Venus Keus - Academia.edu (original) (raw)

Papers by Venus Keus

Research paper thumbnail of CP -violating inflation and its cosmological imprints

Physical Review D

We study models with several SUð2Þ scalar doublets where the inert doublets have a nonminimal cou... more We study models with several SUð2Þ scalar doublets where the inert doublets have a nonminimal coupling to gravity and play the role of the inflaton. We allow for this coupling to be complex, thereby introducing CP violation-a necessary source of the baryon asymmetry-in the Higgs-inflaton couplings. We investigate the inflationary dynamics of the model and discuss how the CP violation of the model is imprinted on the particle asymmetries after inflation in the hot big bang universe.

Research paper thumbnail of Baryogenesis from a CP-Violating Inflation

Proceedings of The International Conference on Beyond Standard Model: From Theory To Experiment

Research paper thumbnail of Pseudo-Goldstone dark matter: gravitational waves and direct-detection blind spots

Journal of High Energy Physics

Pseudo-Goldstone dark matter is a thermal relic with momentum-suppressed direct-detection cross s... more Pseudo-Goldstone dark matter is a thermal relic with momentum-suppressed direct-detection cross section. We study the most general model of pseudo-Goldstone dark matter arising from the complex-singlet extension of the Standard Model. The new U(1) symmetry of the model is explicitly broken down to a CP-like symmetry stabilising dark matter. We study the interplay of direct-detection constraints with the strength of cosmic phase transitions and possible gravitational-wave signals. While large U(1)-breaking interactions can generate a large direct-detection cross section, there are blind spots where the cross section is suppressed. We find that sizeable cubic couplings can give rise to a first-order phase transition in the early universe. We show that there exist regions of the parameter space where the resulting gravitational-wave signal can be detected in future by the proposed Big Bang Observer detector.

Research paper thumbnail of Dark CP violation through the Z portal

Research paper thumbnail of Dark origins of matter-antimatter asymmetry

Proceedings of Corfu Summer Institute 2019 "School and Workshops on Elementary Particle Physics and Gravity" — PoS(CORFU2019)

Research paper thumbnail of Collider signatures of dark CP violation

Research paper thumbnail of Lepton collider indirect signatures of dark CP-violation

The European Physical Journal C

We study an extension of the Standard Model (SM) in which two copies of the SM Higgs doublet are ... more We study an extension of the Standard Model (SM) in which two copies of the SM Higgs doublet are added to the scalar sector. These extra doublets do not develop a vacuum expectation value, hence, they are inert. This essentially leads to a 3-Higgs Doublet Model (3HDM) with 2 inert and 1 active scalar doublets, which we denote as I(2+1)HDM. We allow for CP-violation in the inert sector, where the lightest inert state is protected from decaying to SM particles through the conservation of a Z 2 symmetry, so that it is a Dark Matter (DM) candidate. For this scenario, we identify a smoking gun signature of dark CP-violation in the form of production thresholds of pairs of inert neutral Higgs bosons at an e + e − collider.

Research paper thumbnail of CP violation and BSM Higgs bosons

Proceedings of Prospects for Charged Higgs Discovery at Colliders — PoS(CHARGED2016)

We study extensions of the Standard Model (SM) in which copies of the SM scalar SU(2) doublet are... more We study extensions of the Standard Model (SM) in which copies of the SM scalar SU(2) doublet are added to the Higgs sector. These scalar doublets either acquire a Vacuum Expectation Value (VEV) and hence are active or do not develop a VEV and are inert. We consider CP-violation (CPV) in both the active and inert sector. As an example of a model with CPV in the active sector, we present a Type-I 2-Higgs-Doublet Model (2HDM) with two active doublets and show Large Hadron Collider (LHC) signals of such a scenario. The amount of CPV in this case is very limited due to constraints coming from Electric Dipole Moment experiments. Moreover, 2HDMs with only active doublets do not provide a Dark Matter (DM) candidate. As a result, we turn to 3-Higgs-Doublet Models (3HDMs) where unbounded CPV and viable DM candidates could be introduced simultaneously in the inert sector. We investigate DM phenomenology of such models.

