Bled Workshops in Physics Vol. 18, No. 2 A Proceedings to the 20th Workshop What Comes Beyond ... (p. 56) Bled, Slovenia, July 9-20, 2017 5 AF = 2 in Neutral Mesons From a Gauged SU(3)F Family Symmetry A. Hernandez-Galeana * Departamento de Física, ESFM - Instituto Politécnico Nacional. U. P. "Adolfo Lopez Mateos". C. P. 07738, Ciudad de Mexico, Mexico Abstract. Within a broken local gauge vector-like SU(3)F family symmetry, we study some AF = 2 processes induced by the tree level exchange of the new massive horizontal gauge bosons, which introduce flavor-changing couplings. We find out that some of the dangerous FCNC processes, like for instance; Ko — Ko , Do — Do mixing, may be properly suppressed if the first stage of the Spontaneous Symmetry Breaking (SSB), SU(3)F —> SU(2)F, occurs at a high scale A ~ 1011 GeV, with the SU(2)F gauge bosons acting on the light families. We provide a parameter space region where this framework can accommodate the hierarchical spectrum of quark masses and mixing and simultaneously suppress properly the contribution to Ko — Ko mixing as well as the OLL and Oeffective operators for the AC = 2 processes. Povzetek. Avtor obravnava procese, pri katerih se druZinsko kvantno stevilo spremeni za 2. Uporabi model, v katerem opise druzinsko kvantno stevilo kvarkov in leptonov z grupo SU3, lokalna umeritvena polja grupe SU3 pa poskrbijo za interakcijo med fermioni, ki nosijo ustrezna kvantna stevila. Masivni umeritveni bozoni dopusčajo sicer nevtralne prehode (FCNC) med fermioni iste družine, vendar so taki prehodi, kot primer navaja mesanje Ko — Ko ter Do — Do, dovolj malo verjetni, ce le pride do spontane zlomitve druzinske simetrije SU(3)F —> SU(2)F pri energiji A ~ 1011 GeV. Poisče območje parametrov, v katerem imajo kvarki opazljive lastnosti. Keywords: Quark and lepton masses and mixing, Flavor symmetry, AF = 2 Processes. Pacs: 14.60.Pq, 12.15.Ff, 12.60.-i 5.1 Introduction Flavor physics and rare processes play an important role to test any Beyond Standard Model(BSM) physics proposal, and hence, it is crucial to explore the possibility to suppress properly these type of flavor violating processes. Within the framework of a vector-like gauged SU(3)F family symmetry model[1,2], we study the contribution to AF = 2 processes[3]-[6] in neutral mesons * E-mail: albino@esfm.ipn.mx 5 AF = 2 in Neutral Mesons From a Gauged SU(3)F Family Symmetry 57 at tree level exchange diagrams mediated by the gauge bosons with masses of the order of some TeV's, corresponding to the lower scale of the SU(3)F family symmetry breaking. The reported analysis is performed in a scenario where light fermions obtain masses from radiative corrections mediated by the massive bosons associated to the broken SU(3)F family symmetry, while the heavy fermions; top and bottom quarks and tau lepton become massive from tree level See-saw mechanisms. Previous theories addressing the problem of quark and lepton masses and mixing with spontaneously broken SU(3) gauge symmetry of generations include the ones with chiral local SU(3)H family symmetry as well as other SU(3) family symmetries. See for instance [7]-[20] and references therein. 