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Modern physics is full of the sort of twisty, puzzle-within-a-puzzle plots youd find in a classic detective story: Both physicists and detectives must carefully separate important clues from unrelated information. Both physicists and detectives must sometimes push beyond the obvious explanation to fully reveal whats going on.

And for both physicists and detectives, momentous discoveries can hinge upon Sherlock Holmes-level deductions based on evidence that is easy to overlook. Case in point: the Muon g-2 experiment currently underway at the US Department of Energys Fermi National Accelerator Laboratory.

The current Muon g-2 (pronounced g minus two) experiment is actually a sequel, an experiment designed to reexamine a slight discrepancy between theory and the results from an earlier experiment at Brookhaven National Laboratory, which was also called Muon g-2.

The discrepancy could be a sign that new physics is afoot. Scientists want to know whether the measurement holds up or if its nothing but a red herring.

The Fermilab Muon g-2 collaboration has announced it will present its first result on April 7. Until then, lets unpack the facts of the case.

Illustration by Sandbox Studio, Chicago with Steve Shanabruch

All spinning, charged objectsincluding muons and their better-known particle siblings, electronsgenerate their own magnetic fields. The strength of a particles magnetic field is referred to as its magnetic moment or its g-factor. (Thats what the g part of g-2 refers to.)

To understand the -2 part of g-2, we have to travel a bit back in time.

Spectroscopy experiments in the 1920s (before the discovery of muons in 1936) revealed that the electron has an intrinsic spin and a magnetic moment. The value of that magnetic moment, g, was found experimentally to be 2. As for why that was the valuethat mystery was soon solved using the new but fast-growing field of quantum mechanics.

In 1928, physicist Paul Diracbuilding upon the work of Llewelyn Thomas and othersproduced a now-famous equation that combined quantum mechanics and special relativity to accurately describe the motion and electromagnetic interactions of electrons and all other particles with the same spin quantum number. The Dirac equation, which incorporated spin as a fundamental part of the theory, predicted that g should be equal to 2, exactly what scientists had measured at the time.

But as experiments became more precise in the 1940s, new evidence came to light that reopened the case and led to surprising new insights about the quantum realm.

Illustration by Sandbox Studio, Chicago with Steve Shanabruch

The electron, it turned out, hada little bit of extra magnetism that Diracs equation didnt account for. That extra magnetism, mathematically expressed as g-2 (or the amount that g differs from Diracs prediction), is known as the anomalous magnetic moment. For a while, scientists didnt know what caused it.

If this were a murder mystery, the anomalous magnetic moment would be sort of like an extra fingerprint of unknown provenance on a knife used to stab a victima small but suspicious detail that warrants further investigation and could unveil a whole new dimension ofthe story.

Physicist Julian Schwinger explained the anomaly in 1947 by theorizing that the electron could emit and then reabsorb a virtual photon. The fleeting interaction would slightly boost the electrons internal magnetism by a tenth of a percent, the amount needed to bring the predicted value into line with the experimental evidence. But the photon isnt the only accomplice.

Over time, researchers discovered that there was an extensive network of virtual particles constantly popping in and out of existence from the quantum vacuum. Thats what had been messing with the electrons little spinning magnet.

The anomalous magnetic moment represents the simultaneous combined influence of every possible effect of those ephemeral quantum conspirators on the electron. Some interactions are more likely to occur, or are more strongly felt than others, and they therefore make a larger contribution. But every particle and force in the Standard Model takes part.

The theoretical models that describe these virtual interactions have been quite successful in describing the magnetism of electrons. For the electrons g-2, theoretical calculations are now in such close agreement with the experimental value that its like measuring the circumference of the Earth with an accuracy smaller than the width of a single human hair.

All of the evidence points to quantum mischief perpetrated by known particles causing any magnetic anomalies. Case closed, right?

Not quite. Its now time to hear the muons side of the story.

Illustration by Sandbox Studio, Chicago with Steve Shanabruch

Early measurements of the muons anomalous magnetic moment at Columbia University in the 1950s and at the European physics laboratory CERN in the 1960s and 1970s agreed well with theoretical predictions. The measurements uncertainty shrank from 2% in 1961 to 0.0007% in 1979. It looked as if the same conspiracy of particles that affected the electrons g-2 were responsible for the magnetic moment of the muon as well.

