Interested in the LHC safety assessment - questions about strangelets

[Athena319]

TL;DR

Is it possible that a strange dibaryon produced in the LHC could turn an ordinary nucleus into a dangerous strangelet?

I became interested in the discussions about potential catastrophic risk from colliders and I have some questions about it.

I am particularly interested in the strange matter scenario, and there is one thing I don't understand. I understand that the LSAG report shows that it is essentially impossible to create a strangelet in a particle accelerator. However, there are particles containing many strange quarks, such as the Ω-Ω dibaryon, which can theoretically be produced in collisions. If one of those particles were absorbed by an ordinary nucleus, such as one in a detector or the wall of the beampipe, what would happen to such a nucleus? (Note that the LHC does have detectors like VELO only a few millimeters from the collision point, so they could last long enough to get there even if they only lasted ~10^-10 sec) My understanding is that the nucleus would turn into a hypernucleus, but would it be possible for such a hypernucleus to decay to a strangelet with those quarks, if the strangelet with those quarks had lower energy than the hypernucleus? (This seems plausible because the hypernucleus will have more energy than the ordinary nucleus.)

If so, it seems like this would be a way to create a strangelet that isn’t ruled out by the LSAG report. It might also not be ruled out by cosmic ray collisions with Earth or the Moon, because these highly strange particles (if I understand it correctly) are easier to produce in the central rapidity region rather than the ends of the rapidity region.

What am I missing here? I admit that my knowledge of nuclear physics is limited so I might be just completely off base here.

 

[ohwilleke]

Experiments Won't Trigger The Collapse Of The Universe​

The best available measurements and theory suggest that given the mass of the Higgs boson and the running of various Standard Model physics parameters with energy scale, that the vacuum is only "metastable" and has a tiny probability of collapsing and ending the universe as we know it. But events like this are likely to happen only once in a period of time that is significantly longer than the current age of the universe.

A new preprint looks at whether ultra-high energy cosmic rays or particle collider concentrations of energy could trigger such a vacuum collapse.

Fortunately for us, the bottom line is that we are safe from that happening. We are many orders of magnitude in energy scales below the danger zone.

Other stuff

The risk of the LHC creating a dangerous black hole has been evaluated and is essentially nil. (Also, tiny black holes evaporate extremely fast due to Hawking radiation.)

Heuristically, the thing that keeps any collision product at the LHC from being a concern is that ultimately the collider is colliding only two atoms, and even if something unexpected happened so that energy from several very high energy atoms collided, it still wouldn't involve that much energy.

A nuclear bomb has kilograms of nuclear material. Each mole (grams times atomic number) of an element has about 6 * 10²³ atoms in it. So no one collision, in a worst case scenario, could do much more than to damage some of the equipment at CERN itself.

 

[vanhees71]

Since we are still posting happily in this forum and the LHC has been running for more than 10 years, I'd say these doomsday scenarios are pretty well disproven by experiment now too ;-)).

 

[Athena319]

Since we are still posting happily in this forum and the LHC has been running for more than 10 years, I'd say these doomsday scenarios are pretty well disproven by experiment now too ;-)).

Not necessarily, technically. It's possible that there's some low probability per collision of a doomsday event, and we've just gotten lucky so far.

 

[Vanadium 50]

Not necessarily, technically. It's possible that there's some low probability per collision of a doomsday event, and we've just gotten lucky so far.

Sure. And that possibility can never be excluded.

Eating cornflakes for breakfast may have a one in a billion probability of summoning the archdemon Glorbiz, Destroyer of Words. It hasn't happened - maybe we're just lucky. Prudence indicates we should ban cornflakes immediately! Or maybe cornflakes repel Glorbiz, and we should mandate them.

 

[PeterDonis]

It's possible that there's some low probability per collision of a doomsday event

How many collisions have already taken place? (Hint: it's a very, very large number.) How low would the corresponding probability have to be for us not to have observed a doomsday event yet? (Hint: it's a very, very small number, much smaller than probabilities we routinely ignore when planning for the future.)

 

[Vanadium 50]

How many collisions have already taken place?

Ballpark, a few trillion.

We are more confident in LHC safety than cornflakes and demon safety,

 

[mfb]

266/fb delivered to CMS, about the same for ATLAS, a bit for LHCb, a negligible amount for ALICE, so around 550/fb in total. At an inelastic cross section of around 80 mb we had 550/fb * 80 mb = 4.4*10¹⁶ or 44 quadrillion (44,000 trillion) collisions.

While running at the record luminosity of around 2.2E34/(cm²s) for ATLAS and CMS each, the LHC has around 4 billion collisions per second.

How many collisions have already taken place? (Hint: it's a very, very large number.) How low would the corresponding probability have to be for us not to have observed a doomsday event yet? (Hint: it's a very, very small number, much smaller than probabilities we routinely ignore when planning for the future.)

We can ignore one in a trillion chances if we talk about things people do a few times per year, but that argument doesn't work if you have a huge number of attempts. Just looking at past LHC collisions cannot rule out e.g. a 1 in 50 quadrillion chance of something happening, which sounds small, but that chance is enough to have this happening multiple times in the future - we expect a total of ~500 quadrillion collisions over the lifetime of the LHC.We know there can't be a risk because natural collisions with a higher energy happen all the time. A higher energy increases the chance of things happening.

but would it be possible for such a hypernucleus to decay to a strangelet with those quarks, if the strangelet with those quarks had lower energy than the hypernucleus?

It cannot. And if it could for some reason, then it would happen naturally all the time which means it can't be dangerous.