750 GeV Diphoton Resonance from Singlets in an Exceptional Supersymmetric Standard Model

The 750-760 GeV diphoton resonance may be identified as one or two scalars and/or one or two pseudoscalars contained in the two singlet superfields S_{1,2} arising from the three 27-dimensional representations of E_6 . The three 27s also contain three copies of colour-triplet charge \mp 1/3 vector-like fermions D,\bar{D} and two copies of charged inert Higgsinos \tilde{H}^{+},\tilde{H}^{-} to which the singlets S_{1,2} may couple. We propose a variant of the E_6SSM where the third singlet S_3 breaks a gauged U(1)_N above the TeV scale, predicting Z'_N, D,\bar{D}, \tilde{H}^{+},\tilde{H}^{-} at LHC Run 2, leaving the two lighter singlets S_{1,2} with masses around 750 GeV. We calculate the branching ratios and cross-sections for the two scalar and two pseudoscalar states associated with the S_{1,2} singlets, including possible degeneracies and maximal mixing, subject to the constraint that their couplings remain perturbative up to the unification scale.


Introduction
with W 1,2 referring to either W 1 or W 2 (but not both together which would result in excessive proton decay unless the associated Yukawa couplings were very small).
At the renormalisable level the gauge invariance ensures matter parity and hence LSP stability. All lepton and quark superfields are defined to be odd under matter parity Z M 2 , whilê H ui ,Ĥ di ,D i ,D i , andŜ i are even. This means that the fermions associated withD i ,D i are SUSY particles analogous to the Higgsinos, while their scalar components may be thought of as colour-triplet (and electroweak singlet) Higgses, making complete 5 and5 representations without the usual doublet-triplet splitting.
In order for baryon and lepton number to also be conserved, preventing rapid proton decay mediated byD i ,D i , one imposes either Z qq 2 or Z lq 2 . Under Z qq 2 , the lepton, including the RH neutrino, superfields are assumed to be odd, which forbids W 2 . Under Z lq 2 , the lepton and thê D i ,D i superfields are assumed odd, which forbids W 1 . Baryon and lepton number are conserved at the renormalisable level, with theD i ,D i interpreted as being either diquarks in the former case or leptoquarks in the latter case.
In the E 6 SSM, a further approximate flavour symmetry Z H 2 was also assumed. It is this approximate symmetry that distinguishes the third (by definition, "active") generation of Higgs doublets and SM-singlets from the second and first ("inert") generations. Under this approximate symmetry, all superfields are taken to be odd, apart from the activeŜ 3 ,Ĥ d3 , andĤ u3 which are taken to be even. The inert fields then have small couplings to matter and do not radiatively acquire VEVs or lead to large flavour changing neutral currents. The active fields can have large couplings to matter and radiative electroweak symmetry breaking (EWSB) occurs with these fields. In particular the VEV S 3 = s/ √ 2 is responsible for breaking the U (1) N gauge group and generating the effective µ term and D-fermion masses. In particular we must have s > 5 TeV in order to satisfy M Z ′ N > 2.5 TeV, which is the current LHC Run 2 experimental limit [170].
