86 research outputs found
General soft terms from Supergravity including D-terms
We derive general expressions for soft terms in supergravity where D-terms
contribute significantly to the supersymmetry breaking. Such D-terms can
produce large splitting between scalar and fermionic partners in the spectrum.
By requiring that supersymmetry breaking sets the cosmological constant to
zero, we then parameterize the soft terms when D-terms dominate over F-terms or
are comparable to them. We present an application of our results to the split
supersymmetry scenario and briefly address the issue of moduli stabilisation.Comment: 6 Pages, no figures. To appear in proceedings of the XXXXth
Rencontres de Moriond "Electroweak Interactions and Unified Theories", La
Thuile, Italy, March 5-12, 2005; V2 Typos in eq.(9) corrected and other
improvement
A little more Gauge Mediation and the light Higgs mass
We consider minimal models of gauge mediated supersymmetry breaking with an
extra factor in addition to the Standard Model gauge group. A
charged, Standard Model singlet is assumed to be present which allows for an
additional NMSSM like coupling, . The U(1) is assumed to be
flavour universal. Anomaly cancellation in the MSSM sector requires additional
coloured degrees of freedom. The field can get a large vacuum expectation
value along with consistent electroweak symmetry breaking. It is shown that the
lightest CP even Higgs boson can attain mass of the order of 125 GeV.Comment: 29 pages, 7 Figures; v2: updated references 30 pages, minor wordings
modified, to appear in Nucl. Phys.
Bulk Majorana mass terms and Dirac neutrinos in Randall Sundrum Model
We present a novel scheme where Dirac neutrinos are realized even if lepton
number violating Majorana mass terms are present. The setup is the
Randall-Sundrum framework with bulk right handed neutrinos. Bulk mass terms of
both Majorana and Dirac type are considered. It is shown that massless zero
mode solutions exist when the bulk Dirac mass term is set to zero. In this
limit, it is found that the effective 4D small neutrino mass is primarily of
Dirac nature with the Majorana type contributions being negligible.
Interestingly, this scenario is very similar to the one known with flat extra
dimensions. Neutrino phenomenology is discussed by fitting both charged lepton
masses and neutrino masses simultaneously. A single Higgs localised on the IR
brane is highly constrained as unnaturally large Yukawa couplings are required
to fit charged lepton masses. A simple extension with two Higgs doublets is
presented which facilitates a proper fit for the lepton masses.Comment: 13 Pages, Few clarifications included and added references. Figure
removed. Published in PR
Clockwork for Neutrino Masses and Lepton Flavor Violation
We investigate the generation of small neutrino masses in a clockwork
framework which includes Dirac mass terms as well as Majorana mass terms for
the new fermions. We derive analytic formulas for the masses of the new
particles and for their Yukawa couplings to the lepton doublets, in the
scenario where the clockwork parameters are universal. When the Majorana masses
all vanish, the zero mode of the clockwork sector forms a Dirac pair with the
active neutrino, with a mass which is in agreement with oscillations
experiments for a sufficiently large number of clockwork gears. On the other
hand, when the Majorana masses do not vanish, neutrino masses are generated via
the seesaw mechanism. In this case, and due to the fact that the effective
Yukawa couplings of the higher modes can be sizable, neutrino masses can only
be suppressed by postulating a large Majorana mass for all the gears. Finally,
we discuss the constraints on the mass scale of the clockwork fermions from the
non-observation of the rare leptonic decay .Comment: 11 pages, 7 figure
Flavored Co-annihilations
Neutralino dark matter in supersymmetric models is revisited in the presence
of flavor violation in the soft supersymmetry breaking sector. We focus on
flavor violation in the sleptonic sector and study the implications for the
co-annihilation regions. Flavor violation is introduced by a single
insertion in the slepton mass matrix. Limits on
this insertion from BR() are weak in some regions of the
parameter space where cancellations happen within the amplitudes. We look for
overlaps in parameter space where both the co-annihilation condition as well as
the cancellations within the amplitudes occur. In mSUGRA, such overlap regions
are not existent, whereas they are present in models with non-universal Higgs
boundary conditions (NUHM). The effect of flavor violation is two fold: (a) it
shifts the co-annihilation regions towards lighter neutralino masses (b) the
co-annihilation cross sections would be modified with the inclusion of flavor
violating diagrams which can contribute significantly. Even if flavor violation
is within the presently allowed limits, this is sufficient to modify the
thermally averaged cross-sections by about (10-15)% in mSUGRA and (20-30)% in
NUHM, depending on the parameter space. In the overlap regions, the flavor
violating cross sections become comparable and in some cases even dominant to
the flavor conserving ones. A comparative study of the channels is presented
for mSUGRA and NUHM cases.Comment: 38 pages, 28 figures. Significantly expanded and improved version
with a new section on channels and new appendices on mSUGRA and
cross-sections, version accepted for publication in JHE
Neutrino Mass Constraints on R violation and HERA anomaly
R parity violating trilinear couplings of the minimal
supersymmetric standard model (MSSM) are constrained from the limit on the
electron neutrino mass. Strong limits on these couplings follow from the
earlier neglected contribution due to sneutrino vacuum expectation values. The
limits on most of the couplings derived here are stronger than
the existing ones for a wide range in parameters of MSSM. These limits strongly
constrain the interpretation of recent HERA results in scattering in
terms of production of squarks through violating couplings. In particular,
the interpretation in terms of production off strange quark as
suggested recently is not viable for wide ranges in MSSM parameters.Comment: 15 pages with 5 figures, minor typos corrected and a new reference
adde
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