I don’t know if you’ve been following the ongoing saga of the Ivory-Billed Woodpecker. It’s been running (at least to my mind) in corners of the press since the Spring. I love the story: Some preliminary evidence was found that this bird, which was thought to be extinct, had resurfaced in Arkansas. The scientists on the quest were so happy they cried real tears, apparently. But then there was a series of counter-claims that it was a mistake, a misidentification….and so the discussion went on and on. (Drawing at right was obtained from this site.)
This morning, there was another story about the matter on NPR (I’ve heard about 5 of them on NPR so far…there are at least 9) giving an update on the matter. Several more people have been convinced by new evidence collected by several recording devices that have been left in the forests. Christopher Joyce, in the Radio Expeditions series (lovely name), does an excellent report on the new evidence in the story “Audio Evidence of Ivory-Billed Woodpecker”. (There are links there to several earlier stories on the saga.) There are fascinating highlights in the story, such as when they’re listening to a known recording of the bird, and comparing it to the recording made in the forest. You see, that’s not good enough, since the recording was made in the forest with the bird far away from the microphone. The sound is distorted by trees, leaves, distance, etc. So to do a proper comparison, they have to figure out what the known recording would be like if it had all those obstructions as well…..
Besides the fact that it is a rather lovely story for its own sake, I like it because it reminds me of the processes we go through in fields of physics, especialy Particle (or “High Energy”) Physics, and Cosmology. Most of the objects, events, and phenomena we care about are not directly accessible (and that is the biggest understatement on this blog so far). So people spend a lot of time looking for clear means of identifying what we’re looking for by indirect means. 
A clear example is the Cosmic Microwave Background (CMB). The universe is over 13 billion years old, but a lot of focus on the science of the origins, structure and fate of the universe requires knowledge of the nature the very early universe – physics back from when the universe was in its first tens or hundereds (at most) of thousands of years. Well, we can’t go back to that time, and we can’t make a universe in the lab, so instead we must listen to the echoes of that time (the CMB) using various delicate instruments such as the WMAP or Planck satellites, or the Boomerang balloon experiments. (Image above right is CMB data. Part of it makes our banner image. See a quick explanation here.) Those recordings then allow us to attempt to identify what the features of the physics of the universe were so astonishingly long ago. And people argue, just as they do in the woodpecker story.
Other examples include looking for elusive, very massive particles such as the top quark, the Higgs particle(s), and supersymmetric particles, the latter two categories still being ongoing quests. (JoAnne is our resident expert on these searches, and no doubt she’ll be talking more about this sort of thing.) In cases such as these, in laboratories such as CERN, or SLAC, or Fermilab, (see those labs’ websites for nice tours) we collide together known particles at extraordinary energies, which -because of E=mc^2- allows for the creation of all sorts of other, more massive, particles – more energy, more massive. Among those -fleetingly- will be created the particle we’re looking for. But how do we know? There’s no detector designed to look directly for this new particle. Instead, we detect the lower mass-energy particles into which it decays – of a type that we know very well (electrons, muons, etc) – and we look for the particular patterns those particles make in the detector. A particular pattern or patterns is just like the song of the woodpecker. You don’t see the woodpecker directly, you listen for its song. Same for the particles.
-cvj
August 25th, 2005 at 12:10 pm
I think I will cry real tears when we finally discover the Higgs…
August 25th, 2005 at 12:12 pm
And I’ll bawl my eyes out if they find supersymmetry….
-cvj
August 25th, 2005 at 12:23 pm
I’ll be closest to tears if England win the Ashes back.
Are future particle accelerators under threat if nothing sexy is found at LHC when it’s up (ideally the Higgs or Supersymmetry)?
August 25th, 2005 at 12:25 pm
It was nice to see the development of that story (for some reason, the Times did like three articles on it?) Almost always, supercontentious observations turn out to be mistaken, but it’s wonderful when things pan out.
August 25th, 2005 at 12:26 pm
Hi Adam…. where were you when I did a post on the Ashes a while back? Give us an update on the saga – if you’ve been following it – when you get some time….on that thread though, not here. I’d like to know how its all going, and maybe others too.
