Wednesday, February 28, 2018

A Short History of Demographic Change In Britain

Britain has seen five or more rounds of near total population replacement, in addition to other more modest tweaks to its gene pool (and new cultural eras that had surprisingly little demographic impact).

The most notable less than complete population replacements have been the Anglo-Saxon migration, the Viking migrations, and modern immigration, each of which has been more heavily concentrated in some geographic regions than others. The Normans had little genetic impact outside the British aristocracy.

There is overwhelming evidence of a great Celtic cultural impact, but the demic impact of the Celts was not obviously great. But, there are methodological problems with determining what their demographic impact was on Britain because the Celts would have been genetically and physically quite similar to native Britons. Romans and Punic people meanwhile, definitely had little demographic impact.

1. Pre-Neanderthals Hominin occupation of Britain was intermittent in pre-history.

The first members of the genus Homo in Britain were pre-Neanderthal archaic hominins who had arrived by 814,000 years ago, and were forced out by an ice age about 200,000 years ago, leaving Britain without any members of the genus Homo for the next 100,000 years.
Early pre-Neanderthals inhabited Britain before the last ice age, but were forced south by a previous glaciation about 200,000 year ago. When the climate warmed up again between 130,000 and 110,000 years ago, they couldn't get back because, similar to today, the Channel sea-level was raised, blocking their path.
Homo heidelbergensis arrived in Britain around 500,000 years ago and used Acheulean flint tools, but then left during a severe ice age from 478,000 years ago to 424,000 years ago.  Pre-Neanderthal hominins were then present intermittently for the next 200,000 years or so.

2. Neanderthals Starting around 100,000 years ago, Neanderthals arrived in Britain. Early Neanderthals or "pre-Neanderthals" were also present from 230,000 years ago to around 200,000 years ago.

The Neanderthals were probably weakened by climate factors partially related to a string of extreme volcanic eruptions in Europe and possibly also by improving anatomically modern human capabilities both cultural and individual. Still, Neanderthals in Europe kept anatomically modern humans at bay for about 32,000 years than modern humans expanded to West Asia and South Asia, and at least 82,000 years after modern humans first left Africa.

Neanderthals persisted in Jersey (and probably also Doggerland) until about 42,000 years ago.

3. Cro-Magnon Neanderthals were completely replaced in Britain by the first wave on anatomically modern humans in Europe, the Cro-Magnon, who first appeared in Britain around 43,000 years ago. There was probably some admixture at that time, but most Neanderthal admixture in the Cro-Magnon probably pre-dated their arrival in Britain rather than occurring in situ. Neanderthals and Cro-Magnon typically overlapped in any one place for about 1,000 years at most before Neanderthals were replaced.

Britain was not a refugium during the last big ice age, however. Its entire Cro-Magnon population was eliminated in the run up to the Last Glacial Maximum as glaciers covered Britain. The Last Glacial Maximum was 20,000 years ago.

Very few relic populations in refugia during that ice age that including the Last Glacial Maximum had British Cro-Magnon migrants among them. These refugia had an effective male population as small as 30 men. Thus, any admixture between Neanderthals and Cro-Magnon that took place in Britain was eliminated in the last great ice age.

4. Mesolithic Western Hunter-Gatherers Then, Britain was repopulated in the Mesolithic era by Western Hunter-Gathers like Cheddar Man (from about 9500 years ago) over a period somewhere in the range of about 14,500 to 6,000 years ago. 

Despite coming from a much more restricted gene pool, Western Hunter-Gathers were actually pretty similar in terms of Y-DNA and mtDNA and even to a lesser extent, autosomal genetics, to Cro-Magnon, whose relic populations in refugia like the Franco-Cantrabrian refuge and Italy repopulated Europe with a much restricted founding population after the Last Glacial Maximum, even though direct continuity was absent in Britain.

Also notably, around 6200 BCE, a megatsunami suddenly flooded an inhabited land bridge between Britain and continental Europe called Doggerland (which had been shrinking with rising sea levels since 9000 BCE) was suddenly flooded by runoff from melting glaciers. The Dogger Bank, however, an upland area of Doggerland, remained an island until at least 5000 BCE.

5. Neolithic Farmers Around 6000 years ago (about 4000 BCE), in the Neolithic Revolution in Britain, early European Farmers, probably more Mediterranean Cardial Pottery folk than LBK farmers with more direct links to Anatolia largely (90%+) replaced Western Hunter-Gatherers. Farming supports more than an order of magnitude greater population density than a hunter-gatherer lifestyle does, and as an isolated island with relatively little megafauna after the Last Glacial Maximum, Britain was probably not the most abundant place for Western Hunter-Gatherers to try to survive in, so the hunter-gatherer to farmer population surge may have been particularly great.

