Possible Discovery Of A New Type of Tetraquark, And Possibly Misleading Reporting Article

We have had reports of the discovery of possible tetraquarks and pentaquarks before (i.e. particles with 4 quarks and particles with 5 quarks, respectively). There is an extensive overview of the experiment and theory in this article. So the announcement out of LHCb is not that new. What is new is that this could possibly be a new type of tetraquark made up of 4 heavy quarks.

“Particles made up of four quarks are already exotic, and the one we have just discovered is the first to be made up of four heavy quarks of the same type, specifically two charm quarks and two charm antiquarks,” says the outgoing spokesperson of the LHCb collaboration, Giovanni Passaleva. “Up until now, LHCb and other experiments had only observed tetraquarks with two heavy quarks at most and none with more than two quarks of the same type.”

You may read the preprint here.

That should clear up very much of what the brouhaha is. I probably would have glanced over this had it not be the fact that I stumbled onto another news reports of this discovery, but with a different tone that could be misleading.

First of all, let's look at how CERN produced its news release. The first paragraph read like this:

The LHCb collaboration has observed a type of four-quark particle never seen before. The discovery, presented at a recent seminar at CERN and described in a paper posted today on the arXiv preprint server, is likely to be the first of a previously undiscovered class of particles.

Notice that it says "... a type of four-quark particle ...". This means that there are already other four-quark particles, and that this discover is for a new type that has not been observed before.

Now, compare that to the reporting done by two (count 'em) particle physicists on The Conversation (a place that I go to regularly) on the same discovery. Here is what they wrote:

The LHCb collaboration at CERN has announced the discovery of a new exotic particle: a so-called “tetraquark”. The paper by more than 800 authors is yet to be evaluated by other scientists in a process called “peer review”, but has been presented at a seminar. It also meets the usual statistical threshold for claiming the discovery of a new particle.

If you don't know any better, by reading the first sentence alone, you'd think that this is the first ever discovery of a tetraquark, which would be false.

Certainly, if you read the article further, you'd come across the passage that clarifies what this discovery is:

All tetraquarks and pentaquarks that have been discovered so far contain two charm quarks, which are relatively heavy, and two or three light quarks – up, down or strange. This particular configuration is indeed the easiest to discover in experiments.

But the latest tetraquark discovered by LHCb, which has been dubbed X(6900), is composed of four charm quarks. Produced in high-energy proton collisions at the Large Hadron Collider, the new tetraquark was observed via its decay into pairs of well-known particles called J/psi mesons, each made of a charm quark and a charm antiquark. This makes it particularly interesting as it is not only composed entirely of heavy quarks, but also four quarks of the same kind – making it a unique specimen to test our understanding on how quarks bind together.

So this is not the first discovery of a tetraquark, but rather a discovery of a type of tetraquark, which is what the CERN article implied.

I know I'm being picky, but I've always said that communication between scientists and the general public is extremely tedious. Often times, what you wrote is not what they understood! And once something or some impression has stuck into their heads, it is very difficult to change that. Having a misleading idea immediately imprinted at the very beginning of an article is a horrible thing to do, even if the rest of the article is accurate. At worse, the reader holds on to the original misleading idea, and at best, the reader becomes confused with conflicting understanding. In the world where a lot of people have attention deficit and all they care about are quick bites of news, the message conveyed in the very first paragraph, or even the very first line, is all that they read and get.

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CP Violation in D Meson Decay

LHCb is reporting the first evidence of CP violation in the decay of D meson.

The D⁰ meson is made of a charm quark and an up antiquark. So far, CP violation has only been observed in particles containing a strange or a bottom quark. These observations have confirmed the pattern of CP violation described in the Standard Model by the so-called Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix, which characterises how quarks of different types transform into each other via weak interactions. The deep origin of the CKM matrix, and the quest for additional sources and manifestations of CP violation, are among the big open questions of particle physics. The discovery of CP violation in the D⁰ meson is the first evidence of this asymmetry for the charm quark, adding new elements to the exploration of these questions.

If confirmed, this will be another meson that has exhibited such CP violation, and adds to the argument that such symmetry violation could be the source of our matter-antimatter asymmetry in this universe.

