83 research outputs found
Soft SUSY Breaking Terms for Chiral Matter in IIB String Compactifications
This paper develops the computation of soft supersymmetry breaking terms for
chiral D7 matter fields in IIB Calabi-Yau flux compactifications with
stabilised moduli. We determine explicit expressions for soft terms for the
single-modulus KKLT scenario and the multiple-moduli large volume scenario. In
particular we use the chiral matter metrics for Calabi-Yau backgrounds recently
computed in hep-th/0609180. These differ from the better understood metrics for
non-chiral matter and therefore give a different structure of soft terms. The
soft terms take a simple form depending explicitly on the modular weights of
the corresponding matter fields. For the large-volume case we find that in the
simplest D7 brane configuration, scalar masses, gaugino masses and A-terms are
very similar to the dilaton-dominated scenario. Although all soft masses are
suppressed by ln(M_P/m_{3/2}) compared to the gravitino mass, the
anomaly-mediated contributions do not compete, being doubly suppressed and thus
subdominant to the gravity-mediated tree-level terms. Soft terms are
flavour-universal to leading order in an expansion in inverse Kahler moduli.
They also do not introduce extra CP violating phases to the effective action.
We argue that soft term flavour universality should be a property of the
large-volume compactifications, and more generally IIB flux models, in which
flavour is determined by the complex structure moduli while supersymmetry is
broken by the Kahler moduli. For the simplest large-volume case we run the soft
terms to low energies and present some sample spectra and a basic
phenomenological analysis.Comment: 40 pages, 9 figures, JHEP style; v2. sentence rephrase
Scanning the Landscape of Flux Compactifications: Vacuum Structure and Soft Supersymmetry Breaking
We scan the landscape of flux compactifications for the Calabi-Yau manifold
with two K\" ahler moduli by varying the value of
the flux superpotential over a large range of values. We do not include
uplift terms. We find a rich phase structure of AdS and dS vacua. Starting with
we reproduce the exponentially large volume scenario, but as
is reduced new classes of minima appear. One of them corresponds to the
supersymmetric KKLT vacuum while the other is a new, deeper non-supersymmetric
minimum. We study how the bare cosmological constant and the soft supersymmetry
breaking parameters for matter on D7 branes depend on , for these classes
of minima. We discuss potential applications of our results.Comment: draft format remove
Low-Energy Supersymmetry Breaking from String Flux Compactifications: Benchmark Scenarios
Soft supersymmetry breaking terms were recently derived for type IIB string
flux compactifications with all moduli stabilised. Depending on the choice of
the discrete input parameters of the compactification such as fluxes and ranks
of hidden gauge groups, the string scale was found to have any value between
the TeV and GUT scales. We study the phenomenological implications of these
compactifications at low energy. Three realistic scenarios can be identified
depending on whether the Standard Model lies on D3 or D7 branes and on the
value of the string scale. For the MSSM on D7 branes and the string scale
between 10^12 GeV and 10^17 GeV we find that the LSP is a neutralino, while for
lower scales it is the stop. At the GUT scale the results of the fluxed MSSM
are reproduced, but now with all moduli stabilised. For the MSSM on D3 branes
we identify two realistic scenarios. The first one corresponds to an
intermediate string scale version of split supersymmetry. The second is a
stringy mSUGRA scenario. This requires tuning of the flux parameters to obtain
the GUT scale. Phenomenological constraints from dark matter, (g-2)_mu and
BR(b->s gamma) are considered for the three scenarios. We provide benchmark
points with the MSSM spectrum, making the models suitable for a detailed
phenomenological analysis.Comment: 29 pages, 12 figures, reference adde
Type IIA Orientifolds on General Supersymmetric Z_N Orbifolds
We construct Type IIA orientifolds for general supersymmetric Z_N orbifolds.
