Charged Higgs Mass Research Articles

Single top events as a source of light charged Higgs in the fully hadronic final state at LHC

The single top production proceeds through different channels at LHC. The t-channel production which has a cross section at the level of one third of the ttbar, can be regarded as a source of light charged Higgs boson through top quark decay to charged Higgs. Due to the low jet multiplicity and characteristic kinematic features of this process, a signal selection can be designed to extract charged Higgs signal from the background processes. In this paper, taking MSSM as the theoretical framework, The light charged Higgs signal from single top events is analyzed. The charged Higgs is assumed to decay to tau nu and the hadronic decay of tau leptons is analyzed. Different charged Higgs mass hypotheses are analyzed and a scan over the parameter space (mH+,tanbeta) is performed. It is shown that this process has the potential to exclude large areas of parameter space, while with enough data, a 5 sigma discovery would also be possible. Finally 95% C.L. exclusion and 5 sigma contours are provided for different integrated luminosities of LHC.

Charged Higgs boson detection in theτνdecay mode at future linear colliders

Charged Higgs phenomenology and detection chance at future linear colliders through the production process $e^{-}e^{+} \ra H^{+}H^{-} \ra \tau^{+}\nu \tau \bar{\nu}$ is studied. Both charged Higgs bosons are considered to decay to $\tau\nu$ and the hadronic decay of $\tau$ leptons is analyzed taking into account spin and kinematics effects using a proper simulation of the $\tau$ lepton decay. It is shown that within the MSSM framework, with \tanb = 10, a wide range of charged Higgs masses would have detectable signal beyond the $5\sigma$ statistical significance at linear colliders with $\sqrt{s} = 500$ and 1000 GeV.

ENHANCEMENT OF CHARGED HIGGS PRODUCTION IN ASSOCIATION WITH W± AT MUON COLLIDERS IN GENERAL TWO HIGGS DOUBLET MODELS

The charged Higgs production associated with a W± boson has a smooth cross-section as a function of the charged Higgs mass at muon colliders. The cross-section in minimal supersymmetric standard model (MSSM) is about 25 fb in the range 200 GeV < mH± <400 GeV with tan β = 50. This is much larger than the corresponding cross-section at an e+e- collider which reaches a fraction of femtobarn. The observability of this charged Higgs production at a muon collider has been recently studied in an earlier work leading to the result that with 1 ab-1, a 5σ signal can be observed throughout the aforementioned mass range. In this paper, results of a study based on a general two Higgs doublet model (types II and III) are presented and the cross-section of the charged Higgs production in the most sensitive parameter space is evaluated. It is concluded that the cross-section increases with increasing neutral Higgs boson masses involved in the s-channel diagram and can be as large as several picobarn with tan β = 50. The region of "physical Higgs boson mass" parameter space which could lead to a 5σ signal at 50 fb-1 is specified.

Charged Higgs observability through associated production with W ± at a muon collider

The observability of a charged Higgs boson produced in association with a W boson at future muon colliders is studied. The analysis is performed within the MSSM framework. The charged Higgs is assumed to decay to tb and a fully hadronic final state is analyzed, i.e., mu+mu- \rightarrow H\pmW\mp \rightarrow tbW \rightarrow WbbW \rightarrow jjjjbb. The main background is tt production in fully hadronic final state which is an irreducible background with very similar kinematic features. It is shown that although the discovery potential is almost the same for a charged Higgs mass in the range 200 GeV < mH\pm < 400 GeV, the signal significance is about 1sigma for tanbeta = 50 at integrated luminosity of 50 fb-1. The signal rate is well above that at e+e- linear colliders with the same center of mass energy and enough data (O(1 ab-1)) will provide the same discovery potential for all heavy charged Higgs masses up to mH\pm \sim 400 GeV, however, the muon collider cannot add anything to the LHC findings.

