What Is Fundamental In Physics?

This is a question and my answer from the Physics Forums (officially written at the graduate school level, but dumbed down since the question indicates that the person asking isn't actually that sophisticated and knowledgable. The question is in a block quote, but my answer is not, for ease of reading.

Wiktorius I said:

TL;DR: Does physics establish that mass, particles, and fields are fundamental, or could they be emergent properties of a deeper physical structure?

Are mass, particles, and fields fundamental physical entities, or could they be observable consequences of a deeper physical structure? I am particularly interested in what experimental evidence allows us to distinguish between these possibilities.They aren't necessarily fundamental, but we have no real idea what kind of deeper physical structure could cause what we see and there are no experiments or observations that are likely to take place in the next few decades that can tell us.

Generally, going as deep as we possibly can, we think of particles in the context of an effective field theory as local excitations of fields.

But, most popular accounts, because it is more intuitive to understand, talk in terms of particles, with fermions corresponding to what we think of as matter in a colloquial sense, and bosons corresponding to "force fields" for the fundamental forces of the Standard Model.

Generally speaking, the mass of particles (both fundamental and composite) is not understood as fundamental. Massive Standard Model fundamental particles like electrons, muons, tau leptons, and quarks and W bosons and Z bosons and the Higgs boson (with the probable exception of the neutrinos whose mechanism for acquiring mass isn't well understood at this point) get their mass from their interactions with the Higgs field. Massive composite particles (like protons and neutrons) get their mass from a combination of the masses of the fundamental Standard Model particles that they are made up of (to a small extent) and from the energy of the gluon fields that bind them together (to a great extent). But the sometimes elusive concept of mass-energy is something that is fundamental and conserved.

There is no real consensus over whether gravity is something that arises from the exchange of massless spin-2 gravitons (which are bosons) in a way analogous to the way that electromagnetism arises from the exchange of massless spin-1 photons, or whether gravity is a property of space-time itself which is either classical and smooth, or as in the quantum gravity approach of loop quantum gravity, in which case space-time itself is discrete at some ultra-fine scale.

There is no consensus on this because we don't have any observational tools sufficiently powerful to distinguish between the hypotheses, and because while the math behind classical general relativity is hard, we haven't cracked the math behind quantum gravity theories of various kinds outside some very specific isolated cases in theories that don't hold true for all circumstances and have internal mathematical issues with them that make quantum gravity theories in the general case intractable.

We don't have any well accepted theories that explain why the couple dozen plus experimentally measured physical constants of the Standard Model plus general relativity have the values that they do, although electroweak theory does establish that a few of the Standard Model physical constants are not actually mathematically independent of each other, so the number of independent degrees of freedom in the experimentally measured physical constants of the Standard Model is a few less than the number of experimentally measured physical constants (e.g. the electromagnetic coupling constant, weak force coupling constant, W boson mass, and Z boson mass are related to each other by a formula which has fewer than four independent degrees of freedom).

There are some theories out there that go part of the way, providing a road map for possible ways to explain more of the experimentally measured physical constants of the Standard Model and general relativity. But while these are bit more than speculative, none of them are established in a settled way that can secure a scientific consensus or anything close to that. Moreover, as impressive as our scientific methods are, imprecision in measuring some of these experimentally measured physical constants limits the degree to which we can distinguish one explanation for their values from another. Many key physical constants are measured only to percent or part per thousand levels.

But the failure of scientists so far to find any meaningful deviations from the Standard Model in particle accelerator experiments and other terrestrial tests of it (like ultra-precise measurements of the anomalous magnetic moment of the muon) profoundly constrains any alternatives that would predict anything experimentally different from what the Standard Model predicts.

I can't recall ever meeting a physicist who thinks that there isn't some deeper theory that could explain why those physical constants have the values that they do. But most physicists, having seen the parade of physicists before them who have failed to find that deeper theory, are content to not go looking for it very seriously.

As a practical matter, even if you found the deeper theory that explained why most of those physical constants have the values that they do, it wouldn't necessary change much for most physicists, because we've already measured those physical constants to high precision in most of the cases where precise values are important to precise calculations. Having the deeper theory might allow you to assign more precise values to the physical constants whose values are hardest to measure, which would be a helpful thing on the margins as a practical matter and very personally satisfying, but that might be just about it.

Of course, if we knew why those physical constants had the values that they do, we would probably also rule out all sorts of beyond the Standard Model theories and models in a way that would be more satisfying than the way that we do now. But it wouldn't have many very practical consequences.

There are a variety of reasons why the most naively obvious alternative to the list of Standard Model particles being fundamental, which would be that they are composite particles of a smaller number of more fundamental particles (generically called preons), is unlikely to be an explanation. The reasons are a bit technical (e.g. the binding energy necessary for this to be the case is too great to be consistent with the hypothesis), but the consensus is that this is pretty much a dead end.

String theory, at first, seemed to be another path to a more fundamental explanation of the laws of nature than the Standard Model plus general relativity (which aren't themselves compatible with each other which implies that one or the other or both aren't truly fundamental) but this research agenda in the many decades since it was first introduced has turned out to be a quagmire that even many of its leading theorists don't claim is an accurate description of the world we actually live in, even though the things we learned along the way investigating it may have value.

So, while our core theories, the Standard Model and general relativity, probably aren't the most fundamental and complete explanations of the laws of nature that are possible, we really have no solid leads on alternatives.

Perhaps the most promising area where we might gain a better understanding is from astronomy where ill-understood concepts summarized as dark matter and dark energy might be better understood with more observational astronomy evidence. But we are far from reaching a consensus understanding of them, and are less confident about the baseline explanation of them called Lambda CDM (for cold dark matter) theory now than we have been since Lambda CDM was formulated.

The prospects for something more fundamental didn't always seem so bleak. In the late 1980s and early 1990s, a group of theories called "supersymmetry" and their gravitational extension, "supergravity" looked very promising. It would have explained many of the fundamental constants in an overall framework (although not all of them), it would have provided a path to unifying the Standard Model coupling constants at higher energies into a single force, it would have provided a candidate for dark matter particles that was sufficient to fit the astronomy and particle physics data available at the time, there was no evidence that the cosmological constant wasn't constant, it would have provided a bridge between the Standard Model and string theory, and a path to a workable theory of quantum gravity.

