65 research outputs found
The B-L MSSM from Strings to the LHC
We develop connections between a string-motivated realization of the minimal
B â?? L extension of the MSSM and LHC-observable phenomenology. Using a
random scan of the high-scale parameter space, together with numerical solution
of the renormalization group equations, we connect the modelâ??s roots in String
Theory to its phenomenological implications for the LHC. One predictive result of
this approach is a limited set of possible lightest supersymmetric particles (LSPs).
Motivated by this result, we study the implications of a stop or sbottom LSP at
the LHC. This yields predictive connections between the neutrino sector and the
LHC. We present lower bounds on the mass of stop and sbottom LSPs
The -parity Violating Decays of Charginos and Neutralinos in the B-L MSSM
The MSSM is the MSSM with three right-handed neutrino chiral multiplets
and gauged symmetry. The symmetry is broken by the third family
right-handed sneutrino acquiring a VEV, thus spontaneously breaking -parity.
Within a natural range of soft supersymmetry breaking parameters, it is shown
that a large and uncorrelated number of initial values satisfy all present
phenomenological constraints; including the correct masses for the ,
bosons, having all sparticles exceeding their present lower bounds and
giving the experimentally measured value for the Higgs boson. For this "valid"
set of initial values, there are a number of different LSPs, each occurring a
calculable number of times. We plot this statistically and determine that among
the most prevalent LSPs are chargino and neutralino mass eigenstates. In this
paper, the -parity violating decay channels of charginos and neutralinos to
standard model particles are determined, and the interaction vertices and decay
rates computed analytically. These results are valid for any chargino and
neutralino, regardless of whether or not they are the LSP. For chargino and
neutralino LSPs, we will-- in a subsequent series of papers --present a
numerical study of their RPV decays evaluated statistically over the range of
associated valid initial points.Comment: 62 pages, 12 figures, added references in section 1, corrected some
calculation error
The Minimal SUSY Model: From the Unification Scale to the LHC
This paper introduces a random statistical scan over the high-energy initial
parameter space of the minimal SUSY model--denoted as the MSSM.
Each initial set of points is renormalization group evolved to the electroweak
scale--being subjected, sequentially, to the requirement of radiative and
electroweak symmetry breaking, the present experimental lower bounds on the
vector boson and sparticle masses, as well as the lightest neutral Higgs
mass of 125 GeV. The subspace of initial parameters that satisfies all
such constraints is presented, shown to be robust and to contain a wide range
of different configurations of soft supersymmetry breaking masses. The
low-energy predictions of each such "valid" point - such as the sparticle mass
spectrum and, in particular, the LSP - are computed and then statistically
analyzed over the full subspace of valid points. Finally, the amount of
fine-tuning required is quantified and compared to the MSSM computed using an
identical random scan. The MSSM is shown to generically require less
fine-tuning.Comment: 65 pages, 18 figure
Spontaneous R-Parity Breaking, Stop LSP Decays and the Neutrino Mass Hierarchy
The MSSM with right-handed neutrino supermultiplets, gauged B-L symmetry and
a non-vanishing sneutrino expectation value is the minimal theory that
spontaneously breaks R-parity and is consistent with the bounds on proton
stability and lepton number violation. This minimal B-L MSSM can have a
colored/charged LSP, of which a stop LSP is the most amenable to observation at
the LHC. We study the R-parity violating decays of a stop LSP into a bottom
quark and charged leptons--the dominant modes for a generic "admixture" stop. A
numerical analysis of the relative branching ratios of these decay channels is
given using a wide scan over the parameter space. The fact that R-parity is
violated in this theory by a vacuum expectation value of a sneutrino links
these branching ratios directly to the neutrino mass hierarchy. It is shown how
a discovery of bottom-charged lepton events at the LHC can potentially
determine whether the neutrino masses are in a normal or inverted hierarchy, as
well as determining the theta_23 neutrino mixing angle. Finally, present LHC
bounds on these leptoquark signatures are used to put lower bounds on the stop
mass.Comment: 13 pages, 2 figures, upgraded stop lower bound analysis, version
accepted by PL
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