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Register a new userSquark and Gaugino Hadroproduction and Decays in Non-Minimal Flavour Violating Supersymmetry
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We present an extensive analysis of squark and gaugino hadroproduction and decays in non-minimal flavour violating supersymmetry. We employ the so-called super-CKM basis to define the possible misalignment of quark and squark rotations, and we use generalized (possibly complex) charges to define the mutual couplings of (s)quarks and gauge bosons/gauginos. The cross sections for all squark-(anti-)squark/gaugino pair and squark-gaugino associated production processes as well as their decay widths are then given in compact analytic form. For four different constrained supersymmetry breaking models with non-minimal flavour violation in the second/third generation squark sector only, we establish the parameter space regions allowed/favoured by low-energy, electroweak precision, and cosmological constraints and display the chirality and flavour decomposition of all up- and down-type squark mass eigenstates. Finally, we compute numerically the dependence of a representative sample of production cross sections at the LHC on the off-diagonal mass matrix elements in the experimentally allowed/favoured ranges.
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We study the effects of squark generation mixing on squark and gluino production and decays at LHC in the Minimal Supersymmetric Standard Model (MSSM) with focus on the mixing between second and third generation squarks. Taking into account the constraints from B-physics experiments we show that various regions in parameter space exist where decays of squarks and/or gluinos into quark flavour violating (QFV) final states can have large branching ratios. Here we consider both fermionic and bosonic decays of squarks. Rates of the corresponding QFV signals, e.g. pp -> t t bar{c} bar{c} missing-E_T X, can be significant at LHC(14 TeV). We find that the inclusion of flavour mixing effects can be important for the search of squarks and gluinos and the determination of the underlying model parameters of the MSSM at LHC.
We study the effect of squark generation mixing on squark production and decays at the LHC in the Minimal Supersymmetric Standard Model (MSSM). We show that the effect can be very large despite the very strong constraints on quark flavour violation (QFV) from experimental data on B mesons. We find that the two lightest up-type squarks ${tilde u}_{1,2}$ can have large branching ratios for the decays into $c {tildechi_1^0}$ and $t {tildechi_1^0}$ at the same time, leading to QFV signals $p p to c bar t, (t bar c)$ + missing-$E_T$ + $X$ with a significant rate. The observation of this remarkable signature would provide a powerful test of supersymmetric QFV at LHC. This could have a significant impact on the search for squarks and the determination of the underlying MSSM parameters.
Quark flavour conserving (QFC) fermionic squark decays, such as ~t_{1,2} -> t neutralino_i, are usually assumed in squark search analyses. Here we study quark flavour violating (QFV) bosonic squark decays, such as ~u_2 -> ~u_1 h^0/Z^0, where the mass eigenstates ~u_{1,2} are mixtures of scharm and stop quarks. We show that the branching ratios of such QFV decays can be very large due to sizable ~c_R - ~t_{R/L} and ~t_R - ~t_L mixing effects despite the very strong constraints on the QFV parameters from B meson data. This can result in remarkable QFV signatures with significant rates at LHC (14 TeV), such as pp -> gluino gluino X -> t c bar{c} bar{c} h^0/Z^0 missing-E_T X and pp -> gluino gluino X -> t t bar{c} bar{c} h^0/Z^0 missing-E_T X. The QFV bosonic squark decays can play an important role in the squark and gluino searches at LHC (14 TeV).
We demonstrate that natural supersymmetry is readily realized in the framework of SU(4)_c times SU(2)_L times SU(2)_R with non-universal gaugino masses. Focusing on ameliorating the little hierarchy problem, we explore the parameter space of this model which yields small fine-tuning measuring parameters (natural supersymmetry) at the electroweak scale (Delta_{EW}) as well as at high scale (Delta_{HS}). It is possible to have both Delta_{EW} and Delta_{HS} less than 100 in these models, (2 % or better fine-tuning), while keeping the light CP-even (Standard Model-like) Higgs mass in the 123 GeV-127 GeV range. The light stop quark mass lies in the range 700 GeV <m_{tilde{t}_{1}}< 1500 GeV, and the range for the light stau lepton mass is 900 GeV <m_{tilde{tau}_{1}}< 1300 GeV. The first two family squarks are in the mass range 3000 GeV <m_{tilde{t}_{1}}< 4500 GeV, and for the gluino we find 2500 GeV <m_{tilde{g}_{1}}< 3500 GeV. We do not find any solution with natural supersymmetry which yields significant enhancement for Higgs production and decay in the diphoton channel.
The requirement of Yukawa coupling unification highly constrains the SUSY parameter space. In several SUSY breaking scenarios it is hard to reconcile Yukawa coupling unification with experimental constraints from B(b->s gamma) and the muon anomalous magnetic moment a_mu. We show that b-tau or even t-b-tau Yukawa unification can be satisfied simultaneously with b->s gamma and a_mu in the non-universal gaugino mediation scenario. Non-universal gaugino masses naturally appear in higher dimensional grand unified models in which gauge symmetry is broken by orbifold compactification. Relations between SUSY contributions to fermion masses, b->s gamma and a_mu which are typical for models with universal gaugino masses are relaxed. Consequently, these phenomenological constraints can be satisfied simultaneously with a relatively light SUSY spectrum, compared to models with universal gaugino masses.
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