Phenomenology of sequestered mass generation

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1 Department of Physics, University of Cincinnati, Cincinnati, Ohio 4522, USA I discuss aspects of the phenomenology of a novel class of two Higgs doulet models (2HDMs). One Higgs provides the ulk of the masses of the weak gauge osons and the third generation fermions, while the second Higgs is responsile for the masses of the lighter fermion flavors. The phenomenology of this setup differs sustantially from well studied 2HDMs with natural flavor conservation, flavor alignment, or minimal flavor violation. Flavor violating Higgs couplings generically arise in a controlled way. New production mechanisms and decay modes for the heavy scalar, pseudoscalar and charged Higgs involving second generation quarks can ecome dominant. 38th International Conference on High Energy Physics 3-0 August 206 Chicago, USA Speaker. c Copyright owned y the author(s) under the terms of the Creative Commons Attriution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).

2 . Introduction In the Standard Model (SM) of particle physics, the Higgs oson is the only source of electroweak symmetry reaking and responsile for the masses of all other massive SM particles. Measurements of Higgs production and decay are overall in good agreement with SM predictions and indicate that the masses of the weak gauge osons and also the third generation fermions are indeed largely due to the Higgs []. However, confirming the Higgs as the origin of the light flavors mass is experimentally very challenging, due to the tiny Yukawa couplings involved. An alternative approach to uncover the origin of masses of the light flavors is to assume that it is not the Higgs and explore the implied phenomenology. In [2] we proposed a framework, where the origin of the first and second generation fermions is not the Higgs oson, ut an additional source of electro-weak symmetry reaking (see also [4, 5]). Argualy the simplest realization of this framework is a two Higgs doulet model (2HDM): one Higgs doulet couples to the fermions with rank Yukawa couplings λ, providing mass only for the third generation, while the other Higgs also couples to first and second generation fermions with Yukawa couplings λ. We will consider the following textures for the lepton Yukawa couplings λ l v 0 0 m τ, λ l m e m e m e 2 v m e m µ m µ m e m µ m µ, (.) where v and v are the vacuum expectation values (vevs) of the two Higgs doulets. Analogous textures can e chosen for the up-quark Yukawas. To achieve quantitative agreement with the oserved CKM mixing requires to adapt the corresponding down-quark Yukawa textures slightly (see [2, 3] for details). Generically, such a framework leads to flavor changing neutral currents already at tree level. However, the rank Yukawa couplings preserve a SU(2) 5 flavor symmetry acting on the first two generations of fermions. In the 2HDM setup the symmetry is only roken y the λ Yukawa couplings of the second doulet and flavor transitions etween the first and second generations are protected. Therefore, the most stringent flavor constraints from µ e, s d, and c u transitions can e controlled. The outlined 2HDM setup shows very distinct phenomenology. In contrast to 2HDMs with natural flavor conservation [6], flavor alignment [7, 8], or minimal flavor violation [9], the couplings of the Higgs osons to fermions are not proportional to the fermion masses. Non-standard production and decay modes of the heavy Higgs osons involving light quark generations ecome relevant. Also flavor changing neutral Higgs couplings involving the third generation lead to interesting phenomenological implications. The following discussion is mainly ased on [3] (see also [0, ] for recent related studies). 2. Phenomenology of the 25 GeV Higgs We identify the lightest neutral scalar h of the 2HDM with the 25 GeV Higgs oson. Its couplings are in general modified with respect to SM expectations, and measurements of Higgs rates at the LHC can e used to constrain the parameter space of the model.

