1. Home
  2. College physics
  3. Particle physics
  4. Particles, patterns, and

33.4 Particles, patterns, and conservation laws  (Page 2/21)

<< Chapter < Page
  College physics     Page 2 / 21
Chapter >> Page >

Hadrons and leptons

Particles can also be revealingly grouped according to what forces they feel between them. All particles (even those that are massless) are affected by gravity, since gravity affects the space and time in which particles exist. All charged particles are affected by the electromagnetic force, as are neutral particles that have an internal distribution of charge (such as the neutron with its magnetic moment). Special names are given to particles that feel the strong and weak nuclear forces. Hadrons are particles that feel the strong nuclear force, whereas leptons    are particles that do not. The proton, neutron, and the pions are examples of hadrons. The electron, positron, muons, and neutrinos are examples of leptons, the name meaning low mass. Leptons feel the weak nuclear force. In fact, all particles feel the weak nuclear force. This means that hadrons are distinguished by being able to feel both the strong and weak nuclear forces.

[link] lists the characteristics of some of the most important subatomic particles, including the directly observed carrier particles for the electromagnetic and weak nuclear forces, all leptons, and some hadrons. Several hints related to an underlying substructure emerge from an examination of these particle characteristics. Note that the carrier particles are called gauge bosons . First mentioned in Patterns in Spectra Reveal More Quantization , a boson    is a particle with zero or an integer value of intrinsic spin (such as s = 0, 1, 2, ... size 12{s=0,`1,`2,` "." "." "." } {} ), whereas a fermion    is a particle with a half-integer value of intrinsic spin ( s = 1 / 2, 3 / 2, . . . size 12{s=1/2,`3/2,` "." "." "." } {} ). Fermions obey the Pauli exclusion principle whereas bosons do not. All the known and conjectured carrier particles are bosons.