5.2 SU(3)f flavor symmetry model The model is based on the gauge symmetry G = SU(3)f SU(3)c < SU(2)l < U(1)y (5.1) where SU(3)F is a completely vector-like and universal gauged family symmetry. That is, the corresponding gauge bosons couple equally to Left and Right Handed ordinary Quarks and Leptons, with gH, gs, g and g' the corresponding coupling constants. The content of fermions assumes the standard model quarks and leptons: = (3,3,2,3 )l , ^ = (3,1,2, —1 )l =(3,3,1,-)R , ¥^(3,3,1, - 2 )R , ¥0 = (3,1,1, -2)f 3)r , V°(3,3,1, —2) where the last entry is the hypercharge Y, with the electric charge defined by Q = T3L + 2 Y. The model includes two types of extra fermions: • Right Handed Neutrinos: ¥VR = (3,1,1, 0)r , introduced to cancel anomalies [21], • and a new family of SU(2)L weak singlet vector-like fermions: UL,UR = (1,3,1,-) , D0,DR = (1,3,1, -2 ) (5.2) 3) , D0,DR = (1,3,1,-3 Vector Like electrons: E°, ER = (1,1,1, -2) and New Sterile Neutrinos: NR,NR = (1,1,1,0) , 58 A. Hernandez-Galeana The particle content and gauge symmetry assignments are summarized in Table 5.1. Notice that all SU(3)F non-singlet fields transform as the fundamental representation under the SU(3)F symmetry. SU(3)f SU(3)c SU(2)l U(1)y 3 3 2 1 3 3 3 1 4 3 ^dR 3 3 1 2 - 3 3 1 2 -1 Cr 3 1 1 -2 ^vr 3 1 1 0 3 1 2 -1 od 3 1 2 +1 ni 3 1 1 0 Ul,r 1 3 1 4 3 Dl,r 1 3 1 2 - 3 El,r 1 1 1 -2 nl,r 1 1 1 0 Table 5.1. Particle content and charges under the gauge symmetry 5.3 SU(3)f family symmetry breaking To implement the SSB of SU(3)F, we introduce the flavon scalar fields: ni, i = 2,3, KA ni = (3,1,1,0)= I n?2) , i = 2,3 Wj with the "Vacuum ExpectationValues" (VEV's): (n2)T = (0,A2,0) , (na)T = (0,0, As). (5.3) It is worth to mention that these two scalars in the fundamental representation is the minimal set of scalars to break down completely the SU(3)F family symmetry. The interaction Lagrangian of the SU(3)F gauge bosons to the SM massless fermions is iLint,SU(3)F = gH (f0 f° f3y /7M- 7 M v+M / I Z2 Y__'2 \ '2 + 2^3 V2 ^2 V2 \ 2 V V2 7M 7M v+M Z1 I Z2 ' 3 2 + 2^3 ^2 V2 /f?\ fo f 2 ZM Z2 3 5 AF = 2 in Neutral Mesons From a Gauged SU(3)F Family Symmetry 59 i Y1 + iY2 where gH is the SU(3)F coupling constant, Zï , Z2 and Y± = ' ^ ' , j = 1,2,3 are the eight gauge bosons. Thus, the contribution to the horizontal gauge boson masses from the VEV's in Eq.(5.3) read • : ^(Y+Y- + Y+Y—) + ^(Z1 + Z2 -2ZTZ3) 2 2 2 • : ^(Y+Y- + Y+Y-) + gH3Al^^ The "Spontaneous Symmetry Breaking" (SSB) of SU(3)F occurs in two stages SU(3)f x GSM ——^ SU(2)F ? x GSM ——^ GSM FCNC ? A3: 5 very heavy boson masses (> 100 TeV's) A2: 3 heavy boson masses (may be a few TeV's). Notice that the hierarchy of scales A3 ^ A2 define an "approximate SU(2) global symmetry" in the spectrum of SU(2)F gauge boson masses. To suppress properly the FCNC like, for instance: ^ —> ey, ^ —> e e e, Ko — Ko, and Do — Do, it is crucial to choose properly the SU(2)F symmetry at the lower scale. Therefore, neglecting tiny contributions from electroweak symmetry breaking, we obtain the gauge boson mass terms. M 2 Y+ Y- + M2 Y+Y- + (M2 + M2 ) Y+Y- + Z2 + 2 1M2 + 4M2 Z2 - 1 (M2)^ Z, Z2 3 2_ '73' (5.4) M2 = 92hA2 m2 = 92hA3 y = M3 = Aa M2 A2 (5.5) 2 2 Zi Z2 Zi m2 M2 — vf Z2 M2 —"Tf m2+4M§ 3 Table 5.2. Zi — Z2 mixing mass matrix Diagonalization of the Zi — Z2 squared mass matrix yield the