But bit by bit, that fell apart. Supersymmetry predicted particles with well defined properties, but when particle collider scientists looked for those predicted particles they weren't were they were assumed to be. Better data showed that the Standard Model coupling constants weren't on a path to converging at high energies. Better astronomy observations found that dark matter phenomena behaved differently than it would have if the supersymmetry candidates were what explained it. Better astronomy observations found that the cosmological constant might not be constant after all. The discovery that neutrinos had mass complicated the situation and the failure to detect neutrinoless beta decay complicated one of the most elegant explanations of neutrino mass that might fit better into the supersymmetry/string theory framework. The math necessary for string theory and quantum gravity turned out to be much more problematic than early researchers in these fields had hoped or expected at a very fundamental level. Strong experimentally confirmed anomalies that would deviate from the Standard Model to prove that supersymmetry was correct, instead failed to materialize. The experimental anomalies that seemed to potentially support supersymmetry went away as theoretical predictions and experimental measurements grew more precise.

Supersymmetry isn't definitively ruled out yet, but any version of it that is discovered won't solve the problems that a large share of the physics community hoped and believed that it would in the late 1980s and early 1990s, before they had enough experimental data and mathematical understanding to realize that their beautiful solution to all of the unsolved problems in fundamental physics with a deeper theory wasn't going to hold together.

A generation or two later, we have bits and pieces of ideas - MOND, entropic gravity, axion-like ultralight dark matter particles, Koide's rule and extrapolations of it, multiple Higgs doublet theories, see saw theories of neutrino mass, and more. There are many more partial theories to explain one little thing that surfaced as an anomaly or possibility for a while that were later ruled out. But we have no real solid agenda for developing a deeper theory.

Who knows?

Maybe we're just a genius or three away from ending a period of non-consensus and confusion about a way forward and finding the deeper theories we need to explain the outstanding unsolved problems of fundamental physics. But I'm not that genius and there aren't a lot of good candidates among living physicists today for people who could be that genius.

POST SCRIPT (not in the original post):

It is notable that MOND and Koide's rule, two of the most successful enduring beyond the Standard Model theories, albeit both phenomenological only, both date to the early 1980s, before supersymmetry and string theory had become dominant trends in fundamental physics.

Neutrino physics

Neutrino mass was first discovered in 1998. This finding was replicated and confirmed in 2001. In 2015 Nobel prizes were awarded for the discovery that neutrinos are massive. Experimental determination of some of the parameters of neutrino oscillation (such as the CP violating phase) is still very crude and the absolute neutrino masses are still also not tightly established.

Supersymmetry and string theory advocates tend to strongly favor Majorana mass for neutrinos. The absolute masses of the neutrinos are still not known, only their mass differences. But there are strong hints from cosmology and from the magnitude of the mass differences, that neutrino masses are so small that we wouldn't expect to have observed definitive neutrinoless beta decay signals that would be proof of Majorana mass in neutrinos yet even if that was the source of neutrino mass. I personally find the hypothesis that neutrinos are their own antiparticles to be highly unlikely given that the main reason that they were hypothesized in the first place was to provide particle-antiparticle balance that conserves lepton number. There is a good chance that the bounds on absolute neutrino mass and the non-discovery of neutrinoless double beta decay will exclude a vanilla version of the Majorana mass hypothesis for neutrinos in my lifetime.

This said, I'm also not very impressed with see saw models, in which neutrinos have a Dirac mass arising from oscillations with one to three otherwise undetectable right handed neutrinos that are much more massive than their Standard Model active neutrino counterparts. 

The most plausible alternatives that I imagine, with only thin support from academic research, are that neutrinos either acquire their mass through a combination of their self-interactions via the weak force and their interactions with W bosons more generally, or acquire their mass through a second neutral scalar boson analogous to the Higgs boson.

More generally, I suspect that the role of the W boson in imparting mass to fundamental particles is underrated relative to the rule of the Higgs boson in doing so.

Higgs physics

The Higgs boson was discovered in 2012, although it was predicted about forty years earlier and efforts continue at the Large Hadron Collider (LHC), and in reanalysis of Tevatron collider data, to confirm that its properties are actually fully consistent with the Standard Model Higgs boson predicted in the early 1970s (so far no experimental data disproves this hypothesis and the extent to which it could deviate from that hypothesis is heavily constrained by the data that we do have). The measured mass of the Higgs boson according to the Particle Data Group, which is 125.11  ± 0.11 GeV/c², significantly constrains that parameter space of many supersymmetry (a.k.a. SUSY) theories.

One largely back burner issue is that a global electroweak fit would favor a Higgs boson mass of 90 + 21 -18 GeV/c², which is consistent at the two sigma level with the measured Higgs boson mass, but has a best fit value 1.7 sigma below the measured value which is still a bit puzzling.

There are exclusions of additional Higgs bosons (neutral, charged) proposed by some beyond the Standard Model theories, which the Particle Data Group also underplays, but which are indeed not quite as insurmountable as the exclusions for supersymmetric particles.

Supersymmetry

While supersymmetry papers are still being published, this line of beyond the Standard Model physics inquiry has greatly fallen out of favor from its heyday. A large share of physicists expected it to be discovered at the LHC but that didn't happen.

The Particle Data Group has a full page of supersymmetry exclusions from experiments, which in my humble opinion is too conservative. But it is a difficult set of experimental data points to present because many of the exclusions of model dependent. The three linked review articles on that page, however, are helpful.

The main reasons that supersymmetric particles are disfavored as dark matter candidates (called WIMPs) now are that: 

(1) direct dark matter detection experiments (such as Lux-Zepplin which detected a single first candidate for a direct dark matter detection signal earlier this month mostly like with a mass of about 1 TeV/c² which is six times the top quark mass and four times the mass of a uranium atom) imply a far smaller cross-section of interaction that the cross-section of interaction predicted by supersymmetry theories;

(2) galaxy dynamics (particularly the core-cusp problem) disfavor a dark matter candidate in the 1 TeV/c² or more mass range (even though plenty of preprints hypothesizing that the LZ candidate is a WIMP are out there) and really favor dark matter particle candidates in the 10 keV/c² or less mass range; and

(3) particle collider bounds on the minimum mass of supersymmetric particles that could plausibly be dark matter candidates are generally in the hundreds of GeV/c² or more range.

The consistency of the experimentally measured value of the anomalous magnetic moment of the muon (muon g-2) and the Standard Model predicted value of that quantity, strongly disfavors the existence of supersymmetry below very high energies. 

The SM Expectation For Higgs Boson Pair Production

A new study makes a state of the art prediction of the Higgs boson pair production rate from gluon fusion in the Standard Model. 