CP violation is an essential feature of our universe, necessary to induce the processes that, following the Big Bang, established the abundance of matter over antimatter that we observe in the present-day universe. The size of CP violation observed so far in Standard Model interactions, however, is too small to account for the present-day matter–antimatter imbalance, suggesting the existence of additional as-yet-unknown sources of CP violation.

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First Human Scanned By Spectral X-Ray Scanner

Chalk this up to an application of high-energy physics in the medical diagnostic field. The first human has been scanned by a new type of x-ray scanner (registration required to read article at this moment).

The MARS scanner uses Medipix3 technology developed at CERN to produce multi-energy images with high spatial resolution and low noise. Medipix is a family of read-out chips originally developed for the Large Hadron Collider and modified for medical applications.

The Medipix3 detector measures the energy of each X-ray photon as it is detected. This spectral information is used to produce 3D images that show the individual constituents of the imaged tissue, providing significantly improved diagnostic information.

I'll repeat this, maybe to those not in the choir, that many of the esoteric experiments that you think have no relevance to your everyday lives, may turn out to be the ones that might save your lives, or the lives of your loved ones, down the road. So think about this when you talk to your elected political representatives when it comes to funding basic science.

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An Overview of CLIC at CERN

This is the lesser known effort at CERN among the general public, and yet, it may have one of the most significant impacts coming out of this high-energy physics lab.

CLIC, or the Compact Linear Collider research project at CERN has been studying accelerator science for many years. This is one of a few prominent research centers on accelerator physics throughout the world. Both they and many other accelerator research centers are making advancements in accelerator science that have a direct benefit and application to the general public.

So my intention in highlighting this article is not simply for you to learn what the people at CLIC do. Some of the description may even be beyond your understanding. What you should focus on is all the applications that are already in use, or can be possible in the near future, on the advancements made in this area of physics/engineering. These applications are not just within physics/engineering.

Unfortunately, as I've stated a few times in this blog, funding for accelerator science is often tied to funding in high energy physics, and for the US, the funding profile in this sector has been abysmal. So while accelerator science is actually independent of HEP, its funding has gone downhill with HEP funding over the last few years, especially after the shutdown of the Tevatron at Fermilab.

Whether you support funding, or increase in funding, of this area of study is a different matter, but you should at least be aware and have the knowledge of what you are supporting or not supporting, and not simply make a decision based on ignorance of what it is and what it's implication can be.

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Therapeutic Particles

No, this is not some mumbo-jumbo New Age stuff.

While this technique has become more common, and there are already several places here in the US that are researching this, this is a nice article to introduce to you the current state-of-the-art in using charged particles in medicine, especially in treating and attacking cancer. It appears that the use of carbon ions is definitely catching up in popularity over the current use of protons.

When you read this article, pay attention to the fact that this is an outcome of our understanding of particle accelerators, that this is a particle accelerator applications, and that high-energy physics experimental facilities are often the ones that either initiated the project, or are hosting it. So next time someone asks you the practical applications of particle accelerators or particle physics, point to this.

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Table-Top Elementary Particle Experiment

I love reading articles like this one, where it shows that one can do quite useful research in elementary particles using experimental setup that is significantly smaller (and cheaper) than large particle colliders.

Now, he’s suddenly moving from the fringes of physics to the limelight. Northwestern University in Evanston, Illinois, is about to open a first-of-its-kind research institute dedicated to just his sort of small-scale particle physics, and Gabrielse will be its founding director.

The move signals a shift in the search for new physics. Researchers have dreamed of finding subatomic particles that could help them to solve some of the thorniest remaining problems in physics. But six years’ worth of LHC data have failed to produce a definitive detection of anything unexpected.

More physicists are moving in Gabrielse’s direction, with modest set-ups that can fit in standard university laboratories. Instead of brute-force methods such as smashing particles, these low-energy experimentalists use precision techniques to look for extraordinarily subtle deviations in some of nature’s most fundamental parameters. The slightest discrepancy could point the way to the field’s future. 

Again, I salute very much this type of endeavor, but I dislike the tone of the title of the article, and I'll tell you why.

In science, and especially physics, there is seldom something that has been verified, found, or discovered using just ONE experimental technique or detection method. For example, in the discovery of the Top quark, both CDF and D0 detectors at Fermilab had to agree. In the discovery of the Higgs, both ATLAS and CMS had to agree. In trying to show that something is a superconductor, you not only measure the resistivity, but also magnetic susceptibility.

