A new avenue to charged Higgs discovery in multi-Higgs models

Journal of High Energy Physics, Apr 2014

Current searches for the charged Higgs at the LHC focus only on the τν, cs, and tb final states. Instead, we consider the process pp → Φ → W ± H ∓ → W + W − A where Φ is a heavy neutral Higgs boson, H ± is a charged Higgs boson, and A is a light Higgs boson, with mass either below or above the \( b\overline{b} \) threshold. The cross-section for this process is typically large when kinematically open since H ± → W ± A can be the dominant decay mode of the charged Higgs. The final state we consider has two leptons and missing energy from the doubly leptonic decay of the W + W − and possibly additional jets; it is therefore constrained by existing SM Higgs searches in the W + W − channel. We extract these constraints on the cross-section for this process as a function of the masses of the particles involved. We also apply our results specifically to a type-II two Higgs doublet model with an extra Standard-Model-singlet and obtain new and powerful constraints on m H ± and tan β. We point out that a slightly modified version of this search, with more dedicated cuts, could be used to possibly discover the charged Higgs, either with existing data or in the future.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://link.springer.com/content/pdf/10.1007%2FJHEP04%282014%29140.pdf

A new avenue to charged Higgs discovery in multi-Higgs models

Radovan Dermsek 1 Jonathan P. Hall 1 Enrico Lunghi 1 Seodong Shin 0 1 0 CTP and Department of Physics and Astronomy, Seoul National University , Seoul 151-747, Korea 1 Physics Department, Indiana University , Bloomington, IN 47405, U.S.A Current searches for the charged Higgs at the LHC focus only on the , cs, and tb final states. Instead, we consider the process pp W H W +W A where is a heavy neutral Higgs boson, H is a charged Higgs boson, and A is a light Higgs boson, with mass either below or above the bb threshold. The cross-section for this process is typically large when kinematically open since H W A can be the dominant decay mode of the charged Higgs. The final state we consider has two leptons and missing energy from the doubly leptonic decay of the W +W and possibly additional jets; it is therefore constrained by existing SM Higgs searches in the W +W channel. We extract these constraints on the cross-section for this process as a function of the masses of the particles involved. We also apply our results specifically to a type-II two Higgs doublet model with an extra Standard-Model-singlet and obtain new and powerful constraints on mH and tan . We point out that a slightly modified version of this search, with more dedicated cuts, could be used to possibly discover the charged Higgs, either with existing data or in the future. Contents 1 Introduction 2 Charged Higgs production and decay 2.1 Our example reference scenario: the type-II two Higgs doublet model with an additional SM singlet 2.2 Charged Higgs decays 2.3 Heavy neutral Higgs decays 2.4 Heavy neutral Higgs production 2.5 Total cross-sections 3 The constraint from Standard Model h W +W searches 3.1 Model independent study 3.2 The type-II 2HDM plus singlet case 4 Conclusions A Decay rates A.1 W A.2 Other AH decays A.3 Other H decays A.4 Other H decays A.5 Off-shell H B Branching ratios D CLs limits 1 Introduction The quest to unveil the mechanism responsible for the breaking of the electroweak symmetry made a huge leap forward with the recent discovery of a scalar particle whose quantum numbers and interactions appear to be compatible, albeit with large uncertainties, with those of the Standard Model (SM) Higgs boson [1, 2]. The presence of a fundamental scalar particle renders electroweak physics sensitive to arbitrarily large scales possibly present in a full theory of electroweak, strong, and gravitational interactions. Solutions to this problem usually entail the introduction of new physics just above the electroweak scale. Amongst others, hints that point to the incomplete nature of the SM are the strong empirical evidence for particle dark matter, the baryon-antibaryon asymmetry of the universe, and the pattern of neutrino masses and mixing. Even before addressing these problems it is important to realize that while the structure of currently observed gauge interactions is completely dictated by the SM gauge groups alone the pattern of electroweak symmetry breaking is not. In particular, within the context of a perturbative (Higgs) mechanism there are absolutely no symmetry reasons for introducing a single doublet (besides the empirical observation that such a choice leads directly to the rather successful Cabibbo-Kobayashi-Maskawa pattern of flavor changing and CP violation). Moreover, it is well known that supersymmetry, one of the most popular extensions of the SM that actually addresses some of the above mentioned problems, requires the introduction of a second Higgs doublet. In view of these observations it is clear that understanding how many fundamental scalars are involved in the electroweak spontaneous symmetry breaking mechanism is one of the most pressing questions we currently face. In particular, any model with at least two doublets contain at least two charged Higgs boson (H) and at least two extra neutral Higgses. In this paper we investigate a previously overlooked technique that could uncover a charged Higgs from a multi-Higgs scenario. Direct charged Higgs production in the top-bottom fusion channel typically has crosssections O(1 pb) [3] and discovery would be fairly difficult in this channel [4, 5]. If the charged Higgs mass is lower than the top mass, it is possible to bypass this problem by looking for charged Higgs bosons in top decays (t H+b), taking advantage of the very large tt production cross-section. Moreover, most current experimental studies consider only charged Higgs decays to pairs of fermions (H+ +, H+ cs, and H+ tb). Under these assumptions ATLAS and CMS were able to place bounds on BR(t H+b) at the 15 % level [69] for mH < mt.1 It is well known that the presence of a light neutral Higgs can significantly modify these conclusions. In fact, the H+ W +A decay (A being a neutral CP -even or -odd Higgs boson) can easily dominate the charged Higgs decay width if it is kinematically allowed and the A has non-vanishing mixing with one of the neutral components of a Higgs doublet. Such a light neutral pseudoscalar Higgs (A = a1) has been looked for by BaBar [11, 12] in a1 ( , ) decays and by ATLAS [13] and CMS [14] in pp a1 direct production. These bounds are easily evaded by assuming that the lightest neutral Higgs a1 has a singlet component. Under this condition, in the context of a type-II two Higgs doublet model (2HDM) with an additional singlet, the BR(t bH+) can be as large as O(10 %) for tan < 6 (tan being the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets) even for a1 as light as 8 GeV [15]. Trilepton events in tt