New decay modes of heavy Higgs bosons in a two Higgs doublet model with vectorlike leptons

Journal of High Energy Physics, May 2016

In models with extended Higgs sector and additional matter fields, the decay modes of heavy Higgs bosons can be dominated by cascade decays through the new fermions rendering present search strategies ineffective. We investigate new decay topologies of heavy neutral Higgses in two Higgs doublet model with vectorlike leptons. We also discus constraints from existing searches and discovery prospects. Among the most interesting signatures are monojet, mono Z, mono Higgs, and Z and Higgs bosons produced with a pair of charged leptons.

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New decay modes of heavy Higgs bosons in a two Higgs doublet model with vectorlike leptons

Accepted: May New decay modes of heavy Higgs bosons in a two Higgs doublet model with vectorlike leptons Radovan Derm sek 0 1 2 3 Enrico Lunghi 0 1 3 Seodong Shin 0 1 3 0 Seoul National University , 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea 1 727 E. Third St. , Bloomington, IN, 47405 U.S.A 2 Department of Physics and Astronomy and Center for Theoretical Physics 3 Physics Department, Indiana University , USA In models with extended Higgs sector and additional matter elds, the decay modes of heavy Higgs bosons can be dominated by cascade decays through the new fermions rendering present search strategies ine ective. heavy neutral Higgses in two Higgs doublet model with vectorlike leptons. We also discuss constraints from existing searches and discovery prospects. Among the most interesting signatures are monojet, mono Z, mono Higgs, and Z and Higgs bosons produced with a pair of charged leptons. Beyond Standard Model; Higgs Physics - 2.1 2.2 3.1 3.2 3.3 3.4 3.5 1 Introduction 3 Signatures H ! W H ! Z H ! Z H ! h H ! h 4 Conclusions 1 Introduction 2 Two Higgs doublet model with vectorlike leptons Branching ratios of the heavy Higgs boson Branching ratios of the lightest neutral and charged leptons and H ! e4 , where e4 and 4 are the lightest new charged and neutral leptons. These decay modes can be very large when the mass of the heavy Higgs boson is below the tt threshold and the light Higgs boson (h) is SM-like so that H ! ZZ; W W are suppressed or not present. In this case, avor changing decays H ! 4 or H ! e4 compete only with H ! bb and for su ciently heavy H also with H ! hh. Subsequent decay modes of e4 and 4: e4 ! W , e4 ! Z , e4 ! h and 4 ! W , 4 ! Z , 4 ! h lead to the following 6 decay chains of the heavy Higgs boson: H ! H ! e4 4 ν4 νμ νμ μ e4 W H (b) H (e) νμ ν4 νμ e4 μ μ Z Z H (c) H (f) νμ ν4 νμ e4 μ μ h h are kinematically open. Moreover, the nal states are the same as in pair production of vectorlike leptons. We will not consider these possibilities here. Finally, although we focus on the second family of SM leptons in nal states, the modi cation for a di erent family of leptons or quarks is straightforward. We show that in a large range of the parameter space branching ratios for the decay modes (1.1) and (1.2) can be sizable or even dominant while satisfying constraints from searches for heavy Higgs bosons, pair production of vectorlike leptons [2] obtained from searches for anomalous production of multilepton events and constraints from precision electroweak (EW) observables [ 3 ]. Since the Higgs production cross section can be very large, for example the cross section for a 200 GeV Higgs boson at 8 TeV (13 TeV) LHC for tan = 1 is 7pb (18pb) [4], the nal states above can be produced in large numbers. Thus searching for these processes could lead to the simultaneous discovery of a new Higgs boson and a new lepton if they exist. Some of the decay modes in gure 1 also allow for full reconstruction of the masses of both new particles in the decay chain. The nal states of the processes (1.1–) a2n–d (1.2) are the same as nal states of pp ! W W; ZZ; Zh production or H ! W W; ZZ decays with one of the gauge bosons decaying into second generation of leptons. Since searching for leptons in nal states is typically advantageous, our processes contribute to a variety of existing searches. Even searches for processes with fairly large cross sections can be signi cantly a ected. For example, the contribution of pp ! H ! 