PHYS08200604017 Manimala Mitra - Homi Bhabha National Institute

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Sl no Channels Effective cross-section in fb 1 4b +OSD 33.45 2 4b+l+ ̸ p T 89.60 3 4b+l +2j+ ̸ p T 26.4 4 4b+2l+2j 36.1 5 4b+3l(2l+l ′ )+ ̸ p T 12.04 Table 3.12: Effective cross-sections in fb for M Σ1 = 300 GeV and M h 0 = 70 GeV for the important channels for our model. with effective cross-section of 53.7 fb, or decay into qq ′ giving Σ ± Σ 0 → H ± νh 0 ν → 4b+2j+ ̸ p T , with an effective cross-section of 35.98 fb. • Large effective cross-section in the Σ ± Σ 0 channel is also expected from the following decay chain Σ ± Σ 0 → l ± h 0 l ± H ∓ → 4b+2l+2j, with effective cross-section of 36.12 fb. Both the leptons in this channel come from the heavy fermion decay vertices and carry the flavor information of the model. Choice of a 70 GeV M h 0 does not alter the cross section as can be seen from Table. 3.12. • Σ ± Σ 0 could also decay through the intermediate states H ± νH ± l ∓ . This leads to 20 possible final state particles and collider signatures. These are listed in Table 3.10. However, the only one which has sizable effective cross-section is Σ ± Σ 0 → H ± νH ± l ∓ → 4b+l +4j+ ̸ p T . However, this channel has 4 light quark jets, which is always prone to problems with backgrounds. In Table. 3.12, we have shown the effective cross section for few of the channels considering the Higgs mass M h 0 = 70 GeV, while in the other tables the Higgs mass has been taken as 40 GeV. The choice of the Higgs mass as 70 GeV does not make any significant change in the effective cross sections. Hence we do not repeat the calculation of the effective cross section for all the possible channels for the case of M h 0 = 70 GeV. 72
3.8.3 Backgrounds In Tables 3.8, 3.9 and 3.10 we provided a comprehensive list of collider signature channels for the heavy fermions, and their corresponding effective cross-sections. In the previous subsection we had also discussed some of the most important channels with large effective cross-sections. In Table 3.11 and in Table 3.12 we give a subset of those highlighted in sections 3.8.1 and 3.8.2. These are expected to be the most unambiguous channels, with smallest backgrounds and the largest signal cross-sections. In almost all channels listed in Table 3.11 and in Table 3.12, the final collider signature contains 4 b-jets and a hard lepton coming from the primary heavy fermion decay vertex. In addition, the 4 b-jets come from the h 0 decay vertex which is significantly displaced with respect to the heavy fermion decay vertex. The main source of standard model background for the channels with 4 b-jets and a lepton are the t¯tb¯b modes, which can give multiple b-jets, leptons and missing energy. However, as mentioned many before, the b-jets come from h 0 displaced vertex and should not have any standard model background. Having the hard lepton in the final state further cuts down the background. Therefore, each of these collider channels are expected to have very little to no backgrounds. For a detailed signal to background analysis one requires a detailed simulation for the final state topology, which is outside the scope of this work. Nevertheless we add a few lines discussing qualitatively the possibility of backgrounds for some of the listed channels in Table 3.11. • 4b +OSD: Here the two opposite sign dileptons come from the Σ + Σ − decays. Since the Σ ± are heavy with M Σ ± = 300 GeV, the leptons will be very hard and we can put a cut of p T ∼ > 100 GeV. The displaced h 0 vertex should remove all backgrounds. • 4b + l+ ̸ p T : Here t¯tb¯b does not directly give any background, unless one of the leptons from the final state is missed. However, the p T cut on the hard lepton and the displaced h 0 vertices should effectively remove any residual background. • 4b+l ′ + ̸ p T : Here the p T cut on the lepton cannot be imposed as the lepton here comesfromW ± decay. However, the4b-jetsstillcomefromthedisplaced h 0 vertices and that should anyway take care of killing all backgrounds to a large extent. • 4b+l + 2jet+ ̸ p T : The main background could again come from standard model t¯tb¯b channels. This can also be removed by the displaced h 0 vertex and a cut of p T ∼ > 100 GeV for the lepton. • 4b+2l +2j: Similar to the first case, but with 2 extra jets. • 4b+3l(2l +l ′ )+ ̸ p T : Out of the 3 leptons in this channel, two are hard and one is relatively soft. In addition we have the h 0 displaced vertex. Therefore, this channel is expected to be absolutely background free. 73
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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
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(2004); A. Ghosal, hep-ph/0304090;
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active flavor. In recent years, sev
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Figure 2.1: The possible neutrino s
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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 90 and 91: Decay modes Σ ± m 1 Σ ± m 2 Σ
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 98 and 99: Sl no Channels Effective cross-sect
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 =
Page 140 and 141: Bibliography [1] S. Roy and B. Mukh
Page 142 and 143: [15] M. C. Gonzalez-Garcia and J. W
Page 144 and 145: ν i A Σi • ˜ν i h,H,A × χ
Page 146 and 147: 118
Page 148 and 149: 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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