We now propose a variant of the E 6 SSM in which we allow all three singletsŜ i (as well aŝ H d3 andĤ u3 ) to be even under the Z H 2 . This allows all three singletsŜ i to couple toĤ ui and H di as well asD i andD i . If for simplicity we take the couplings in Eq. (6) to have the diagonal form, λ jki ∝ λ ji δ jk and κ jki ∝ κ ji δ jk , then the Z H 2 symmetry allows to reduce the structure of the Yukawa interactions in the superpotential to: The superfieldŜ 3 is assumed to acquire a rather large VEV ( S 3 = s/ √ 2) giving rise to the effective µ term, masses of exotic quarks and inert Higgsino states which are given by In our analysis here we restrict our consideration to the case when exotic quarks and inert Higgsinos are sufficiently light compared to the VEV s > 5 TeV, but are heavier than half the mass of the 750 GeV resonance, so that they appear in loop diagrams for the singlet decays. It means that the Yukawa couplings ofŜ 3 to all exotic states should be quite small. Throughout this paper we are going to assume that some scalar components of the first and second singletŝ S α , with α = 1, 2, can be identified with the resonances which give rise to the excess of diphoton events at an invariant mass around 750 GeV recently reported by the LHC experiments. ATLAS and CMS measurements indicate that the branching ratios of the decays of such resonances into SM fermions have to be sufficiently small. This implies that the mixing between the scalar components ofŜ α and the neutral scalar components of the third pair of Higgs doublets H u and H d , which are the ones that give rise to the EWSB, should be strongly suppressed. In order to ensure the suppression of the corresponding mixing we impose the further requirement, namely that the SM singletsŜ α , with α = 1, 2, have rather small couplings to the third pair of Higgs doublets H u and H d , i.e. λ 3α ≈ 0. This guarantees thatŜ α develop rather small VEVs and the mixing between the neutral scalar components ofŜ α , H u and H d can be negligibly small so that it can be even ignored in the leading approximation. In this context it is worth pointing out that if couplings κ i3 , λ 3α , λ α3 and λ 33 are set to be small at the scale M X then they will remain small at any scale below M X . Neglecting the Yukawa couplings λ 3α the low energy effective superpotential of the modified E 6 SSM below the scale Ŝ 3 can be written as where α = 1, 2 and i = 1, 2, 3. The superpotential (10) does not contain any mass terms that involve superfieldsŜ α . This implies that the fermion components ofŜ α can be very light.
In particular, the corresponding states can be lighter than 0.1 eV forming hot dark matter in the Universe. Such fermion states have negligible couplings to Z boson as well as other SM particles and therefore would not have been observed at earlier collider experiments. These states also do not change the branching ratios of the Z boson and Higgs decays ‡ . Moreover if Z ′ boson is sufficiently heavy the presence of such light fermion states does not affect Big Bang Nucleosynthesis [166]. The superpotential (10) contains ten new Yukawa couplings λ α1 , λ α2 , κ i1 and κ i2 . The running of these Yukawa couplings obey the following system of the renormalization group ‡ The presence of very light neutral fermions in the particle spectrum might have interesting implications for the neutrino physics (see, for example [171]).
(RG) equations: The requirement of validity of perturbation theory up to the Grand Unification scale M X restricts the interval of variations of these Yukawa couplings at low-energies. In our analysis here we use a set of one-loop RG equations (11) while the evolution of gauge couplings is calculated in the two-loop approximation.

750 GeV diphoton excess in the variant E 6 SSM
Turning now to a discussion of the 750 GeV diphoton excess recently observed by ATLAS and CMS in the framework of the variant of the E 6 SSM discussed in the previous section, whose effective superpotential is given by Eq. (10). This SUSY model involves two SM singlet super-fieldsŜ 1,2 plus a set of extra vector-like supermultiplets beyond the MSSM, including two pairs of inert Higgs doublets (Ĥ d α andĤ u α ), as well as three generations of exotic quarksD i andD i with electric charges ∓1/3.
The scenario discussed in this section is that the 750-760 GeV diphoton resonance may be identified as one or two scalars denoted N 1,2 and/or one or two pseudoscalars denoted A 1,2 contained in the two singlet superfieldsŜ 1,2 . The masses of these scalars and pseudoscalars arises from the soft SUSY breaking sector. However, to simplify our analysis, we assume that all other sparticles are sufficiently heavy so that their contributions to the production and decay rates of states with masses around 750 GeV can be ignored. Moreover the scenario under consideration implies that almost all exotic vector-like fermion mass states are heavier than 375 GeV so that the on-shell decays of N α and A α into the corresponding particles are not kinematically allowed.
Integrating out the heavy fermions corresponding to two pairs of inert Higgsino doublets H d α andH u α and three generations of vector-like D i and D i fermions, which appear in the usual triangle loop diagrams, one obtains the effective Lagrangian which describes the interactions of N α and A α with the SM gauge bosons, where In order to obtain analytic expressions forc iα one should replace in Eqs. (13) c iα byc iα and substitute function Because in our analysis we focus on the diphoton decays of N α and A α that may lead to the 750 GeV diphoton excess it is convenient to use the effective Lagrangian that describes the interactions of these fields with the electromagnetic one. Using Eq. (12) one obtains where c γ α = c 1α cos 2 θ W + c 2α sin 2 θ W ,c γ α =c 1α cos 2 θ W +c 2α sin 2 θ W and F µν is a field strength associated with the electromagnetic interaction.