In other words, you require many different types of verification, and the more the better or the more convincing it becomes.

While these table-top experiments are very ingenious, they will NOT replace the big colliders. No one in their right mind will tell CERN to "step aside", other than the author of this article. There are discoveries or parameters of elementary particles that these table-top experiments can study more efficiently than the LHC, but there are also plenty of the parameter phase space that the LHC can probe that can't be easily reached by these table-top experiments. They all are complimenting each other!

People who don't know any better, or don't know the intricacies of how experiments are done or how knowledge is gathered, will get the impression that because of these table-top experiments, facilities like the LHC will no longer be needed. I hate to think that this is the "take-home" message that many people will get.

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Hyperfine Splitting of Anti-Hydrogen Is Just Like Ordinary Hydrogen

More evidence that the antimatter world is practically identical to our regular matter world. The ALPHA collaboration at CERN has reported the first ever measurement of the anti-hydrogen hyperfine spectrum, and it is consistent to that measured for hydrogen.

Now, they have used microwaves to flip the spin of the positron. This resulted not only in the first precise determination of the antihydrogen hyperfine splitting, but also the first antimatter transition line shape, a plot of the spin flip probability versus the microwave frequency.

“The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting,” the researchers said.

“From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 ± 0.5 MHz, consistent with expectations for atomic hydrogen at the level of four parts in 10,000.”

I am expecting a lot more studies on these anti-hydrogen, especially now that they have a very reliable way of sustaining these things.

The paper is an open access on Nature, so you should be able to read the entire thing for free.

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The Higgs - Five Years In

In case you've been asleep the past 5 years or so and what to catch up on our lovable Higgs, here is a quick, condensed version of the saga so far.

Where were you on 4 July 2012, the day the Higgs boson discovery was announced? Many people will be able to answer without referring to their diary. Perhaps you were among the few who had managed to secure a seat in CERN’s main auditorium, or who joined colleagues in universities and laboratories around the world to watch the webcast.

This story promises to have lots of sequels, just like the movies released so far this year.

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The 750-GeV Blip At LHC - It Came And Went

A lot of HEP were in a tizzy since last year over the unexpected peak in the data at 750 GeV. And now, early reports from the current meeting going on in Chicago are indicating that this might be just a statistical anomaly.

Sadly, it seems that the 750 GeV particle wasn’t meant to be. Physicists at the International Conference on High Energy Physics (ICHEP) in Chicago were due to reveal the latest data on the excess of photon pairs at 750 GeV later today, but a paper accidentally posted online last night by the CMS collaboration states that their new round of data found no extra photons. This suggests the earlier hints were just a statistical fluke.

“As data comes in, excesses tend to come and go,” says CMS researcher Nadja Strobbe at Fermilab, near Batavia, Illinois. Researchers from ATLAS are due to present their results later today, but rumours suggest they will announce that the 750 GeV bump is gone.

But the fun part is all the theory papers that came gushing out as soon as the possibility of this being real.

A week after the announcement, theorists had written over 100 possible explanations; today, there are over 500. Nearly all of these papers posit the existence of a particle with a mass of 750 GeV or higher whose decay created the extra photons. Because this particle would have been outside the standard model of particle physics, it could have forced a reconsideration of how particles and forces interact.

I've always been curious to ask many of the people who did similar things on what they have to say for themselves. They had just created an explanation for the existence of the unicorn.

This is not new. When the OPERA collaboration indicated a faster-than-light neutrino detection a few years ago, numerous theory papers came out for that as well, proposing a myriad of particles and new physics. This is all before this result was confirmed. And of course, we all know what happened with that one as well.

I guess that people would rather be FIRST to be correct rather than be cautious and not appear foolish. After all, how many of us would remember that such-and-such wrote a paper to explain something that never existed in the first place?

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New Physics Beyond The Higgs?

Marcelo Gleiser has written a nice article on the curious 750 GeV bump coming from the LHC as announced last year. It is a very good article for the general public, especially on his condensed version of the analysis provided by PRL on the possible origin of this bump.

Still, there is an important point that I want to highlight that is not necessarily about this particular experiment, but rather about physicists and how physics is done. It is in this paragraph:

The exciting part of this is that the bump would be new, surprising physics, beyond expectations. There's nothing more interesting for a scientist than to have the unexpected show up, as if nature is trying to nudge us to look in a different direction.

