Root Privileges

Higgs mechanism

Is the Higgs boson doing its job?
At the heart of particle physics lies the Standard Model, a theory that has stood for nearly half a century as the best description of the subatomic realm. It tells us what particles exist, how they interact, and why the universe is stable at the smallest scales. The Standard Model has correctly predicted the outcomes of several experiments testing the limits of particle physics. Even then, however, physicists know that it’s incomplete: it can’t explain dark matter, why matter dominates over antimatter, and why the force of gravity is so weak compared to the other forces. To settle these mysteries, physicists have been conducting very detailed tests of the Model, each of which has either tightened their confidence in a hypothetical explanation or has revealed a new piece of the puzzle.

A central character in this story is a subatomic particle called the W boson — the carrier of the weak nuclear force. Without it, the Sun wouldn’t shine because particle interactions involving the weak force are necessary for nuclear fusion to proceed. W bosons are also unusual among force carriers: unlike photons (the particles of light), they’re massive, about 80-times heavier than a proton. This mass difference — of a massless photon and a massive W boson — arises due to a process called the Higgs mechanism. Physicists first proposed this mechanism in 1964 and confirmed it was real when they found the Higgs boson particle at the Large Hadron Collider (LHC) in 2012.

The particles of the Standard Model of particle physics. The W bosons are shown among the force-carrier particles on the right. The photon is denoted γ. The electron (e) and muon (µ) are shown among the leptons on the right. The corresponding neutrino flavours are showing on the bottom row, denoted ν. Credit: Daniel Dominguez/CERN

But finding the Higgs particle was only the beginning. To prove that the Higgs mechanism really works the way the theory says, physicists need to check its predictions in detail. One of the sharpest tests involves how W bosons scatter off each other at high energies. The key to achieving this is the W boson’s polarisation states. Both photons and W bosons have a property called quantum spin, but whereas for photons its value is zero, for W bosons its non-zero. The spin also has a direction. If it points sideways, the W boson is said to be transverse polarised; if it’s pointing along the particle’s direction of travel, the W boson is said to be longitudinally polarised. The longitudinal ones are special because their behaviour is directly tied to the Higgs mechanism.

Specifically, if the Higgs mechanism and the Higgs boson don’t exist, calculations involving the longitudinal W bosons scattering off of each other quickly give rise to nonsensical mathematical results in the theory. The Higgs boson acts like a regulator in this engine, preventing the mathematics from ‘blowing up’. In fact, in the 1970s, the theoretical physicists Benjamin Lee, Chris Quigg, and Hugh Thacker showed that without the Higgs boson, the weak force would become uncontrollably powerful at high energies, leading to the breakdown of the theory. Their work was an important theoretical pillar that justified building the colossal LHC machine to search for the Higgs boson particle.

Technical foundation for a muon collider laid at J-PARC

The terms Higgs boson, Higgs field, and Higgs mechanism describe related but distinct ideas. The Higgs field is a kind of invisible medium thought to fill all of space. Particles like W bosons and Z bosons interact with this field as they move and through that interaction they acquire mass. This is the Higgs mechanism: the process by which particles that would otherwise be massless become heavy.

The Higgs boson is different: it’s a particle that represents a vibration or a ripple in the Higgs field, just as a photon is a ripple in the electromagnetic field. Its discovery in 2012 confirmed that the field is real and not just something that appears in the mathematics of the theory. But discovery alone doesn’t prove the mechanism is doing everything the theory demands. To test that, physicists need to look at situations where the Higgs boson’s balancing role is crucial.

The scattering of longitudinally polarised W bosons is a good example. Without the Higgs boson, the probabilities of the scatterings occurring uncontrollably at higher energy, but with the Higgs boson in the picture, they stay within sensible bounds. Observing longitudinally polarised W bosons behaving as predicted is thus evidence for the particle as well as a check on the field and the mechanism behind it.

Imagine a roller-coaster without brakes. As it goes faster and faster, there’s nothing to stop it from flying off the tracks. The Higgs mechanism is like the braking system that keeps the ride safe. Observing longitudinally polarised W bosons in the right proportions is equivalent to checking that the brakes actually work when the roller-coaster speeds up.

Credit: Skyler Gerald

Another path that physicists once considered and that didn’t involve a Higgs boson at all was called technicolor theory. Instead of a single kind of Higgs boson giving the W bosons their mass, technicolor proposed a brand-new force. Just as the strong nuclear force binds quarks into protons and neutrons, the hypothetical technicolor force would bind new “technifermion” particles into composite states. These bound states would mimic the Higgs boson’s job of giving particles mass, while producing their own new signals in high-energy collisions.