Revisiting the Γ(K→eν)/Γ(K→μν) ratio in supersymmetric unified models

It has been pointed out that supersymmetric extensions of the Standard Model can induce significant changes to the theoretical prediction of the ratio Γ(K→eν)/Γ(K→μν)≡R K , through lepton flavour violating couplings. In this work we carry out a full computation of all one-loop corrections to the relevant νlH + vertex, and discuss the new contributions to R K arising in the context of different constrained (minimal supergravity-inspired) models which succeed in accounting for neutrino data, further considering the possibility of accommodating a near-future observation of a μ→eγ transition. We also re-evaluate the prospects for R K in the framework of unconstrained supersymmetric models. In all cases, we address the question of whether it is possible to saturate the current experimental sensitivity on R K while in agreement with the recent limits on B-meson decay observables (in particular BR(B s →μ + μ −) and BR(B u →τν)), as well as BR(τ→eγ) and available collider constraints. Our findings reveal that in view of the recent bounds, and even when enhanced by effective sources of flavour violation in the right-handed $\tilde{e}-\tilde{\tau}$ sector, constrained supersymmetric (seesaw) models typically provide excessively small contributions to R K . Larger contributions can be found in more general settings, where the charged Higgs mass can be effectively lowered, and even further enhanced in the unconstrained MSSM. However, our analysis clearly shows that even in this last case SUSY contributions to R K are still unable to saturate the current experimental bounds on this observable, especially due to a strong tension with the B u →τν bound.

Decay properties of a class of doubly charged Higgs bosons

We study the leptonic decays of a doubly charged Higgs bosons class which is predicted by a model based on the SU(3)C⊗SU(2)L⊗U(1)N electroweak gauge symmetry. In contrast to other models, decays into τ±τ± are largely dominant (99.5% or more). Coupling of these scalars to two standard charged gauge bosons are either zero or very suppressed. Couplings to two different flavor of charged leptons do not occur. Some coupling features imposed by symmetry and representation content lead to simple relationships between decay rates and doubly charged Higgs masses. Some of the parameters depend only on the decay widths and on the charged lepton masses. In order to clarify the relevance of our results, some aspects of this model are compared with the Higgs triplet model.

Observability of light charged Higgs decay to muon in top quark pair events at LHC

In this paper the charged Higgs signal through the decay to a pair of muon and neutrino (H -> mu nu) is analyzed. The analysis attempts to estimate the amount of muonic signal of the charged Higgs at LHC at a center of mass energy of 14 TeV. The signal process is the top quark pair production with one of the top quarks decaying to a charged Higgs (non SM anomalous top quark decay) and the other decaying to a W boson which is assumed to decay hadronically to two light jets. Due to the small branching ratio of charged Higgs decay to muon, results are quoted for data corresponding to an integrated luminosity of 300 fb^-1 which is expected to be collected at the LHC high luminosity regime. It is shown that a signal significance close to 5 down to below 1 is achievable for a charged Higgs mass in the range 80 GeV < m(H \pm) < 150 GeV taking the top quark pair production with both top quarks decaying to W bosons as the main irreducible background.

Precision electroweak tests of the standard model

CKM Unitarity in the Standard Model predicts |Vud|2 + |Vus|2 + |Vub|2 = 1. Experiments currently give 0.9999(6). The outstanding agreement constrains "new physics" effects at the tree and quantum loop level. Examples considered are: exotic muon decays, heavy quark or lepton mixing, high scale induced 4 fermion operators (e.g. excited W bosons from extra dimensions) and additional Z′ gauge bosons. Also, combining Kμ2 decays and CKM unitarity gives a charged Higgs mass bound mH± ≳ 5tan β GeV. Constraints from other precisely measured electroweak observables are also discussed.

CONSTRAINTS ON THE CHARGED HIGGS BOSON OF THE TWO-HIGGS DOUBLET MODEL TYPE III

The D0 experiment has reported a direct search for a charged Higgs boson produced by [Formula: see text] annihilation and decaying to [Formula: see text] final state, in the 180≤MH+≤300 GeV mass range. The analysis has led to upper limits on the production cross-section in the framework of the two-Higgs doublet model types I, II and III. We compare the predictions of two different scenarios in the framework of the two-Higgs doublet type III to the cross-section limits reported by D0 collaboration, and we obtain constraints on the charged Higgs mass, for the case when the charged Higgs mass is bigger than the top quark mass. Also, searches for the charged Higgs boson with a mass smaller than top quark mass are considered, we discuss the possible limits on the charged Higgs boson mass obtained from measurements of the ratio [Formula: see text] within the two-Higgs doublet model type III.

