Why the Z boson had a different mass at different times of day. | Hacker News Reader

Why the Z boson had a different mass at different times of day.

en.wikipedia.org

65 pointsjlangenauer22 comments

Theoretical science is certainly romantic --- but this sort of thing is what makes experimental science sexy. To be able to say "Ah! I am accidentally measuring the gravitation of the water in a nearby lake" --- and then compensate for it. Data so sharp you cut yourself.

The empirical data only tells you that your mass result is variable. It's your theorising that suggest as a hypothesis that the lake's current volume is perturbing your measurement - which you then show to be consistent with the rest of your theoretical framework by experiment.

I wonder if the bounds are such that someone walking along the corridor will affect the measurement ("yo momma so fat she perturbs the expected measured mass of the Z-boson!"). What's the relative gravitational attraction of, say, Jupiter versus a nearby train.

A great insight.

I'd love to be the guy who decided I bet that low frequency monthly term is the tides, let's just regress it out shall we?

Yeah, surely someone got a free beer out of that one.

I wonder, once you've convinced yourself the idea isn't crazy, how you go about convincing someone else --- No, look at the tidal chart, and then look at this variation here. See? And then one day you've hit critical mass and the whole lab is looking at train tables, the passage of the moon, and how often yo' momma brings you lunch, trying to find correspondences.

Or maybe there was already a list of possible confabulations, in decending order, and they checked them off one by one. That would be less amusing, I think.

Well, we are talking about the measurements of the Z boson being inaccurate (at really, really, really high levels of precision), not that the boson itself is somehow changing mass.

Sounds like a lot of fun to be had with super precise measurements in any case.

I think the mass actually changed. If you move, your mass increases w.r.t to an inertial frame. The closer you travel to the speed of light the more mass you get. I think mass also changes when the gravitational field changes. The device picked up those small changes .

http://en.wikipedia.org/wiki/Mass_in_special_relativity

According to the quote, the shape of the experiment was changing...

"So the bigger lake in the Spring was making the particle heavier." I am not sure which effect the quote describes: a slight change in the mass or a change in the instrument. Both are different. If it is the former I should be able to measure the change from light years away (since the lake wont affect me but will affect the particle).

It was not changing, the data was being corrupted. The link you gave describes relativistic (not invarient mass) in special relativity. You are correct that the relativistic (NOT invariant) mass can change depending on the inertial reference frame. However, the inclusion of changing gravitational fields and acceleration within gravitational fields is not the special theory of relativity, but the general theory of relativity.

While your idea of varying inertial reference frames is correct for invariant mass at a constant velocity (or experiencing no acceleration or distortion of spacetime due to a gravitational field), it is not correct when those are included.

In fact, it is easy to see that the relativistic mass must stay constant here for two reasons: 1) Relativistic mass can change between reference frames, but we are always doing the experiment in the same reference frame, and 2) Look at the equations. http://en.wikipedia.org/wiki/Lorentz_transformation#Lorentz_...

There are no gravitational terms in those equations, only spacetime derivatives (and various constants).

Edit: It's very late and I bet I'.m being unclear -- the velocity magnitude is probably changing slightly because of the outside fields. However, I doubt that relativistc mass change would be detectable by even their instruments. It's probably just variance in path.

I wonder why the weight of the boson is affected by all these factors. Anyone care to fill me in?

Z bosons decay into a lepton (electron, muon, or tau particle) and its anti-particle. Those decay products pass through a magnetic field and eventually collide with a material that absorbs all of their energy. Measuring the path of the leptons (in particular, the deflection caused by the magnetic field) allows you to determine their momentum. The intensity of the collision with the stopping material is used to determine the energy.

Knowing the energy and momentum allows one to calculate the path. Gravitational forces are also acting on those particles, and any changes in their paths caused will change the final calculated mass.

So it's just the gravitational forces acting on those Z bosons that affect the measurement of weight? If so, I'm just blown away. Physics never ceases to make my day better.

At least in my last physics class, weight was defined to be the gravitational force of the earth acting on an object. Perhaps you're blown away because you're equating weight and mass?

To be precise, weight is defined as the magnitude of the force one must apply to an object in a gravitational field in order to hold it at rest.

If you're on the moon, the gravitational force of the earth acting on an object is not what matters. It's the gravitational force of the moon that matters.

They're not measuring weight anyway -- they are measuring mass. Maybe I'll write up a blog post with a picture of how mass spectrometry works. It's a fairly common homework problem in intro EM courses anyway.

No, but because of how precise the experiment was. At first I didn't quite understand it, and now the full force of the article has hit me.

"final calculated [weight]" may be a better way to word it to avoid any confusion with the actual mass of the particle, as opposed to the calculation of how gravity at a given moment effects it.

The same thought occurred to me as well. However, I think the quote means that their _measurement_ of the mass was affected, not the real mass.

So it wasn't the ghost of Wolfgang Pauli flitting by after all?

That would pretty much drive me nuts.

I mean, you'd end up having to worry about the migratory patterns of birds and the pollen index while attempting to lock the actual value down.

Before any of that would be people walking by or int he area of the experiment, your own body and your changing (increasing?) weight.

For those interested, the train they were talking about was the French TGV high-speed train:

http://en.wikipedia.org/wiki/TGV

Reply on news.ycombinator.com