But then, in 2001, the Brookhaven Muon g-2 experiment turned up something strange. The experiment was designed to increase the precision from the CERN measurements and look at the weak forces contribution to the anomaly. It succeeded in shrinking the error bars to half a part per million. But it also showed a tiny discrepancyless than 3 parts per millionbetween the new measurement and the theoretical value. This time, theorists couldnt come up with a way to recalculate their models to explain it. Nothing in the Standard Model could account for the difference.

It was the physics mystery equivalent of a single hair found at a crime scene with DNA that didnt seem to match anyone connected to the case. The question wasand still iswhether the presence of the hair is just a coincidence, or whether it is actually an important clue.

Physicists are now re-examining this hairat Fermilab, with support from the DOE Office of Science, the National Science Foundation and several international agencies in Italy, the UK, the EU, China, Korea and Germany.

In the new Muon g-2 experiment, a beam of muonstheir spins all pointing the same directionare shot into a type of accelerator called a storage ring. The rings strong magnetic field keeps the muons on a well-defined circular path. If g were exactly 2, then the muons spins would follow their momentum exactly. But, because of the anomalous magnetic moment, the muons have a slight additional wobble in the rotation of their spins.

When a muon decays into an electron and two neutrinos, the electron tends to shoot off in the direction that the muons spin was pointing. Detectors on the inside of the ring pick up a portion of the electrons flung by muons experiencing the wobble. Recording the numbers and energies of electrons they detect over time will tell researchers how much the muon spin has rotated.

Using the same magnet from the Brookhaven experiment with significantly better instrumentation, plus a more intense beam of muons produced by Fermilabs accelerator complex, researchers are collecting 21 times more data to achieve four times greater precision.

The experiment may confirm the existence of the discrepancy; it may find no discrepancy at all, pointing to a problem with the Brookhaven result; or it may find something in between, leaving the case unsolved.

Illustration by Sandbox Studio, Chicago with Steve Shanabruch

Theres reason to believe something is going on that the Standard Model hasnt told us about.

The Standard Model is a remarkably consistent explanation for pretty much everything that goes on in the subatomic world. But there are still a number of unsolved mysteries in physics that it doesnt address.

Dark matter, for instance, makes up about 27% of the universe. And yet, scientists still have no idea what its made of. None of the known particles seem to fit the bill. The Standard Model also cant explain the mass of the Higgs boson, which is surprisingly small. If the Fermilab Muon g-2 experiment determines that something beyond the Standard Modelfor example an unknown particleis measurably messing with the muons magnetic moment, it may point researchers in the right direction to close another one of these open files.

A confirmed discrepancy wont actually provide DNA-level details about what particle or force is making its presence known, but it will help narrow down the ranges of mass and interaction strength in which future experiments are most likely to find something new. Even if the discrepancy fades, the data will still be useful for deciding where to look.

It might be that a shadowy quantum figure lurking beyond the Standard Model is too well hidden for current technology to detect. But if its not, physicists will leave no stone unturned and no speck of evidence un-analyzed until they crack the case.

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The mystery of the muon's magnetism | symmetry magazine - Symmetry magazine

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In the second part of a series on the science of consciousness, Sen Duke features those who believe the human brain works more like a quantum computer.

The mystery of consciousness, according to Roger Penrose, the 89-year-old winner of the 2020 Nobel Prize in physics, will only be solved when an understanding is found for how brain structures can harness the properties of quantum mechanics to make it possible.

Penrose, emeritus professor of mathematics at the University of Oxford a collaborator of the late Stephen Hawking who won the Nobel for his work on the nature of black holes, has been interested in consciousness since he was a Cambridge graduate student. He has authored many books on consciousness, most notably The Emperors New Mind (1989), and believes it to be so complex that it cannot be explained by our current understanding of physics and biology.

As a young mathematician, Penrose believed, and still does today, that something is true, not because it is derived from the rules or axioms, but because its possible to see that its true. The ultimate truth in mathematics, he reasoned, cannot, therefore, be proven by following algorithms; a set of calculations performed to instruction.

