Highlights
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Prompt neutron emission in 250No spontaneous fission associated with ground and isomeric state decays
2024, 48(6): 064002. doi: 10.1088/1674-1137/ad361a
The complete-fusion reaction 204Pb(48Ca,2n)250No was used to study two activities of 250No with distinct half-lives. A total of 1357 events were observed in the SFiNx neutron detection system. The average number of neutrons emitted per spontaneous fission of 250No was determined to be$ (4.1 \pm 0.1) $ . The unusually symmetrical shape of the prompt neutron multiplicity distribution was restored and presented for the first time. Statistical tests were performed to compare the prompt neutron multiplicity distributions associated with the ground state and K-isomer state decays. -
Optimization of performance of the KM2A full array using the Crab Nebula
2024, 48(6): 065001. doi: 10.1088/1674-1137/ad2e82
The full array of the Large High Altitude Air Shower Observatory (LHAASO) has been in operation since July 2021. For its kilometer-square array (KM2A), we optimized the selection criteria for very high and ultra-high energy γ-rays using data collected from August 2021 to August 2022, resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%, compared with that of previous cuts. With the implementation of these new selection criteria, the angular resolution was also significantly improved by approximately 10% at tens of TeV. Other aspects of the full KM2A array performance, such as the pointing error, were also calibrated using the Crab Nebula. The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model, which is consistent with the previous results from LHAASO and other experiments. -
Impacts of gravitational-wave background from supermassive black hole binaries on the detection of compact binaries by LISA
2024, 48(6): 065103. doi: 10.1088/1674-1137/ad34c2
In the frequency band of the Laser Interferometer Space Antenna (LISA), extensive research has been conducted on the impact of foreground confusion noise generated by galactic binaries within the Milky Way Galaxy. Additionally, recent evidence of a stochastic signal, announced by the NANOGrav, EPTA, PPTA, CPTA, and InPTA, indicates that the stochastic gravitational-wave background (SGWB) generated by supermassive black hole binaries (SMBHBs) can contribute strong background noise within the LISA band. Given the presence of such strong noise, it is expected to have significant impacts on LISA's scientific missions. In this study, we investigate the impacts of the SGWB generated by SMBHBs on the detection of individual massive black hole binaries, verified galactic binaries, and extreme mass ratio inspirals in the context of LISA. We find it essential to resolve and eliminate the excess noise from the SGWB to guarantee the success of LISA's missions.
Just Accepted
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Searching for 76Ge neutrinoless double beta decay with the CDEX-1B experiment
Published: 2024-06-30
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Masses and decays of triply-heavy pentaquarks
Published: 2024-06-30
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Determination of the number of ψ(3686) events taken at BESIII
Published: 2024-06-30
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Spatial covariant gravity with two degrees of freedom in the presence of an auxiliary scalar field: Perturbation analysis
2024, 48(8): 085101-085101-15. doi: 10.1088/1674-1137/ad47a9Show AbstractWe investigate a class of gravity theories respecting only spatial covariance, termed spatially covariant gravity, in the presence of an auxiliary scalar field. We examine the conditions on the Lagrangian required to eliminate scalar degrees of freedom, allowing only two tensorial degrees of freedom to propagate. Instead of strict constraint analysis, in this paper, we employ the perturbation method and focus on the necessary conditions to evade the scalar mode at the linear order in perturbations around a cosmological background. Beginning with a general action and solving the auxiliary perturbation variables in terms of a would-be dynamical scalar mode, we derive the condition to remove its kinetic term, thus ensuring that no scalar mode propagates. As an application of the general condition, we study a polynomial-type Lagrangian as a concrete example, in which all monomials are spatially covariant scalars containing two derivatives. We find that the auxiliary scalar field is essential, and new terms in the Lagrangian are allowed. Our analysis provides insights into constructing gravity theories with two degrees of freedom in the extended framework of spatially covariant gravity.
