D meson
Encyclopedia
The D mesons are the lightest particle containing charm quark
s. They are often studied to gain knowledge on the weak interaction
. The strange D mesons (Ds) were called the "F mesons" prior to 1986.
detector at the Stanford Linear Accelerator Center
.
Since the D mesons are the lightest mesons containing a single charm quark
(or antiquark), they must change the charm (anti)quark into an (anti)quark or another type to decay. Such transitions violate the internal charm quantum number, and can take place only via the weak interaction
. In D mesons, the charm quark preferentially changes into a strange quark via an exchange of a W particle
, therefore the D meson preferentially decays into s and s.
In November 2011, researchers at the LHCb
experiment at CERN
reported (3.5 sigma significance) that they have observed a direct CP violation
in the neutral D meson decay, possibly beyond the Standard Model
.
[a] PDG reports the resonance width (Γ). Here the conversion τ = is given instead.
Charm quark
The charm quark or c quark is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks...
s. They are often studied to gain knowledge on the weak interaction
Weak interaction
Weak interaction , is one of the four fundamental forces of nature, alongside the strong nuclear force, electromagnetism, and gravity. It is responsible for the radioactive decay of subatomic particles and initiates the process known as hydrogen fusion in stars...
. The strange D mesons (Ds) were called the "F mesons" prior to 1986.
Overview
The D mesons were discovered in 1976 by the Mark IMark I (detector)
The Mark I, also known as the SLAC-LBL Magnetic Detector, was a particle detector that operated at the interaction point of the SPEAR collider from 1973 to 1977. It was the first 4π detector, i.e...
detector at the Stanford Linear Accelerator Center
Stanford Linear Accelerator Center
The SLAC National Accelerator Laboratory, originally named Stanford Linear Accelerator Center, is a United States Department of Energy National Laboratory operated by Stanford University under the programmatic direction of the U.S...
.
Since the D mesons are the lightest mesons containing a single charm quark
Charm quark
The charm quark or c quark is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks...
(or antiquark), they must change the charm (anti)quark into an (anti)quark or another type to decay. Such transitions violate the internal charm quantum number, and can take place only via the weak interaction
Weak interaction
Weak interaction , is one of the four fundamental forces of nature, alongside the strong nuclear force, electromagnetism, and gravity. It is responsible for the radioactive decay of subatomic particles and initiates the process known as hydrogen fusion in stars...
. In D mesons, the charm quark preferentially changes into a strange quark via an exchange of a W particle
W and Z bosons
The W and Z bosons are the elementary particles that mediate the weak interaction; their symbols are , and . The W bosons have a positive and negative electric charge of 1 elementary charge respectively and are each other's antiparticle. The Z boson is electrically neutral and its own...
, therefore the D meson preferentially decays into s and s.
In November 2011, researchers at the LHCb
LHCb
LHCb is one of six particle physics detector experiments collecting data at the Large Hadron Collider accelerator at CERN. LHCb is a specialized b-physics experiment, that is measuring the parameters of CP violation in the interactions of b-hadrons...
experiment at CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
reported (3.5 sigma significance) that they have observed a direct CP violation
CP violation
In particle physics, CP violation is a violation of the postulated CP-symmetry: the combination of C-symmetry and P-symmetry . CP-symmetry states that the laws of physics should be the same if a particle were interchanged with its antiparticle , and left and right were swapped...
in the neutral D meson decay, possibly beyond the Standard Model
Standard Model
The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...
.
List of D mesons
| Particle name | Particle symbol |
Antiparticle symbol |
Quark content |
Rest mass (MeV/c Speed of light The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time... 2) |
I Isospin In physics, and specifically, particle physics, isospin is a quantum number related to the strong interaction. This term was derived from isotopic spin, but the term is confusing as two isotopes of a nucleus have different numbers of nucleons; in contrast, rotations of isospin maintain the number... G |
JP Parity (physics) In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:... C C parity In physics, C parity or charge parity is a multiplicative quantum number of some particles that describes its behavior under a symmetry operation of charge conjugation .... |
S Strangeness In particle physics, strangeness S is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic reactions, which occur in a short period of time... |
C | B' Bottomness In physics, bottomness also called beauty, is a flavour quantum number reflecting the difference between the number of bottom antiquarks and the number of bottom quarks that are present in a particle: B^\prime = -Bottom quarks have a bottomness of −1 while bottom antiquarks have a... |
Mean lifetime (s Second The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock.... ) |
Commonly decays to (>5% of decays) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| D meson | 1,869.62 ± 0.20 | 0− | 0 | +1 | 0 | See decay modes | |||||
| D meson | 1,864.84 ± 0.17 | 0− | 0 | +1 | 0 | See decay modes | |||||
| Strange D meson | 0 | 0− | +1 | +1 | 0 | See decay modes | |||||
| D meson | (2010) | (2010) | 2,010.27.62 ± 0.17 | 1− | 0 | +1 | 0 | |
|||
| D meson | (2007) | (2007) | 2,006.97 ± 0.19 | 1− | 0 | +1 | 0 | |
|||
[a] PDG reports the resonance width (Γ). Here the conversion τ = is given instead.
See also
- List of mesons
- List of baryons
- List of particles
- Timeline of particle discoveriesTimeline of particle discoveriesThis is a timeline of subatomic particle discoveries, including all particles thus far discovered which appear to be elementary given the best available evidence...