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

Journal of High Energy Physics

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

Research paper thumbnail of Cosmological constraints on light flavons

Journal of High Energy Physics

The Froggatt-Nielsen mechanism is a well-motivated framework for generating the fermion mass hier... more The Froggatt-Nielsen mechanism is a well-motivated framework for generating the fermion mass hierarchy. This mechanism introduces flavons, complex scalars which are singlet under the Standard Model gauge symmetry and charged under a new global family symmetry. We make use of a leptophilic flavon to produce the charged lepton Yukawa matrix. The real part of the flavon mixes with the Higgs boson and introduces lepton flavour violating interactions which are bounded by experiment. The imaginary part of the flavon, η, is a long-lived light particle, whose abundance is restricted by cosmological observations. For m η < 2m e where the decay of η to charged leptons is kinematically forbidden, we identify allowed regions of m η with respect to the vacuum expectation value of the flavon field where all experimental and cosmological constraints are satisfied.

Research paper thumbnail of Direct and indirect probes of Goldstone dark matter

Research paper thumbnail of Singlet scalar and 2HDM extensions of the Standard Model: CP-violation and constraints from (g − 2)μ and eEDM

Journal of High Energy Physics

We study popular scalar extensions of the Standard Model, namely the singlet extension, the 2-Hig... more We study popular scalar extensions of the Standard Model, namely the singlet extension, the 2-Higgs doublet model (2HDM) and its extension by a singlet scalar. We focus on the contributions of the added scalars to the anomalous magnetic moment of the muon, (g − 2) µ in the presence of CP-violation, and the electric dipole moment of the electron (eEDM) in these models. In the absence of CP-violation, CP-even and CP-odd scalars contribute with an opposite sign to the anomalous magnetic moment of the muon and as a result these models generally require very light scalars to explain the observed discrepancy in (g − 2) µ. We study the effect of CP-violation on the anomalous magnetic moment of the muon and its compatibility with the eEDM constraints. We show that given the current status of the global set of constraints applied on all values of cot β, in the CP-violating scalar extensions, there exist no viable parameter space in agreement with both a µ and eEDM bounds.

Research paper thumbnail of Dark Matter signals at the LHC from a 3HDM

Journal of High Energy Physics

We analyse new signals of Dark Matter (DM) at the Large Hadron Collider (LHC) in a 3-Higgs Double... more We analyse new signals of Dark Matter (DM) at the Large Hadron Collider (LHC) in a 3-Higgs Doublet Model (3HDM) where only one doublet acquires a Vacuum Expectation Value (VEV), preserving a parity Z 2. The other two doublets are inert and do not develop a VEV, leading to a dark scalar sector controlled by Z 2, with the lightest CP-even dark scalar H 1 being the DM candidate. This leads to the loop induced decay of the next-to-lightest scalar, H2toH1foverlinefleft(f=u,d,c,s,b,e,mu,tauright){H}_2\to {H}_1f\overline{f}\left(f=u,d,c,s,b,e,\mu, \tau \right)H2toH1foverlinefleft(f=u,d,c,s,b,e,mu,tauright) H 2 → H 1 f f ¯ f = u , d , c , s , b , e , μ , τ , mediated by both dark CP-odd and charged scalars. This is a smoking-gun signal of the 3HDM since it is not allowed in the 2HDM with one inert doublet and is expected to be important when H 2 and H 1 are close in mass. In practice, this signature can be observed in the cascade decay of the SM-like Higgs boson, htoH1H2toH1H1foverlinefh\to {H}_1{H}_2\to {H}_1{H}_1f\overline{f}htoH_1H_2toH_1H_1foverlinef h → H 1 H 2 → H 1 H 1 f f ¯ into two DM particles and di-leptons/d...

Research paper thumbnail of Flavon-induced lepton flavour violation

Journal of Physics: Conference Series

ATLAS and CMS have observed a flavor violating decay of the Higgs to muon and tau. The fact that ... more ATLAS and CMS have observed a flavor violating decay of the Higgs to muon and tau. The fact that flavour violating couplings of the Higgs boson are exactly zero in the Standard Model suggests the mixing of the Higgs with another scalar with flavour violating couplings. We use the flavon field from the Froggatt-Nielsen mechanism, responsible for generating the lepton Yukawa matrices, for this purpose. The parameter space is constrained from experimental bounds on charged lepton flavor violation in other processes, however, we show that a substantial region of parameter space survives these bounds while producing a large enough Br(h → µτ).

