ذرات رنگ -
بار به تنهایی یافت نمی شوند
بهمین
دلیل کوارکها درون هادرونها محبوس هستند. این اختلاط موجب
می شود رنگها خنثی شوند. کنش قوی باعث می شود که ترکیب
کوارکها بصورت باریون و مزون ظاهر شوند.
Color-charged particles
cannot be found individually. For this reason, the
color-charged quarks areconfined in
groups hadrons with other quarks.
These composites are
color neutral. Strong interactions reflected that quarks
combine only into baryons three quark objects, and
mesons quark-antiquark objects, but not, for example,
four-quarkobjects. Only baryons three different colors
and mesons color and anticolor are color-neutral. |
Color-Force Field
کوارکها در داخل هادرونها گلئون رد و بدل می
کنند. بهمین دلیل فیزیکدانان در مورد میدان رنگ - نیرو صحبت می
کنند که گلئونها، کوارکها را بطرف یکدیگر می رانند.
The quarks in a given hadron madly exchange
gluons. For this reason, physicists talk about the color-force
field which
consists of the gluons holding quarks together.
If one of the quarks in a given hadron is
pulled away from its neighbors, the color-force field
"stretches" between that quark and its neighbors. In so doing,
more and more energy is added to the color-force field as the
quarks are pulled apart. At some point, it is energetically
cheaper for the color-force field to "snap" into a new
quark-antiquark pair. In so doing, energy is conserved because
the energy of the color-force field is converted into the mass
of the new quarks, and the color-force field can "relax" back to
an unstretched state.
کوارکها نمی
توانند تنها باشند، زیرا نیروی رنگ افزایش می یابد و آنها
را از یکدیگر دور می کند
Quarks cannot exist individually because the
color force increases as they are pulled apart. |
هنگامیکه
کوارکی گلئون جذب می کند یا منتشر می کند، رنگ کوارک باید
تغییر کند تا ثبات رنگ محفوظ بماند.
When a quark emits or
absorbs a gluon, that quark's color must change in order
to conserve
color charge. For example, suppose a red quark
changes into a blue quark
and emits a red/antibluegluon
the antiblue manifests as yellow. The net color is still red. This
is
because - after the emission of the gluon the blue color
of the quark cancels with
the antiblue color of the gluon. The remaining color
then is the red color of the gluon.
Quarks emit and absorb
gluons very frequently within a hadron, so there is no
way to
observe the color of an individual quark. Within a
hadron, though, the color of the two quarks exchanging a
gluon will change in a way that keeps the bound system
in a color-neutral state. |
کنش قوی کوارکها را به یکدیگر متصل می کند
Residual Strong Force
So now we know that the strong force binds quarks together
because quarks have color charge. But that still does not
explain what holds the nucleus together, since positive protons
repel each other with electromagnetic force, and protons and
neutrons are color
neutral.
چه چیزی
هسته را به متحد نگاه می دارد؟
نیروهای قوی
که کوارکها به یکدیگر وارد می کنند، موجب پایداری هسته است
همچنانکه در
شکل بالا نشان داده شده است، یک کوارک از یک پروتون به
کوارک دیگری از پروتون دوم نیرو وارد می کند و این نیرو از
نیروی دافعه الکتریکی قوی تر است
So what holds the nucleus
together?
They don't call it the strong force for nothing. The
strong force between the quarks in one proton and the
quarks in another proton is strong enough to overwhelm
the repulsive electromagnetic force. This is called the
residual strong interaction,
and it is what "glues" the nucleus together. |
Weak
شش نوع کوارک
و شش نوع لپتون وجود دارد. همه مواد موجود در جهان از اینها ساخته
شده اند.
There are six kinds of quarks and six
kinds of leptons. But all the stable matter of the universe
appears to be made of just the two least-massive quarks (up
quark and down quark), the least-massive charged lepton (the
electron), and the neutrinos.
نیروی هسته ای ضعیف
موجب می شود که کوارکهای سنگین به کوارکهای سبکتر واپاشیده شوند.
Weak interactions are responsible for the decay of massive
quarks and leptons into lighter quarks and leptons. When
fundamental particles decay, it is very strange: we observe the
particle vanishing and being replaced by two or more different
particles. Although the total of mass and energy is conserved,
some of the original particle's mass is converted into kinetic
energy, and the resulting particles always have less mass than
the original particle that decayed.
تمام مواد
موجود در اطاف ما از کوارکهای سبک و لپتونها تشکیل شده اند
که آنها واپاشیده نمی شوند. در مدل استاندارد کنش ضعیف و
کنش الکترومغناطیسی یکسان سازی شده اند که آن را الکتروویک
می نامند
The only matter around
us that is stable is made up of the smallest quarks and
leptons, which cannot decay any further. The Standard
Model has united electromagnetic interactions and weak
interactions into one unified interaction called
electroweak. |
Electroweak
Weak and the electromagnetic
interactions
have been combined into a unified electroweak theory.
Physicists had long believed that weak
forces were closely related to electromagnetic forces.
Eventually they discovered that at very short distances (about
10-18 meters)
the strength of the weak interaction is comparable to that of
the electromagnetic. On the other hand, at thirty times
that distance (3x10-17 m)
the strength of the weak interaction is 1/10,000th than that
of the electromagnetic interaction. At distances typical for
quarks in a proton or
neutron(10-15 m)
the force is even tinier.
In fact, the weak and electromagnetic
forces have essentially equal strengths. This is because the
strength of the interaction depends strongly on both the mass of
the force carrier and the distance of the interaction. The
difference between their observed strengths is due to the huge
difference
in mass between the W and Z particles, which are very massive,
and the photon,
which has no mass as far as we know.
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