138,801 research outputs found
Erratum to “The lollipop graph is determined by its Q-spectrum”
AbstractThe proof of Theorem 3.3 in [Y. Zhang, X. Liu, B. Zhang, X. Yong, The lollipop graph is determined by its Q-spectrum, Discrete Math. 309 (2009) 3364–3369] is not correct. Actually, in the development of PA(G1)(λ), the authors missed several products into addition, which makes the rest of the proof invalid. Note that the statement of the theorem is true. Here, we give a correct proof
Radiation Campaign of HPK Prototype LGAD sensors for the High-Granularity Timing Detector (HGTD)
We report on the results of a radiation campaign with neutrons and protons of
Low Gain Avalanche Detectors (LGAD) produced by Hamamatsu (HPK) as prototypes
for the High-Granularity Timing Detector (HGTD) in ATLAS. Sensors with an
active thickness of 50~m were irradiated in steps of roughly 2 up
to a fluence of . As a function of the
fluence, the collected charge and time resolution of the irradiated sensors
will be reported for operation at
Study of boson production in association with beauty and charm
The associated production of a boson with a jet originating from either a
light parton or heavy-flavor quark is studied in the forward region using
proton-proton collisions. The analysis uses data corresponding to integrated
luminosities of 1.0 and collected with the LHCb detector
at center-of-mass energies of 7 and 8 TeV, respectively. The bosons are
reconstructed using the decay and muons with a transverse
momentum, , larger than 20 GeV in the pseudorapidity range
GeV
and . The sum of the muon and jet momenta must satisfy
GeV. The fraction of jet events that originate from beauty
and charm quarks is measured, along with the charge asymmetries of the
and production cross-sections. The ratio of the jet to
jet production cross-sections is also measured using the
decay. All results are in agreement with Standard Model predictions
The Spectral Features of Disk and Corona with Mass Evaporation in the Low/Hard State
We investigate the spectral features of accretion flows composed of an outer
cool, optically thick disk and inner hot, optically thin, advection dominated
accretion flows (ADAF) within the framework of disk and corona with mass
evaporation (Liu et al. 2002a). In this work, both the magnetic field and
Compton scattering of soft photons from the disk by electrons in the corona are
included to calculate the evaporation rates at different distances. The disk is
truncated at the distance where the evaporation rate equals to the accretion
rate (). For a series of accretion rates,
the corresponding truncation radii are calculated out, with which we are able
to calculate the emergent spectra from the inner ADAF + outer disk + corona. At
very low accretion rates, the spectra are similar to that of a pure ADAF
because the disk is truncated at large distances. The disk component becomes
important at high accretion rates since the truncation occurs at small
distances. An anti-correlation between the Eddington ratio and the hard X-ray photon index at low/hard states is predicted by the model. Comparing the theoretical
results with observations, we find that our model can reproduce the
anti-correlation between the Eddington ratio and the hard X-ray photon
index observed for the X-ray binary XTE J1118+480.Comment: 11 pages and 7 figures, published by PAS
Absolute luminosity measurements with the LHCb detector at the LHC
Absolute luminosity measurements are of general interest for colliding-beam
experiments at storage rings. These measurements are necessary to determine the
absolute cross-sections of reaction processes and are valuable to quantify the
performance of the accelerator. Using data taken in 2010, LHCb has applied two
methods to determine the absolute scale of its luminosity measurements for
proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In
addition to the classic "van der Meer scan" method a novel technique has been
developed which makes use of direct imaging of the individual beams using
beam-gas and beam-beam interactions. This beam imaging method is made possible
by the high resolution of the LHCb vertex detector and the close proximity of
the detector to the beams, and allows beam parameters such as positions, angles
and widths to be determined. The results of the two methods have comparable
precision and are in good agreement. Combining the two methods, an overall
precision of 3.5% in the absolute luminosity determination is reached. The
techniques used to transport the absolute luminosity calibration to the full
2010 data-taking period are presented.Comment: 48 pages, 19 figures. Results unchanged, improved clarity of Table 6,
9 and 10 and corresponding explanation in the tex
Observation of radiative decay and evidence for
A search for radiative decays of the -wave spin singlet charmonium
resonance is performed based on events
collected with the BESIII detector operating at the BEPCII storage ring. Events
of the reaction channels and are
observed with a statistical significance of and ,
respectively, for the first time. The branching fractions of and are measured to be
and , respectively, where the first errors are
statistical and the second are systematic uncertainties.Comment: 7 pages, 2 figure
Observation of an anomalous line shape of the mass spectrum near the mass threshold in
Using events collected by the BESIII experiment
in 2012, we study the
process and observe a significant abrupt change in the slope of the
invariant mass distribution at the
proton-antiproton () mass threshold. We use two models to
characterize the line shape around
: one which explicitly incorporates the opening of a
decay threshold in the mass spectrum (Flatt\'{e} formula), and another which is
the coherent sum of two resonant amplitudes. Both fits show almost equally good
agreement with data, and suggest the existence of either a broad state around
with strong couplings to final states or a
narrow state just below the mass threshold. Although we cannot
distinguish between the fits, either one supports the existence of a
molecule-like state or bound state with greater than significance
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
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