Research paper thumbnail of CP violating scalar Dark Matter

Journal of High Energy Physics

We study an extension of the Standard Model (SM) in which two copies of the SM scalar SU(2) doubl... more We study an extension of the Standard Model (SM) in which two copies of the SM scalar SU(2) doublet which do not acquire a Vacuum Expectation Value (VEV), and hence are inert, are added to the scalar sector. We allow for CP-violation in the inert sector, where the lightest inert state is protected from decaying to SM particles through the conservation of a Z 2 symmetry. The lightest neutral particle from the inert sector, which has a mixed CP-charge due to CP-violation, is hence a Dark Matter (DM) candidate. We discuss the new regions of DM relic density opened up by CP-violation, and compare our results to the CP-conserving limit and the Inert Doublet Model (IDM). We constrain the parameter space of the CP-violating model using recent results from the Large Hadron Collider (LHC) and DM direct and indirect detection experiments.

Research paper thumbnail of CP violating Two-Higgs-Doublet Model: constraints and LHC predictions

Journal of High Energy Physics

Two-Higgs-Doublet Models (2HDMs) are amongst the simplest extensions of the Standard Model. Such ... more Two-Higgs-Doublet Models (2HDMs) are amongst the simplest extensions of the Standard Model. Such models allow for tree-level CP Violation (CPV) in the Higgs sector. We analyse a class of CPV 2HDM (of Type-I) in which only one of the two Higgs doublets couples to quarks and leptons, avoiding dangerous Flavour Changing Neutral Currents. We provide an up to date and comprehensive analysis of the constraints and Large Hadron Collider (LHC) predictions of such a model. Of immediate interest to the LHC Run 2 is the golden channel where all three neutral Higgs bosons are observed to decay into gauge boson pairs, W W and ZZ, providing a smoking gun signature of the CPV 2HDM.

Research paper thumbnail of Higgs-flavon mixing and h → μτ

Journal of High Energy Physics, 2016

ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, h → µτ. W... more ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, h → µτ. We show that this result can be accommodated through a mixing of the Higgs with a flavon, the field responsible for generating the Yukawa matrices in the lepton sector. We employ a version of the Froggatt-Nielsen mechanism at the electroweak scale, with only the leptons and the flavon transforming non-trivially under the corresponding symmetry group. Non-observation of charged lepton flavor violation (LFV) in other processes imposes important constraints on the model, which we find to be satisfied in substantial regions of parameter space.

Research paper thumbnail of Frustrated symmetries in NHDM

Research paper thumbnail of Observable heavy Higgs dark matter

Journal of High Energy Physics, 2015

Dark Matter (DM), arising from an Inert Higgs Doublet, may either be light, below the W mass, or ... more Dark Matter (DM), arising from an Inert Higgs Doublet, may either be light, below the W mass, or heavy, above about 525 GeV. While the light region may soon be excluded, the heavy region is known to be very difficult to probe with either Direct Detection (DD) experiments or the Large Hadron Collider (LHC). We show that adding a second Inert Higgs Doublet helps to make the heavy DM region accessible to both DD and the LHC, by either increasing its couplings to the observed Higgs boson, or lowering its mass to 360 GeV m DM , or both.

Research paper thumbnail of Stabilizing the Higgs potential with a Z′

Physics Letters B, 2015

Current data point toward metastability of the electroweak vacuum within the Standard Model. We s... more Current data point toward metastability of the electroweak vacuum within the Standard Model. We study the possibility of stabilizing the Higgs potential in U(1) extensions thereof. A generic Z boson improves stability of the scalar potential in two ways: it increases the Higgs self-coupling, due to a positive contribution to the beta-function of the latter, and it decreases the top quark Yukawa coupling, which again has a stabilizing effect. We determine the range of U(1) charges which leads to a stable electroweak vacuum. In certain classes of models, such stabilization is possible even if the Z does not couple to the Higgs and is due entirely to the reduction of the top Yukawa coupling. We also study the effect of the kinetic mixing between the extra U(1) and hypercharge gauge fields.

