分类: 物理学 >> 核物理学 提交时间: 2023-06-09 合作期刊: 《Nuclear Science and Techniques》
摘要: The penalized least squares (PLS) method with appropriate weights has proven to be a successful baseline estimation method for various spectral analyses. It can extract the baseline from the spectrum while retaining the signal peaks in the presence of random noise. The algorithm is implemented by iterating over the weights of the data points. In this study, we propose a new approach for assigning weights based on the Bayesian rule. The proposed method provides a self-consistent weighting formula and performs well, particularly for baselines with different curvature components. This method was applied to analyze Schottky spectra obtained in 86 Kr projectile fragmentation measurements in the experimental Cooler Storage Ring (CSRe) at Lanzhou. It provides an accurate and reliable storage lifetime with a smaller error bar than existing PLS methods. It is also a universal baseline-subtraction algorithm that can be used for spectrum-related experiments, such as precision nuclear mass and lifetime measurements in storage rings.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: With applications in cosmology, infrared astronomy and CMB survey, frequency-division multiplexing (FDM) proved to be a viable readout for transition-edge sensors (TES). We investigate the occurrence of out-of-band resonances (OBR) which could constrain the bandwidth of the FDM readout of TES bolometers. The study includes SPICE modeling of the entire setup including the cryogenic harness, LC filters, Superconducting Quantum Interference Device (SQUID) and room-temperature amplifier. Simulation results show that the long harness (for flight model) could cause multiple reflections that generate repetitive spikes in the spectrum. Peaks of the OBR are mainly due to the parasitic capacitances at the input of SQUID. Implementing a low-pass RC circuit (snubber) at the input of the SQUID dampened the OBR. As a result, the first peak only appears around 20 MHz which is a safe margin for the 1 MHz-3.8 MHz FDM in use in the prototype readout. Using a spectrum analyzer and broadband LNAs,we also measured the OBR for the prototype FDM readout in the lab up to 500 MHz. The measurement was conducted at temperatures of 50 mK and 4 K and for various biasing of the DC SQUID. It turns out that OBR are more intense at 50 mK and are caused by the harness impedance mismatch rather than the SQUID. Simulation codes and supporting materials are available at https://github.com/githubamin/LT-Spice-Simulation-of-FDM-readout.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: We demonstrate that the recently observed X,Y,Z states cannot be purely from kinematic effect. Especially the narrow near-threshold structures in elastic channels call for nearby poles of the S-matrix which are qualified as states. We propose a way to distinguish cusp effects from genuine states and demonstrate that (not all of) the recently observed X,Y,Z states cannot be purely from kinematic effects. Especially, we show that the narrow near-threshold structures in elastic channels call for nearby poles of the S-matrix, since the normal kinematic cusp effect cannot produce that narrow structures in the elastic channels in contrast to genuine S-matrix poles. In addition, it is also discussed how spectra can be used to distinguish different scenarios proposed for the structure of those poles, such as hadro-quarkonia, tetraquarks and hadronic molecules. The basic tool employed is heavy quark spin symmetry.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: We propose to study the pentaquark candidates of P+c(4380) and P+c(4450) in J/ψ photoproduction and look for further experimental evidence for their nature. Since the photoproduction process does not satisfy the so-called "anomalous triangle singularity" condition their presence in J/ψ photoproduction would conclude that they should be genuine states and provide further evidence for their existence.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: We find that several thresholds can contribute to the enhancements of the newly observed heavy pentaquark candidates P+c(4380) and P+c(4450) via the anomalous triangle singularity (ATS) transitions in the specific kinematics of Λb→J/ψK−p. Apart from the observed two peaks we find that another peaks around 4.5 GeV can also be produced by the ATS. We also show that the Σ(∗)c can be produced at leading order in Λb decay. This process is different from the triangle diagram and its threshold enhancement only appears as CUSP effects if there is no pole structure or the ATS involved. The threshold interaction associated with the presence of the ATS turns out to be a general phenomenon and plays a crucial role in the understanding of candidates for exotic states.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: In order to test different models proposed for some states discovered recently in the charmonium mass range that do not fit into the pattern predicted by the conventional quark model, we derive predictions for the spectrum within the hadro-charmonium picture, the tetraquark picture as well as the hadronic molecular approach. We exploit heavy quark spin symmetry for the hadro-charmonium and hadronic molecule scenarios. The patterns that emerge from the different models turn out to be quite distinct. For example, only within the hadro-charmonium picture a pseudoscalar state emerges that is lighter than the Y(4260). Possible discovery channels of these additional states are discussed.
分类: 生物学 >> 植物学 >> 植物生物化学、植物生物物理学 提交时间: 2016-05-04
摘要: In many aromatic plants including spearmint (Mentha spicata), the sites of secondary metabolite production are tiny specialized structures called peltate glandular trichomes (PGT). Having high commercial values, these secondary metabolites are exploited largely as flavours, fragrances and pharmaceuticals. But, knowledge about transcription factors (TFs) that regulate secondary metabolism in PGT remains elusive. Understanding the role of TFs in secondary metabolism pathway will aid in metabolic engineering for increased yield of secondary metabolites and also the development of new production techniques for valuable metabolites. Here, we isolated and functionally characterized a novel MsYABBY5 gene that is preferentially expressed in PGT of spearmint. We generated transgenic plants in which MsYABBY5 was either overexpressed or silenced using RNA interference (RNAi). Analysis of the transgenic lines showed that the reduced expression of MsYABBY5 led to increased levels of terpenes and that overexpression decreased terpene levels. Additionally, ectopic expression of MsYABBY5 in Ocimum basilicum and Nicotiana sylvestris decreased secondary metabolite production in them, suggesting that the encoded transcription factor is probably a repressor of secondary metabolism.