Higgs boson discovery confirmation

[Larry Borgia]

Ok, this is going to be a little rremoved from the OP's question but it's something that's been bugging me.

We say that there are a variety of explanations--many worlds, collapsing waves etc--and that it doesn't matter which one is true if they are mathematically equivalent. At least it doesn't matter to physicists. But still doesn't one explanation have to be true? If we take the many worlds explanation seriously, doesn't that mean that there are many worlds? And either there are many worlds or there aren't. If a quantum event creates a new world, shouldn't that new world actually (somehow) exist? Or am I being too naive?

[Exapno Mapcase]

Originally Posted by Grey

I'm not sure that's what Greene means. Basically, and someone straighten me out, there are multiple approaches to achieving the same results depending on what mathematical approach you take in M theory. Similar to how matrix and wave mechanics can be used to reach the same result in quantum mechanics and so we wind up with transformation theory and Hilbert space. But just because 2 different mathematical formulations gives you the same answer doesn't mean you get 2 universes.


Note though, I may have misunderstood Greene's point.

That's not I how read the book. He describes nine fundamentally different types of multiverses. And anywhere from 0 to 9 of these might actually be physically real.

[Exapno Mapcase]

Originally Posted by Larry Borgia

Ok, this is going to be a little rremoved from the OP's question but it's something that's been bugging me.

We say that there are a variety of explanations--many worlds, collapsing waves etc--and that it doesn't matter which one is true if they are mathematically equivalent. At least it doesn't matter to physicists. But still doesn't one explanation have to be true? If we take the many worlds explanation seriously, doesn't that mean that there are many worlds? And either there are many worlds or there aren't. If a quantum event creates a new world, shouldn't that new world actually (somehow) exist? Or am I being too naive?

The problem is that using "exist" to describe something in a forever inaccessible other universe is depending on everyday words to stretch farther than is allowed. Philosophers have enough problems trying to define "truth," "reality," and "existence" in our touchable physical universe. Are mathematical constructs "real"? Does information "exist"? If there are nine distinct types of multiverses is any one more real than any of the others or are they all equal in some sense?

You're getting into territory that might be described as the singularity of words. They break down at this point and can't be defined.

[Larry Borgia]

Originally Posted by Exapno Mapcase

The problem is that using "exist" to describe something in a forever inaccessible other universe is depending on everyday words to stretch farther than is allowed. Philosophers have enough problems trying to define "truth," "reality," and "existence" in our touchable physical universe. Are mathematical constructs "real"? Does information "exist"? If there are nine distinct types of multiverses is any one more real than any of the others or are they all equal in some sense?

You're getting into territory that might be described as the singularity of words. They break down at this point and can't be defined.

I mean exists in the same way our world exists. Somewhere there is a world that is identical to our world except in our world a certain electron emitted a photon at time t and in that world it didn't. Or there isn't. But there either is or there isn't.

Math is fine, pure math is fine, but physics has to relate to something. Otherwise it's not science but rather "making things up," a very expensive glass bead game.

[NojNoj]

Originally Posted by Exapno Mapcase

If there are nine distinct types of multiverses is any one more real than any of the others or are they all equal in some sense?

You're getting into territory that might be described as the singularity of words. They break down at this point and can't be defined.

I think you can make distinctions between theories predicting something "real," but completely outside our realm of being able to test or visualize, vs. theories that are so abstract, they loose any link with what we know and experience.

My understanding of some of Greene's earlier ideas, as one multiverse idea is 3-dimensional "branes" floating around in some n-dimensional space. That all feels fine and real, even though we'll never observe it directly.

I've never heard any explanation of "Multiple Worlds..." of where the worlds are. Are these newly formed spacial dimension? Some new time axis? what?

[borschevsky]

I have a question too .

From what I understand, the theory has predicted that if the Higgs exists, it should decay in a certain way, so that type of decay should be more common than would otherwise be expected. But this Higgs decay will be relatively uncommon, so the difference you'd see in "Higgs" and "Non-Higgs" universes is very small. So it's been necessary to run an enormous number of trials to become confident that this extra bit is really there, and isn't just some statistical noise.

I guess my question is: what exactly is the event that's being counted in these trials? Is it literally the exact same experiment run an enormous number of times? If so, is the result of each trial just one of these quantum probabilistic things where occasionally you get a Higgs boson, more commonly you get something else that decays like the Higgs, and sometimes you get something else altogether?

[NojNoj]

Originally Posted by Exapno Mapcase

I keep hearing that many-worlds is becoming the preferred interpretation among physicists, because of the way the math works.

I'm having trouble squaring that idea with what's been stated that many-worlds makes no testable prediction, no new explanatory power, and no new methods for solving wave, or other, equations. So how can the math be "better" in any way?

[Grey]

Originally Posted by Exapno Mapcase

That's not I how read the book. He describes nine fundamentally different types of multiverses. And anywhere from 0 to 9 of these might actually be physically real.

I think I'm confusing The Elegant Universe with this new book. So he's describing different valid results based on the math? Analogous with -2 and +2 as roots of 4?

[Larry Borgia]

Originally Posted by Larry Borgia

I mean exists in the same way our world exists. Somewhere there is a world that is identical to our world except in our world a certain electron emitted a photon at time t and in that world it didn't. Or there isn't. But there either is or there isn't.

Math is fine, pure math is fine, but physics has to relate to something. Otherwise it's not science but rather "making things up," a very expensive glass bead game.

