270 research outputs found
Exploring the Higgs Portal with 10/fb at the LHC
We consider the impact of new exotic colored and/or charged matter
interacting through the Higgs portal on Standard Model Higgs boson searches at
the LHC. Such Higgs portal couplings can induce shifts in the effective
Higgs-gluon-gluon and Higgs-photon-photon couplings, thus modifying the Higgs
production and decay patterns. We consider two possible interpretations of the
current LHC Higgs searches based on ~ 5/fb of data at each detector: 1) a Higgs
boson in the mass range (124-126) GeV and 2) a `hidden' heavy Higgs boson which
is underproduced due to the suppression of its gluon fusion production cross
section. We first perform a model independent analysis of the allowed sizes of
such shifts in light of the current LHC data. As a class of possible candidates
for new physics which gives rise to such shifts, we investigate the effects of
new scalar multiplets charged under the Standard Model gauge symmetries. We
determine the scalar parameter space that is allowed by current LHC Higgs
searches, and compare with complementary LHC searches that are sensitive to the
direct production of colored scalar states.Comment: 27 pages, 11 figures; v2: references added, correction to scalar form
factor, numerical results updated with Moriond 2012 data, conclusions
unchange
Excluding Electroweak Baryogenesis in the MSSM
In the context of the MSSM the Light Stop Scenario (LSS) is the only region
of parameter space that allows for successful Electroweak Baryogenesis (EWBG).
This possibility is very phenomenologically attractive, since it allows for the
direct production of light stops and could be tested at the LHC. The ATLAS and
CMS experiments have recently supplied tantalizing hints for a Higgs boson with
a mass of ~ 125 GeV. This Higgs mass severely restricts the parameter space of
the LSS, and we discuss the specific predictions made for EWBG in the MSSM.
Combining data from all the available ATLAS and CMS Higgs searches reveals a
tension with the predictions of EWBG even at this early stage. This allows us
to exclude EWBG in the MSSM at greater than (90) 95% confidence level in the
(non-)decoupling limit, by examining correlations between different Higgs decay
channels. We also examine the exclusion without the assumption of a ~ 125 GeV
Higgs. The Higgs searches are still highly constraining, excluding the entire
EWBG parameter space at greater than 90% CL except for a small window of m_h ~
117 - 119 GeV.Comment: 24 Pages, 4 Figures (v3: fixed typos, minor corrections, added
references
Risk, Unexpected Uncertainty, and Estimation Uncertainty: Bayesian Learning in Unstable Settings
Recently, evidence has emerged that humans approach learning using Bayesian updating rather than (model-free) reinforcement algorithms in a six-arm restless bandit problem. Here, we investigate what this implies for human appreciation of uncertainty. In our task, a Bayesian learner distinguishes three equally salient levels of uncertainty. First, the Bayesian perceives irreducible uncertainty or risk: even knowing the payoff probabilities of a given arm, the outcome remains uncertain. Second, there is (parameter) estimation uncertainty or ambiguity: payoff probabilities are unknown and need to be estimated. Third, the outcome probabilities of the arms change: the sudden jumps are referred to as unexpected uncertainty. We document how the three levels of uncertainty evolved during the course of our experiment and how it affected the learning rate. We then zoom in on estimation uncertainty, which has been suggested to be a driving force in exploration, in spite of evidence of widespread aversion to ambiguity. Our data corroborate the latter. We discuss neural evidence that foreshadowed the ability of humans to distinguish between the three levels of uncertainty. Finally, we investigate the boundaries of human capacity to implement Bayesian learning. We repeat the experiment with different instructions, reflecting varying levels of structural uncertainty. Under this fourth notion of uncertainty, choices were no better explained by Bayesian updating than by (model-free) reinforcement learning. Exit questionnaires revealed that participants remained unaware of the presence of unexpected uncertainty and failed to acquire the right model with which to implement Bayesian updating
Implications of a Modified Higgs to Diphoton Decay Width
Motivated by recent results from Higgs searches at the Large Hadron Collider,
we consider possibilities to enhance the diphoton decay width of the Higgs
boson over the Standard Model expectation, without modifying either its
production rate or the partial widths in the WW and ZZ channels. Studying
effects of new charged scalars, fermions and vector bosons, we find that
significant variations in the diphoton width may be possible if the new
particles have light masses of the order of a few hundred GeV and sizeable
couplings to the Higgs boson. Such couplings could arise naturally if there is
large mass mixing between two charged particles that is induced by the Higgs
vacuum expectation value. In addition, there is generically also a shift in the
Z + Gamma partial width, which in the case of new vector bosons tends to be of
similar magnitude as the shift in the diphoton partial width, but smaller in
other cases. Therefore simultaneous measurements in these two channels could
reveal properties of new charged particles at the electroweak scale.Comment: 29 pages, 8 figures; v2: updated references and minor improvements in
presentations; v3: sign of the scalar contribution to Z+Gamma amplitudes
fixed. Related figures update
Higgs decay to dark matter in low energy SUSY: is it detectable at the LHC ?
