4,251 research outputs found
Seeking for sterile neutrinos with displaced leptons at the LHC
We study the signal of long-lived sterile neutrino at the LHC produced
through the decay of the boson. It decays into charged lepton and jets. The
characteristic signature is a hard prompt lepton and a lepton from the
displaced decay of the sterile neutrino, which leads to a bundle of displaced
tracks with large transverse impact parameter. Different from other studies, we
neither reconstruct the displaced vertex nor place requirement on its invariant
mass to maintain sensitivity for low sterile neutrino masses. Instead, we focus
on the displaced track from the lepton. A difficulty for low mass sterile
neutrino study is that the displaced lepton is usually \textit{non-isolated}.
Therefore, leptons from heavy flavor quark is the major source of background.
We closely follow a search for displaced electron plus muon search at CMS and
study their control regions, which is related to our signal regions, in great
detail to develop a robust estimation of the background for our signals. After
further optimization on the signal limiting the number of jets, low and
large lepton displacement to suppress SM background, we reach an
exclusion sensitivity of about () for the mixing angle
square at 10 (2) GeV sterile neutrino mass respectively. The strategy we
propose can cover the light sterile masses complimentary to beam dump and
forward detector experiments.Comment: 22 pages, 6 figures, 1 table; v2: matched to Journal version
Effects of time-varying in SNLS3 on constraining interacting dark energy models
It has been found that, for the Supernova Legacy Survey three-year (SNLS3)
data, there is strong evidence for the redshift-evolution of color-luminosity
parameter . In this paper, adopting the -cold-dark-matter (CDM)
model and considering its interacting extensions (with three kinds of
interaction between dark sectors), we explore the evolution of and its
effects on parameter estimation. In addition to the SNLS3 data, we also take
into account the Planck distance priors data of the cosmic microwave background
(CMB), the galaxy clustering (GC) data extracted from SDSS DR7 and BOSS, as
well as the direct measurement of Hubble constant from the Hubble Space
Telescope (HST) observation. We find that, for all the interacting dark energy
(IDE) models, adding a parameter of can reduce by 34,
indicating that is ruled out at 5.8 confidence level
(CL). Furthermore, it is found that varying can significantly change
the fitting results of various cosmological parameters: for all the dark energy
models considered in this paper, varying yields a larger
and a larger ; on the other side, varying yields a smaller for
the CDM model, but has no impact on for the three IDE models. This
implies that there is a degeneracy between and . Our work shows
that the evolution of is insensitive to the interaction between dark
sectors, and then highlights the importance of considering 's evolution
in the cosmology fits.Comment: 11 pages, 6 figures, 1 table; revised version accepted by EPJC. arXiv
admin note: substantial text overlap with arXiv:1310.6109, arXiv:1312.018
Heterogeneity in structurally arrested hard spheres
When cooled or compressed sufficiently rapidly, a liquid vitrifies into a glassy amorphous state. Vitrification in a dense liquid is associated with jamming of the particles. For hard spheres, the density and degree of order in the final structure depend on the compression rate: simple intuition suggests, and previous computer simulation demonstrates, that slower compression results in states that are both denser and more ordered. In this work, we use the Lubachevsky-Stillinger algorithm to generate a sequence of structurally arrested hard-sphere states by varying the compression rate. We find that while the degree of order, as measured by both bond-orientation and translation order parameters, increases monotonically with decreasing compression rate, the density of the arrested state first increases, then decreases, then increases again, as the compression rate decreases, showing a minimum at an intermediate compression rate. Examination of the distribution of the local order parameters and the distribution of the root-mean-square fluctuation of the particle positions, as well as direct visual inspection of the arrested structures, reveal that they are structurally heterogeneous, consisting of disordered, amorphous regions and locally ordered crystal-like domains. In particular, the low-density arrested states correspond with many interconnected small crystal clusters that form a polycrystalline network interspersed in an amorphous background, suggesting that jamming by the domains may be an important mechanism for these states
Partitioned time integration methods for hardware in the loop based on linearly implicit L-Stable Rosenbrock methods
Hardware in the loop based on dynamic substructuring was conceived to be a
hybrid numerical-experimental technique to simulate the non-linear behaviour of an emulated
structure. Its challenge is to ensure that both numerical and physical substructures interact in
real time by means of actuators –transfer systems-. With this objective in mind, the
development and implementation of partitioned real-time compatible Rosenbrock algorithms
are presented in this paper. In detail, we shortly introduce monolithic linearly implicit L-stable
algorithms with two stages; and in view of the analysis of complex emulated structures, we
present a novel interfield partitioned algorithm. Both the stability and accuracy properties of
the proposed algorithm are examined through analytical and numerical studies carried out on
Single-DoF model problems. Moreover, a novel test rig conceived to perform both linear and
nonlinear substructure tests is introduced, and tests on a two-DoF split-mass system are
illustrated. The drawbacks of this algorithm are underlined and improvements are introduced
on a companion solution procedure
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