The crucial test to check whether some given signals are due to the Higgs boson or due to technicolor lies in the behaviour of longitudinally polarised W bosons. In the Standard Model, their scattering is kept under control by the Higgs boson’s balancing act. In technicolor, by contrast, there is no Higgs boson to cancel the runaway growth. The probability of the scattering of longitudinally polarised W bosons would therefore rise sharply with more energy, often leaving clearly excessive signals in the data.

Thus, observing longitudinally polarised W bosons at consistent with the predictions of the Standard Model, and not finding any additional signals, would also strengthen the case for the Higgs mechanism and weaken that for technicolor and other “Higgs-less” theories.

At the Large Hadron Collider, the cleanest way to study look for such W bosons is in a phenomenon called vector boson scattering (VBS). In VBS, two protons collide and the quarks inside them emit W bosons. These W bosons then scatter off each other before decaying into lighter particles. The leftover quarks form narrow sprays of particles, or ‘jets’, that fly far forward.

If the two W bosons happen to have the same electric charge — i.e. both positive or both negative — the process is even more distinctive. This same-sign WW scattering is quite rare and that’s an advantage because then it’s easy to spot in the debris of particle collisions.

Both ATLAS and CMS, the two giant detectors at the LHC, had previously observed same-sign WW scattering without breaking down the polarisation. In 2021, the CMS detector reported the first hint of longitudinal polarisation but at a statistical significance only of 2.3 sigma, which isn’t good enough (particle physicists prefer at least 3 sigma). So after the LHC completed its second run in 2018, collecting data from around 10 quadrillion collisions between protons, the ATLAS collaboration set out to analyse it and deliver the evidence. This group’s study was published in Physical Review Letters on September 10.

The layout of the Large Hadron Collider complex at CERN. Protons (p) are pre-accelerated to higher energies in steps — at the Proton Synchrotron (PS) and then the Super Proton Synchrotron (SPS) — before being injected into the the LHC ring. The machine then draws two opposing beams of protons from the SPS and accelerates them to nearly the speed of light before colliding them head-on at four locations, under the gaze of the four detectors. ATLAS and CMS are two of them. Credit: Arpad Horvath (CC BY-SA)

The challenge of finding longitudinally polarised W bosons is like finding a particular needle in a very large haystack where most of the needles look nearly identical. So ATLAS designed a special strategy.

When one W boson decays, the result is one electron or muon and one neutrino. If the W boson is positively charged, for example, the decay could be to one anti-electron and one electron-neutrino or to one anti-muon and a muon-neutrino. Anti-electrons and anti-muons are positively charged. If the W boson is negatively charged, the products could one electron and one electron-antineutrino or one muon and one muon-antineutrino. So first, ATLAS zeroed in on the fact that it was looking for two electrons, two muons, or one of each, both carrying the same electric charge. Neutrinos however are really hard to catch and study, so the ATLAS group look for their absence rather than their presence. In all these particle interactions, the law of conservation of momentum holds — which means in a given interaction, a neutrino’s presence can be elucidated when the momenta of the electrons or muons add up to be slightly lower than that of the W boson; the missing amount would have been carried away by the neutrino, like money unaccounted for in a ledger.

This analysis also required an event of interest to have at least two jets (reconstructed from streams of particles) with a combined energy above 500 GeV and separated widely in rapidity (which is a measure of their angle relative to the beam). This particular VBS pattern — two electrons/muons, two jets, and missing momentum — is the hallmark of same-sign WW scattering.

Second, even with these strict requirements, impostors creep in. The biggest source of confusion is WZ production, a process in which another subatomic particle called the Z boson decays invisibly or one of its decay products goes unnoticed, making the event resemble WW scattering. Other sources include electrons having their charges mismeasured, jets can masquerading as electrons/muons, and some quarks producing electrons/muons that slip into the sample. To control for all this noise, the ATLAS group focused on control regions: subsets of events that produced a distinct kind of noise that the group could cleanly ‘subtract’ from the data to reveal same-sign WW scattering, thus also reducing uncertainty in the final results.

Third, and this is where things get nuanced: the differences between transverse and longitudinally polarised W bosons show up in distributions — i.e. how far apart the electrons/muons are in angle, how the jets are oriented, and the energy of the system. But since no single variable could tell the whole story, the ATLAS group combined them using deep neural networks. These machine-learning models were fed up to 20 kinematic variables — including jet separations, particle angles, and missing momentum patterns — and trained to distinguish between three groups:

(i) Two transverse polarised W bosons;

(ii) One transverse polarised W boson and one longitudinally polarised W boson; and

(iii) Both longitudinally polarised W bosons

Fourth, the group combined the outputs of these neural networks and fit with a maximum likelihood method. When physicists make measurements, they often don’t directly see what they’re measuring. Instead, they see data points that could have come from different possible scenarios. A likelihood is a number that tells them how probable the data is in a given scenario. If a model says “events should look like this,” they can ask: “Given my actual data, how likely is that?” And the maximum likelihood method will help them decide the parameters that make the given data most likely to occur.

