ′ , unlike GR where it is largest for the nearest planet. For higher values of M Z ′ , an exponential suppression of the perihelion advancement occurs. We take the observational limits for all planets for which the perihelion advancement is measured and we obtain the upper bound on the gauge boson coupling g for all the planets. The Mars gives the stronger bound on g for the mass range ≤ 10 - 19 eV and we obtain the exclusion plot. This mass range of gauge boson can be a possible candidate of fuzzy dark matter whose effect can therefore be observed in the precession measurement of the planetary orbits. [ABSTRACT FROM AUTHOR]

In this paper, a study is carried out on the e - p → e - γ ∗ p → p W - γ ν e production to probe quartic W + W - γ γ couplings at the Large Hadron electron Collider (LHeC) with s = 1.30 , 1.98 TeV and at the Future Circular Collider-hadron electron (FCC-he) with s = 3.46 , 5.29 TeV . Production cross-sections are determined for both at leptonic and hadronic decay channels of the W-boson. With the data from future e - p colliders, it is possible to obtain sensitivity measures at 95 % C.L. on the anomalous f M , i / Λ 4 and f T , j / Λ 4 couplings which are competitive with the limits obtained by the LHC, as well as with others limits reported in the literature. The production mode e - p → e - γ ∗ p → p W - γ ν e in e - p collisions offers a window for study the quartic W + W - γ γ electroweak bosons couplings at the LHeC and the FCC-he, which provides a much cleaner collision environment than the LHC. [ABSTRACT FROM AUTHOR]

Cosmological evolution and particle creation in R 2 -modified gravity are considered for the case of the dominant decay of the scalaron into a pair of gauge bosons due to conformal anomaly. It is shown that in the process of thermalization superheavy dark matter with the coupling strength typical for the GUT SUSY can be created. Such dark matter would have the proper cosmological density if the particle mass is close to 10 12 GeV. [ABSTRACT FROM AUTHOR]

We study dark matter (DM) abundance in the framework of the extension of the Standard Model (SM) with an additional U (1) X gauge symmetry. One complex singlet is included to break the U (1) X gauge symmetry, meanwhile one of the doublets is considered inert to introduce a DM candidate. The stability of the DM candidate is analyzed with a continuous U (1) X gauge symmetry as well as discrete Z 2 symmetry. We find allowed regions for the free model parameters which are in agreement with the most up-to-date experimental results reported by CMS and ATLAS Collaborations, the upper limit on WIMP-nucleon cross section imposed by XENON1T Collaboration and the upper limit on the production cross-section of a Z ′ gauge boson times the branching ratio of the Z ′ boson decaying into ℓ - ℓ + . We also obtain allowed regions for the DM candidate mass from the relic density reported by the PLANCK Collaboration including light, intermediate and heavy masses; depending mainly on two parameters of the scalar potential, λ 2 x and λ 345 = λ 3 + λ 4 + 2 λ 5 . We find that trough p p → χ χ γ production, it may only be possible for a future hadron–hadron circular collider (FCC-hh) to be able to detect a DM candidate within the range of masses 10–60 GeV. [ABSTRACT FROM AUTHOR]

We present a fermionic dark matter model mediated by the hidden gauge boson. We assume the QED-like hidden sector which consists of a Dirac fermion and U(1) X gauge symmetry, and introduce an additional scalar electroweak doublet field with the U(1) X charge as a mediator. The hidden U(1) X symmetry is spontaneously broken by the electroweak symmetry breaking and there exists a massive extra neutral gauge boson in this model which is the mediator between the hidden and visible sectors. Due to the U(1) X charge, the additional scalar doublet does not couple to the Standard Model fermions, which leads to the Higgs sector of type I two Higgs doublet model. The new gauge boson couples to the Standard Model fermions with couplings proportional to those of the ordinary Z boson but very suppressed, thus we call it the dark Z boson. We study the phenomenology of the dark Z boson and the Higgs sector, and show the hidden fermion can be the dark matter candidate. [ABSTRACT FROM AUTHOR]

The full ATLAS Run 2 data set with time-integrated luminosity of 139 fb - 1 in the diboson channels in hadronic final states is used to probe a simple model with an extended gauge sector (EGM), proposed by Altarelli et al., and often taken as a convenient benchmark by experimentalists. This model accommodates new charged W ′ and neutral Z ′ vector bosons with modified trilinear Standard Model gauge couplings, decaying into electroweak gauge boson pairs WZ or WW, where W/Z decay hadronically. Exclusion limits at the 95% CL on the Z ′ and W ′ resonance production cross section times branching ratio to electroweak gauge boson pairs in the mass range of ∼ 1–5 TeV are here converted to constraints on W– W ′ and Z– Z ′ mixing parameters and masses for the EGM. We present exclusion regions on the parameter space of the W ′ and Z ′ by using the full Run 2 data set comprised of pp collisions at s = 13 TeV and recorded by the ATLAS detector at the CERN LHC. The obtained exclusion regions are significantly extended compared to those obtained from the previous analysis performed with Tevatron data as well as with LHC data collected at 7 and 8 TeV in Run 1 and are the most stringent bounds to date. [ABSTRACT FROM AUTHOR]