4 to pp ! W W can be close to current limits while satisfying the constraints from H ! W W . This has been recently studied in ref. [1] { 2 { in the two Higgs doublet model we consider here, and also in a more model independent way in ref. [5]. However, the processes with tiny SM rates would be the best place to look for this scenario and here we will focus on such signatures. Examples of almost background free processes include H ! h and H ! h with h ! . Vectorlike quarks and leptons near the electroweak scale provide a very rich phenomenology. For example, similar processes to (1.1) and (1.2) involving SM-like Higgs boson decaying into 2`2 or 4` through a new lepton were previously studied in ref. [6] and the 4` case also in ref. [7]. An explanation of the muon g 2 anomaly with vectorlike leptons was studied in [8, 9]. Vectorlike quarks and possibly Z0 o er possibilities to explain anomalies in Z-pole observables [10{13]. Extensions of the SM with complete vectorlike families HJEP05(216)48 were considered to provide an understanding of values of gauge couplings from IR xed point behavior and threshold e ects of vectorlike fermions [14, 15]. Vectorlike quarks and leptons were also considered in supersymmetric framework, see for example refs. [16{21]. Further discussion and references can be found in a recent review [22]. This paper is organized as follows. In section 2 we brie y summarize the model, discuss constraints and present result for branching ratios of the heavy Higgs boson and new leptons. In section 3 we discuss relevant existing searches and the most promising search strategies for each of the six processes. We summarize and present concluding remarks in section 4. 2 Two Higgs doublet model with vectorlike leptons In ref. [1] we introduced an explicit model consisting of a type-II two Higgs doublet model augmented by vectorlike pairs of new leptons: SU(2) doublets LL;R, SU(2) singlets EL;R and SM singlets NL;R, where the LL and ER have the same hypercharges as leptons in the SM. In order to avoid dangerous rates of lepton avor changing transitions between the light leptons we further assume that the new leptons mix only with one family of SM leptons and we consider the mixing with the second family as an example. This can be achieved by requiring that the individual lepton number is an approximate symmetry (violated only by light neutrino masses). With these assumptions, one can write the most general renormalizable Lagrangian containing Yukawa and mass terms for the second generation of SM leptons and new vectorlike leptons. After spontaneous symmetry breaking, Hu0 = vu and H0 d = vd with right-handed elds ( R; LR; ER)T on the right [9], v = 174 GeV (we also de ne tan vu=vd), the model can be summarized by mass matrices in the charged lepton sector, with left-handed elds ( L; LL ; EL) on the left and qvu2 + vd2 = 0y vd 0 E vd1 vd CA ; 0 vd ME (2.1) and in the neutral lepton sector, with left-handed elds ( ; L0L; NL) on the left and right{ 3 { handed elds ( R = 0; L0R; NR)T on the right [1], vu CA : 0 vu MN (2.2) (2.3) (2.4) (2.5) (2.6) (2.7) (2.8) The superscripts on vectorlike elds represent the charged and the neutral components (we inserted R = 0 for the right-handed neutrino which is absent in our framework in order to keep the mass matrix 3 3 in complete analogy with the charged sector). The usual SM Yukawa coupling of the muon is denoted by y , the Yukawa couplings to Hd are denoted by various s, the Yukawa couplings to Hu are denoted by various s and nally the explicit mass terms for vectorlike leptons are given by ML;E;N . Note that explicit mass terms between SM and vectorlike elds (i.e. LLR and EL R) can be rotated away. These mass matrices can be diagonalized by bi-unitary transformations and we label the two new charged and neutral mass eigenstates by e4; e5 and 4 ; 5 respectively: ULy MeUR = diag (m ; me4 ; me5 ) ; VLyM VR = diag (0; m 4 ; m 5 ) : Since SU(2) singlets mix with SU(2) doublets, the couplings of all involved particles to the Z, W and Higgs bosons are in general modi ed. The avor conserving couplings receive corrections and avor changing couplings between the muon (or muon neutrino) and heavy leptons are generated. The relevant formulas for these couplings in terms of diagonalization matrices de ned above can be found in refs. [1, 9]. In the limit of small mixing, approximate analytic expressions for diagonalization matrices can be obtained which are often useful for understanding of numerical results. These are also given in refs. [1, 9]. 