CKM matrix isStandard Model of Particle PhysicsIt represents the coupling strength between top type quarks and bottom type quarks through the weak interaction of W particles.For the second generation quark case, it was first given by the Italian physicist Kabibo in 1963, and is usually called the Kabibo matrix or Kabibo angle.In 1973, Japanese physicists Shing Kobayashi and Minying Yoshikawa extended it to the third generation quarks.The third generation matrix contains phase, which can be used to explainWeak interactionCharge parity inSymmetry breaking(CP violation) is also often used to explain the asymmetry of cosmic baryon number.
Coupling strength of weak particle interaction.For the second generation quark case, it was first given by the Italian physicist Kabibo in 1963, and is usually called the Kabibo matrix or Kabibo angle.In 1973, Japanese physicists Shing Kobayashi and Minying Yoshikawa extended it to the third generation quarks.The third generation matrix contains phase, which can be used to explainWeak interactionCharge parity symmetry breaking in（
It is also often used to explain the asymmetry of the baryon number in the universe.
Fundamentals
Announce
edit
Measurement of CKM matrix elements
Most known
The matrix elements are determined by the semi leptonic decay method of hadrons.For example,
With the nucleus
For decay measurement, the specific transition with the smallest hadron effect is selected for experiment;
Is from
Measured by the decay of meson semileptonic channels.Although the uncertainty of hadron flow will affect
The accuracy of matrix element measurement can still be achieved by using strong interaction symmetry and reducing the influence of hadron current uncertainty
and
High precision measurement.Similarly, the strong action symmetry is accurately measured
It also played an important role.
with
Quark related
Matrix elements, such as
available
Meson semileptonic channel decay measurement, and
It is measured by the charm particle production in the neutrino nucleus scattering.
Measurement of meson semileptonic channel decay
The precision is limited by the uncertainty of shape factor.
Meson semileptonic channel decay is mainly used for researchCharm quarkAbsolute scale of decay amplitude and test of hadron flow mechanics.with
Quark related
Matrix element,
and
Must use
The decay of meson semileptonic channels is measured, and their absolute scale is theoretically assumed.
Representation of CKM matrix
In the standard model,
Like the fermion mass, the value of the matrix element does not belong to the basic parameter predicted by theory, but needs to be measured experimentally.Introducing the unitary condition with physical significance and abandoning the nonphysical quark phase factor, the theory concludes that:
The matrix contains only four independent parameters.These parameters can be selected in many forms, but there must be a phase factor
。Therefore,
A matrix must contain a complex element.
Use a set of angles
、
、
and
, represents
Matrix, in the form of:
among
，
wait.
That's what I mentioned earlier
horn
。factor
produce
Destruction effect, this factor disappears in the case of two generations of quarks.in consideration of
Very small and
Very close to 1, the above formula can be abbreviated as:
The values of matrix elements are arranged hierarchically according to their size
Near zero.In 1983, it was suggested that
Matrix by parameter
To expand,
Here, four independent parameters are taken as
、
、
and
。
Of the upper left corner of the matrix
The subarray is
and
quark
Rotation matrix.Experimental measurements show that this
The submatrix is an approximate unitary matrix.Deployable inner
Off diagonal elements of submatrix
and
be equal to
, and the diagonal element is equal to
The correction is reduced to maintain the approximate unitary of the subarray.
The measured value is about
, take
Magnitude, therefore writing
, where
Is approximately
Constant of.Experimental measurement
, or
, so take
。
The elements in the third column of the matrix are the same as
Quarks are related, and their representations must satisfy the conditions of unitary and orthogonality.This approximate parameterization method is easy to deal with in experimental research, so it is widely used.
CP damage
Third-generation quark
The matrix contains a phase factor.In the standard model, non-zero phase factors will result in
destruction.That is to say, the corresponding quark transition amplitude is not invariant under the joint transformation of positive and negative particle charges and space parity inversion.
Destruction is very important in understanding the hierarchical structure of particles and their interaction properties, and is also necessary in explaining the fact that the world is dominated by positive matter (rather than antimatter).People are looking out of the standard model with great interest
Sources of damage.
So far, only in
The weak effect of several thousandths is observed in the meson decay
Destruction.Although the observation results are consistent with the expectation of the standard model, the experiment cannot confirm that:
The matrix is where this decay occurs
One of the possible explanations for destruction.In fact, some theories beyond the standard model can also explain the existing decay data.
The value is very small, but the measured value is not zero, about
。It is very important that the matrix element is not zero, otherwise the standard model will not exist
destruction.In addition, the standard model expects:
Meson decay has larger
Disrupt asymmetry.seek
Meson decay
Destructive experiments have begun in some countries.[1]