AnomalousB-meson mixing and baryogenesis

There exist experimental hints from the B sector for CP violation beyond the Standard Model (SM) CKM paradigm. An anomalous dimuon asymmetry was reported by the D0 collaboration, while tension exists between $B \to \tau \nu$ and $S_{\psi K}$. These measurements, disfavoring the SM at the ~3$\sigma$ level, can be explained by new physics in both $B_d$-$\bar{B}_d$ and $B_s$- $\bar{B}_s$ mixing, arising from (1) new bosonic degrees of freedom at or near the electroweak scale, and (2) new, large CP-violating phases. These two new physics ingredients are precisely what is required for electroweak baryogenesis to work in an extension of the SM. We show that a simple two Higgs doublet model with top-charm flavor violation can explain the B anomalies and the baryon asymmetry of the Universe. Moreover, the presence of a large relative phase in the top-charm Yukawa coupling, favored by $B_{d,s}$-$\bar{B}_{d,s}$ mixing, weakens constraints from $\epsilon_K$ and $b \to s \gamma$, allowing for a light charged Higgs mass of O(100 GeV).

Erratum to: Revisiting the global electroweak fit of the Standard Model and beyond with Gfitter

The global fit of the Standard Model to electroweak precision data, routinely performed by the LEP electroweak working group and others, demonstrated impressively the predictive power of electroweak unification and quantum loop corrections. We have revisited this fit in view of (i) the development of the new generic fitting package Gfitter, (ii) the insertion of constraints from direct Higgs searches at LEP and the Tevatron, and (iii) a more thorough statistical interpretation of the results. Gfitter is a modular fitting toolkit, which features predictive theoretical models as independent plugins, and a statistical analysis of the fit results using toy Monte Carlo techniques. The state-of-the-art electroweak Standard Model is fully implemented, as well as generic extensions to it. This paper introduces the Gfitter project, and presents state-of-the-art results for the global electroweak fit in the Standard Model, and for a model with an extended Higgs sector (2HDM). Numerical and graphical results for fits with and without including the constraints from the direct Higgs searches at LEP and Tevatron are given. Perspectives for future colliders are analysed and discussed. Including the direct Higgs searches, we find M_H=(116.4 +18.3 -1.3) GeV, and the 2sigma and 3sigma allowed regions [114,145] GeV and [[113,168] and [180,225]] GeV, respectively. For the strong coupling strength at fourth perturbative order we obtain alpha_S(M_Z)=0.1193 +0.0028 -0.0027(exp) +- 0.0001(theo). Finally, for the mass of the top quark, excluding the direct measurements, we find m_t=(178.2 +9.8 -4.2) GeV. In the 2HDM we exclude a charged-Higgs mass below 240 GeV at 95% confidence level. This limit increases towards larger tan(beta), where e.g., M_H+-<780 GeV is excluded for tan(beta)=70.

Leptonic signatures of doubly charged Higgs boson production at the LHC

The production of doubly charged Higgs bosons (H^{\pm\pm}) at the CERN LHC can give rise to distinctive multi-lepton signatures. The discovery potential of H^{\pm\pm} can be optimized by considering a search strategy which is sensitive to both of the dominant production mechanisms, q\bar q\to H^{++}H^{--} and q\bar {q'}\to H^{\pm\pm}H^{\mp}. We compare the discovery potential for the signatures of exactly four leptons and at least three leptons in the final state, using the same set of cuts. We have carried out fast detector simulations at the LHC for both signal and backgrounds for a wide range of values of the charged Higgs mass. We find that the use of the latter channel can substantially improve the detection prospects of the doubly charged Higgs boson at the LHC.

Two Higgs doublet model of type II facing flavor physics data

We discuss tests of the charged Higgs sector of the Two Higgs Doublet Model (2HDM) of Type II in the light of recent flavour physics data. Particular attention is paid to recent measurement of purely leptonic decays of heavy-light mesons, which depart more or less significantly from the Standard Model (SM) predictions. We derive constraints on the parameters of the 2HDM type II from leptonic and semileptonic $\Delta F=1$ decays as well as loop processes ($b \to s \gamma$, $B\bar{B}$ mixing or $Z\to\bar{b}b$) sensitive to charged Higgs contributions. The outcome of this work is that while 2HDM Type II can fit individual observable through fine-tuning schemes, in a combined analysis it does not perform better than the SM by favouring a decoupling solution. Assuming that 2HDM Type II is realized in Nature, constraints on its parameters ($m_{H^+}$ and $\tan \beta$) are derived. A limit on the charged Higgs mass $m_{H^+} > 316 \; {\rm GeV}$ at $95\%$~CL is obtained irrespective of the value of $\tan \beta$. This limit is dominated by the $b\rightarrow s \gamma$ branching ratio measurement. All results have been obtained with the \ckmfitter\ analysis package, featuring the frequentist statistical approach \rfit\ to handle theoretical uncertainties.

