Related Experiment Video
Updated: Jul 3, 2026
07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
Measurement of the lifetime difference between Bs mass eigenstates
D Acosta1, J Adelman, T Affolder
1University of Florida, Gainesville, Florida 32611, USA.
Physical Review Letters
|March 24, 2005
Summary
Researchers measured lifetimes and polarization amplitudes for B(0)(s) and B(0)(d) decays. For the first time, they determined the distinct lifetimes of the B(0)(s) system
Area of Science:
- Particle Physics
- High Energy Physics
- Quantum Mechanics
Background:
- Understanding B meson decays is crucial for testing the Standard Model of particle physics.
- CP violation in the B(0)(s) system provides insights into matter-antimatter asymmetry.
- Previous studies lacked precise measurements of the lifetimes of the heavy and light mass eigenstates.
Purpose of the Study:
- To measure the lifetimes and polarization amplitudes for B(0)(s)-->J/psiphi and B(0)(d)-->J/psiK(*0) decays.
- To separately measure the lifetimes of the heavy and light mass eigenstates in the B(0)(s) system for the first time.
- To determine the relative contributions of amplitudes with definite CP as a function of decay time.
Main Methods:
- Analysis of B(0)(s)-->J/psiphi and B(0)(d)-->J/psiK(*0) decay data.
- Measurement of lifetimes using the time-dependent decay rates.
- Determination of CP properties through polarization amplitude analysis.
Main Results:
- Measured lifetimes for B(0)(s) eigenstates: tau(L) = (1.05(+0.16)(-0.13) +/- 0.02) ps and tau(H) = (2.07(+0.58)(-0.46) +/- 0.03) ps.
- Calculated the difference in decay rates: DeltaGamma(s)/Gamma(s) = (65(+25)(-33) +/- 1)%.
- Determined the average decay rate difference: DeltaGamma(s) = (0.47(+0.19)(-0.24) +/- 0.01) ps(-1).
Conclusions:
- The study provides the first separate measurements of B(0)(s) heavy and light eigenstate lifetimes.
- The results offer new precision for understanding CP violation and decay dynamics in the B(0)(s) system.
- These measurements contribute to stringent tests of the Standard Model in flavor physics.
Related Concept Videos
01:52Atomic Mass
Atoms — and the protons, neutrons, and electrons that compose them — are extremely small. For example, a carbon atom weighs less than 2 × 10−23 g. When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the atomic mass unit (amu). The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are...
01:15High-Resolution Mass Spectrometry (HRMS)
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 example, the mass of helium...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
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.
01:08Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
01:13Mass Spectrometry: Isotope Effect
Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the mass differences between isotopes. Furthermore, the intensity of these signals is dependent on the...
01:13Mass Analyzers: Overview
The mass analyzer is a crucial component of the mass spectrometer. In the ionization chamber, the vaporized sample is bombarded with a high-energy electron beam to generate a radical cation and further fragment into neutral molecules, radicals, and cations. A series of negatively charged accelerator plates accelerate the cations into the mass analyzer. The mass analyzer separates ions according to their mass-to-charge (m/z) ratios and then directs them to the detector. The common types of mass...