We introduce a new parametrization of the MNS lepton mixing matrix which separates the hierarchical Grand Unified relations among quarks and leptons. We argue that one large angle stems from the charged leptons, the other from the seesaw structure of the neutral lepton mass matrix. We show how two large mixing angles can arise naturally provided there are special requirements on the Dirac (∆I w = 1/2) and Majorana (∆I w = 0) masses. One possibility is a correlated hierarchy between them, the other is that the ∆I w = 0 Majorana mass has a specific texture; it is Dirac-like for two of the three families.

We contrast the experimental signatures of low energy supersymmetry and the model of Universal Extra Dimensions and discuss various methods for their discrimination at hadron colliders. We study the discovery reach of the Tevatron and the LHC for level 2 Kaluza-Klein modes, which would indicate the presence of extra dimensions. We find that with 100 fb −1 of data the LHC will be able to discover the γ 2 and Z 2 KK modes as separate resonances if their masses are below 2 TeV. We also investigate the possibility to differentiate the spins of the superpartners and KK modes by means of the asymmetry method of Barr.

Physics Letters B 620 (2005) 42-51. doi:10.1016/j.physletb.2005.05.075Received by publisher: 2005-03-23Harvest Date: 2016-01-04 12:22:20DOI: 10.1016/j.physletb.2005.05.075Page Range: 42-5

We present an implementation of the model of minimal universal extra dimensions (MUED) in CalcHEP/CompHEP. We include all level-1 and level-2 Kaluza-Klein (KK) particles outside the Higgs sector. The mass spectrum is automatically calculated at one loop in terms of the two input parameters in MUED: the inverse radius R −1 of the extra dimension and the cut-off scale of the model Λ. We implement both the KK number conserving and the KK number violating interactions of the KK particles. We also account for the proper running of the gauge coupling constants above the electroweak scale. The implementation has been extensively cross-checked against known analytical results in the literature and numerical results from other programs. Our files are publicly available and can be used to perform various automated calculations within the MUED model.

Nuclear Physics, Section B 681 (2004) 31-64. doi:10.1016/j.nuclphysb.2003.12.012Received by publisher: 2003-04-23Harvest Date: 2016-01-04 12:22:37DOI: 10.1016/j.nuclphysb.2003.12.012Page Range: 31-6

No abstract

We analyze the cascade decays of the scalar quarks and gluinos of the minimal supersymmetric extension of the standard model, which are abundantly produced at the ͑CERN͒ Large Hadron Collider, into heavier charginos and neutralinos which then decay into the lighter ones and charged Higgs particles, and we show that they can have substantial branching fractions. The production rates of these Higgs bosons can be much larger than those from the direct production mechanisms, in particular for intermediate values of the parameter tan ␤, and could therefore allow for the detection of these particles. We also discuss charged Higgs boson production from direct two-body top and bottom squark decays as well as from two-and three-body gluino decays.

Thanks to the focus point phenomenon, it is quite natural for the minimal SUGRA model to have a large soft scalar mass (m 0 > 1 TeV). A distinctive feature of this model is an inverted hierarchy, where the lighter stop has a significantly smaller mass than the other squarks and sleptons. Consequently, the gluino is predicted to decay dominantly via stop exchange into a channel containing 2b and 2W along with the LSP. We exploit this feature to construct a robust signature for this model at the LHC in leptonic channels with 3-4 b tags and a large missing-E T . 1The minimal SUGRA model represents the most attractive model of low energy supersymmetry in terms of simplicity and economy of parameters [1]. Besides it can naturally account for the electroweak symmetry breaking as well as the suppression of flavour changing neutral current effects. The basic parameters of the model are m 0 , M 1/2 , A, B and µ -i.e. the soft supersymmetry breaking scalar and gaugino masses, the trilinear and bilinear couplings, along with the supersymmetric Higgs mass parameter. The last two can be determined in terms of the two Higgs vacuum expectation values, v 1 and v 2 , using the two minimisation conditions. The first one determines the B parameter in term ofand the ratio v 2 /v 1 ≡ tan β. The second condition giveswhere the last term comes from the radiative correction to the Higgs potential. Thus for any tan β, the naturalness of the electroweak scale requires m for tan β > ∼ 5. Moreover, contrary to some earlier apprehensions, a large value of m 0 seems to lead to a cosmologically interesting dark matter density [5]. Besides a large m 0 would also alleviate the potential conflict of the minimal SUGRA model with the electric dipole moments of electron and neutron [6]. Thus the minimal SUGRA model with a large soft scalar mass (m 0 > 1 TeV) seems to be attractive both on theoretical and phenomenological grounds. We shall analyse the signature of this model at the large hadron collider (LHC) by exploiting the distinctive characteristics of the large m 0 limit. Indeed we shall see that they lead to a more robust signal at LHC compared to the canonical SUGRA model. The ModelFor qualitative understanding of the model it is instructive to look at the approximate expressions for the electroweak scale scalar masses in terms of the universal soft mass parameters at the GUT scale. We shall neglect the GUT scale A parameter, which is unimportant for the present consideration; and assume not too large tan β where the b Yukawa coupling is relatively less significant. Then analytic solutions to the one-loop RGE givewhere U and Q refer to the 3rd generation singlet and doublet squarks [7]. Herewhere the subscript f denotes the fixed point values of the top Yukawa coupling and the corresponding tan β at the electroweak scale. The numerical coefficients of y in (3) which is in turn related to the physical top quark mass M t viaThe QCD and SUSY radiative corrections add about 6% and 4% respectively to the running mass to arrive at the phys...