LHC experiments bring new insight into matter of the primordial universe

Aug 13, 2012
A view of the detector in the 12,500-ton Compact Muon Solenoid experiment (CMS). Image courtesy of CERN

(Phys.org) -- Experiments using heavy ions at CERN's Large Hadron Collider (LHC) are advancing understanding of the primordial universe. The ALICE, ATLAS and CMS collaborations have made new measurements of the kind of matter that probably existed in the first instants of the universe. They will present their latest results at the Quark Matter 2012 conference, which starts today in Washington DC. The new findings are based mainly on the four-week LHC run with lead ions in 2011, during which the experiments collected 20 times more data than in 2010.

Just after the , quarks and gluons – basic building blocks of matter – were not confined inside composite particles such as protons and neutrons, as they are today. Instead, they moved freely in a state of matter known as "quark–gluon plasma". Collisions of lead in the LHC, the world’s most powerful particle accelerator, recreate for a fleeting moment conditions similar to those of the early universe. By examining a billion or so of these collisions, the experiments have been able to make more precise measurements of the properties of matter under these extreme conditions.

“The field of heavy-ion physics is crucial for probing the properties of matter in the , one of the key questions of fundamental physics that the LHC and its experiments are designed to address. It illustrates how in addition to the investigation of the recently discovered Higgs-like boson, physicists at the LHC are studying many other important phenomena in both proton–proton and lead–lead collisions,” said CERN Director-General Rolf Heuer.

At the conference, the ALICE, and CMS collaborations will present more refined characterizations of the densest and hottest matter ever studied in the laboratory – 100,000 times hotter than the interior of the Sun and denser than a neutron star.

ALICE will present a wealth of new results on all aspects of the evolution of high-density, strongly interacting matter in both space and time. Important studies deal with “charmed particles”, which contain a charm or anticharm quark. Charm quarks, 100 times heavier than the up and down quarks that form normal matter, are significantly decelerated by their passage through quark–gluon plasma, offering scientists a unique tool to probe its properties. ALICE physicists will report indications that the flow in the plasma is so strong that the heavy charmed particles are dragged along by it. The experiment has also observed indications of a thermalization phenomenon, which involves the recombination of charm and anticharm quarks to form “charmonium”.

“This is only one leading example of the scientific opportunities in reach of the ALICE experiment,” said Paolo Giubellino, spokesperson of the ALICE collaboration. “With more data still being analysed and further data-taking scheduled for next February, we are closer than ever to unravelling the properties of the primordial state of the universe: the quark–gluon plasma.”

In the 1980s, the initial dissociation of charmonium was proposed as a direct signature for the formation of quark–gluon plasma, and first experimental indications of this dissociation were reported from fixed-target experiments at ’s Super Proton Synchrotron in 2000. The much higher energy of the makes it possible for the first time to study similar tightly-bound states of the heavier beauty quarks. The hypothesis was that, depending on their binding energy, some of these states would “melt” in the plasma produced, while others would survive the extreme temperature. The CMS experiment now observes clear signs of the expected sequential suppression of the “quarkonium” (quark–antiquark) states.

“CMS will present important new heavy-ion results not only on quarkonium suppression, but also on bulk properties of the medium and on a variety of studies of jet quenching,” said CMS spokesperson Joseph Incandela. “We are entering an exciting new era of high-precision research on strongly interacting matter at the highest energies produced in the laboratory.”

The quenching of jets is the phenomenon in which highly energetic sprays of particles break up in the dense quark–gluon plasma, giving scientists detailed information about the density and properties of the produced matter. ATLAS will report new findings on jet quenching, including a high-precision study of how the jets fragment in matter, and on the correlations between jets and electroweak bosons. The results are complementary to other exciting ones, including groundbreaking findings on the flow of the plasma.

“We have entered a new phase in which we not only observe the phenomenon of quark–gluon plasma, but where we can also make high-precision using a variety of probes,” said ATLAS spokesperson Fabiola Gianotti. “The studies will contribute significantly to our understanding of the early universe.” 

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GFoyle
3.7 / 5 (6) Aug 13, 2012
These exciting experiments, results, and theoretical implications are well presented in the best writing I've read in PhysOrg in a long time. My thanks to the unnamed author as well as the many scientists.
vacuum-mechanics
1 / 5 (3) Aug 13, 2012
The field of heavy-ion physics is crucial for probing the properties of matter in the primordial universe, one of the key questions of fundamental physics that the LHC and its experiments are designed to address. ...The studies will contribute significantly to our understanding of the early universe.