Implications of Yukawa textures in the decay H+ → W+γ within the 2HDM-III

We discuss the implications of assuming a four-zero Yukawa texture for the charged Higgs decay H+ → W+γ at the one-loop level, within the context of the general two-Higgs doublet model of type III. We begin by presenting a detailed analysis of the charged Higgs boson couplings with heavy quarks and the resulting effects on their decays. In particular, we present the possible enhancement of the decay H+ → W+γ, whose branching ratio could be of the order 10−2, for charged Higgs mass of the order 180 GeV. These parameters can still avoid the B → Xsγ constraint, the perturbativity and ρ0 bound. We show that BR(H+ → W+γ) ∼ 10−2 is favored by the constraints of mixing and of the radiative corrections to the vertex in the regime small tan β. In a scenario favored by all the above restrictions, we study the production of charged Higgs bosons, which is also sensitive to the modifications of its couplings, and we evaluate the events rates at the LHC, including the ‘direct’ and ‘indirect’ production channels. We get an event rate of order 60 (120) for ‘direct’ (‘indirect’) production reaction and including the decay H+ → W+γ in the final state, with an integrated luminosity of 105 pb−1.

Charged Higgs phenomenology in the flipped two-Higgs-doublet model

We study the phenomenology of the charged Higgs boson in the "flipped" two Higgs doublet model, in which one doublet gives mass to up-type quarks and charged leptons and the other gives mass to down-type quarks. We present the charged Higgs branching ratios and summarize the indirect constraints. We extrapolate existing LEP searches for H+H- and Tevatron searches for t tbar with t --> H+ b into the flipped model and extract constraints on MH+ and the parameter tan(beta). We finish by reviewing existing LHC charged Higgs searches and suggest that the LHC reach in this model could be extended for charged Higgs masses below the tb threshold by considering t tbar with t --> H+ b and H+ --> q qbar, as has been used in Tevatron searches.

Higgs masses in the four generation minimal supersymmetric standard model

In the minimal supersymmetric standard model with three generations of fermions, there is a stringent upper bound on the mass of the lightest neutral Higgs $h$, and the mass of the charged Higgs ${H}^{+}$ must be close (within tens of GeV) to the heavier neutral Higgs $H$ and the pseudoscalar Higgs $A$. In this paper, we show that in the four generation minimal supersymmetric standard model, the upper bound on the $h$ mass is much higher, as high as 400 GeV, and ${H}^{+}$ is generally much heavier than the $A$, allowing the ${H}^{+}\ensuremath{\rightarrow}A{W}^{+}$ decay, potentially changing search strategies for both the charged Higgs and the pseudoscalar. The $H$ mass, on the other hand, remains within tens of GeV of the charged Higgs mass.

Bs,d−B¯s,dmixings andb→q(γ,ll¯)decays in private Higgs model

We study the low energy phenomena induced by the lightest charged Higgs in the private Higgs model, in which each quark flavor is associated with a Higgs doublet. We show that the couplings of the charged Higgs scalars to fermions are fixed and the unknown parameters are only the masses and mixing elements of the charged Higgs scalars. As the charged Higgs masses satisfy with ${M}_{b}&lt;{M}_{c}\ensuremath{\ll}{M}_{s}\ensuremath{\ll}{M}_{d,u}$, processes involving $B$-meson are expected to be the ideal places to test the private Higgs model. In particular, we explore the constraints on the model from experimental data in $B$ physics, such as the branching ratio (BR) and $CP$ asymmetry of $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$, ${B}_{d,s}\mathrm{\text{\ensuremath{-}}}{\overline{B}}_{d,s}$ mixings and the BR for $B\ensuremath{\rightarrow}{K}^{*}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$. We illustrate that the sign of the Wilson coefficient for $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ can be different from that in the standard model, while this flipped sign can be displayed by the forward-backward asymmetry of $B\ensuremath{\rightarrow}V{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ with $V$ a vector meson. We also demonstrate that ${B}_{d,s}\mathrm{\text{\ensuremath{-}}}{\overline{B}}_{d,s}$ mixings and their time-dependent $CP$ asymmetries are negligible small and the BR of $B\ensuremath{\rightarrow}{K}^{*}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ can have a more strict bound than that of $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$.