Also, while I'm just a dumbass on the internet, Lee Smolin is not, and in his book The trouble with Physics he called foundational problems in QM one of the five big unsolved problems in physics, so he at least seems to feel it's a real problem, not something to be handwaved away with "at least the math works."

[cmyk]

Originally Posted by Der Trihs

The real question is, what happens if you put Gods in an accelerator and collide them at high speed?



Besides really annoying them, that is.

Can God make a particle with which He, Himself, cannot collide?

[iamnotbatman]

Originally Posted by NojNoj

I understand that it may be intellectually pleasing to work with an interpretation that simply corresponds to what the math is telling you, but underneath, it seems to have the same ugliness as "collapsing a wave form."

It doesn't

Originally Posted by NojNoj

How does it fit with the rest of what we know of the universe (i.e., where are these other worlds, once an event is observed?) How does it fit in any way with what we observe? In other words, how is different than interpreting Newton's equations as being driven by invisible dragons being the ones creating force?

It fits with what we observe to the same extent that any other interpretation of QM fits with what we observe. When you are faced with multiple explanations of the same phenomena which make the same testable predictions, you have to use Occam's razor to decide which explanation is worth aligning yourself with. In this case, collapse of the wave function is more similar to invisible dragons, in that it is an unnecessary and overly complicated explanation.

Originally Posted by NojNoj

And perhaps more importantly, MWI has been around longer than String Theory and you're saying it hasn't resulted in any testable predictions or unique methods. At some point you have to see that others might see this as sterile intellectualizing, no matter how beautiful...

It is not meant to nor does it promise to provide any testable predictions. It is merely an ontology. Not a whole lot of time has been spent on it. It is simply an observation that is "obvious" to some, and "silly" to the sadly misinformed

Originally Posted by NojNoj

And also I'm not sure I agree that this is a case of boldly "trusting the math." My understanding is that Einstein trusted the math when it said speed of light is constant, and doing so resulted in special relativity. Then he trusted the math that said gravity was like angular acceleration and out came general relativity. So, Einstein trusted math that corresponded to phenomenon people could observe and measure. In contrast, [...]

It sounds like you agree this is a case of trusting the math, you just don't like the fact that the math implies something which is unfalsifiable.

Originally Posted by NojNoj

[...] some subset of theoretical physicists are "trusting" (I would say interpreting) the wave equation to say there are many potential outcomes (of which we somehow only observe one), and that results in....(?)

There are many potential outcomes in the ordinary vanilla quantum mechanics that everybody agrees is correct. The non-MWI camp would argue that the other outcomes predicted by the Schrodinger equation magically disappear in some ill-understood process corresponding to no known law of physics, under circumstances that are ill-understood, and for which no ontology has ever been found. Many years of human life have been spent trying to understand what this process might be. The MWI camp simply suggests that the other outcomes live-on. We simply do not observe them due to decoherence. To me this provides a far simpler explanation, and a very satisfying ontology. It is also possible that, since this explanation seems so much more reasonable, that it could help provide a foundation for future theories which themselves may very well be falsifiable.

Now, you may think this is all mental masturbation, but most of us (at least those not interested in philosophy) don't obsess about it. It's no big deal. It is simply nice to have a satisfying ontology at the back of one's mind, in the same way that when you aren't looking up at the sky you assume the moon is still orbiting the earth, even though you cannot prove it without looking at it. Of course, we use Occam's razor to provide the most useful and agreeable ontology; that even when we aren't looking, the moon orbits the earth. It's the same reason most of us are not solipsistic. The MWI is no more mental masturbation that many of the things you take for granted about the world.

[Inner Stickler]

Originally Posted by iamnotbatman

Higgs? Hugs!

Relevant

[iamnotbatman]

Originally Posted by borschevsky

I guess my question is: what exactly is the event that's being counted in these trials? Is it literally the exact same experiment run an enormous number of times? If so, is the result of each trial just one of these quantum probabilistic things where occasionally you get a Higgs boson, more commonly you get something else that decays like the Higgs, and sometimes you get something else altogether?

Your description is exactly correct!

[NojNoj]

Originally Posted by iamnotbatman

The MWI is no more mental masturbation that many of the things you take for granted about the world.

First off, extra points for calling me out my using the euphamism of "sterile intellectualizing" (well, it does sound more polite than "mental masterbation").

Everything you say makes perfect sense, though I think it'd be better if people clearly labeled a theory like MWI as "philosophy" and not physics to avoid confusion.

The one sticking point is how is MWI less-ugly? Doesn't that mean it does offer some useful method? Without going into hard-to-explain details, is there any way to convey what you find appealing about the MWI perspective from a "working phycisist" perspective?

[iamnotbatman]

Originally Posted by Larry Borgia

Ok, this is going to be a little rremoved from the OP's question but it's something that's been bugging me.

We say that there are a variety of explanations--many worlds, collapsing waves etc--and that it doesn't matter which one is true if they are mathematically equivalent. At least it doesn't matter to physicists. But still doesn't one explanation have to be true? If we take the many worlds explanation seriously, doesn't that mean that there are many worlds? And either there are many worlds or there aren't. If a quantum event creates a new world, shouldn't that new world actually (somehow) exist? Or am I being too naive?

If there are many worlds, they exist! We wouldn't say there are many worlds if we didn't mean it!

[Larry Borgia]

Originally Posted by iamnotbatman

If there are many worlds, they exist! We wouldn't say there are many worlds if we didn't mean it!