It followed, Penrose deduced, that the truth of how consciousness operates in the brain may not be provable by algorithms or thinking of the brain as a computer. This idea set off a life-long quest to understand the mysterious processes governing consciousness going on in our heads, which, Penrose says, remain beyond our existing understanding of physics, mathematics, biology or computers.

After The Emperors New Mind was published, Penrose received a letter from Stuart Hameroff, professor of anaesthesiology at the University of Arizona, who also had a long interest in understanding consciousness. In the letter, Hameroff described tiny structures in the brain called microtubules, which he believed were capable of generating consciousness by tapping into the quantum world.

Hameroff, who has worked as an anaesthesiologist for 45 years, believes anaesthesia may work through specifically targeting consciousness through its action on the neural microtubules. After writing the letter, he met Penrose in 1992, and over the next two years they developed radical ideas about consciousness which ran counter to the thinking of most neuroscientists, and still do.

Penrose and Hameroff believe that the human brain works more like a quantum computer than any classical computers. This is because future quantum computers will be designed to harness the ability of quantum particles to exist in multiple locations, states and positions all at once. These quantum effects arise in the microtubules, they suggest, which then act as the brains link to the quantum world.

The microtubules were structures that Hameroff had studied in since his graduate student days. They interested him initially, he recalls, because of their role in cancer. The microtubules were crucial to cell division, by splitting chromosomes perfectly in two. If microtubules did not function then chromosomes could be divided unevenly in three or four, not two, he says, thus triggering cancer.

The central role that the microtubules played in cell division, led Hameroff to speculate that they were controlled by some form of natural computing. In his book Ultimate Computing (1987), he argues that microtubules have sufficient computation power to produce thought. He also argues that the microtubules the tiny structures which give the cell its shape and act like a scaffold are the most basic units of information processing in the brain, not the neurons.

The fact that microtubules are found in animals, plants and even single-celled amoeba, says Hameroff means that consciousness is probably widespread and exists at many levels. The way microtubules work to produce consciousness, he says, can be thought of as being similar to how a conductor directs the sounds produced by individual musicians and orchestrates it into a coherent functioning orchestra.

Consciousness will be a different experience in humans compared to amoeba, says Hameroff. A single-celled organism might have proto-consciousness; that is consciousness without no memory, without context, isolated, not connected with anything else, and occurring at low intensity. There wouldnt be any sense of self memory or meaning, but there would be some glimmer of feeling or awareness.

Penrose agreed with Hameroff that the microtubules could possibly maintain the quantum coherence needed for complex thought and a collaboration began that continues today. Consciousness, the two believed, was a non-logarithmic, quantum process that could only be understood by a theory that linked the brain to quantum mechanics.

This led Penrose and Hameroff to develop a theory called orchestrated reduction, or OR. This proposed that areas of the brain where consciousness occurs must be structured so that they can hold innumerable quantum possibilities all at once per the rules of quantum mechanics while permitting the controlled reduction of such endless possibilities, without destroying the quantum system.

The microtubules were, both agreed, the best currently known structures in the brain where quantum processes could take place in a stable way and be harnessed to generate our conscious experience. They agreed that consciousness might ultimately be found in many locations across the brain, not just confined to the microtubules.

According to Hameroff, the presence of pyramid-shaped cells containing microtubules organised to run in two directions, rather than in parallel, which is more usual, was the difference between the parts of the brain where consciousness happens and the unconscious brain. Its notable, he says, that these pyramidal cells are not present in the cerebellum; an area considered to be unconscious.

One of the main criticisms of the Penrose-Hameroff quantum-based theory of consciousness is that there is no way to measure whether quantum processes are happening in the microtubules or any other parts of the brain. Penrose accepts such criticism but believes such measurements will become possible over the long term.

Hameroff already has plans to test whether quantum states exist inside microtubules. If he can prove this, his next step will be to see if such states disappear under anaesthesia. If they do then he says it strengthens the theory that microtubules host conscious thought.

Brain scanning techniques like PET and MRI, have become very powerful but are of little or no use in consciousness studies, says Penrose. They can, he notes, monitor blood flow and where activity is happening in the brain but they cant say whether that activity involves conscious thought. For that something else is required.