For example, say you toss a coin 100 times and get 62 heads. You wonder: is the coin fair or biased? If it’s fair, the chance of exactly 62 heads is small. If the coin is slightly biased (heads with probability 0.62), the chance of 62 heads is higher. The maximum likelihood estimate is to pick the bias, or probability of heads, that makes your actual result most probable. So here the method would say, “The coin’s bias is 0.62” — because this choice maximises the likelihood of seeing 62 heads out of 100.

In their analysis, the ATLAS group used the maximum likelihood method to check with the LHC data ‘preferred’ a contribution from longitudinal scattering, after subtracting what background noise and transverse-only scattering could explain.

The results are a milestone in experimental particle physics. In the September 10 paper, ATLAS reported evidence for longitudinally polarised W bosons in same-sign WW scattering with a significance of 3.3 sigma — sufficiently close to 4, which is the calculated significance based on the predictions of the Standard Model. This means the data behaved as theory predicted, with no unexpected excess or deficit.

It’s also bad news for technicolor theory. By observing longitudinal W bosons at exactly the rates predicted by the Standard Model, and not finding any additional signals, the ATLAS data strengthens the case for the Higgs mechanism providing the check on the W bosons’ scattering probability, rather than the technicolor force.

The measured cross-section for events with at least one longitudinally polarised W boson was 0.88femtobarns, with an uncertainty of 0.3 femtobarns. These figures essentially mean that there were only a few hundred same-sign WW scattering events in the full dataset of around 10 quadrillion proton-proton collisions. The fact that ATLAS could pull this signal out of such a background-heavy environment is a testament to the power of modern machine learning working with advanced statistical methods.

The group was also able to quantify the composition of signals. Among others:
1. About 58% of events were genuine WW scattering
2. Roughly 16% were from WZ production
3. Around 18% arose from irrelevant electrons/muons, charge misidentification or the decay of energetic photons
One way to appreciate the importance of these findings is by analogy: imagine trying to hear a faint melody being played by a single violin in the middle of a roaring orchestra. The violin is the longitudinal signal; the orchestra is the flood of background noise. The neural networks are like sophisticated microphones and filters, tuned to pick out the violin’s specific tone. The fact that ATLAS couldn’t only hear it but also measured its volume to match the score written by the Standard Model is remarkable.

Perhaps in the same vein, these results are more than just another tick mark for the Standard Model. It’s a direct test of the Higgs mechanism in action. The discovery of the Higgs boson particle in 2012 was groundbreaking but proving that the Higgs mechanism performs its theoretical role requires demonstrating that it regulates the scattering of W bosons. By finding evidence for longitudinally polarised W bosons at the expected rate, ATLAS has done just that.

The results also set the stage for the future. The LHC is currently being upgraded to a form called the High-Luminosity LHC and it will begin operating later this decade, collect datasets about 10x larger than what the LHC did in its second run. With that much more data, physicists will be able to study differential distributions, i.e. how the rate of longitudinal scattering varies with energy, angle or jet separation. These patterns are sensitive to hitherto unknown particles and forces, such as additional Higgs-like particles or modifications to the Higgs mechanism itself. That is, even small deviations from the Standard Model’s predictions could hint at new frontiers in particle physics.

Indeed, history has often reminded physicists that such precision studies often uncover surprises. Physicists didn’t discover neutrino oscillations by finding a new particle but by noticing that the number of neutrinos arriving from the Sun at detectors on Earth didn’t match expectations. Similarly, minuscule mismatches between theory and observations in the scattering of W bosons could someday reveal new physics — and if they do, the seeds will have been planted by studies like that of the ATLAS group.

Challenging the neutrino signal anomaly

On the methodological front, the analysis also showcases how particle physics is evolving. ‘Classical’ analyses once banked on tracking single variables; now, deep learning has played a starring role by combining many variables into a single discriminant, allowing ATLAS to pull the faint signal of longitudinally polarised W bosons from the noise. This approach could only become more important as both datasets and physicists’ ambitions expand.

Perhaps the broadest lesson in all this is that science often advances by the unglamorous task of verifying the details. The discovery of the Higgs boson answered one question but opened many others; among them, measuring how it affects the scattering of W bosons is one of the ore direct ways to probe whether the Standard Model is complete or just the first chapter of a longer story. Either way, the pursuit exemplifies the spirit of checking, rechecking, testing, and probing until scientists truly understand how nature works at extreme precision.

