相关实验视频
Updated: May 24, 2025

10:42
Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
Published on: May 3, 2019
6.6K
使用Muonic τ衰变测量分支分数比率R(D^{+}) 和R(D^{*+}) 的测量
R Aaij1, A S W Abdelmotteleb2, C Abellan Beteta3
1Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands.
Physical review letters
|February 28, 2025
概括
研究人员测量了涉及陶子的B0衰变的分支分数比率,并将其与子的衰变进行比较. 结果与标准模型一致,有助于对粒子物理学的理解.
科学领域:
- 高能物理 高能物理
- 粒子物理学 粒子物理学
- 子光谱学 子光谱学
背景情况:
- 粒子物理学的标准模型 (SM) 预测了B介子衰变的特定比率.
- 与SM预测的偏差可能表明标准模型之外的新物理学.
- 之前对涉及陶子的B介质子衰变的测量表明了与SM预测的一些紧张关系.
研究的目的:
- 为了精确测量B0衰变的分支分数比率R(D+) 和R(D*+).
- 为了将这些比率与它们的体对应物进行比较.
- 测试标准模型在涉及重夸克和子的B质子衰变中的预测.
主要方法:
- 利用LHCb实验收集的2.0fb^-1的质子对质子碰撞13TeV的数据样本.
- 通过将D+介质与tau- -> mu- nu_tau候选体结合,重建了最终状态.
- 通过D+ -> K- pi+ pi+ 衰变通道重建了D+ 中子.
主要成果:
- 测量的R (D+) = 0.249 ± 0.043 (统计) ± 0.047 (系统).
- 测量的R ((D*+) = 0.402 ± 0.081 (国家统计) ± 0.085 (系统).
- 测量结果显示与标准模型预测的兼容性,相关系数为-0.39.
结论:
- 测量的分支分数比率与标准模型一致.
- 这项研究为B介质子衰变领域提供了精确的测量.
- 用更大的数据集进行进一步的研究可能会改进这些测量,并探测潜在的新物理.
相关概念视频
¹³C NMR: ¹H–¹³C Decoupling
993
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
993
Atomic Nuclei: Nuclear Spin State Population Distribution
911
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
911
Double Resonance Techniques: Overview
176
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...
176
¹H NMR: Complex Splitting
1.2K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
1.2K
High-Resolution Mass Spectrometry (HRMS)
1.2K
The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For...
1.2K
Radioactive Decay and Radiometric Dating
32.9K
Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
32.9K

