94 research outputs found
Impact of LSP Character on Slepton Reach at the LHC
Searches for supersymmetry at the Large Hadron Collider (LHC) have
significantly constrained the parameter space associated with colored
superpartners, whereas the constraints on color-singlet superpartners are
considerably less severe. In this study, we investigate the dependence of
slepton decay branching fractions on the nature of the lightest supersymmetric
particle (LSP). In particular, in the Higgsino-like LSP scenarios, both decay
branching fractions of and depend strongly on
the sign and value of , which has strong implications for the reach of
dilepton plus MET searches for slepton pair production. We extend the
experimental results for same flavor, opposite sign dilepton plus MET searches
at the 8 TeV LHC to various LSP scenarios. We find that the LHC bounds on
sleptons are strongly enhanced for a non-Bino-like LSP: the 95% C.L. limit for
extends from 300 GeV for a Bino-like LSP to about 370 GeV
for a Wino-like LSP. The bound for with a Higgsino-like LSP is
the strongest (~ 490 GeV) for ~ and is the weakest
(~ 220 GeV) for ~ . We also calculate prospective
slepton search reaches at the 14 TeV LHC. With 100 fb integrated
luminosity, the projected 95% C.L. mass reach for the left-handed slepton
varies from 550 (670) GeV for a Bino-like (Wino-like) LSP to 900 (390) GeV for
a Higgsino-like LSP under the most optimistic (pessimistic) scenario. The reach
for the right-handed slepton is about 440 GeV. The corresponding 5
discovery sensitivity is about 100 GeV smaller. For 300 fb integrated
luminosity, the reach is about 50 - 100 GeV higher.Comment: 24 pages, 10 figure
Complex decay chains of top and bottom squarks
Current searches for the top squark mostly focus on the decay channels of
or , leading to final states
for top squark pair production at the LHC. In supersymmetric scenarios with
light gauginos other than the neutralino lightest supersymmetric particle
(LSP), different decay modes of the top squark could be dominant, which
significantly weaken the current top squark search limits at the LHC.
Additionally, new decay modes offer alternative discovery channels for top
squark searches. In this paper, we study the top squark and bottom squark decay
in the Bino-like LSP case with light Wino or Higgsino next-to-LSPs (NLSPs), and
identify cases in which additional decay modes become dominant. We also perform
a collider analysis for top squark pair production with mixed top squark decay
final states of , , leading to the
collider signature. The branching fraction for
such decay varies between 25\% and 50\% for a top squark mass larger than 500
GeV with GeV. At the 14 TeV LHC with 300
integrated luminosity, the top squark can be excluded up to about 1040 GeV at
the 95\% C.L., or be discovered up to 940 GeV at 5 significance.Comment: 28 pages, 13 figure
Galaxy Bias and its Effects on the Baryon Acoustic Oscillations Measurements
The baryon acoustic oscillation (BAO) feature in the clustering of matter in
the universe serves as a robust standard ruler and hence can be used to map the
expansion history of the universe. We use high force resolution simulations to
analyze the effects of galaxy bias on the measurements of the BAO signal. We
apply a variety of Halo Occupation Distributions (HODs) and produce biased mass
tracers to mimic different galaxy populations. We investigate whether galaxy
bias changes the non-linear shifts on the acoustic scale relative to the
underlying dark matter distribution presented by Seo et al (2009). For the less
biased HOD models (b < 3), we do not detect any shift in the acoustic scale
relative to the no-bias case, typically 0.10% \pm 0.10%. However, the most
biased HOD models (b > 3) show a shift at moderate significance (0.79% \pm
0.31% for the most extreme case). We test the one-step reconstruction technique
introduced by Eisenstein et al. (2007) in the case of realistic galaxy bias and
shot noise. The reconstruction scheme increases the correlation between the
initial and final (z = 1) density fields achieving an equivalent level of
correlation at nearly twice the wavenumber after reconstruction. Reconstruction
reduces the shifts and errors on the shifts. We find that after reconstruction
the shifts from the galaxy cases and the dark matter case are consistent with
each other and with no shift. The 1-sigma systematic errors on the distance
measurements inferred from our BAO measurements with various HODs after
reconstruction are about 0.07% - 0.15%.Comment: Accepted by ApJ. 21 pages, 10 figure
High-precision predictions for the acoustic scale in the non-linear regime
We measure shifts of the acoustic scale due to nonlinear growth and redshift
distortions to a high precision using a very large volume of
high-force-resolution simulations. We compare results from various sets of
simulations that differ in their force, volume, and mass resolution. We find a
consistency within 1.5-sigma for shift values from different simulations and
derive shift alpha(z) -1 = (0.300\pm 0.015)% [D(z)/D(0)]^{2} using our fiducial
set. We find a strong correlation with a non-unity slope between shifts in real
space and in redshift space and a weak correlation between the initial redshift
and low redshift. Density-field reconstruction not only removes the mean shifts
and reduces errors on the mean, but also tightens the correlations: after
reconstruction, we recover a slope of near unity for the correlation between
the real and redshift space and restore a strong correlation between the low
and the initial redshifts. We derive propagators and mode-coupling terms from
our N-body simulations and compared with Zeldovich approximation and the shifts
measured from the chi^2 fitting, respectively. We interpret the propagator and
the mode-coupling term of a nonlinear density field in the context of an
average and a dispersion of its complex Fourier coefficients relative to those
of the linear density field; from these two terms, we derive a signal-to-noise
ratio of the acoustic peak measurement. We attempt to improve our
reconstruction method by implementing 2LPT and iterative operations: we obtain
little improvement. The Fisher matrix estimates of uncertainty in the acoustic
scale is tested using 5000 (Gpc/h)^3 of cosmological PM simulations from
Takahashi et al. (2009). (abridged)Comment: Revised to match the version in print: a new figure (figure 6) is
added and Section 5 (and figure 8) is revised to include more details. 19
emulated apj pages with 13 figures and 3 table
Medical Student Engagement in a Virtual Learning Environment Positively Correlates with Course Performance and Satisfaction in Psychiatry
This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Introduction
There has been a move to a “flipped classroom” (FC) in medical education. The FC promotes active learning and utilizes independent preparation prior to in-class sessions. Few studies have evaluated the effectiveness of the FC approach in medical education, specifically via virtual learning. The purpose of this study evaluates student and faculty perceptions of the FC approach and relationships between student engagement and performance.
