258 research outputs found
Charged current universality problem and NuTeV anomaly: is SUSY to blame?
We compute the complete one-loop contributions to low-energy charged current weak interaction observables in the Minimal Supersymmetric Standard Model (MSSM). We obtain the constraints on the MSSM parameter space which arise when precision low-energy charged current (CC) data are analyzed in tandem with measurements of the muon anomaly. The data imply a pattern of mass splittings among first and second generation sleptons and squarks which contradicts predictions of widely used models for supersymmetry breaking mediation. We also discuss the implications of these constraints on the SUSY one-loop contributions to the (anti)neutrino-nucleus deep inelastic scattering. We consider the ratios of neutral current to charged current cross sections, and compare with the deviations of these quantities from the Standard Model predictions implied by the recent NuTeV measurement. We discuss one scenario in which a right-sign effect arises, and show that it is ruled out by the CC data. We also study R parity-violating contributions. Although such effects can account for the violation of the first row CKM unitarity, they can not reproduce the NuTeV anomaly. If NuTeV anomaly is ultimately explained within the SM, R parity-violating resolution of the CKM unitarity problem can be tested in parity-violating electron scattering experiments at SLAC and TJNAF
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
Pion Leptonic Decays and Supersymmetry
We compute supersymmetric contributions to pion leptonic (\pi_{l2}) decays in
the Minimal Supersymmetric Standard Model (MSSM). When R-parity is conserved,
the largest contributions to the ratio R_{e/\mu} = \Gamma[ \pi^+ \to e^+
\nu_e(\gamma)]/\Gamma[ \pi^+ \to \mu^+ \nu_\mu(\gamma)] arise from one-loop
(V-A)x(V-A) corrections. These contributions can be potentially as large as the
sensitivities of upcoming experiments; if measured, they would imply
significant bounds on the chargino and slepton sectors complementary to current
collider limits. We also analyze R-parity violating interactions, which may
produce a detectable deviation in R_{e/\mu} while remaining consistent with all
other precision observables.Comment: 12 pages, 11 figures; included additional electroweak constraints in
analysis, simplified abstract, ref. adde
The LHC Discovery Potential of a Leptophilic Higgs
In this work, we examine a two-Higgs-doublet extension of the Standard Model
in which one Higgs doublet is responsible for giving mass to both up- and
down-type quarks, while a separate doublet is responsible for giving mass to
leptons. We examine both the theoretical and experimental constraints on the
model and show that large regions of parameter space are allowed by these
constraints in which the effective couplings between the lightest neutral Higgs
scalar and the Standard-Model leptons are substantially enhanced. We
investigate the collider phenomenology of such a "leptophilic"
two-Higgs-doublet model and show that in cases where the low-energy spectrum
contains only one light, CP-even scalar, a variety of collider processes
essentially irrelevant for the discovery of a Standard Model Higgs boson
(specifically those in which the Higgs boson decays directly into a
charged-lepton pair) can contribute significantly to the discovery potential of
a light-to-intermediate-mass (m_h < 140 GeV) Higgs boson at the LHC.Comment: 25 pages, LaVTeX, 11 figures, 1 tabl
Fully self-consistent calculations of nuclear Schiff moments
We calculate the Schiff moments of the nuclei 199Hg and 211Ra in completely
self-consistent odd-nucleus mean-field theory by modifying the
Hartree-Fock-Bogoliubov code HFODD. We allow for arbitrary shape deformation,
and include the effects of nucleon dipole moments alongside those of a
CP-violating pion-exchange nucleon-nucleon interaction. The results for 199Hg
differ significantly from those of previous calculations when the CP-violating
interaction is of isovector character.Comment: 7 pages, 2 figure
Relationship between the Montreal Cognitive Assessment and Mini-mental State Examination for assessment of mild cognitive impairment in older adults
BACKGROUND: The Montreal Cognitive Assessment (MoCA) was developed to enable earlier detection of mild cognitive impairment (MCI) relative to familiar multi-domain tests like the Mini-Mental State Exam (MMSE). Clinicians need to better understand the relationship between MoCA and MMSE scores.
METHODS: For this cross-sectional study, we analyzed 219 healthy control (HC), 299 MCI, and 100 Alzheimer's disease (AD) dementia cases from the Alzheimer's Disease Neuroimaging Initiative (ADNI)-GO/2 database to evaluate MMSE and MoCA score distributions and select MoCA values to capture early and late MCI cases. Stepwise variable selection in logistic regression evaluated relative value of four test domains for separating MCI from HC. Functional Activities Questionnaire (FAQ) was evaluated as a strategy to separate dementia from MCI. Equi-percentile equating produced a translation grid for MoCA against MMSE scores. Receiver Operating Characteristic (ROC) analyses evaluated lower cutoff scores for capturing the most MCI cases.
