2.4- QUARKS AND ANTIQUARKS Flashcards
What were kaons called when they were first discovered?
called V particles
Why were kaons called V particles when they were first discovered?
cloud chamber photographs often showed V-shaped tracks
What did investigation show about V particles?
showed that the V tracks decay into pions only, or into pions and protons
What kind of particles were V particles called after the investigation that the V tracks decay into pions only, or into pions and protons?
strange particles
What do all strange particles decay through?
weak interaction
What strange particles were referred to as kaons?
those that decay into pions
Although strange particles all decay through the weak interaction what were sigma particles found to .. ? (2)
have different rest masses which were always greater than the proton’s rest mass
decay either in sequence or directly into protons and pions
In what numbers are strange particles created?
strange particles created in twos
Is strangeness always conserved in strong interactions?
yes
Is strangeness always conserved in weak interactions?
no- strangeness can change by 0, +1, or -1 in weak interactions
Examples of properties of hadrons? (3)
charge
strangeness
rest mass
How can the properties of hadrons be explained?
by assuming they’re composed of smaller particles known as quarks and antiquarks
What are the 3 types of quarks and antiquarks I need to know for hadrons?
up, down and strange
How are up, down and strange quarks denoted?
u, d, s
Are mesons hadrons?
yes
What do mesons consist of?
a quark and an antiquark
What combination is a π^0 meson?
– or –
uu dd
Why’re combinations that include - not called pions?
ss
they decay much faster than pions
How many uncharged kaons are there?
two
What are the uncharged kaons?
K^0 meson and -^0 meson
K
What is the antiparticle of any meson?
quark-antiquark pair
What is the antiparticles of a meson as it’s made up of a quark-antiquark pair?
meson
What are baryons and antibaryons?
hadrons that consist of three quarks for a baryon or three antiquarks for an antibaryon
What is the quark combination for a proton?
uud
What is the quark combination for a neutron?
udd
What is the quark combination for an antiproton?
uud
What is the Σ particle?
baryon containing a strange quark
What is the only stable baryon?
proton
What does a free neutron decay into?
proton
What does a free neutron release when it decays a proton?
releases an electron and an electron antineutrino, as in β− decay
What happens in β− decay?
neutron in a neutron-rich nucleus change into a proton, releasing an electron + electron antineutrino
In quark terms what happens in β− decay?
down quark changes to an up quark
What happens in β+ decay?
proton in proton-rich nucleus changes into a neutron, releasing a positron + electron neutrino
In quark terms what happens β+ decay?
up quark changes to a down quark
