1,271 research outputs found
Correcting for the solar wind in pulsar timing observations: the role of simultaneous a nd l ow-frequency observations
The primary goal of the pulsar timing array projects is to detect
ultra-low-frequency gravitational waves. The pulsar data sets are affected by
numerous noise processes including varying dispersive delays in the
interstellar medium and from the solar wind. The solar wind can lead to rapidly
changing variations that, with existing telescopes, can be hard to measure and
then remove. In this paper we study the possibility of using a low frequency
telescope to aid in such correction for the Parkes Pulsar Timing Array (PPTA)
and also discuss whether the ultra-wide-bandwidth receiver for the FAST
telescope is sufficient to model the solar wind variations. Our key result is
that a single wide-bandwidth receiver can be used to model and remove the
effect of the solar wind. However, for pulsars that pass close to the Sun such
as PSR J1022+1022, the solar wind is so variable that observations at two
telescopes separated by a day are insufficient to correct the solar wind
effect.Comment: accepted by RA
Electromagnetic decays of vector mesons as derived from QCD sum rules
We apply the method of QCD sum rules in the presence of external
electromagnetic fields to the problem of the electromagnetic
decays of various vector mesons, such as , and . The induced condensates obtained previously
from the study of baryon magnetic moments are adopted, thereby ensuring the
parameter-free nature of the present calculation. Further consistency is
reinforced by invoking various QCD sum rules for the meson masses. The
numerical results on the various radiative decays agree very well with the
experimental data.Comment: To appear in Phys. Lett.
Signature of the +jet and dijet production mediated by an excited quark with QCD next-to-leading order accuracy at the LHC
We present a detailed study of the production and decay of the excited quark
at the QCD next-to-leading order (NLO) level at the Large Hadron Collider,
using the narrow width approximation and helicity amplitudes method. We find
that the QCD NLO corrections can tighten the constraints on the model
parameters and reduce the scale dependencies of the total cross sections. We
discuss the signals of the excited quark production with decay mode
and , and present several
important kinematic distributions. Moreover, we give the upper limits of the
excited quark excluded mass range and the allowed parameter space for the
coupling constants and the excited quark mass.Comment: 20 pages, 13 figures; version published in PR
Threshold resummation for the production of a color sextet (antitriplet) scalar at the LHC
We investigate threshold resummation effects in the production of a color
sextet (antitriplet) scalar at next-to-next-to-leading logarithmic (NNLL) order
at the LHC in the frame of soft-collinear effective theory. We show the total
cross section and the rapidity distribution with NLO+NNLL accuracy, and we
compare them with the NLO results. Besides, we use recent dijet data at the LHC
to give the constraints on the couplings between the colored scalars and
quarks.Comment: 21 pages,9 figures,3 tables; Version published in EPJ
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