At the LHC the exotic states N α and A α can be predominantly produced through gluon fusion. When exotic quarks have masses below 1 TeV the corresponding production cross section is rather large and determined by the effective couplings |c 3α | 2 and |c 3α | 2 . However such states mainly decay into a pair of gluons which is very problematic to detect at the LHC. Therefore possible collider signatures of these exotic states are associated with their decays into W W , ZZ, γZ and γγ. Since W and Z decay mostly into quarks the process pp → N α (A α ) → γγ tends to be one of the most promising channels to search for such resonances. In the limit when exotic states decay predominantly into a pair of gluons the branching ratios of N α → γγ and A α → γγ are proportional to |c γ α | 2 /|c 3α | 2 and |c γ α | 2 /|c 3α | 2 respectively. As a consequence cross sections σ(pp → N α (A α ) → γγ) do not depend on |c 3α | 2 and |c 3α | 2 . The corresponding signal strengths are basically defined by the partial decay widths Γ(N α → γγ) and Γ(A α → γγ).
The cross sections of the processes that may result in the 750 GeV diphoton excess can be written as where X α is either N α or A α exotic states, Γ Xα is a total decay width of the resonance X α while C gg ≃ 3163, √ s ≃ 13 TeV and M Xα is the mass of the appropriate exotic state which should be somewhat around 750 GeV. The partial decay widths of the corresponding resonances are given by In the limit when Γ Xα ≈ Γ(X α → gg) the dependence of the cross section (16) on Γ(X α → gg) disappear and its value is determined by the partial decay width Γ(X α → γγ) as one could naively expect. In this case, as it was pointed out in [10], one can obtain σ(pp → γγ) ≈ 8 fb at Then the cross section σ γγ ≈ σ(pp → γγ) for arbitrary partial decay widths of X α → γγ can be approximately estimated as where the branching ratios associated with the decays of exotic states into gluons g and vector bosons V (V = γ, W ± , Z) are given by In Eqs. (20) Γ(X α → gg) and Γ(X α → V V ) are partial decay widths that correspond to the exotic state decays into a pair of gluons and a pair of vector bosons respectively whereas Γ Xα is a total decay width of this state.

One scalar/pseudoscalar case
Let us now consider the scenario when one of the scalar/pseudoscalar exotic states (N 1 or A 1 ) has a mass which is rather close to 750 GeV. From Eqs. (13)- (15) and (17) it follows that the diphoton decay rates of these new bosons and the corresponding signal strength depend very strongly on the values of the Yukawa coulings λ α1 and κ i1 . On the other hand the growth of these Yukawa couplings at low energies entails the increase of their values at the Grand Unification scale M X resulting in the appearance of the Landau pole that spoils the applicability of perturbation theory at high energies (see, for example [172]). The requirement of validity of perturbation theory up to the scale M X sets an upper bound on the low energy value of λ α1 and κ i . In our analysis we use two-loop SM RG equations to compute the values of the gauge couplings at the scale Q = 2 TeV. Above this scale we use two-loop RG equations for the gauge couplings and one-loop RG equations for the Yukawa couplings including the ones given by Eq. (11) to analyse the RG flow of these couplings. In the simplest case when λ α1 = κ i1 our numerical analysis indicates that the values of these couplings at the scale Q = 2 TeV should not exceed 0.6. The upper bound on the coupling λ α1 becomes less stringent when κ i1 are small. In the limit when all κ i1 vanish the value of λ 11 = λ 21 has to remain smaller than 0.81 to ensure the applicability of perturbation theory up to the GUT scale. Although in this case Γ(A 1 → γγ) and Γ(N 1 → γγ) attain their maximal value the production cross sections of exotic states N 1 or A 1 are negligibly small since they are determined by the low-energy values of κ i1 . The upper    bounds on κ i1 can be also significantly relaxed when λ 11 = λ 21 = 0. If this is a case then the requirement of the validity of perturbation theory implies that κ 11 = κ 21 = κ 31 0.79. However in this limit the diphoton production rate associated with the presence A 1 or N 1 is again negligibly small because the corresponding partial decay width vanish. Thus in this section we focus on the scenario with λ α1 = κ i1 = 0.6. This choice of parameters guarantees that the production cross sections of N 1 and A 1 as well as their partial decay width can be sufficiently large.