2.1 Branching ratios of the heavy Higgs boson In order to focus on decay modes (1.1) or (1.2) we either allow mixing only in the neutral sector, couplings, or only in the charged sector, couplings. We further assume that the relevant lighter new lepton, 4 or e4, is heavier that mH =2 to avoid decays into pairs of new leptons and the heavier new lepton, 5 or e5, is heavier than H. Finally, we work in the limit with the light Higgs boson being fully SM-like and thus the heavy CP even Higgs H has no direct couplings to gauge bosons. We apply these requirements on randomly generated points in the parameter space speci ed by following ranges: N ; ; or L; E ; ; tan mH 2 [130; 340] GeV ; where we focus on mH < 2mt in order to avoid H ! tt and on the small tan region where the heavy Higgs production cross section is the largest. { 4 { We impose constraints from precision EW data related to the muon and muon neutrino: muon lifetime, Z-pole observables (Z partial width to , the invisible width, forwardbackward asymmetry, left-right asymmetry) and the W partial width; constraints from oblique corrections, namely from S and T parameters; and the LEP limit on the mass of a new charged lepton, 105 GeV. These constraints are obtained from ref. [ 3 ]. We also impose constraints on pair production of vectorlike leptons [2] obtained from searches for + anomalous production of multilepton events.1 In addition to constraints on new leptons we also impose constraints from searches for new Higgses: H ! W W [24, 25] and H ! [26]. Although the processes in (1.1) or (1.2) do not contribute to H ! W W directly, they contribute to the same nal states as obtained from decays of W bosons. In applying the constraints from H ! W W we follow the analyses presented in refs. [5, 27]. We implement the cut-based analysis using the data for e e nal state in [24, 25] but the results using would be similar. Since our H has no direct coupling to the W boson, it is only the top quark and new charged leptons in loops that contribute to H ! . The top quark contribution to H ! and thus this process is highly constraining the parameter space at very small tan . In the scales as cot2 usual two Higgs doublet model this was studied in ref. [28]. However, new charged leptons can enhance or partially cancel the contribution from the top quark depending on the signs of the new Yukawa couplings. Thus the allowed range of tan is expected to extend to lower values compared to the usual two Higgs doublet model. Since new leptons also couple to the SM-like Higgs boson, the constraints from h ! at present still allow for a sizable new physics contribution [29]. have to be also satis ed. These Results of the scan in the case of mixing in the neutral lepton sector, allowing for and h ! H ! 4 , are depicted in gure 2 in various planes of relevant branching ratios and tan . The dark colored points satisfy all the limits summarized above. The gray points satisfy all the limits on new leptons but are excluded by H ! ; W W and h ! light colors represent the points which are phenomenologically viable and satisfy H ! . Finally, the limits only if mixing in the charged lepton sector is simultaneously allowed which partially cancels the contribution from the top quark. In this case, for simplicity, we allow L and E to mix but not with the muon and we conservatively extend the ranges for and to [ 1; 1]. We clearly see the lower bound on tan ' 0:55. Without the mixing in the charged sector the lower limit on tan moves to about 0.7. Similarly, results of the scan in the case of mixing only in the charged lepton sector, allowing for H ! e4 , are given in gure 3 in the same planes and color scheme. In this case, the tan dependence is not so signi cant because the new Yukawa coupling inducing in the same way as the bb coupling. The lowest possible value H ! e4 scales with tan of tan is 0.7 as it was in the H ! 4 [ 1; 1], as indicated by light colors, only allows tan & 0:6. case. Even extending the ranges for and to For completeness we plot the same points in the plane of Higgs branching ratios for H ! 4 and H ! e4 versus the Higgs mass in gure 4. Finally, although we focussed on the CP even Higgs, the results for CP odd Higgs would be qualitatively similar. 1For the discussion of prospects of multilepton searches for vectorlike leptons in the case of mixing with the 3rd generation of SM leptons, see ref. [23]. { 5 { points) additionally satisfy the bounds from H ! allowed. Various colors indicate di erent ranges of mH and BR(H ! hh) speci ed in the legend. 