Scientists To Hunt For Supersymmetric Particle In LHC

An anonymous reader notes this article about the upcoming restart of the LHC. "A senior researcher at the Large Hadron Collider says a new particle could be detected this year that is even more exciting than the Higgs boson. The accelerator is due to come back online in March after an upgrade that has given it a big boost in energy. This could force the first so-called supersymmetric particle to appear in the machine, with the most likely candidate being the gluino. Its detection would give scientists direct pointers to "dark matter". And that would be a big opening into some of the remaining mysteries of the universe. 'It could be as early as this year. Summer may be a bit hard but late summer maybe, if we're really lucky,' said Prof Beate Heinemann, who is a spokeswoman for the Atlas experiment, one of the big particle detectors at the LHC. 'We hope that we're just now at this threshold that we're finding another world, like antimatter for instance. We found antimatter in the beginning of the last century. Maybe we'll find now supersymmetric matter.'"

Comments

2x power

[monkeyzoo]

The upgrade they completed DOUBLES the energy!

Re:2x power

[fisted]

Oh noes. So we're all gonna die, like, twice!

Re:2x power

[Drexus]

And at which point, all past experiments will want another shot at confirming results — drawing a reference point for new experiments of tomorrow.

Re:2x power

[iggymanz]

If true we would see black holes of planetary mass orbiting stars. But that is not the case, we see the usual rocky or gas giant planets.

Re:2x power

[PPH]

Black holes that small would be hard to see. And if created by advanced civilizations with LHC-sized accelerators, very rare. And then these black holes would evaporate via Hawking radiation quite rapidly (on astronomical time scales).

Re:2x power

[hcs_$reboot]

Some people are worrying about doubling the LHC power.

Re:2x power

[iggymanz]

Planets of earth sized mass (our hypothetical LHC-building self-immolators) cause perturbations in the orbits planets we can see

Re:2x power

[amaurea]

To make a planet-eating black hole from an accelerator experiment you need to assume that Hawking ratiation doesn't exist (or is extremely feeble), or those black holes would evaporate instantly before they can accrete any matter. So you would end up with planet-mass black holes orbiting stars.

Even if you turned off Hawking radiation, it would still be hard for a black hole from a particle accelerator to actually eat the planet. Let's say you have an accelerator much more powerful than the LHC, with a center-of-mass energy of 1 PeV. If all that were used to produce a black hole, it would have a mass of 1.8e-21 kg. An electron or proton a single hydrogen radius away from it (which we can use as a typical intermolecular distance in the Earth for simplicity) would feel an acceleration of 1e-11 m/s^2, which is absolutely tiny compared to the electrical forces that govern motion on those scales. A small black hole like that behaves much like a neutrino - it hardly interacts with anything. And it needs to do that to grow. I think we could have lots of these inside the Earth and not even notice (dun-dun-DUUN!).

Even if you included Hawking radiation but somehow only turned it on after the black hole had consumed the planet, you still wouldn't get rid of the planet-mass black hole, as a hole of that size evaporates extremely slowly, and would have a life time of more than 5e50 years.

Planet-mass black holes could be detected via gravitational microlensing. Planets are regularly detected this way. But it may be hard to distinguish those black holes from planets. As far as I know we can't exclude a population of these in orbit around a fraction of the stars in the milky way. The accretion events, when the planets are eaten, would probably be quite bright, and might be visible as mini-supernovas.

Re:2x power

[buchner.johannes]

Black holes that small would be hard to see. And if created by advanced civilizations with LHC-sized accelerators, very rare. And then these black holes would evaporate via Hawking radiation quite rapidly (on astronomical time scales).

You are way off. Macroscopic black holes, for all intents and purposes, do not evaporate.
A Earth-mass black hole will take 10^50 years to evaporate. (The age of the universe is ~10^10 years).

If you want a black hole that evaporates within a reasonable time, like the age of the universe, you are looking at 10^11 kg. That is tiny compared to a planet, somewhat comparable to the Great Pyramid of Giza.