The upper image shows an electron and positron colliding head-on. The lower image shows a starburst image from which two photons are emerging in opposite directions.
When a particle encounters its antiparticle, they annihilate, often producing pure energy in the form of photons. In this case, an electron and a positron convert all their mass into two identical energy rays, which move away in opposite directions to keep total momentum zero as it was before. Similar annihilations occur for other combinations of a particle with its antiparticle, sometimes producing more particles while obeying all conservation laws.
Selected particle characteristics The lower of the ∓ size 12{ -+ {}} {} or ± size 12{ +- {}} {} symbols are the values for antiparticles.
Category Particle name Symbol Antiparticle Rest mass ( MeV / c 2 ) B L e L μ L τ size 12{L rSub { size 8{τ} } } {} S size 12{S} {} Lifetime Lifetimes are traditionally given as t 1 / 2 / 0 . 693 (which is 1 / λ size 12{ {1} slash {λ} } {} , the inverse of the decay constant). (s)
Gauge Photon γ size 12{γ} {} Self 0 0 0 0 0 0 Stable
Bosons W size 12{W} {} W + size 12{W rSup { size 8{+{}} } } {} W − size 12{W rSup { size 8{ - {}} } } {} 80 . 39 × 10 3 size 12{"80" "." "22" times "10" rSup { size 8{3} } } {} 0 0 0 0 0 1.6 × 10 − 25 size 12{3 times "10" rSup { size 8{ - "25"} } } {}
Z size 12{Z} {} Z 0 size 12{Z rSup { size 8{0} } } {} Self 91 . 19 × 10 3 size 12{"91" "." "19" times "10" rSup { size 8{3} } } {} 0 0 0 0 0 1.32 × 10 − 25 size 12{3 times "10" rSup { size 8{ - "25"} } } {}
Leptons Electron e − size 12{e rSup { size 8{ - {}} } } {} e + size 12{e rSup { size 8{ - {}} } } {} 0.511 0 ± 1 size 12{ +- 1} {} 0 0 0 Stable
Neutrino (e) ν e size 12{e rSup { size 8{ - {}} } } {} v ¯ e size 12{ { bar {v}} rSub { size 8{e} } } {} 0 7 . 0 eV size 12{0` left (<7 "." 0`"eV" right )} {} Neutrino masses may be zero. Experimental upper limits are given in parentheses. 0 ± 1 size 12{ +- 1} {} 0 0 0 Stable
Muon μ − size 12{μ rSup { size 8{ - {}} } } {} μ + size 12{μ rSup { size 8{+{}} } } {} 105.7 0 0 ± 1 size 12{ +- 1} {} 0 0 2 . 20 × 10 − 6 size 12{2 "." "20" times "10" rSup { size 8{ - 6} } } {}
Neutrino ( μ size 12{μ} {} ) v μ size 12{v rSub { size 8{μ} } } {} v - μ size 12{v rSub { size 8{μ} } } {} 0 ( < 0.27 ) 0 0 ± 1 size 12{ +- 1} {} 0 0 Stable
Tau τ − size 12{τ rSup { size 8{ - {}} } } {} τ + size 12{τ rSup { size 8{+{}} } } {} 1777 0 0 0 ± 1 size 12{ +- 1} {} 0 2 . 91 × 10 − 13 size 12{2 "." "29" times "10" rSup { size 8{ - "13"} } } {}
Neutrino ( τ size 12{τ} {} ) v τ size 12{v rSub { size 8{τ} } } {} v - τ size 12{ { bar {v}} rSub { size 8{τ} } } {} 0 ( < 31 ) 0 0 0 ± 1 size 12{ +- 1} {} 0 Stable
Hadrons (selected)
  Mesons Pion π + size 12{π rSup { size 8{+{}} } } {} π − size 12{π rSup { size 8{ - {}} } } {} 139.6 0 0 0 0 0 2.60 × 10 −8
π 0 size 12{π rSup { size 8{0} } } {} Self 135.0 0 0 0 0 0 8.4 × 10 −17
Kaon K + size 12{K rSup { size 8{+{}} } } {} K − size 12{K rSup { size 8{ - {}} } } {} 493.7 0 0 0 0 ± 1 size 12{ +- 1} {} 1.24 × 10 −8
K 0 size 12{K rSup { size 8{0} } } {} K - 0 size 12{ { bar {K}} rSup { size 8{0} } } {} 497.6 0 0 0 0 ± 1 size 12{ +- 1} {} 0.90 × 10 −10
Eta η 0 size 12{η rSup { size 8{0} } } {} Self 547.9 0 0 0 0 0 2.53 × 10 −19
(many other mesons known)
  Baryons Proton p size 12{p} {} p - size 12{ { bar {p}}} {} 938.3 ± 1 0 0 0 0 Stable Experimental lower limit is >5 × 10 32 size 12{>5 times "10" rSup { size 8{"32"} } } {} for proposed mode of decay.
Neutron n size 12{n} {} n - size 12{ { bar {n}}} {} 939.6 ± 1 0 0 0 0 882
Lambda Λ 0 size 12{Λ rSup { size 8{0} } } {} Λ - 0 size 12{ { bar {Λ}} rSup { size 8{0} } } {} 1115.7 ± 1 0 0 0 ∓ 1 size 12{ -+ 1} {} 2.63 × 10 −10
Sigma Σ + size 12{Σ rSup { size 8{+{}} } } {} Σ - − size 12{ { bar {Σ}} rSup { size 8{ - {}} } } {} 1189.4 ± 1 0 0 0 ∓ 1 size 12{ -+ 1} {} 0.80 × 10 −10
Σ 0 size 12{Σ rSup { size 8{0} } } {} Σ - 0 size 12{ { bar {Σ}} rSup { size 8{0} } } {} 1192.6 ± 1 0 0 0 ∓ 1 size 12{ -+ 1} {} 7.4 × 10 −20
Σ − size 12{Σ rSup { size 8{ - {}} } } {} Σ - + size 12{ { bar {Σ}} rSup { size 8{+{}} } } {} 1197.4 ± 1 0 0 0 ∓ 1 size 12{ -+ 1} {} 1.48 × 10 −10
Xi Ξ 0 size 12{Ξ rSup { size 8{0} } } {} Ξ - 0 size 12{ { bar {Ξ}} rSup { size 8{0} } } {} 1314.9 ± 1 0 0 0 ∓ 2 size 12{ -+ 2} {} 2.90 × 10 −10
Ξ − size 12{Ξ rSup { size 8{ - {}} } } {} Ξ + size 12{Ξ rSup { size 8{+{}} } } {} 1321.7 ± 1 0 0 0 ∓ 2 size 12{ -+ 2} {} 1.64 × 10 −10
Omega Ω − size 12{ %OMEGA rSup { size 8{ - {}} } } {} Ω + size 12{ %OMEGA rSup { size 8{+{}} } } {} 1672.5 ± 1 0 0 0 ∓ 3 size 12{ -+ 3} {} 0.82 × 10 −10
(many other baryons known)

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
<< Chapter < Page Page > Chapter >>
Practice Key Terms 15

Read also:

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'College physics' conversation and receive update notifications?

Ask