
Direct Coupling of the Higgs Boson to the Top Quark Observed - bellinom
http://www.media.uzh.ch/en/Press-Releases/2018/CMS-Experiment.html
======
politelemon
If my layperson's understanding is correct (probably vastly generalized), this
should be considered exciting news. A few years ago the existence of the Higgs
Boson was confirmed with some degree of confidence. These Higgs Bosons are
produced when particles interact with the Higgs Field giving them mass.

The next question from that was - is that really the Higgs Boson, does it
behave the way we expect it to (according to standard model)? I believe this
is a test to verify that it does and they measured the coupling constant and
it matched up. Neat. This could help with a much deeper understanding of why
particles have mass.

~~~
cshimmin
ATLAS physicist here -- you're mostly right! The existence of a Higgs boson
has been confirmed with extremely high confidence. And this news... it's
exciting in the sense that it's an important result, but it's a bit of a
damper on those of us who were hoping to discover new secrets about the
universe.

Interestingly, the primary production mechanism for the Higgs boson at the LHC
proceeds via the fusion of gluon particles from the colliding protons. This
seems strange at first glance, since the Higgs interacts with particles
proportionally to their mass, while the gluons are massless. In the standard
model, there is a higher-order process wherein the gluons annihilate into a
virtual "loop" of top quarks (which are very massive), which then "lend" their
mass to produce the Higgs.

Because previous measurements have been consistent with the Standard Model
prediction, we already had some evidence that the coupling to top quarks was
nominal. However, there are other possible scenarios involving exotic physics
that could mimic this production mechanism, which could imply the existence of
new forces/particles, and that the Higgs boson does not couple to "normal"
particles in the predicted fashion. Because of the nature of these heavy
virtual loop processes, it turns out that it's pretty hard to distinguish
between different such scenarios by examining the kinematic properties of the
events. Hence, the main observable is the rate, and even that can be made to
match a wide range of values with or without standard couplings, given a
clever enough theory.

This recent result demonstrates directly that the Higgs boson does indeed
couple to the top quark in a matter roughly consistent with the Standard Model
expectation (the CMS measurement shows an upward fluctuation, indicating even
stronger coupling than expected, although this is probably just a statistical
fluctuation). Therefore, no fancy/exotic physics (such as string theory,
strong gravity, etc) are required to explain the observed production of Higgs
bosons so far at the LHC.

~~~
dspillett
_> The existence of a Higgs boson has been confirmed with extremely high
confidence. And this news... it's exciting in the sense that it's an important
result, but it's a bit of a damper on those of us who were hoping to discover
new secrets about the universe._

There is a certain beauty in not only accepting that you might be wrong, but
actively _wanting_ to be wrong because that could be so much more interesting!

And a certain sadness in the disappointment some obviously have when they
accept that the less interesting outcome is the one that they receive.

~~~
cshimmin
Well, it's a bit selfish really. It's a terribly interesting outcome as it is,
but the particle physicists in the 70's and 80's got to have all the fun.

~~~
da_chicken
Sort of how the chemists in the 18th and 19th centuries got to have all the
fun.

"I'll call it 'Aluminum.' No, wait! ' _Aluminium_!' Uh... ship that first
print run of my book with the wrong spelling to North America. Nobody will
notice!"

"I'll call it Potassium, because it's found in potash." "That's not very
creative." "Fine, I'll call it Kalium and give it a symbol of K." "Where'd you
get Kalium from?" "Well, it's very alkaline, you see. It's from potash, after
all." "That's still not very creative!" "Fine. We'll call it Potassium, but
give it a symbol of K. Happy now?"

~~~
vidarh
It's still called Kalium in a bunch of languages.

~~~
staticautomatic
Is that also the case for "natrium?"

~~~
Confusion
Certainly:
[https://en.m.wiktionary.org/wiki/natrium](https://en.m.wiktionary.org/wiki/natrium)

And those are also mostly the countries using Kalium:
[https://en.m.wiktionary.org/wiki/kalium](https://en.m.wiktionary.org/wiki/kalium)

~~~
DrPhish
It misses Japanese, which uses German for a great many scientific and medical
loanwords:

[https://en.wiktionary.org/wiki/%E3%82%AB%E3%83%AA%E3%82%A6%E...](https://en.wiktionary.org/wiki/%E3%82%AB%E3%83%AA%E3%82%A6%E3%83%A0)

------
mullikine
The brightly colored CMS detector reminds me of the colorful spiralling
concentic circles of a mandlebrot zoom. We live in the matrix

~~~
martinpw
Yeah, they are spectacular. And then you look at the green parts on the side
and realize that thing is 4 stories high.

As an aside, I like the understated way the description is written:

 _The extraction of these events from the LHC data is challenging as there are
many mundane type of events that can mimic them. Identifying these events
requires measurements from all CMS subdetectors, which makes the
reconstruction quite complex._

I can only imagine what the value of "many" and the amount of effort behind
"challenging"and "quite complex" really is.

