Related Experiment Video
Updated: Jun 2, 2026
07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
Measurement of the mass difference between t and t quarks
T Aaltonen1, B Álvarez González, S Amerio
1Division of High Energy Physics, Department of Physics, University of Helsinki and Helsinki Institute of Physics, FIN-00014, Helsinki, Finland.
Physical Review Letters
|May 17, 2011
Summary
Physicists measured the top quark mass difference using the CDF II detector. The study found a difference of -3.3 GeV/c², deviating from the expected zero mass difference in particle physics.
Area of Science:
- High Energy Physics
- Particle Physics
- Quantum Chromodynamics
Background:
- The Standard Model of particle physics predicts fundamental particles to be their own antiparticles.
- The CPT symmetry theorem is a cornerstone of quantum field theory, implying particles and antiparticles have identical masses.
Purpose of the Study:
- To directly measure the mass difference between the top quark and its antiparticle.
- To test the CPT symmetry in the context of top quark properties.
Main Methods:
- Analysis of top quark pair (tt) candidate events in the lepton+jets channel.
- Event-by-event mass difference estimation to create signal and background templates.
- Maximum likelihood fit comparing data distribution to templates.
Main Results:
- A measured mass difference ΔM(top) = M(t) - M(t) = -3.3 ± 1.4(stat) ± 1.0(syst) GeV/c².
- The result is approximately 2 standard deviations away from the CPT-conserving hypothesis of zero mass difference.
- Utilized 5.6 fb⁻¹ of integrated luminosity from the Tevatron pp Collider.
Conclusions:
- The direct measurement suggests a potential deviation from CPT symmetry for the top quark.
- Further investigation and higher precision measurements are warranted to confirm or refute this observation.
- This finding could have implications for our understanding of fundamental symmetries in particle physics.
Related Concept Videos
01:09Comparing Experimental Results: Student's t-Test
The t-test is a statistical method used to compare the sample mean with a population mean or compare two means from two data sets. The test statistic is calculated from the standard deviation, mean, and number of measurements in the data set at a selected confidence interval and then compared to a table of critical values at this confidence level. If the test statistic is smaller than the critical value, the null hypothesis is accepted. In this case, we state that the difference between the...
01:19Thomson's e/m Experiment
In a beam of charged particles created by a heated cathode, the particles move at different speeds. However, many applications need a beam with uniform particle speeds. An arrangement known as a velocity selector uses electric and magnetic fields to pick particles with a particular speed from the beam.
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...
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...
02:13Nuclear Binding Energy
The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect indicates a “loss” in mass of 4.0331 amu – 4.0026 amu = 0.0305 amu. The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms. The nuclear binding energy is the energy produced when the atoms’ nucleons are bound together;...
01:21Tandem Mass Spectrometry
Tandem mass spectrometry is a technique that uses multiple mass analyzers in series to obtain a higher selectivity and reduce chemical noise during analyte detection. Instruments with multiple analyzers separated by an interaction cell enable secondary fragmentation and selected study of the fragment ions.Secondary fragmentations occur in the interaction cell and can be induced by various factors. Fragmentation induced by collision with inert gases, such as N2, Ar, He, etc., is called...
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...