Some day when Higgs boson pair production experiments are about 1000 times more precise than they are today, this prediction can be compared to the experimental data, which is one way to determine is the Higgs boson self-coupling is consistent with the Standard Model prediction or if it instead has a value more consistent with a beyond the Standard Model value. 

Gluon fusion is one of the main mechanisms by which Higgs bosons and Higgs boson pairs are created, and combined with Standard Model predictions for the other possible mechanisms, can be compared to the actual experimentally observed rates of Higgs boson pair production at particle collider experiments.

Despite the lengths of many authors go to in order to make the calculation that considers all sorts of higher order corrections, however, the uncertainties are still large. 

But the experimental measurements currently aren't any better. They show that the actual rate of Higgs boson pair production is merely less than 2.4 times the Standard Model expectation (i.e. less than about 87.3 fb) with a 95% confidence interval. Higgs boson pair production rates are 0.06% of the overall Higgs boson production. In the Standard Model, Higgs boson pair production predominantly (90%) comes from the gluon fusion mechanism that the new study calculates considering all feasible to calculate factors.

Total Higgs boson production at 13 TeV is about 55.6 pb (+6% -8% uncertainties at one sigma) of which 48.4 (87% of the total) comes from gluon fusion with the remaining 7.2 pb coming from six other main production mechanisms. Higgs boson pair production at 13 TeV using a gluon fusion rate of 33 fb is 36.36 fb, of which 3.36 fb come from five other main non-gluon fusion production mechanisms. And, 1 picobarn (pb) = 1,000 femtobarns (fb).

This study (see below) concludes that double Higgs boson pair production at 13 TeV from gluon fusion is actually 30.4 fb (but subject to a roughly + 10% -23% uncertainty, so its is consistent with the earlier less exhaustively calculated result quoted in the Particle Data Group review below the fold which has roughly the same uncertainty on a percentage basis; the new result has a central value which is about 8% smaller than the old one). A ± 0.2 GeV change in the Higgs boson mass from 125.0 GeV shifts the predicted value by only about + 0.3% (if it is lighter) - 0.4% (if it is heavier), so the gluon fusion Higgs boson pair production rate isn't very sensitive to tweaks to the Higgs boson mass within the current range of uncertainty, but is probably a little bit less than 30.4 fb.

The paper and its abstract are as follows:

In this contribution, the higher-order QCD and electroweak corrections to Standard Model Higgs boson pair production via the gluon-fusion mechanism, gg→hh, are summarized and the different sources of theoretical uncertainty are assessed. The discussion includes finite top quark mass effects, matching to parton showers, approximate NNLO and N3LO QCD corrections, NLO electroweak effects, and uncertainties associated with the top quark mass scheme and perturbative scale choices. In addition, we provide an updated state-of-the-art recommendation for the inclusive gluon-fusion Higgs boson pair production cross section and the corresponding Higgs boson pair invariant-mass distribution.

Ajjath A H, et al., "Higgs Boson Pair Production via Gluon Fusion: Higher-Order Corrections and Theoretical Uncertainties" arXiv:2609.04868 (September 4, 2026) (Contribution to CERN Report 5 approved by LHC Higgs Working Group, Working Group 4 Report number LHCHWG-2026-010).

It concludes that:

Notably, while this prediction is sensitive to the Higgs boson mass, it is not sensitive enough to meaningfully distinguish Higgs boson masses experimentally because the differences due to the Higgs boson mass are smaller than the uncertainty in the prediction.

The conclusion explains:

This report has summarized the current status of precision predictions for Standard Model Higgs boson pair production via gluon fusion. The discussion brings together NLO QCD calculations with full top quark mass dependence, approximate NNLO QCD predictions, N3LO QCD corrections and soft-gluon resummation, NLO electroweak corrections, and details the main sources of theoretical uncertainty entering the theoretical prediction. 

The final recommendations provide state-of-the-art SM reference predictions for phenomenological studies and LHC analyses. They combine higher-order QCD (exact NLO, approximate NNLO and N3LO + N3LL) and EW (NLO) corrections, together with a full uncertainty budget. The combined inclusive cross sections, including the dominant uncertainty associated with the top-quark mass scheme, are collected in Table 12, while their dependence on the Higgs-boson mass is given in Table 13. Additionally we provide differential distributions in m(hh) (Section 7.5), along with corresponding K-factors from the higher-order calculations. These numbers should be used as the definitive predictions of this report, superseding the intermediate results shown in the preceding sections where different input parameters or PDF choices are used. It is worth noting that while the present work does not reduce the overall uncertainty with respect to the previous recommendation, its central prediction includes N3LO+N3LL QCD corrections in the HTL, NLO electroweak effects and updated PDF sets, and should therefore provide a more accurate reference value. 

Further improvements in the SM prediction will come from reducing uncertainties associated with finite top quark mass effects and mass-scheme choice, extending fully differential predictions with consistently combined higher-order QCD and electroweak effects, and updating the recommendations as parton distributions and input parameters evolve.

Background from the Particle Data Group (with somewhat icky formatting) appears below the fold. 

A Possible Glueball Resonance

A glueball is a strong force bound system without any valence quarks that binds gluons, the carrier bosons of the strong force instead of quarks. A well-established resonance seen in experiments at discovery level significance since 2011, whose internal structure is unclear, is shown in a new preprint to be consistent with a nearly pure pseudoscalar glueball state (i.e. a spin-0, electromagnetically neutral boson with odd parity and no valence quarks).

The properties of glueballs (which depend primarily on a single experimentally measured physical constant, the strong force coupling constant), have been calculated from the very early days of quantum chromodynamics (QCD), which is the Standard Model theory of the strong force. And, there are only a modest number of theoretically possible glueballs. This resonance is on the low end of, but consistent with, the mass predicted for a pseudoscalar glueball.

But distinguishing a glueball resonance from a non-glueball resonance is difficult, and because glueballs are always bosons and share quantum numbers with bosons that include valence quarks, they have a natural tendency to blend with similar bosons making a mere glueball component in a resonance rather than a pure glueball, something that is probably common in reality.

There have only been a few resonances that have been convincingly interpreted as a near pure glueball, and this is one of them. But the fact that this is an analysis of a lone author which has not yet been published in a peer reviewed journal bodes caution in accepting this conclusion as definitive. But to the extent that this analysis holds up, it confirms an important qualitative prediction of QCD (i.e. the existence of glueballs with various quantum numbers that have their predicted masses).

