3,215 research outputs found
Strong decays of low-lying -wave baryons with QPC model
For further decoding the inner structure of the two excited states
observed by LHCb, we perform a systematical study of the strong decays of the
low-lying -wave and excitations using the quark pair
creation model within the coupling scheme. Combining with the measured
masses and decay properties of and , the
two excited states can be explained as -mode states
and
, respectively. If
such a view were correct, and could be another
interesting channels for experimental exploring of the and
, respectively. Those calculations are good consistent with
the results within the chiral quark model. In addition, for the other missing
-wave and excitations, our predictions indicate that:(i)
the two -mode states are likely to be moderate states with a
width of MeV. The state dominantly decays into
and , while the state decays primarily
through and . (ii) The -mode
states may be moderate states with a widths of about several to dozens of MeV.
Most of the -mode states mainly decay into the -wave
bottomed baryon via the pionic decay processes. Meanwhile, several
-mode states have significant decay rates into . (iii) While, the -mode states are predicted to be very
broad states with a width of about several hundreds MeV. It will be a great
challenge to explore the -mode states in experiments for
their broad widths.Comment: 11 pages, 5 figure
Life fingerprints of nuclear reactions in the body of animals
Nuclear reactions are a very important natural phenomenon in the universe. On the earth, cosmic rays constantly cause nuclear reactions. High energy beams created by medical devices also induce nuclear reactions in the human body. The biological role of these nuclear reactions is unknown. Here we show that the in vivo biological systems are exquisite and sophisticated by nature in influence on nuclear reactions and in resistance to radical damage in the body of live animals. In this study, photonuclear reactions in the body of live or dead animals were induced with 50-MeV irradiation. Tissue nuclear reactions were detected by positron emission tomography (PET) imaging of the induced beta+ activity. We found the unique tissue "fingerprints" of beta+ (the tremendous difference in beta+ activities and tissue distribution patterns among the individuals) are imprinted in all live animals. Within any individual, the tissue "fingerprints" of 15O and 11C are also very different. When the animal dies, the tissue "fingerprints" are lost. The biochemical, rather than physical, mechanisms could play a critical role in the phenomenon of tissue "fingerprints". Radiolytic radical attack caused millions-fold increases in 15O and 11C activities via different biochemical mechanisms, i.e. radical-mediated hydroxylation and peroxidation respectively, and more importantly the bio-molecular functions (such as the chemical reactivity and the solvent accessibility to radicals). In practice biologically for example, radical attack can therefore be imaged in vivo in live animals and humans using PET for life science research, disease prevention, and personalized radiation therapy based on an individual's bio-molecular response to ionizing radiation
Strong decays of the low-lying - and -wave baryons
In this work, we systematically study the OZI-allowed two-body strong decay
properties of - and -wave baryons within the -
coupling scheme in the framework of the quark pair creation model. For a
comparison, we also give the predictions of the chiral quark model. Some model
dependencies can be found in the predictions of two models. The calculations
indicate that: (i) The -wave -mode states most likely
to be relatively narrow states with a width of MeV. Their main
decay channels are , or , or . The
-wave -mode states most might be broad states with a width of
MeV. They dominantly decay into and
channels. Some evidences of these -wave states are most
likely to be observed in the and invariant
mass spectra around the energy range of GeV. (ii) The -wave
-mode excitations may be moderate states with a width of
about dozens of MeV. The -wave -mode states mainly decay into the
-wave charmed baryon via the pionic decay processes. Meanwhile, several
-wave -mode states have significant decay rates into or
. Hence, the and are likely to be interesting channels for
experimental exploration. (iii) Furthermore, the two -wave -mode
excitations and
are most likely to be fairly narrow state with
a width of dozens of MeV, and they mainly decay into . Some
evidences of them might be observed in the invariant mass
spectra around the energy range of GeV.Comment: 12 pages,5 figures, 4 tables. arXiv admin note: text overlap with
arXiv:2208.1011
Geometry and optics calibration of WFCTA prototype telescopes using star light
The Large High Altitude Air Shower Observatory project is proposed to study
high energy gamma ray astronomy ( 40 GeV-1 PeV ) and cosmic ray physics ( 20
TeV-1 EeV ). The wide field of view Cherenkov telescope array, as a component
of the LHAASO project, will be used to study energy spectrum and compositions
of cosmic ray by measuring the total Cherenkov light generated by air showers
and shower maximum depth. Two prototype telescopes have been in operation since
2008. The pointing accuracy of each telescope is crucial to the direction
reconstruction of the primary particles. On the other hand the primary energy
reconstruction relies on the shape of the Cherenkov image on the camera and the
unrecorded photons due to the imperfect connections between photomultiplier
tubes. UV bright stars are used as point-like objects to calibrate the pointing
and to study the optical properties of the camera, the spot size and the
fractions of unrecorded photons in the insensitive areas of the camera.Comment: 5 pages, 6 figures, submitted to Chinese Physics
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