An anomaly observed recently in the 8 Be nuclear transition by the Atomki collaboration hints at a weakly-coupled, light new gauge boson with a mass of about 17 MeV. In this paper, we propose that this new gauge boson comes from a short-distance structure of the spacetime, rather than from an extension of the Standard Model through adding an extra U (1) gauge symmetry. The dominant contribution to the relevant matrix element of the 8 Be nuclear transition is given by the axial couplings. In order to account for the 8 Be anomaly and satisfy the current experimental constraints, the coupling constant of the new gauge boson should be about O (10 - 4 - 10 - 5) . Our theoretical model allows understanding the origin of the smallness of the coupling constant, which is still missing or being incompletely understood in the models at which the new gauge boson has the axial couplings. [ABSTRACT FROM AUTHOR]

After the recent high precision determinations of V us and V ud , the first row of the CKM matrix shows more than 4 σ deviation from unitarity. Two possible scenarios beyond the Standard Model can be investigated in order to fill the gap. If a 4th non-sequential quark b ′ (a vector-like weak isosinglet) participates in the mixing, with | V u b ′ | ∼ 0.04 , then its mass should be no more than 6 TeV or so. A different solution can come from the introduction of the gauge horizontal family symmetry S U (3) ℓ acting between the lepton families and spontaneously broken at the scale of about 6 TeV. Since the gauge bosons of this symmetry contribute to muon decay in interference with Standard Model, the Fermi constant is slightly smaller than the muon decay constant so that unitarity is recovered. Also the neutron lifetime problem, that is about 4 σ discrepancy between the neutron lifetimes measured in beam and trap experiments, is discussed in the light of the these determinations of the CKM matrix elements. [ABSTRACT FROM AUTHOR]

We present a first, consistent combination of measurements from top-quark and B physics to constrain top-quark properties within the Standard Model Effective Field Theory (SMEFT). We demonstrate the feasibility and benefits of this approach and detail the ingredients required for a proper combination of observables from different energy scales. Specifically, we employ measurements of the t t ¯ γ cross section together with measurements of the B ¯ → X s γ branching fraction to test the Standard Model and look for new physics contributions to the couplings of the top quark to the gauge bosons within SMEFT. We perform fits of three Wilson coefficients of dimension-six operators considering only the individual observables as well as their combination to demonstrate how the complementarity between top-quark and B physics observables allows to resolve ambiguities and significantly improves the constraints on the Wilson coefficients. No significant deviation from the Standard Model is found with present data. [ABSTRACT FROM AUTHOR]

We study the gauged U (1) L μ - L τ scotogenic model with emphasis on latest measurement of LHCb R K (∗) anomaly and AMS-02 positron excess. In this model, neutrino masses are induced at one-loop level with Z 2 -odd particles, i.e., right-handed neutrinos N ℓ (ℓ = e , μ , τ) and inert scalar doublet η inside the loop. Meanwhile, the gauged U (1) L μ - L τ symmetry is broken spontaneously by the scalar singlet S, resulting to the massive gauge boson Z ′ . Provided certain couplings to quarks induced by heavy vector-like quarks, the gauge boson Z ′ would contribute to the transition b → s μ + μ - , hence explain the R K (∗) anomaly. As for the Majorana fermion DM N, the gauge boson Z ′ and the singlet Higgs H 0 will generate various annihilation channels, among which the N N → Z ′ Z ′ and N N → Z ′ H 0 (→ Z ′ Z ′) channel could be used to interpret the AMS-02 positron excess. We give a comprehensive analysis on model parameter space with consider various current constraints. The combined analysis shows that the R K (∗) anomaly and AMS-02 positron excess can be explained simultaneously. [ABSTRACT FROM AUTHOR]

Considering the superior performances of the future e-p colliders, LHeC and FCC-eh, we discuss the feasibility of detecting the extra neutral scalar h 2 and the light gauge boson Z μ τ , which are predicted by the U (1) L μ - L τ model. Taking into account the experimental constraints on the relevant free parameters, we consider all possible production channels of h 2 and Z μ τ at e-p colliders and further investigate their observability through the optimal channels in the case of the beam polarization P (e -) = - 0.8 . We find that the signal significance above 5 σ of h 2 as well as Z μ τ detecting can be achieved via process and a 5 σ sensitivity of Z μ τ detecting can be gained via process at e-p colliders with appropriate parameter values and a designed integrated luminosity. However, the signals of h 2 decays into pair of SM particles are difficult to be detected. [ABSTRACT FROM AUTHOR]