This based on the conventional concept of the big bang theory in which there is a huge infinite densed of energy, but the crucial problem is that where is this infinite energy come from ( i.e. it violate principle of conservation of energy)? May be this paper could help to solve the problem.
http://www.vacuum...mid=7=en
ziphead
2.1 / 5 (7) Aug 13, 2012
ALICE; who the frack is ALICE?
Any news from CASTOR?
Vendicar_Decarian
3.7 / 5 (3) Aug 13, 2012
Castor didn't survive the explosion.
Lagerhaus
5 / 5 (1) Aug 14, 2012
I like to know if anyone has studied the following problem. With the empirical findings about the higgs boson and the theory of the higgs field, the next step would be to find what particle will assert gravity to mass, which was given by the interaction with the higgs field. So there is a theory this will be the graviton. This would mean that this graviton as a particle is limited by the speed of light. Therefore gravity's effect would be limited by the speed of light? Has anyone measured if the loss of mass, like for example in supernovi explosions, leads to a loss of gravity not in an instant but with the limit of the speed of light?
jonnyboy
1 / 5 (5) Aug 14, 2012
I like to know if anyone has studied the following problem. With the empirical findings about the higgs boson and the theory of the higgs field, the next step would be to find what particle will assert gravity to mass, which was given by the interaction with the higgs field. So there is a theory this will be the graviton. This would mean that this graviton as a particle is limited by the speed of light. Therefore gravity's effect would be limited by the speed of light? Has anyone measured if the loss of mass, like for example in supernovi explosions, leads to a loss of gravity not in an instant but with the limit of the speed of light?


yes
Satene
3 / 5 (2) Aug 14, 2012
During supernova explosions the most of energy is released in form of photons and neutrinos, which indeed move with speed of light (or slightly slower/faster). I presume, only subtle portion of energy will be released in form of superluminal gravitational waves and this loss of mass would be difficult to detect with material balance of supernova explosion.
yes
not.
daywalk3r
3.9 / 5 (11) Aug 14, 2012
Has anyone measured if the loss of mass,like for example in supernovi explosions,leads to a loss of gravity not in an instant but with the limit of the speed of light?
Look up "gravity-wave detectors" as those were designed and deployed for such purposes (LIGO, VIRGO, GEO 600 - to name a few). Though none of them have yet been able to detect anything - be it either due to lack of sensitivity, or lack of gravitational waves altogether.

But the whole issue is a bit more complicated than that..

Gravity is rather related to the energy density gradient in spacetime (eg. curvature) than just to what is currently understood under "mass" (which is related to energy by the famous E=mc^2 equation from Einstein). And as energy in a closed system (Universe) is neither created nor destroyed (only displaced), there is no "instant" change in gravity taking place.

So until there is evidence that energy/mass can be displaced at superluminal speeds, it is safe to assume gravity obeys TSoL too.
Torbjorn_Larsson_OM
not rated yet Aug 14, 2012
@ vacuum-mechanics:

There isn't any "infinite [density of] energy in the old big bang cosmology or the new inflationary standard cosmology. Bad troll is trolling badly.

@ Lagerhouse:

The lightspeed relativity of gravity was measured already before it was known as general relativity (GR). IIRC from observations of Jupiter's moons.

Mass loss in relativity has been measured a long time too. Of course lost mass leads to decreased gravity, but I dunno if anyone has measured it on the same system.

Especially energy loss (and so mass loss) in spin down by neutron stars has been observed - deviations from spherical form will cause gravity waves.

Gravitons are easily extracted from quantizing gravity at low energies. (Making it a field theory approximation I suppose - it is at high energies the effective theory of GR breaks down.)

But while the neutron star observations are pretty unambiguous no one has detected gravity waves more generally, or gravitons at all.
Torbjorn_Larsson_OM
not rated yet Aug 14, 2012
[cont]

Actually, the higgs field, if it stands up to testing with the found particle, is our first universal scalar field. It is more like inflationary physics.

I hear the higgs field being dual used as the inflation field ("inflaton field") has been suggested and then excluded on theoretical grounds. But the Planck probe results on inflation, due this year, will be interesting in this light. There should be a synergy here.

Makes you wonder if inflation has observable particles like the higgs field presumably has. Certainly it has fluctuations, its primordial fluctuations should be what caused cosmic microwave background fluctuations and correlated structure formation. (They wouldn't be called "inflatons" I think, it is a quasiparticle used to connote the state of the universe in the field.)

I dunno if there are constraints forbidding more longstanding fluctuations, i.e. particles, in inflation fields.
Torbjorn_Larsson_OM
3 / 5 (2) Aug 14, 2012
You know what, I am tired of this "infinite energy" trope that is so misunderstood and misused by various science denialists.

