1,688 research outputs found
Four Generations and Higgs Physics
In the light of the LHC, we revisit the implications of a fourth generation
of chiral matter. We identify a specific ensemble of particle masses and
mixings that are in agreement with all current experimental bounds as well as
minimize the contributions to electroweak precision observables. Higgs masses
between 115-315 (115-750) GeV are allowed by electroweak precision data at the
68% and 95% CL. Within this parameter space, there are dramatic effects on
Higgs phenomenology: production rates are enhanced, weak-boson-fusion channels
are suppressed, angular distributions are modified, and Higgs pairs can we
observed. We also identify exotic signals, such as Higgs decay to same-sign
dileptons. Finally, we estimate the upper bound on the cutoff scale from vacuum
stability and triviality.Comment: 11 pages, 7 figures, REVTe
Top Quark Seesaw, Vacuum Structure and Electroweak Precision Constraints
We present a complete study of the vacuum structure of Top Quark Seesaw
models of the Electroweak Symmetry Breaking, including bottom quark mass
generation. Such models emerge naturally from extra dimensions. We perform a
systematic gap equation analysis and develop an improved broken phase
formulation for including exact seesaw mixings. The composite Higgs boson
spectrum is studied in the large-N_c fermion-bubble approximation and an
improved renormalization group approach. The theoretically allowed parameter
space is restrictive, leading to well-defined predictions. We further analyze
the electroweak precision constraints. Generically, a heavy composite Higgs
boson with a mass of ~1TeV is predicted, yet fully compatible with the
precision data.Comment: 73 pages, 26 Figures, Latex2e (minor refinements, one Fig added
Charge-coupled devices detectors with high quantum efficiency at UV wavelengths
We report on multilayer high efficiency antireflection coating (ARC) design and development for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of single-layer coatings, which achieve >50% quantum efficiency (QE) in four bands from 130 to 300 nm. We now present multilayer coating designs that significantly outperform our previous work between 195 and 215 nm. Using up to 11 layers, we present several model designs to reach QE above 80%. We also demonstrate the successful performance of 5 and 11 layer ARCs on silicon and fused silica substrates. Finally, we present a five-layer coating deposited onto a thinned, delta-doped CCD and demonstrate external QE greater than 60% between 202 and 208 nm, with a peak of 67.6% at 206 nm
Maverick dark matter at colliders
Assuming that dark matter is a weakly interacting massive particle (WIMP)
species X produced in the early Universe as a cold thermal relic, we study the
collider signal of pp or ppbar -> XXbar + jets and its distinguishability from
standard-model background processes associated with jets and missing energy. We
assume that the WIMP is the sole particle related to dark matter within reach
of the LHC--a "maverick" particle--and that it couples to quarks through a
higher dimensional contact interaction. We simulate the WIMP final-state signal
XXbar + jet and dominant standard-model (SM) background processes and find that
the dark-matter production process results in higher energies for the colored
final state partons than do the standard-model background processes, resulting
in more QCD radiation and a higher jet multiplicity. As a consequence, the
detectable signature of maverick dark matter is an excess over standard-model
expectations of events consisting of large missing transverse energy, together
with large leading jet transverse momentum and scalar sum of the transverse
momenta of the jets. Existing Tevatron data and forthcoming LHC data can
constrain (or discover!) maverick dark matter.Comment: 11 pages, 7 figure
Emergency and critical care services in Tanzania: a survey of ten hospitals.