Due to the limited statistics so far accumulated in the Higgs boson search at
the LHC, the Higgs boson property has not yet been tightly constrained and it
is still allowed for the Higgs boson to decay invisibly to dark matter with a
sizable branching ratio. In this work, we examine the Higgs decay to neutralino
dark matter in low energy SUSY by considering three different models: the
minimal supersymmetric standard model (MSSM), the next-to-minimal
supersymmetric standard models (NMSSM) and the nearly minimal supersymmetric
standard model (nMSSM). Under current experimental constraints at 2-sigma level
(including the muon g-2 and the dark matter relic density), we scan over the
parameter space of each model. Then in the allowed parameter space we calculate
the branching ratio of the SM-like Higgs decay to neutralino dark matter and
examine its observability at the LHC by considering three production channels:
the weak boson fusion VV->h, the associated production with a Z-boson pp->hZ+X
or a pair of top quarks pp->htt_bar+X. We find that in the MSSM such a decay is
far below the detectable level; while in both the NMSSM and nMSSM the decay
branching ratio can be large enough to be observable at the LHC.Comment: Version in JHE
Middleborns disadvantaged? testing birth-order effects on fitness in pre-industrial finns
Parental investment is a limited resource for which offspring compete in order to increase their own survival and reproductive success. However, parents might be selected to influence the outcome of sibling competition through differential investment. While evidence for this is widespread in egg-laying species, whether or not this may also be the case in viviparous species is more difficult to determine. We use pre-industrial Finns as our model system and an equal investment model as our null hypothesis, which predicts that (all else being equal) middleborns should be disadvantaged through competition. We found no overall evidence to suggest that middleborns in a family are disadvantaged in terms of their survival, age at first reproduction or lifetime reproductive success. However, when considering birth-order only among same-sexed siblings, first-, middle-and lastborn sons significantly differed in the number of offspring they were able to rear to adulthood, although there was no similar effect among females. Middleborn sons appeared to produce significantly less offspring than first-or lastborn sons, but they did not significantly differ from lastborn sons in the number of offspring reared to adulthood. Our results thus show that taking sex differences into account is important when modelling birth-order effects. We found clear evidence of firstborn sons being advantaged over other sons in the family, and over firstborn daughters. Therefore, our results suggest that parents invest differentially in their offspring in order to both preferentially favour particular offspring or reduce offspring inequalities arising from sibling competition
Culture Adaptation Alters Transcriptional Hierarchies among Single Human Embryonic Stem Cells Reflecting Altered Patterns of Differentiation
We have used single cell transcriptome analysis to re-examine the substates of early passage, karyotypically Normal, and late passage, karyotypically Abnormal (‘Culture Adapted’) human embryonic stem cells characterized by differential expression of the cell surface marker antigen, SSEA3. The results confirmed that culture adaptation is associated with alterations to the dynamics of the SSEA3(+) and SSEA3(-) substates of these cells, with SSEA3(-) Adapted cells remaining within the stem cell compartment whereas the SSEA3(-) Normal cells appear to have differentiated. However, the single cell data reveal that these substates are characterized by further heterogeneity that changes on culture adaptation. Notably the Adapted population includes cells with a transcriptome substate suggestive of a shift to a more naïve-like phenotype in contrast to the cells of the Normal population. Further, a subset of the Normal SSEA3(+) cells expresses genes typical of endoderm differentiation, despite also expressing the undifferentiated stem cell genes, POU5F1 (OCT4) and NANOG, whereas such apparently lineage-primed cells are absent from the Adapted population. These results suggest that the selective growth advantage gained by genetically variant, culture adapted human embryonic stem cells may derive in part from a changed substate structure that influences their propensity for differentiation
Pragmatic trials of pain therapies
Pragmatic randomised clinical trials aim to directly inform clinical or health policy decision-making. Here, we systematically review methods and design of pragmatic trials of pain therapies to examine methods, identify common challenges, and areas for improvement. Seven databases were searched for pragmatic randomised controlled clinical trials which assessed pain treatment in a clinical population of adults reporting pain. All screening steps and data extractions were performed twice. Data were synthesised descriptively and correlation analyses between pre-specified trial features and PRECIS-2 (PRagmatic – Explanatory Continuum Indicator Summary 2) ratings and attrition were performed. Protocol registration: PROSPERO-ID CRD42020178954. Of 57 included trials, only 21% assessed pharmacological interventions, the remainder physical, surgical, psychological or self-management pain therapies. Three-quarters of the trials were comparative effectiveness designs, often conducted in multiple centres (median: 5; Q1/3: 1, 9.25) and with a median sample size of 234 patients at randomization (Q1/3: 135.5; 363.5). Although most trials recruited chronic pain patients, reporting of pain duration was poor and not well described. Reporting was comprehensive for most general items, while often deficient for specific pragmatic aspects. Average ratings for pragmatism were highest for treatment adherence flexibility and clinical relevance of outcome measures. They were lowest for patient recruitment methods and extent of follow-up measurements and appointments. Current practice in pragmatic trials of pain treatments can be improved in areas such as patient recruitment and reporting of methods, analysis and interpretation of data. These improvements will facilitate translatability to other real-world settings – the purpose of pragmatic trials
Suicide Prevention for Older Adults in Residential Communities: Implications for Policy and Practice
Examining an often under-appreciated area, Carol Podgorski and colleagues discuss the suicide risk and opportunities for suicide prevention in seniors' residential communities
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