435 research outputs found
The Effects of Fourth Generation on the double Lepton Polarization in B \rar K \ell^+ \ell^- decay
This study investigates the influence of the fourth generation quarks on the
double lepton polarizations in B \rar K \ell^+ \ell^- decay. Taking
|V_{t's}V_{t'b}|\sim \{0.01-0.03\} with phase about 100^\circ, which is
consistent with the b\to s\ell^+\ell^- rate and the B_s mixing parameter Delta
m_{B_s}$, we obtain that the double lepton(muon and tau) polarizations are
quite sensitive to the existence of fourth generation. It can serve as a good
tool to search for new physics effects, precisely, to indirect search for the
fourth generation quarks(t', b').Comment: 30 pages, 27 figure
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
JUNO Conceptual Design Report
The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine
the neutrino mass hierarchy using an underground liquid scintillator detector.
It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants
in Guangdong, China. The experimental hall, spanning more than 50 meters, is
under a granite mountain of over 700 m overburden. Within six years of running,
the detection of reactor antineutrinos can resolve the neutrino mass hierarchy
at a confidence level of 3-4, and determine neutrino oscillation
parameters , , and to
an accuracy of better than 1%. The JUNO detector can be also used to study
terrestrial and extra-terrestrial neutrinos and new physics beyond the Standard
Model. The central detector contains 20,000 tons liquid scintillator with an
acrylic sphere of 35 m in diameter. 17,000 508-mm diameter PMTs with high
quantum efficiency provide 75% optical coverage. The current choice of
the liquid scintillator is: linear alkyl benzene (LAB) as the solvent, plus PPO
as the scintillation fluor and a wavelength-shifter (Bis-MSB). The number of
detected photoelectrons per MeV is larger than 1,100 and the energy resolution
is expected to be 3% at 1 MeV. The calibration system is designed to deploy
multiple sources to cover the entire energy range of reactor antineutrinos, and
to achieve a full-volume position coverage inside the detector. The veto system
is used for muon detection, muon induced background study and reduction. It
consists of a Water Cherenkov detector and a Top Tracker system. The readout
system, the detector control system and the offline system insure efficient and
stable data acquisition and processing.Comment: 328 pages, 211 figure
Measurements of and Production in + Collisions at = 200 GeV
We report measurements of charmed-hadron (, ) production cross
sections at mid-rapidity in + collisions at a center-of-mass energy of
200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the
hadronic decays , and their charge conjugates,
covering the range of 0.62.0 GeV/ and 2.06.0 GeV/ for
and , respectively. From this analysis, the charm-pair production cross
section at mid-rapidity is = 170 45
(stat.) (sys.) b. The extracted charm-pair cross section is
compared to perturbative QCD calculations. The transverse momentum differential
cross section is found to be consistent with the upper bound of a Fixed-Order
Next-to-Leading Logarithm calculation.Comment: 15 pages, 16 figures. Revised version submitted to Phys. Rev.
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