-cvj
August 25th, 2005 at 1:05 pm
Adam asked:
“Are future particle accelerators under threat if nothing sexy is found at LHC when it’s up (ideally the Higgs or Supersymmetry)?”
There is no threat regardless of what LHC discovers, because there will be NO future, more powerful particle accelerators, not even in the wildest dreams of high energy physicists.
The problem is the exponential growth of the power, magnitude, as well as complexity and cost of modern particle accelerators, as you look at the history how accelerators grow from a desktop instrument consuming no more than the electricity of a light bulb, to the currently building LHC of 27km underground tunnel, and consumes a better half of the electricity of the whole Geneva city.
What will the next generation accelerator be? 5% more energy, consuming 5% more electricity, and dig a tunnel 5% longer than 27 km? That hardly seem to be worthwhile or useful as far as research value is concerned. You need something at least 10 times more powerful to make it useful at all, and capable of exploring energy scale that LHC has not already explored.
Can you image something many times more powerful than LHC, buried in a precise circular tunnel that runs across the whole of France land, sucks up a better part of the electrocity of the whole Europe, and maybe costs a budget of more than the GDP of a sizeable Enropean country? No civilization system can sustain exponential growth like this kind.
LHC is the end of big particle accelerator experiments. Period. I could be wrong and there might be one more generation of accelerator after LHC, but definitely not more than one more generation.
Quantoken
August 25th, 2005 at 1:18 pm
Adam, I strongly suggest that you wait to hear from JoAnne for the answer to your very interesting and important question….
-cvj
August 25th, 2005 at 1:39 pm
Ashes update posted in that old thread. And yes, I’m keen to hear what JoAnne has to say on that topic.
August 25th, 2005 at 1:59 pm
Quantoken’s view is rather gloomy but, unfortunately, not very far from the truth in terms of the practical limit in building bigger and bigger particle accelerators.
First, to answer Adam’s question: yes, there is the next accelerator we’d like to build, the electron-positron Linear Collider, which will be under threat if we don’t find anything new at the LHC. The latest indications from the funding agencies are that they would like to wait for the first LHC results before they decide on the Linear Collider.
However, the Linear Collider in itself is not going to be so much a discovery machine as a study-the-properties one. If we find a new particle or particles at the LHC, we can run the Linear Collider at the appropriate energy to produce them copiously and do precision measurements of all their properties (i.e., mass, couplings, spin, parity, etc.) This would be important not only for its own sake, but also to distinguish among the different models beyond the Standard Model.
If on the other hand the LHC does not discover any new particles (and given that its discovery potential will be all the way up to 1 TeV), we will probably need to go back to the drawing board and rethink our models. Of course, such a result, albeit negative, would be exciting in its own right.
August 25th, 2005 at 5:43 pm
Gosh, there’s lots to respond to here!
Here at Snowmass, in about 45 minutes, we are having a panel discussion on `What will it take to start construction on the International Linear Collider.’ Naturally, I will post about the results. The question is a political one, i.e., what will it take for the politicians to fund the ILC. Scientifically, we know that we want the ILC no matter what the LHC finds.
To respond to Adam, I am afraid that you are correct in the sense that the ILC will not get funded if the LHC comes up empty-handed. This is very unfortunate as in that case we would need the ILC even more than ever!
It is possible that the LHC will not be able to see the Higgs if it decays in a non-standard way. There are many such models with regions of parameter space where this can happen. However, the ILC is a model independent machine and detects the Higgs no matter how it decays, even if it decays into particles which are invisible to the detector. The scenario I just described is our worst nightmare for the LHC.
However, I sincerely doubt if accelerator science will come to an end. Current acceleration techniques have hit a dead end, but there is alot of interesting research on advanced acceleration techniques (see Caolionn O’Connell over at Quantum Diaries). I am confident that the accelerator folks will come up with a feasible method of obtaining high gradients (i.e., high accelerating energy per meter) at a reasonable cost. We are talking about obtaining tens to hundreds of GeV per meter, thus making very high energy colliders feasible in the future. I should say that more efficient acceleration techniques has followed a natural progression with historical precedent. Recall that Fermi envisioned an accelerator with the circumference equal to that of the moon in order to test his theory.