It was an observation on early big bang theories, that running the expansion backwards goes to higher energy densities. So creationists and other crackpots latched on to this, as well as theoretical physicists that saw both synergies to similar gravitational singularities (black holes) and to making a perfectly constrained fundamental Theory Of Everything.

Of course we know have string theory making a mockery of "perfectly constrained" as well as inflation theory that embeds the earlier big bang expansion with a period before thermalization. It too have the property that if you run its expansion backwards a worldline blueshifts to higher energy densities. Eventually you run into the Planck dimensional constraint as your wordlines emerges out of a Planck volume.
Torbjorn_Larsson_OM
not rated yet Aug 14, 2012
[cont]
But you know what? This process happens around us, hell _in_ us, in todays universe too! Expansion of spacetime means unambiguously that particle wordlines expands out of Planck dimensional volumes as you observe the physics at highest possible resolution.

The only difference then is that this continuous "singularity" (you wish) process descends back up to where spacetime emerges from Planck energy densities _into_ (slightly lower than) Planck energy densities.

It is no more mysterious than the physics of Planck scales in the first place. Something that string theory explains by dualities "wrapping around" into lower energies and larger scales.

Meanwhile, eternal inflation can be backwards eternal for all we know, and Susskind now makes a good point that this is most likely the case. Not that initial conditions may be unnecessary of course, in Susskind's words:

"I did not claim that the concept of an initial condition is unnecessary. I don't know if it is or not."
Deathclock
not rated yet Aug 14, 2012
ALICE; who the frack is ALICE?
Any news from CASTOR?


A Large Ion Collider Experiment.
Lagerhaus
not rated yet Aug 14, 2012
Thank you, for all the great comments. There is another thing which always bothered me, the singularity. No matter if in a black hole or at the big bang. Why are so many sure that it is infinite small, I would understand dense but the infinite small? Is it because the math leads to it? I would be fine with very small, but smaller than an H atom for all the universe created by the big bang?
daywalk3r
4 / 5 (12) Aug 14, 2012
Why are so many sure that it is infinite small, I would understand dense but the infinite small?
I try to answer with a counter-question: Why are so many sure that GOD exists? :-)

At this point, noone can be "sure", but sure many can "believe".

Is it because the math leads to it?

It is because of the incompleteness of our current theories, which do not propose/predict/include anything that could stop further collapse of a mass after it reaches/falls bellow its associated Schwarzschild radius. And yes, it is also what the math (of current theories) leads to, when let completely "off chains".

As long as there is "limited knowledge", there can be "believers". And so in regard to the "infinities", those who "believe" might be just dreamers, but those who are "sure", are just foolish :-)
Satene
1 / 5 (3) Aug 14, 2012
IMO the universe appears like water surface, being observed with its own waves. At the distance everything appears blurred because of scattering of light at the density fluctuations of vacuum - but it doesn't mean, the universe and galaxies doesn't exist there. This model is supported with many observations already and the LHC experiments are mostly irrelevant to it.
antialias_physorg
not rated yet Aug 14, 2012
I would understand dense but the infinite small?

The one necessitates the other. Density is mass per volume. If you can grok infinite density (and we know that black holes have finite mass because their gravitational attraction is finite) then the volume has to be infinitely small.

A bit of a poser is how spacetime behaves when you put it through that much of a wringer. Mass can stretch spacetime (e.g. the distance - on the inside - between the 'center' of a black hole and the event horizon is infinite. Because you can shoot a ray of light and it will never reach the event horizon.) The term 'distance' really is iffy as soon as you enter the event horizon - at least as relates to anything that is 'further out' than you are.

It may be that spacetime inside keeps stretching while the mass keeps collapsing so that a singularity isn't ever reached.
antialias_physorg
4.8 / 5 (4) Aug 14, 2012
Something I have sometimes trouble grasping, when I think about black holes, is the nature of gravity itself.

There are theories that pose an exchange particle (graviton).
However, the spacetime between any point A inside the event horizon of a black hole and any point B further out (even if B is also inside the event horizon) is semi-disconnected. There is no path from A to B - even at the speed of light (There is, obviously, a path from B to A).

Yet black holes still interact gravitationally with stuff outside. So the mass inside the event horizon does manage to exude gravitons outside the event horizon.