Re:2x power

[buchner.johannes]

Even if you turned off Hawking radiation, it would still be hard for a black hole from a particle accelerator to actually eat the planet. Let's say you have an accelerator much more powerful than the LHC, with a center-of-mass energy of 1 PeV. If all that were used to produce a black hole, it would have a mass of 1.8e-21 kg. An electron or proton a single hydrogen radius away from it (which we can use as a typical intermolecular distance in the Earth for simplicity) would feel an acceleration of 1e-11 m/s^2, which is absolutely tiny compared to the electrical forces that govern motion on those scales. A small black hole like that behaves much like a neutrino - it hardly interacts with anything. And it needs to do that to grow. I think we could have lots of these inside the Earth and not even notice (dun-dun-DUUN!).

There is an even easier answer to address the fears about LHC micro-black holes. Particles with energies comparable or exceeding LHC energies hit the atmosphere of earth every day, and we observe their effects with Cosmic-ray observatories such as Cerenkov Detectors. Business as usual, and nothing exciting happened for the last billion years.

Re:2x power

[Anonymous Coward]

Black holes that small would be hard to see. And if created by advanced civilizations with LHC-sized accelerators, very rare. And then these black holes would evaporate via Hawking radiation quite rapidly (on astronomical time scales).

So what you're saying is the unexplained high intensity gamma-ray bursts are civilizations about where we are on the evolutionary scale blowing themselves up?

Re:2x power

[Tablizer]

these black holes would evaporate via Hawking radiation quite rapidly

But there is a small chance Hawking was wrong and that we will all die.

Re:2x power

[Maritz]

Nature creates collisions in the atmosphere (cosmic rays) that are many orders of magnitude more powerful than anything at the LHC, and has been doing so since as long as the earth existed. No black holes yet. :)

Re:2x power

[Anonymous Coward]

Why would it grow? They are talking of blackholes the size of a couole of particles. Your coffee mug has way more mass than those, and pulls more stuff to it. And it's not growing exponentially unless you forgot to wash it.

Re:2x power

[Anonymous Coward]

the theory is derived from OBSERVATION and EXPERIMENTATION.

Electric universe is nothing more than crank science, and both observation and experimentation completely contradict it.

Try studying comets from both sides.

Next try working out orbital mechanics for the moon and earth system with electric universe, then try using those same numbers for checking your own weight. After you do that try checking the numbers for attraction between you and somebody sitting next to you. Those numbers and constants do not work at all. These are experiments you can do yourself at home!

Re:2x power

[Tablizer]

But that's not something we can control. We can't do anything about things we cannot control. I don't see how the existence of uncontrollable risks should affect our decisions about controllable risks.

Re:2x power

[iggymanz]

Sorry, that tired old horse argument doesn't hold because the black hole formed in the cosmic ray case not at rest in the earth frame as one created at the LHC will be.

The Giant Suck will get us all! We're DOOOOMED. DOOOOOOMED I tell you!

Re:Wow they might find a new particle (or not)

[SuricouRaven]

Failing to find what the theories predict is still an advancement in knowledge.

I hope there'll be no supersymmetry

[Anonymous Coward]

No matter what virtues it may have, a theory that doubles the number of elementary particles is a gross violation of Ockham's razor. Well, maybe that's the way the world is made up. I just hope it isn't.

Re:I hope there'll be no supersymmetry

[Anonymous Coward]

The question is, do you have a simpler explanation? If not (and no, I'm not convinced that 13 dimensional vibrating strings is simpler) then Ockham's razor still holds.

Re:I hope there'll be no supersymmetry

[hweimer]

The question is, do you have a simpler explanation?

Er, stick to the Standard Model since there is no experimental observation to the contrary? (Okay, there are neutrino oscillations, but it is possible to fix this without supersymmetry or extra dimensions.)

Re:I hope there'll be no supersymmetry

[anarchyboy]

Well theres neutrino oscillations, g-2 of the muon, baryogenisis, dark matter, dark energy and inflation to name a few.