In Figs. 1a and 1b the dependence of the branching ratios of the exotic pseudoscalar and scalar states on the masses of exotic quarks is examined. To simplify our analysis the masses of all exotic quarks are set to be equal while the masses of all inert Higgsinos are assumed to be around 400 GeV. From Fig. 1a and 1b it follows that the exotic pseudoscalar and scalar states decay predominantly into a pair of gluons when the masses of exotic quarks µ D are below 1 TeV. Moreover if µ D is close to 400 − 500 GeV all other branching ratios are negligibly small. With increasing µ D the branching ratio of the exotic pseudoscalar (scalar) state decays into gluons decreases whereas the branching ratios of the decays of this state into W + W − , ZZ, γγ and γZ increase. The branching ratios of A 1 (N 1 ) → W W and A 1 (N 1 ) → ZZ are the second and third largest ones. The branching ratio of A 1 (N 1 ) → γγ is considerably smaller but still larger than A 1 (N 1 ) → γZ. Although the branching ratios of A 1 (N 1 ) → W W and A 1 (N 1 ) → ZZ can be a substantially bigger than the branching ratio A 1 (N 1 ) → γγ their experimental detection is more problematic because W and Z decays mainly into quarks. When µ D is around 1 TeV the branching ratio of A 1 (N 1 ) → gg is still the largest one and constitutes about 75%(80%) while for µ D ≃ 2 TeV the branching ratios of A 1 (N 1 ) → gg and A 1 (N 1 ) → W W become comparable.
In Fig. 1c and 1d we explore the dependence of the partial decay widths associated with the decays of the exotic pseudoscalar and scalar states into a pair of photons on the masses of exotic quarks and inert Higgsinos µ Hα . One can see that these decay widths decrease very rapidly with increasing µ Hα . The dependence on the masses of exotic quarks is weaker because these states carry small electric charges ±1/3. Since here we assume that κ i1 /µ D i and λ α1 /µ Hα have the same sign the growth of either exotic quark masses or µ Hα results in the reduction of the corresponding decay rate. When µ D is larger than 1.5 TeV the dependence of the partial decay widths under consideration becomes rather weak. From Fig. 1c and 1d it is easy to see that the partial width of the decays A 1 → γγ is substantially larger than the one associated with N 1 → γγ leading to the larger value of the cross sections σ(pp → A 1 → γγ) as compared with σ(pp → N 1 → γγ).
In our analysis we use Eq. (19) to estimate the values of the cross sections σ(pp → A 1 → γγ) and σ(pp → N 1 → γγ) at the 13 TeV LHC. The results of our investigation are shown in Figs. 1e and 1f. In the case of scalar exotic states with mass 750 GeV this cross section tends to be substantially smaller than 1 fb. The presence of 750 GeV exotic pseudoscalar can lead to the considerably stronger signal in the diphoton channel. When all exotic quarks have masses around 400−500 GeV the corresponding cross section can reach 2−3 fb. Somewhat stronger signal can be obtained if we assume that both scalar and pseudoscalar exotic states have masses which are close to 750 GeV. In this case the sum of the cross sections σ(pp → A 1 → γγ)+σ(pp → N 1 → γγ) can reach 4.5 fb if exotic quarks have masses about 400 GeV. The existence of two nearly degenerate resonances may also explain why the analysis performed by the ATLAS collaboration leads to the relatively large best-fit width which is about 45 GeV. Unfortunately, the cross sections mentioned above decreases substantially with increasing exotic quark masses. Indeed, if µ D 1 TeV the sum of the cross sections σ(pp → A 1 → γγ) + σ(pp → N 1 → γγ) does not exceed 2 fb. These cross sections continue to fall even for µ D 1.5 TeV when the corresponding partial decay widths are rather close to their lower saturation limits because the branching ratios associated with the decays of A 1 and N 1 into a pair of gluons decrease with increasing µ D .