One way to measure thought, some scientists believe, is by observing brainwaves. For example, some evidence suggests that brainwaves, oscillating at about 40 Hertz, can be correlated with consciousness.

Penrose and Hameroff would like to find evidence for quantum brain oscillations in the microtubules but have no tools yet to achieve this.

This is a long-term project, which I dont see resolving for many years, says Penrose who, given his age, would like to see things moving faster. I feel pretty sure that we havent really understood fully how biological systems are organised and how they may be taking advantage of the subtle effects of [quantum] physics.

The big difficulty with trying to measure quantum processes in the brain, Penrose points out, is that such effects are destroyed when they are observed or brought into contact with the outside world. It is going to be very hard to have direct access to consciousness, as to observe it, currently, would be to destroy it.

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Can science explain the mystery of consciousness? - The Irish Times

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KARACHI:

In the words of one researcher, science is not meant to cure us of mystery. Instead, he argues, it is supposed to reinvent and reinvigorate.

For us lay people, science remains a mystery sans reinvention. For reasons mundane and existential, most of us shy away from asking the fundamental questions. Perhaps it is due to our own shyness, even fear, that many of us hold such awe for those who dare go intellectually where the rest of us are unwilling or incapable of going.

Speaking of awe and mysteries, there are a handful of places around the world that evoke both while capturing our collective imagination. If I mention the European Organisation for Nuclear Research, it may or may not mean anything to most of us. But, if I use the acronym CERN, many may find their thoughts transported to the world of Dan Brown, of scientific intrigue and where the impossible becomes possible.

Speaking still of mysteries, and of CERN, there is the question of antimatter, a material many of us may confuse with the similar sounding yet wildly different concepts of dark matter and dark energy. Beyond our own mysterious understanding of it, lie the antimatter mysteries that the scientists who study it reinvent and reinvigorate in their attempts to understand it.

As luck, or perhaps fate, would have it, one of them is Pakistani. Who better to demystify both what we know at the moment about antimatter and what working at CERN entails.

Demystifying antimatter

For Muhammad Sameed, a lifes yearning for understanding has led to a dream come true. The 32-year-old Islamabad native is among a mere handful of Pakistanis who would think themselves lucky for a chance to work at CERN. What is more in Sameeds case, he is physicist involved in studying antimatter particles at one of the worlds premier physics research organisations.

At CERN, Sameed is part of the ALPHA experiment, an acronym that stands for the Antihydrogen Laser Physics Apparatus. Just recently, the ALPHA collaboration effort succeeded in cooling down antihydrogen particles the simplest form of atomic antimatter with laser light.

Speaking with The Express Tribune, the young scientist began by admitting that the wider scientific community had perhaps contributed to some of the public misunderstandings about antimatter. I think it is us physicists fault for giving such similar names to such different concepts, he said when asked about the difference between antimatter, dark matter and dark energy.

Taking his own crack at remedying that, he explained: Before we explain antimatter, it is important remember what matter is, at the subatomic level.

Most of us learn about atoms and how they are made of electrons, protons and neutrons in school. But that is where the general awareness ends, said Sameed. If you look deeper, while electrons are fundamental particles they belong to a family of particles called leptons protons and neutrons are not. Those two are made up of two more kinds of fundamental particles: the quarks and the gluons, which bind them. He added that all matter that surrounds us and that we can interact with is made of particles from two families, namely quarks and leptons. Both families consist of six kinds of particles each.

According to Sameed, we have known all of this since the early part of the previous century, when quantum mechanics was developed. Where does antimatter come in? It was first articulated in a theoretical study by physicist Paul Dirac, he shared.

Dirac, while solving a quantum mechanics equation, arrived at two solutions, one positive and the other negative. The positive one corresponded to the electron. Dirac initially disregarded the negative solution, but later used it to hypothesise the existence of antielectrons, Sameed explained. He made that prediction in 1928, and just four years later, an American experiment actually discovered it.

How was the discovery made, you wonder? We have all these particles from outer space that pass through our planet, said Sameed. If we apply a magnetic field to them, we can determine which direction these particles turn in. If electrons turn to one side, particles with the opposite charge would turn in the other direction.