In this work, we take the X(2370) with J^PC = 0−+ as a glueball consists of three valence gluons, and construct a six-quark current based on rigorous current-field duality to obtain the glueball-quark Lagrangian. Then we perform Fierz transformation to bosonize the quark current into a series of three pseudoscalar mesons. At last, we obtain ratios among the partial decay widths of the glueball to three pseudoscalar mesons in a model-independent way, which are compatible with the experimental data from the BESIII Collaboration and support assigning the X(2370) as a glueball.

Zhi-Gang Wang, "Analysis of the X(2370) as a glueball based on rigorous current-field duality" arXiv:2608.03362 (August 4, 2026).

In other physics news, the Higgs boson continues to be consistent with Standard Model expectations in newly observed ways.

A New Higgs Boson Mass Measurement

Every new precision measurement of the Higgs boson mass is golden, and it is increasingly being pinned down to some precision.

A measurement of the Higgs boson mass in the diphoton decay channel is performed using proton-proton collision data at a center-of-mass energy of 13 TeV. The data set recorded with the CMS detector between 2016 and 2018 is used, corresponding to an integrated luminosity of 138 fb−1. A refined detector calibration and new analysis techniques are employed to improve the precision of the results compared to earlier measurements. The Higgs boson mass is measured to be mH = 125.13 ± 0.15 GeV = 125.13 ± 0.10 (stat) ± 0.12 (syst) GeV. 

In addition, a combination with the mass measurement at center-of-mass energies of 7 and 8 TeV in the diphoton final state is performed resulting in mH = 125.06 ± 0.14 GeV = 125.06 ± 0.09 (stat) ± 0.11 (syst) GeV.

CMS Collaboration, "A measurement of the Higgs boson mass in the diphoton decay channel in proton-proton collisions at s√ = 13TeV" arXiv:2607.28396 (July 30, 2026) (Submitted to Physics Letters B.).

This result compares to a Particle Data Group global average of 125.13 ± 0.11 GeV (S = 1.5).

The Latest Global Electroweak Fits Of Standard Model Physical Constants

A global electroweak fit combines experimentally measured values of Standard Model physical constants with the theoretical relationships between those constants in the electroweak sector of the Standard Model to determine where, within the range of uncertainties in the experimental measurements the true value of those physical constants is most likely to be. Basically, it uses theory to eke out a bit more precision in our determination of these constants than the measurements make possible in isolation.

The fact that it is possible with experimentally measured value of Standard Model physical constants without serious tensions (which it is) also provides a global test of the consistency of the Standard Model with reality.

The latest paper using up to date experimental data to make a global electroweak fit of Standard Model physical constants can be found here. The discussion of how the input values are chosen (basically, an educated best summary of the data to date) in the paper is also noteworthy.

The global fit of the Z boson mass is 91.1882 ± 0.0019 GeV and the global fit of the Z boson width is 2.4945 ± 0.0006 GeV.

The global fit of the W boson mass is 80.3584 ± 0.0048 GeV and the global fit of the W boson width is 2.090 ± 0.001 GeV.

The Higgs boson mass is 125.13 ± 0.11 GeV. The Standard Model expectation for the Higgs boson width is 4.10 ± 0.06 MeV; a complete global electroweak fit of the data produces 3.78 + 0.30 − 0.27 MeV, which is consistent with the Standard Model expectation. The couplings of the Higgs boson in an electroweak global fit are within roughly 1% ± 1% of the Standard Model expectation. 

The global fit of the charm quark pole mass (in the MS scheme) is 1.273 ± 0.003 GeV.

The global fit of the bottom quark pole mass (in the MS scheme) is 4.183 ± 0.004 GeV.

The global fit of the top quark pole mass is 172.67 ± 0.56 GeV.

The global fit of the strong force coupling constant at the Z boson squared energy scale is 0.1179 ± 0.0009.

The global fit of the effective leptonic weak mixing angle is sin^2(theta) = 0.23149 ± 0.00005.

The Modest Excess Higgs Boson Production Explained

The Standard Model is stochastic (i.e. probabilistic) and not deterministic. It doesn't say, if you do X then Y will happen. It says, if you do X, Y with happen Z percent of the time.

One of the many things that the Standard Model predicts is the Higgs boson production rate, as a probability distribution of the rate at which Higgs bosons are produced in given circumstances. The calculation is in the form of an infinite series of terms with leading order, next to leading order, next to next to leading order, etc. terms.

You haven't read much about the physics of Higgs boson production at this blog because its a lot less simple and intuitive than Higgs boson decays, which are much more straightforward and rely on simpler, less complicated processes and rules. This makes Higgs boson production harder to write good blog posts about than Higgs boson decays. Also, the experimental anomalies compared to Standard Model predictions for Higgs boson production have been less striking, with more uncertainty and not very striking discrepancies, even though the discrepancies in Higgs boson production rates have been quite persistent.

In practice, scientists calculate the Standard Model prediction for the Higgs production rate with as many terms as are practically feasible for them to calculate, and then they try to estimate the uncertainty arising from the omitted terms as best they can.

Usually, each slight incremental improvement in the accuracy of the calculation takes disproportionately more work to calculate than the amount of work that was necessary to make the previous improvement of that magnitude. 

But, now and then, scientists unexpectedly find a previous omitted term from their calculations that is really important, although figuring out which terms will be especially fruitful to include is still at a more art than science level right now. Research programs like the amplituhedron approach and related developments from it are trying to bring more science to that search, but we aren't quite there yet.

Experiments since 2012, when the Higgs boson was first discovered, have shown that Higgs production usually exceeds the rate calculated by the best available Standard Model prediction calculations, although either not by a statistically significant amount, or with only a mild statistical tension with the best available predicted value for the Standard Model Higgs boson production rate.

Initially, some scientists though that this could be because the Higgs boson was detected sooner than it would have been otherwise because of a statistical fluke of higher than expected Higgs production. At first, that was a plausible proposal.

But it has been 14 years now, so it probably wasn't that, because the slight bias towards higher the expected Higgs boson production rates hasn't completely gone away, as the sample size of Higgs bosons detected has surged and reduced statistical uncertainties (but not always systemic uncertainties in the measurements of the Higgs boson production rates). 

Of course, like every anomaly in high energy particle physics, some theorists have, instead, tried to explain this persistent, not very large anomaly, with beyond the Standard Model physics.