production can be used to discover at the LHC a charged Higgs produced in top decays and decaying to W A with as little as 20 fb1 integrated luminosity at 8 TeV center of mass energy. At the LHC the charged Higgs can be alternatively produced in the decay of a heavier neutral Higgs (). Heavy neutral Higgs bosons are dominantly produced in gluon-gluon fusion (ggF) with a significant cross-section, leading to sizable charged Higgs production rates. For our somewhat model independent analysis, we ignore possible mass relations amongst the various Higgs bosons as they depend on the exact Lagrangian of the model. In 1A preliminary result of ATLAS reduces this to O(0.1%) [10]. the presence of a light Higgs A the decay H+ W +A is mostly dominant for mH+ < mt and remains comparable to H+ tb otherwise, depending on the values of the various parameters. Note that the H+ W +h1 decay (we take h1 be the particle recently discovered at the LHC) vanishes in the limit that h1 is completely SM-like. In this study we consider the process pp HW W +W A as shown in figure 1. The constraints we derive are valid for mA not too far above the bb threshold, where the decay A bb should be dominant (they are also approximately valid below this threshold, as discussed in section 3.1). At large transverse momentum of the bb pair (transverse momentum relevant for the event selection), the angular separation of the two bottom quarks is small and they are combined into a single jet.2 The final state we consider is, therefore, constrained by the standard h W W searches by CMS [21] (with 19.5 fb1 at 8 TeV and 4.9 fb1 at 7 TeV) and ATLAS [22] (with 20.7 fb1 at 8 TeV and 4.6 fb1 at 7 TeV). We use the data provided in the CMS analysis to place bounds. The impact of the experimental cuts depends on the kinematics and is controlled by the masses of the three intermediate Higgs bosons only. We therefore derive constraints on the LHC cross-section for the considered process that depend only on the masses of the relevant particles and not on other model-dependent parameters or the CP nature of the neutral Higgs bosons and A. We also apply our results to a CP conserving type-II 2HDM with an additional singlet [2326]. In this framework the lightest neutral Higgs (A) is identified with the lightest CP -odd eigenstate a1 and the heavy Higgs () with the heavy CP -odd Higgs a2. To the extent that the a2 H+W decay dominates over other decays involving Higgs bosons (and this can easily be the case) and decays to other beyond-the-Standard-Model particles our bounds depend on only ma2 , mH , ma1 , tan(), and A (the mixing angle in the CP -odd sector). A novelty in our analysis is the exclusion of parameter space regions at low tan . The 8 TeV LHC data analyzed so far allow one, using our approach, to probe only a relatively light charged Higgs (roughly below the tb threshold); in the future, regions in parameter space with a heavy charged Higgs will be accessible as well. We also consider the same scenario but with one of the CP -even states (h2) as the heavy neutral state . The types of scenario we consider and constrain can easily be consistent with constraints on the custodial symmetry breaking parameter = M W2 /(MZ2 cos2 W ). The paper is organized as follows. In section 2 we discuss the production and decay cross-section for our signal. In particular, after introducing the type-II 2HDM + singlet scenario in section 2.1 we discuss charged (H) and neutral () Higgs decays in sections 2.2 and 2.3, the gg production cross-section in section 2.4, and the total cross-section (production times branching ratios) in section 2.5. In section 3.1 we show the upper bound on the total cross-section that we extract from SM Higgs to W W searches. In section 3.2 we specialize the previous results to our reference scenario (type-II 2HDM with an additional singlet, = a2 and A = a1) and present the new exclusion bounds at low tan that we extract. Finally, in section 4, we present our conclusions. 2The ATLAS collaboration recently announced the results of a search for a similar process, where the light state A is identified with the 125 GeV CP -even Higgs, dominantly decaying into two separable bjets [16]. They consider the semileptonic decay of the W W . This was based on the suggestion put forward in ref. [17]. See also ref. [1820] which includes the non-resonant production of HW . W W W W Charged Higgs production and decay In the multi-Higgs models containing at least two SU(2) doublets, there can exist a heavy neutral Higgs () which decays into HW . The process is shown in figure 1 with the charged Higgs decaying to a light neutral Higgs A and another W boson. Looking for this process could be the first way the charged Higgs is discovered and its properties measured. This is due to the large value of (gg W H W W A) when all particles can be on-shell. In this section, we focus on showing how large such a production crosssection times the branching ratios can be, especially in the context of the type-II 2HDM + singlet scenario. In the following subsections, we show that the branching ratios of H W A and HW can be sizable when kinematics allow and the production cross-section of is roughly as large as that of the SM Higgs. Our general cross-section constraints depend only on the masses of the particles involved and will be discussed in the next section. For the specific type-II 2HDM + singlet reference scenario we can constrain physical parameters (the masses; tan ; and A, the mixing angle in the CP -odd sector) without specifying the Lagrangian in the Higgs sector and we assume no mass relations among the Higgs bosons states. Our example reference scenario: the type-II two Higgs doublet model with an additional SM singlet Considering the type-II 2HDM with one extra complex singlet scalar we define the fieldspace basis by AN = 2ImS, h cos() sin() 0 2ReHd0 vd NH = si0n() cos0() 01 2 R2Re HeSu0 svu , AH = 2 cos()ImHu0 sin()ImHd0 , where S is the SM-singlet and s is its possibly non-zero VEV and tan = vu/vd. In this convention, h interacts exactly as a SM Higgs in both gauge and Yukawa interactions; H has no coupling to the gauge boson pairs and interacts with the up-type quarks (down-type quarks and charged leptons) with couplings multiplied by cot (tan ) relative to the SM Higgs couplings. The orthogonal state to AH and AN is the Z-boson Goldstone mode. We define an orthogonal matrix U that transforms the CP -even field-space basis states into the CP -even mass eigenstates h1 U1h U1H U1N h h2 = U2h U2H U2N H h3 U3h U3H U3N N We define h1 to be the particle recently discovered at the LHC and do not demand that hi are ordered by mass. The overlap of h1 with the SM-like state h appears to be large. The mass eigenstates h2 and h3 are then approximately superpositions of H and N only. When we consider h2 to be the heavy state produced from pp collisions U2H , the overlap of h2 and H, becomes an important parameter. We define a mixing angle between the CP -odd mass eigenstates A by where a1 is defined to be the lighter state. The state a1 is identified with A in our process pp W H W W A. We mainly consider to be the other CP -odd state a2 but also consider the case where it is one of the CP -even states, defined to be h2. When the mass of a1 is below the bb threshold the constraints from the decay a1 ( , ) at BaBar and the light scalar search at the LHC (pp a1 ) lead to an upper bound on cos A tan of about 0.5 [13, 14, 27]. We concentrate on two benchmark a1 masses: 8 and 15 GeV. Our results depend weakly on this mass; therefore, the 8 GeV threshold is representative of masses just below and just above the bb threshold, where the constraint cos A tan . 