The physicist shared that since the discovery of the antielectron almost 90 years ago scientists have discovered an antimatter counterpart to each regular matter particle we know of. The story we physicists should be telling people is that not only is antimatter real, but that these are particles are found in nature, he said. The real question is this: we know from equations and experiments that when matter is produced in a lab or after the Big Bang an equal amount of antimatter is produced. So how is it that regular matter became so dominant in our universe and why is there so little antimatter occurring in nature?

According to Sameed, all research into antimatter at CERN and other organisations is focused on this question: What happened? Where did all the antimatter go? One proposed explanation, he shared, is that antimatter has some as yet unknown property that converts it into regular matter in unequal amounts. So by producing and trapping antimatter in a lab, we test it for various properties and whether those can explain what happened to most antimatter in nature. This has been the focus of research for the last 30 to 40 years.

Cooling with lasers

Explaining the recent ALPHA experiment with laser cooling, Sameed began by explaining the choice of antihydrogen. Hydrogen is the simplest atom we know of, with just one proton and one electron. Antihydrogen, similarly, is the simplest antiatom, he said.

You take an antiproton, get an antielectron to orbit it, and you should have an antihydrogen atom. But this is easier said than done, he explained. The main challenge with producing antihydrogen or any other antimatter particle is that if an anti-matter particle comes in contact with a regular matter particle, both are annihilated. So in order to capture anti-matter particles, you need to create perfect vacuum to ensure they dont come in contact with matter particles.

Sameed added that the challenge isnt just limited to creating vacuum either. You need to make sure that the container being used is designed in a way to ensure antimatter particles dont come in contact with its walls. This is done using electromagnetic fields.

Explaining how scientists study antimatter, Sameed began by explaining how regular matter particles would be studied. Take a regular hydrogen atom which is in what we call a ground state or normal state. If we shine a laser with a specific energy level onto that simple atom, its electron can jump into an excited state. He said that scientists have known about the effects of lasers on hydrogen atoms for a long time. We know what frequencies can excite it. For our experiment, we thought to test the same on anti-hydrogen atoms. We wondered if it would react differently to regular hydrogen due to differences in energy levels or other properties. Perhaps our findings could help unravel some of the mystery around why there is so little antimatter in the universe?

According to Sameed, the effects of lasers on antihydrogen were first tested in 2017. We shined a laser with the same frequency as the one that excites electrons in a regular hydrogen atom on to an antihydrogen atom. The results suggest the effect on antihydrogen was more or less the same, he said. But one side effect that we uncovered at the time and this had been predicted before the experiment was that laser light can cool particles.

Normally we use lasers to heat things, but if you shine a laser beam on an atom that is coming towards it, it has an effect of slowing down the atom, he added. So our current experiment was the first time we tested this laser cooling principle on antimatter.

Sameed further revealed that the next antimatter experiment being developed aims to study how it behaves under the influence of gravity from regular matter. We know how gravitational forces work between regular matter. Our equations suggest the same interaction would be true between two objects made of antimatter. But, we want to find out what happens in terms of gravity when there is an interaction between matter and antimatter. At the moment, we dont even have any strong theories to predict what will happen.

Easier said than done

When Sameed explains the experiment, one may get the false impression that it is as easy as pointing a laser towards antimatter. But nothing could be further from the truth.

For starters the laser we use is not the one used in laser pointers that most people know of. Ours is an ultraviolet laser, which is invisible to the naked eye and has a much higher energy level. It is not available commercially and is very difficult to manufacture, so we have to develop it in-house at CERN, he said. The laser in question is also absorbed by air particles, Sameed added. Not only must the beam travel through vacuum, it must be produced and aimed in vacuum as well.

According to Sameed, firing a laser at antihydrogen is a very different challenge that firing it at regular hydrogen. For normal hydrogen, we can shine the laser from any angle. But for antihydrogen, because the entire container is surrounded by special magnets to keep it from touching the walls, there is a very small access point for the laser itself.

Commercial possibilities

Any innovative technology can open up opportunities beyond what those who developed it are sometimes able to appreciate. Speaking on this aspect, Sameed said: We scientists develop such innovative solutions to satisfy pure curiosity and answer the fundamental questions about physics. But all research produces technological byproducts and sooner or later, they trickle down to R&D companies and eventually to wider society.