In this paper, we generalize Coleman–Weinberg (CW) inflation in grand unified theories (GUTs) such as SU (5) and SO (10) by means of considering two complex singlet fields with conformal invariance. In this framework, inflation emerges from a spontaneously broken conformal symmetry. The GUT symmetry implies a potential with a CW form, as a consequence of radiative corrections. The conformal symmetry flattens the above VEV branch of the CW potential to a Starobinsky plateau. As a result, we obtain n s ∼ 1 - 2 N and r ∼ 12 N 2 for N ∼ 50–60 e-foldings. Furthermore, this framework allow us to estimate the proton lifetime as τ p ≲ 10 40 years, whose decay is mediated by the superheavy gauge bosons. Moreover, we implement a type I seesaw mechanism by weakly coupling the complex singlet, which carries two units of lepton number, to the three generations of singlet right handed neutrinos (RHNs). The spontaneous symmetry breaking of global lepton number amounts to the generation of neutrino masses. We also consider non-thermal leptogenesis in which the inflaton dominantly decays into heavy RHNs that sources the observed baryon asymmetry. We constrain the couplings of the inflaton field to the RHNs, which gives the reheating temperature as 10 6 GeV ≲ T R < 10 9 GeV. [ABSTRACT FROM AUTHOR]

In this work, we propose minimal realizations for generating Dirac neutrino masses in the context of a right-handed abelian gauge extension of the Standard Model. Utilizing only U (1) R symmetry, we address and analyze the possibilities of Dirac neutrino mass generation via (a) tree-level seesaw and (b) radiative correction at the one-loop level. One of the presented radiative models implements the attractive scotogenic model that links neutrino mass with Dark Matter (DM), where the stability of the DM is guaranteed from a residual discrete symmetry emerging from U (1) R . Since only the right-handed fermions carry non-zero charges under the U (1) R , this framework leads to sizable and distinctive Left–Right asymmetry as well as Forward–Backward asymmetry discriminating from U (1) B - L models and can be tested at the colliders. We analyze the current experimental bounds and present the discovery reach limits for the new heavy gauge boson Z ′ at the LHC and ILC. Furthermore, we also study the associated charged lepton flavor violating processes, dark matter phenomenology and cosmological constraints of these models. [ABSTRACT FROM AUTHOR]

Extensions of the standard model often come with additional, possibly electroweakly charged Higgs states, the prototypal example being the Two-Higgs-Doublet Model. While collider phenomenology does not exclude the possibility for some of these new scalar fields to be light, it is relatively natural to consider masses in the multi-TeV range, in which case the only remaining light Higgs boson automatically receives SM-like properties. The appearance of a hierarchy between the new-physics states and the electroweak scale then leads to sizable electroweak corrections, e. g. in the decays of the heavy Higgs bosons, which are dominated by effects of infrared type, namely Sudakov logarithms. Such radiative contributions obviously affect the two-body decays, but should also be paired with the radiation of electroweak gauge bosons (or lighter Higgs bosons) for a consistent picture at the one-loop order. Resummation of the leading terms is also relatively easy to achieve. We re-visit these questions in the specific case of the fermionic decays of heavy Higgs particles in the Next-to-Minimal Supersymmetric Standard Model, in particular pointing out the consequences of the three-body final states for the branching ratios of the heavy scalars. [ABSTRACT FROM AUTHOR]

In string compactifications, frequently the anomalous U(1) gauge symmetry appears which belongs to $$E_8 \times E_8'$$ of the heterotic string. This anomalous U(1) gauge boson obtains mass at the compactification scale ( $$\approx 10^{18\,}\,\text {GeV}$$ ) by absorbing one pseudoscalar (corresponding to the model-independent axion) from the second rank antisymmetric tensor field $$B_{MN}$$ . Below the compactification scale a global symmetry $$U(1)_{\mathrm{anom}}$$ results whose charge $$Q_\mathrm{anom}$$ is the original gauge U(1) charge. This is the most natural global symmetry, realizing the 'invisible' axion. This global symmetry $$U(1)_{\mathrm{anom}}$$ is suitable for a flavor symmetry. In the simplest compactification model with the flipped SU(5) grand unification, all the low energy parameters are calculated in terms of the vacuum expectation values of the standard model singlets. [ABSTRACT FROM AUTHOR]

We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models. It incorporates fermionic decays to a fermion and a scalar or a gauge boson as well as scalar decays into two fermions, two gauge bosons, two scalars or a scalar and a gauge boson. We present the relevant generic expressions for virtual and real corrections. Whereas wave-function corrections are determined from on-shell conditions, the parameters of the underlying model are by default renormalised in a $$\overline{\text {DR}}$$ (or $$\overline{\text {MS}}$$ ) scheme. However, the user can also define model-specific counter-terms. As an example we discuss the renormalisation of the electric charge in the Thomson limit for top-quark decays in the standard model. One-loop-induced decays are also supported. The framework additionally allows the addition of mass and mixing corrections induced at higher orders for the involved external states. We explain our procedure to cancel infrared divergences for such cases, which is achieved through an infrared counter-term taking into account corrected Goldstone boson vertices. We compare our results for sfermion, gluino and Higgs decays in the minimal supersymmetric standard model (MSSM) against the public codes SFOLD, FVSFOLD and HFOLD and explain observed differences. Radiatively induced gluino and neutralino decays are compared against the original implementation in SPheno in the MSSM. We exactly reproduce the results of the code CNNDecays for decays of neutralinos and charginos in R-parity violating models. The new version SARAH 4.11.0 by default includes the calculation of two-body decay widths at the full one-loop level. Current limitations for certain model classes are described. [ABSTRACT FROM AUTHOR]