High scale impact in alignment and decoupling in two-Higgs doublet models

The two-Higgs doublet model (2HDM) provides an excellent benchmark to study physics beyond the Standard Model (SM). In this work we discuss how the behaviour of the model at high energy scales causes it to have a scalar with properties very similar to those of the SM -- which means the 2HDM can be seen to naturally favor a decoupling or alignment limit. For a type II 2HDM, we show that requiring the model to be theoretically valid up to a scale of 1 TeV, by studying the renormalization group equations (RGE) of the parameters of the model, causes a significant reduction in the allowed magnitude of the quartic couplings. This, combined with $B$-physics bounds, forces the model to be naturally decoupled. As a consequence, any non-decoupling limits in type II, like the wrong-sign scenario, are excluded. On the contrary, even with the very constraining limits for the Higgs couplings from the LHC, the type I model can deviate substantially from alignment. An RGE analysis similar to that made for type II shows, however, that requiring a single scalar to be heavier than about 500 GeV would be sufficient for the model to be decoupled. Finally, we show that not only a 2HDM where the lightest of the CP-even scalars is the 125 GeV one does not require new physics to be stable up to the Planck scale but this is also true when the heavy CP-even Higgs is the 125 GeV and the theory has no decoupling limit for the type I model.Comment: 28 pages, 19 figure

Implications of the LHC two-photon signal for two-Higgs-doublet models

We study the implications for Two Higgs Doublet Models of the recent announcement at the LHC giving a tantalizing hint for a Higgs boson of mass 125 GeV decaying into two photons. We require that the experimental result be within a factor of two of the theoretical Standard Model prediction, and analyze the type I and type II models as well as the lepton-specific and flipped models, subject to this requirement. It is assumed that there is no new physics other than two Higgs doublets. In all of the models, we display the allowed region of parameter space taking the recent LHC announcement at face value, and we analyze the $W^+W^-$, $ZZ$, $\bar{b}b$ and $\tau^+\tau^-$ expectations in these allowed regions. Throughout the entire range of parameter space allowed by the $\gamma\gamma$ constraint, the number of events for Higgs decays into $WW$, $ZZ$ and $b \bar b$ are not changed from the Standard Model by more than a factor of two. In contrast, in the Lepton Specific model, decays to $\tau^+ \tau^-$ are very sensitive across the entire $\gamma \gamma$-allowed region.Comment: Latex, 6 pages, 4 figures; v2 - added 2 reference

Wrong sign and symmetric limits and non-decoupling in 2HDMs

We analyse the possibility that, in two Higgs doublet models, one or more of the Higgs couplings to fermions or to gauge bosons change sign, relative to the respective Higgs Standard Model couplings. Possible sign changes in the coupling of a neutral scalar to charged ones are also discussed. These \textit{wrong signs} can have important physical consequences, manifesting themselves in Higgs production via gluon fusion or Higgs decay into two gluons or into two photons. We consider all possible wrong sign scenarios, and also the \textit{symmetric limit}, in all possible Yukawa implementations of the two Higgs doublet model, in two different possibilities: the observed Higgs boson is the lightest CP-even scalar, or the heaviest one. We also analyse thoroughly the impact of the currently available LHC data on such scenarios. With all 8 TeV data analysed, all wrong sign scenarios are allowed in all Yukawa types, even at the 1$\sigma$ level. However, we will show that B-physics constraints are crucial in excluding the possibility of wrong sign scenarios in the case where $\tan \beta$ is below 1. We will also discuss the future prospects for probing the wrong sign scenarios at the next LHC run. Finally we will present a scenario where the alignment limit could be excluded due to non-decoupling in the case where the heavy CP-even Higgs is the one discovered at the LHC.Comment: 20 pages, 15 figure

Mass-degenerate Higgs bosons at 125 GeV in the Two-Higgs-Doublet Model

The analysis of the Higgs boson data by the ATLAS and CMS Collaborations appears to exhibit an excess of h --> gamma\gamma events above the Standard Model (SM) expectations; whereas no significant excess is observed in h --> ZZ* --> {four lepton} events, albeit with large statistical uncertainty due to the small data sample. These results (assuming they persist with further data) could be explained by a pair of nearly mass-degenerate scalars, one of which is a SM-like Higgs boson and the other is a scalar with suppressed couplings to W+W- and ZZ. In the two Higgs doublet model, the observed \gamma\gamma and ZZ* --> {four lepton} data can be reproduced by an approximately degenerate CP-even (h) and CP-odd (A) Higgs boson for values of \sin(\beta-\alpha) near unity and 0.7 < \tan\beta < 1. An enhanced \gamma\gamma signal can also arise in cases where m_h ~ m_H, m_H ~ m_A, or m_h ~ m_H ~ m_A. Since the ZZ* --> {four lepton} signal derives primarily from a SM-like Higgs boson whereas the \gamma\gamma signal receives contributions from two (or more) nearly mass-degenerate states, one would expect a slightly different invariant mass peak in the ZZ* --> {four lepton} and \gamma\gamma channels. The phenomenological consequences of such models can be tested with additional Higgs data that will be collected at the LHC in the near future.Comment: 18 pages, 19 pdf figures, v2: references added, v3&v4: added refs and explanation