In particular, we provide the methods to deal with the non-factorisable
six-dimensional tori for the cases Z7, Z8, Z8', Z12 and Z12'. As an application
of these methods we explicitly construct many new orientifold models.Comment: 48 pages, LaTeX, 14 figures, refs. added, closed string spectra
slightly change
Moduli Stabilisation and de Sitter String Vacua from Magnetised D7 Branes
Anomalous U(1)'s are ubiquitous in 4D chiral string models. Their presence
crucially affects the process of moduli stabilisation and cannot be neglected
in realistic set-ups. Their net effect in the 4D effective action is to induce
a matter field dependence in the non-perturbative superpotential and a
Fayet-Iliopoulos D-term. We study flux compactifications of IIB string theory
in the presence of magnetised D7 branes. These give rise to anomalous U(1)'s
that modify the standard moduli stabilisation procedure. We consider simple
orientifold models to determine the matter field spectrum and the form of the
effective field theory. We apply our results to one-modulus KKLT and
multi-moduli large volume scenarios, in particular to the Calabi-Yau
P^4_{[1,1,1,6,9]}. After stabilising the matter fields, the effective action
for the Kahler moduli can acquire an extra positive term that can be used for
de Sitter lifting with non-vanishing F- and D-terms. This provides an explicit
realization of the D-term lifting proposal of hep-th/0309187.Comment: 35 pages, 1 figure. v2: Minor changes, references adde
Sparticle Spectra and LHC Signatures for Large Volume String Compactifications
We study the supersymmetric particle spectra and LHC collider observables for
the large-volume string models with a fundamental scale of 10^{11} GeV that
arise in moduli-fixed string compactifications with branes and fluxes. The
presence of magnetic fluxes on the brane world volume, required for chirality,
perturb the soft terms away from those previously computed in the dilute-flux
limit. We use the difference in high-scale gauge couplings to estimate the
magnitude of this perturbation and study the potential effects of the magnetic
fluxes by generating many random spectra with the soft terms perturbed around
the dilute flux limit. Even with a 40% variation in the high-scale soft terms
the low-energy spectra take a clear and predictive form. The resulting spectra
are broadly similar to those arising on the SPS1a slope, but more degenerate.
In their minimal version the models predict the ratios of gaugino masses to be
M_1 : M_2 : M_3=(1.5 - 2) : 2 : 6, different to both mSUGRA and mirage
mediation. Among the scalars, the squarks tend to be lighter and the sleptons
heavier than for comparable mSUGRA models. We generate 10 fb^{-1} of sample LHC
data for the random spectra in order to study the range of collider
phenomenology that can occur. We perform a detailed mass reconstruction on one
example large-volume string model spectrum. 100 fb^{-1} of integrated
luminosity is sufficient to discriminate the model from mSUGRA and aspects of
the sparticle spectrum can be accurately reconstructed.Comment: 42 pages, 21 figures. Added references and discussion for section 3.
Slight changes in the tex
Large-Volume Flux Compactifications: Moduli Spectrum and D3/D7 Soft Supersymmetry Breaking
We present an explicit calculation of the spectrum of a general class of
string models, corresponding to Calabi-Yau flux compactifications with
h_{1,2}>h_{1,1}>1 with leading perturbative and non-perturbative corrections,
in which all geometric moduli are stabilised as in hep-th/0502058. The volume
is exponentially large, leading to a range of string scales from the Planck
mass to the TeV scale, realising for the first time the large extra dimensions
scenario in string theory. We provide a general analysis of the relevance of
perturbative and non-perturbative effects and the regime of validity of the
effective field theory. We compute the spectrum in the moduli sector finding a
hierarchy of masses depending on inverse powers of the volume. We also compute
soft supersymmetry breaking terms for particles living on D3 and D7 branes. We
find a hierarchy of soft terms corresponding to `volume dominated' F-term
supersymmetry breaking. F-terms for Kahler moduli dominate both those for
dilaton and complex structure moduli and D-terms or other de Sitter lifting
terms. This is the first class of string models in which soft supersymmetry
breaking terms are computed after fixing all geometric moduli. We outline
several possible applications of our results, both for cosmology and
phenomenology and point out the differences with the less generic KKLT vacua.Comment: 64 pages, 4 figures; v2. references added; v3. typos, reference
added, matches published versio
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