0.5 does and does not apply respectively. In the parameter region where one of the CP -even Higgses h2,3 is lighter than 150 GeV, the direct search bounds for light neutral Higgses in associated production hia1 (i = 2, 3) at LEP-II can be considered [28]. The final states can be, for example, 4b or 2b2 . However, even for h2,3 light enough for this associated production to be possible, the cross-section is proportional to the doublet component of a1 and is usually small in our scenario. The upper bounds in [28] constrain cos2(A) Ui2H (i = 2, 3) times branching ratios as a function of the masses, but this can easily be small enough to be consistent with the bounds. We therefore ignore the LEP-II constraint throughout this paper. The masses of the extra neutral and charged Higgs bosons can affect the custodial symmetry breaking parameter = M W2 /(MZ2 cos2 W ), where W is the weak mixing angle. Since we are considering extensions of the Higgs sector involving only SU(2) doublets and singlets, contributions to 1 appear only at loop level. In our type-II 2HDM + singlet reference scenario with = a2 (mostly doublet), A = a1 (mostly singlet) and the SM-like Higgs boson discovered at the LHC identified with h1, depends also on the two remaining CP -even states h2,3. For a simple demonstration of the constraint, we assume that one of these two states is completely doublet (the field-space basis state H defined above). Then the main contributions to the vacuum polarization of the W by H a2 and H H loops need to be cancelled by that of the Z by H a2 loop. Therefore one can roughly expect the contribution due to the mass difference between H and a2 can be cancelled by that between H and a2, while making that of the H H loop to the W boson small. (In the 2HDM, complete contributions to the oblique parameters are well depicted in the appendix D of the reference [29].) In figure 2, we show the H mass range allowed at 95 % C.L. by the present determination of [30] for given masses of a2 and H. The solid (blue) contours give the maximum value of mH required to satisfy the experimental constraint; the dashed (green) contours show the difference between the maximum and minimum mH required and are therefore a measure of the (low) fine tuning between mH and mH that we require. We find that in the parameter space where our process is dominant (m mH & MW ) the contributions to can easily be compensated by the contributions of other Higgs states, although the fine tuning between mH+ and mH increases as ma2 does. It is quite possible for the H state to remain unconstrained by LHC Higgs searches. Based on this result, we simply ignore the constraint throughout this paper. We also ignore possible mass relations amongst the various Higgs bosons which depend on the exact details of the Higgs sector Lagrangian. Charged Higgs decays When the charged Higgs is lighter than the top quark (light charged Higgs), investigating only the usual or cs final states from its decay may not be enough for discovery. This is because the process H+ W +A, whose decay rate is proportional to m3H+, can easily dominate over the + and cs final states. The detailed analysis of the light charged Higgs from the top quark decay in the context of the type-II 2HDM + singlet is shown in ref. [15], where the lightest CP odd neutral Higgs a1 is the particle A. The main factors determining the BR(H+ W +a1) are the SU(2) doublet fraction (at the amplitude level) in a1 (cos A) and tan . According to that analysis, BR(H+ W +a1) rapidly approaches unity for mH+ > MW + ma1 even when the light Higgs a1 is highly singlet-like, as long as tan is small. For a charged Higgs heavier than the top quark (heavy charged Higgs), the channel H+ tb opens to compete with the process H+ W +A. In the context of the typeII 2HDM + singlet, we show the dependence of the BR(H+ W +a1) on cos A and tan in figure 3. For low tan . 5, the value of (H+ tb) is dominantly determined by the (mt/v)2 cot2 term, so the BR(H+ W +a1) increases for larger tan . (See appendix A for the detailed formulae.) Above threshold the ratio of the H+ W +a1 and H+ tb decay rates is proportional to cos2 A tan2 m2H+. For ma1 = 8 GeV the constraint cos A tan . 0.5 applies and hence BR(H+ W +a1) is at most around 30 % for mH+ < 400 GeV, increasing for larger charged Higgs masses. On the other hand, we do not need to consider this bound when a1 is heavier than about 9 GeV, so in this case the mmHax-mmHin 95% CL D allowed region, cos2A=0.1 150 200 250 300 BR(H+ W +a1) can be larger than 0.5, corresponding to larger values of cos A tan when ma1 is set to 15 GeV in figure 3. Far above thresholds and at low tan we have Consequently, BR(H W a1) can be still larger than 0.5 even after the on-shell H+ tb decay opens, as long as a1 is heavier than about 9 GeV. For large values of tan ( 7) the tan dependence of BR(H+ W +a1) is reversed since the (mb/v)2 tan2 term in (H+ tb) is dominant. Heavy neutral Higgs decays The W H decay can easily dominate over decays into SM fermions, including top quarks. In the type II 2HDM + singlet scenario we set A = a1 and = a2 (which is the heavy CP -odd Higgs); then figure 4 shows how BR(a2 HW ) varies with tan and the various masses. For small tan , the branching ratio is affected by the partial width a2 tt, whose rate depends on cot2 . Since we only consider this decay and decays into SM fermions, all taking place via the doublet (AH ) component of a2, the sin2(A) dependence cancels out of all of the branching ratios of a2. For our reference type-II 2HDM + singlet scenario we assume the possible decays a2 hiZ and a2 hia1 to be subdominant compared to a2 HW , where hi is a CP -even neutral Higgs. This is tan() = 1, cos() = 0.5 tan() = 1, cos() = 0.1 tan() = 2, cos() = 0.1 tan() = 5, cos() = 0.1 tan() = 1, cos() = 0.5 tan() = 1, cos() = 0.1 tan() = 2, cos() = 0.5 tan() = 2, cos() = 0.1 tan() = 5, cos() = 0.5 tan() = 5, cos() = 0.1 tan() = 10, cos() = 0.5 tan() = 10, cos() = 0.1 tan() = 20, cos() = 0.5 tan() = 20, cos() = 0.1 tan() = 50, cos() = 0.5 tan() = 50, cos() = 0.1 1 0.9 0.8 ) 0.7 W 0.6 H 0.5 20.4 a (R0.3 B 0.2 0.1 in order to reduce the number of parameters relevant for determining cross-section times branching ratios in this reference scenario (to be compared to the general bounds on this cross-section times branching ratios that we derive). The processes a2 hia1 are model dependent even within the type II 2HDM + singlet scenario. As for the possible decay modes a2 hiZ: the more SM-like the 125 GeV particle discovered at the LHC (h1) is (the more h1 h, see section 2.1), the more suppressed the decay to h1Z will be. On the other hand the other final states hi>1Z can reduce the relevant BR(a2 HW ) by up to about 1/3, if we consider that the constraint requires very approximate mass degeneracy of H and any state significantly overlapping with H (The width to ZH is equal to the width to H+W if one ignores the phase-space factor). The results we present (e.g. the new bound in the (tan , mH ) plane for ma2 2mt) are not much affected by the presence of this decay mode and we will neglect it altogether in the following. Far above thresholds we have (a2 H+W ) + (a2 HW +) (a2 tt) Heavy neutral Higgs production The dominant production mechanism for hSM at the LHC is ggF mediated by quark loops, mainly dominated by the top quark loop due to its large Yukawa coupling. The production cross-section of depends on its modified couplings to up- and down-type quarks. The AH and H interaction states, defined in section 2.1, have couplings to up-type quarks suppressed by 1/ tan and couplings to down-type quarks enhanced by tan . The production of a2 is also modified at leading order since there are different form factors for the scalar and pseudoscalar couplings; CP -even Higgs bosons couple to fermions via scalar couplings and CP -odd couple via pseudoscalar. At leading order the ggF production cross-section for a scalar or pseudoscalar is proportional to 3 X gqA1/2 A1H/2( ) = 2[ + ( 1)f ( )]/ 2 where g is the relative coupling to the quark q (relative to that of the SM Higgs) and mq is the quark pole mass. The form factors A1/2 are equal to for scalar and pseudoscalar couplings respectively. The universal scaling function f can be found, for example, in ref. [31, 32]. In the limit 0 the functions A1H/2( ) and 8 TeV 102100 150 200 250 300 350 400 450 500 550 600 mh2/GeV 14 TeV & inc. bbF 14 TeV & inc. bbF 102100 150 200 250 300 350 400 450 500 550 600 mh2/GeV A1A/2( ) tend to 4/3 and 2 respectively, so the ratio squared tends to 2.25. The K-factors (the ratios of cross-sections to their leading order approximations) are typically around 1.8 and cannot be neglected. In this work, to calculate the CP -odd (AH ) and CP -even (H) doublet production we take the 8 and 14 TeV ggF production cross-sections recommended by the CERN Higgs Working Group [33] (calculated at NNLL QCD and NLO EW) for a SM Higgs of the same mass M and multiply by the ratio where gq = {tan(), cot()} for {down-, up-} type quarks q. (This is also the approach taken in ref. [34].) We checked the consistency of this approach using the Fortran code HIGLU [35, 36] at NNLO QCD and NLO EW level with the CTEQ6L parton distribution functions. For the cases of a2 and h2 the cross-section will have an additional suppression of approximately sin2 A and U2H respectively, since only the doublet admixture couples 2 to quarks. These production cross-sections at 8 and 14 TeV are shown in figure 5. Note that for AH there is a sharp peak around the tt threshold region for small tan (where the top loop dominates) due to the pseudoscalar form factor. Below the tt threshold the shapes of the curves are highly dependent on whether the top or bottom loop dominates. This is because the form factor looks quite different depending on whether one is above threshold (bottom loop case) or below threshold (top loop case). At moderate and large tan (i.e. tan & 5) heavy neutral Higgs production in bottom fusion (bbF, upper right plot in figure 1) can be larger than in gluon fusion (ggF, upper left plot in figure 1). In fact, although the probability to find a bottom quark in a proton is small (whereas gluons have the largest parton distribution function at LHC center-of-mass energies), this is compensated by the fact that bbF is an electroweak tree-level process (whereas the ggF is one-loop suppressed). In the lower plots of figure 5 we show the impact of adding the bbF cross-section (calculated using FeynHiggs [3740]) to the ggF one for s = 14 TeV; clearly the effect is sizable only for large values of tan & 10. Note that at small tan ggF is large and dominant and that at large tan bbF controls the crosssection; at intermediate values of tan 5 the ggF suppression is not yet compensated by the bbF enhancement and we find relatively small cross-sections. Total cross-sections Combining the previous results, we can obtain the complete cross-section times branching ratios (gg a2 W +W a1) at 8 TeV in figure 6 for various masses and values of tan and cos A. For small tan , we can easily obtain a total cross-section times branching ratios O(pb), which is comparable to the SM Higgs production times BR(hSM W +W ). Hence the LHC Higgs search result can constrain the maximum total cross-section of our process, as will be discussed in the next section. For very large tan (& 20) our study is not very sensitive because the tan dependence of the a2 production cross-section (responsible for the enhancement of the latter at large tan ) is compensated by the tan suppression of the branching ratio BR(a2 W +W a1). The complete branching ratios BR(a2 W +W a1) are calculated as outlined in appendix B and are shown in figure 7. For comparison, we also show the expected total cross-section at 14 TeV for both = a2 and = h2 in figures 8 and 9 respectively. Note that in these plots we add the ggF and bbF production cross-sections. The most important effect of adding the latter is bmH = 160 GeV, ma1 = 8 GeV 8 TeV bmH = 160 GeV, ma1 = 15 GeV 8 TeV ma2 = 360 GeV, ma1 = 8 GeV 8 TeV ma2 = 360 GeV, ma1 = 15 GeV 8 TeV bmH = 110 GeV, a2101 ( R B102 ) a2103 a2101 ( R B102 ) a2103 a2101 ( R B102 ) a2103 g104100 g ( a2101 ( R B102 ) a2103 a2101 ( R B102 ) a2103 a2101 ( R B102 ) a2103 g104 g ( to tan 5 we expect to be sensitive to all values of tan (depending on cos A). When = h2, the complete cross-section (gg h2 W +W a1) divided by the mixing1 0.9 )10.8 a0.7 W0.6 W0.5 20.4 (a0.3 R B0.2 0.1 tan() = 1, cos() = 0.5 tan() = 1, cos() = 0.1 tan() = 2, cos() = 0.1 tan() = 5, cos() = 0.1 1 0.9 )10.8 a0.7 W0.6 W0.5 20.4 (a0.3 R B0.2 0.1 tan() = 1, cos() = 0.5 tan() = 1, cos() = 0.1 tan() = 2, cos() = 0.5 tan() = 2, cos() = 0.1 tan() = 5, cos() = 0.5 tan() = 5, cos() = 0.1 tan() = 10, cos() = 0.5 tan() = 10, cos() = 0.1 tan() = 20, cos() = 0.5 tan() = 20, cos() = 0.1 tan() = 50, cos() = 0.5 tan() = 50, cos() = 0.1 element-squared U22H is shown. We show that it is possible to have total cross-sections O(10 pb) in some regions of the parameter space. In these figures we include also a heavier charged Higgs masses, above the tb threshold. In this method of estimating the total cross-section, multiplying the production crosssection by the branching