

SLAC results disagree with the Standard Model - Marge
http://arxiv.org/abs/1205.5442

======
starwed
To whomever changed the title to eliminate the phrase "new physics": that
wasn't in any way sensational or editorial. This is a common phrase within the
physics community. From the conclusions part of the paper:

>The results presented here disagree with the SM at the 3.4σ level. Together
with the measurements by the Belle Collaboration, and the sizable difference
between the measured and predicted branching fraction of B− → τ−ντ [35–39],
_this could be an indication of new physics processes_ affecting decays with a
τ lepton in the final state.

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tapertaper
3.4 sigmas aren't enough. Call when you get to 5.

[http://scienceblogs.com/startswithabang/2011/12/13/the-
large...](http://scienceblogs.com/startswithabang/2011/12/13/the-large-hadron-
collider-the/)

and...

<http://trap.it/47HCqt>

~~~
ced
3.4 sigmas is the _within_ -model uncertainty - that is, given the assumptions
about their instruments and methodologies, the result stands at 3.4 sigma, or
about 1/1000.

I think that the uncertainty _about_ the model and assumptions is already
larger than 1/1000, especially given the recent failed "faster-than-light
neutrinos" LHC experiment. So while 5 sigmas would be nice, I would assume
that the physicists over there are busy double-checking everything, and trying
to reproduce the result, rather than improve their "sigma-score".

Can any physicist confirm? I'm not all that familiar with how these things
work. Furthermore, if they perform once more the experiment and get the same
3-sigma result, wouldn't that compound into a >3-sigma total?

~~~
Marge
The faster-than-light neutrinos probably got explained by a loose cable,
sorry. :) [http://arstechnica.com/science/2012/02/faster-than-light-
neu...](http://arstechnica.com/science/2012/02/faster-than-light-neutrino-
result-apparently-a-mistake-due-to-loose-cable/)

As to the double-checking, the analysis behind this result used the whole data
set collected by the BaBar experiment at the Stanford Linear Accelerator
(SLAC). So that's years of data, and the experiment hasn't been running since
2008. The question of course is, can some other experiment produce the same
results. As this is B-physics I would guess LHCb, one of the 4 main
experiments at CERN's LHC, might be able to do this, but I really don't know
for sure.

If you can repeat the same experiment and get another 3 sigma deviation from
the Standard Model predictions then yes, you could combine the results to get
a >3 sigma total (though they don't simply just add up to 6).

~~~
ced
_The faster-than-light neutrinos probably got explained by a loose cable,
sorry. :)_

Right:) That's exactly what I was referring to: the uncertainty about the
model/experimental setup is larger than the N-sigmas uncertainty reported by
the model and instruments.

~~~
DiabloD3
Except the scientists behind the loose cable up front said "we don't
understand these these results, we think they are false, please help us figure
out why". At no point were they published for legitimate consideration.

------
_dark_matter_
The idea of "New Physics" is sensational. There's only improvements to current
models, and maybe new models for new situations. The Standard Model has worked
out for too many situations for it to be just "wrong".

~~~
CJefferson
I would say that Relativity, and Quantum Mechanics, were 'new physics' over
the old Newtonian model, although for many, many, many problems, Newtonian
mechanics are still the best model. If this finally has found a major flaw in
the Standard Model, I consider that extremely exciting news.

~~~
sidww2
Relativity & Quantum Mechanics were massive paradigm shifts. In contrast, any
flaw in the Standard Model, while exciting, will likely be orders of magnitude
smaller in terms of impacting how we view the world.

Also we already know the Standard Model is not the complete picture (it cannot
integrate QM & General Relativity).