But, a new paper now explains most or all of what has been going on. It turns out that the Higgs boson that physicists have observed is behaving more like than Standard Model Higgs boson to higher precision than ever, once again.

The new paper recalculates the Standard Model predicted Higgs boson production rate and determines that some next to leading order terms contributing to the predicted Higgs boson production rate were more important than had been expected. It turns out that these omitted terms can led to up to 10% more Higgs bosons being produced than would have been predicted without them in some circumstances.

Including the omitted terms explains most or all of the excess of experimentally observed Higgs boson production over the old calculation of the SM predicted value. This also, by the way, tends to imply that the uncertainties in the old experimental measurements were probably overestimated, which is a common reality in electroweak physics (as opposed to QCD or astronomy where uncertainties are often underestimated).

This new discovery feels like a reprise of the comparisons between the experimentally measured values of muon g-2 and state of the art calculations of the Standard Model prediction. In both cases, the gap has been mostly bridged by improving the quality of the calculations of the Standard Model predictions with an immense amount of hard calculation work, rather than by improving experimental accuracy or discovery new beyond the Standard Model physics. And, like the muon g-2 discrepancies, the part of the Higgs boson production calculation that has impaired the accuracy of the Standard Model prediction has mostly been the very hard to calculate strong force/hadronic/quark based part of what is primarily an extremely precise electroweak calculation.

The new paper and its abstract are as follows:

We present the mixed QCD-electroweak corrections to Higgs boson pair production in the quark-antiquark channel. 

The virtual amplitudes are computed fully analytically using the method of differential equations. We determine the integration constants by matching our expressions to the large mass expansion limit of the canonical integrals. We implement the results in the POWHEG-BOX framework for phenomenological studies. 

The corrections are found to have a significant impact on the shapes of differential cross sections, reaching up to +10% for the invariant mass distribution of the Higgs boson pair near the production threshold. This channel has not been considered before in calculations of the next-to-leading order electroweak corrections to Higgs boson pair production.

Marco Bonetti, Gudrun Heinrich, Philipp Rendler, William J. Torres Bobadilla, "Electroweak corrections to Higgs boson pair production: The quark channel" arXiv:2606.25928 (June 24, 2026) (contribution to the proceedings of Loops and Legs in Quantum Field Theories 2026, Bayreuth, Germany).

The new paper above is a physics conference summary of a more detailed paper on the same topic released in January of this year.

More Higgs Boson Properties Measured

The experimental data is still strongly consistent with the observed Higgs boson being the Standard Model Higgs boson.

A study of the structure of the coupling between the Higgs boson and the top quark is performed using events from tt¯H and tH production in the H→γγ decay channel, with 164 fb−1 of proton-proton collision data at a center-of-mass energy of s√ = 13.6 TeV collected by the ATLAS detector at the LHC. 

The cross section of the tt¯H process times the Higgs to diphoton decay branching ratio is measured to be 1.46+0.40−0.35=1.46+0.34−0.32(stat.)+0.22−0.13(sys.) fb, corresponding to 1.13+0.33−0.28 times the Standard Model prediction. 

An observed 95% confidence level limit on the tH production cross section times the Higgs to diphoton decay branching ratio is set at 6.2 times the Standard Model prediction, compared to an expected limit of 4.4 times, constituting the most stringent tH upper limit achieved in a single measurement to date. 

The results are combined with 140 fb−1 of proton-proton collision data collected at s√ = 13 TeV in the same production and decay channel, and a CP-mixing angle of |α|>38∘ is excluded at the 95% confidence level, with a purely CP-odd Higgs-top Yukawa coupling excluded at the level of 5.8 standard deviations, providing the most stringent direct constraints on the CP structure of the Higgs-top Yukawa interaction to date.

ATLAS Collaboration, "Probing the Higgs-top Yukawa interaction in the tt¯H and tH processes using H→γγ with the ATLAS detector" arXiv:2606.04855 (June 3, 2026) (Phys. Rev. Lett.) (the paper is 36 pages long including a 20 pages long list of authors).

More Physics Quick Hits

A relationship between the Higgs boson, top quark, and Z boson masses

Maybe a coincidence, maybe meaningful. The only relation that fits, using pole masses, holds at 1.4 sigma, but tends to predict either a rather high Higgs boson mass, or a rather low top quark mass.

I have little doubt that there are deeper functional relationships between the fundamental constants of the Standard Model (or at least some of them) than are contained within the Standard Model (what I call "within the Standard Model new physics" as opposed to "beyond the Standard Model new physics"). And, even if this particular relationship is not actually true, it is close enough that it is fruitful to ask, if there is some deeper source for these experimentally measured physical constant values, what kind of relationship would produce a close coincidence like this one.

For example, I wonder if an approximation of this relationship is favored in some way by the LP & C relationship that the square of the Higgs vev is equal to the sum of the squares of the fundamental SM particle masses, or by the approximate, but not exact, equality between the sum of the squares of the fundamental fermion masses and the sum of the squares of the fundamental boson masses.

Indeed, the paper notes that: 

After the Higgs discovery the numerical observation M(H)^2 ≃ M(Z)*M(t) (1) was proposed as a possible electroweak mass coincidence involving the heaviest spin-0, spin-1/2 and spin-1 representatives of the Standard Model (SM) spectrum.

(The citation for this sentence is to a paper by the author of the current paper: E. Torrente-Lujan, "The Higgs mass coincidence problem: why is the Higgs mass M2 H = MZMt?", Eur. Phys. J. C 74 (2014) 2744, arXiv:1209.0474.)

This suggests that there might be a fuller relationship that involves addition masses on the Standard Model spectrum beyond the heaviest ones that might provide correcting terms bringing the relationship to a more exact one.

I also seem to recall that there theoretically expected mass of the W boson in the Standard Model is a function of the Z boson mass, the top quark mass, and the Higgs boson mass, based upon electroweak unification in some way, but have never seen that relationship spelled out in detail. I have only seen the abbreviated leading order relationship between the W boson mass and Z boson mass that is related to the electromagnetic force and weak force coupling constants. 

The paper doesn't evaluate the "arithmetic relation" with the theoretically predicted W boson mass of 80.357 ± 0.006 GeV, but because that value is lower than the PDG value of 80.3692 ± 0.0133 GeV, it should be a somewhat better fit with the theoretically predicted W boson mass. As it turns out, this difference doesn't matter much, and neither does the difference between the Higgs boson mass that they use of 125.2 ± 0.11 GeV and the lower value of the Higgs boson mass of 125.09 GeV that is sometimes used. Indeed, the greater precision of the theoretically estimated W boson mass may increase the statistical significance of the discrepancy somewhat.

