Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.physics > #519371

LHC spots a consistent oddity in decays with leptons

Show all headers | View raw

LHC spots a consistent oddity in decays with leptons
> http://arstechnica.com/science/2015/09/lhc-spots-a-consistent-oddity-in-decays-with-leptons/

> The intriguing results come courtesy of the LHCb detector. Rather
> than search for new particles, LHCb tracks the decay of particles
> that contain a b quark (b stands for bottom or beauty, depending on
> who you talk to). These particles are well understood, so deviations
> from their expected behavior are relatively easy to spot. And those
> deviations could point to physics we haven't seen before, possibly
> including problems with the Standard Model of particles and their
> interactions.
>
> In this case, the detector was tracking neutral B mesons as they
> decayed into D mesons. (This happens as the bottom quark in the B
> meson decays into a charm quark. The second quark in the mesons, a
> down quark, sits all this out and just pairs with whatever's around.)
> This decay results in the production of a neutrino (which we can
> ignore) and a lepton, which is what we're paying attention to here.
>
> Leptons are a group of particles that include the familiar electron
> and its two heavier, more exotic cousins, the muon and the tau
> (sometimes called the "tauon" for pedantry's sake). From the
> perspective of the Standard Model, any lepton will do. The decays
> should produce the three leptons in proportion to their relative
> masses (a tau is about twice the mass of a proton, the muon weighs
> substantially less, and the electron is a lightweight).
>
> In this case, the LHCb collaboration tracked decays that produced
> either muons or taus, and then measured their relative frequency. And
> the results were close to the expected value, but not quite. Instead,
> taus were produced slightly more often than expected, a difference
> that was 2.1 standard deviations off from the Standard Model
> expectation.
>
> Now, in particle physics, 2.1 standard deviations is the sort of
> result that frequently goes away as more data is gathered—it takes
> three standard deviations to get physicists excited, and five before
> they start saying they've found something. Which is why, based on the
> abstract of the paper, there's nothing to get excited about here.
>
> But deep in the discussion, there's an intriguing indication that
> something unusual might be going on here: "The measured value is in
> good agreement with previous measurements at BaBar and Belle." These
> other two detectors studied B mesons produced by electron/positron
> collisions. So that means three different detectors, using different
> types of particle collisions, have seen a similar (if similarly weak)
> excess.


-- 

sci.physics is an unmoderated newsgroup dedicated
to the discussion of physics, news from the physics
community, and physics-related social issues.

Back to sci.physics | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

LHC spots a consistent oddity in decays with leptons Sam Wormley <swormley1@gmail.com> - 2015-09-06 16:17 -0500
  Re: LHC spots a consistent oddity in decays with leptons jimp@specsol.spam.sux.com - 2015-09-06 21:48 +0000
    Re: LHC spots a consistent oddity in decays with leptons Sam Wormley <swormley1@gmail.com> - 2015-09-06 17:12 -0500
      Re: LHC spots a consistent oddity in decays with leptons jimp@specsol.spam.sux.com - 2015-09-06 22:34 +0000

csiph-web