In
particle physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
, B mesons are
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 subparticles, ...
s composed of a
bottom
Bottom may refer to:
Anatomy and sex
* Bottom (BDSM), the partner in a BDSM who takes the passive, receiving, or obedient role, to that of the top or dominant
* Bottom (sex), a term used by gay couples and BDSM
* Buttocks or bottom, part of th ...
antiquark and either an
up (),
down (),
strange () or
charm quark (). The combination of a bottom antiquark and a
top quark
The top quark, sometimes also referred to as the truth quark, (symbol: t) is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs Boson. This coupling y_ is very close to unity; in the Standard ...
is not thought to be possible because of the top quark's short lifetime. The combination of a bottom antiquark and a bottom quark is not a B meson, but rather ''
bottomonium
In particle physics, quarkonium (from quark and -onium, pl. quarkonia) is a flavorless meson whose constituents are a heavy quark and its own antiquark, making it both a neutral particle and its own antiparticle.
Light quarks
Light quarks ( up ...
'', which is something else entirely.
Each B meson has an
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 ...
that is composed of a bottom quark and an
up (),
down (),
strange () or
charm () antiquark respectively.
List of B mesons
– oscillations
The neutral B mesons, and , spontaneously transform into their own antiparticles and back. This phenomenon is called
flavor oscillation. The existence of neutral B meson oscillations is a fundamental prediction of the
Standard Model of
particle physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
. It has been measured in the – system to be about , and in the – system to be 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 national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been opera ...
. A first estimation of the lower and upper limit of the – system value have been made by the
DØ experiment
The DØ experiment (sometimes written D0 experiment, or DZero experiment) was a worldwide collaboration of scientists conducting research on the fundamental nature of matter. DØ was one of two major experiments (the other was the CDF experim ...
also at
Fermilab
Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been opera ...
.
On 25 September 2006,
Fermilab
Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been opera ...
announced that they had claimed discovery of previously-only-theorized B
s meson oscillation. According to Fermilab's press release:
This first major discovery of Run 2 continues the tradition of particle physics discoveries at Fermilab, where the bottom (1977) and top (1995) quarks were discovered. Surprisingly, the bizarre behavior of the B (pronounced "B sub s") mesons is actually predicted by the Standard Model of fundamental particles and forces. The discovery of this oscillatory behavior is thus another reinforcement of the Standard Model's durability ...
CDF physicists have previously measured the rate of the matter-antimatter transitions for the B meson, which consists of the heavy bottom quark bound by the strong nuclear interaction to a strange antiquark. Now they have achieved the standard for a discovery in the field of particle physics, where the probability for a false observation must be proven to be less than about 5 in 10 million (). For CDF's result the probability is even smaller, at 8 in 100 million
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".
On 14 May 2010, physicists at the Fermi National Accelerator Laboratory reported that the oscillations decayed into matter 1% more often than into antimatter, which may help explain the abundance of matter over antimatter in the observed Universe. However, more recent results at
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 paramet ...
with larger data samples have suggested no significant deviation from the Standard Model.
Rare decays
B mesons are an important probe for exploring
quantum chromodynamics. Various uncommon decay paths of the B mesons are sensitive to physics processes
outside the standard model. Measuring these rare branching fractions sets limits on new particles. The LHCb experiment has observed and searched for several of these decays such as
On 21 February 2017, the LHCb collaboration announced that the rare decay of a neutral B meson into two oppositely charged
kaons
KAON (Karlsruhe ontology) is an ontology infrastructure developed by the University of Karlsruhe and the Research Center for Information Technologies in Karlsruhe.
Its first incarnation was developed in 2002 and supported an enhanced version of ...
had been observed to a statistical significance of 5.
See also
*
B– oscillation
References
External links
W.-M. Yao ''et al.'' (Particle Data Group), J. Phys. G 33, 1 (2006) and 2007 partial update for edition 2008 (URL: http://pdg.lbl.gov)*
*
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Mesons
B physics