Then there is the hierarchy problem and flavour problems which aren't experimental observations so you might not want to count them and thats not even touching the problem of trying to get a consistent theory for the standard model and gravity together.

Re:I hope there'll be no supersymmetry

[hweimer]

Other than muon g-2 (which might or might not be there), none of the things you mention actually contradict the standard model because it simply makes no statement about them. It's way too early to send the standard model down the drain because the alternatives either contain more speculative physics than known physics or are conceptually elegant but still wrong (see SU(5)).

LHC upgrade

[Anonymous Coward]

I hope it does not include systemd

Re:Wow they might find a new particle (or not)

[bill_mcgonigle]

Failing to find what the theories predict is still an advancement in knowledge.

Failing to find what a theory predicts largely excludes it (assuming the experiment isn't faulty), and is a good result and useful science. Whether or not science reporters can grok that is a job for the PR department (LHC has a good one - c.f. Particle Fever).

The Supersymmetry folks did not expect to find a Higgs boson at 127GeV. ATLAS did find what looks like a Higgs boson at 127GeV.

If there were a guarantee that this particle is the Higgs, then there wouldn't be a need to continue upwards to test Supersymmetry. But it's not guaranteed - so not finding supersymmetric pairs at the higher energies will firmly rule out the Supersymmetry model (reassigning physicists to other models) and increase the confidence that the discovered particle is the Higgs.

Hunt for Particle in LHC

[PPH]

Just turn it on its side and smack it a couple of times. That's how I get loose bits out of machinery.

Re:Hunt for Particle in LHC

[Tablizer]

That's why they don't hire wookies.

Re:Wow they might find a new particle (or not)

[iggymanz]

our BEST and most widely accepted model, the Standard Model, has problems. The Higgs boson is too light, and in fact the lighter it is the further off the Standard Model is

http://www.quantumdiaries.org/...

Yes, yes !

[Kekke]

We found it ...zup...
-end of transmission from earth-

Re:Yes, yes !

[Tablizer]

On the up-side, the Galactic Darwin Award is a very shiny and attractive award.

Re:I hope there'll be no dark matter

[DanielOom]

What could happen if they discovered the Voldemortino?

Actually 13/8 times the energy

[Roger W Moore]

The centre of mass energy is actually going from 8 to 13 TeV so it is not a doubling of the energy. However we are increasing the luminosity (number of protons in the beam) too so we will probably have at least twice the reach in energy that we did before. While the article makes it sound like something new looking for Supersymmetry (SUSY) is something we have been searching for since the start of the LHC.

SUSY is the leading candidate theory to explain why the higgs is so much lower in energy that the energy scale at which gravity becomes important: the Planck scale. While there are good arguments to suppose that SUSY is within range of the LHC energy I would put about as much store in a prediction of which SUSY particle will be discovered first as I would in a 14 day weather forecast: there is some science that goes into it but there are so many unknowns that the prediction is likely to be junk. Worse, while we can be pretty certain that there will be some sort of weather in 14 days there is no guarantee that there is a lightest SUSY particle: SUSY might not exist in nature although this itself would raise some interesting questions.

Re:Actually 13/8 times the energy

[Pro-feet]

True.
But, if we are going to discover a SUSY particle in the first months after turning on, it is indeed very likely to be the gluino. Just because the probability of creating it, if it is within kinematical reach, will be large, compared to many other SUSY particles. All weakly produced particles will take more data to get hold of because they are rarer. In addition, in most models, the gluino decays give rise to spectacular collisions, that are relatively easy to distinnguish from known backgrounds.

Re:Actually 13/8 times the energy

[Roger W Moore]

...and what about squarks? These are strongly coupled and there are some arguments to suggest that the stop squark is most likely to have the lowest mass.

