We will review the status of the Higgs boson beyond Standard Model. This proceeding will be focused on the experimental and theoretical status of the Higgs boson in the Composite Higgs models. In particular we will discuss implications on the beyond Standard Model (BSM) Higgs coming from the observed excess at 125 GeV

Azatov, Aleksandr

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The Higgs boson beyond Standard ModelAleksandr Azatov11Dipartimento di Fisica, Università di Roma “La Sapienza"and INFN Sezione di Roma; I-00185 Rome, ItalyDOI: http://dx.doi.org/10.3204/DESY-PROC-2012-02/176We will review the status of the Higgs boson beyond Standard Model. This proceeding willbe focused on the experimental and theoretical status of the Higgs boson in the CompositeHiggs models. In particular we will discuss implications on the beyond Standard Model(BSM) Higgs coming from the observed excess at 125 GeV.1 IntroductionHiggs fields is the only missing element of the Electroweak Symmetry breaking mechanism.With the recent hints from LHC about excess at 125 GeV [1, 2] it becomes crucial to understandthe nature of this candidate for the Higgs boson and the mechanism that stabilizes its mass atthe electroweak scale. One of the most attractive explanations of the Higgs mass stability isgiven in the models, where the Higgs appears as a composite field of some new strong dynamics[3]. However masses of the composite states in such framework are generically around TeV,so that we need additional mechanism to explain, why the Higgs is much lighter than the restof the composite states. Such mass hierarchy can be naturally explained in the models, whereHiggs is a pseudo Nambu-Goldstone boson of some larger global symmetry group[3, 4]. Recentlythis idea attracted more attention because this setup is dual to the extra dimensional modelsin warped geometry[5], where Higgs comes as a fifth component of the five dimensional gaugefield [6]. Generically in such models the rest of the composite resonances are much heavier thanthe Higgs field, which makes them hard to produce directly at the LHC, however their indirecteffects might be seen in the modifications of the Higgs couplings to the Standard Model(SM)fields. Within this framework first hints of new physics might be observed in the deviations ofthe Higgs couplings from their Standard Model expectations. In this note we will review genericpredictions of the composite models as well as current constraints on the Higgs couplings.2 Single Higgs effective theoryAs we argued in the previous section, for the BSM Higgs we expect modifications of the Higgscouplings. To parametrize such interactions the Higgs field h, it is convenient to use Electroweak(EW) chiral lagrangian with all the possible additional interactions involving h[7, 8]. LEPconstraints on ∆ρ parameter force our lagrangian to be symmetric under custodial SU(2)L ×SU(2)R symmetry. Longitudinal polarizations of the W and Z correspond to the Nambu-Goldstone (NG) bosons of SU(2)L×SU(2)R/SU(2)V symmetry breaking, and can be describedDIS 2012 1by the 2× 2 matrixΣ(x) = exp (iσaχa(x)/v) , (1)where σa are the Pauli matrices and v = 246GeV. The scalar h is assumed to be a singlet ofthe custodial SU(2)V . The Lagrangian thus reads:L = −V (h) + L(2) + L(4) + . . . (2)where L(n) includes the terms with n derivatives and V (h) is the potential for h. At the levelof two derivatives one has [7]L(2) =12(∂µh)2 +v24Tr(DµΣ†DµΣ)(1 + 2ahv+ bh2v2+ · · ·)− v√2λuij(u¯(i)L , d¯(i)L)Σ(u(i)R , 0)T (1 + cuhv+ c2uh2v2+ · · ·)+ h.c.+(uR ⇔ dR, cu ⇔ cd) + ((u, d⇔ ν, e), cu ⇔ cl) (3)Standard Model corresponds to the point where all a = b = ci = 1 and c2i = 0 At the level offour derivatives one can write the lagrangian as a sum of operators OiL(4) =∑iOi (4)where Oi are defined in the following wayO1 = Tr[(DµΣ)†(DµΣ)](∂νF1(h))2, O2 = Tr[(DµΣ)†(DνΣ)]∂µ∂νF2(h)OGG = GµνGµν FGG(h), OBB = BµνBµν FBB(h)OW = DµWaµν Tr[Σ†σai←→D νΣ]FW (h), OB = −∂µBµν Tr[Σ†i←→D νΣσ3]FB(h)OWH = iWaµν Tr[(DµΣ)†σaDνΣ]FWH(h), OBH = −i Bµν Tr[(DµΣ)†(DνΣ)σ3]FBH(h)OW∂H =12W aµν Tr[Σ†σai←→D µΣ]∂νFW∂H(h), OB∂H = −12Bµν Tr[Σ†i←→D µΣσ3]∂νFW∂B(h)Fi(h) = α(0)i + α(1)i h+ α(2)i h2 + ... (5)The operators OW , OB contribute to the S parameter and the operators OGG, OBB are impor-tant for the contribution of the Higgs couplings to gluons and photons. Generically all theseoperators have independent coefficients, which have to be determined during the experiment.3 Current constraints on the Higgs couplingsIn this section we will derive the current bounds on the Higgs couplings. Instead of consideringthe whole set of operators presented in the previous section we will focus on the followingscenariocu = cd = cl ≡ c (6)2 DIS 2012and all the operators Oi vanish.1 We will assume that couplings of the Higgs to