If you have followed this blog for a considerable period of time, you would have read something similar in my many postings. This is especially true when I tried to debunk the erroneous claim of many crackpots who keep stressing that scientists are merely people who simply work within the box, and can't think outside of the box, or refuse to look for something new. This is of course, utterly dumb and false, because scientists, by definition, study things that are not known, not fully understood, etc. Otherwise, there will be no progression of knowledge the way we have seen it.

I'm going to keep harping this, because I continue to see nonsense like this being perpetuated in many different places.

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LHC Knocked Out By A Weasel?

You can't make these things up!

CERN's Large Hadron Collider, the world's biggest particle accelerator located near Geneva, Switzerland, lost power Friday. Engineers who were investigating the outage made a grisly discovery -- the charred remains of a weasel, CERN spokesman Arnaud Marsollier told CNN.
If you are a weasel kind, be forewarned! Don't mess around at CERN!

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Socio-Economic Impact of the LHC

This is an interesting analysis of the impact of the LHC, especially in terms of economics.

I think many politicians and the general public do not realize that even for something that is built to study something that appears to be esoteric and no direct and immediate application, there can be immediate benefits socially and economically.

That is why I continue to be surprised and appalled that the US continue to not "care" about their loss in having any kind of high-energy physics particle collider on their soil anymore. This is especially puzzling in light of the fact that other parts of the world are seriously pursuing having such experiments within their borders, even if it is under an international collaboration. Certainly China is pursuing having such facilities, and Japan just announced the start of an electron-positron collider. As far as I'm aware of, Japan is the leading contender for hosting the International Linear Collider (ILC), something that Fermilab has also been pursuing.

But with the devastating budget issues in the US, this is looking to be very bleak. People seem to only see the money being spent on such facilities, without realizing the significant impact not only on the intellectual aspect of it, but the economic impacts, both short-term and long-term. An analysis done in this preprint may not make it to the people who hold the power, but it is certainly there to be seen.

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2 Most Dangerous Numbers? Phooey!

Baloney!

This is a report on a TED talk by a CERN physicist Harry Cliff. In it, he discussed the conundrum theoretical physicists are facing with the current knowledge of the Higgs and dark energy.

At the core of Cliff's argument are what he calls the two most dangerous numbers in the universe. These numbers are responsible for all the matter, structure, and life that we witness across the cosmos.

So in the attempt to make this story more "sexy", we of course have to make sound as if we are reaching an apocalyptic problem that will spell "the end of physics" (how many times have you heard that already?). There are several problems with this reporting:

1. The degree of certainty on the validity of ANY of these theories is LOW. Anyone wants to argue that? So while it is certainly important to pursue it, the TED talk can only be seen as being a very quick and superficial snapshot of an ONGOING and still preliminary investigation! Our knowledge of the Higgs and dark energy are still in the extreme infancy when compared to many of the more established areas. This is like groping in the dark and then pronouncing that we're doom because someone  heard something moving.

2. The claim that "getting answers could be impossible" is false. In that section of the report, nothing that was described is impossible. The limit on the energy of the LHC isn't a limitation on the physics or our ability. We can certainly build a bigger, more energetic collider (the Superconducting Supercollider that was supposed to be built in Texas in the 80's would have had a higher energy than the LHC!). New research on advanced acceleration scheme, led by a slew of wakefield-type accelerators, has the potential of boosting particle energy even higher while making the accelerator more compact. So no, there is no ceiling yet, in terms of the physics, in going to higher and higher energies. What is hindering the building of such machines is the economics! This is not a physical impossibility, but rather a social "impossibility".

I am always skeptical whenever someone, or even a scientist, claim of "maybe" we might reach the end of something, or that we'll never get beyond such-and-such. Again, we seem to have never learned what happened when we claim that, with the state of our knowledge of superconductivity in the early 1980's being a prime example. Almost everyone thought that the field was fully matured, and that there's nothing left to discovery there other than refining our knowledge and the production of the material. Then high-Tc superconductors were discovered and all hell broke loose!

Scientists need to be aware that talks like this can be latched on by the public because news reporters like to over-emphasize the "dramatic" parts. Without intending it, something that many of us know to be still very much a "work in progress" becomes a "fact" to many people outside the field.