So wouldn't this mean that gravitons are either faster than the speed of light? Or that they bypass spacetime altogether some other way.

more likely we're dealing with a force that doesn't really lend itself to explanation via particle interchange but just via geometric modelling (a la Einstein and the 'rubber sheets')
lengould100
not rated yet Aug 15, 2012
Gravity has always puzzled me, reference ftl etc. Example, imagine a huge black hole travelling past a gravitational field measuring device at a significant distance of nearest approach, and at a velocity at a significant proportion of light speed. The mass of the black hole is large enough to significantly overwhelm the gravitational effect of any other nearby mass, such as other stars or etc. What does the measuring device show? Does the device measure the gravitational effect of the passing black hole's vector of gravitational attraction instantateously changing and pointing directly at the real location of the black hole, or is there a delay in gravitational effect proportional to the absolute distance from the measuring device to the black hole, which distance steadily reduces then increases?

Interesting as a thought experiment anyway, (for me lol). My question is, would an observer near the gravitational vector measuring device see the direction of the gravitational ....
lengould100
not rated yet Aug 15, 2012
... vector pointing exactly the same as his telescope points at the passing black hole? (Indicating that changes in gravitational effects occur only at the speed of light). Or will the location percieved by the gravitational detector precede that percieved by the telescope, indicating that gravity is mediated instantaneously?
daywalk3r
3.9 / 5 (11) Aug 15, 2012
As a response to lengoulds question:

Overlooking the fact that your telescope would hardly "perceive" anything when observing an approaching inactive BH (;-D) ..

If the massive object (like a BH) was approaching at a signifficant portion of the speed of light (like 99%), and radiating/reflecting in a detectable spectra (eg. "visible" by your telescope), then from the observational viewpoint of the telescope, it would actually seem as if it was approaching FTL!

But this would be just an illusion caused by the compression (and accompanying blueshift) of the photon wavefront, resulting in a "fast-forward" like effect.

The intensity of the approaching objects gravitational field at the approached observers position should change at the same (illusionary) "sped-up" rate as its photonic image observed through the telescope.

In other words, the gravitational effects should be directly proportional to the perceived data from the telescope.

---> 2nd part of my 1st comment in this thread.
antialias_physorg
not rated yet Aug 15, 2012
Overlooking the fact that your telescope would hardly "perceive" anything when observing an approaching inactive BH

Oh, I think the distortion of the galaxies in the background close to line of sight to the event horizon would be quite noticeable.

then from the observational viewpoint of the telescope, it would actually seem as if it was approaching FTL!

Nope. Why do you think it would? You'd get blueshift ofthe Hawking radiation but that's about it (and that radiation is incredibly tiny/undetectable for all but the smallest black holes).

As long as you are a bit outside the event horizon a black hole does not behave differently than something else of the same mass seen from that distance. (If you're inside the event horizon looking in the direction of the center you wouldn't see anything at all)
daywalk3r
3.9 / 5 (11) Aug 15, 2012
AA, AA..

Firstly, good luck spotting the background distortion for a stellar mass BH from a distance of several thousand or even millions of light years. And secondly..

You might want to try to think harder next time, and also maybe read the whole comment (not just an isolated sentence) while trying to figure it out for yourself, before posting such replies :-P

I believe it's even hardly necessary to explain (for the rest of the readers, at least) where your opposition is at fault.. (as the logical ground for it was actually laid down right in the next paragraph, lol)

Small hint: I was not even specifficaly reffering to a BH, as should be quite clear by reading the whole (and not just the quoted part) of the sencence. So even by this it seems like you obviously must have totally missed the whole point :-)

No problem. Happens to the best :-P

On a side note: The thing you posted about BH's and gravitons is actually one of the major constraints against a GR-graviton based ToG.
antialias_physorg
not rated yet Aug 15, 2012
Firstly, good luck spotting the background distortion for a stellar size BH from a distance of several thousand or even millions of light years.

Done.
http://www.space....axy.html

The original question also stipulated "The mass of the black hole is large enough to significantly overwhelm the gravitational effect of any other nearby mass", which means we're not dealing with millions of light year distant black holes.

You still owe me an explanation on where the 'apparent FTL' happens. I'd really like to know.
lengould100
not rated yet Aug 15, 2012
Still I'd like to see the key question addressed. Presuming the extremely heavy-and-dense object travelling past fairly near was clearly visible, and it doesn't pass close enough to disrupt the observer physically, will the line of sight and the direction pointed to by the gravitational detector coincide or not?
daywalk3r
3.9 / 5 (11) Aug 15, 2012
LOL AA.. AGN vs stellar mass BH ftw :-)

But more to the point: I was trying to make an example to show the illusionaty FTL aspect of the proposed thought-experiment, and relate to it in the later part of my take on the proposed problematic. It was not ment as a direct part of the explanation per se, but rather as a "helping stick". So your concurrece is rather off-topic in this regard.