ratios, the non-zero width of the heavy state is neglected. We check that for m above the HW threshold, going beyond the zero-width approximation for is a numerically small effect in the parameter space we consider. Below the HW threshold the finite width effects can be important if the width of is already comparable to the widths of H and W (the dominant contribution can come from going off-shell rather than H or W ). We find that this can only occur at extreme values of tan ( 20 or 1 if m > 2mt). In these cases our method can underestimate the below threshold (off-shell) total cross-section. See appendix C for more details of the width. Our zerowidth approximation for the heavy state does not affect the limits that we derive. (For the kinematics the finite width effects are included.) The constraint from Standard Model h W +W searches Model independent study The CMS collaboration observed a SM Higgs signal in the W +W `+` channel (final states with zero jets or one jet were included) with a mass of approximatively 125 GeV [21] 2 (a101 R B )a2102 b ,bg103 (g 104 2 (a101 R B )a2102 b ,bg103 (g 104 2 (a101 R B )a2102 b ,bg103 (g 104 a2101 ( R B )102 a2 gg103 ( 104 a2101 ( R B )102 a2 gg103 ( 104 a2101 ( R B )102 a2 gg103 ( 104 at a significance of 4. CMS also provides an exclusion bound for a SM Higgs bosons in the mass range 128600 GeV at 95 % confidence level (C.L.). The process that we are considering (pp W +W A) leads to a very similar final state, the only difference being 2101 h ( R B102 ) h2 b103 b , g g (104 2101 h ( R B102 ) h2 b103 b , g g (104 2101 h ( R B102 ) h2 b103 b , g g (104 the light Higgs A decay products that lead to extra jets or leptons. We, therefore, expect this search to provide strong constraints on the charged Higgs production mechanism we consider and potentially to offer an avenue to discover a charged Higgs. However, due to the presence of the light Higgs A, the distributions of kinematic variables that we obtain are different from those expected in the SM Higgs search. In order to apply the results in ref. [21] we need to calculate how the efficiency of the various cuts adopted in that analysis are affected by the presence of the light Higgs A. The constraints that we derive are valid for a light Higgs A whose mass is just above the bb threshold and which decays dominantly to a pair of bottom quarks. In the CMS analysis the number of jets (for the purposes of separating the events into channels; 0, 1, or more) is defined as the number of reconstructed jets with pT > 30 GeV (and || < 4.7), reconstructed using the anti-kT clustering algorithm with distance parameter R = 0.5. For purely kinematic reasons, when the pT of the A is as large as 30 GeV the angular separation (R) between the two b quarks is going to be small (compared to 0.5) for the A masses that we consider and therefore any A final state with high enough pT to count as a jet will in fact have its final state b quarks cluster into a single jet most of the time. This has been explicitly checked in ref. [15] (for A +, + ) and in ref. [41] (for A bb see figure 6 therein). Using MadGraph we checked that for mA up to around 15 GeV, the R angular opening of the two b quarks is small enough to treat the bb system as a single fat jet (obviously for a low enough pT cut and/or a large enough mA, the two final state b quarks can look like two distinct jets). For mA below the bb threshold A will decay mainly to lepton pairs or maybe to charm quark pairs. For example, for A = a1, decaying via its AH admixture, decays to pairs will dominate until very low tan 1.3, where decays to charm pairs begin to overtake [27]. For such decays into charm quarks the opening angle cannot exceed 0.5 and the decay products will mostly be clustered into a single jet. For the decays into leptons, the decay products will also mostly be clustered into a single jet and give no additional isolated leptons; the exception is when both leptons decay leptonically (about 13 % of the time). In this case there will be no jet and quite possibly extra isolated leptons that would lead to the event not passing the selection criteria in the CMS analysis. This small effect should not much affect our results. The CMS collaboration presented exclusion bounds obtained using two different techniques to isolate the signal from the background. The first is a cut-based analysis in which separate sets of kinematic cuts are applied for each different Higgs mass hypothesis. The second is a shape-based analysis applied to the distribution of events in the two-dimensional (mT , m``) plane. In this paper, we apply the cut based analysis of ref. [21] to our signal; at this time, we cannot proceed with the shape-based analysis since the CMS note does not provide enough detail. All of the CMS data are split into four channels depending on whether the two leptons have different or the same flavor (DF, SF) and whether there is zero or one high pT (> 30 GeV) jet (0j, 1j). In each channel the expected background, expected signal, and observed data are given for several SM Higgs mass hypotheses. For each of these hypotheses a different set of cuts is applied. The cuts used for SM Higgs searches with mass hypotheses 120, 125, 130, 160, 200, and 400 GeV are presented in table 1 of ref. [21]. Extra cuts are also applied for the SF channels in order to suppress background from Drell-Yan processes. In this paper, we analyze the 19.5 fb1 of data collected at s = 8 TeV and presented in table 4 of ref. [21]. To obtain the observed upper limit from applying the cuts in each channel and corresponding to each SM Higgs mass hypothesis we adopt a modified frequentist construction [42, 43]. (A brief summary of the CLs method is presented in appendix D.) The 95 % C.L. upper limit (on the number of events) that we obtain from our analysis is indicated with `FHJ , where H refers to each of the SM Higgs mass hypotheses and F J to the channel considered (F {DF, SF} and J {0j, 1j}). The value of `FHJ has to be compared to the expected signal EFHJP , where P stands for the considered theory and point in parameter space. (For the type-II 2HDM + singlet scenario P stands for the relevant Higgs boson masses, cos A, and tan .) In the type-II 2HDM + singlet reference scenario the expected signal in the 0j channel is then AP cos2 A sin2 AP BaP2 AP cos2 A + BP aFH,Prel , |(gg{za2)} where the exact A dependence has been factored out. Here sFH0 is the number of expected events for each of the six SM Higgs mass hypotheses H in each channel F 0 in table 4 of the CMS note [21]. BHH is the production cross-section times branching ratio for that SM Higgs. The production cross-section times branching ratio for gg a2 HW is given by sin2 AP BaP2. In the branching ratio for H a1W we factor out the cos2 A dependence and define AP = (H A1H W ) and BP = (H / a1W ), where AiH is the pure AH interaction state with the mass of ai. xHP is the fraction of events that have F one more jet (in