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Higgs Mass Refined

The combined data from ATLAS and CMS from LHC Run 1 has produced a Higgs mass with greater accuracy.

ATLAS reported the mass of this new boson to be in the mass region of 126 billion electronvolts, and CMS found it to be in the region of 125. In May 2015, the two experiments combined their measurements, refining the Higgs mass closer to 125.09 GeV.

But what is important is the report on the measurement of the coupling strength in the Higgs interactions.

This particular analysis focused on the interaction of the Higgs boson with other particles, known as coupling strength. The combined measurements are more precise than each experiment could accomplish alone, and results establish that the Higgs mechanism grants mass to both the matter and force-carrying particles as predicted by the Standard Model of particle physics.
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In the Standard Model, how strongly the Higgs boson couples to another particle determines that particle’s mass and the rate at which a Higgs boson decays into other particles.
For instance, the Higgs boson couples strongly with the bottom quark and very weakly with the electron; therefore, the bottom quark has a much greater mass than the electron and the Higgs will commonly decay into a bottom quark and its antiquark.

This is why there is still a lot more to be measured and refined in Run 2.

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Report From 13 TeV

So far so good!

This report briefly describes the achievement of getting to 13 TeV collision energy at the LHC.

At 10.40 a.m. on 3 June, the LHC operators declared "stable beams" for the first time at a beam energy of 6.5 TeV. It was the signal for the LHC experiments to start taking physics data for Run 2, this time at a collision energy of 13 TeV – nearly double the 7 TeV with which Run 1 began in March 2010.

So far, they haven't been swallowed by a catastrophic black hole that is supposed to destroy our world. Darn it! What's next? Sighting of supersymmetry particles? You must be joking!

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Pentaquark Discovery - Here We Go Again!

I read with a combination excitement and skepticism of the report that LHCb may have seen not one, but two pentaquarks. The skepticism should be justified because previous claims of the discovery of such quarks have turned out to be false. Still, this one comes with a 9sigma statistics.

The LHCb team is confident that the particles are indeed pentaquarks that comprise two up quarks, one down quark, one charm quark and one anticharm quark. "Benefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states," explains LHCb physicist Tomasz Skwarnicki of Syracuse University in the US. 

As always, and as with any other new and important claim, time will tell as more analysis and experiments are done. The public and the media, especially, need to understand that this is still a work in progress, as with any scientific endeavor.

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CERN Confirms The Existence of The Force

I can't let April 1st go without at least one goofy post, can I? So here it is!

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CERN's ALPHA Experiment

See, I like this. I like to highlight things that most of the general public simply don't know much about, especially when another major facility throws a huge shadow over it.

This article mentions two important things about CERN: It is more than just the LHC, and it highlights another very important experiment, the ALPHA experiment.

ALPHA’s main aim is to study the internal structure of the antihydrogen atom, and see if there exist any discernible differences within it that set it apart from regular hydrogen. In 2010 ALPHA was the first experiment to trap 38 antihydrogen atoms (an antielectron orbiting an antiproton) for about one-fifth of a second and then the team perfected its apparatus and technique to trap a total of 309 antihydrogen atoms for 1000 s in 2011. Hangst hopes that with the new updated ALPHA 2 device (which includes lasers for spectroscopy), the researchers will soon see precisely what lies within an antihydrogen atom by studying its spectrum. They had a very short test run of a few weeks with ALPHA 2 late last year, and will begin their next set of experiment in earnest in the coming months.

They will be producing more amazing results in the future, because this is all uncharted territory. 

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The Detectors at the LHC

Don Lincoln has a video on the 4 detectors at the LHC.



As you watch this, don't miss the fact that these are "... technological marvels..." in themselves, and that high energy physics had to invent and make their own detectors and detection processes to advance the field. Detector and instrumentation physics have always been an integral part of experimental high energy physics, and one often sees students in this field that are actually working on detector physics.

As a consequence, high energy physics drives innovations and new applications that eventually leaks into the rest of the world. This is a point that is often missed by those outside of the field.

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The LHC

For those of you who have been unconscious for the past 5 or 6 years, here is another video explaining the LHC and the latest upgrade that will bring it to a higher energy regime.



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