191 research outputs found
Probing the Randall-Sundrum geometric origin of flavor with lepton flavor violation
The ``anarchic'' Randall-Sundrum model of flavor is a low energy solution to
both the electroweak hierarchy and flavor problems. Such models have a warped,
compact extra dimension with the standard model fermions and gauge bosons
living in the bulk, and the Higgs living on or near the TeV brane. In this
paper we consider bounds on these models set by lepton flavor violation
constraints. We find that loop-induced decays of the form l->l'+gamma are
ultraviolet sensitive and uncalculable when the Higgs field is localized on a
four-dimensional brane; this drawback does not occur when the Higgs field
propagates in the full five-dimensional space-time. We find constraints at the
few TeV level throughout the natural range of parameters, arising from
muon-electron conversion in the presence of nuclei, rare muon decays, and rare
tau decays. A "tension" exists between loop-induced dipole decays such as
mu->e+gamma and tree-level processes such as muon-electron conversion; they
have opposite dependences on the five-dimensional Yukawa couplings, making it
difficult to decouple flavor-violating effects. We emphasize the importance of
the future experiments MEG and PRIME. These experiments will definitively test
the Randall-Sundrum geometric origin of hierarchies in the lepton sector at the
TeV-scale.Comment: 27 pgs, 15 figs; v2: numerical bug in tau decays fixe
Conflict Resolution and Distributive Justice: Reflections on the Burton-Laue Debate
Excerpt
From its inception, the field of conflict resolution has appealed strongly to practitioners, researchers, and theorists interested in social betterment. Most conflict resolvers would probably agree that their efforts are motivated, at least in part, by the conception of a Good (or at least a Better) Society considerably less violent and contentious, more peaceful and cooperative, than the existing social order. Many would also affirm that in order to reach this goal, the sources of violence and contention, which include cultural norms sanctioning or glorifying violence, invidious and discriminatory isms (racism, sexism, etc.), gross socioeconomic and political inequities, and over-reliance on formal, adversarial decision-making procedures need to be eliminated or, at least, mitigated. And many would assert, in addition, that the methods of making these changes should be consistent, so far as possible, with the aims sought to be achieved: that is, they should rely on nonviolent conflict resolution.
R-symmetric Gauge Mediation and the MRSSM
This is an invited summary of a seminar talk given at various institutions in
the United States and Canada. After a brief introduction, a review of the
minimal R-symmetric supersymmetric standard model is given, and the benefits to
the flavor sector are discussed. R-symmetric gauge mediation is an attempt to
realize this model using metastable supersymmetry breaking techniques. Sample
low energy spectra are presented and tuning is discussed. Various other
phenomenological results are summarized.Comment: 14 pages, invited Brief Review, submitted to Modern Physics Letters
A; v2: replaced Figure 1, updated acknowledgments, fixed typo
QCD Corrections to K-Kbar Mixing in R-symmetric Supersymmetric Models
The leading-log QCD corrections to K-Kbar mixing in R-symmetric
supersymmetric models are computed using effective field theory techniques. The
spectrum topology where the gluino is significantly heavier than the squarks is
motivated and focused on. It is found that, like in the MSSM, QCD corrections
can tighten the kaon mass difference bound by roughly a factor of three. CP
violation is also briefly considered, where QCD corrections can constrain
phases to be as much as a factor of ten smaller than the uncorrected value.Comment: 11 pages, 11 pdf-figures; updated acknowledgments and references,
clarified relationship to Ref[17], clarified CP-violation sectio
Single top production in a non-minimal supersymmetric model
We study single top production at the LHC in a SUSY-QCD model with a heavy
Dirac gluino. The presence of a heavy Dirac gluino allows for notable top-up
flavour changing neutral currents. In this scenario, we find that the process
ug->tg gives the largest contribution to single top production via FCNCs at the
LHC. The key features of this signal are that the top quark is produced very
forward and that it is asymmetric to its anti-top counterpart, as the latter
lacks a valence quark.Comment: 9 pages, 4 figures, a background added, references added, minor
revisions, to be published in Phys. Lett.