Featured image: The massive mural of the ATLAS detector at CERN painted by artist Josef Kristofoletti. The mural is located at the ATLAS Experiment site and shows on two perpendicular walls the detector with a collision event superimposed. The event on the large wall shows a simulation of an event that would be recorded in ATLAS if a Higgs boson was produced. The cavern of the ATLAS Experiment with the detector is 100 m directly below the mural. The height of the mural is about 12 m. The actual ATLAS detector is more than twice as big. Credit: Claudia Marcelloni, Michael Barnett/CERN.
Sep 12, 2025
Peter Higgs, self-promoter

I was randomly rewatching The Big Bang Theory on Netflix today when I spotted this gem:

Okay, maybe less a gem and more a shiny stone, but still. The screenshot, taken from the third episode of the sixth season, shows Sheldon Cooper mansplaining to Penny the work of Peter Higgs, whose name is most famously associated with the scalar boson the Large Hadron Collider collaboration announced the discovery of to great fanfare in 2012.

My fascination pertains to Sheldon’s description of Higgs as an “accomplished self-promoter”. Higgs, in real life, is extremely reclusive and self-effacing and journalists have found him notoriously hard to catch for an interview, or even a quote. His fellow discoverers of the Higgs boson, including François Englert, the Belgian physicist with whom Higgs won the Nobel Prize for physics in 2013, have been much less media-shy. Higgs has even been known to suggest that a mechanism in particle physics involving the Higgs boson should really be called the ABEGHHK’tH mechanism, include the names of everyone who hit upon its theoretical idea in the 1960s (Philip Warren Anderson, Robert Brout, Englert, Gerald Guralnik, C.R. Hagen, Higgs, Tom Kibble and Gerardus ‘t Hooft) instead of just as the Higgs mechanism.

No doubt Sheldon thinks Higgs did right by choosing not to appear in interviews for the public or not writing articles in the press himself, considering such extreme self-effacement is also Sheldon’s modus of choice. At the same time, Higgs might have lucked out and be recognised for work he conducted 50 years prior probably because he’s white and from an affluent country, both of which attributes nearly guarantee fewer – if any – systemic barriers to international success. Self-promotion is an important part of the modern scientific endeavour, as it is with most modern endeavours, even if one is an accomplished scientist.

All this said, it is notable that Higgs was also a conscientious person. When he was awarded the Wolf Prize in 2004 – a prestigious award in the field of physics – he refused to receive it in person in Jerusalem because it was a state function and he has protested Israel’s war against Palestine. He was a member of the Campaign for Nuclear Disarmament until the group extended its opposition to nuclear power as well; then he resigned. He also stopped supporting Greenpeace after they become opposed to genetic modification. If it is for these actions that Sheldon deemed Higgs an “accomplished self-promoter”, then I stand corrected.

Featured image: A portrait of Peter Higgs by Lucinda Mackay hanging at the James Clerk Maxwell Foundation, Edinburgh. Caption and credit: FF-UK/Wikimedia Commons, CC BY-SA 4.0.

Feb 19, 2020
Tom Kibble (1932-2016)

Featured image: From left to right: Tom Kibble, Gerald Guralnik, Richard Hagen, François Englert and Robert Brout. Credit: Wikimedia Commons.

Sir Tom Kibble passed away on June 2, I learnt this morning with a bit of sadness that I’d missed the news. It’s hard to write about someone in a way that prompts others either to find out more about that person or, if they knew him or his work, to recall their memories of him when I myself would like only to do the former now. So let me quickly spell out why I think you should pay attention: Kibble was one of the six theorists who, in 1964, came up with the ABEGHHK’tH mechanism to explain how gauge bosons acquired mass. The ‘K’ in those letters stands for ‘Kibble’. However, we only remember that mechanism with the second ‘H’, which stands for Higgs; the other letters fell off for reasons not entirely clear – although convenience might’ve played a role. And while everyone refers to the mechanism as the Higgs mechanism, Peter Higgs, the man himself, continues to call it the ABEGHHK’tH mechanism.

Anyway, Kibble was known for three achievements. The first was to co-formulate – alongside Gerald Guralnik and Richard Hagen – the ABEGHHK’tH mechanism. It was validated in early 2013, earning only Higgs and ‘E’, François Englert, the Nobel Prize for physics that year. The second came in 1967, to explain how the mechanism accords the W and Z bosons, the carriers of the weak nuclear force, with mass but not the photons. The solution was crucial to validate the electroweak theory, and whose three conceivers (Sheldon Glashow, Abdus Salam and Steven Weinberg) won the Nobel Prize for physics in 1979. The third was the postulation of the Kibble-Żurek mechanism, which explains the formation of topological defects in the early universe by applying the principles of quantum mechanics to cosmological objects. This work was done alongside the Polish-American physicist Wojciech Żurek.