Two degenerate scalar/pseudoscalar case
Now let us assume that there are two superfieldsŜ 1 andŜ 2 that have sufficiently large Yukawa couplings to the exotic quark and inert Higgsino states and can contribute to the measured cross section pp → γγ. In other words we assume that scalar and pseudoscalar components of both superfields can have masses around 750 GeV. Naively one may expect that this could allow to enhance the theoretical prediction for the cross section pp → γγ. Again we start from the simplest case when all Yukawa couplings are the same. Then the numerical analysis indicates that in this case the requirement of the validity of perturbation theory up to the scale M X sets even more stringent upper bound on the low energy value of the Yukawa couplings as compared with the one scalar/pseudoscalar case. Indeed, using the one-loop RG equations (11) and twoloop RG equations for the gauge couplings one obtains that λ α1 = κ i1 = λ α2 = κ i2 = λ 0 0.43. Smaller values of the Yukawa couplings do not affect the branching ratios of A 1 and N 1 . Moreover A 2 and A 1 as well as N 2 and N 1 have basically the same branching ratios. This is because partial decay widths of A 1,2 and N 1,2 as well as the corresponding total widths are proportional to λ 2 0 . As a consequence in the leading approximation branching ratios do not depend on λ 0 (see Fig. 2a and 2b ). On the other hand as one can see from Fig. 1c, 1d, 1e and 1f the partial decay widths of A 1,2 → γγ and N 1,2 → γγ as well as the cross sections σ(pp → A 1,2 → γγ) and σ(pp → N 1,2 → γγ) are reduced by factor 2 because of the smaller values of the Yukawa couplings. If all exotic states A 1 and A 2 as well as N 1 and N 2 are nearly degenerate around 750 GeV so that their distinction is not possible within present experimental accuracy, then the superpositions of rates from these bosons basically reproduces the corresponding rates in the one scalar/pseudoscalar case (see Figs. 1e, 1f, 2e and 2f). Thus, it seems rather problematic to achieve any enhancement of the signal in the diphoton channel in the scenario when all Yukawa couplings are equal or reasonably close to each other.

Maximal mixing scenario
Following on from the discussion in the previous subsection, there is one case when a modest enhancement of the signal in the diphoton channel can be achieved. This happens in the socalled maximal mixing scenario when the masses of exotic scalars as well as the masses of exotic pseudoscalars are rather close to 750 GeV and the breakdown of SUSY gives rise to the mixing of these states preserving CP conservation. In this case one can expect that the mixing angles between CP-odd exotic states and CP-even exotic states tend to be rather large, i.e.about ±π/4, because these bosons are nearly degenerate. To simplify our analysis here we set these angles to be equal to π/4. Then the scalar components of the superfields S 1 and S 2 can be expressed in terms of the mass eigenstates N 1 , N 2 , A 1 and A 2 as follows In addition we assume that only superfield S 1 couples to the inert Higgsino states, i.e. λ α2 = 0, and only superfield S 2 couples to the exotic quarks, i.e. κ i1 = 0. In this limit the requirement of the validity of perturbation theory up to the scale M X implies that λ α1 = λ 0 0.8 and κ i2 = κ 0 0.79. Setting GeV one can obtain simple analytical expressions for the partial decay widths of N 1 , A 1 , N 2 and A 2 into a pair of photons Assuming, that κ 0 /µ D and λ 0 /µ D have the same sign, Eqs. (22) and (23) are very similar to the ones which was used before for the calculation of the corresponding partial decay widths in one scalar/pseudoscalar case. Because the expressions for other partial decay widths are also very similar the branching ratios shown in Figs. 3a and 3b are almost the same as in Figs. 1a and 1b. At the same time in the case of N 2 and A 2 destructive interference between the contributions of exotic quarks and inert Higgsinos occurs. This leads to the suppression of the diphoton partial decay width. As a consequence when exotic quarks are lighter than 1 TeV the branching ratios of the decays N 2 → γγ and A 2 → γγ are the lowest ones (see Figs. 3c and 3d).
As before from Fig. 3 it follows that all exotic states N 1 , A 1 , N 2 and A 2 decay mainly into a pair of gluons. The corresponding branching ratio decreases with increasing µ D because c 3α andc 3α diminish. The branching ratios of the decay of these states into W W and ZZ are the second largest and third largest ones. These branching ratios are substantially larger than the ones associated with the decays of exotic states into γγ and γZ. In the case of N 2 and A 2 the branching ratios of the decay of these states into W W can be an order of magnitude larger than the branching ratios of N 2 → γγ and A 2 → γγ. Nevertheless the observation of the decays of N α and A α into pairs of W W and ZZ tend to be more problematic since W and Z decay mostly into quarks. All branching ratios of the exotic scalar and pseudoscalar decays except the largest one grow with increasing µ D . As a result for µ D ≃ 2 TeV the branching ratios of A α (N α ) → gg and A α (N α ) → W W become sufficiently close.