The relation M(H)^2 ≃ M(Z)*M(t), previously proposed as a non-trivial Higgs mass coincidence, is reconsidered with present electroweak inputs and with a scheme-consistent matching analysis. With the 2025 PDG values for M(Z), M(W) and M(H), and the ATLAS-CMS direct top-mass combination, the pole-level ratio is ρ(Zt)=M(Z)*M(t)/M(H)^2 = 1.00362 ± 0.00261. Thus an exact pole-level geometric relation predicts either M(H) = 125.426 ± 0.120 GeV or M(t) = 171.898 ± 0.302 GeV, which is still a 1.4σ test rather than an exclusion. 

By contrast, the companion arithmetic relation gives ρ(Wt) = (M(W)+M(t))/(2M(H))=1.00994±0.00159 and is not a viable exact mass sum rule. 

We then evaluate the complete NNLO weak-scale MS bar matching formulae at μ=M(t). In the standard convention one obtains ρˆ(Zt(M(t)) = √(g(2)^2+g(Y)^2) * y(t)/(4√2λ) = 0.96714±0.00361. Consequently, the exact running-coupling boundary condition λ =  g(Z)y(t)/(4√2) at the top scale would predict M(H) = 123.19 ± 0.20 GeV, or equivalently M(t) = 177.81 ± 0.50GeV when M(H) is held fixed. This is incompatible with the measured point. 

A possible symmetry explanation must therefore act on pole-level threshold quantities, or provide a finite matching factor κ(th) = 1.0340 ± 0.0039 at the electroweak scale. We formulate this requirement as a target for custodial/top-Higgs or triality-like symmetry extensions.

E. Torrente-Lujan, "The Higgs-top-Z mass coincidence relation after NNLO matching" arXiv:2605.21721 (May 20, 2026) (Report number: FISPAC-TH/3145-26, UQBAR-TH/26-97234).

Another key chart from the paper is this one:

The Lambda predictions are very far from the mark, as are the "arithmetic relation" estimates. The other relationship still has some tension with the experimental results but isn't ruled out.

Bounds on new neutrino physics

The constraints on BSM physics continue to narrow. In the Standard Model, the neutrino magnetic moment is predicted to be far below the threshold of current experimental detection, and the neutrino has an exactly zero electromagnetic charge. These results are consistent with those predictions and thus constrain BSM neutrino physics to very slight deviations from the SM predictions. Non-standard interactions of neutrinos are likewise constrained materially.

CODATA 2022 gives the value:

     ${\displaystyle {\sin }^2{\theta }_{\mathsf{\text{w}}}=1-{\left(\frac{m_{\mathsf{\text{W}}}}{m_{\mathsf{\text{Z}}}}\right)}^2=0.22305(23).}$

So, the Weinberg angle measurement from the CONUS collaboration, while consistent with the world average measurement at the two sigma level, is too imprecise by two orders of magnitude to add meaningfully to our knowledge of that physical constant compared to the value obtained from simply plugging in the world average measured values of the W boson mass and the Z boson mass (or from calculating it in electroweak unification theory from the electromagnetic coupling constant and the weak force coupling constant so e^2/g^2 = sin^2 theta(W).

Its detections with pion-decay-at-rest, solar and recently with reactor antineutrinos by the CONUS collaboration render coherent elastic neutrino-nucleus scattering (CEνNS) an established tool for investigations within and beyond the Standard Model (SM). The CONUS experiment located at the nuclear power plants in Brokdorf (Germany) and Leibstadt (Switzerland) operates Germanium semiconductor detectors in a compact shield at close distance to the reactor core. An observation with 3.7σ significance is reported at the Leibstadt site, showing good agreement with its SM prediction.

Physics investigations performed with the last datasets collected at the Brokdorf reactor and with the first data obtained at the Leibstadt site are summarized. By using the experimental analysis framework, the presented results contain the full systematics that underlie the experiment. 

Previously determined limits with neutrino-electron scattering on the neutrino magnetic moment and a neutrino millicharge are improved to μ(ν) < 5.18⋅10^−11μB and q(ν) < 1.76⋅10^−12e0 (90% C.L). Further, the scale of new physics related to NSIs is improved to ΛNSI = 145 GeV and limits on the coupling of light new mediators are lowered down to 4⋅10−7 (90% C.L.) with the new data. Finally, the determination of the Weinberg angle with CEνNS and reactor antineutrinos yields sin(θ(W))^2  = 0.28 +0.03 −0.04 at a momentum transfer of ∼10 MeV.

N. Ackermann, et al., "New constraints on physics within and beyond the standard model from the latest CONUS datasets" arXiv:2605.22815 (May 21m 2026).

The abstract is unclear about what there is 3.7 sigma evidence of, but the body text clarifies that: "With data collected there since 2023, a successful CEνNS detection was reported with 3.7σ significance."

The body text explains some of the theoretical motivation for the paper:

On theory side CEνNS has become an interesting tool for investigations within and beyond the standard model (BSM) because of its flavor-blind and, in principle, threshold-free properties [21–27]. Within the SM it enables measurements of the Weinberg angle sin^2 θ(W) at the MeV scale with neutrinos and probe modifications of the involved couplings, i.e. via radiative correction [28–31] or investigation of the nuclear form factor when deviating from full coherence, i.e. with higher neutrino energies from πDAR sources [32–36]. BSM searches can be performed by testing for new neutrino interactions, for example in the context of heavy new physics via non-standard neutrino interactions (NSIs)[37–43] or new light mediators [44–53]. Neutrino (electromagnetic) properties [26, 27, 54–56] or emerging new particles may be probed as well [57–59]. Furthermore, future applications in the context of multi-messenger astronomy [60–62] or nuclear safeguarding seem promising [63, 64]. Experimental upscaling in the near future will allow such investigations via precision CEνNS measurements.

The (Weak) Evidence For Extra Higgs Bosons

The 95 GeV bump is suspiciously close to the mass of the Z boson plus the mass of the b-quark. The 152 GeV bump is close to the mass of two W bosons reduced by the mass of two b-quarks. 

The implication of these coincidences is that there could be an explanation along the lines of diphoton signals that are missing decay products that prevent them from accurately reflecting the true source of the diphoton signals. 

Also, given the modest statistical significant of these alleged resonances, it could be that these are simply the product of statistical flukes in the background estimations or some other sort of measurement errors.