Probing wrong-sign Yukawa couplings at the LHC and a future linear collider

We consider the two-Higgs-doublet model as a framework in which to evaluate the viability of scenarios in which the sign of the coupling of the observed Higgs boson to down-type fermions (in particular, $b$-quark pairs) is opposite to that of the Standard Model (SM), while at the same time all other tree-level couplings are close to the SM values. We show that, whereas such a scenario is consistent with current LHC observations, both future running at the LHC and a future $e^+ e^-$ linear collider could determine the sign of the Higgs coupling to $b$-quark pairs. Discrimination is possible for two reasons. First, the interference between the $b$-quark and the $t$-quark loop contributions to the $ggh$ coupling changes sign. Second, the charged-Higgs loop contribution to the $\gamma \gamma h$ coupling is large and fairly constant up to the largest charged-Higgs mass allowed by tree-level unitarity bounds when the $b$-quark Yukawa coupling has the opposite sign from that of the SM (the change in sign of the interference terms between the $b$-quark loop and the $W$ and $t$ loops having negligible impact).Comment: 28 pages, 21 figure

Assessing patterns of geographic dispersal of Gelidium sesquipedale (Rhodophyta) through RAPD differentiation of populations

Randomly amplified polymorphic DNAs (RAPDs) of bulked genomic DNA samples were used to analyse the genetic differentiation of Gelidium sesquipedale populations. They reflect the pat terns of gene flow, which in turn depend on the dispersal mechanisms of the species and on near-shore ocean currents. Fourteen populations were sampled from northern France to Morocco, covering the geographical distribution of the species. A single bulk DNA sample (from 15 individuals) was used in each population, under the assumption that the resulting patterns represent the populations' most common genetic features. To test this, we investigated the genetic variability among 5 bulk samples within a single population. Genetic distances among bulks were very low (average = 0.065) and were signifi- cantly lower than those observed between geographically separated populations (average = 0.241). Neighbour-joining analysis of the distance matrix of populations separated a well-supported group including populations of northern Spain and of northern France, and a less-supported group containing populations of northern Portugal. Multidimensional scaling of the genetic distance matrix revealed 2 isolated populations, Sao Rafael in southern Portugal and Algeciras in southern Spain. These patterns of genetic differentiation are discussed under the available data on the near-shore ocean currents. Results suggest that the genetic differentiation of G. sesquipedale populations may be used as a biological tracer of prevailing flows and barriers of the near-shore currents. A positive correlation between geographical and genetic distances of G. sesquipedale populations along the species geographical dis tribution was found, suggesting that a continuous transport of detached fronds and their reattachment to new substrate must be an effective dispersal mechanism of the species, sustaining the gene flow among populations

Response of key stress-related genes of the seagrass Posidonia oceanica in the vicinity of submarine volcanic vents

Submarine volcanic vents are being used as natural laboratories to assess the effects of increased ocean acidity and carbon dioxide (CO2) concentration on marine organisms and communities. However, in the vicinity of volcanic vents other factors in addition to CO2, which is the main gaseous component of the emissions, may directly or indirectly confound the biota responses to high CO2. Here we used for the first time the expression of antioxidant and stress-related genes of the seagrass Posidonia oceanica to assess the stress levels of the species. Our hypothesis is that unknown factors are causing metabolic stress that may confound the putative effects attributed to CO2 enrichment only. We analyzed the expression of 35 antioxidant and stress-related genes of P. oceanica in the vicinity of submerged volcanic vents located in the islands of Ischia and Panarea, Italy, and compared them with those from control sites away from the influence of vents. Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) was used to characterize gene expression patterns. Fifty-one percent of genes analyzed showed significant expression changes. Metal detoxification genes were mostly down-regulated in relation to controls at both Ischia and Panarea, indicating that P. oceanica does not increase the synthesis of heavy metal detoxification proteins in response to the environmental conditions present at the two vents. The up-regulation of genes involved in the free radical detoxification response (e.g., CAPX, SODCP and GR) indicates that, in contrast with Ischia, P. oceanica at the Panarea site faces stressors that result in the production of reactive oxygen species, triggering antioxidant responses. In addition, heat shock proteins were also activated at Panarea and not at Ischia. These proteins are activated to adjust stress-accumulated misfolded proteins and prevent their aggregation as a response to some stressors, not necessarily high temperature. This is the first study analyzing the expression of target genes in marine plants living near natural CO2 vents. Our results call for contention to the general claim of seagrasses as "winners" in a high-CO2 world, based on observations near volcanic vents. Careful consideration of factors that are at play in natural vents sites other than CO2 and acidification is required. This study also constitutes a first step for using stress-related genes as indicators of environmental pressures in a changing ocean.project HighGrass "High-CO2 effects on seagrass photosynthetic ecophysiology" [PTDC/MAREST/3687/2012]; MIUR Italian flagship project RITMARE; ESF COST Action "Seagrass Productivity: from genes to ecosystem management

Could the LHC two-photon signal correspond to the heavier scalar in two-Higgs-doublet models?

LHC has reported tantalizing hints for a Higgs boson of mass 125 GeV decaying into two photons. We focus on two-Higgs-doublet Models, and study the interesting possibility that the heavier scalar (H) has been seen, with the lightest scalar (h) having thus far escaped detection. Non-observation of h at LEP severely constrains the parameter-space of two-Higgs-doublet models. We analyze cases where the decay H --> h h is kinematically allowed, and cases where it is not, in the context of type I, type II, lepton-specific, and flipped models.Comment: 9 pages, pdf figure