addition to those from initial or final state QCD radiation) passing the jet selection due to the decay of a1. Here these events are therefore removed from the 0j channel and appear in the 1j channel. aFH,Prel is the relative acceptance for our signal and, for each Higgs mass hypothesis H, is defined as the ratio of the fraction of pp a2 W W a1 events that survive a given cut H to the fraction of SM Higgs events that survive the same cut. Both of these numbers depend on F since extra cuts are applied in the SF channels. The exact definition of this relative acceptance is For the expected signal in the 1j channels, we obtain AP cos2 A sin2 AP BaP2 AP cos2 A + BP aFH,Prel . mA = 8 GeV 8 TeV EFHJP < `FHJ . We apply whichever of these conditions leads to the best upper limit on the production cross-section times branching ratios for our signal. These limits on cross-section times branching ratios are model independent in the sense that they apply to any model containing , H, and A particles and depend only on the masses of these particles. Moreover, they do not depend on the CP nature of the and A Higgs bosons because the is produced on-shell and the structure of the 0V decay (where (0) are spin-0) does not depend on the CP nature of the (0) (see appendix A). These cross-section limits are shown in the upper plots in figure 10 and they are superimposed on our reference scenario in figure 6. When deriving these limits l we assume a fractional systematic error for the expected signal appearing in each channel of 30 %, which we consider to be conservative (see appendix D). We find that the limits hardly vary with mA at all for the range that we consider. The peaks that appear in the left plot are due to us only having data for discrete values of the SM Higgs mass hypothesis. For instance, the most prominent peak corresponds to the mass at which the 400 GeV cuts take over the 200 GeV cuts in providing the best upper limit. Currently only very low values of tan (. 2) can be constrained in our reference scenario. The strongest constraint is obtained near the tt threshold region, for this reason we choose ma2 = 360 GeV as a reference point in the detailed parameter space study presented in the next subsection. If the analysis were to be performed again using a more appropriate set of cuts for each set of masses the suppression due to the relative acceptance (see eq. (3.2)) could certainly be reduced. In fact, since the SM Higgs to W W signal and our signal are very similar, it is reasonable to presume that optimized cuts would lead to relative acceptances closer to unity. This would remove the peaks and slightly lower the baseline in the plot in figure 10, leading to an order of magnitude improvement on the upper limit in some parts of the parameter space. Existing 8 TeV data could, therefore, be used to probe more moderate values of tan . Estimating the possible sensitivity of a dedicated search at s = 14 TeV is not simple, nonetheless the problem is one of distinguishing a signal over the uncertainty of the background. Assuming that with more data the background determination continues to be statistics limited and assuming that going from 8 to 14 TeV the background crosssection roughly doubles we can very roughly predict that at 14 TeV with 100 fb1 (500 fb1) of data a dedicated analysis could be sensitive to cross-sections of order 0.6 pb (0.3 pb), to be compared with the kinds of signals predicted in figures 8 and 9. A proper analysis would need to be carried out by the experimental groups after collecting more data. It is also worth pointing out that our xHP parameter is almost always closer to unity F than to zero. In the SM search the limits coming from the 0j and 1j channels are comparable. In our case, however, the best limit almost always comes from the 1j channels, with the 0j channels setting much weaker limits. Almost as many events are moved out of the 1j channels due to the non-zero xHP than are moved from the 0j into the 1j channels, F so the large xHP does not significantly increase the limits coming from the 1j channels; F it just weakens the limits coming from the 0j channels. However, if one were to look at a 2j channel, with the same cuts as in the 0j and 1j channels, but requiring exactly two high pT (> 30 GeV) jets, the situation could be different. Such a channel would not be useful for the SM Higgs to W W search (the 2j channel discussed in the CMS analysis [21] has completely different cuts and is designed to single out vector boson fusion production) and is therefore not considered in SM searches. However, for our process the probability to have two high pT jets even in the ggF production, one coming from initial or final state radiation and another coming from the A decay, is significant. Such a 2j channel would also likely have a smaller background and could lead to better limits than the 1j channels for which we have data. If we replace the a2 with one of the CP -even states, = h2, in our type-II 2HDM + singlet scenario the analysis is similar. In this case there is, however, another independent parameter, the H fraction in h2, U22H . This affects the production of but not the decays of h2 under the assumptions outlined in subsection 2.3. The type-II 2HDM plus singlet case As explained in the previous section, SM Higgs W W searches allow one to place model independent constraints on a charged Higgs produced in the decay of a heavy neutral Higgs and decaying to W A, where A is a generic light neutral Higgs. In this section we apply the results presented in section 3.1 to the special case of a type-II 2HDM with an extra SM singlet. In the context of this model the limits worked out in section 3.1 apply at relatively low tan (. 2). In figure 11 we show the limits we obtain for ma2 = 360 GeV. As explained in the previous section we choose ma2 = 360 GeV as a reference point because the constraints we obtain are the strongest around the resonance region ma2 2mt. The figure shows the excluded regions in the (mH , tan ) plane for various values of ma1 {8, 15} GeV and cos2 A {0.1, 0.01}. The grey region is excluded by direct searches at LEP [5761]. The blue and green regions are excluded by Tevatron and LHC searches in the [6, 7, 62] and cs [63] final states, respectively. The pink region is excluded by a combination of searches at BaBar [11, 12] (3s a1 channel) and at the LHC [13, 14] (direct gg a1 production); this pink exclusion only applies for ma1 just below the bb threshold and not for ma1 just above. The red area is excluded by a dedicated t bH+ bW +a1 bW + + search at CDF [56]. The purple area surrounded by the thick black solid line is the additional region of parameter space excluded by our study in the gg a2 W +W a1 channel. At lower values of cos2 A the exclusion region narrows due to the cos2 A dependence of BR(H W a1) (see the discussion in section 2.2). In particular, for (ma1 , cos2 A) = (8 GeV, 0.1), the light charged Higgs parameter region analyzed in ref. [15] is completely excluded (if a heavy Higgs with mass ma2 = 360 GeV is present). On one hand, at low values of tan . 