PHYS08200604017 Manimala Mitra - Homi Bhabha National Institute

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Decay modes Σ ± m 1 Σ ± m 2 Σ ± m 3 ν m H ± 0.381 0.475 0.475 e ± mA 0 0.251 2.30×10 −6 0.0 µ ± m A0 2.31×10 −6 0.126 0.126 τ m ± A0 2.31×10 −6 0.126 0.126 e ± mh 0 0.37 2.51×10 −6 0.0 µ ± m h0 3.39×10 −6 0.137 0.137 τ m ± h0 3.39×10 −6 0.137 0.137 Table3.4: DecaybranchingfractionsofΣ ± m 1 , Σ ± m 2 andΣ ± m 3 forM h 0=70,M H 0=150,M H ± = 170 GeV and M A 0 = 140 GeV. We have taken model parameters M 1 = 300 GeV and M 2 = M 3 = 600 GeV. Decay modes Σ 0 m 1 Σ 0 m 2 Σ 0 m 3 e ∓ m H± 0.381 4.35×10 −6 0.0 µ ∓ mH ± 3.51×10 −6 0.238 0.238 τm ∓H± 3.51×10 −6 0.238 0.238 ν m A 0 0.251 0.252 0.252 ν m h 0 0.368 0.272 0.272 Table3.5: DecaybranchingfractionsofΣ 0 m 1 , Σ 0 m 2 andΣ 0 m 3 forM h 0=70,M H 0=150,M H ± = 170 GeV and M A = 140 GeV. We have taken model parameters M 1 = 300 GeV and M 2 = M 3 = 600 GeV. the Higgs with the leptons and quarks are given in Appendix B. The interaction of Higgs fields with the gauge fields comes from the Higgs kinetic terms and is the same as the general two Higgs doublet model. Possible decay channels for the charged Higgs involve the W ± and the neutral CP even Higgs. In the two Higgs doublet model, the W ± −H ∓ −H 0 coupling is proportional to sin(β −α), whereas W ± −H ∓ −h 0 coupling is proportional to cos(β − α) [19]. In Appendix A, we have shown how constraint from neutrino mass drives sinα ∼ sinβ ∼ 10 −6 . Therefore, in our model H ± → W ± H 0 is always suppressed, irrespective of the Higgs mass. In fact, the only decay channel possible for the charged Higgs in our model is H ± → W ± h 0 , for which the decay branching fraction BR(H ± → W ± h 0 ) = 1.0. (3.79) The W ± next decay into either q m q ′ m pairs or l ± mν m pairs. The branching fractions of the neutral Higgs h 0 , H 0 and A 0 are given in Table. 3.6 and also in Table. 3.7. Though H 0 is almost never produced through heavy fermion decays in our model, we have included 62
Decay modes h 0 H 0 A 0 b m¯bm 0.89 0.87 0.87 τ m¯τ m 0.07 0.09 0.09 c m¯c m 0.04 0.04 0.04 Table 3.6: Decay branching fractions of h 0 , H 0 and A 0 for M h 0 = 40 GeV, M H 0 = 150 GeV, and M A 0 = 140 GeV. Decay modes h 0 b m¯bm 0.88 τ m¯τ m 0.08 c m¯c m 0.04 Table 3.7: Decay branching fractions of h 0 , H 0 and A 0 for M h 0 = 70 GeV. them in the table for completeness. We find that the neutral Higgs decay to b m¯bm pairs almost 88-89% of the times for M h 0 = 70,40 GeV respectively. The decays to τ m¯τ m and c m¯c m happen less than few percent of the times. In our following sections where we look for collider signatures, we will consider h 0 decays to only b m¯bm and τ m¯τ m pairs. Finally, a short discussion on direct production of h 0 , without involving the heavy fermion decays, is in order. In this work we have considered one of the cases where the lightest Higgs mass as low as 40 GeV. This might appear to be a cause of concern, given that such a Higgs was not observed at LEP. However, it is easy to see that this Higgs mass is not excluded by the direct Higgs searches at LEP-2. This is because the coupling corresponding to Z − Z − h 0 vertex is given by (gM Z /cosθ w )sin(β − α). Since in our model sin(β−α) isalmost zero, the LEP-2 boundonHiggs mass does not pose any serious threat to our model, irrespective of the mass of h 0 . 3.7 Displaced h 0 Decay Vertex Amongst themost significant difference ofour model with theusual type-III seesaw model are the decay lifetimes of the heavy fermions and h 0 . The total decay rate for 300 GeV Σ 0 m is about 10 −2 GeV. This gives the corresponding rest frame lifetime as 10 −13 cm. The lifetime for Σ ± m is similar. One can check that for the usual one Higgs doublet models, the rest frame lifetime for the heavy fermions is ≃ 0.5 cm [15] for m ν = 0.1 eV and M Σ ∼ 100 GeV, which is rather large. The authors of [15] therefore proposed that the displaced decay vertex ofheavy fermioncould beatypical signatureoftheoneHiggstype- 63
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Neutrinos and Some Aspects of Physi
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Declaration This thesis is a presen
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Acknowledgments First and foremost,
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iii
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trino masses are bounded within 0.1
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softly broken Z 2 symmetry, the mas
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tribimaximal mixing in the neutrino
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Bibliography [1] Two Higgs doublet
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Contents 1 Introduction 1 1.1 Stand
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6.2.2 Charged Lepton Masses and Mix
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Chapter 1 Introduction 1.1 Standard
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For positive µ 2 and λ, the Higgs
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type of Yukawa interaction between
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interaction with the Higgs as λ f