I don't know what this means.

[NojNoj]

Originally Posted by Larry Borgia

I don't know what this means.

Yes, I think we've arrived at the key sticking point.

MWI doesn't seem to elegantly explain observed phenomon--where do the additional possibilities live on? Please give us something (e.g., new time dimension), or we can no longer tolerate parasitic string theorists suckling at the teet of the state..

[borschevsky]

Originally Posted by iamnotbatman

Your description is exactly correct!

Thanks!

[iamnotbatman]

Originally Posted by NojNoj

Everything you say makes perfect sense, though I think it'd be better if people clearly labeled a theory like MWI as "philosophy" and not physics to avoid confusion.

When it comes to the popularizers, they do go overboard in describing things that are more philosophical that physical. However while the MWI is indeed "philosophy of physics", many would think that it is unfair to draw extra attention to this fact just because it seems bizarre to you. There are many, many bits of ontology that are technically speaking "philosophy" scattered throughout our physics education, and even built into our theories. Most of them you wouldn't question because they are "obvious" to you, so you are applying a double-standard here. And these bits of philosophy are valuable! It's very useful to be able to visualize things, and have some underlying picture of reality to fall back on when trying to work out the solution to a problem. As you know from your description of Einstein's work, a physicist's intuition about the nature of reality has shown time and time again to be invaluable in moving science forward. An while this intuition is guided by what is technically philosophy, it is in practice very much a part of pragmatic physics. And in moving physics forward, it helps to be able to try to understand "what is really going on." How else are we to make that "leap" to the next big theory? But when you have mathematics that has many possible interpretations as to "what is really going on" you have to make a mental choice in order to move forward. Typically "beauty" is involved, and of course Occam's razor. This is, whether you like it or not, a valuable part of practicing physics that is technically philosophy.

To sum up the above paragraph, it is unfair to characterize MWI as philosophy (not that there is anything wrong with philosophy) unless you also characterize the copenhagen interpretation as equally philosophy. If you are going to learn quantum mechanics, it is normal (unless you are an android or are autistic or something) to adopt some mental description of what is actually happening, something that corresponds to the math and is able to give you physical intuition. You have to make some choice. That choice is philosophy, whether you end up on the side of the MWI, copenhagen, or anything else. So it is unfair to pick out the MWI as somehow a special offender. Your real issue with it is that you think it is strange and unnecessarily extravagant. In my opinion this is because you do not understand it well enough.

Originally Posted by NojNoj

The one sticking point is how is MWI less-ugly? Doesn't that mean it does offer some useful method? Without going into hard-to-explain details, is there any way to convey what you find appealing about the MWI perspective from a "working phycisist" perspective?

It offers no useful method. It is less ugly because it makes fewer assumptions. The best I can do is to offer a bit of history and my comment on it.

In the 1920's it was found that the evolution of particles can be described by a simple differential equation (the Schrodinger equation). This is simple and beautiful. A given particle is described by a wave, which can be many places at once. This wave undulates and evolves according the the Schrodinger equation. But when we make a measurement, we don't see a wave, we see a 'blip'. Almost 100 years later today, as far as we can tell, the Schrodinger equation is correct whenever we are not looking. But still, no one knows why or how or what causes the Schrodinger equation to suddenly stop working whenever we make a measurement. Clearly something really crazy is going on! Some complicated physics that causes the wave to "collapse" whenever we try to look at it! But no one has ever figured out any physical interaction that could cause a collapse, because every physical interaction is correctly described by the Schrodinger equation! Except when we are looking! But we are just made up of particles. Our bodies follow the Schrodinger equation too! So there should be no such thing as a special kind of measurement we can make, that would cause a wave function to collapse. How can we cause the wave function to collapse by making a measurement, if we are just made up of particles, and the Schrodinger equation is always correct for particles and doesn't cause any collapse? Clearly there is a fundamental logical inconsistency in trying to think of the wave function as collapsing. It is a total mess, requires a world-view that is akin to the magical dragons you have mentioned, and some new physical mechanism causing wave function collapse which is ill-defined (what is a measurement?) and self-contradictory. This is why people have tried to use consciousness to explain wave function collapse. This is the ugly mess people get in when they are taught that the wave function actually collapses!

The far simpler explanation is that the Schrodinger equation is always correct. There is no such thing as wave function collapse. There is just the appearance of wave-function collapse due to anthropic self-selection and decoherence. This is a fancy way of saying that there is a large, continuous wave function, and you take that wave function seriously. You don't postulate "many worlds" so much as you simply assume the wave function exists and evolves according to the Schrodinger equation. The "interpretation" comes in when you notice that the wave function is a sum of many little pieces (like when you integrate a curve you can break it into pieces that you sum up). Because the Schrodinger equation is linear, the evolution of the whole wave function is equivalent to the simultaneous evolution of an infinite number of slightly different "pieces" that make up the wave function. One of those pieces is "you". Another piece is a slightly different version of "you". Each version of "you" interacts with pieces of the wave function of the surrounding universe, and becomes entangled with it (interactions mean that conservation laws start forbidding mutually incompatible alternate possibilities). As each version of "you" gets more and more entangled with parts of other waves functions, it becomes impossible for "you v1" to interact with "you v2" because "you v1" has gone and interacted in a way that is logically incompatible with "you v2". In other words, "you v1" and "you v2" are in "separate universes" practically speaking, although you are both still part of a larger wave function still evolving according to the Schrodinger equation.