I spoke to Kibble once, only for a few minutes, at a conference at the Institute of Mathematical Sciences, Chennai, in December 2013 (at the same conference where I met George Sterman as well). This was five months after Fabiola Gianotti had made the famous announcement at CERN that the LHC had found a particle that looked like the Higgs boson. I’d asked Kibble what he made of the announcement, and where we’d go from here. He said, as I’m sure he would’ve a thousand times before, that it was very exciting to be proven right after 50 years; that it’d definitively closed one of the biggest knowledge gaps in modern theoretical particle physics; and that there was still work to be done by studying the Higgs boson for more clues about the nature of the universe. He had to rush; a TV crew was standing next to me, nudging me for some time with him. I was glad to see it was Puthiya Thalaimurai, a Tamil-language news channel, because it meant the ‘K’ had endured.

Rest in peace, Tom Kibble.

Jun 11, 2016
“Maybe the Higgs boson is fictitious!”

That’s an intriguing and, as he remarks, plausible speculation by the noted condensed-matter physicist Philip Warren Anderson. It appears in a short article penned by him in Nature Physics on January 26, in which he discusses how the Higgs mechanism as in particle physics was inspired by a similar phenomenon observed in superconductors.

According to the Bardeen-Cooper-Schrieffer theory, certain materials lose their resistance to the flow of electric current completely and become superconductors below a critical temperature. Specifically, below this temperature, electrons don’t have the energy to sustain their mutual Coulomb repulsion. Instead, they experience a very weak yet persistent attractive force between them, which encourages them to team up in pairs called Cooper pairs (named for Leon Cooper).

If even one Cooper pair is disrupted, all Cooper pairs in the superconductor will break, and it will cease to be a superconductor as well. As a result, the energy to break one pair is equivalent to the energy necessary to break all pairs – a coercive state of affairs that keeps the pairs paired up despite energetic vibrations from the atoms in the material’s lattice. In this energetic environment, the Cooper pairs all behave as if they were part of a collective (described as a Bose-Einstein condensate).

This transformation can be understood as the spontaneous breaking of a symmetry: the gauge symmetry of electromagnetism, which dictates that no experiment can distinguish between the laws governing electricity and magnetism. With a superconductor, however, the laws governing electricity in the material become different below the critical temperature. And when a gauge symmetry breaks, a massive¹ boson is formed. In the case of BCS superconductivity, however, it is not an actual particle as much as the collective mode of the condensate.

In particle physics, a similar example exists in the form of electroweak symmetry breaking. While we are aware of four fundamental forces in play around us (strong, weak, electromagnetic and gravitational), at higher energies the forces are thought to become unified into one ‘common’ force. And on the road to unification, the first to happen is of the electromagnetic and weak forces – into the electroweak force. Axiomatically, the electroweak symmetry was broken to yield the electromagnetic and weak forces, and the massive Higgs boson.

Anderson, who first discussed the ‘Higgs mode’ in superconductors in a paper in 1958, writes in his January 26 article (titled Higgs, Anderson and all that),

… Yoichiro Nambu, who was a particle theorist and had only been drawn into our field by the gauge problem, noticed in 1960 that a BCS-like theory could be used to create mass terms for massless elementary particles out of their interactions. After all, one way to describe the energy gap in BCS is that it represents a mass term for every point on the Fermi surface, mixing the particle with its opposite spin and momentum antiparticle. In 1960 Nambu and Jona-Lasinio developed a theory in which most of the mass of the nucleon comes from interactions — this theory is still considered partially correct.

But the real application of the idea of a superconductivity-like broken symmetry as a source of the particle spectrum came with the electroweak theory — which unified the electromagnetic and weak interactions — of Sheldon Glashow, Abdus Salam and Steven Weinberg.

What is fascinating is that these two phenomena transpire at outstandingly different energy scales. The unification of the electromagnetic and weak forces into the electroweak force happens beyond 100 GeV. The energy scale at which the electrons in magnesium diboride become superconducting is around 0.002 eV. As Terry Pratchett would have it, the “aching gulf” of energy in between spans 12 orders of magnitude.

At the same time, the parallels between superconductivity and electroweak symmetry breaking are more easily drawn than between other, more disparate fields of study because their occurrence is understood in terms of the behavior of fundamental particles, especially bosons and fermions. It is this equivalence that makes Anderson’s speculative remark more attractive:

If superconductivity does not require an explicit Higgs in the Hamiltonian to observe a Higgs mode, might the same be true for the 126 GeV mode? As far as I can interpret what is being said about the numbers, I think that is entirely plausible. Maybe the Higgs boson is fictitious!

To help us along, all we have at the moment is the latest in an increasingly asymptotic series of confirmations: as reported by CERN, “the results draw a picture of a particle that – for the moment – cannot be distinguished from the Standard Model predictions for the Higgs boson.”

¹Massive as in having mass, not as in a giant boson.

Feb 7, 2015
Would you just calm down about the Bose in the boson?