~~~
chaos95
Also the definition of "mundane" \- I'd guess there are several phenomena
under that heading that are quite fascinating in their own right.

~~~
c12
What I find incredible is the drive that these scientists have; then again
they get to work at what is in my opinion the most amazing scientific facility
humanity has built to date on Earth.

I'd choose looking over mundane data every day for that, regardless of how
boring it was, if only to be in the shadow of giants.

------
spullara
That's what we need, more confirmation of the standard model.

~~~
c12
To some, further confirmation of the standard model is a disappointment
because it doesn't tell us anything we didn't already know or point to some
exciting new physics.

~~~
Michael_Groom
Read this theory, it contains everything the standard model is incapable of
explaining, i.e. mass, distribution of normal matter/antimatter dark matter
and dark energy after the big bang, decrease of dark matter, increase of dark
energy, what DM and DE actually is, et cetera:

[http://norbert-winter.com/wp-
content/uploads/2018/02/2017-03...](http://norbert-winter.com/wp-
content/uploads/2018/02/2017-03-17_UC-AOS-en_norbert-winter_the-universe-
code_the-unified-composition-and-order-system-of-the-universe.pdf)

~~~
fabatka
Do you understand any of this? This notation is entirely unfamiliar to me, and
the text seems like gibberish (my favourite expression is "The most colossally
great global unification"). I'm also a bit skeptical about one person
answering so much big open questions all by himself, while there are a lot of
very bright scientists working on them without this much success.

~~~
perl4ever
The word "colossal" appears a surprisingly large number of times, as I just
posted elsewhere in this thread. And "rupture" is used even more. You would
think such important words would have some introduction, unless they are
standard terms of art.

~~~
Michael_Groom
Well “rupture” in this context simply describes the rupture of the massive
short ranged repulsive boson G5 leading to the rupture of the neutrino leading
to the reproduction cascade (see p153) leading to the proportions of normal
matter/antimatter and dark matter as measured by the planck telescope right
after the big bang.

~~~
perl4ever
Can you define "rupture" without using the word "rupture" or "simply" in the
explanation?

I find the excessive use of "colossal" and "rupture" to be very suggestive of
a Freudian slip implying the author is subconsciously aware that his
inspiration followed a massive cerebral hemorrhage.

~~~
Michael_Groom
Interesting assumption from skimming the pdf. Happy to hear your true thoughts
once you actually read and fully understand it.

~~~
perl4ever
It appears to be hermetic, so I don't see anything that can be studied
further.

I'm not sure why you are promoting it if you can't explain it yourself.

Here, for comparison, is what appears to me to be a normal scientific paper
that mentions spinors:

Supersymmetry, supergravity theories and the dual spinor model F Gliozzi, J
Scherk, D Olive - Nuclear Physics B, 1977

[http://cds.cern.ch/record/203097/files/CM-P00061869.pdf](http://cds.cern.ch/record/203097/files/CM-P00061869.pdf)

Note that it _does not_ end with "THE END" and it _does_ cite other scientific
works.

------
eric-hu
Is anyone aware of the "new techniques for data extraction" that this article
refers to?

~~~
thiagotomei
CMS physicist here! As our ATLAS colleagues, we also use boosted decision
trees extensively in our analysis, as well as the so-called Matrix Element
Method -- a way to combine the knowledge of the differential theoretical
cross-sections for the signal and background processes with our knowledge of
the experimental resolution of our detectors. More details are available in
[1].

However, in CMS we have recently started using Deep Neural Networks. These are
used for the separation of signal and background events in the "single-lepton
channel" of the search, i.e., the search where the Higgs boson decays to two
bottom quarks and the top quarks decay in such a way that at least one
electron or muon is present in the final state. Again, more details here: [2]

[1] [http://arxiv.org/abs/1803.05485](http://arxiv.org/abs/1803.05485)

[2] [http://cms-results.web.cern.ch/cms-results/public-
results/pr...](http://cms-results.web.cern.ch/cms-results/public-
results/preliminary-results/HIG-17-026/index.html)

