45 research outputs found
Flavour changing neutral currents and CP violating processes in generalized supersymmetric theories
We consider supersymmetric extensions of the standard model with general
non-universal soft breaking terms. We analyse in a model-independent way the
constraints on these terms at the electroweak energy scale coming from gluino
mediated flavour (F) changing neutral current and CP-violating processes. We
have computed the complete and effective hamiltonian
for gluino mediated processes, including for the first time the effect of box
diagrams in the evaluation of . We present
numerical results for the constraints on these non-universal soft breaking
terms for different values of the parameters, extending the analysis also to
the leptonic sector. A comparison with previous results in the literature is
given.Comment: LaTeX, 17 pages, 3 uuencoded figure
Phenomenology on a Slice of Spacetime
We study the phenomenology resulting from backgrounds of the form , where denotes a generic manifold of
dimension , and is the slice of 5-dimensional anti-de
Sitter space which generates the hierarchy in the Randall-Sundrum (RS) model.
The additional dimensions may be required when the RS model is
embedded into a more fundamental theory. We analyze two classes of
dimensional manifolds: flat and curved geometries. In the first case,
the additional flat dimensions may accommodate localized fermions which in turn
could resolve issues, such as proton decay and flavor, that were not addressed
in the original RS proposal. In the latter case, the positive curvature of an
manifold with can geometrically provide the
5-dimensional warping of the RS model. We demonstrate the key features of these
two classes of models by presenting the background solutions, the spectra of
the Kaluza-Klein (KK) gravitons, and their 4-dimensional couplings, for the
sample manifolds , , and . The resulting phenomenology is
distinct from that of the original RS scenario due to the appearance of a
multitude of new KK graviton states at the weak scale with couplings that are
predicted to be measurably non-universal within the KK tower. In addition, in
the case of flat compactifications, fermion localization can result in KK
graviton and gauge field flavor changing interactions.Comment: 30 pages, 8 figures. Small corrections included to agree with
published versio
Supersymmetric Relations Among Electromagnetic Dipole Operators
Supersymmetric contributions to all leptonic electromagnetic dipole operators
have essentially identical diagramatic structure. With approximate slepton
universality this allows the muon anomalous magnetic moment to be related to
the electron electric dipole moment in terms of supersymmetric phases, and to
radiative flavor changing lepton decays in terms of small violations of slepton
universality. If the current discrepancy between the measured and Standard
Model values of the muon anomalous magnetic moment is due to supersymmetry, the
current bound on the electron electric dipole moment then implies that the
phase of the electric dipole operator is less than . Likewise
the current bound on decay implies that the fractional
selectron-smuon mixing in the left-left mass squared matrix, \delta m_{\smuon
\selectron}^2 / m_{\slepton}^2, is less than . These relations and
constraints are fairly insensitive to details of the superpartner spectrum for
moderate to large .Comment: Latex, 38 pages, 2 figure
Electric Dipole Moments Do Not Require the CP-violating Phases of Supersymmetry To Be Small
We report the first fully general numerical calculation of the neutron and
electron dipole moments, including the seven significant phases. We find that
there are major regions in the parameter space where none of the phases are
required to be small, contrary to the conventional wisdom. The electric dipole
moments (EDM's) do provide useful constraints, allowing other regions of
parameter space to be carved away. We keep all superpartner masses light so
agreement with experimental limits arises purely from interesting relations
among soft breaking parameters.Comment: 23 pages, 7 figures; 2 references adde
Collider aspects of flavour physics at high Q
This review presents flavour related issues in the production and decays of
heavy states at LHC, both from the experimental side and from the theoretical
side. We review top quark physics and discuss flavour aspects of several
extensions of the Standard Model, such as supersymmetry, little Higgs model or
models with extra dimensions. This includes discovery aspects as well as
measurement of several properties of these heavy states. We also present public
available computational tools related to this topic.Comment: Report of Working Group 1 of the CERN Workshop ``Flavour in the era
of the LHC'', Geneva, Switzerland, November 2005 -- March 200
Genome-wide association study identifies four novel loci associated with Alzheimer's endophenotypes and disease modifiers
More than 20 genetic loci have been associated with risk for Alzheimer's disease (AD), but reported genome-wide significant loci do not account for all the estimated heritability and provide little information about underlying biological mechanisms. Genetic studies using intermediate quantitative traits such as biomarkers, or endophenotypes, benefit from increased statistical power to identify variants that may not pass the stringent multiple test correction in case-control studies. Endophenotypes also contain additional information helpful for identifying variants and genes associated with other aspects of disease, such as rate of progression or onset, and provide context to interpret the results from genome-wide association studies (GWAS). We conducted GWAS of amyloid beta (Aβ42), tau, and phosphorylated tau (ptau181) levels in cerebrospinal fluid (CSF) from 3146 participants across nine studies to identify novel variants associated with AD. Five genome-wide significant loci (two novel) were associated with ptau181, including loci that have also been associated with AD risk or brain-related phenotypes. Two novel loci associated with Aβ42 near GLIS1 on 1p32.3 (β = -0.059, P = 2.08 × 10-8) and within SERPINB1 on 6p25 (β = -0.025, P = 1.72 × 10-8) were also associated with AD risk (GLIS1: OR = 1.105, P = 3.43 × 10-2), disease progression (GLIS1: β = 0.277, P = 1.92 × 10-2), and age at onset (SERPINB1: β = 0.043, P = 4.62 × 10-3). Bioinformatics indicate that the intronic SERPINB1 variant (rs316341) affects expression of SERPINB1 in various tissues, including the hippocampus, suggesting that SERPINB1 influences AD through an Aβ-associated mechanism. Analyses of known AD risk loci suggest CLU and FERMT2 may influence CSF Aβ42 (P = 0.001 and P = 0.009, respectively) and the INPP5D locus may affect ptau181 levels (P = 0.009); larger studies are necessary to verify these results. Together the findings from this study can be used to inform future AD studies
A common haplotype lowers PU.1 expression in myeloid cells and delays onset of Alzheimer's disease
A genome-wide survival analysis of 14,406 Alzheimer's disease (AD) cases and 25,849 controls identified eight previously reported AD risk loci and 14 novel loci associated with age at onset. Linkage disequilibrium score regression of 220 cell types implicated the regulation of myeloid gene expression in AD risk. The minor allele of rs1057233 (G), within the previously reported CELF1 AD risk locus, showed association with delayed AD onset and lower expression of SPI1 in monocytes and macrophages. SPI1 encodes PU.1, a transcription factor critical for myeloid cell development and function. AD heritability was enriched within the PU.1 cistrome, implicating a myeloid PU.1 target gene network in AD. Finally, experimentally altered PU.1 levels affected the expression of mouse orthologs of many AD risk genes and the phagocytic activity of mouse microglial cells. Our results suggest that lower SPI1 expression reduces AD risk by regulating myeloid gene expression and cell function