It may sound complicated, and it is difficult to explain, and yes, deducing all of this may seem complicated, and some of the deductions may seem bizarre to you, but the underlying idea is very simple and coherent, and not bizarre at all. The universe consists of a wave function that evolves according the Schrodinger equation. Full stop.

[Exapno Mapcase]

Originally Posted by NojNoj

Yes, I think we've arrived at the key sticking point.

MWI doesn't seem to elegantly explain observed phenomon--where do the additional possibilities live on? Please give us something (e.g., new time dimension), or we can no longer tolerate parasitic string theorists suckling at the teet of the state..

Multiverse means multiple universes. These are universes separate from our own. They have separate existence. They do not live in our time or space or perhaps even our physics. They are separate. And they all fall out of the math so they are physics. They are not some magic words that physicists dreamed up to be cute. They are as mathematical as the laws of thermodynamics. Where do they live, BTW?

You problem is actually with the philosophy, not with the physics. You're telling physicists that since you can't understand the implications of the math in words therefore their math can't be meaningful. I fully sympathasize with not understanding, but that can't become the basis for "I'm right, you're wrong."

On preview: written before iamnotbatman's last post.

[Pasta]

Originally Posted by borschevsky

I guess my question is: what exactly is the event that's being counted in these trials?

The Large Hadron Collider at CERN sends clumps of protons around a 17-mile circular path in both directions. When each clump of protons approaches each experiment's location, the protons are deflected so as to cross paths exactly in the middle of the detector (CMS shown in the link).

Each proton that runs into a proton heading in the other direction is an independent trial. Protons are made up of quarks and the gluons that bind them together, so each trial is really a collision of a whole mess of particles at once, and the result is generally rather messy. The most interesting cases are where a single quark or gluon from each proton takes the brunt of the collision, and these two particles interact to produce a heavier particle. This heavier particle is usually an unstable one that decays almost immediately, and the decay products are detected (along with any spray from the "spectator" pieces of the protons) by the surrounding detector elements.

The production of a simple Standard Model Higgs boson at the LHC should happen in about 1-billionth of the proton collisions. The fact that it happens rarely is annoying enough, but it's not the real issue. The real issue is that for every Higgs you produce, there have been a billion other collision producing other things that could mimic the Higgs' decay pattern. The detectors and the analyses are designed to minimize this identification confusion, but in the end, almost all of the decays that look just like a Higgs decay are in fact not a Higgs decay. (The jargon is that these are "background events".) As you say, you need to build up a very large number of trials to notice the tiny extra decays due to the presence of the occasional Higgs particle on top of all the uninteresting background.

Nature throws us a bone, though. If you had to just count Higgs-like decays and try to tell if you got more than you "should", then we'd be miles from discovery. However, if you can measure the momenta of all the decay products, then you can calculate the mass of the particle that decayed into them. You can then look to see not just that you got extra Higgs-like decays but that these extra ones pile up at a particular calculated mass. This is very powerful is demonstrating that a new particle (and not a statistical fluctuation) is the source of the extra decays.

Here are the CMS and ATLAS plots that show the number of Higgs-like decays they see as a function of the mass they calculate for the parent particle using the observed decay products. Of note is that the background events lead to a wide smear of calculated masses. This isn't because it's a bunch of differently massed particles producing them but rather that the daughter particles detected in each background case are usually an incomplete set, which causes you to calculate a sort of random answer for the mass. The little bump of extra events you can see in the plot tells you both that there is something extra happening and what the mass of the parent particle is. And the figure shows that CMS and ATLAS see completely consistent values for the mass of this new particle.

These figures are showing only the cases where the Higgs was seen decaying into two photons. This is the easiest decay mode for removing background events since there isn't as much that can mimic it. (Although as the plots show, there's still plenty of background!) But unfortunately, it's also a very unlikely way for the Higgs to decay. Take a look at this plot. It shows all the different ways a Standard Model Higgs can decay (colored lines) and the fraction of time it would decay to each (vertical axis), as a function of the mass of the Higgs. We now know the mass to be around 125 GeV, so we can read off how often it should decay to, say, a charm/anticharm quark pair (labeled "cc", with a line over one of the c's) or anything else. The two-photon case is labeled "gamma-gamma" and is way at the bottom. At 125 GeV, it is only 0.2% of the decays. But, it's still the easiest one to use since all the others have tons of unrelated processes that mimic them, making them very hard needles to find in their respective haystacks.

Each search for one of these decay channels is an independent effort requiring somewhat different approaches. And, while the two-photon case is the most powerful, the others do help (with Z*Z* being the next best), and so the experiments combine the statistical power from each to get the best final answer possible. Also, a key question is whether the observed rate of decay into each of these different daughter particles follows the pattern expected for a Standard Model Higgs. So far it is all consistent, but the statistical power is very low in most of the decay modes so it is too early to say for sure.

[NojNoj]

Originally Posted by Exapno Mapcase

You're telling physicists that since you can't understand the implications of the math in words therefore their math can't be meaningful.

First, let's be clear again that we all appreciate "iamnotbatman's" incredibly thoughtful and lucid posts (I have some ideas for a book I think they should write, but another thread...) It's not trying to prove anyone wrong...

To me the discussion is what constitutes fruitful scientific work. No one can really understand a lot of things about physics (time dilation, what's a probability wave exactly, what does it mean to bend space), but we accept them because they "fit" with our basic conception of the world (e.g., I can sort of imagine that as you approach speed of light, you increasingly enter a different realm).

