1,462 research outputs found
Rare earth magnetism in CeFeAsO: A single crystal study
Single crystals of CeFeAsO, large enough to study the anisotropy of the
magnetic properties, were grown by an optimized Sn-flux technique. The high
quality of our single crystals is apparent from the highest residual
resistivity ratio, RRR = 12, reported among undoped RFeAsO compounds (R=rare
earth) as well as sharp anomalies in resistivity, specific heat, C(T), and
thermal expansion at the different phase transitions. The magnetic
susceptibility chi(T) presents a large easy-plane anisotropy consistent with
the lowest crystal electric field doublet having a dominant Gamma_6 character.
Curie-Weiss like susceptibilities for magnetic field parallel and perpendicular
to the crystallographic c-axis do not reveal an influence of a staggered field
on the Ce site induced by magnetic ordering of the Fe. Furthermore, the
standard signatures for antiferromagnetic order of Ce at T_N = 3.7 K observed
in chi(T) and C(T) are incompatible with a Zeeman splitting Delta = 10 K of the
CEF ground state doublet at low temperature due to the Fe-magnetic order as
previously proposed. Our results can be reconciled with the earlier observation
by assuming a comparatively stronger effect of the Ce-Ce exchange leading to a
reduction of this Zeeman splitting below 15 K.Comment: 15 pages, 6 figures, added section on magn. susceptibilit
Higher-order multipole amplitude measurement in
Using events collected with the BESIII detector at
the BEPCII storage ring, the higher-order multipole amplitudes in the radiative
transition are measured.
A fit to the production and decay angular distributions yields
and , where the first
errors are statistical and the second systematic. Here denotes the
normalized magnetic quadrupole amplitude and the normalized electric
octupole amplitude. This measurement shows evidence for the existence of the
signal with statistical significance and is consistent with
the charm quark having no anomalous magnetic moment.Comment: 14 pages, 4 figure
Observation of decays into vector meson pairs , , and
Decays of to vector meson pairs , and
are observed for the first time using
\psip events accumulated at the BESIII detector at the BEPCII
collider. The branching fractions are measured to be , , and , for , , and ,
respectively. The observation of decays into a pair of vector
mesons , and indicates that the hadron
helicity selection rule is significantly violated in decays. In
addition, the measurement of gives the rate of doubly
OZI-suppressed decay. Branching fractions for and
decays into other vector meson pairs are also measured with improved precision.Comment: 4 pages, 2 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
Observation and study of the decay
We report the observation and study of the decay
using events
collected with the BESIII detector. Its branching fraction, including all
possible intermediate states, is measured to be
. We also report evidence for a structure,
denoted as , in the mass spectrum in the GeV/
region. Using two decay modes of the meson ( and
), a simultaneous fit to the mass spectra is
performed. Assuming the quantum numbers of the to be , its
significance is found to be 4.4, with a mass and width of MeV/ and MeV, respectively, and a
product branching fraction
. Alternatively, assuming , the
significance is 3.8, with a mass and width of MeV/ and MeV, respectively, and a product
branching fraction
. The angular distribution of
is studied and the two assumptions of the
cannot be clearly distinguished due to the limited statistics. In all
measurements the first uncertainties are statistical and the second systematic.Comment: 10 pages, 6 figures and 4 table
Study of radiative decays into a vector meson
The decays () are studied with
a sample of radiative \psip\to\gamma\chi_{cJ} events in a sample of
(1.06\pm0.04)\times 10^{8} \psip events collected with the BESIII detector.
The branching fractions are determined to be: , , and . The decay is observed for the first time. Upper limits at the 90% confidence
level on the branching fractions for and \chict decays into these
final states are determined. In addition, the fractions of the transverse
polarization component of the vector meson in decays
are measured to be for , for , and for , respectively. The first errors are statistical and the second
ones are systematic.Comment: 8 pages, 3 figure
Observation of and confirmation of its large branching fraction
The baryonic decay is observed, and the
corresponding branching fraction is measured to be
, where the first uncertainty is statistical
and second systematic. The data sample used in this analysis was collected with
the BESIII detector operating at the BEPCII double-ring collider with
a center-of-mass energy of 4.178~GeV and an integrated luminosity of
3.19~fb. The result confirms the previous measurement by the CLEO
Collaboration and is of greatly improved precision, which may deepen our
understanding of the dynamical enhancement of the W-annihilation topology in
the charmed meson decays
First Observation of the Decays chi_{cJ} -> pi^0 pi^0 pi^0 pi^0
We present a study of the P-wave spin -triplet charmonium chi_{cJ} decays
(J=0,1,2) into pi^0 pi^0 pi^0 pi^0. The analysis is based on 106 million
\psiprime decays recorded with the BESIII detector at the BEPCII electron
positron collider. The decay into the pi^0 pi^0 pi^0 pi^0 hadronic final state
is observed for the first time. We measure the branching fractions B(chi_{c0}
-> pi^0 pi^0 pi^0 pi^0)=(3.34 +- 0.06 +- 0.44)*10^{-3}, B(chi_{c1} -> pi^0 pi^0
pi^0 pi^0)=(0.57 +- 0.03 +- 0.08)*10^{-3}, and B(chi_{c2} -> pi^0 pi^0 pi^0
pi^0)=(1.21 +- 0.05 +- 0.16)*10^{-3}, where the uncertainties are statistical
and systematical, respectively.Comment: 7 pages, 3 figure
Study of and
The decays and have been
investigated with a sample of 225.2 million events collected with the
BESIII detector at the BEPCII collider. The branching fractions are
determined to be and . Distributions of the angle
between the proton or anti-neutron and the beam direction are well
described by the form , and we find
for and
for . Our branching-fraction
results suggest a large phase angle between the strong and electromagnetic
amplitudes describing the decay.Comment: 16 pages, 13 figures, the 2nd version, submitted to PR
Study of and and
We study the decays of and to the final states
and based on a single
baryon tag method using data samples of
and events collected with
the BESIII detector at the BEPCII collider. The decays to
are observed for the first time. The
measured branching fractions of and
are in good agreement with, and much
more precise, than the previously published results. The angular parameters for
these decays are also measured for the first time. The measured angular decay
parameter for , , is found to be negative, different to the other
decay processes in this measurement. In addition, the "12\% rule" and isospin
symmetry in the and and
systems are tested.Comment: 11 pages, 7 figures. This version is consistent with paper published
in Phys.Lett. B770 (2017) 217-22
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