July, 2012 – A Higgs boson-like entity is spotted at the Large Hadron Collider. Indians decry the lack of celebration of S.N. Bose, the Bengali physicist whom bosons are named for.

January, 2013 – The particle found at the LHC is confirmed to be a Higgs boson. Further outcry about S.N. Bose having been forgotten in favor of the “Western” intellects.

October, 2013 – Peter Higgs and Francois Englert win the 2013 Nobel Prize in physics for their work on the Higgs mechanism. Bose is also in the limelight but for the same wrong reasons.

The word ‘boson’ was named for S.N. Bose not because he discovered bosons. It was named so by Paul Dirac, a Nobel Prize winning physicist, to honour Bose’s contribution to the Bose-Einstein statistics, work he did with Albert Einstein on defining the general properties of all bosons.

There are two kinds of particles in nature. Matter particles are the proverbial building blocks. They are the quarks and leptons, together called fermions. Force particles guide the matter particles around and help them interact with each others. They are the photons, W and Z bosons, gluons and the Higgs bosons.

In 1924, Bose and Einstein developed a theory to explain how a group of identical but non-interacting particles may occupy different energy states. They drew up a set of statistical rules and the particles that followed these rules did not obey Pauli’s exclusion principle. All such particles came to be called bosons.

Similarly, in 1926, Enrico Fermi and Paul Dirac came up with a set of rules for particles that did obey Pauli’s exclusion principle. While they worked on this theory independently, Fermi’s results were published first, leading to Dirac calling these particles fermions in the Italian giant’s honour.

So there. S.N. Bose – good man, great contribution – but he has nothing to do with the Higgs boson in particular except that this particle is a boson. What’s being celebrated about the Higgs is not being done in denial of Bose’s contributions because there is nothing to deny. The physics behind what’s going on now has more to do with how the hunt for one particular boson is shaping modern particle physics. Face it, the world of science has moved on.

If anything, I liked this Outlook article (except the last line) published a day after the momentous CERN announcements on July 4 last year. It brought S.N. Bose back into the limelight at a time when few of us in the country had (or have) the scientific temperament to acknowledge such contributions from history and, simply, recognise and preserve it for what it is: homage.

Indeed, some Indians seem to harbour a maleficient sense of entitlement that extends to calls demanding the ‘B’ in ‘bosons’ be capitalised. Rolf Dieter-Heuer, Director General of CERN, responded to this while at a meeting in Kolkata in September 2012: “I was asked yesterday why the boson was not capped. In Bose’s own city today, we have capped the Boson. I, in fact, always cap the Boson. But today, we changed all our CERN slides to cap Bosons.”

Another example of misguided entitlement was some Indian physicists saying that ‘naming the Higgs particle after Bose is an honour bigger than the Nobel Prize itself’. If you’re looking for honour of Indian origin in the Nobel Prize for physics in 2013, look to Indian scientists who worked on the collider.

Look to contributions from the Tata Institute of Fundamental Research and the Institute of Mathematical Sciences. Look to the superconducting magnets technology that India provided. Look to people like Rohini Godbole, Kajari Mazumdar (see slide 4), and Ashoke Sen.

But if all you want to do is cling to the vestiges of a legacy you helped fade, then you’re also doomed, benumbed to the sting of being denied the Nobel Prizes only because you’re not producing and retaining Nobel-class thinkers anymore.

(This blog post first appeared at The Copernican on October 10, 2013.)

Oct 10, 2013
The travails of science communication

There’s an interesting phenomenon in the world of science communication, at least so far as I’ve noticed. Every once in a while, there comes along a concept that is gaining in research traction worldwide but is quite tricky to explain in simple terms to the layman.

Earlier this year, one such concept was the Higgs mechanism. Between December 13, 2011, when the first spotting of the Higgs boson was announced, and July 4, 2012, when the spotting was confirmed as being the piquingly-named “God particle”, the use of the phrase “cosmic molasses” was prevalent enough to prompt an annoyed (and struggling-to-make-sense) Daniel Sarewitz to hit back on Nature. While the article had a lot to say, and a lot more waiting there to just to be rebutted, it did include this remark:

If you find the idea of a cosmic molasses that imparts mass to invisible elementary particles more convincing than a sea of milk that imparts immortality to the Hindu gods, then surely it’s not because one image is inherently more credible and more ‘scientific’ than the other. Both images sound a bit ridiculous. But people raised to believe that physicists are more reliable than Hindu priests will prefer molasses to milk. For those who cannot follow the mathematics, belief in the Higgs is an act of faith, not of rationality.

Sarewitz is not wrong in remarking of the problem as such, but in attempting to use it to define the case of religion’s existence. Anyway: In bridging the gap between advanced physics, which is well-poised to “unlock the future”, and public understanding, which is well-poised to fund the future, there is good journalism. But does it have to come with the twisting and turning of complex theory, maintaining only a tenuous relationship between what the metaphor implies and what reality is?