MWI, to me, doesn't do that. Main sticking point is I can accept probability waves when talking about a subatomic particle, but not in larger scale systems. We can observe probabilistic effects in subatomic particles, but not in larger scale systems.

So, again, where are the aspects of the wave equation that live on, after a measurement is made? (Before the measurement, no problem that they exist, since we've observed that that sort of weirdness goes on in the subatomic realm. Not so in macroscopic....)

I'm not so bothered by the philisophical inconsistencies of the Copehagen Interpretation because they accord with experiment, and they seem no less arbitrary as why particles have certain charges, why we live in a world with 4 forces and not 42, etc.

[Rachellelogram]

Originally Posted by iamnotbatman

Higgs? Hugs!

I would support the hugtrino or hugton.

[iamnotbatman]

Originally Posted by NojNoj

So, again, where are the aspects of the wave equation that live on, after a measurement is made?

They exist, but there is no sense in asking "where". That's a category mistake , like asking what is the sound of the color red. We can describe them mathematically as continuing to exist and evolving along the same position and time coordinates used before the measurement, but they can no longer interact with us, and therefore we cannot measure them.

Originally Posted by NojNoj

I'm not so bothered by the philisophical inconsistencies of the Copehagen Interpretation because they accord with experiment, and they seem no less arbitrary as why particles have certain charges, why we live in a world with 4 forces and not 42, etc.

The MWI accords with experiment as well. It is predictively equivalent to the Copenhagen interpretation. I have argued that the MWI is less arbitrary than the Copenhagen interpretation, and that the Copenhagen interpretation is internally inconsistent. The charges etc of particles seem arbitrary, but if we came up with a theory that post-dicted those values with less arbitrariness, we would hopefully value it more than the old theory.

[iamnotbatman]

Originally Posted by rachelellogram

I would support the hugtrino or hugton.

I like 'hugtron'

[NojNoj]

Originally Posted by iamnotbatman

We can describe them mathematically as continuing to exist and evolving along the same position and time coordinates used before the measurement, but they can no longer interact with us, and therefore we cannot measure them..

Thanks, that's what I was looking for and now it makes sense

[borschevsky]

I have to say, this message board is really great sometimes.

Originally Posted by Pasta

Nature throws us a bone, though. If you had to just count Higgs-like decays and try to tell if you got more than you "should", then we'd be miles from discovery. However, if you can measure the momenta of all the decay products, then you can calculate the mass of the particle that decayed into them. You can then look to see not just that you got extra Higgs-like decays but that these extra ones pile up at a particular calculated mass. This is very powerful is demonstrating that a new particle (and not a statistical fluctuation) is the source of the extra decays.

Here are the CMS and ATLAS plots that show the number of Higgs-like decays they see as a function of the mass they calculate for the parent particle using the observed decay products. Of note is that the background events lead to a wide smear of calculated masses. This isn't because it's a bunch of differently massed particles producing them but rather that the daughter particles detected in each background case are usually an incomplete set, which causes you to calculate a sort of random answer for the mass. The little bump of extra events you can see in the plot tells you both that there is something extra happening and what the mass of the parent particle is. And the figure shows that CMS and ATLAS see completely consistent values for the mass of this new particle.

Thanks for this explanation, I feel like I have a decent handle on things now. If I might ask another question, what is it that causes the Higgs boson to appear in the few cases where it does? That is, if we had an extreme level of control over the conditions of the collisions, could we always produce a Higgs boson? Or is this one-in-a-billion rate just a property of the universe, something like a half-life?

[Pasta]

Originally Posted by borschevsky

What is it that causes the Higgs boson to appear in the few cases where it does? That is, if we had an extreme level of control over the conditions of the collisions, could we always produce a Higgs boson? Or is this one-in-a-billion rate just a property of the universe, something like a half-life?

It's random. In the same way that decay products are quantum mechanically random, so too are production products. Indeed, the same formalism that one uses to calculate the probabilities of particle X decaying into a, b, or c is also used to calculate the probabilities of a collision producing X, Y, or Z.

(A side point: some of the production randomness at the LHC is due to the fact that complex objects (protons) are being collided, and you could perhaps consider that an experimentally improvable situation. But, you can't have isolated quarks or gluons, so you can't have a pure quark or gluon collider. Thus, you are stuck with messy protons, which have many uninteresting ways of interacting. There is design work underway for a next-generation electron-positron collider that would provide a much cleaner environment for studying detailed properties of the Higgs or anything else that may be discovered at the LHC. But even though elementary particles would be collided there, production is still probabilistic. At a 500-GeV e⁺e^- collider, a Higgs would be produced in about one collision out of every hundred.)

[NojNoj]

@iamnotbatman If you had any more patience, I had one more clarifying question on "Many Worlds"

Just wondering if there is not an experiment that could be done to test one aspect of the theory. My understanding of MWI as you described it is (and please bear with me if I get terminology wrong): if a subatomic particle that has two states ("up" and "down" let's say) collides with an aircraft carrier we're standing on that measures the particle in the "up" state, then there is also a system consisting of the aircraft carrier and the particle in the "down" state that continues existing in the same location and time as the aircraft carrier we're on (but which we can't observe).