3 30 2HDM type I 0 t Β Figure : Allowed region in the cos(β α) vs. tanβ plane from measurements of the 25 GeV Higgs rates at the LHC. The dark green and light green regions correspond to the σ and 2σ allowed regions, allowing the O(m 2nd /m 3rd ) terms in the relevant Higgs couplings to float etween 3m 2nd /m 3rd and +3m 2nd /m 3rd. The dashed line corresponds to the 2σ contour in a 2HDM type. As in any other 2HDM, the coupling of h to the weak gauge osons W and Z is universally suppressed y a factor cos(β α), where α is the mixing angle of the two neutral scalar osons and tanβ = v/v is the ratio of the vevs of the two Higgs doulets. The modifications to the couplings to third generation fermions read Y t t Y Y τ Yτ SM c α, (2.) s β where c x = cosx, s x = sinx. In the aove expression we show the leading term and neglect corrections of the order of m 2nd /m 3rd. The modification of the third generation couplings coincide with those in a 2HDM type. The couplings of the first and second generation are instead modified y Y c Yc SM Y s s Y µ µ Y u u Y d d Y e Ye SM s α, (2.2) c β where we neglected corrections of the order m 2nd /m 3rd (for second generation couplings) and m st /m 3rd (for first generation couplings). For α = 0, i.e. in the asence of mixing etween the scalar components of the two doulets, h does not couple to the first and second generation. Away from the decoupling limit, cos(β α) 0, the couplings can deviate sustantially from SM values. Fig. shows the result of a χ 2 fit to the Higgs signal strengths from [] comined with the ounds on h µ + µ from [2]. The dark (light) green region is allowed y the LHC results at the σ (2σ) level. Shown for comparison is also the 2σ constraint in a 2HDM type (dashed contour). Away from the decoupling limit, h generically also acquires flavor violating couplings. We generically expect lepton flavor violating Higgs decays of the order of Br(h τµ) m2 µ 3m 2 0 3, Br(h τe) m2 e 3m 2 0 7, Br(h µe) m2 em 2 µ 3m 2 τm (2.3) 2

4 00 tanβ=50, cos(β-α)=.05 cc ct tanβ=50, cos(β-α)=.05 0 cc+ch σ [p] ggf q+h th VBF m H [GeV] BR m H [GeV] Figure 2: Left: Production cross sections of the heavy scalar H in 3 TeV proton-proton collisions as function of the scalar mass m H for fixed tanβ = 50 and cos(β α) = Right: Branching ratios of the heavy scalar H as function of the scalar mass m H for fixed tanβ = 50 and cos(β α) = While the h τe and h µe decays are well elow the foreseeale experimental sensitivities, h τµ can e at an experimentally accessile level. 3. Phenomenology of the Heavy Higgs Bosons The couplings of the heavy Higgs osons to fermions show a very pronounced flavor nonuniversal structure. For example, for the heavy scalar H we find Y H c c Y s H Ys SM Y H t t Y H µ µ Y H Y H u u ss Y τ H Yτ SM s α, (3.) t β c β Y H d d tt μμ WW Y e H c α Ye SM t β. (3.2) s β In these expressions we neglected corrections of the order m 2nd /m 3rd (for second and third generation couplings) and m st /m 3rd (for first generation couplings). Note that the third generation couplings are suppressed y tanβ, while the couplings to first and second generation are enhanced y tanβ. Correspondingly, the decays of H to the third generation (top, ottom, tau) are not necessarily dominant. For large and moderate tan β, sizale ranching ratios involving charm quarks and muons can e expected. Moreover, novel non-standard production modes of the heavy Higgs osons involving second generation quarks can ecome relevant. The left plot of Fig. 2 shows various production cross sections of H as function of its mass m H for tanβ = 50 and cos(β α) = Production from charm quarks is dominant for large tanβ. The curve laeled cc + ch includes c c H production and production in association with a charm quark cg ch and cg ch. Production from gluon fusion is su-dominant. Production in association with ottom and top quarks is mainly induced y flavor violating couplings, e.g. sg H or cg th. The corresponding cross sections can e at an interesting level. The vector ττ ZZ τμ 3