The notion of a “cosmic molasses” isn’t that bad; it does get close to the original idea of a pervading field of energy whose forces are encapsulated under certain circumstances to impart mass to trespassing particles in the form of the Higgs boson. Even this is a “corruption”, I’m sure. But what I choose to include or leave out makes all the difference.

The significance of experimental physicists having probably found the Higgs boson is best conveyed in terms of what it means to the layman in terms of his daily life and such activities more so than trying continuously to get him interested in the Large Hadron Collider. Common, underlying curiosities will suffice to to get one thinking about the nature of God, or the origins of the universe, and where the mass came from that bounced off Sir Isaac’s head. Shrouding it in a cloud of unrelated concepts is only bound to make the physicists themselves sound defensive, as if they’re struggling to explain something that only they will ever understand.

In the process, if the communicator has left out things such as electroweak symmetry-breaking and Nambu-Goldstone bosons, it’s OK. They’re not part of what makes the find significant for the layman. If, however, you feel that you need to explain everything, then change the question that your post is answering, or merge it with your original idea, etc. Do not indulge in the subject, and make sure to explain your concepts as a proper fiction-story: Your knowledge of the plot shouldn’t interfere with the reader’s process of discovery.

Another complex theory that’s doing the rounds these days is that of quantum entanglement. Those publications that cover news in the field regularly, such as R&D mag, don’t even do as much justice as did SciAm to the Higgs mechanism (through the “cosmic molasses” metaphor). Consider, for instance, this explanation from a story that appeared on November 16.

Electrons have a property called “spin”: Just as a bar magnet can point up or down, so too can the spin of an electron. When electrons become entangled, their spins mirror each other.

The causal link has been omitted! If the story has set out to explain an application of quantum entanglement, which I think it has, then it has done a fairly good job. But what about entanglement-the-concept itself? Yes, it does stand to lose a lot because many communicators seem to be divesting of its intricacies and spending more time explaining why it’s increasing in relevance in modern electronics and computation. If relevance is to mean anything, then debate has to exist – even if it seems antithetical to the deployment of the technology as in the case of nuclear power.

Without understanding what entanglement means, there can be no informed recognition of its wonderful capabilities, there can be no public dialog as to its optimum use to further public interests. When when scientific research stops contributing to the latter, it will definitely face collapse, and that’s the function, rather the purpose, that sensible science communication serves.

Nov 17, 2012
Signs of a slowdown

The way ahead for particle physics seems dully lit after CERN’s fourth-of-July firecracker. The Higgs announcement got everyone in the physics community excited – and spurred a frenzied submission of pre-prints all rushing to explain the particle’s properties. However, that excitement quickly died out after ICHEP ’12 was presented with nothing significant, even with anything a fraction as significant as the ATLAS/CMS results.

(L-R) Gianotti, Heuer & Incandela

Even so, I suppose we must wait at least another 3 months before a a conclusive Higgs-centric theory emerges that completely integrates the Higgs mechanism with the extant Standard Model.

The spotting of the elusive boson – or an impostor – closes a decades-old chapter in particle physics, but does almost nothing in pointing the way ahead apart from verifying the process of mass-formation. Even theoretically, the presence of SM quadratic divergences in the mass of the Higgs boson prove a resilient barrier to correct. How the Higgs field will be used as a tool in detecting other particles and the properties of other entities is altogether unclear.

The tricky part lies in working out the intricacies of the hypotheses that promise to point the way ahead. The most dominant amongst them is supersymmetry (SUSY). In fact, hints of existence of supersymmetric partners were recorded when the LHCb detector at the LHC spotted evidence of CP-violation in muon-decay events (the latter at 3.9σ). At the same time, the physicists I’m in touch with at IMS point out that rigid restrictions have been instituted on the discovery of sfermions and bosinos.

The energies at which these partners could be found are beyond those achievable by the LHC, let alone the luminosity. More, any favourable-looking ATLAS/CMS SUSY-results – which are simply interpretations of strange events – are definitely applicable only in narrow and very special scenarios. Such a condition is inadmissible when we’re actually in the hunt for frameworks that could explain grander phenomena. Like the link itself says,

“The searches leave little room for SUSY inside the reach of the existing data.”

Despite this bleak outlook, there is still a possibility that SUSY may stand verified in the future. Right now: “Could SUSY be masked behind general gauge mediation, R-parity violation or gauge-mediated SUSY-breaking” is the question (gauge-mediated SUSY-breaking (GMSB) is when some hidden sector breaks SUSY and communicates the products to the SM via messenger fields). Also, ZEUS/DESY results (generated by e-p DIS studies) are currently being interpreted.