So, one might wonder why that aircraft carrier is not detectable because of its effects on gravity, etc., and I assume the answer is the same reason that all the possible states of an "undetermined" subatomic particle don't have effects on gravity. So, to test the possibility of both states of the aircraft carrier existing in the same place, could you run an experiment where you shoot millions of paths of "undetermined" particles so that they intersect (i.e., occupy the same time and place), and see whether the results of the experiment are equivalent to if there were no intersections? (Because, if there were any interference between the particle paths, wouldn't that say you can't have different wave equations/aircraft carriers occupying the same space?)

[NojNoj]

Re: Higgs Boson Humor

Apropos of this discussion, here's http://iowahawk.typepad.com/iowahawk...rts-taxon.htmlsome theoretical physics satire (definitely from a somewhat right-wing perspective, but I'm a lefty and find it very funny):

[Half Man Half Wit]

Originally Posted by iamnotbatman

I like 'hugtron'

So those LHC doomsday predictions might come true after all...

[HMS Irruncible]

So again to try the patience, just another clarifying question.

Am I right in understanding that the Higgs boson doesn't normally exist in nature, but producing it was the best (maybe only) method of proving that the Higgs field does exist in nature?

[Leo Bloom]

On the profession, which has now entered the public consciousness since, well, forever, and some basics questions.

If you showed the CMS and ATLAS plots to any able particle physicist, would he/she shout "eureka, praise the lord," etc., or is Higgs stuff more specialized?

In those plots of decay paths, did figuring _each_ path take lifetimes of research and ultimately testing? And rate a Nobel or two?

Do people know--or what results are people entertaining--of what happens when you keep smashing protons at higher and higher speeds?

Why were protons chosen?

[aldiboronti]

What wonderful responses to my original question! Is it any wonder that I love this message board? That comment by iamnotbatman on Schrodinger's equation upthread just blew me away. And the religious types talk of scientists taking the mystery and wonder out of the universe! The reality that lies at the root of ourselves and the whole universe is proving to be orders of magnitude more awesome, wondrous, breathtaking, staggering than a whole host of creation myths.

By the way I suppose one could date the beginning of science to the first caveman curiously breaking something to pieces to see what it was made of. And isn't that what we're still doing with our super colliders? With a teeny bit more force though.

[iamnotbatman]

Originally Posted by NojNoj

@iamnotbatman If you had any more patience, I had one more clarifying question on "Many Worlds"

Just wondering if there is not an experiment that could be done to test one aspect of the theory. My understanding of MWI as you described it is (and please bear with me if I get terminology wrong): if a subatomic particle that has two states ("up" and "down" let's say) collides with an aircraft carrier we're standing on that measures the particle in the "up" state, then there is also a system consisting of the aircraft carrier and the particle in the "down" state that continues existing in the same location and time as the aircraft carrier we're on (but which we can't observe).

So, one might wonder why that aircraft carrier is not detectable because of its effects on gravity, etc., and I assume the answer is the same reason that all the possible states of an "undetermined" subatomic particle don't have effects on gravity.

The reason goes back to quantum mechanics, regardless of which interpretation you subscribe to. When a particle is in a superposition of states, those states do not interact with each other as though they are separate particles; they are states representing one particle, not multiple different particles. For example, forget gravity (because it is so weak, let's discuss something more dramatic), let's talk about a charged particle. A charged particle can become in a quantum superposition so that its wave function is spread a bit out in space. But if you treated each part of that wave function as a separate particle that can interact with the other parts of the wave function, then they would all fly apart, exploding at near the speed of light. Because charged particles repel, very strongly. So when a particle is in a quantum superposition, you don't treat it as a bunch of separate particles; the wave function represents one particle only, just different possible states for the one particle to be in. In the MWI each of these possible states are not just possible, but real. But they don't interact with each other. In the Copenhagen interpretation each possible state is only possible, but not real until measurement. But still, each possible state does not interact with the others.

Now, when I say "does not interact", I should clarify one thing. The states do "interact" in the sense that they are described by a wave function that, when added together, can interfere constructively or destructively, the same way light can interfere constructively or destructively. But the states are not actually interacting, they are just adding linearly on top of each other, which mathematically can have the effect of causing interference. This is one of the main sources of interesting quantum effects, again regardless of which philosophical interpretation you subscribe to.

Originally Posted by NojNoj

So, to test the possibility of both states of the aircraft carrier existing in the same place, could you run an experiment where you shoot millions of paths of "undetermined" particles so that they intersect (i.e., occupy the same time and place), and see whether the results of the experiment are equivalent to if there were no intersections? (Because, if there were any interference between the particle paths, wouldn't that say you can't have different wave equations/aircraft carriers occupying the same space?)

In spirit you seem to be describing an experiment that gets to the heart of quantum mechanics (again, regardless of any philosophical interpretation). It is called the double-slit experiment. It means that a single particle can "interfere with itself" because it is described by a wave (note again that there is no interaction, gravitational or otherwise). Again this is described within ordinary quantum mechanics, and is true in the MWI or the Copenhagen interpretation.

[iamnotbatman]

Originally Posted by HMS Irruncible

So again to try the patience, just another clarifying question.

Am I right in understanding that the Higgs boson doesn't normally exist in nature, but producing it was the best (maybe only) method of proving that the Higgs field does exist in nature?

You are right.

[iamnotbatman]

Originally Posted by Leo Bloom

On the profession, which has now entered the public consciousness since, well, forever, and some basics questions.

If you showed the CMS and ATLAS plots to any able particle physicist, would he/she shout "eureka, praise the lord," etc., or is Higgs stuff more specialized?