Re:Actually 13/8 times the energy

[Pro-feet]

Yes, the stop (and sbottom) squark is a prime target too.
But it will come again a little later than the gluino. The reason is that we have excluded the gluino in most scenarios already wel beyond 1.2TeV, while the stop squark is unlimited above ~700GeV (and that's assuming ideal decays).
Now, with the increase in energy, the heavier is the particle, the higher the increase in production probability. This is visualised in the following (M_X being the "mass" of the produced system, in this case twice the gluino or stop mass, since they come in paris; and the solid line being the most relevant here for strong production):
http://www.hep.ph.ic.ac.uk/~ws...
For a gluino at the limit of what we could exclude until now, a ~ fifteenfold increase in production probability is expected, while for stops it will be more a factor 6 or 7.
A final argument why stops take a little longer is that the main backgrounds (top quark pairs, mainly) are looking quite similar even in the easier decay modes, while many of the possible gluino decays lead to signals that have a tiny background (like four-top final states).

Re:Actually 13/8 times the energy

[Roger W Moore]

But it will come again a little later than the gluino.

All these arguments are reasons why it is easier to see stops than gluinos which I'm already aware of. However what you are also assuming here is that the gluino mass is comparable to the squark masses. Is there any justification for that because I've not seen it e.g. if the gluino mass is 3 times that of the squarks it will not be seen first.

Unless there is an argument to say why this is disfavoured you are drawing unwarranted conclusions based on detector sensitivities. It doesn't matter how much more sensitive we are in ATLAS to gluinos or how much faster we can do the analysis if we can't produce any gluinos to detect because their mass is too high.

Re:Actually 13/8 times the energy

[Pro-feet]

I referred to the current limits (~1.2TeV for gluino versus 700GeV for stop), which is more or less corresponding to a couple of events on a small background - for both gluino and stop searches at their high-mass extremes.
Production probability (cross section) plot for 8TeV can be seen here:
http://inspirehep.net/record/1...
Couldn't find a 13TeV version quickly; but the trends are the same: much higher probability for gluino paris (~g~g in red) than for stop pairs (blue curve).
Now, when we move from 8TeV to 13TeV, for a gluino just at the limit, the production probability goes up much more than for a stop at its own somewhat lower limit.
So I'm not assuming same mass, I'm assuming a heavier gluino actually.
Of course, for a 5TeV gluino, no chance; but the same goes for a 2TeV stop - production rate too low.

Re:Actually 13/8 times the energy

[Roger W Moore]

You are completely missing the point. Consider two scenarios: (a) a 1.25 TeV gluino and a 1 TeV stop and (b) a 5 TeV gluino and a 750 GeV stop. Which of these two possible SUSY models is more likely? (a) or (b)? If the answer is (as I suspect) that they are both roughly equally likely then you are just as likely to see the stop quark first as you are to see a gluino first: in (a) you see the gluino and in (b) you see the stop first.

If you want to say that seeing a gluino is more likely then you have to be able to say that models like (a) are more likely than models like (b). For example we do have theory to support that the stop is probably the lightest of the squarks. Without a prediction of the mass of a gluino relative to the squark masses you have no real basis to say that you will see a gluino first because you no idea what the gluino mass is relative to the stop mass. About the only argument you might make is that there is marginally more available phase space for the stop mass because the current limit is below the gluino mass limit but given that the upper bounds are not well constrained this is not much of an argument.

Re:Actually 13/8 times the energy

[Pro-feet]

For the same reasons the stop is expected light (naturalness, i.e. SUSY as a solution to the hierarchy problem), also the gluino is expected light. What is light? Some put it at 400GeV for the stop, and 1.5 TeV for the gluino. But it's a bit of a subjective point. So if you like natural SUSY, you expect the gluino to be around the corner, and the stop to be within reach, but probably decaying softly and therefore having escaped detection so far. How likely is such a scenario? There is no good metrci for the likelihood of models. Therefore I prefer to look at it experimentally, i.e. wrt our current limits. If the gluino and stop are just beyond our current limits, then, according to my previous posts (which apparenntly completely missed the point...) the gluino will jump in our face, while the stop will take more time.