Research paper thumbnail of CP -violating inflation and its cosmological imprints

Physical Review D

We study models with several SUð2Þ scalar doublets where the inert doublets have a nonminimal cou... more We study models with several SUð2Þ scalar doublets where the inert doublets have a nonminimal coupling to gravity and play the role of the inflaton. We allow for this coupling to be complex, thereby introducing CP violation-a necessary source of the baryon asymmetry-in the Higgs-inflaton couplings. We investigate the inflationary dynamics of the model and discuss how the CP violation of the model is imprinted on the particle asymmetries after inflation in the hot big bang universe.

Research paper thumbnail of Baryogenesis from a CP-Violating Inflation

Proceedings of The International Conference on Beyond Standard Model: From Theory To Experiment

Research paper thumbnail of Pseudo-Goldstone dark matter: gravitational waves and direct-detection blind spots

Journal of High Energy Physics

Pseudo-Goldstone dark matter is a thermal relic with momentum-suppressed direct-detection cross s... more Pseudo-Goldstone dark matter is a thermal relic with momentum-suppressed direct-detection cross section. We study the most general model of pseudo-Goldstone dark matter arising from the complex-singlet extension of the Standard Model. The new U(1) symmetry of the model is explicitly broken down to a CP-like symmetry stabilising dark matter. We study the interplay of direct-detection constraints with the strength of cosmic phase transitions and possible gravitational-wave signals. While large U(1)-breaking interactions can generate a large direct-detection cross section, there are blind spots where the cross section is suppressed. We find that sizeable cubic couplings can give rise to a first-order phase transition in the early universe. We show that there exist regions of the parameter space where the resulting gravitational-wave signal can be detected in future by the proposed Big Bang Observer detector.

Research paper thumbnail of Dark CP violation through the Z portal

Research paper thumbnail of Dark origins of matter-antimatter asymmetry

Proceedings of Corfu Summer Institute 2019 "School and Workshops on Elementary Particle Physics and Gravity" — PoS(CORFU2019)

Research paper thumbnail of Collider signatures of dark CP violation

Research paper thumbnail of Lepton collider indirect signatures of dark CP-violation

The European Physical Journal C

We study an extension of the Standard Model (SM) in which two copies of the SM Higgs doublet are ... more We study an extension of the Standard Model (SM) in which two copies of the SM Higgs doublet are added to the scalar sector. These extra doublets do not develop a vacuum expectation value, hence, they are inert. This essentially leads to a 3-Higgs Doublet Model (3HDM) with 2 inert and 1 active scalar doublets, which we denote as I(2+1)HDM. We allow for CP-violation in the inert sector, where the lightest inert state is protected from decaying to SM particles through the conservation of a Z 2 symmetry, so that it is a Dark Matter (DM) candidate. For this scenario, we identify a smoking gun signature of dark CP-violation in the form of production thresholds of pairs of inert neutral Higgs bosons at an e + e − collider.

Research paper thumbnail of CP violation and BSM Higgs bosons

Proceedings of Prospects for Charged Higgs Discovery at Colliders — PoS(CHARGED2016)

We study extensions of the Standard Model (SM) in which copies of the SM scalar SU(2) doublet are... more We study extensions of the Standard Model (SM) in which copies of the SM scalar SU(2) doublet are added to the Higgs sector. These scalar doublets either acquire a Vacuum Expectation Value (VEV) and hence are active or do not develop a VEV and are inert. We consider CP-violation (CPV) in both the active and inert sector. As an example of a model with CPV in the active sector, we present a Type-I 2-Higgs-Doublet Model (2HDM) with two active doublets and show Large Hadron Collider (LHC) signals of such a scenario. The amount of CPV in this case is very limited due to constraints coming from Electric Dipole Moment experiments. Moreover, 2HDMs with only active doublets do not provide a Dark Matter (DM) candidate. As a result, we turn to 3-Higgs-Doublet Models (3HDMs) where unbounded CPV and viable DM candidates could be introduced simultaneously in the inert sector. We investigate DM phenomenology of such models.