RESULTS: Most dementia cases scored abnormally, while MCI and HC score distributions overlapped on each test. Most MCI cases scored ≥ 17 on MoCA (96.3%) and ≥ 24 on MMSE (98.3%). The ceiling effect (28-30 points) for MCI and HC was less using MoCA (18.1%) versus MMSE (71.4%). MoCA and MMSE scores correlated most for dementia (r = 0.86; versus MCI r = 0.60; HC r = 0.43). Equi-percentile equating showed a MoCA score of 18 was equivalent to MMSE of 24. ROC analysis found MoCA ≥ 17 as the cutoff between MCI and dementia that emphasized high sensitivity (92.3%) to capture MCI cases. The core and orientation domains in both tests best distinguished HC from MCI groups, whereas comprehension/executive function and attention/calculation were not helpful. Mean FAQ scores were significantly higher and a greater proportion had abnormal FAQ scores in dementia than MCI and HC.
CONCLUSIONS: MoCA and MMSE were more similar for dementia cases, but MoCA distributes MCI cases across a broader score range with less ceiling effect. A cutoff of ≥ 17 on the MoCA may help capture early and late MCI cases; depending on the level of sensitivity desired, ≥ 18 or 19 could be used. Functional assessment can help exclude dementia cases. MoCA scores are translatable to the MMSE to facilitate comparison
Activation of p107 by Fibroblast Growth Factor, Which Is Essential for Chondrocyte Cell Cycle Exit, Is Mediated by the Protein Phosphatase 2A/B55α Holoenzyme
The phosphorylation state of pocket proteins during the cell cycle is determined at least in part by an equilibrium between inducible cyclin-dependent kinases (CDKs) and serine/threonine protein phosphatase 2A (PP2A). Two trimeric holoenzymes consisting of the core PP2A catalytic/scaffold dimer and either the B55α or PR70 regulatory subunit have been implicated in the activation of p107/p130 and pRB, respectively. While the phosphorylation state of p107 is very sensitive to forced changes of B55α levels in human cell lines, regulation of p107 in response to physiological modulation of PP2A/B55α has not been elucidated. Here we show that fibroblast growth factor 1 (FGF1), which induces maturation and cell cycle exit in chondrocytes, triggers rapid accumulation of p107-PP2A/B55α complexes coinciding with p107 dephosphorylation. Reciprocal solution-based mass spectrometric analysis identified the PP2A/B55α complex as a major component in p107 complexes, which also contain E2F/DPs, DREAM subunits, and/or cyclin/CDK complexes. Of note, p107 is one of the preferred partners of B55α, which also associates with pRB in RCS cells. FGF1-induced dephosphorylation of p107 results in its rapid accumulation in the nucleus and formation of larger complexes containing p107 and enhances its interaction with E2F4 and other p107 partners. Consistent with a key role of B55α in the rapid activation of p107 in chondrocytes, limited ectopic expression of B55α results in marked dephosphorylation of p107 while B55α knockdown results in hyperphosphorylation. More importantly, knockdown of B55α dramatically delays FGF1-induced dephosphorylation of p107 and slows down cell cycle exit. Moreover, dephosphorylation of p107 in response to FGF1 treatment results in early recruitment of p107 to the MYC promoter, an FGF1/E2F-regulated gene. Our results suggest a model in which FGF1 mediates rapid dephosphorylation and activation of p107 independently of the CDK activities that maintain p130 and pRB hyperphosphorylation for several hours after p107 dephosphorylation in maturing chondrocytes
Photoluminescence Study of the Interface Fluctuation Effect for InGaAs/InAlAs/InP Single Quantum Well with Different Thickness
Photoluminescence (PL) is investigated as a function of the excitation intensity and temperature for lattice-matched
InGaAs/InAlAs quantum well (QW) structures with well thicknesses of 7 and 15 nm, respectively. At low temperature,
interface fluctuations result in the 7-nm QW PL exhibiting a blueshift of 15 meV, a narrowing of the linewidth
(full width at half maximum, FWHM) from 20.3 to 10 meV, and a clear transition of the spectral profile with
the laser excitation intensity increasing four orders in magnitude. The 7-nm QW PL also has a larger blueshift
and FWHM variation than the 15-nm QW as the temperature increases from 10 to ~50 K. Finally, simulations
of this system which correlate with the experimental observations indicate that a thin QW must be more affected by
interface fluctuations and their resulting potential fluctuations than a thick QW. This work provides useful information
on guiding the growth to achieve optimized InGaAs/InAlAs QWs for applications with different QW thicknesses
Extra Families, Higgs Spectrum and Oblique Corrections
The standard model accommodates, but does not explain, three families of
leptons and quarks, while various extensions suggest extra matter families. The
oblique corrections from extra chiral families with relatively light
(weak-scale) masses, , are analyzed and used to constrain the
number of extra families and their spectrum. The analysis is motivated, in
part, by recent N = 2 supersymmetry constructions, but is performed in a
model-independent way. It is shown that the correlations among the
contributions to the three oblique parameters, rather than the contribution to
a particular one, provide the most significant bound. Nevertheless, a single
extra chiral family with a constrained spectrum is found to be consistent with
precision data without requiring any other new physics source. Models with
three additional families may also be accommodated but only by invoking
additional new physics, most notably, a two-Higgs-doublet extension. The
interplay between the spectra of the extra fermions and the Higgs boson(s) is
analyzed in the case of either one or two Higgs doublets, and its implications
are explored. In particular, the precision bound on the SM-like Higgs boson
mass is shown to be significantly relaxed in the presence of an extra
relatively light chiral family.Comment: 20 pages, 8 figures, version for PR
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