Re:Actually 13/8 times the energy

[Roger W Moore]

Therefore I prefer to look at it experimentally, i.e. wrt our current limits. If the gluino and stop are just beyond our current limits, then, according to my previous posts (which apparenntly completely missed the point...) the gluino will jump in our face

How is making an arbitrary choice that stop and gluino are both just beyond the current limits "looking at it experimentally"? What's to prevent stop being just beyond our detection range with the gluino being far above it? The argument for a light stop is that the top has a large correction to the Higgs mass due to its strong coupling: I'm not aware of any such argument for the gluon since it is massless. Natural SUSY does not place any hard limits on the upper bounds: things just get less natural as the masses increase but there is no line in the sand where the models cease to be natural. You could perhaps argue that it is unnatural by the time you get to ~10TeV or higher without SUSY but, as you say, it is purely subjective and not at all 'experimental'.

Re:Actually 13/8 times the energy

[Pro-feet]

The gluino plays a similar naturalness role as the stop, at 2-loop level. Now you are aware, though I made that point in my previous post too.

Just beyond the limits is not an arbitrary choice. Given our current limits already, naturalness points to these masses being as low as possible.

Re:Actually 13/8 times the energy

[Roger W Moore]

The gluino plays a similar naturalness role as the stop, at 2-loop level.

Do you have a paper to back that up? It seems very surprising that a 2-loop level effect would have the same constraints as something at the tree level.

Just beyond the limits is not an arbitrary choice. Given our current limits already, naturalness points to these masses being as low as possible.

Not quite. Given our current understanding it would appear more natural to have SUSY at a lower mass scale but if we find SUSY at 10TeV all that means is that SUSY is perhaps less natural than it could have been. It's like tossing a coin: how many heads in a row do you need to get before you conclude that the coin is weighted? You can draw an arbitrary line in the sand and say '5 sigma' but it is just that an arbitrary line in the sand. With SUSY we have the same problem: you can put an arbitrary line on the energy scale and say "above X TeV it is unnatural" but it is just that: an arbitrary line. You might be happier if SUSY existed at a lower energy scale (I would be too!) but the universe is not there just to make us happy.

Re:Actually 13/8 times the energy

[Pro-feet]

A classic by now on SUSY naturalness related to LHC: http://arxiv.org/abs/1110.6926
See Section II.

Supersymmetry already has strong constraints

[hweimer]

The observation that the electron electric dipole moment is less than 10^-29 e cm (as measured by the ACME experiment in 2013) already places strong constraints on supersymmetric partner masses, making it rather unlikely that the upgraded LHC will see anything.

Re:Supersymmetry already has strong constraints

[Lawrence_Bird]

IIRC there are other results that further limit the space available for SUSY, minimal or otherwise. But just like string theory, its supporters refuse to go away.

Re:Wow they might find a new particle (or not)

[Anonymous Coward]

(Before anyone replies - climate skeptics know more about the science than the believers. A recent research headline that didn't make Slashdot ... )

There is a difference between being skeptical and claiming that something is wrong, thus the need to distinguish between a skeptic and a denier.

proton decay?

[Vicious Penguin]

IANAPP, but I thought that the lack of observed proton decay had largely invalidated supersymmetry.

I mean, "yea science" and all, but I suppose am I missing something?

Re:proton decay?

[iggymanz]

we've only looked for proton decay on the order of 10^34 years half-life, if it's larger there is no extant experiment that would see it.

Re:proton decay?

[Pro-feet]

You only need one extra symmetry (so-called R parity) to protext the proton from decay. Such a symmetry is not far-fetched, and arises in some GUT models even dynamically. Imposing this R parity yields also automatically a stable lightest supersymmetric particle, and it turns out that that can be a really plausible dark-matter candidate. This said, studies also go on about models where this R parity is not conserved, still keeping the proton's lifetime within the stringent experimental bounds.

Re:Don't get too upset.