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

Journal of High Energy Physics

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

Research paper thumbnail of Cosmological constraints on light flavons

Journal of High Energy Physics

The Froggatt-Nielsen mechanism is a well-motivated framework for generating the fermion mass hier... more The Froggatt-Nielsen mechanism is a well-motivated framework for generating the fermion mass hierarchy. This mechanism introduces flavons, complex scalars which are singlet under the Standard Model gauge symmetry and charged under a new global family symmetry. We make use of a leptophilic flavon to produce the charged lepton Yukawa matrix. The real part of the flavon mixes with the Higgs boson and introduces lepton flavour violating interactions which are bounded by experiment. The imaginary part of the flavon, η, is a long-lived light particle, whose abundance is restricted by cosmological observations. For m η < 2m e where the decay of η to charged leptons is kinematically forbidden, we identify allowed regions of m η with respect to the vacuum expectation value of the flavon field where all experimental and cosmological constraints are satisfied.

Research paper thumbnail of Direct and indirect probes of Goldstone dark matter

Research paper thumbnail of Singlet scalar and 2HDM extensions of the Standard Model: CP-violation and constraints from (g − 2)μ and eEDM

Journal of High Energy Physics

We study popular scalar extensions of the Standard Model, namely the singlet extension, the 2-Hig... more We study popular scalar extensions of the Standard Model, namely the singlet extension, the 2-Higgs doublet model (2HDM) and its extension by a singlet scalar. We focus on the contributions of the added scalars to the anomalous magnetic moment of the muon, (g − 2) µ in the presence of CP-violation, and the electric dipole moment of the electron (eEDM) in these models. In the absence of CP-violation, CP-even and CP-odd scalars contribute with an opposite sign to the anomalous magnetic moment of the muon and as a result these models generally require very light scalars to explain the observed discrepancy in (g − 2) µ. We study the effect of CP-violation on the anomalous magnetic moment of the muon and its compatibility with the eEDM constraints. We show that given the current status of the global set of constraints applied on all values of cot β, in the CP-violating scalar extensions, there exist no viable parameter space in agreement with both a µ and eEDM bounds.

Research paper thumbnail of Dark Matter signals at the LHC from a 3HDM

Journal of High Energy Physics

We analyse new signals of Dark Matter (DM) at the Large Hadron Collider (LHC) in a 3-Higgs Double... more We analyse new signals of Dark Matter (DM) at the Large Hadron Collider (LHC) in a 3-Higgs Doublet Model (3HDM) where only one doublet acquires a Vacuum Expectation Value (VEV), preserving a parity Z 2. The other two doublets are inert and do not develop a VEV, leading to a dark scalar sector controlled by Z 2, with the lightest CP-even dark scalar H 1 being the DM candidate. This leads to the loop induced decay of the next-to-lightest scalar, H2toH1foverlinefleft(f=u,d,c,s,b,e,mu,tauright){H}_2\to {H}_1f\overline{f}\left(f=u,d,c,s,b,e,\mu, \tau \right)H2toH1foverlinefleft(f=u,d,c,s,b,e,mu,tauright) H 2 → H 1 f f ¯ f = u , d , c , s , b , e , μ , τ , mediated by both dark CP-odd and charged scalars. This is a smoking-gun signal of the 3HDM since it is not allowed in the 2HDM with one inert doublet and is expected to be important when H 2 and H 1 are close in mass. In practice, this signature can be observed in the cascade decay of the SM-like Higgs boson, htoH1H2toH1H1foverlinefh\to {H}_1{H}_2\to {H}_1{H}_1f\overline{f}htoH_1H_2toH_1H_1foverlinef h → H 1 H 2 → H 1 H 1 f f ¯ into two DM particles and di-leptons/d...

Research paper thumbnail of Flavon-induced lepton flavour violation

Journal of Physics: Conference Series

ATLAS and CMS have observed a flavor violating decay of the Higgs to muon and tau. The fact that ... more ATLAS and CMS have observed a flavor violating decay of the Higgs to muon and tau. The fact that flavour violating couplings of the Higgs boson are exactly zero in the Standard Model suggests the mixing of the Higgs with another scalar with flavour violating couplings. We use the flavon field from the Froggatt-Nielsen mechanism, responsible for generating the lepton Yukawa matrices, for this purpose. The parameter space is constrained from experimental bounds on charged lepton flavor violation in other processes, however, we show that a substantial region of parameter space survives these bounds while producing a large enough Br(h → µτ).