Method
The first-year medical student psychiatry curriculum was redesigned with an FC approach and subsequently altered by COVID-19 to a virtual learning environment. A mixed-method approach was used to examine both qualitative assessment and quantitative performance data. Students and facilitators were invited to participate in surveys regarding the curriculum changes. Student performance data was collected via quizzes and examinations. Engagement was evaluated by student participation in National Board of Medical Examiners–style multiple-choice questions delivered via Top Hat®. Correlational analyses were used to evaluate associations between engagement and performance. T-tests were used to compare student satisfaction across 2019 and 2020.
Results
Performance on in-class questions was positively associated with class rank and performance (p < 0.005). More students were either satisfied or strongly satisfied (91.5%) in 2020 compared to 85.7% in 2019 (two-tailed t-test, p = 0.04). Most students (81.3%) preferred in-class questions to lectures. In 2020, 62.6% of student comments were positive regarding the psychiatry curriculum vs 33.3% in 2019. Over 61.5% of facilitators felt positive towards the changes.
Conclusion
Our results demonstrate a positive relationship between engagement and class performance. Students and facilitators positively perceived the approach, with students preferring in-class questions compared to lectures. Future research should evaluate overall performance on standardized tests, third-year clerkships, and number of students matching into psychiatry
Slepton Discovery in Electroweak Cascade Decay
The LHC studies on the MSSM slepton sector have mostly been focused on direct
slepton Drell-Yan pair production. In this paper, we analyze the case when the
sleptons are lighter than heavy neutralinos and can appear in the on-shell
decay of neutralino states. In particular, we have studied the \chi_1^\pm
\chi_2^0 associated production, with the consequent decays of \chi_1^\pm and
\chi_2^0 via on-shell sleptons. The invariant mass of the lepton pairs,
m_{\ell\ell}, from the neutralino decay has a distinctive triangle shape with a
sharp kinematic cutoff. We discuss the utilization of this triangle shape in
m_{\ell\ell} distribution to identify the slepton signal. We studied the
trilepton plus missing E_T signal and obtained the effective cross section,
\sigma \times BR \times acceptance, that is needed for a 5\sigma discovery as a
function of the cutoff mass for the LHC with center of mass energy 14 TeV and
100 fb^{-1} integrated luminosity. Our results are model independent such that
they could be applied to other models with similar decay topology. When applied
to the MSSM under simple assumptions, it is found that with 100 fb^{-1}
integrated luminosity, a discovery reach in the left-handed slepton mass of
about 600 GeV could be reached, which extends far beyond the slepton mass reach
in the usual Drell-Yan studies.Comment: 20 pages, 5 figure
First-Borns Carry a Higher Metabolic Risk in Early Adulthood: Evidence from a Prospective Cohort Study
Birth order has been associated with early growth variability and subsequent increased adiposity, but the consequent effects of increased fat mass on metabolic risk during adulthood have not been assessed. We aimed to quantify the metabolic risk in young adulthood of being first-born relative to those born second or subsequently.Body composition and metabolic risk were assessed in 2,249 men, aged 17-19 years, from a birth cohort in southern Brazil. Metabolic risk was assessed using a composite z-score integrating standardized measurements of blood pressure, total cholesterol, high density lipoprotein, triglycerides and fat mass. First-borns had lower birth weight z-score (Δ = -0.25, 95%CI -0.35, -0.15,p<0.001) but showed greater weight gain during infancy (change in weight z-score from birth to 20 months: Δ = 0.39, 95%CI 0.28-0.50, p<0.0001) and had greater mean height (Δ = 1.2 cm, 95%CI: 0.7-1.6, p<0.0001) and weight (Δ = 0.34 kg, 95%CI: 0.13-0.55, p<0.002) at 43 months. This greater weight and height tracked into early adulthood, with first-borns being significantly taller, heavier and with significantly higher fat mass than later-borns. The metabolic risk z-score was significantly higher in first-borns.First-born status is associated with significantly elevated adiposity and metabolic risk in young adult men in Brazil. Our results, linking cardiovascular risk with life history variables, suggest that metabolic risk may be associated with the worldwide trend to smaller family size and it may interact with changes in behavioural or environmental risk factors
Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences and Countermeasures.
Circadian (∼ 24 hour) timing systems pervade all kingdoms of life, and temporally optimize behaviour and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behaviour and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these too are increasingly subject to disruption. A large proportion of the world's population is at increased risk of environmentally-driven circadian rhythm and sleep disruption, and a minority of individuals are also genetically predisposed to circadian misalignment and sleep disorders. The consequences of disruption to the circadian system and sleep are profound and include myriad metabolic ramifications, some of which may be compounded by adverse effects on dietary choices. If not addressed, the deleterious effects of such disruption will continue to cause widespread health problems; therefore, implementation of the numerous behavioural and pharmaceutical interventions that can help restore circadian system alignment and enhance sleep will be important
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