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Why are strange quarks strange?

  1. Jun 26, 2015 #1
    I know that all the quark names have a meaning and that the strange quark was named "strange quark" because it had strange properties.What are those strange properties the strange quark possess?
     
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  3. Jun 26, 2015 #2

    Orodruin

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    They were strange to physicists of the time when hadrons containing them were discovered. This was mainly due to such hadrons not conforming to the isospin framework in the same way as earlier hadrons had. Such hadrons were strange and associated with a quantum number called "strangeness". Quarks were discovered later if I do not misremember, and strangeness turned out to be the number of strange quarks in the hadron (so named because of this).
     
  4. Jun 26, 2015 #3

    jtbell

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    IIRC, the first-discovered strange particles (what we know now as the K and Λ) have much longer lifetimes than they "should" have had.
     
  5. Jun 26, 2015 #4

    Orodruin

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    Right, thanks for the reminder.
    Naturally, this is now attributed to weak interactions being the only interaction which breaks quark flavour.
     
  6. Jun 26, 2015 #5
    Thanks for clearing up for me because a website I used for a long time said that they where named strange quarks because they where smaller the higher generation quarks(up quark) but they where more massive which is true for all the other 3 quarks and if there where more quarks they would be even smaller than a top quark but more massive than all 6 quarks combined. So if that answer for why the strange quark are called strange then all the other quarks would also be called strange quarks and those third generation quarks would be even stranger due to their unfathomable size and there unfathomable mass for a particle. Particularly the top with a size of 1 x 10e-22 meters vs. an up quark with 1 x 10e-18 meters and 173 GeV with more than 100,000 times the mass of a up quark so it would be much stranger than a strange quark with only 50 times the mass of a up quark and a size of 4 x 10e-18.
     
  7. Jun 27, 2015 #6

    jtbell

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    The concept of "strangeness" came before the idea of the strange quark. In the early 1950s some newly-discovered particles had longer lifetimes than expected, so they were called "strange" and a new quantum number, "strangeness", was invented for them. The strong and electromagnetic interactions conserve strangeness, but the weak interaction doesn't.

    In the 1960s the idea of quarks came along. Originally there were only three of them: up, down and strange. All the "strange" particles have a strange quark in them, and a strange quark can convert to a down quark only via the weak interaction, which explains the long lifetime of "strange" particles.

    The charm and bottom (originally "beauty") quarks came along later, in the 1970s, to explain more newly-created particles that have properties that don't fit into the old up-down-strange scheme.

    Finally, based on the pattern formed by the up, down, strange, charm and bottom quarks, it was widely assumed that a "top" quark also had to exist, but particles containing top quarks weren't actually observed until the 1990s.

    In the meantime some physicists speculated that maybe top quarks weren't really necessary after all. I remember seeing in the early 1980s, towards the end of my graduate-school period, preprints about "topless bottom models" which sounded a bit, um, risqué. :wideeyed:
     
    Last edited: Jun 27, 2015
  8. Jun 27, 2015 #7
    How long did those strange particles last?
     
  9. Jun 27, 2015 #8

    Orodruin

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    Just a wordog warning: Quarks (as well as other elementary particles) do not have an intrinsic size. Be very suspicious of any source which claims otherwise.

    You can check the lifetimes of all these particles at http://pdg.lbl.gov/
     
  10. Jun 27, 2015 #9

    mfb

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    That does not make sense at all.

    By the way: due to a historic accident (see above), strange-quarks have a strangeness of minus one, and anti-strange-quarks have a strangeness of plus one.
     
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