Research paper thumbnail of CP violating scalar Dark Matter

Journal of High Energy Physics

We study an extension of the Standard Model (SM) in which two copies of the SM scalar SU(2) doubl... more We study an extension of the Standard Model (SM) in which two copies of the SM scalar SU(2) doublet which do not acquire a Vacuum Expectation Value (VEV), and hence are inert, are added to the scalar sector. We allow for CP-violation in the inert sector, where the lightest inert state is protected from decaying to SM particles through the conservation of a Z 2 symmetry. The lightest neutral particle from the inert sector, which has a mixed CP-charge due to CP-violation, is hence a Dark Matter (DM) candidate. We discuss the new regions of DM relic density opened up by CP-violation, and compare our results to the CP-conserving limit and the Inert Doublet Model (IDM). We constrain the parameter space of the CP-violating model using recent results from the Large Hadron Collider (LHC) and DM direct and indirect detection experiments.

Research paper thumbnail of CP violating Two-Higgs-Doublet Model: constraints and LHC predictions

Journal of High Energy Physics

Two-Higgs-Doublet Models (2HDMs) are amongst the simplest extensions of the Standard Model. Such ... more Two-Higgs-Doublet Models (2HDMs) are amongst the simplest extensions of the Standard Model. Such models allow for tree-level CP Violation (CPV) in the Higgs sector. We analyse a class of CPV 2HDM (of Type-I) in which only one of the two Higgs doublets couples to quarks and leptons, avoiding dangerous Flavour Changing Neutral Currents. We provide an up to date and comprehensive analysis of the constraints and Large Hadron Collider (LHC) predictions of such a model. Of immediate interest to the LHC Run 2 is the golden channel where all three neutral Higgs bosons are observed to decay into gauge boson pairs, W W and ZZ, providing a smoking gun signature of the CPV 2HDM.

Research paper thumbnail of Higgs-flavon mixing and h → μτ

Journal of High Energy Physics, 2016

ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, h → µτ. W... more ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, h → µτ. We show that this result can be accommodated through a mixing of the Higgs with a flavon, the field responsible for generating the Yukawa matrices in the lepton sector. We employ a version of the Froggatt-Nielsen mechanism at the electroweak scale, with only the leptons and the flavon transforming non-trivially under the corresponding symmetry group. Non-observation of charged lepton flavor violation (LFV) in other processes imposes important constraints on the model, which we find to be satisfied in substantial regions of parameter space.

Research paper thumbnail of Frustrated symmetries in NHDM

Research paper thumbnail of Observable heavy Higgs dark matter

Journal of High Energy Physics, 2015

Dark Matter (DM), arising from an Inert Higgs Doublet, may either be light, below the W mass, or ... more Dark Matter (DM), arising from an Inert Higgs Doublet, may either be light, below the W mass, or heavy, above about 525 GeV. While the light region may soon be excluded, the heavy region is known to be very difficult to probe with either Direct Detection (DD) experiments or the Large Hadron Collider (LHC). We show that adding a second Inert Higgs Doublet helps to make the heavy DM region accessible to both DD and the LHC, by either increasing its couplings to the observed Higgs boson, or lowering its mass to 360 GeV m DM , or both.

Research paper thumbnail of Stabilizing the Higgs potential with a Z′

Physics Letters B, 2015

Current data point toward metastability of the electroweak vacuum within the Standard Model. We s... more Current data point toward metastability of the electroweak vacuum within the Standard Model. We study the possibility of stabilizing the Higgs potential in U(1) extensions thereof. A generic Z boson improves stability of the scalar potential in two ways: it increases the Higgs self-coupling, due to a positive contribution to the beta-function of the latter, and it decreases the top quark Yukawa coupling, which again has a stabilizing effect. We determine the range of U(1) charges which leads to a stable electroweak vacuum. In certain classes of models, such stabilization is possible even if the Z does not couple to the Higgs and is due entirely to the reduction of the top Yukawa coupling. We also study the effect of the kinetic mixing between the extra U(1) and hypercharge gauge fields.