You still owe me an explanation on where the 'apparent FTL' happens. I'd really like to know.
You mean you still don't grasp it, even after reading the explanation (about the apparent illusion)? :-S

I try to illustrate it on a more "graspable" example:
For an observed object (initially at rest) that starts moving towards the observer at 0.5c, at the time-point at which the observer detects the object starts moving, the object will be allready 1/2 the distance towards the observer.

Which in turn means? (I let that last bit for you to figure out - can't get everything for free x-D)

Best regards.
daywalk3r
3.9 / 5 (11) Aug 15, 2012
Still I'd like to see the key question addressed. Presuming the extremely heavy-and-dense object travelling past fairly near was clearly visible,and it doesn't pass close enough to disrupt the observer physically, will the line of sight and the direction pointed to by the gravitational detector coincide or not?
I did address it allready. But well..

Neglecting any length contraction from "travelling past" (not directly towards) at a signifficant portion of c, and baseing the assumption on a spacetime-curvature model of gravity & conforming to the conservation of energy (& some observational evidence), the answer is:

YES, the "line of sight" should coincide with the direction pointed to by the gravitational detector.

To reitterate: If the effect of gravity is a direct consequence of the energy density gradient of spacetime (eg. curvature), then this effect is also directly tied to the maximum possible speed of energy/mass displacement - which is currently bested by the photon.
lengould100
not rated yet Aug 16, 2012
So daywalk3r: You declare that gravity is a field reaching to infinite distance as an attribute of the simple existence of (a) mass, and the field travels through space along with, and at precisely the same velocity, as the mass which generates it. Where then does the supposed "graviton" fit in?
lengould100
not rated yet Aug 16, 2012
So since this gravity field "travels with the mass" at exactly the same velocity, but light takes measurable time to travel from the mass to our telescope, shouldn't the gravity vector detector apparently point in a direction measurably ahead of the telescope observing the light from the object, which takes measurable time to travel from the object to us?
lengould100
5 / 5 (2) Aug 16, 2012
Ok, sorry people, I should do my own searching for answers. Turns out Wikipedia (who knew it was getting that good lol?) has some pretty good information. Gravitons are probably massless spin 2 bosons which propagate at a speed of "C or less", possibly closed-loop strings, possibly not connected to any brane. Probably impossible to ever detect individually.

Probably meaning that in my thought experiment, the gravity vector detector and the telescope should point in precisely the same direction. Kudos.

http://en.wikiped...Graviton

lengould100
not rated yet Aug 16, 2012
antialias_physorg
not rated yet Aug 16, 2012
If you want to keep abreast of any findings in this field then check out the LIGO experiment.
http://en.wikiped...rvations
They were specifically set up to look for gravity waves (and if the speed of gravity is other than the speed of ligt they should be able to measure it.)
daywalk3r
3.9 / 5 (11) Aug 16, 2012
You declare that gravity is a field reaching to infinite distance as an attribute of the simple existence of (a) mass,and the field travels through space along with,and at precisely the same velocity,as the mass which generates it.
Not exactly..

"existence of (a) mass" - has little to do with it.
Mass is rather an effect. ENERGY per unit volume of space is what matters here (eg. energy density). "Matter" being just alot of energy confined in a small volume of space.

And gravity is not exactly a field, but rather the "effect of gravity" is proportional to something that can be described as a field (energy density of spacetime, and its gradient).

AND...

To change the energy density of any given volume of space, it requires energy to be DISPLACED from point A to point B - and as far as we to date know (and have observational evidence for) - the maximum speed of displacement of energy equals that of a photon (eg. the speed of light).

So "the field" also "travels" (changes) at c.
daywalk3r
3.9 / 5 (11) Aug 16, 2012
Where then does the supposed "graviton" fit in?
The "graviton" is just a resonance of the interaction mechanism of the field.

If the "speed" of gravity was infinite, then there would be no such resonance (as its frequency would also be infinite).

So insta-gravity = no graviton (pretty much).

So since this gravity field "travels with the mass" at exactly the same velocity
The field does not "travel" - it changes.
And this change happens at the speed of displacement of energy, which by current knowledge and observations, equals to (or is less than) c. As allready explained in my previous post.

However, if the "speed" of gravity was at some point proven to deviate from c, it would easily be a candidate for one of the greatest discoveries of mankind EVER.

But I guess we will (at the very least) have to wait for Advanced LIGO and/or eLISA to even approach the possibility of such a discovery.

PS: AA, I'm currious.. Did you get the "FTL thing" in the end?

Cheers.