G2HDM : Gauged Two Higgs Doublet Model

A novel model embedding the two Higgs doublets in the popular two Higgs doublet models into a doublet of a non-abelian gauge group $SU(2)_H$ is presented. The Standard Model $SU(2)_L$ right-handed fermion singlets are paired up with new heavy fermions to form $SU(2)_H$ doublets, while $SU(2)_L$ left-handed fermion doublets are singlets under $SU(2)_H$. Distinctive features of this anomaly-free model are: (1) Electroweak symmetry breaking is induced from spontaneous symmetry breaking of $SU(2)_H$ via its triplet vacuum expectation value; (2) One of the Higgs doublet can be inert, with its neutral component being a dark matter candidate as protected by the $SU(2)_H$ gauge symmetry instead of a discrete $Z_2$ symmetry in the usual case; (3) Unlike Left-Right Symmetric Models, the complex gauge fields $(W_1^{\prime}\mp i W_2^{\prime})$ (along with other complex scalar fields) associated with the $SU(2)_H$ do {\it not} carry electric charges, while the third component $W^{\prime}_3$ can mix with the hypercharge $U(1)_Y$ gauge field and the third component of $SU(2)_L$; (4) Absence of tree level flavour changing neutral current is guaranteed by gauge symmetry; and {\it etc}. In this work, we concentrate on the mass spectra of scalar and gauge bosons in the model. Constraints from previous $Z^\prime$ data at LEP and the Large Hadron Collider measurements of the Standard Model Higgs mass, its partial widths of $\gamma\gamma$ and $Z\gamma$ modes are discussed.Comment: 40 pages, 7 figures, version accepted in JHEP, relic density discussion adde

Top Quark Rare Decays via Loop-Induced FCNC Interactions in Extended Mirror Fermion Model

Flavor changing neutral current (FCNC) interactions for a top quark $t$ decays into $Xq$ with $X$ represents a neutral gauge or Higgs boson, and $q$ a up- or charm-quark are highly suppressed in the Standard Model (SM) due to the Glashow-Iliopoulos-Miami mechanism. Whilst current limits on the branching ratios of these processes have been established at the order of $10^{-4}$ from the Large Hadron Collider experiments, SM predictions are at least nine orders of magnitude below. In this work, we study some of these FCNC processes in the context of an extended mirror fermion model, originally proposed to implement the electroweak scale seesaw mechanism for non-sterile right-handed neutrinos. We show that one can probe the process $t \to Zc$ for a wide range of parameter space with branching ratios varying from $10^{-6}$ to $10^{-8}$, comparable with various new physics models including the general two Higgs doublet model with or without flavor violations at tree level, minimal supersymmetric standard model with or without $R$-parity, and extra dimension model.Comment: 30 pages, 8 figures, 2 tables and 1 appendix. Version to appear in NP

Consistency of a gauged two-Higgs-doublet model: Scalar sector

We study the theoretical and phenomenological constraints imposed on the scalar sector of the gauged two Higgs doublet model proposed recently as a variant of the popular inert Higgs doublet model of dark matter. The requirements of tree-level vacuum stability and perturbative unitarity in the scalar sector are analyzed in detail. Furthermore, taking into account the constraints from the 125 GeV Higgs boson measurements at the Large Hadron Collider, we map out the allowed ranges for the fundamental parameters of the scalar potential in the model.Comment: 41 pages, 31 figures. V2: Content added to section III.A, references added, content matches version published in PR

Signals of New Gauge Bosons in Gauged Two Higgs Doublet Model

Recently a gauged two Higgs doublet model, in which the two Higgs doublets are embedded into the fundamental representation of an extra local $SU(2)_H$ group, is constructed. Both the new gauge bosons $Z^\prime$ and $W^{\prime (p,m)}$ are electrically neutral. While $Z^\prime$ can be singly produced at colliders, $W^{\prime (p,m)}$, which is heavier, must be pair produced. We explore the constraints of $Z^\prime$ using the current Drell-Yan type data from the Large Hadron Collider. Anticipating optimistically that $Z^\prime$ can be discovered via the clean Drell-Yan type signals at high luminosity upgrade of the collider, we explore the detectability of extra heavy fermions in the model via the two leptons/jets plus missing transverse energy signals from the exotic decay modes of $Z^\prime$. For the $W^{\prime (p,m)}$ pair production in a future 100 TeV proton-proton collider, we demonstrate certain kinematical distributions for the two/four leptons plus missing energy signals have distinguishable features from the Standard Model background. In addition, comparisons of these kinematical distributions between the gauged two Higgs doublet model and the littlest Higgs model with T-parity, the latter of which can give rise to the same signals with competitive if not larger cross sections, are also presented.Comment: 39 pages, 23 figures, 7 tables and two new appendixes, to appear in EPJ

Patient and health system delays in the diagnosis and treatment of new and retreatment pulmonary tuberculosis cases in Malawi

BACKGROUND: Tuberculosis (TB) control remains a challenge in Malawi despite the National TB Control Program since 1984. This study aimed at measuring patient and health system delays and identifying factors associated with these delays. METHODS: A cross-sectional survey of 588 pulmonary TB patients was conducted in three TB centres in Blantyre, Lilongwe, and Mzuzu, between July and December 2011 using a semi-structured questionnaire. Patient delay was defined as the time interval between the onset of TB symptom(s) (a common symptom being coughing) to the first visit to any health provider. Health system delay was the interval from the first care-seeking visit at any health provider to the initiation of anti-tuberculosis treatment. Participants were invited to participate in the study during intensive phase of treatment. The characteristics associated with patient and health system delays were analyzed. RESULTS: The median patient delay was 14 days for both new and retreatment TB cases (interquartile range [IQR] 14 – 28 and 7 – 21, respectively). The median health system delay was 59 days (IQR 26 – 108) for new and 40.5 days (IQR 21–90) for retreatment cases. Factors associated with longer patient delay in new cases included primary education (adjusted odds ratio [AOR] 2.2, 95% CI 1.3 – 3.9) and knowledge that more than three weeks of coughing is a sign of TB (AOR 1.9, 1.1 – 3.3). In retreatment cases, distance >10 Km (AOR 3.3, 1.1 – 9.6) and knowledge that more than three weeks of coughing is a sign of TB (AOR 3.7, 1.3 – 10.7; p < 0.05) were significant factors. Making the first visit to a health centre (OR 1.9, 0.9 – 3.8) or a drug store/ traditional healer (OR 5.1, 1.1 – 21.7) in new TB cases were associated with a longer health system delay (p < 0.05) while smear negative (OR 6.4, 1.5 – 28.3), and smear unknown or not done (OR 6.1, 1.3 – 26.9) among retreatment cases were associated with a longer health system delay (p < 0.05). CONCLUSIONS: Effective management and new diagnostic techniques are needed especially among retreatment cases. It is also needed to address geographic barriers to accessing care and increasing TB awareness in the community