The meson is a

meson In particle physics, a meson ( or ) is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticle ...

composed of a

bottom antiquark The bottom quark or b quark, also known as the beauty quark, is a third-generation heavy quark with a charge of − ''e''. All quarks are described in a similar way by electroweak and quantum chromodynamics, but the bottom quark has excep ...

and a

strange quark The strange quark or s quark (from its symbol, s) is the third lightest of all quarks, a type of elementary particle. Strange quarks are found in subatomic particles called hadrons. Examples of hadrons containing strange quarks include kaons () ...

. Its

antiparticle In particle physics, every type of particle is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the positron (also known as an antie ...

is the meson, composed of a bottom quark and a strange antiquark.

B–B oscillations

Strange B mesons are noted for their ability to

oscillate Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

between

matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic par ...

and

antimatter In modern physics, antimatter is defined as matter composed of the antiparticles (or "partners") of the corresponding particles in "ordinary" matter. Antimatter occurs in natural processes like cosmic ray collisions and some types of radio ...

via a box-diagram with measured by CDF experiment at

Fermilab Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy United States Department of Energy National Labs, national laboratory specializing in high-energy parti ...

. That is, a meson composed of a bottom quark and strange antiquark, the strange meson, can spontaneously change into an bottom antiquark and strange quark pair, the strange meson, and vice versa. On 25 September 2006,

announced that they had claimed discovery of previously-only-theorized B_s meson oscillation. According to Fermilab's press release: Ronald Kotulak, writing for the

Chicago Tribune The ''Chicago Tribune'' is a daily newspaper based in Chicago, Illinois, United States, owned by Tribune Publishing. Founded in 1847, and formerly self-styled as the "World's Greatest Newspaper" (a slogan for which WGN radio and television a ...

, called the particle "bizarre" and stated that the meson "may open the door to a new era of physics" with its proven interactions with the "spooky realm of antimatter". Better understanding of the meson is one of the main objectives of the

LHCb The LHCb (Large Hadron Collider beauty) experiment is one of eight particle physics detector experiments collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the parame ...

experiment conducted at the

Large Hadron Collider The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundr ...

. On 24 April 2013, CERN physicists in the LHCb collaboration announced that they had observed

CP violation In particle physics, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry ( charge symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be t ...

in the decay of strange mesons for the first time. Scientists found the B_s meson decaying into two

muon A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As wi ...

s for the first time, with Large Hadron Collider experiments casting doubt on the scientific theory of

supersymmetry In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories e ...

. CERN physicist Tara Shears described the CP violation observations as "verification of the validity of the Standard Model of physics".

Rare decays

The rare decays of the B_s meson are an important test of the Standard Model. The branching fraction of the strange b-meson to a pair of muons is very precisely predicted with a value of Br(B_s→ µ⁺µ⁻)_SM = (3.66 ± 0.23) × 10⁻⁹. Any variation from this rate would indicate possible physics beyond the Standard Model, such as supersymmetry. The first definitive measurement was made from a combination of LHCb and CMS experiment data:

Br(B_s \rightarrow \mu^+\mu^-) = 2.8^_ \times 10^

This result is compatible with the Standard Model and set limits on possible extensions.

References

External links

* Mesons Strange quark B physics {{Particle-stub

B–B oscillations

Rare decays

See also

References

External links