In Major Breakthrough, Scientists Observe Higgs Boson Decay into Bottom Quarks

[phands]

Intriguing....

In a major physics milestone, scientists at CERN’s Large Hadron Collider (LHC) have observed the first evidence of a Higgs boson particle decaying into two matter-antimatter bottom quarks. This achievement, announced jointly on Tuesday by the ATLAS and CMS teams at LHC, has significant implications for future research into the most basic building blocks of matter in the universe.
If that all sounds like a bunch of particle wonk, fear not—even scientists in the field regard these quantum-scale interactions as mind-bogglers. So let’s back up and revisit what the Higgs boson is and why it’s any of our dang business how it decays.


The existence of this famous particle was proposed in the 1960s by a team of physicists including its namesake, Peter Higgs, to explain how some massless particles appeared to magically gain mass. The Higgs boson became an important lynchpin to the Standard Model of particle physics, which is our best attempt to explain how the forces of the universe work (minus gravity.) Proving that the particle did exist would validate the Standard Model, and demonstrating that it could not exist would mean rethinking our most basic assumptions.
As it turns out, the Higgs boson is a total flake that only hangs around for one septillionth of a second before decaying into smaller parts. Over the past half-century, scientists repeatedly tried and failed to capture the fallout of its flickering existence by crashing particles into each other at near light speed in a series of accelerators.
It wasn’t until the summer of 2012 that the LHC, the most powerful accelerator in the world, finally smashed some particles just right, and definitively identified the decay of a Higgs boson into smaller particles called Z bosons, W bosons, and photons. The particle was shown to exist and the Standard Model was validated—a discovery that earned Higgs and physicist François Englert the 2013 Nobel Prize in Physics.
So if the Higgs boson’s decay has already been observed, what’s special about the new announcement from the ATLAS and CMS teams? Once again, it has to do with the Higgs boson being a prickly customer that does not like to make anything easy for the people who study it.


The particle has long been theorized to decay along five signature pathways, of which four have already been observed at LHC. The fifth hypothetical pathway, in which the Higgs boson decays into subatomic particles called bottom quarks, is both the most difficult to trace and the most common, and is estimated to be the outcome of 60% of Higgs decay events.

Read more at:- https://motherboard.vice.com/en_us/...-observe-higgs-boson-decay-into-bottom-quarks

 

[steve_bank]

How would you detect a massless particle?

 

[Juma]

How would you detect a massless particle?

? That would depend on how it interacts. Photons are massless and are easily detected.
Neutrinos :

Various detection methods have been used. Super Kamiokande is a large volume of water surrounded by phototubes that watch for the Cherenkov radiation emitted when an incoming neutrino creates an electron or muon in the water. The Sudbury Neutrino Observatory is similar, but uses heavy water as the detecting medium. Other detectors have consisted of large volumes of chlorine or gallium which are periodically checked for excesses of argon or germanium, respectively, which are created by neutrinos interacting with the original substanc

 

[bigfield]

How would you detect a massless particle?

Photons are massless particles which are absorbed by electrons. We can see those using our eyes or by building photoconductive sensors.

Basically, massless particles interact with other types of particles that we know how to measure.

 

[repoman]

https://en.wikipedia.org/wiki/Higgs_boson#Decay

Found this article, when trying to see what even more energy than the LHC might find. Currently only rare cosmic rays have that much energy.

https://www.forbes.com/sites/startswithabang/2016/11/29/cosmic-rays-may-reveal-new-physics-just-out-of-lhcs-reach/#13c9f892669b

 

[steve_bank]

I thought photons have a mass. It has been demonstrated on a model space elevator that a laser can lift a thin light disk on a cable.

Particle physics is out of my depth. I once tried to get through a book but it was too complex to just pick up casually. I looked at some links on CERN detectors. It looks like a form of mass spectrometer.

https://lhcb-public.web.cern.ch/lhcb-public/en/detector/Detector-en.html

https://home.cern/about/experiments/lhcb

 

[bigfield]

I thought photons have a mass. It has been demonstrated on a model space elevator that a laser can lift a thin light disk on a cable.

If photons had mass they could not travel at c, because relativistic mass (which is a product of rest mass) approaches infinity as speed approaches c.

I did a quick search for space elevators lifted by lasers, and it seems that the laser is just shining a concentrated beam of light on photovoltaic cells on the elevator, which collect energy to be used by the elevator's conventional electric motors. Couldn't find a reference to an experiment where the laser beam itself did the pushing.

https://lhcb-public.web.cern.ch/lhcb-public/en/detector/Detector-en.html

https://home.cern/about/experiments/lhcb

The LHC collides protons. I think you've conflated photons and protons.

 

[steve_bank]

I thought photons have a mass. It has been demonstrated on a model space elevator that a laser can lift a thin light disk on a cable.

If photons had mass they could not travel at c, because relativistic mass (which is a product of rest mass) approaches infinity as speed approaches c.

I did a quick search for space elevators lifted by lasers, and it seems that the laser is just shining a concentrated beam of light on photovoltaic cells on the elevator, which collect energy to be used by the elevator's conventional electric motors. Couldn't find a reference to an experiment where the laser beam itself did the pushing.

https://lhcb-public.web.cern.ch/lhcb-public/en/detector/Detector-en.html

https://home.cern/about/experiments/lhcb

The LHC collides protons. I think you've conflated photons and protons.

OK. Got it wrong.

 

[steve_bank]

I thought photons have a mass. It has been demonstrated on a model space elevator that a laser can lift a thin light disk on a cable.

If photons had mass they could not travel at c, because relativistic mass (which is a product of rest mass) approaches infinity as speed approaches c.

I did a quick search for space elevators lifted by lasers, and it seems that the laser is just shining a concentrated beam of light on photovoltaic cells on the elevator, which collect energy to be used by the elevator's conventional electric motors. Couldn't find a reference to an experiment where the laser beam itself did the pushing.

https://lhcb-public.web.cern.ch/lhcb-public/en/detector/Detector-en.html

https://home.cern/about/experiments/lhcb

The LHC collides protons. I think you've conflated photons and protons.

Not confusing, poorly worded. It appears results of collisions are evaluated by mass spectroscopy.



Ok. It has relativistic momentum but no mass. I also found a link explaining away photons requiremening mass to interact with gravity via relativity.

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html

 

[lpetrich]

Long-sought decay of Higgs boson observed | CERN
In Major Breakthrough, Scientists Observe Higgs Boson Decay into Bottom Quarks - Motherboard
I'd posted on some earlier announcements in Checking the Higgs Particle's Mass-Making.

So we have checked the Higgs particle's couplings to the W, the Z, the top and bottom quarks, and the tau lepton. The next decay that they will be looking for is into muons. They will last long enough to travel through the detectors, meaning that one will not need to infer their production from their decay products, as one has to with most of the other Higgs-particle decay products. Including bottom quarks. However, muons will be produced at much less rate than the decay products observed so far, because (decay fraction) ~ (mass)^2. So the Higgs particle should decay into muons at about 1/1600 the rate that it decays into bottom quarks.

An upcoming upgrade to the Large Hadron Collider is High Luminosity, making it the HL-LHC. That will mean many more events to work with and sort through. So when that gets running, we may see Higgs -> muons decays with it.

 

[repoman]

This seems to be a good recent science literate, but layman overview about the LHC:

https://medium.com/starts-with-a-bang/five-years-after-the-higgs-what-else-has-the-lhc-found-95b3149751b1