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Amplitude analysis of the decays
${\boldsymbol D^{\bf 0}\bf\to\pi^+\pi^-\pi^+\pi^-} $ and${\boldsymbol D^{\bf 0}\bf\to\pi^+\pi^-\pi^0\pi^0} $ 2024, 48(8): 083001-083001-28. doi: 10.1088/1674-1137/ad3d4dShow AbstractUsing$ e^+e^- $ annihilation data corresponding to an integrated luminosity of 2.93$ \rm fb^{-1} $ taken at the center-of-mass energy$ \sqrt{s}=3.773 $ GeV with the BESIII detector, a joint amplitude analysis is performed on the decays$ D^0\to\pi^+\pi^-\pi^+\pi^- $ and$ D^0\to\pi^+\pi^-\pi^0\pi^0 $ (non-η). The fit fractions of individual components are obtained, and large interferences among the dominant components of the decays$ D^{0}\to a_{1}(1260)\pi $ ,$ D^{0}\to\pi(1300)\pi $ ,$ D^{0}\to\rho(770)\rho(770) $ , and$ D^{0}\to2(\pi\pi)_{S} $ are observed in both channels. With the obtained amplitude model, the$ CP $ -even fractions of$ D^0\to \pi^+\pi^-\pi^+\pi^- $ and$ D^0\to\pi^+\pi^-\pi^0\pi^0 $ (non-η) are determined to be$ (75.2\; \pm\; 1.1_{\rm stat.}\; \pm\; 1.5_{\rm syst.})\ $ % and$(68.9\; \pm\; 1.5_{\rm stat.}\; \pm\; 2.4_{\rm syst.})$ %, respectively. The branching fractions of$ D^0\to \pi^+\pi^-\pi^+\pi^- $ and$ D^0\to\pi^+\pi^-\pi^0\pi^0 $ (non-η) are measured to be$(0.688\; \pm\; 0.010_{\rm stat.}\; \pm\; 0.010_{\rm syst.})$ % and$(0.951\; \pm\; 0.025_{\rm stat.}\; \pm\; 0.021_{\rm syst.})$ %, respectively. The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of$ D^0 \to 4\pi $ when used to determine the CKM angle$ \gamma (\phi_{3}) $ via the$ B^{-}\to D K^{-} $ decay. -
Masses of the conjectured H-dibaryon at different temperatures
2024, 48(8): 083105-083105-11. doi: 10.1088/1674-1137/ad3d4cShow AbstractWe present a lattice QCD determination of masses of the conjectured H-dibaryon, denoted as
$ m_H $ , at nine different temperatures:$ T/T_c = $ 0.24, 0.63, 0.76, 0.84, 0.95, 1.09, 1.27, 1.52, and 1.90. The masses of baryons N, Σ, Ξ, and Λ at different temperatures were also computed. The simulations were performed on an anisotropic lattice with$ N_f=2+1 $ flavours of clover fermion at a quark mass corresponding to$m_\pi=384(4)\; {{\rm{MeV}}}$ . The thermal ensembles were provided by the FASTSUM collaboration, whereas the zero temperature ensembles were provided by the Hadspec collaboration. We also calculated the spectral density of the correlation function of those particles. The spectral density distributions show a rich peak structure at the lowest temperature; at intermediate temperatures, the mass values of those particles obtained by the extrapolation method reflect a two-peak structure. While the spectral density for the octet baryon becomes smooth at$ T/T_c = $ 1.27, 1.52, and 1.90, the spectral density for the H-dibaryon becomes smooth at$ T/T_c = 1.90 $ . At$ T/T_c =0.24 $ , the mass difference of the H-dibaryon and Λ pair, expressed as$ \Delta m = m_H - 2\,m_{\Lambda} $ , was estimated to be$ \Delta m = -14.6(6.2) $ MeV, which suggests the existence of a bound H-dibaryon state.
Current Issued
2024 Vol. 48, No. 6
Published: 30 May 2024
Published: 30 May 2024
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Original research articles, Ietters and reviews Covering theory and experiments in the fieids of
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- Cosmology
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Cover Story
- Cover Story (Issue 4, 2024) | Advancing gravitational wave astronomy: AI-enhanced detection and real-time analysis in the presence of glitches
- Cover Story (Issue 3, 2024) | First measurement of the ground-state mass of 22Al helpsto evaluate the ab-initio theory
- Cover Story (Issue 2, 2024) | Quark/gluon taggers light the way to new physics
- Cover story (Issue 6, 2023) ｜Joint constraints on cosmological parameters using future multi-band gravitational wave standard siren observations
- Cover Story (Issue 5, 2023) | Production and decay of polarized hyperon-antihyperon pairs
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