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posted by CoolHand on Monday October 26 2015, @03:39PM   Printer-friendly
from the these-glueballs-ain't-for-sniffin dept.

http://arstechnica.com/science/2015/10/missing-glueballs-are-sticky-problem-for-particle-physics/

The discovery of the Higgs boson was rightfully heralded as a triumph of particle physics, one that brought completion to the Standard Model, the collection of theories that describes particles and their interactions. Lost in the excitement, however, was the fact that we're still missing a piece from the Standard Model—another type of particle that doesn't resemble any other we've yet seen.

The particle is a glueball, but its goofy name doesn't express how interesting it is. Glueballs are unique in that they don't contain any matter at all: they have no quarks or electrons or neutrinos. Instead, they are made entirely of gluons, which are the particles that bind quarks together inside protons, neutrons, and related objects.

Particle physicists are sure they exist, but everything else about them is complicated, to say the least. Like so many other exotic particles (including the Higgs), glueballs are very unstable, decaying quickly into other, less massive particles. We don't have any ideas about their masses, however, which is obviously kind of important to know if you want to find them. We also don't know exactly how they decay, making it hard to know exactly how we'll identify them in experiments.

If I may be so bold, what do fellow SNs think of modern particle physics, and do any of you have any crazy alternative non-particle-centric physical theories (for example, a model of reality that works using 7-dimensional strings as opposed to 1-dimensional strings from string theory?)


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  • (Score: 3, Informative) by AnonymousCowardNoMore on Monday October 26 2015, @06:36PM

    by AnonymousCowardNoMore (5416) on Monday October 26 2015, @06:36PM (#254817)

    You left out three important things: 1) It's a joke. 2) It's actually impossible. 3) Feynman retold the joke but got it from his advisor (Wheeler).

    I cannot resist telling you an amusing fable, but you must promise not to take it too seriously. Feynman claimed that his advisor...

    ...

    ...this does imply that the number of positrons in the universe should equal the number of electrons (give or take one), but apart from that it's kind of cute.

    --D. Griffiths, Introduction to Elementary Particles, 2nd ed. 2008. Wiley. Page 65-66.

    The problem with the number of antiparticles can't be solved by assuming they are far away, since our understanding of cosmology implies that sufficiently distant particles will never be able to reach us even at the speed of light. This is due to the rate of cosmic expansion. The idea would also imply that every particle (of the appropriate type, here electrons) must be stable, otherwise they would break the chain when decaying. If it applies to electrons, then you would be at pains to explain why the matter-antimatter distinction does not work that way for other (unstable) particles.

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  • (Score: 1, Interesting) by Anonymous Coward on Monday October 26 2015, @06:47PM

    by Anonymous Coward on Monday October 26 2015, @06:47PM (#254825)

    I am well outside my area of expertise and I just came across this idea the other day. However, I do not think it was considered a joke at the time:

    The space-time approach to quantum electrodynamics, as has been developed by Feynman,1) seems to offer a very attractive and useful idea to this domain of physics. His ingenious method is indeed attractive, not only because of its 'intuitive procedure which enables one to picture to oneself the complicated interactions of elementary particles, its ease and relativistic correctness with which one can calculate the necessary matrix elements or transition probabilities, but also because of its way of thinking which seems somewhat strange at first look and resists our minds that are accustomed to causal laws. According to the new standpoint, one looks upon the world in its four-dimensional entirety. A phenomenon that will come into play in this theatre is now laid out beforehand in full detail from immemorial past to ultimate future and one investigates the whole of it at glance. The time itself loses sense as the indicator of the development of phenomena; there are particles which flow down as well as up the stream of time; the- eventual creation and annihilation of pairs that may occur now and then, is no creation nor annihilation, but only a change of directions of moving particles, from past to future, or from future to past; a virtual pair, which, according to the ordinary view, is foredoomed to exist only for a limited interval of time, may also be regarded as a single particle that is circulating round a closed orbit in the four-dimensional theatre; a real particle is then a particle whose orbit is not closed but reaches to infinity ...

    Nambu, Yoichiro (1950). "The Use of the Proper Time in Quantum Electrodynamics I". Progress in Theoretical Physics 5 (5): 82.
    http://ptp.oxfordjournals.org/content/5/1/82.full.pdf+html [oxfordjournals.org]

    • (Score: 3, Informative) by AnonymousCowardNoMore on Monday October 26 2015, @06:59PM

      by AnonymousCowardNoMore (5416) on Monday October 26 2015, @06:59PM (#254832)

      The part about there being only one electron is the joke. The part about positrons being time-reversed electrons is not.

      • (Score: 0) by Anonymous Coward on Monday October 26 2015, @09:35PM

        by Anonymous Coward on Monday October 26 2015, @09:35PM (#254889)

        That second paper I quoted does not treat it as a joke.

        • (Score: 2) by AnonymousCowardNoMore on Tuesday October 27 2015, @04:06PM

          by AnonymousCowardNoMore (5416) on Tuesday October 27 2015, @04:06PM (#255154)

          You refer to the first page, I take it? Great question.

          It is possible to view an annihilating electron-positron pair as a single particle changing direction in time, since a positron is an electron with its time, parity (handedness) and charge reversed (CPT theorem). Similarly for pair production. We could also chain together as many of these events as we want, to create a large number of particle-antiparticle pairs which may be viewed as a "single" particle in 4D spacetime. The article mentions that and is correct, that it is an interesting (and instructive) way to view things.

          However, the joke does not relate to a given pair. The joke is that every electron and positron in the entire universe can be linked by such a chain, which would mean that all of them may be viewed as a single particle. It is not literally possible because it is violated for the reasons I gave above. It is also violated by every such chain disconnected from the others (for example, virtual pair production where the created electron-positron pair annihilate with each other, creating a closed loop) and by any process which creates or destroys an electron or positron without an identical antiparticle involved. (E.g. beta decay.) Therefore, it can not really be used to explain why all electrons appear identical.