557 research outputs found
Study of the P-wave charmonium state \chi_{cJ} in \psi(2S) decays
The processes , and have been studied using a sample of produced
decays. We determine the total width of the to be
MeV. We present the first
measurement of the branching fraction , where the first error is statistical and the
second one systematic. Branching fractions of and
are also reported.Comment: 10 pages, revtex, 3 figures, 2 table
In-orbit demonstration of X-ray pulsar navigation with the Insight-HXMT satellite
In this work, we report the in-orbit demonstration of X-ray pulsar navigation
with Insight-Hard X-ray Modulation Telescope (Insight-HXMT), which was launched
on Jun. 15th, 2017. The new pulsar navigation method 'Significance Enhancement
of Pulse-profile with Orbit-dynamics' (SEPO) is adopted to determine the orbit
with observations of only one pulsar. In this test, the Crab pulsar is chosen
and observed by Insight-HXMT from Aug. 31th to Sept. 5th in 2017. Using the
5-day-long observation data, the orbit of Insight-HXMT is determined
successfully with the three telescopes onboard - High Energy X-ray Telescope
(HE), Medium Energy X-ray Telescope (ME) and Low Energy X-ray Telescope (LE) -
respectively. Combining all the data, the position and velocity of the
Insight-HXMT are pinpointed to within 10 km (3 sigma) and 10 m/s (3 sigma),
respectively.Comment: Accepted by the Astrophysical Journal Supplemen
Discovery of delayed spin-up behavior following two large glitches in the Crab pulsar, and the statistics of such processes
Glitches correspond to sudden jumps of rotation frequency () and its
derivative () of pulsars, the origin of which remains not well
understood yet, partly because the jump processes of most glitches are not well
time-resolved. There are three large glitches of the Crab pulsar, detected in
1989, 1996 and 2017, which were found to have delayed spin-up processes before
the normal recovery processes. Here we report two additional glitches of the
Crab pulsar occurred in 2004 and 2011 for which we discovered delayed spin up
processes, and present refined parameters of the largest glitch occurred in
2017. The initial rising time of the glitch is determined as hour. We
also carried out a statistical study of these five glitches with observed
spin-up processes. The two glitches occurred in 2004 and 2011 have delayed
spin-up time scales () of \,days and \,days,
respectively. We find that the vs. relation
of these five glitches is similar to those with no detected delayed spin-up
process, indicating that they are similar to the others in nature except that
they have larger amplitudes. For these five glitches, the amplitudes of the
delayed spin-up process () and recovery process
(), their time scales (, ), and
permanent changes in spin frequency () and total frequency
step () have positive correlations. From these
correlations, we suggest that the delayed spin-up processes are common for all
glitches, but are too short and thus difficult to be detected for most
glitches.Comment: 25 pages, 8 figure
Observation of in
Using a sample of events recorded with
the BESIII detector at the symmetric electron positron collider BEPCII, we
report the observation of the decay of the charmonium state
into a pair of mesons in the process
. The branching fraction is measured for the first
time to be , where the first uncertainty is
statistical, the second systematic and the third is from the uncertainty of
. The mass and width of the are
determined as MeV/ and
MeV.Comment: 13 pages, 6 figure
The First GECAM Observation Results on Terrestrial Gamma-ray Flashes and Terrestrial Electron Beams
Gravitational-wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) is a space-borne instrument dedicated to monitoring high-energy
transients, including Terrestrial Gamma-ray Flashes (TGFs) and Terrestrial
Electron Beams (TEBs). We implemented a TGF/TEB search algorithm for GECAM,
with which 147 bright TGFs, 2 typical TEBs and 2 special TEB-like events are
identified during an effective observation time of 9 months. We show
that, with gamma-ray and charged particle detectors, GECAM can effectively
identify and distinguish TGFs and TEBs, and measure their temporal and spectral
properties in detail. A very high TGF-lightning association rate of 80\%
is obtained between GECAM and GLD360 in east Asia region.Comment: The paper was accepted by Geophysical Research Letters on June 16th,
202
- …