If they were competent, and if the plots had well labelled axes and titles.

Originally Posted by Leo Bloom

In those plots of decay paths, did figuring _each_ path take lifetimes of research and ultimately testing? And rate a Nobel or two?

Yes. A tremendous of both experimental and theoretical work went into being able to make those plots. And yes, nobels were won for a number of decay channels in there, for example the discovery of the W and Z bosons.

Originally Posted by Leo Bloom

Do people know--or what results are people entertaining--of what happens when you keep smashing protons at higher and higher speeds?

No one knows, but that's why we build bigger particle accelerators, so we can find out. There may be new particles that are so massive they can only be discovered with higher energy particle beams.

Originally Posted by Leo Bloom

Why were protons chosen?

Because they are charged and heavy. Charged allows us to accelerate them using electric fields. Heavy allows us to move them along a circular path without them radiating away too much of their energy.

[NojNoj]

@iamnotbatman

Thanks. I guess by bringing an aircraft into the mix, I'm proposing a variation of Shroedinger's Cat. If you set up a detector so that if an "up" particle hit it, the aircraft carrier disintegrated, then it seems in the MWI interpretation, you have superimposed states where in one the aircraft carrier is still there and its gravity is bending space-time, and another where there's no more aircraft carrier and so space-time is not bent.

So, space itself seems to have to become part of the wave equation in MWI. Hope that clarifies where I'm still mystified...

[iamnotbatman]

Originally Posted by NojNoj

@iamnotbatman

Thanks. I guess by bringing an aircraft into the mix, I'm proposing a variation of Shroedinger's Cat. If you set up a detector so that if an "up" particle hit it, the aircraft carrier disintegrated, then it seems in the MWI interpretation, you have superimposed states where in one the aircraft carrier is still there and its gravity is bending space-time, and another where there's no more aircraft carrier and so space-time is not bent.

So, space itself seems to have to become part of the wave equation in MWI. Hope that clarifies where I'm still mystified...

Well, if you insist on including gravity in the mix, I have to qualify anything I say with "we don't have a theory of quantum gravity yet". But yes, space itself must be part of the wave equation, if you start talking about gravitational stuff (otherwise you can ignore the fact that space is part of the wave equation, because in each "world" the space is an exact duplicate).

[Pasta]

Originally Posted by HMS Irruncible

Am I right in understanding that the Higgs boson doesn't normally exist in nature, but producing it was the best (maybe only) method of proving that the Higgs field does exist in nature?

The Higgs boson exists in nature just the same as any other unstable particle. It is created in the same sorts of collision processes that the LHC uses. You are correct in the sense that you won't find a bunch of them just sitting around somewhere, but the same can be said about almost every other particle we have a name for, so this isn't special about the Higgs.

Originally Posted by Leo Bloom

If you showed the CMS and ATLAS plots to any able particle physicist, would he/she shout "eureka, praise the lord," etc., or is Higgs stuff more specialized?

Any particle physicist worth his or her salt should have no problem interpreting and appreciating the results. A young grad student in a separate area of particle physics that hasn't gotten to the point in their career where they notice the bigger picture might have to ask a question or two, but for the Higgs even that would be the exception. (I bring grad students into it simply because a significant fraction of the people working in particle physics (or any scientific research field) at any one time are grad students.)

Obviously the deeper you dive into the specifics of how the measurements were made, the more you will get into collider physics jargon, collider detector jargon, LHC-specific jargon, analysis-specific jargon, ... But even then, a particle physicist working in another arena should have no problem understanding how pretty much any nitty-gritty part of the experiment was done if they could talk with an expert over a long lunch.

In those plots of decay paths, did figuring _each_ path take lifetimes of research and ultimately testing?

Once you specify what sort of Higgs field you are introducing into the theory, then the calculations of the decay rates are fairly routine (if cumbersome). The basic features of the curves (how they trend, where they go up or down) is qualitatively explanable without much math at all. To be sure, most particle physicists can't calculate this stuff at the drop of a hat because it's a chore and it's been done, so these calculations are generally out-sourced to those that specialize in it (in practice by using the software tools they have created). To be sure, a decent fraction of experimentalists would have some difficultly doing these calculation, but most could probably pull it off if given ample time and a particle physics library.

This all assumes we have a Standard Model in place and we're just asking "What happens if you put in a Higgs field." In actually getting to the basics of the Standard Model was a major feat of science in the last century, and numerous Nobel prizes came from all that. But, I get the impression that you are asking a more Higgs-specific question and aren't looking that far back (or further, to the first quantum mechanics and relativity work, or even the electromagnetism of the 1800's before that, ... Lots of giants' shoulders.)

Do people know--or what results are people entertaining--of what happens when you keep smashing protons at higher and higher speeds?

Nope, and the LHC is the most recent step in the "higher and higher speeds" sequence. The Standard Model has many ugly properties that point to something new happening at some not-too-much-higher energy. There are many intriguing, and generally well-motivated, theories around about new stuff that might be seen, but so far nothing new has appeared.

(There are also reasons to expect new stuff happening many orders of magnitude higher in energy, but this physics can't be accessed directly just by ramping up the energy, so one uses various indirect means.)

Why were protons chosen?