After the Higgs discovery, the question of whether particles beyond those of the Standard Model exist is more pressing than ever. In this context, the scalar sector is particularly promising, since it lies at the core of the internal problems of the Standard Model, while extensions of it allow us to resolve them and can provide explanations for Dark matter, non-zero neutrino masses, inflation etc. 

In these proceedings, we review the indications for new Higgs bosons at the electroweak scale with masses of ≈95 GeV and ≈152 GeV. These excesses are most significant in the di-photon channel but are supported by weaker-than-expected limits in other decay modes. 

While for the 95 GeV candidate the production mechanism is mostly unknown, the (hypothetical) 152 GeV Higgs is dominantly produced in association with leptons, (b) jets and missing energy, pointing towards the Drell-Yan production of an SU(2)L triplet with Y=0. Interestingly, this model predicts t→H±b with H±→WZ, which resembles the signature of tt¯Z production in the Standard Model and is in fact preferred by current data. 

Finally, we investigate the possibility that the significant tensions between the Standard Model predictions and the measurements in differential top-quark distributions are due to contamination from new physics involving both the 152 GeV and the 95 GeV scalar.

Andreas Crivellin, et al., "Indications for New Higgs Bosons" arXiv:2605.04233 (May 5, 2026) (Proceedings of the Corfu Summer Institute 2025 "School and Workshops on Elementary Particle Physics and Gravity" (CORFU2025)).

The Latest News In Top Quark Physics

The latest indirect measurement of the top quark pole mass is surprisingly precise (exceeding the precision of the world average in a single measurement) despite the method used, which has historically had large error bars. The Particle Data Group world averages are as follows:

This will probably drag up the world average a little bit, to about 172.7 GeV.

We present an indirect determination of the top-quark pole mass mt within a global analysis of parton distribution functions (PDFs), based on the public NNPDF framework. 

We consider a wide range of measurements, including both single- and double-differential observables, computed at NNLO QCD accuracy with EW corrections, and analyse their individual as well as combined impact on the joint (α(s),m(t)) parameter space, while accounting for PDF evolution up to approximate N3LO QCD accuracy with QED corrections. We account for missing higher order QCD uncertainties by default. 

Unique to our analysis are the inclusion of, first, toponium contributions around the tt¯ threshold, second, state-of-the-art constraints on αs from the lattice, and finally, a detailed sensitivity study of the various ATLAS and CMS differential cross-section measurements at 8 and 13 TeV. We demonstrate explicitly how a combined determination requires the refitting of the PDFs in order to correctly correlate uncertainties. 

We find mt = 172.80 ± 0.26 GeV at approximate N3LO QCD including NLO QED, EW and toponium corrections.

Richard D. Ball, Jaco ter Hoeve, Roy Stegeman, "A Determination of the Top Mass from a Global PDF Analysis" arXiv:2603.28865 (March 30, 2026).

Another new paper on top quark physics (with an abstract devoid of much of an interesting description of the paper) confirms that: 

(1) the experimentally measured top quark-antitop quark pair production rates are consistent with the Standard Model expectation, 

(2) toponium has been discovered by both the ATLAS and CMS experiments at the Large Hadron Collider (LHC), and 

(3) the Higgs field Yukawa of the top quark is experimentally confirmed to be not more than 2.1 times the Standard Model expectation (the coupling should be proportionate to the top quark's pole mass in the Standard Model).

The Higgs Boson Still Matches The Standard Model

The Standard Model Higgs Boson hypothesis continues to be a good fit to the data, this time, an inclusive measurement of all Higgs bosons produced in the LHC data of the CMS experiment over a three year period.

Combined measurements of Higgs boson production and decay rates are reported, representing the most comprehensive study performed by the CMS Collaboration to date. The included analyses use proton-proton collision data recorded by the CMS experiment at s√ = 13 TeV from 2016 to 2018, corresponding to an integrated luminosity of 138 fb−1. The statistical combination is based on analyses that measure the following decay channels: H → γγ, H → ZZ, H → WW, H → ττ, H → bb, H → μμ, and H → Zγ → ℓℓγ (ℓ = e,μ). Information in the events from each decay channel is used to target multiple Higgs boson production processes. Searches for invisible Higgs boson decays are also considered, as well as an analysis that measures off-shell Higgs boson production in the H → ZZ → 4ℓ decay channel. 

The best fit inclusive signal yield is measured to be 1.014 +0.055 −0.053 times the standard model expectation, for a Higgs boson mass of 125.38 GeV. 

Measurements in kinematic regions defined by the simplified template cross section framework are also provided, as well as interpretations in the coupling modifier and standard model effective field theory frameworks. The coupling modifier interpretation is further used to place constraints on various two-Higgs-doublet models. The results show good compatibility with the standard model predictions for the majority of the measured parameters.

CMS Collaboration, "Combined measurements and interpretations of Higgs boson production and decay in proton-proton collisions at s√ = 13 TeV" arXiv:2602.18611 (February 20, 2026) (Submitted to Reports on Progress in Physics).

The result is about 0.2 sigma above the Standard Model expectation, which is very consistent with the result obtained and once again suggests that the uncertainties in the measurement (the average discrepancy from the expected results if the errors are accurately measured and Gaussian should be 1 sigma), in the interests of being conservative in estimating them, are overestimated. This is common in electroweak (as opposed to strong force) high energy physics experiments.

The breakdown of the sources of uncertainty are notable too:

The theoretical uncertainty is the biggest contributor to the total uncertainty. More specifically:

The largest component of the uncertainty originates from the theoretical uncertainty in the signal yield normalization (∆µincl/µincl = 3.6%). The contributions from the experimental uncertainties are shared amongst the different sources of uncertainty, with no single dominant contribution.

The statistical uncertainty (assuming that the uncertainty can correctly be modeled as Gaussian, i.e. a statistical normal distribution) is almost certainly spot on correct because establishing it is a mechanical process that involves few judgment calls. This means that any excess estimates of uncertainty in this experiment come from the theoretical and systemic experimental uncertainties.

A statement about the Higgs boson mass used in this analysis is found in the introduction, and doesn't represent any insights from the inclusive measurement which doesn't meaningfully distinguish between the Higgs boson mass assumed in the analysis and newer more precise measurements by the ATLAS and CMS experiments which are about 0.2% (i.e. 170-200 MeV) less massive.

