19,730 research outputs found
Looking at the photoproduction of massive gauge bosons at the LHeC
In this contribution we report on the investigation of the photoproduction of
W and Z bosons in the planned electron-proton/nucleus collider, the LHeC. The
production cross sections and the number of events are provided and theoretical
uncertainties are discussed. We also analyze the sensitivity of the LHeC
experiment to physics beyond Standard Model by studying the role played by
anomalous WWgamma coupling in the presented process.Comment: Contribution to the proceedings of the XXI International Workshop on
Deep-Inelastic Scattering and Related Subjects (DIS2013), Marseille, 22-26
April 201
Quarkonium plus prompt-photon associated hadroproduction and nuclear shadowing
The quarkonium hadroproduction in association with a photon at high energies
provides a probe of the dynamics of the strong interactions as it is dependent
on the nuclear gluon distribution. Therefore, it could be used to constrain the
behavior of the nuclear gluon distribution in proton-nucleus and
nucleus-nucleus collisions. Such processes are useful to single out the
magnitude of the shadowing/antishadowing effects in the nuclear parton
densities. In this work we investigate the influence of nuclear effects in the
production of JPsi + photon and Upsilon + photon and estimate the transverse
momentum dependence of the nuclear modification factors. The theoretical
framework considered in the JPsi (Upsilon) production associated with a direct
photon at the hadron collider is the non-relativistic QCD (NRQCD) factorization
formalism.Comment: 8 pages, 4 figures. Final version to be published in European
Physical Journal
Inclusive and exclusive dilepton photoproduction at high energies
In this work we investigate the inclusive and exclusive photoproduction of
dileptons, which is relevant for the physics programme to be studied in the
proposed electron-proton collider, the LHeC. In the inclusive case, the process
is sensitive to the parton distribution functions in the photon whereas the
exclusive channel is connected to the small- QCD dynamics. For the latter,
we investigate the role played by saturation physics at a very high energy
scenario. The estimates for production cross sections and the number of events
are presented.Comment: 5 pages, version to be published in Physical Review
Reconstruction of the Cosmic Equation of State for High Redshift
We investigate the possibilities of reconstructing the cosmic equation of
state (EoS) for high redshift. In order to obtain general results, we use two
model-independent approaches. The first reconstructs the EoS using comoving
distance and the second makes use of the Hubble parameter data. To implement
the first method, we use a recent set of Gamma-Ray Bursts (GRBs) measures. To
implement the second method, we generate simulated data using the Sandage-Loeb
() effect; for the fiducial model, we use the model. In both
cases, the statistical analysis is conducted through the Gaussian processes
(non-parametric). In general, we demonstrate that this methodology for
reconstructing the EoS using a non-parametric method plus a model-independent
approach works appropriately due to the feasibility of calculation and the ease
of introducing a priori information ( and ). In the near
future, following this methodology with a higher number of high quality data
will help obtain strong restrictions for the EoS.Comment: 9 pages, 5 figure
Quantiles for Counts
This paper studies the estimation of conditional quantiles of counts. Given the discreteness of the data, some smoothness has to be artificially imposed on the problem. The methods currently available to estimate quantiles of count data either assume that the counts result from the discretization of a continuous process, or are based on a smoothed objective function. However, these methods have several drawbacks. We show that it is possible to smooth the data in a way that allows inference to be performed using standard quantile regression techniques. The performance and implementation of the estimator are illustrated by simulations and an application.Asymmetric maximum likelihood, Jittering, Maximum score estimator, Quantile regression, Smoothing.
Quantiles for Fractions and Other Mixed Data
This paper studies the estimation of quantile regression for fractional data, focusing on the case where there are mass-points at zero or/and one. More generally, we propose a simple strategy for the estimation of the conditional quantiles of data from mixed distributions, which combines standard results on the estimation of censored and Box-Cox quantile regressions. The implementation of the proposed method is illustrated using a well-known dataset.
Discrepancies between empirical and theoretical models of the flaring solar chromosphere and their possible resolution
Models of the solar chromosphere during flaring deduced theoretically or empirically are compared. Marked discrepancies are noted and various reasons are offered to explain their existence. A means is presented for testing theoretical heating models (electron heating) by analyzing the net energy loss rates in (observed) empirical atmospheres and inverting the flare energy equation to deduce the parameters of the supposed heating mechanism
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