0.03 we lose sensitivity because the a2 width becomes dominated by a2 tt. On the other hand, at large tan 10 either the a2 production cross-section or BR(a2 W +W a1) are suppressed and our search loses sensitivity. Our study extends also to charged Higgs masses above the tb threshold. Unfortunately, sensitivity in this region is not currently very strong for the following two reasons. First, in this region the H W a1 branching ratio is suppressed at low tan . 2 and very large tan 10 unless the charged Higgs mass is fairly large (see figure 3). Second, as the charged Higgs mass increases, the phase space for the a2 HW decay shrinks; this can be compensated by raising the a2 mass at the price of a reduced production cross-section. In conclusion, we do not currently find appreciable constraints for mH & 180 GeV. This heavy charged Higgs parameter space could be constrained in the future with more data. In figure 12 we show regions that we exclude in the (ma2 , cos2 A) plane at fixed values of mH {110, 160} GeV, ma1 {8, 15} GeV, and tan . The region above the dotted line is excluded by direct a1 searches at BaBar and at the LHC (tan cos A . 0.5 [15, 27]) mH = 110 GeV, ma1 = 8 GeV mH = 160 GeV, ma1 = 8 GeV mH = 160 GeV, ma1 = 15 GeV 103 103 when ma1 is just below the bb threshold. The reason for the weakening of the limits for intermediate a2 masses in figure 12 is purely due to the fact that we have data for the cuts corresponding to SM Higgs mass hypotheses of 200 GeV and 400 GeV, but nothing in between. This then causes the peaks of weakening limits in figure 10 and the effects can be seen in figure 12. (See also figure 6.) The experimental discovery at the LHC of a particle compatible with the SM Higgs boson is the first step towards a full understanding of the electroweak symmetry breaking mechanism. Assuming that the particle discovered at the LHC is a fundamental scalar, it becomes imperative to figure out what exactly the Higgs sector is. Many beyond-the-SM scenarios contain a second Higgs doublet and predict the existence of at least one charged Higgs and several neutral CP -even and -odd Higgs bosons. Most experimental searches have been conducted under the rather traditional assumption that the charged Higgs dominantly decays into or cs pairs at low-mass (mH . mt) and into tb otherwise. The existence of a light neutral Higgs A opens the decay channel H+ W +A and offers new discovery venues. In this paper, we study a charged Higgs whose production mechanism relies on a heavy neutral Higgs () and whose dominant decay is into a light neutral Higgs (A) pp W H W +W A. For mA & 2mb, this particle decays dominantly to pairs of b quarks that are detected, at sufficiently high pT , as a single jet. Under these conditions, the final state is simply W +W plus jets and is, therefore, constrained by SM Higgs searches in the W W channel (this is also mostly true for mA below the bb threshold). For mA . 2mb, the A dominantly decays into pairs, whose decay products will also mostly be clustered into a singlet jet unless both s decay leptonically. (The latter case provides no extra jets and extra isolated leptons that would lead to the event not passing the selection criteria in the CMS analysis. This may however be another useful signal to search for.) Using existing data on searches for a SM Higgs in the range 128600 GeV we are able to place constraints on this new physics process. In particular, we find that the upper limit on the production cross-section times branching ratios for the process in (4.1) are in the O(110 pb) range for a wide range of , H and A masses. The results (presented at the top of figure 10) depend very loosely on the details of a given model and will be useful to constrain a vast array of theories that contain three such particles. In particular the limits depend only on the masses of the three particles and not on the CP nature of and A. For the sake of definiteness we specialize our results to an explicit type-II 2HDM plus singlet reference scenario and show that our results are able, at low tan , to exclude previously open regions of parameter space. The constraints we derive are shown in figures 11 and 12. They are limited both because we only have partial access to the relevant data and because the cuts used for the SM Higgs search are not quite optimized for the process we consider. We point out that a slight modification of the search strategy, using more appropriate cuts that depend on the hypothesized masses of and H, would lead to better limits and would be sensitive to more moderate values of tan . Our analysis extends, in principle, to arbitrarily large charged Higgs masses. In practice, the parametric dependence of the production crosssection and branching ratios on the charged Higgs mass limits our present sensitivity to mH . 180 GeV. However, the parameter space with a heavier charged Higgs could be constrained in the future at the 14 TeV LHC. We point out that once the contribution to production from bb fusion is taken into account alongside gg fusion, sensitivity to all values of tan in our reference scenario should be achieved at the 14 TeV LHC. With 100 fb1 of data we very roughly estimate that sensitivity to cross-sections of order 0.6 pb would be achieved, to be compared to the kinds of cross-sections predicted in figures 8 and 9. A search for the process where the charged Higgs is produced in the same way but goes to tb is also being considered [64]. Finally, let us comment on the possibility that our process might contribute sizably to the total pp W +W cross-section. A recent CMS measurement with 3.54 fb1 of integrated luminosity at 8 TeV, found a slight excess in this channel: 69.9 2.8 5.6 3.1 pb against a SM expectation of 57.3+21..46 pb without the inclusion of the SM Higgs contribution [65]. Even after accounting for this an additional contribution of several pb seems to be required (see for instance ref. [66] for a possible explanation of this tension in a supersymmetric framework). If this discrepancy survives, the process discussed in this paper could potentially offer a contribution of the correct order of magnitude. Acknowledgments R.D. is supported in part by the Department of Energy under grant number DE-FG0291ER40661. S.S. is supported by the TJ Park POSCO Postdoc fellowship and NRF of Korea No. 2011-0012630. E.L. would like to thank Frank Siegert for substantial help with the Sherpa Monte Carlo. Decay rates3 12 = (1 k1 k2)2 4k1k2, 1 = p11 = p1 4k1. Allowing the W to be off-shell and assuming it can decay to all light fermions (excluding tops), which we take to be massless, we can write 0 1x2k (1 x1)(1 x2) k (1 x1 x2 k + kW )2 + kW W Here 1 and 2 label the fermions from the W decay.4 This formula is valid for AH HW , H HW , and H AH W . For a2 HW and H a1W , with the conventions defined in section 2.1, there is a suppression by sin2(A) and cos2(A) respectively. Writing the integral in this way, the inner x1 integration can be performed analytically and the remaining integrand behaves well for numerical integration and the 3A more complete list of two- and three-body tree-level decays relevant in Higgs sector extensions containing doublets and singlets, along with accompanying C++ code, will be presented in ref. [68]. 