R-symmetric gauge mediation
We present a version of Gauge Mediated Supersymmetry Breaking which preserves
an R-symmetry - the gauginos are Dirac particles, the A-terms are zero, and
there are four Higgs doublets. This offers an alternative way for gauginos to
acquire mass in the supersymmetry-breaking models of Intriligator, Seiberg, and
Shih. We investigate the possibility of using R-symmetric gauge mediation to
realize the spectrum and large sfermion mixing of the model of Kribs, Poppitz,
and Weiner.Comment: 26+ pages, 3 figures, BIBTEX; v2 published version: references added,
paragraph on spectrum running removed, section added on adjoint scalar
masses, clarification of the meaning of Table 3 adde
The flavor puzzle in multi-Higgs models
We reconsider the flavor problem in the models with two Higgs doublets. By
studying two generation toy models, we look for flavor basis independent
constraints on Yukawa couplings that will give us the mass hierarchy while
keeping all Yukawa couplings of the same order. We then generalize our findings
to the full three generation Standard Model. We find that we need two
constraints on the Yukawa couplings to generate the observed mass hierarchy,
and a slight tuning of Yukawa couplings of order 10%, much less than the
Standard Model. We briefly study how these constraints can be realized, and
show how flavor changing currents are under control for mixing in
the near-decoupling limit.Comment: 26 pages, typos are corrected, references are added, the final
versio
Nuclear Punctate Distribution of ALL-1 is Conferred by Distinct Elements at the N-terminus of the Protein
The ALL-1 gene positioned at 11q23 is directly involved in human acute leukemia either through a variety of chromosome translocations or by partial tandem duplications. ALL-1 is the human homologue of Drosophila trithorax which plays a critical role in maintaining proper spatial and temporal expression of the Antennapedia-bithorax homeotic genes determining the fruit fly's body pattern. Utilizing specific antibodies, we found that the ALL-1 protein distributes in cultured cells in a nuclear punctate pattern. Several chimeric ALL-1 proteins encoded by products of the chromosome translocations and expressed in transfected cells showed similar speckles. Dissection of the ALL-1 protein identified within its -1,100 N-terminal residues three polypeptides directing nuclear localization and at least two main domains conferring distribution in dots. The latter spanned two short sequences conserved with TRITHORAX. Enforced nuclear expression of other domains of ALL-1, such as the PHD (zinc) fingers and the SET motif, resulted in uniform nonpunctate patterns. This indicates that positioning of the ALL-1 protein in subnuclear structures is mediated via interactions of ALL-1 N-terminal elements. We suggest that the speckles represent protein complexes which contain multiple copies of the ALL-1 protein and are positioned at ALL-1 target sites on the chromatin. Therefore, the role of the N-terminal portion of ALL-1 is to direct the protein to its target genes
Threshold effects in excited charmed baryon decays
Motivated by recent results on charmed baryons from CLEO and FOCUS, we
reexamine the couplings of the orbitally excited charmed baryons. Due to its
proximity to the [Sigma_c pi] threshold, the strong decays of the
Lambda_c(2593) are sensitive to finite width effects. This distorts the shape
of the invariant mass spectrum in Lambda_{c1}-> Lambda_c pi^+pi^- from a simple
Breit-Wigner resonance, which has implications for the experimental extraction
of the Lambda_c(2593) mass and couplings. We perform a fit to unpublished CLEO
data which gives M(Lambda_c(2593)) - M(Lambda_c) = 305.6 +- 0.3 MeV and h2^2 =
0.24^{+0.23}_{-0.11}, with h2 the Lambda_{c1}-> Sigma_c pi strong coupling in
the chiral Lagrangian. We also comment on the new orbitally excited states
recently observed by CLEO.Comment: 9 pages, 3 figure
DN interaction from meson exchange
A model of the DN interaction is presented which is developed in close
analogy to the meson-exchange KbarN potential of the Juelich group utilizing
SU(4) symmetry constraints. The main ingredients of the interaction are
provided by vector meson (rho, omega) exchange and higher-order box diagrams
involving D*N, D\Delta, and D*\Delta intermediate states. The coupling of DN to
the pi-Lambda_c and pi-Sigma_c channels is taken into account. The interaction
model generates the Lambda_c(2595) resonance dynamically as a DN quasi-bound
state. Results for DN total and differential cross sections are presented and
compared with predictions of an interaction model that is based on the
leading-order Weinberg-Tomozawa term. Some features of the Lambda_c(2595)
resonance are discussed and the role of the near-by pi-Sigma_c threshold is
emphasized. Selected predictions of the orginal KbarN model are reported too.
Specifically, it is pointed out that the model generates two poles in the
partial wave corresponding to the Lambda(1405) resonance.Comment: 14 pages, 8 figure
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