6,403 research outputs found
Boosting Higgs pair production in the final state with multivariate techniques
The measurement of Higgs pair production will be a cornerstone of the LHC
program in the coming years. Double Higgs production provides a crucial window
upon the mechanism of electroweak symmetry breaking and has a unique
sensitivity to the Higgs trilinear coupling. We study the feasibility of a
measurement of Higgs pair production in the final state at
the LHC. Our analysis is based on a combination of traditional cut-based
methods with state-of-the-art multivariate techniques. We account for all
relevant backgrounds, including the contributions from light and charm jet
mis-identification, which are ultimately comparable in size to the irreducible
QCD background. We demonstrate the robustness of our analysis strategy in
a high pileup environment. For an integrated luminosity of
ab, a signal significance of is obtained,
indicating that the final state alone could allow for the
observation of double Higgs production at the High-Luminosity LHC.Comment: 47 pages, 22 figures. v2: updated references, added comparison of
post-MVA kinematic distributions. v3: matches published version in EPJ
An Overview of the Rotational Behavior of Metal--Poor Stars
The present paper describes the behavior of the rotational velocity in
metal--poor stars ([Fe/H]<-0.5 dex) in different evolutionary stages, based on
Vsini values from the literature. Our sample is comprised of stars in the field
and some Galactic globular clusters, including stars on the main sequence, the
red giant branch (RGB), and the horizontal branch (HB). The metal--poor stars
are, mainly, slow rotators, and their Vsini distribution along the HR diagram
is quite homogeneous. Nevertheless, a few moderate to high values of Vsini are
found in stars located on the main sequence and on the HB. We show that the
overall distribution of Vsini values is basically independent of metallicity
for the stars in our sample. In particular, the fast-rotating main sequence
stars in our sample present similar rotation rates as their metal-rich
counterparts, suggesting that some of them may actually be fairly young, in
spite of their low metallicity, or else that at least some of them would be
better classified as blue straggler stars. We do not find significant evidence
of evolution in Vsini values as a function of position on the RGB; in
particular, we do not confirm previous suggestions that stars close to the RGB
tip rotate faster than their less evolved counterparts. While the presence of
fast rotators among moderately cool blue HB stars has been suggested to be due
to angular momentum transport from a stellar core that has retained significant
angular momentum during its prior evolution, we find that any such transport
mechanisms must likely operate very fast as the star arrives on the zero-age HB
(ZAHB), since we do not find a link between evolution off the ZAHB and Vsini
values.
We present an extensive tabulation of all quantities discussed in this paper,
including rotation velocities, temperatures, gravitieComment: 22 pages, 10 figure
Comment on triple gauge boson interactions in the non-commutative electroweak sector
In this comment we present an analysis of electroweak neutral triple gauge
boson couplings projected out of the gauge sector of the extended
non-commutative standard model. A brief overview of the current experimental
situation is given.Comment: 4 page
Rheological transitions in the middle crust:insights from Cordilleran metamorphic core complexes
High-strain mylonitic rocks in Cordilleran metamorphic
core complexes reflect ductile deformation in the middle crust, but in many
examples it is unclear how these mylonites relate to the brittle detachments
that overlie them. Field observations, microstructural analyses, and
thermobarometric data from the footwalls of three metamorphic core complexes
in the Basin and Range Province, USA (the Whipple Mountains, California; the
northern Snake Range, Nevada; and Ruby Mountains–East Humboldt Range,
Nevada), suggest the presence of two distinct rheological transitions in the
middle crust: (1) the brittle–ductile transition (BDT), which depends on
thermal gradient and tectonic regime, and marks the switch from discrete
brittle faulting and cataclasis to continuous, but still localized, ductile
shear, and (2) the localized–distributed transition, or LDT, a deeper, dominantly
temperature-dependent transition, which marks the switch from localized
ductile shear to distributed ductile flow. In this model, brittle normal
faults in the upper crust persist as ductile shear zones below the BDT in
the middle crust, and sole into the subhorizontal LDT at greater depths.<br><br>In metamorphic core complexes, the presence of these two distinct
rheological transitions results in the development of two zones of ductile
deformation: a relatively narrow zone of high-stress mylonite that is
spatially and genetically related to the brittle detachment, underlain by a
broader zone of high-strain, relatively low-stress rock that formed in the
middle crust below the LDT, and in some cases before the detachment was
initiated. The two zones show distinct microstructural assemblages,
reflecting different conditions of temperature and stress during
deformation, and contain superposed sequences of microstructures reflecting
progressive exhumation, cooling, and strain localization. The LDT is not
always exhumed, or it may be obscured by later deformation, but in the
Whipple Mountains, it can be directly observed where high-strain mylonites
captured from the middle crust depart from the brittle detachment along a
mylonitic front
Derivation of a dynamic model of the kinetics of nitrogen uptake throughout the growth of lettuce : calibration and validation
A kinetic model of nitrogen (N) uptake throughout growth was developed for lettuce
cultivated in nutrient solution under varying natural light conditions. The model couples
nitrogen uptake with dry matter accumulation using a two-compartment mechanistic
approach, incorporating structural and non-structural pools. Maximum nitrogen uptake
rates are assumed to decline with shoot dry weight, to allow for the effects of plant
age. The model was parameterized using data from the literature, and calibrated for
differences in light intensity using an optimization algorithm utilizing data from three
experiments in different growing seasons. The calibrated model was validated against
the data from two independent experiments conducted under different light conditions.
Results showed that the model made good predictions of nitrogen uptake by plants from
seedlings to maturity under fluctuating light levels in a glasshouse. Plants grown at a
higher light intensity showed larger maximum nitrogen uptake rates, but the effect of
light intensity declined towards plant maturity
The Standard Model on Non-Commutative Space-Time: Electroweak Currents and Higgs Sector
In this article we review the electroweak charged and neutral currents in the
Non-Commutative Standard Model (NCSM) and compute the Higgs and Yukawa parts of
the NCSM action. With the aim to make the NCSM accessible to phenomenological
considerations, all relevant expressions are given in terms of physical fields
and Feynman rules are provided.Comment: 33 pages, axodraw.sty; shortened, comments and references added,
version to appear in EPJ
Differential cAMP signaling at hippocampal output synapses
cAMP is a critical second messenger involved in synaptic transmission and synaptic plasticity. Here, we show that activation of the adenylyl cyclase by forskolin and application of the cAMP-analog Sp-5,6-DCl-cBIMPS both mimicked and occluded tetanus-induced long-term potentiation (LTP) in subicular bursting neurons, but not in subicular regular firing cells. Furthermore, LTP in bursting cells was inhibited by protein kinase A (PKA) inhibitors Rp-8-CPT-cAMP and H-89. Variations in the degree of EPSC blockade by the low-affinity competitive AMPA receptor-antagonist {gamma}-d-glutamyl-glycine ({gamma}-DGG), analysis of the coefficient of variance as well as changes in short-term potentiation suggest an increase of glutamate concentration in the synaptic cleft after expression of LTP. We conclude that presynaptic LTP in bursting cells requires activation of PKA by a calcium-dependent adenylyl cyclase while LTP in regular firing cells is independent of elevated cAMP levels. Our results provide evidence for a differential role of cAMP in LTP at hippocampal output synapses
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