4This is for one particular charge of W . The equivalent formula for a Z boson is obtained by replacing W Z everywhere. The formulae in ref. [32] (2.20) and ref. [67] (41,58,59) are a factor of 2 too large for the W boson case, whereas the formula for the Z boson case are correct. This is because Z (as defined in ref. [32]), rather than being the ratio of the Z and W widths times cos3 W , contains an extra factor of 1/2. This is the symmetry factor relevant for the V V decays, but not the V decays. There is also a typo in the sin4 W term in Z in ref. [32]. outer integration over x2 can evaluated numerically very quickly. For completeness, above threshold in the zero-width on-shell approximation we can write5 In this massless fermion approximation we can write Other AH decays For light quarks q QCD(M ) + (35.94 1.36 nf ) QCD(2M )2 , mq is the running mass at the scale M = mAH , and nf is the QCD number of flavours at M . Further QCD corrections for the scalar and pseudoscalar decays to quarks are derived in refs. [69] and [70] and summarised in ref. [32], but these are only valid in the heavy top mass limit, i.e. when the boson is light compared to the top quark. For charged leptons l +2kW ((1 xt)(1 xb) kW ) Here mb has been neglected in the integrand.The leading QCD correction can be included by using the running mass for the mt2 factor that appears out front, which comes directly from the Yukawa coupling in the Feynman rule. In the integrand and in the integration limits the running mass is not used (for kt and kb) so that the threshold appears in the correct place.6 For three-body decays written in terms of the xs (energies) of two (1 and 2) 5This is also for one particular charge of W and the equivalent formula for a Z boson is again obtained by replacing W Z. This on-shell formula in ref. [32] (2.18) contains a typo that makes it dimensionally inconsistent. The formulae in ref. [67] (38,39,51,57) are correct, except that (57) contains an erroneous factor of cos2 W . 6This formula is correct in ref. [67] (55,56), but the expression in ref. [32] (2.8) is a factor of 2 larger. The formula (2.8) as written is correct below threshold after one takes into account that either top can go off-shell, but is then a factor of 2 too large above threshold. Our approach is given in the text. of the three final states particles (1, 2, and 3) the kinematic limits are, without neglecting any masses, 8GF 2 mt3(1 kW )(1 + 2kW )b1W/2. A formula for (AH tt bW +bW ) that is valid both above and below threshold can be obtained by doubling (AH tt tbW ) and using 4t in place of t. Above threshold in the zero-width on-shell approximation we can write (AH tt) = 43GF2 taMn2m( t2 ) t. Other H decays (H qq) = 3GF (gqAH )2M mq2(1 + qq) , 4 2 1.57 32 ln Again, a formula for (H tt) that is valid both above and below threshold can be obtained by doubling (H tt tbW ) and using 4t in place of t. Above threshold in the zero-width on-shell approximation we can write (H tt) = 43GF2 taMn2m( t2 ) t3. Other H decays For light up- and down-type quarks u and d, assuming ku, kd One of the (1 kl) factors comes from the matrix-element-squared and the other is the phase-space factor l . 3GF M ptb 42 h(1 kt kb)(mb2 tan2() + mt2 cot2()) 4mbmtpktkbi . (A.21) Off-shell H In the off-shell decay W H W W A, the decay widths W and H roughly decide which one is preferred to be off-shell. The full decay width of H in our type-II 2HDM + singlet reference scenario is shown in comparison with W in figure 13. For an H with a mass much above the tb threshold the possible three-body decay of through an off-shell H needs to be considered. ( W +H W +tb) 8The mt2 term given in ref. [67] (63) seems to be incorrect, producing a different shape to our formula below threshold and not agreeing with the on-shell formula above threshold. All our formulae are checked to make sure that they reproduce the on-shell zero-width approximation formulae sufficiently above threshold, up to finite width effects. eV101 G / H102 103 104 ( W +H W +W ) eV101 G / H102 103 104 50 100 150 200 250 300 350 400 450 500 mH/GeV this determines which one preferably goes off-shell. 4mbmtpkbkt (x1 2kW ) 4kW (1 x1 + kW ) (1 x1 k)2 4kW k 2 (1 x1 + kW kH )2 + kH H suppressed by mixing angles for other mass eigenstates that are not completely doublet. B Branching ratios Only two and three-body decay rates are calculated to allow for fast numerical integration. product of the two branching ratios These individual branching ratios can be calculated using off-shell W s and tops. 101 101 100 150 200 250 300 350 400 450 500 550 600 ma2/GeV Alternatively, allowing the H to go off-shell, we can write 2( W +H W +W A)y + 2( W +H)yBR(H W A) 2( W +H W +X)y + 2( W +H)y + ( 9 W H) , should be used in place of the actual off-shell particle width in the integrand denominator ( y2/M 2). Here tops and W s coming from the H are on-shell. This formula is really only needed for H masses above the tb threshold anyway, as can be seen by looking at figure 13. This formula provides a very good approximation to real answer calculated using four-body decay widths (allowing both the H and W to be off shell) much better than just allowing the particle with the largest width to be off-shell but is built out of three-body decay widths and can therefore be quickly evaluated using single numerical integration. Figure 14 shows the width of a2 (divided by its doublet fraction) in the type-II 2HDM + singlet scenario. The contribution to the total cross-section from a2 going off-shell (rather than H or W ) can be important at high tan or at very low tan if mH + MW > 2mt. For large a2 masses the width of a2 can become very large. CLs limits = P (D |H0) P (D |H1) B + S = b + s qb2 + s + s22, where s is the expected signal, its statistical error is taken to be s, its fractional systematic error is taken to be . In this paper, we set = 30% as a conservative bound. We approximate everything as Gaussian. We therefore take Where is the cumulative distribution function. For a given b, b, D, , and the 1 confidence level limit on s can therefore be found. We call this solution s = l. For our calculation, the parameters are obtained from ref. [21]. Open Access. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.


This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1007%2FJHEP04%282014%29140.pdf

Radovan Dermíšek, Jonathan P. Hall, Enrico Lunghi. A new avenue to charged Higgs discovery in multi-Higgs models, Journal of High Energy Physics, 2014, 140, DOI: 10.1007/JHEP04(2014)140