Fifth Dimension Found At LHC?（原声文稿）

Transcript of LHC对撞数据出现无法解释的异常：第五维度可能真的存在 （中文完整文稿）。

A team of physicists claim they have found evidence for extra dimensions in data from the Large Hadron Collider.

If they're right, this would be one of the biggest discoveries in physics in decades. Let's have a look.

The new paper comes from two physicists in France and is an analysis of data collected at CMS that's one of the detectors at CERN's Large Hadron Collider LHC for short.

The LHC collides protons at a center of mass energy of several teraelectron volts, which is still the world record.

If these protons slam into each other, they create new particles, and since the energy is so high, they might create particles that no one's ever seen before.

The CMS experiment is basically a gigantic collection of sensitive measurement devices built around an enormous magnet.

The researchers were particularly interested in collisions that produce what's called jets.

For particle physicists, a jet is a spray of particles that appears when an energetic quark or gluon emerges from a collision.

Quarks are the constituents of protons and neutrons and gluons are the particles that hold quarks together.

By measuring the energy and direction of these sprays, physicists can reconstruct the masses of heavier particles that might have produced them.

Fun fact, I know someone who sat at an airport working on slides about collisions and jets and nuclear physics and was asked to please step aside into a small room for some questions to a story, but back to the extra dimensions.

That the Large Hydrocollider might find evidence for additional dimensions of space was one of the most exciting prospects when I was a student.

Indeed, it's what I wrote my PhD thesis about.

You see, the relation is that if there are additional dimensions of space, they must be small.

They must be curled up to small radius. And then the wavelength of the particles must fit into the radius.

This would mean that every particle that enters the extra dimensions has higher harmonics, standing waves in the extra dimensions.

And the higher the harmonics, the higher the energy of the particles.

These physicists now say that the large Haddon Collider has seen heavy versions of gluons with masses of about 3 .6 and 8 .6 Tv.

These decay into heavier versions of quarks and these then decay into these jets.

They found evidence for this in data collected by CMS between 2016 and 2018 and that run CMS saw two particularly interesting events, each produced four jets with a very high combined mass.

You can see the suspicious events here in this figure, it's the two dots up here.

They say that depending on how you look at it, they stand out at 3 .6 to 4 sigma, so that falls short of the 5 sigma discovery threshold, but it's more than just a little odd.

They say that the data from CMS run 3 could cross the discovery threshold.

The analysis is quite interesting because it's not just any sort of extra dimension they find, they find evidence for what's specifically called the Randall -Sundrum scenario.

In this case, there's only one extra dimension and it has a cosmological constant.

In the Randall -Sundrum scenario, the masses of the particles are not equally spaced, and that fits the data best. But there are some problems with this analysis.

First, the CMS run -through data is already out and they haven't seen any further of these jets.

Second, the idea of heavy gluons decaying into heavy quarks is contradicted by other data.

The authors acknowledge this problem, but basically just say, well, then the extra dimension is somehow more complicated.

Third, the authors claimed last year to have seen evidence for a heavier versions of graviton that are hypothetical particles that could carry the gravitation of force.

That turned out to be a composite particle of a top and an anti -top quark.

So these guys clearly are not accounting very well for standard physics in the first place.

They say it's why I'm sorry, but I give this a 9 out of 10 on the bullshit meter.

I don't doubt that these events exist or that they are odd, but I do not for a second buy the extra dimension story.

What I think is going on here instead is that particle physicists are desperately searching for something, anything interesting in the data that could justify building a bigger collider. Why is it not a 10 out of 10? Because I might be wrong.

I mean, there was a time in my life when I didn't think all these six -dimensional stuff is bullshit.

My reasoning at the time was basically, well, we don't know why space has three dimensions, so then maybe it actually isn't three. Seems worth checking.

Today I look at this entirely differently.

A scientific hypothesis must be necessary in the first place.

You can't just invent maths and then forever claim that one day one might be able to test it.

It's obviously a strategy that can't work and that, as a matter of fact, does not work.

That said, I spend years studying extra dimensions that don't exist, but this, as it turns out, was excellent preparation for the academic job market.

In September, a dark web marketplace claimed to be selling scans of more than 150 million drivers licenses.

Oh yes, that's a thing.

According to the FBI, Americans lost nearly 21 billion dollars to cybercrime last year. Thanks for watching. See you tomorrow.