In addition to being charged and heavy, they are cheap and plentiful. The accelerator complex literally starts with a gas cylinder of hydrogen. Proton/antiproton collisions were used at the Tevatron at Fermilab, and this has some distinct engineering and analysis advantages, but making antiprotons takes a lot of resources (off all kinds: people, energy, accelerator time, raw numbers of protons, ...), and you wouldn't have been able to get anywhere near the number of collisions per second at the LHC with proton/antiproton collisions.

(One engineering challenge, as an example: to keep a proton moving around in a circle you use magnets, since charged particles are deflected when they move through a magnetic field. Positively charged particles are deflected one way, and negatively charges particles are deflected the other way. In a proton/antiproton collider, the protons are going (say) clockwise around the ring and the antiprotons are going counterclockwise, which is perfect, since it means the protons need to be deflected to the right and antiprotons to the left. The two counter-circulating beams can thus share a beam pipe and can use the same magnetic fields around the ring. In the proton/proton case, this breaks down, and you need two oppositely directed magnetic fields, one for each beam. This requires two independent beam pipes and two magnets sitting very close to one another, each producing 8.3 tesla to boot! (Pictures?) But the engineering complexity is worth it for a collision rate that is much higher than you could get with protons and antiprotons.)

[Pasta]

(Apologies for the painful number of typos in the preceding post. I was typing it in a rather non-ideal environment...)

[Leo Bloom]

Originally Posted by borschevsky

If so, is the result of each trial just one of these quantum probabilistic things where occasionally you get a Higgs boson, more commonly you get something else that decays like the Higgs, and sometimes you get something else altogether?

[Bolding mine]
I thought if it looks like a duck, quacks like duck, etc.

There are exactly similar decay paths that ”add up" in energy to other particles?

Or did they not know which decay products were the right ones, which would've made the whole endeavor trivial?

[iamnotbatman]

Originally Posted by Leo Bloom

[Bolding mine]
I thought if it looks like a duck, quacks like duck, etc.

There are exactly similar decay paths that ”add up" in energy to other particles?

Or did they not know which decay products were the right ones, which would've made the whole endeavor trivial?

For any individual case, we have no way of knowing whether the decay products are coming from a Higgs. At the end of the day we look for two photons, or four muons, etc, and there are various ways you can get two photons or four muons, which are not the Higgs. These different ways of producing the same final set of particles you are looking for are called "backgrounds." There are various backgrounds for each channel of the Higgs analysis. For example, in the channel that looks for the Higgs decaying to two photons, one of the backgrounds is the case in which a spray of hadrons is wrongly identified as a photon. Another background is when two photons are produced directly from the proton collision. Another background is when the proton collision produces various mesons and two of them decay to photons. Some of these backgrounds can be eliminated by looking carefully for other particles in each event, but many of them are "irreducible." For each of these "backgrounds" there is a distribution of invariant masses of the two photons which can be roughly theoretically predicted. When you look for the Higgs, you look for a "peak" in the invariant mass spectrum of the two photons above the expected background distribution.

[NojNoj]

Economist had a good article on Higgs. The article mentioned one theory, dubbed "technicolor" (I think) that involves Higgs particles being comprised of quarks (new kind?), held together with a new variety of strong force. (And I gathered, this was to explain away some element of precision the Stand Model predicts about some characteristic of the Higgs.)

Would anyone who's "in the trenches" of theoretical or experimental physics care to comment on how prevalent, and what the general feeling about, this theory is?

[iamnotbatman]

Originally Posted by NojNoj

Economist had a good article on Higgs. The article mentioned one theory, dubbed "technicolor" (I think) that involves Higgs particles being comprised of quarks (new kind?), held together with a new variety of strong force. (And I gathered, this was to explain away some element of precision the Stand Model predicts about some characteristic of the Higgs.)

Would anyone who's "in the trenches" of theoretical or experimental physics care to comment on how prevalent, and what the general feeling about, this theory is?

Technicolor is a possibility that is taken seriously and experimentally searched for by mainstream particle physicists. It is nowhere as popular a theory as the Higgs, but it has its adherents. But for a while now it has been nearly ruled out by experiment, and now with the new LHC data (125 GeV Higgs mass), it is almost certainly ruled out for good.

[allotrope]

You won't be able to read the article without a subscription, but the decay data on the particle announced July 4th may indicate that while it may be something similar to the Higgs, it might not be the genuine article.

The most concerning item is the fact that no decays into tau leptons have been detected (beyond background). According to the article, since leptons are fermions (which have mass), if it's not decaying into taus, it's probably not giving them mass either.

But there are also problems with other decay paths as well. For example the decay into 2 photons seems to happen far too frequently.

This is still preliminary, but there is already speculation that this particle and the Higgs itself if this isn't it, might well be a composite just like a proton or neutron. That would open up a lot of possibilities.

[iamnotbatman]

Please be aware that the "problems" you mention are not yet problems, because they are not statistically significant. The experiments have also updated their results since July 4th (see for example, here), and the not-yet-statistically-significant deviations from Standard Model behavior are starting to get smaller. But it will take a while. The tau tau channel, in particular, simply requires much more data before being able to say something meaningful. It is not unexpected that the experiments haven't observed many events above background. The photon photon channel is a bit more interesting, but it will still take another year to be sure if something funny is going on. I'm as eager as anyone else to find something new and interesting going on here, but I wouldn't start getting excited just yet.

[cmyk]

Originally Posted by Der Trihs

The real question is, what happens if you put Gods in an accelerator and collide them at high speed?



Besides really annoying them, that is.

You get the Jesus H. Christ particle — which I'm all sure we can guess what the 'H.' really stands for.