41 research outputs found
Constraining parameter space in type-II two-Higgs doublet model in light of a 126 GeV Higgs boson
We explore the implications of a 126 GeV Higgs boson indicated by the recent
LHC results for two-Higgs doublet model (2HDM). Identifying the 126 GeV Higgs
boson as either the lighter or heavier of CP even neutral Higgs bosons in 2HDM,
we examine how the masses of Higgs fields and mixing parameters can be
constrained by the theoretical conditions and experimental constraints. The
theoretical conditions taken into account are the vacuum stability,
perturbativity and unitarity required to be satisfied up to a cut-off scale. We
also show how bounds on the masses of Higgs bosons and mixing parameters depend
on the cut-off scale. In addition, we investigate whether the allowed regions
of parameter space can accommodate particularly the enhanced di-photon signals,
ZZ* and WW* decay modes of the Higgs boson, and examine the prediction of the
signal strength of Z{\gamma} decay mode for the allowed regions of the
parameter space.Comment: To be published in JHEP, 20 pages, 11 figures, Figures and results
are updated for the recent LHC result
Viability of MSSM scenarios at very large tan(beta)
We investigate the MSSM with very large tan(beta) > 50, where the fermion
masses are strongly affected by loop-induced couplings to the "wrong" Higgs,
imposing perturbative Yukawa couplings and constraints from flavour physics.
Performing a low-energy scan of the MSSM with flavour-blind soft terms, we find
that the branching ratio of B->tau nu and the anomalous magnetic moment of the
muon are the strongest constraints at very large tan(beta) and identify the
viable regions in parameter space. Furthermore we determine the scale at which
the perturbativity of the Yukawa sector breaks down, depending on the
low-energy MSSM parameters. Next, we analyse the very large tan(beta) regime of
General Gauge Mediation (GGM) with a low mediation scale. We investigate the
requirements on the parameter space and discuss the implied flavour
phenomenology. We point out that the possibility of a vanishing Bmu term at a
mediation scale M = 100 TeV is challenged by the experimental data on B->tau nu
and the anomalous magnetic moment of the muon.Comment: 29 pages, 7 figures. v2: discussion in sections 1 and 4 expanded,
conclusions unchanged. Matches version published in JHE
Probing the charged Higgs boson at the LHC in the CP-violating type-II 2HDM
We present a phenomenological study of a CP-violating two-Higgs-doublet Model
with type-II Yukawa couplings at the Large Hadron Collider (LHC). In the light
of recent LHC data, we focus on the parameter space that survives the current
and past experimental constraints as well as theoretical bounds on the model.
Once the phenomenological scenario is set, we analyse the scope of the LHC in
exploring this model through the discovery of a charged Higgs boson produced in
association with a W boson, with the former decaying into the lightest neutral
Higgs and a second W state, altogether yielding a b\bar b W^+W^- signature, of
which we exploit the W^+W^- semileptonic decays.Comment: 37 pages, 16 figures; v2 updated treatment of LHC constraint
Charged-Higgs phenomenology in the Aligned two-Higgs-doublet model
The alignment in flavour space of the Yukawa matrices of a general
two-Higgs-doublet model results in the absence of tree-level flavour-changing
neutral currents. In addition to the usual fermion masses and mixings, the
aligned Yukawa structure only contains three complex parameters, which are
potential new sources of CP violation. For particular values of these three
parameters all known specific implementations of the model based on discrete
Z_2 symmetries are recovered. One of the most distinctive features of the
two-Higgs-doublet model is the presence of a charged scalar. In this work, we
discuss its main phenomenological consequences in flavour-changing processes at
low energies and derive the corresponding constraints on the parameters of the
aligned two-Higgs-doublet model.Comment: 46 pages, 19 figures. Version accepted for publication in JHEP.
References added. Discussion slightly extended. Conclusions unchange
Physical constraints on a class of two-Higgs doublet models with FCNC at tree level
We analyse the constraints and some of the phenomenological implications of a class of two Higgs doublet models where there are flavour-changing neutral currents (FCNC) at tree level but the potentially dangerous FCNC couplings are suppressed by small entries of the CKM matrix V. This class of models have the remarkable feature that, as a result of a discrete symmetry of the Lagrangian, the FCNC couplings are entirely fixed in the quark sector by V and the ratio v(2)/v(1) of the vevs of the neutral Higgs. The discrete symmetry is extended to the leptonic sector, so that there are FCNC in the leptonic sector with their flavour structure fixed by the leptonic mixing matrix. We analyse a large number of processes, including decays mediated by charged Higgs at tree level, processes involving FCNC at tree level, as well as loop induced processes. We show that in this class of models one has new physical scalars beyond the standard Higgs boson, with masses reachable at the next round of experiments
The C2HDM revisited
The complex two-Higgs doublet model is one of the simplest ways to extend the
scalar sector of the Standard Model to include a new source of CP-violation.
The model has been used as a benchmark model to search for CP-violation at the
LHC and as a possible explanation for the matter-antimatter asymmetry of the
Universe. In this work, we re-analyse in full detail the softly broken
symmetric complex two-Higgs doublet model (C2HDM). We provide
the code C2HDM_HDECAY implementing the C2HDM in the well-known HDECAY program
which calculates the decay widths including the state-of-the-art higher order
QCD corrections and the relevant off-shell decays. Using C2HDM_HDECAY together
with the most relevant theoretical and experimental constraints, including
electric dipole moments (EDMs), we review the parameter space of the model and
discuss its phenomenology. In particular, we find cases where large CP-odd
couplings to fermions are still allowed and provide benchmark points for these
scenarios. We examine the prospects of discovering CP-violation at the LHC and
show how theoretically motivated measures of CP-violation correlate with
observables.The work of D.F., J.C.R. and J.P.S. is supported in part by the Portuguese Fundacao para a Ciencia e Tecnologia (FCT) under contracts CERN/FIS-NUC/0010/2015 and UID/FIS/00777/2013. MM acknowledges financial support from the DFG project "Precision Calculations in the Higgs Sector - Paving the Way to the New Physics Landscape" (ID: MU 3138/1-1).info:eu-repo/semantics/publishedVersio
The Higgs vacuum uplifted: revisiting the electroweak phase transition with a second Higgs doublet
The existence of a second Higgs doublet in Nature could lead to a cosmological first order electroweak phase transition and explain the origin of the matter-antimatter asymmetry in the Universe. We explore the parameter space of such a two-Higgs-doublet-model and show that a first order electroweak phase transition strongly correlates with a significant uplifting of the Higgs vacuum w.r.t. its Standard Model value. We then obtain the spectrum and properties of the new scalars H0, A0 and H± that signal such a phase transition, showing that the decay A0 → H0Z at the LHC and a sizable deviation in the Higgs self-coupling λhhh from its SM value are sensitive indicators of a strongly first order electroweak phase transition in the 2HDM