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where ˆΦ is the MSSM chiral super
Page 39: (2004); A. Ghosal, hep-ph/0304090;
Page 44 and 45: active flavor. In recent years, sev
Page 46 and 47: Figure 2.1: The possible neutrino s
Page 48 and 49: Majorana mass term breaks lepton nu
Page 50 and 51: The kinetic term of the Higgs tripl
Page 52 and 53: ight handed neutrino N R can be exa
Page 54 and 55: alternating group which is not a di
Page 56 and 57: The group contains two one-dimensio
Page 58 and 59: from neutral-current interactions i
Page 60: [31] K. S. Babu and R. N. Mohapatra
Page 64 and 65: of producing the heavy fermion trip
Page 66 and 67: where Σ ± Ri = Σ1 Ri ∓iΣ2 Ri
Page 68 and 69: while U ν diagonalizes m ν and ˜
Page 70 and 71: It is evident that the masses of th
Page 72 and 73: 0.001 0.001 0.0001 0.0001 U e3 1e-0
Page 74 and 75: if we neglect terms proportional to
Page 76 and 77: calculations for lepton flavor viol
Page 78 and 79: fb. Therefore, it is obvious that t
Page 80 and 81: Σ − -> e m 1 m h 0 Σ − -> e m
Page 82 and 83: We can also see that for Σ − m 1
Page 84 and 85: the sinα term. However, decay to h
Page 86 and 87: Σ − m 1 ->ν m1 W Σ 0 m 1 ->ν
Page 88 and 89: Γ 2HDM (Σ 0 m → ν m H 0 ) ≃
Page 92 and 93: III seesaw model. Clearly, for our
Page 94 and 95: Sl no Channels Effective cross-sect
Page 96 and 97: • The other dominant decay channe
Page 102 and 103: 3.9 Conclusions The seesaw mechanis
Page 104 and 105: Appendix A: The Scalar Potential an
Page 106 and 107: B: The Interaction Lagrangian B.1:
Page 108 and 109: C H0 ,L 1√ ll 2 (T 11Y † l S 11
Page 110 and 111: c Z,L ll c Z,L lΣ − c Z,L Σ −
Page 112 and 113: Bibliography [1] S. Weinberg, Phys.
Page 114: Lett. B 615, 231 (2005); Phys. Rev.
Page 118 and 119: violating λ ′′ coupling are co
Page 120 and 121: neutralino-neutrinomassmatrixandins
Page 122 and 123: 4.3 Symmetry Breaking In this secti
Page 124 and 125: +(M 2 +m 2 Σ )ũ2 + ∑ m 2˜ν i
Page 126 and 127: Here M 1,2 are the soft supersymmet
Page 128 and 129: is violated, we have neutrino-neutr
Page 130 and 131: (M 1,2 ,M,µ,Y Σi ,v 1,2 ,ũ,u i )
Page 132 and 133: In our model in addition to the sta
Page 134 and 135: 4.8 Conclusion In this work we have
Page 136 and 137: Y Σi √2 ĤuˆΣ 0 0c Rˆν L i
Page 138 and 139: while the parameter α 1 is α 1 =
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Bibliography [1] S. Roy and B. Mukh
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[15] M. C. Gonzalez-Garcia and J. W
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ν i A Σi • ˜ν i h,H,A × χ
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118
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of the form ⎛ ⎞ A B B m ν =
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triplet representation of A 4 , l =
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m 0 =0.016 m 0 =0.024 m 0 =0.032 2
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Higgs Neutrino mass matrix Eigenval
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5.3. The deviation of the mixing an
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Sin 2 θ 12 Sin 2 θ 13 Sin 2 θ 23
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Figure 5.5: Scatter plot showing th
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Figure 5.6: Same as Fig. 5.5 but fo
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mass matrix is then given as ⎛ m
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Bibliography [1] M. C. Gonzalez-Gar
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140
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142
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a way that the residual µ−τ sym
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where Λ is the cut-off scale of th
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m 2 . The eigenvectors are given as
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For λ ≃ 2 × 10 −2 ≃ λ2 c 2
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2 2 2 1 1 1 y 2 0 y 3 0 y 4 0 -1 -1
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0.08 0.25 0.06 0.2 10 -3 m νee (eV
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We show the values of |U e3 | ≡ s
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while the branching ratio for this
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6.4 The Vacuum Expectation Values I
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where we have defined B = (b+f 1 +f
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VEV alignments. Another way the VEV
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(2006); M. Maltoni, T. Schwetz, M.
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168
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metric standard model in chapter 1.
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mally two. However the R-parity vio
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sector contains the exact/approxima
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PHYS08200604017 Manimala Mitra - Homi Bhabha National Institute

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