Single Higgs-boson production through γγ scattering within the general 2HDM

The production of a single neutral Higgs boson h through (loop-induced) γγ collisions is explored in the context of the linear colliders within the general Two-Higgs-Doublet Model (2HDM). Two different mechanisms are analyzed: on the one hand, the scattering γγ→h of two real photons in a γγ collider; on the other, the more traditional mechanism of virtual photon fusion, e+e−→e+e−γ∗γ∗→e+e−+h. Owing to the peculiar properties of the Higgs boson self-interactions within the general 2HDM, we find that the overall production rates can be boosted up significantly, provided the charged Higgs mass is not too heavy. For example, if MH±≳100 GeV and, in addition, Mh0 falls in the ballpark of the LEP bound on the SM Higgs mass up to a few hundred GeV, the cross-sections may typically render 〈σγγ→h〉∼0.1–1 pb and σ(e+e−→e+e−h0)≲0.01 pb – in both cases well above the SM prediction. Although for MH±>300 GeV the rates become virtually insensitive to the Higgs boson self-couplings, a significant tail of non-SM effects produced by the combined contribution of the Yukawa couplings and gauge bosons could still reveal a smoking gun.

Revisiting the global electroweak fit of the Standard Model and beyond with Gfitter

The global fit of the Standard Model to electroweak precision data, routinely performed by the LEP electroweak working group and others, demonstrated impressively the predictive power of electroweak unification and quantum loop corrections. We have revisited this fit in view of (i) the development of the new generic fitting package, Gfitter, allowing for flexible and efficient model testing in high-energy physics, (ii) the insertion of constraints from direct Higgs searches at LEP and the Tevatron, and (iii) a more thorough statistical interpretation of the results. Gfitter is a modular fitting toolkit, which features predictive theoretical models as independent plug-ins, and a statistical analysis of the fit results using toy Monte Carlo techniques. The state-of-the-art electroweak Standard Model is fully implemented, as well as generic extensions to it. Theoretical uncertainties are explicitly included in the fit through scale parameters varying within given error ranges. This paper introduces the Gfitter project, and presents state-of-the-art results for the global electroweak fit in the Standard Model (SM), and for a model with an extended Higgs sector (2HDM). Numerical and graphical results for fits with and without including the constraints from the direct Higgs searches at LEP and Tevatron are given. Perspectives for future colliders are analysed and discussed. In the SM fit including the direct Higgs searches, we find M H =116.4 −1.3 +18.3 GeV, and the 2σ and 3σ allowed regions [114,145] GeV and [[113,168] and [180,225]] GeV, respectively. For the strong coupling strength at fourth perturbative order we obtain α S (M 2 )=0.1193 −0.0027 +0.0028 (exp )±0.0001 (theo). Finally, for the mass of the top quark, excluding the direct measurements, we find m t =178.2 −4.2 +9.8 GeV. In the 2HDM we exclude a charged-Higgs mass below 240 GeV at 95% confidence level. This limit increases towards larger tan β, e.g., $M_{H^{\pm}}<780 \mbox{GeV}$ is excluded for tan β=70.

Some consequences of a Higgs triplet

We consider an extension of the scalar sector of the Standard Model with a single complex Higgs triplet X. Such extensions are the most economic, model-independent way of generating neutrino masses through triplet interactions. We show that a term like a0ΦΦX† must be included in the most general potential of such a scenario in order to avoid a massless neutral physical scalar. We also demonstrate that a0 must be real, thus ruling out any additional source of CP violation. We then examine the implications of this term in the mass matrices of the singly and doubly charged scalar, neutral scalar and pseudoscalar fields. We find that, for small values of a0/v2, where v2 is the triplet vev, the spectrum allows the decay of heavier scalars into lighter ones via gauge interactions. For large a0/v2, the doubly charged, singly charged and neutral pseudoscalar bosons become practically degenerate, while the even-parity neutral scalars remain considerably lighter, thus emphasizing the possibility of decay of the singly charged or neutral pseudoscalar states into the neutral scalars. Constraints from the ρ-parameter are used to find nontrivial limits on the charged Higgs mass depending on a0. We also study the couplings of the various physical states in this scenario. For small values of |a0|/v2, we find the lightest neutral scalar field to be triplet dominated, and thus having extremely suppressed interactions with fermion as well as gauge–boson pairs.