eigenvalues 60 A. Hernandez-Galeana M- = 2 + Ml - \\(M2 - M2)2 + M2M3 M+ = 2 (M2 + M2 + \(M2 - M2)2 + M^M2 and finally (5.6) (5.7) 72 72 m2 Y+Y- + M2 Y+Y- + (M2 + M2) Y+Y- + M- — + M+ —+ where —_ /'cos * — sin (— —2 sin * cos * ) V — cos * sin * = —— m2 4 + m2(M2 - M2) —1 = cos * —- - sin * —+ , — 2 = sin * — _ + cos * —+ (5.8) (5.9) (5.10) 5.4 Electroweak symmetry breaking For electroweak symmetry breaking we introduction two triplets of SU(2)L Higgs doublets, namely; and the VEV?s where = (3,1,2,-1) = 1 (ou) = — fVui ^ ) V2y° ®d = (3,1,2, +1), (®d) = ( (®2d) I , The contributions from (®u) and (® d) yield the W and — o gauge boson masses and mixing with the SU(3)F gauge bosons g2 (vU + vdd) W+W- + fc^ (vU + vdd) —0 8 + tiny contribution to the SU(3)F gauge boson masses and mixing with the gauge boson —o , 5 AF = 2 in Neutral Mesons From a Gauged SU(3)F Family Symmetry 61 vU = vL + v2u + v3u ,v d = v2d + v2d + v3d • So, if we defme Mw = 1 gv we may write v = \JvU + vd « 246 GeV. 5.5 Fermion masses 5.5.1 Dirac See-saw mechanisms The scalars and fermion content allow the gauge invariant Yukawa couplings Hu UR + hiu lUR ni UO + Mu UL UR + h.c (5.11) Hd ®d DR + hid ni DO + Md DO DR + h.c (5.12) He if ®d ER + hie ifR ni E° + Me E° ER + h.c (5.13) Hv if NR + hiv iRni Nf + Mnd N° NR + h.c (5.14) hL (NL)c + mL NR (N°)c + h.c (5.15) hiR ^V vr ni (NR)c + mR NR (NR)c + h.c (5.16) MU , Md , Me , Mnd , mL , mR are free mass parameters and Hu, Hd, He, Hv, hiu, hid, hie, hiv, hL, hiR are Yukawa coupling constants. When the involved scalar fields acquire VEV's, we get in the gauge basis 1L RT = (e°, m°,t°, EO)L,R, the mass terms 10M°1R + h.c, where M0 = /0 0 0 hvi\ 0 0 0 hv2 0 0 0 hv3 \0 h2A2 h3A3 M J /0 0 0 ai\ 0 0 0 a2 0 0 0 a3 V0 b2 b3 Mj (5.17) M0 is diagonalized by applying a biunitary transformation ^LR = V0 R xL,R. Using the possible parametrizations for the orthogonal matrices and V£ are written explicitly in the Appendix A, Using one obtains y°TM0 V° = Diag(0,0, -A3,A4) (5.18) VltM°M°t V° = VrtM°tM° VR = Diag(0,0,A3,A4) . (5.19) where A3 and A4 are the nonzero eigenvalues defined in Eqs.(5.56-5.58), A4 being the fourth heavy fermion mass, and A3 of the order of the top, bottom and tau 62 A. Hernandez-Galeana mass for u, d and e fermions, respectively. We see from Eqs.(5.18,5.19) that from tree level the See-saw mechanism yields two massless eigenvalues associated to the light fermions: it is worth to mention that the Yukawa couplings in Eqs.5.11-5.16 are invariant under the global symmetry U(1 )B x U(1 )Y x U(1 )a x U(1 , where B is the baryon number, Y is the hypercharge, and U(1 )a, U(1 are two additional symmetries, and one of them could play the role of a Peceei-Quinn symmetry to address the strong CP problem[22]. 5.6 One loop contribution to fermion masses After tree level contributions the first two generations remain massless. Therefore, in this scenario light fermion masses, including neutrinos, may get small masses from radiative corrections mediated by the SU(3)F heavy gauge bosons. The one loop diagram of Fig. 1 gives the generic contribution to the mass term mtj ë?Le?R, where Y i i < nk > < > Fig. 5.1. Generic one loop diagram contribution to the mass term my e?Le°R 2 mij = cy^ Y m° (V0)ik(V0)jkf(My,mk) ,