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

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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

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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