2.2 Branching ratios of the lightest neutral and charged leptons The branching ratios of new lightest neutral and charged leptons decaying through Z and W bosons are shown in gure 5. Although not explicitly shown, the remaining branching ratio of the decay through the SM Higgs boson can be easily read out since only three decay modes are possible. In the left panels only constraints from EW precision data and direct searches are imposed. In the right panels we include the impact of constraints from searches for anomalous production of multilepton events [2]. In these plots, the colors indicate the doublet fractions of 4 or e4. The blue, cyan, magenta, and red points have doublet fractions in the ranges [95,100]%, [50,95]%, [5, 50]%, and [0, 5]% respectively. The doublet fraction the a (a = 4; 5) is de ned as 1 h 2 (VLy)a2 i2 h + (VLy)a4 i2 h + (VRy)a4 i2 (2.9) and the doublet fraction of ea (a = 4; 5) is obtained by replacing the VL;R matrices by UL;R matrices in the formula above. Singlet fractions are given by 1 | (doublet fraction). { 6 { decay. Color coding is the same as in gure 2. We inserted the sub gure extending tan and do not even allow a doublet-like charged lepton in the mass range considered. Note however that in the case of charged leptons with large BR(e4 ! W ) the constraints come from the pair production of 4 that accompanies doublet-like e4 or from e4 4 production; the e4e4 pair production is not directly constrained by multilepton searches. Without mixing in the neutral sector, BR( 4 ! W ) = 1 and this decay mode is highly constrained [2]. Allowing simultaneously full mixing in both charged and neutral sectors would relax this constraint somewhat. The main features of plots in gure 5 can be understood from analytic formulas for couplings that can be obtained in the limit of small mixing [1]. For singlet-like e4 or 4 the avor changing couplings to W and Z have, in the leading order, the same dependence on parameters controlling the mixing. Thus this dependence disappears in the ratio and we nd this slope. (e4 ! W )= (e4 ! Z ) to be approximately 2:1 leading to the red bands with For doublet-like 4, the avor changing couplings to A = W; Z; h have the form N ( A + A ) where A and A are functions of tan , MN and ML. This implies immediately that, for xed tan , MN and ML, a scan over the three couplings N , { 7 { axis of these ellipses is almost horizontal for ML & v; for smaller ML the ellipses collapse onto the diagonal, which corresponds to BR( 4 ! h ) gures 3, 4 and 7 of ref. [1] for various choices of m 4 . Finally, for the doublet-like e4, there are two couplings, L and E , connecting the muon to vectorlike fermions and thus controlling the overall strengths of avor changing couplings to W , Z, and h. In result, there is signi cantly more freedom and generating couplings to W , Z, and h are less correlated. In order to illuminate more subtle features of the scenario, we plot the same points in the planes of branching ratios versus the masses of 4 and e4 in gure 6. 0. This behavior can be seen in 3 Signatures In this section we discuss each of the novel heavy Higgs decay modes with details of the main features of each channel, of existing experimental searches to which these new process contribute, and of possible new searches. Considering the variety of possible nal states, detailed Monte Carlo studies of these signatures are beyond the scope of this paper. For estimates of rates of various processes we will use, as a reference point, the production cross section of a 200 GeV Higgs boson at 8 TeV LHC for tan = 1 which is 7pb. The corresponding cross section at 13 TeV LHC is 18pb, and for di erent values of tan these numbers should be divided by tan2 . Furthermore, we will assume BR(H ! 4 ) or BR(H ! e4 ) to be 50% and branching ratios of 4 or e4 relevant for a given process to be 100%. These branching ratios are close to the upper possible values allowed as we saw in the previous section. Note however that after imposing all constraints e4 ! Z branching ratios above 40%, while possible, are di cult to achieve. 3.1 H The diagrams in gures 1a and 1d yield the W nal state. A detailed study of these topologies with W ! ` (` = e; ) has been presented in refs. [1, 5], where with focus on contributions to the existing pp ! W W and pp ! H ! W W measurements. { 8 { straints from precision EW data and in the right plots also by searches for anomalous production of multilepton events. The blue, cyan, magenta, and red points have doublet fractions in the ranges [95,100]%, [50,95]%, [5, 50]%, and [0, 5]% respectively. A crucial feature of the process in gure 1a is that the intermediate 4 ! W decay, with a hadronically decaying W , allows the kinematic reconstruction of the neutral fermion 4. Experimental studies of this mode can be a ected by searches for semileptonic decays of a heavy Higgs (H ! W W ! ` jj) which have been presented in refs. [30{34]. In these searches, the assumption that the observed missing transverse momentum is caused by a neutrino emitted in the W decay, is used to reconstruct the complete four-momentum of the neutrino; thus allowing the reconstruction of the Higgs mass (m2H = (p` + p + pjj )2). The e ciency loss due to this reconstruction procedure is about 50%. However, in our case, the neutrino does not originate from a W and this procedure does not reconstruct the correct Higgs mass. An alternative approach is to consider the transverse mass mT = (E= 2T that is expected to have an edge at mH . Moreover the pT distribution of the neutrino is T p=2 )1=2 expected to be di erent because the latter does not originate from a W . Finally, for Higgs masses above 200 GeV our signal is potentially enhanced, with respect to the one studied in ref. [30], by the ratio of BR(H ! 