gluons andphotons are modified only due to the modification of the Higgs couplings to W and t no directcontribution to these vertices. Note that assumption Eq. 6 is realized in type I 2HDM and alsoin the composite Higgs scenarios, where both top and bottom mix with the same representationsof composite group, for example in the models (MCHM4,5) based on the SO(5)/SO(4) cosetwe haveMCHM 4 : a = c =√1− ξMCHM 5 : a =√1− ξ, c = 1− 2ξ√1− ξ , (7)where (ξ = v2f2 ) and f is analogue of pion decay constant. To derive current constraints onthe (a, c) parameters we assumed Bayesian approach and extracted likelihoods following themethod suggested in [8]. The results are presented on the Figure 1.mh =120 , 95%mh =130 , 95%mh =160 , 95%mh = 200 , 95%MCHM4MCHM5øSM0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-3-2-10123acCMS@ S =7 TeV ;b 4.8 fb-1 DFigure 1: Current exclusions in the plane (a, c)for various Higgs masses as obtained with ourmethod: the area to the right of each curve is ex-cluded at 95% CL. These exclusions combine allsearch channels at CMS, with the full 2011 dataset, purple and orange lines indicate MCHM4and MCHM5 contours in the (a, c) planeWe can see that for the Higgs mass above130 GeV large part of the parameter space isexcluded. Also note that for the light Higgsmh = 120, 130 GeV iso-contours are not sym-metric in (c⇔ −c), this is because of the γγchannel where we can probe the relative signbetween a and c due to the interference of thediagrams with loops of W and loops of t.4 Excess at 125 GeVRecently both collaborations ATLAS andCMS reported excess of events at mh ≈ 125GeV, so it is interesting to know what we canlearn about the couplings of this resonancewith the current LHC data. On the Fig. 2 weplotted posterior probability fixed contours inthe (a, c) plane. We can see that so far SMHiggs is well in agreement with the currentdata. Also note that due to the γγ chan-nel probability contours are asymmetric in(c⇔ −c), and there is always a solution withnegative c. Another interesting feature is abig difference between CMS and ATLAS plotsnear the fermiophobic line c = 0. This is dueto the fact that CMS collaboration presentsresults for the exclusive searches in γγ andWW channels. For example, cuts requiring1 Note that this assumption is not as bad as it might seem, because only OGG, OBB , OW,B , OW (B)∂H areimportant for the single Higgs production, however constraints from S parameter require OW,B to be small.Also in the case when Higgs is a pNGB field, operators OGG,(BB) explicitly break shift symmetry and shouldbe suppressed.DIS 2012 368% CL95% CLø99% CL0.0 0.5 1.0 1.5 2.0-3-2-10123acCMS @ s =7 TeV;£ 4.9 fb-1D68% CL95% CLø99% CL0.0 0.5 1.0 1.5 2.0 2.5-3-2-10123acATLAS @ s =7 TeV;£ 4.9 fb-1DFigure 2: Isocontours of 68%, 95%, 99% probability in the (a, c) plane for 125 GeV Higgs comingfrom CMS (left) and ATLAS (right), Standard Model is indicated by startwo extra high pT jets in the forward region in the final state help to select events producedmainly through the vector boson fusion mechanism, this allows us to probe a region of param-eter space in the c = 0 region. This illustrates explicitly, how important exclusive analysis isfor determining Higgs couplings in the future.5 SummaryWe reviewed current status of the BSM Higgs at LHC and analysed current constraints on theHiggs couplings from ATLAS and CMS at 5 fb−1. Even now at low luminosity we can extractsome information about the Higgs couplings, and constrain the parameter space of the compositemodels. This exercise demonstrates that exclusive analysis is essential in understanding thenature of the Higgs boson.References[1] ATLAS Collaboration, “Combined search for the Standard Model Higgs boson using up to 4.9 fb-1 of ppcollision data at sqrt(s) = 7 TeV with the ATLAS detector at the LHC,” arXiv:1202.1408 [hep-ex].[2] CMS Collaboration, “Combination of CMS searches for a Standard Model Higgs boson” CMS-PASHIG-11-032[3] D. B. Kaplan, H. Georgi and S. Dimopoulos, Phys. Lett. B 136, 187 (1984).[4] G. F. Giudice, C. Grojean, A. Pomarol and R. Rattazzi, JHEP 0706, 045 (2007) [hep-ph/0703164].[5] L. Randall and R. Sundrum, Phys. Rev. Lett. 83, 3370 (1999) [hep-ph/9905221].[6] K. Agashe, R. Contino and A. Pomarol, Nucl. Phys. B 719, 165 (2005) [hep-ph/0412089].[7] R. Contino, C. Grojean, M. Moretti, F. Piccinini and R. Rattazzi, JHEP 1005, 089 (2010)[arXiv:1002.1011 [hep-ph]].[8] A. Azatov, R. Contino and J. Galloway, JHEP 1204, 127 (2012) [arXiv:1202.3415 [hep-ph]].4 DIS 2012

The higgs boson beyond standard model

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The Higgs boson beyond Standard Model

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The higgs boson beyond standard model

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