[blue trane]

Downvoting destroys, so there is an effect.

Re:Wow they might find a new particle (or not)

[Pro-feet]

A 126 GeV Higgs boson as we (also CMS did, btw) have observed it, and studied its properties in detail, is no problem to be accomodated in even the minimal versions of supersymmetry. What makes you say it was not expected at that mass? It's on the high side, but the higher the mass, the more that Higgs boson with or without supersymmetry would look the same in our detectors...

Key: beyond-the-standard-model physics

[l2718]

Specifically finding SUSY would be great for the people who predicted it. From the point of view of particle physics as a whole, the goal is seeing some physics not covered by the standard model. In any case unless you can write papers on the topic, it's useless to speculate what will be found. Since the accelerator already exists we don't need any hype about it.

However, if even this energy upgrade doesn't bring signals beyond the standard model, it will be very hard to ask for many billions of USD to build the next accelerator, based only on the hope of "we might see something".

Not being a physicist....

[Whiteox]

I'm pretty sure that you guys are making all this up. It looks like cern geeks keep inventing theoretical particles, then search for them, find something that almost fits, then theorizes that another particle must exist, look for that until you find something that almost fits, then look for another particle etc. etc. etc.
It's like those astrophysicists. They have no idea either and keep making up hypotheses, backed up by arcane invented maths using as many dimensions as they can so they can postulate weirder scenarios, trying to link up the micro-cosmic and macro-cosmic.
Anyway, doesn't all this reek of 'ether'? - You know - an invisible matter that pervades space?

Re:Not being a physicist....

[ClickOnThis]

I'm pretty sure that you guys are making all this up.

You admit you are not a physicist. That means you admit you do not know what your are talking about.

It looks like cern geeks keep inventing theoretical particles, then search for them, find something that almost fits, then theorizes that another particle must exist, look for that until you find something that almost fits, then look for another particle etc. etc. etc.

Not just CERN "geeks" but scientists from all over the world, looking for patterns in the way the universe is constructed. Patterns are useful, because they allow us to distill vast amounts of knowledge into a much smaller number of concepts. It's no secret that scientists try to find patterns that fit observations, and then try to extend their applicability to other potential observations, with the goal of finding those patterns that do the best job of summarizing and conceptualizing our understanding of nature and our ability to predict its behavior.

It's like those astrophysicists. They have no idea either and keep making up hypotheses, backed up by arcane invented maths using as many dimensions as they can so they can postulate weirder scenarios, trying to link up the micro-cosmic and macro-cosmic.

As I said, you don't know what you are talking about. Astrophysicists don't "make up" hypotheses out of thin air -- they base them on observations of the universe. And they don't use "arcane" math with lots of dimensions just so they can create "weird" scenarios. Rather, they're trying to find patterns that fit observations, per above. The math is a tool that supports this endeavor.

the particle physics culture problem

[Goldsmith]

Particle physics did an excellent job building a multidisciplinary, international, scientific workforce. As a field, they are largely independent of the world of 12-36 month grants and frequent peer reviewed publications the rest of us live in. More scientific fields should look to particle physics for guidance on self-organization and priority setting.

However, in the process, particle physics has separated itself from general physics. Outside of some cosmologists, there are not many other physicists who can (or care to) work with particle physics colleagues. We were on board for Higgs, but I think the physics and more importantly, the culture, has veered off so far from what we're used to that it's going to be hard to justify discoveries as "fundamental."

Re:Wow they might find a new particle (or not)

[ClickOnThis]

Failing to find what the theories predict is still an advancement in knowledge.

That's putting it mildly.

A failed experiment can do more than advance knowledge. It can start a scientific revolution.

Consider what is arguably the most famous failed experiment in history: the Michelson-Morely experiment that failed to show the presence of an aether on which light was thought to travel. The consequences of this failed experiment included the development of Special Relativity.

gluino ?

[MLBs]

I'm sorry, but all *uino are reserved for embedded controller related product names.