The SM predictions for the Higgs boson production and decay rates depend on the mass of the Higgs boson mH. For all measurements in this paper, the mass is fixed at mH = 125.38 GeV. This was the most precise measurement of m(H) (± 0.14 GeV) by the CMS Collaboration at the time that the analyses entering the combination were performed. Since then, a more precise measurement of m(H) = 125.08 ± 0.12 GeV has been performed by CMS in the H → ZZ → 4ℓ channel. The ATLAS Collaboration also performed a more precise measurement of m(H) = 125.11 ± 0.11 GeV, combining the H → ZZ → 4ℓ and H → γγ channels. The small difference in m(H) between these values has a negligible effect on the results in this paper.

So, any hope from the abstract that this experiment would also shed light on the Higgs boson mass has been dashed. 

The final point in the abstract about only a majority of the results being compatible with the Standard Model is explained as follows:

In contrast to the inclusive measurement, the per production process measurement shows a small tension with the SM, with a compatibility p-value of pSM = 0.02. This tension is mostly driven by µtH, for which an excess of 2.2 standard deviations above the SM expectation is seen. The µWH and µZH parameters are also measured to be larger than the SM expectations by approximately two standard deviations. The 68% CL intervals range from ±7.5% for µggH to ±39% for µtH, relative to their best fit values. 

The per decay channel measurement shows a better compatibility with the SM (pSM = 0.33). The largest deviations are observed in the µττ and µZγ parameters. However, these are still compatible with the SM expectations within the 95% CL intervals. The µγγ, µZZ, µWW, and µττ parameters are all measured with excellent precision, with 68% CL intervals of approximately ±10% relative to their best fit values. The µbb parameter is measured with a 68% CL interval of ±15%. This represents a significant improvement compared to the previous combined Higgs boson measurement by the CMS Collaboration (±21%), because of the newly added H → bb channels and updated H → bb input analyses. The parameters for the rarer decay channels, µµµ and µZγ, are measured with 68% CL intervals of ±37% and ±39%, respectively, relative to their best fit values.

The biggest deviations in particular channels are still only slight tensions and are expected due to the look elsewhere effect. 

The constraints on the Higgs boson self-coupling relative to the Standard Model expected value, kappa(A), which is a quite hard to measure property of the Higgs boson, are also very consistent with the Standard Model expectation, as shown in the chart below (with kappa(F) and kappa(V) reflecting scenarios where there are different couplings to fermions and vector bosons).

A Parts Per Thousand Measurement Of The Electroweak Mixing Angle

The weak mixing angle or Weinberg angleis a parameter in the Weinberg–Salam theory (by Steven Weinberg and Abdus Salam) of the electroweak interaction, part of the Standard Model of particle physics, and is usually denoted as θ(W). It is the angle by which spontaneous symmetry breaking rotates the original W(0) and B(0) vector boson plane, producing as a result the Z(0) boson, and the photon. Its measured value is slightly below 30°, but also varies, very slightly increasing, depending on how high the relative momentum of the particles involved in the interaction is that the angle is used for.

- Wikipedia.

In the Standard Model of Particle Physics, the electroweak mixing angle is a function of the ratio of the W boson mass to the Z boson mass, and is also a function a simple formulas that have the electromagnetic coupling constant and the weak force coupling constant as inputs.

The electroweak mixing angle is of mostly theoretical interest as a key derived parameter in the electroweak force unification (i.e. it can be calculated from other Standard Model fundamental constants) that was a key breakthrough in the development of the Standard Model of Particle Physics. 

A part per thousand measurement honestly isn't all that precise for electroweak physics (some physical constants in electroweak physics are known to parts per million levels or better), but since it doesn't have many direct engineering applications, its measurement is mostly a consistency check on the electroweak portion of the Standard Model as a whole, that provides a fairly tight global constraint on the magnitude of beyond the Standard Model physics of many varieties that can be consistent with the experimental data (in much the same way as muon g-2 measurements do). 

But, unlike muon g-2, at least at the precisions at which we can measure it, the electroweak mixing angle only receives electromagnetic force and weak force contributions, and does not receive QCD strong force contributions.

The measurement of this physical constant described in the paper below is made at the momentum scale of the Z boson pole mass, about 91.19 GeV/c^2, which in an energy range known as the electroweak scale.

This energy scale is considerably greater than the mass-energies of first and second generation quarks, the electrons, muons, tau leptons, protons, neutrons, and the light mesons that bind protons and neutrons in atomic nuclei. But, it is considerably less the the maximum momentum scales that can be reached at the Large Hadron Collider (LHC), which is the highest energy particle collider. 

The energy scale at which this measurement is made is about three orders of magnitude higher in energy scale than the energy scale at which the anomalous magnetic moment of the muon (i.e. muon g-2) is measured, which is about 0.10566 GeV/c^2.

This contribution presents a overview of a recent CMS-based determination of the effective leptonic weak mixing angle, sin2θℓeff, derived from forward-backward asymmetry measurements in Drell-Yan events at 13 TeV. Although the CMS analysis achieved a major reduction in uncertainties, its overall precision is ultimately limited by residual parton distribution function (PDF) uncertainties. 

This proceeding highlights the role of complementary CMS observables, which probe distinct parton-density combinations and provide additional constraints beyond those obtained from the original asymmetry measurement alone. 

The improved analysis yields a substantially reduced total uncertainty, resulting in sin2θℓeff = 0.23156 ± 0.00024. This result is consistent with the Standard Model prediction and represents the highest precision achieved so far in an individual determination of this parameter.

Arie Bodek, Hyon-San Seo, Un-Ki Yang, "Summary of the Precision Measurements of the Electroweak Mixing Angle in the Region of the Z pole" arXiv:2601.20717 (January 28, 2026).

The value measured by the CMS experiment at the LHC is about 0.00005 lower than the Standard Model prediction (which is about 0.2 sigma and indicates that the uncertainty in the measurement is probably overstated with conservative assumptions about its accuracy).

This result, more clearly than past experimental results, favors the Standard Model of Particle Physics over the beyond the Standard Model "two Higgs doublet" model, which which there are four extra Higgs bosons, two charged Higgs bosons (positive and negative), one odd parity Higgs boson, and one heavy even parity Higgs boson. 

Earlier LHC measurements (in blue), Tevatron measurements (in green), and pre-Tevatron measurements from LEP and SLD (in black), were collectively inconclusively in their relative preferences for the Standard Model compared to a two Higgs doublet model. The CDF M(W) value below is an outlier that has never been taken very seriously, and probably the product of some sort of subtle analysis error.