Now, to respond to Anna – my goodness! The ILC IS a discovery machine – it does MUCH more than measure properties. I just gave one example above where the ILC can discover particles that the LHC cannot. In addition, there are 2 steps for discovery: 1) to discover a new particle, 2) to discover what that new particle is and what theory it originates from. The LHC is very good at doing the first step, but it simply cannot carry out the second. We need the ILC for that.
One example that has come up many times here at Snowmass is that of Supersymmetry. The main signature for supersymmetry at the LHC is missing energy – particles which do not interact with the detector, but we know were there due to energy and momentum conservation. However, that’s the main signature for a group of other theories (such as extra dimensions or Little Higgs) as well. And how do we know which theory gives rise to the missing energy if it is observed at the LHC? The answer is that it depends on what the physics actually is and what the values of the model parameters actually are. In some cases we can be lucky and have already divised clever methods of tests that work at the LHC, but most of the time there are no such tests that work. In other words, we will know that the LHC has discovered missing energy, but we won’t know whether it is Supersymmetry, extra dimensions, Little Higgs, or something else we haven’t thought of yet. This is the main crux of the physics case for the ILC.
August 25th, 2005 at 6:02 pm
Hi JoAnne,
When I said that “measuring the properties would be important in order to distinguish among the different models”, I meant exactly what you so nicely described in the last two paragraphs of your reply. I just had a narrower definition of “discovery” in mind, meaning discovery of the particle itself, whereas you imply discovery of the underlying theory. But we agree on the basis – w/o the LC we will probably not be able to tell what we will be seeing at the LHC, if we see something.
August 25th, 2005 at 9:12 pm
JoAnne said:The main signature for supersymmetry at the LHC is missing energy – particles which do not interact with the detector, but we know were there due to energy and momentum conservation. However, that’s the main signature for a group of other theories (such as extra dimensions or Little Higgs) as well. And how do we know which theory gives rise to the missing energy if it is observed at the LHC?
Do all agree this is the case that if particles were there, and are not now, that “something” has to answer this?? JoAnne, Lee Smolin, Peter Woit. Anyone for that matter?
August 25th, 2005 at 9:47 pm
Hi again JoAnne,
I realized I didn’t respond to your earlier point about the LC seeing the Higgs if the latter decays in non-standard ways. Yes of course, you will infer it from the recoil. I didn’t mean to dismiss this option altogether (I said that the LC will be not SO much a discovery machine as…), I just emphasized the main motivation for building the LC. As you also said at the end of your post, we are building the physics case for the LC mostly as the place to sort out whatever we find at the LHC (i.e., unravel the underlying theory).
I now realize that my first posting was rather dense. Sorry. See, that was my very first posting at any web blog ever.
I now know I should explain things in more detail.
August 25th, 2005 at 10:03 pm
Plato,
It’s not that the particles were there and are not now. It’s just that the particles that JoAnne was referring to do not interact with the matter of the detector, as she said. Thus, they don’t leave signatures (no tracks, no energy deposits, etc.). We infer their existence from energy and momentume conservation: the colliding beams come on one and the same axis. This means that the initial momentum of the system before the collision is all in one direction. Therefore, the final momentum of the system after the collision should also be in the same direction. If, when you add up the momenta of all the visible particles after the collision, you end up with a significant net momentum on the plane transverse to the beam axis (and after you have calibrated your detector and you are sure it is not a systematic effect), then you know that there were some particles produced that were invisible to your detector.
August 26th, 2005 at 12:05 am
Anna, you are doing fine. Don’t worry and keep writing comments!
August 26th, 2005 at 6:42 am
Thanks Anna,
then you know that there were some particles produced that were invisible to your detector.
Generalized Questions
In context of this thread started on the woodpecker and the listening for the sounds of species, I couldn’t help think of sound in this case, as events discovered, as the “Oh My God Particle.”
Would the “landscape” be relevant here as we might interpret it in Sun-Earth relation. In light of Lagrange points and how particles would make it through, from early cosmological events?
Thanks