Asked if he could foresee any antimatter applications used beyond research, Sameed said there was one example already in medical imaging, even if it was difficult to predict wider uses. The PET or Positron Emission Tomography scanner. The positron is an anti-matter particle. It is essentially an anti-electron.

Beyond that, CERN in general is responsible for developing a wide-range of technologies. For instance, to trap anti-matter particles, we need strong magnetic fields. To produce those, we have to develop superconducting magnets which have various commercial uses as well. For instance, such magnets are used in hospitals in MRI scanners. A lot of technologies used in modern medicine were first developed in research centres like CERN, Sameed revealed.

Even on the software side, applications developed to track near-instant physical phenomenon have been co-opted by some financing trading companies which want to leverage the ability to process information in microseconds.

Sameed added that all CERN research is open-source and accessible to anyone in the world. You can contact our knowledge transfer centre and gain our research to use in reasonable ways.

The value of research

According to Sameed, the side effects of research for researchs sake are undeniable. We can see it over the last few centuries. The countries and regions that invested in fundamental research and technology, are the ones that are now global powers, he said. But we dont even need to look at it philosophically. Just look at the Internet.

Sameed pointed out that the World Wide Web was originally developed by CERN in the 1980s as a means to share information between physicists instantaneously. The intention at the time was only to aid research. But it was made open source, and the effect of that simple choice in reshaping life can be seen today.

Back to the future

How does one get to work at CERN? For Sameed, the yearning to become a scientist was sparked by one movie most of us watch and loved growing up. I was five or six when I watched Back to the Future. I dont think I understood much about the movie at the time, but I remember finding the character of Doc Brown fascinating, he said. I decided then that I would at least try to be a scientist when I grew up.

In terms of background, Sameed admits he had an ordinary middle-class upbringing. But I am lucky that my parents tried to provide me the best education possible, he said. Still, CERN was beyond his dreams till the time he graduated A-Levels.

For Sameed, the path to a career in science opened with his elder brothers academic pursuits. He went to the US on scholarship to study chemical and biological engineering. That made me realise that I too could get in-depth education in physics abroad. Like him, I applied for a scholarship and was able to study physics at Cornell University. That really set the stage for me.

The next chapter began when Sameed came across the example of another Pakistani who went on a summer internship to CERN. He made me aware that there was a programme international students could apply for. I applied, with no hope of getting in, and originally I was rejected. But, some time later, they contacted me again and told me that I was a better fit for another department, and here I am.

According to Sameed, he initially believed his recruiters at CERN had made an error. But once I got here, I realised that I was no different from other students, from Europe or US or elsewhere. We Pakistanis are in no way inferior to other countries in terms of talent. All that is missing is awareness.

When not busy participating in research, Sameed tries to do his part to raise awareness about opportunities for other Pakistanis at CERN. Pakistan is now an associate member at CERN and what that means is that any Pakistani can apply for any job here. This is not limited to just positions for scientists and engineers, and involves things like administration and legal affairs, etc.

Pakistan and CERN

According to Sameed, at the youth level, there is more awareness about CERN in Pakistan now. In fact, Pakistan has one of the highest number of applicants to CERN, he said. But most of these are just student positions at the moment and for higher level positions, we are still lagging behind. In terms of Pakistanis who are at CERN for the long term, there may be four or five.

Even so, Pakistanis appear to be highly valued at CERN, Sameed revealed. Pakistani engineers have made a huge contribution to CERN and they are a very well respected community here. They always trust Pakistanis who make it to CERN to do a good job, he said. There is also immense pride for Pakistanis at CERN due to Dr Abdus Salams contributions, both to physics as a whole and to CERN during the time he spent here. One of the streets is even named after him, he added.

Asked what advice he had for other young Pakistanis who choose a similar path, the physicist pointed out that there are many opportunities available, not just in CERN, but other high quality institutes. Not only are Pakistanis eligible to apply, but they are looking for people from diverse backgrounds with talent, he said. Even if you dont have the confidence, I would say apply. Because you might think youre not good enough, but the people who are recruiting may believe otherwise.

Sameed reiterated that when he joined CERN, he realised he was as good as anyone else. My hope for the future is that in addition to engineers, more Pakistani physicists will join as well.

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Where did the antimatter go? - The Express Tribune

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