The dependence of the partial decay widths and the corresponding cross sections at the 13 TeV LHC associated with the decays of the exotic pseudoscalar and scalar states into a pair of photons on the exotic quark masses is shown in Fig. 4. The results of our calculations for N 1 and A 1 are very similar to the ones obtained in the one scalar/pseudoscalar case (see Fig. 2e and 2f). The partial decay widths and the cross sections σ(pp → A 1 (N 1 ) → γγ) are just a bit smaller since the Yukawa couplings of A 1 and N 1 to the exotic quarks and inert Higgsino states are slightly smaller. They decrease with increasing the masses of exotic quarks µ D as before. On the contrary, the partial decay widths of N 2 → γγ and A 2 → γγ increase with increasing the exotic quark masses for fixed values of inert Higgsino masses because of the destructive interference mentioned above. They attain their maximal values for µ D ≫ 1 TeV when the contribution of the exotic quarks to the partial decay widths become vanishingly small. The cross sections σ(pp → A 2 (N 2 ) → γγ) also increase with increasing exotic quark masses when µ D 700 GeV. However if exotic quarks are considerably heavier than 1 TeV then these cross sections become smaller for larger µ D since the branching ratios of A 2 (N 2 ) → gg diminish.
The sums of the cross sections σ(pp → N 1 → γγ)+σ(pp → N 2 → γγ) and σ(pp → A 1 → γγ)+ σ(pp → A 2 → γγ) that correspond to the case when all exotic scalar and pseudoscalar states have masses around 750 GeV decreases with increasing µ D (see Figs. 4c and 4d). At large values of the exotic quark masses these cross sections are bigger than the ones in the one scalar/pseudoscalar case shown in Fig. 1e and 1f. This is because the requirement of the validity of perturbation theory up to the scale M X allows for larger values of λ α1 in the maximal mixing scenario as compared with the one scalar/pseudoscalar case. From Figs. 4c and 4d one can see that the sum of all cross section that includes contributions of all scalar and pseudoscalar states with masses around 750 GeV changes from 4.5 fb to 3 fb when the exotic quark masses vary from 400 GeV to 1 TeV. The presence of such nearly degenerate states in the particle spectrum may also provide an explanation why the value of the best-fit width of the resonance obtained by ATLAS collaboration is so large.

Conclusions
In this paper we have proposed a variant of the E 6 SSM in which the third singlet S 3 breaks the gauged U (1) N above the TeV scale, which predicts a Z ′ N , vector-like colour triplet and charge ∓1/3 quarks D,D, and two families of inert Higgsinos, all of which should be observed at LHC Run 2, plus the two lighter singletsŜ 1,2 with masses around 750 GeV which are candidates for the recently observed diphoton excess. We have calculated the branching ratios and crosssections for the two scalars N 1,2 and two pseudoscalars A 1,2 associated withŜ 1,2 , including possible degeneracies and maximal mixing, subject to the constraint that their couplings remain perturbative up to the unification scale.
Our results show that this variant of the E 6 SSM with two nearly degenerate pseudoscalars A 1,2 with masses around 750 GeV, may give rise to cross sections of pp → γγ that can be as large as about 3 fb providing that the inert Higgsino states have masses around 400 GeV, while the three generations of D,D are lighter than about 1 TeV. If the two nearly denegerate scalars N 1,2 also have masses around 750 GeV, then these cross-sections may be further boosted by about 1 fb, assuming that they are at present unresolvable. The existence of nearly degenerate spinless singlets provides an explaination for why the best-fit width of the 750 GeV resonance obtained by the ATLAS collaboration is apparently so large, i.e. about 45 GeV. However further data from Run 2 should begin to resolve the two separate pseudoscalar states A 1,2 (plus perhaps the two scalar states N 1,2 ).
Finally we emphasise that the three families of light vector-like D-quarks around 1 TeV and two families of inert Higgsinos around 400 GeV, although not currently ruled out because of their non-standard decay patterns, should be observable in dedicated searches at Run 2 of the LHC. The Z ′ N gauge boson also remains a prediction of the E 6 SSM. In addition, the proposed variant E 6 SSM also predicts further decay modes of the 750 GeV resonance into W W , ZZ and γZ that might be possible to observe in the Run 2 at the LHC.