While there is a need for good quality care for patients with serious reversible disease in all countries in the world, Emergency and Critical Care tends to be one of the weakest parts of health systems in low-income countries. We assessed the structure and availability of resources for Emergency and Critical Care in Tanzania in order to identify the priorities for improving care in this neglected specialty. Ten hospitals in four regions of Tanzania were assessed using a structured data collection tool. Quality was evaluated with standards developed from the literature and expert opinion. Important deficits were identified in infrastructure, routines and training. Only 30% of the hospitals had an emergency room for adult and paediatric patients. None of the seven district and regional hospitals had a triage area or intensive care unit for adults. Only 40% of the hospitals had formal systems for adult triage and in less than one third were critically ill patients seen by clinicians more than once daily. In 80% of the hospitals there were no staff trained in adult triage or critical care. In contrast, a majority of equipment and drugs necessary for emergency and critical care were available in the hospitals (median 90% and 100% respectively. The referral/private hospitals tended to have a greater overall availability of resources (median 89.7%) than district/regional hospitals (median 70.6). Many of the structures necessary for Emergency and Critical Care are lacking in hospitals in Tanzania. Particular weaknesses are infrastructure, routines and training, whereas the availability of drugs and equipment is generally good. Policies to improve hospital systems for the care of emergency and critically ill patients should be prioritised
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the
design of new-physics searches at the LHC and the characterization of their
results. Both ATLAS and CMS have already presented some results in terms of
simplified models, and we encourage them to continue and expand this effort,
which supplements both signature-based results and benchmark model
interpretations. A simplified model is defined by an effective Lagrangian
describing the interactions of a small number of new particles. Simplified
models can equally well be described by a small number of masses and
cross-sections. These parameters are directly related to collider physics
observables, making simplified models a particularly effective framework for
evaluating searches and a useful starting point for characterizing positive
signals of new physics. This document serves as an official summary of the
results from the "Topologies for Early LHC Searches" workshop, held at SLAC in
September of 2010, the purpose of which was to develop a set of representative
models that can be used to cover all relevant phase space in experimental
searches. Particular emphasis is placed on searches relevant for the first
~50-500 pb-1 of data and those motivated by supersymmetric models. This note
largely summarizes material posted at http://lhcnewphysics.org/, which includes
simplified model definitions, Monte Carlo material, and supporting contacts
within the theory community. We also comment on future developments that may be
useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results
from "Topologies for Early LHC Searches" workshop (SLAC, September 2010).
Supplementary material can be found at http://lhcnewphysics.or
Development and evaluation of an online three-level proton vs photon decision support prototype for head and neck cancer - Comparison of dose, toxicity and cost-effectiveness
AbstractTo quantitatively assess the effectiveness of proton therapy for individual patients, we developed a prototype for an online platform for proton decision support (PRODECIS) comparing photon and proton treatments on dose metric, toxicity and cost-effectiveness levels. An evaluation was performed with 23 head and neck cancer datasets
Higgs Boson Decay into Hadronic Jets
The remarkable agreement of electroweak data with standard model (SM)
predictions motivates the study of extensions of the SM in which the Higgs
boson is light and couples in a standard way to the weak gauge bosons.
Postulated new light particles should have small couplings to the gauge bosons.
Within this context it is natural to assume that the branching fractions of the
light SM-like Higgs boson mimic those in the standard model. This assumption
may be unwarranted, however, if there are non-standard light particles coupled
weakly to the gauge bosons but strongly to the Higgs field. In particular, the
Higgs boson may effectively decay into hadronic jets, possibly without
important bottom or charm flavor content. As an example, we present a simple
extension of the SM, in which the predominant decay of the Higgs boson occurs
into a pair of light bottom squarks that, in turn, manifest themselves as
hadronic jets. Discovery of the Higgs boson remains possible at an
electron-positron linear collider, but prospects at hadron colliders are
diminished substantially.Comment: 30 pages, 7 figure
The MicroRNA-200 Family Is Upregulated in Endometrial Carcinoma
BACKGROUND: MicroRNAs (miRNAs, miRs) are small non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. MicroRNAs are dysregulated in cancer and may play essential roles in tumorigenesis. Additionally, miRNAs have been shown to have prognostic and diagnostic value in certain types of cancer. The objective of this study was to identify dysregulated miRNAs in endometrioid endometrial adenocarcinoma (EEC) and the precursor lesion, complex atypical hyperplasia (CAH). METHODOLOGY: We compared the expression profiles of 723 human miRNAs from 14 cases of EEC, 10 cases of CAH, and 10 normal proliferative endometria controls using Agilent Human miRNA arrays following RNA extraction from formalin-fixed paraffin-embedded (FFPE) tissues. The expression of 4 dysregulated miRNAs was validated using real time reverse transcription-PCR. RESULTS: Forty-three miRNAs were dysregulated in EEC and CAH compared to normal controls (p<0.05). The entire miR-200 family (miR-200a/b/c, miR-141, and miR-429) was up-regulated in cases of EEC. CONCLUSIONS: This information contributes to the candidate miRNA expression profile that has been generated for EEC and shows that certain miRNAs are dysregulated in the precursor lesion, CAH. These miRNAs in particular may play important roles in tumorigenesis. Examination of miRNAs that are consistently dysregulated in various studies of EEC, like the miR-200 family, will aid in the understanding of the role that miRNAs play in tumorigenesis in this tumour type
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