4 ! W maximal H and 4 branching ratios are taken from ! jj ) . 0:5 1 0:7 0:35 (where the gures 4 and 6) to BR(H ! W W ! jj ) = 2 0:74 0:7 0:1 ' 0:1 (where we included a combinatoric factor of 2 for the { 9 { new lepton mass. H ! 3.2 (with a leptonic tau) and H ! and is constrained by searches for The diagram in gure 1b leads to the Z nal state. For Z ! our process contributes to the jet plus missing ET signature, that is common to monojet searches for dark matter pair production or for invisible Higgs boson decays. For instance, in refs. [35, 36] the ATLAS and CMS collaborations placed upper limits on the visible cross section de ned as the product of cross section, Monte Carlo acceptances and detector e ciencies, i.e. the observed number of events divided by the integrated luminosity. Requiring E= T > 150 GeV, the ATLAS limit is 726 fb which is larger than the typical values that we can obtain. For our reference point, even before requiring an extra high-pT jet and including acceptances and detector e ciencies, the total cross section is (pp ! H) BR(H ! 4 ! Z ` `) . (7 pb) 0:5 1 0:2 ! ``, our signal contributes to the pp ! ZZ ! `` measurement [37] and to searches for H ! ZZ ! `` [38], mono-Z with missing energy, Z + E= T [39, 40] and Zh(H) ! `` + E= T [41]. For instance, the CMS search for Z + E= T [40] nds a limit on the visible cross section (for various E= T cuts) at the 1{2 fb level; in our case the mH = 200 GeV total cross section is up to (pp ! H) 210 fb, before acceptances and e ciencies. Therefore, this channel is likely to o er the strongest constraint. The hadronic Z ! jj mode is less clean and has been studied in the context of the ! ! H ! ZZ ! jj the Higgs, PH = pZ + p 1 + p 2 , and charged vectorlike lepton, Pe4 = pZ + p 1 (up to a dilution due to picking the wrong muon). The most promising channel is H ! Z ! `` . A recent ATLAS search for e4 ! Z` ! 3` with the e4 produced with another vectorlike lepton in a Drell-Yan process is presented in ref. [42] where the visible cross section into 4`, 3` + jj and 3` nal states is found to be smaller than 1 fb. For our reference point, we obtain underlying process and kinematics with respect to vectorlike leptons pair production, we expect our acceptance for the ATLAS search to be somewhat smaller than the quoted (20{50)% acceptance. In addition, one could additionally search for a fourth lepton and require one lepton pair to form a Z while imposing a Z veto on the second pair thus suppressing ZZ backgrounds; the four leptons invariant mass is also expected to peak at the heavy Higgs mass. In ref. [43], CMS presented a study of a heavy SM-like Higgs decaying to ZZ and found that for Higgs masses smaller than about 500 GeV the 95% upper limit on the total cross section into four leptons is 0:1 this corresponds to about 0:1 takes into account that only the 4 and 2e2 nal states should be included), which has to be compared to our reference cross section of about 210 fb discussed above. Since these searches require two on-shell Z bosons compared to the single Z in our signal, we expect the Monte Carlo level acceptances for this process to be very small. A similar argument applies to pp ! ZZ ! 4` [44]. However, one can again impose a Z veto on two of the charged leptons, almost completely removing the SM background. The Z ! jj mode is also interesting but it yields experimental bounds that are roughly an order of magnitude weaker than in the di-lepton case [43]. The invisible Z channel is problematic because it leads to a dimuon plus missing energy nal state in which the two muons do not reconstruct a Z. This nal state would also contribute to a W W search. This mode stems from the diagram in gure 1f and leads to large contributions to several very promising nal states: ( )h , (ZZ )h ! 6`, (W W )h ! 