5 oson fusion production cross section is tiny, as are the cross sections for production in association with vector osons (not shown in the plot). The ranching ratios of H as function of its mass m H are shown in the right plot of Fig. 2 for tanβ = 50 and cos(β α) = The dominant decay modes are c c and the flavor violating ct. The decay into t t can also e sizale. Decays into final states with taus and muons are at the level of few 0 3 to few 0 2. Note that the decay rates into τ + τ and µ + µ are comparale. This is in stark contrast to un-flavored 2HDMs where the ratio of these ranching ratios is determined y the ratio of lepton masses m 2 τ/m 2 µ 300. Decays into gauge osons are typically su-dominant. For the chosen value of cos(β α) = 0.05, the WW and ZZ ranching ratios can reach the 0% level for Higgs masses of around TeV. The production cross sections and ranching ratios of the heavy pseudoscalar A show a very similar ehavior. The main difference are the asence of vector oson fusion production and of production in association with vector osons as well as the asence of decays into WW and ZZ. In contrast to the scalar H, the pseudoscalar A can e produced in association with the light Higgs h and can decay into Zh. The corresponding production cross section and ranching ratio are typically too small to e of phenomenological relevance. Given the distinct production and decay modes discussed aove, the standard searches for heavy Higgs osons at the LHC (H/A τ + τ and H WW/ZZ) have only weak sensitivity to our model. We find that the strongest constraints can currently e derived from searches for di-muon resonances. For tanβ = 50, such searches allow to exclude H and A with masses elow 300 GeV. For lower values of tanβ, the constraints are much weaker. The discussed 2HDM setup predicts a set of novel signatures that can e searched for at the LHC. Among the most interesting signatures are flavor violating Higgs decays pp H/A τ µ with cross sections up to 00 f, and pp H/A tc with cross sections as large as several p. Another very interesting signature are multi top final states pp th/a ttc. A significant fraction of this signature consists of two same sign tops, cg th/a tt c or cg th/a t tc, providing a very clean and distinct signature. Also the charged Higgs oson shows distinct non-standard phenomenology. The dominant production mode is typically production from a cs initial state with cross sections as large as p for a charged Higgs mass of m H ± 500 GeV. Production in association with a top is typically several 0s of f. The main decay mode is not necessarily H ± t ut can e H ± c or H ± cs. The H ± τν decay mode is suppressed, with ranching ratios of few 0 3. The H ± µν decay has comparale ranching ratio. Interesting novel signatures of the charged Higgs include production in association with a top followed y the decay into c or cs: pp th ± tc/s. Searches for di-jet resonances with an associated top might have interesting sensitivities to the discussed framework. 4. Summary and Outlook I discussed the distinct collider phenomenology of a novel class of 2HDMs. One Higgs doulet provides the dominant contriution of the masses of the weak gauge osons and the third generation 4

6 fermions, while the second Higgs doulet is responsile for the masses of the lighter fermion flavors. The properties of the 25 GeV Higgs and the additional heavy Higgs osons differ markedly from other well studied 2HDMs with natural flavor conservation, flavor alignment, and minimal flavor violation. Characteristic signatures include the lepton flavor violating decay h τ µ with ranching ratios possily in reach of the LHC, as well as flavor violating decays of the heavy Higgs osons H/A tc and H/A τµ. Other interesting collider signatures include same sign tops and di-jet resonances with an associated top. Further studies are required to determine the sensitivities of possile dedicated LHC searches for such signatures. Acknowledgements WA acknowledges financial support y the University of Cincinnati. References [] G. Aad et al. [ATLAS and CMS Collaorations], JHEP 608, 045 (206) [arxiv: [hep-ex]]. [2] W. Altmannshofer, S. Gori, A. L. Kagan, L. Silvestrini and J. Zupan, Phys. Rev. D 93, no. 3, 0330 (206) [arxiv: [hep-ph]]. [3] W. Altmannshofer, J. Ey, S. Gori, M. Lotito, M. Martone and D. Tuckler, arxiv: [hep-ph]. [4] D. Ghosh, R. S. Gupta and G. Perez, Phys. Lett. B 755, 504 (206) [arxiv: [hep-ph]]. [5] F. J. Botella, G. C. Branco, M. N. Reelo and J. I. Silva-Marcos, arxiv: [hep-ph]. [6] S. L. Glashow and S. Weinerg, Phys. Rev. D 5, 958 (977). [7] A. Pich and P. Tuzon, Phys. Rev. D 80, (2009) [arxiv: [hep-ph]]. [8] W. Altmannshofer, S. Gori and G. D. Kris, Phys. Rev. D 86, 5009 (202) [arxiv: [hep-ph]]. [9] G. D Amrosio, G. F. Giudice, G. Isidori and A. Strumia, Nucl. Phys. B 645, 55 (2002) [hep-ph/ ]. [0] F. J. Botella, G. C. Branco, M. Neot and M. N. Reelo, Eur. Phys. J. C 76, no. 3, 6 (206) [arxiv: [hep-ph]]. [] M. Sher and K. Thrasher, Phys. Rev. D 93, no. 5, (206) [arxiv: [hep-ph]]. [2] ATLAS Collaoration, ATLAS-CONF