However, everyone knows that between now and a future that contains a verified-SUSY, hundreds of financial appeals stand in the way. 😀 This is a typical time of slowdown – a time we must use for open-minded hypothesizing, discussion, careful verification, and, importantly, honest correction.

Jul 17, 2012
The philosophies in physics

As a big week for physics comes up–a July 4 update by CERN on the search for the Higgs boson followed by ICHEP ’12 at Melbourne–I feel really anxious as a small-time proto-journalist and particle-physics-enthusiast. If CERN announces the discovery of evidence that rules out the existence of such a thing as the Higgs particle, not much will be lost apart from years of theoretical groundwork set in place for the post-Higgs universe. Physicists obeying the Standard Model will, to think the snowclone, scramble to their boards and come up with another hypothesis that explains mass-formation in quantum-mechanical terms.

For me… I don’t know what it means. Sure, I will have to unlearn the Higgs mechanism, which does make a lot of sense, and scour through the outpouring of scientific literature that will definitely follow to keep track of new directions and, more fascinatingly, new thought. The competing supertheories–loop quantum gravity (LQG) and string theory–will have to have their innards adjusted to make up for the change in the mechanism of mass-formation. Even then, their principle bone of contention will remain unchanged: whether there exists an absolute frame of reference. All this while, the universe, however, will have continued to witness the rise and fall of stars, galaxies and matter.

It is easier to consider the non-existence of the Higgs boson than its proven existence: the post-Higgs world is dark, riddled with problems more complex and, unsurprisingly, more philosophical. The two theories that dominated the first half of the previous century, quantum mechanics and special relativity, will still have to be reconciled. While special relativity holds causality and locality close to its heart, quantum mechanics’ tendency to violate the latter made it disagreeable at the philosophical level to A. Einstein (in a humorous and ironical turn, his attempts to illustrate this “anomaly” numerically opened up the field that further made acceptable the implications of quantum mechanics).

The theories’ impudent bickering continues with mathematical terms as well. While one prohibits travel at the speed of light, the other allows for the conclusive demonstration of superluminal communication. While one keeps all objects nailed to one place in space and time, the other allows for the occupation of multiple regions of space at a time. While one operates in a universe wherein gods don’t play with dice, the other can exist at all only if there are unseen powers that gamble on a secondly basis. If you ask me, I’d prefer one with no gods; I also have a strange feeling that that’s not a physics problem.

Speaking of causality, physicists of the Standard Model believe that the four fundamental forces–nuclear, weak, gravitational, and electromagnetic–cause everything that happens in this universe. However, they are at a loss to explain why the weak force is 10³²-times stronger than the gravitational force (even the finding of the Higgs boson won’t fix this–assuming the boson exists). An attempt to explain this anomaly exists in the name of supersymmetry (SUSY) or, together with the Standard Model, MSSM. If an entity in the (hypothetical) likeness of the Higgs boson cannot exist, then MSSM will also fall with it.

Taunting physicists everywhere all the way through this mesh of intense speculation, Werner Heisenberg’s tragic formulation remains indefatigable. In a universe in which the scale at which physics is born is only hypothetical, in which energy in its fundamental form is thought to be a result of probabilistic fluctuations in a quantum field, determinism plays a dominant role in determining the future as well as, in some ways, contradicting it. The quantum field, counter-intuitively, is antecedent to human intervention: Heisenberg postulated that physical quantities such as position and particle spin come in conjugate quantities, and that making a measurement of one quantity makes the other indeterminable. In other words, one cannot simultaneously know the position and momentum of a particle, or the spins of a particle around two different axes.

To me, this seems like a problem of scale: humans are macroscopic in the sense that they can manipulate objects using the laws of classical mechanics and not the laws of quantum mechanics. However, a sense of scale is rendered incontextualizable when it is known that the dynamics of quantum mechanics affect the entire universe through a principle called the collapse postulate (i.e., collapse of the state vector): if I measure an observable physical property of a system that is in a particular state, I subject the entire system to collapse into a state that is described by the observable’s eigenstate. Even further, there exist many eigenstates for collapsing into; which eigenstate is “chosen” depends on its observation (this is an awfully close analogue to the anthropic principle).

xkcd #45

That reminds me. The greatest unsolved question in my opinion is whether the universe houses the brain or if the brain houses the universe. To be honest, I started writing this post without knowing how it would end: there were multiple eigenstates it could “collapse” into. That it would collapse into this particular one was unknown to me, too, and, in hindsight, there was no way I could have known about any aspect of its destiny. Having said that, the nature of the universe–and the brain/universe protogenesis problem–with the knowledge of deterministic causality and mensural antecedence, if the universe conceived the brain, the brain must inherit the characteristics of the universe, and therefore must not allow for freewill.

Now, I’m faintly depressed. And yes, this eigenstate did exist in the possibility-space.

Jul 1, 2012