4` + MET and (bb)h (the subscript indicates the particles whose invariant mass reconstruct the SM Higgs). Standard Model backgrounds to the rst three modes are essentially absent making them golden channels to discover this process. In fact, the dominant SM backgrounds are pp ! h( ; Z); moreover, the latter can be further suppressed by requiring the Z to be virtual by vetoing di-leptons with invariant mass close to mZ . For our reference point we nd almost zero background) could be already present in the existing data set. BR(H ! e4 BR(H ! e4 ! h ! h ! ! ZZ ) . ! 0:4 fb. A large number of expected events (over 3.5 The SM Higgs plus missing energy signal, depicted in gure 1c, is also very interesting because it overlaps with dark matter searches. The clear golden mode is the ( )h + E= T nal state. A search for this signal has been performed in ref. [45] where a small excess of 3 events has been observed over (essentially) no background. In fact, the pp ! Zh ! 0.2 fb and, with a 10% acceptance, leads to about 0.5 events at 20 fb 1. The cross section for our reference point is about 0:5 1 10:5 fb. Assuming that our signal acceptance is identical to the acceptance used in this search (10%), we expect about 21 events with 20 fb 1 of integrated luminosity. Future updates of this search will certainly place interesting constraints on our process has a total cross section of about model. In ref. [46] the pp ! (Z ! bb)(h ! invisible) ! bb + E= T was studied. Interestingly a small excess of 20 events is observed for mbb 125 GeV that would be compatible with our signal with h ! bb. For our reference point and considering the h ! bb decay of the SM Higgs we get a cross section of up to 2:0 pb. This is further reduced by the b tagging e ciency (0:72 = 0:5) and by the acceptance. In ref. [47], CMS presents a similar study but the di-jet invariant mass distribution after b-tagging is not presented; hence we do not know whether an excess at mbb = 125 GeV is seen. In refs. [48] ATLAS performed a dedicated search for pp ! (h ! bb)Z=W . Events are classi ed according to the number of leptons in the nal state: Z ! (0-leptons), W ! ` (1-lepton), Z ! `` (2-leptons). The 0-lepton channel shares the nal state with the search presented in ref. [46] (that we discussed above) and a small excess compatible with the one observed in that search has also been observed. A similar search has been performed by CMS in ref. [49]. A search for h ! bb produced in association with dark matter has been presented in ref. [50] where, unfortunately, the bb invariant mass distribution is not shown. Other interesting nal states are pp ! h + E= T ! ( modes are similar to the corresponding SM pp ! h ! ( ; ; W W ; ZZ ) + E= T . These ; ; W W ; ZZ ) ones, albeit with sizable extra missing energy that further reduces all backgrounds. 4 Conclusions In two Higgs doublet model type II with vectorlike leptons, the decay modes of heavy Higgs bosons can be dominated by cascade decays through the new leptons into W , Z and Higgs bosons and SM leptons. These processes are listed in eqs. (1.1) and (1.2) and corresponding Feynman diagrams are in gure 1. After applying constraints from precision electroweak observables, searches for heavy Higgs bosons and constraints on pair production of vectorlike leptons obtained from searches for anomalous production of multilepton events we found that branching ratios of H ! 4 and H ! e4 , where e4 and 4 are the lightest new charged and neutral leptons can be as large as 50%. These decay modes are especially relevant below the tt threshold and when the light Higgs boson (h) is SM-like so that H ! ZZ; W W are suppressed or not present, competing only with H ! bb and for su ciently heavy H also with H ! hh. Furthermore, we found that each of the subsequent decay modes of e4 and 4: e4 ! W providing many possible search opportunities. Among the most interesting signatures are monojet, mono Z, mono Higgs, and Z and Higgs bosons produced with a pair of charged leptons. Some of these signatures are almost background free. Combining this with potentially large production cross section for these processes presents great discover prospects at the LHC. Acknowledgments The work of RD and EL was supported in part by the U.S. Department of Energy under grant number DE-SC0010120. RD was supported in part by the Ministry of Science, ICT and Planning (MSIP), South Korea, through the Brain Pool Program. RD also thanks the Galileo Galilei Institute for Theoretical Physics for hospitality and support during part of this work. Open Access. 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Radovan Dermíšek, Enrico Lunghi, Seodong Shin. New decay modes of heavy Higgs bosons in a two Higgs doublet model with vectorlike leptons, Journal of High Energy Physics, 2016, 148, DOI: 10.1007/JHEP05(2016)148