One key subtly genetically is that early European Farmers were themselves a mix of European hunter-gatherers and core Fertile Crescent original farmers, and the hunter-gatherers that the original farmers admixed with were only modestly genetically drifted from Western hunter-gatherers. So, crude ancestry estimates overestimate the extent to which British or Western European hunter-gatherers admixed with local hunter-gatherer populations.

This said, on the European continent, there was significant enrichment of local hunter-gather admixture following first wave Neolithic collapse before Bell Beaker and Corded Ware people emerged onto the European scene.

But, the first wave Neolithic farming civilization collapsed, in my view, most likely as a result of crop failures from some combination of soil exhaustion due to poor farming practices of first wave Neolithic farmers (repeated everywhere first wave Neolithic farmers went) and climate, returning Britain to a predominantly hunter-gatherer-herder society with a much lower population density. There is some evidence a wave of plague that swept Europe at this time as well, but disease is often an effect rather than a cause of famine.

6. Bell Beaker People The semi-hunter-gatherer/herder ancestors of the first wave Neolithic Britons were then almost entirely replaced or overwhelmed demographically (93%+), in perhaps a few centuries or less (in a period starting around 2400 BCE and ending before 2000 BCE see also here suggesting 2500 BCE to 2100 BCE), by the Bell Beaker people who brought a more sophisticated Copper/Bronze age farming package with them that endured.

The Bell Beaker people who colonized Britain were genetically very similar to the Bell Beaker people of Continental Europe, with significant steppe ancestry and regionally specific Y-DNA R1b clades and mtDNA H clades, rather than like the Iberian Bell Beaker people who were genetically more similar to the Neolithic people of that region with only a sprinkling of the genetic flavors that are predominant in other European continental Bell Beaker people. This was a quite surprising discovery, because in terms of ceramics and other physical relics, the Bell Beaker culture appears to have originating in Iberia and in particular in Portugal which is the least like European continental Bell Beaker people genetically.

Also, despite the heavy rate of population change associated with the appearance of the Bell Beaker people, both in Britain and in Europe, the change must not have been complete, because there was, for example, a continuity of architectural styles and religious practices to some extent, between the descendants of the first wave Neolithic people and the Bell Beaker people. 

The Bell Beaker colonization of Britain was its last nearly complete population replacement through the present. Today's British people are on average perhaps 80% identical to the Bell Beaker people genetically (in terms of ancestry percentages, which ignore the large portion of the genome in which all humans and all Europeans since the Middle Neolithic to early Bronze Age, are basically fixed, in raw, model independent genetic overlap the percentage similarity is much, much higher) with Germanic admixture making up the balance. These two successive waves of replacement left only about 1% of less of the British gene pool attributable to the Mesolithic Western Hunter-Gatherers of Britain. Previous estimates from the early 2000s that concluded that most British ancestry was traceable to the Mesolithic era or the Neolithic revolution in Britain have been revealed by ancient DNA evidence to be incorrect.

There was significant population exchange and trade between Bell Beaker Britain and Bell Beaker areas in continental Western Europe for pretty much the entire Bell Beaker area until Bronze Age collapse.

In terms of physical traces of culture and probably language as well based upon the time depth of the Celtic languages, the Bell Beaker derived cultures collapse and are replaced by recognizably Celtic cultures within a few centuries of Bronze Age collapse (ca. 1200 BCE), which was a climate driven collapse of many cultures over a geographic range from Britain to Egypt to the Indus River Valley (at least).

The language(s) spoken by the Bell Beaker people of Britain remains an open issue that may never be definitively resolved. The oldest historically attested linguistic layer in Britain is Celtic with discernible impacts from other populations that were historically present in Britain discussed below.

7. Celts, Romans and Punic People Subsequent Celts (coinciding with the British Iron Age ca. 800 BCE), Romans (43 CE to 410 CE plus an invasion in 55-54 BCE), and heavy maritime trade handled by Punic people from Northwest Africa (Iron Age ca. 1100 BCE to early Middle Ages ca. 800 CE), each of whom had a powerful toponym impact and a significant cultural impact on Britain, didn't have much of a population genetic impact. The demographic impact of the Celts was fairly minor and the Romans and Punic traders had only a negligible demographic impact on Britain. 

Only about 4% of the population of Roman Britain was Roman, and some of those would have been foreign soldiers on a short term tour of duty rather than permanent settlers.
Roman Britain had an estimated population between 2.8 million and 3 million people at the end of the second century. At the end of the fourth century, it had an estimated population of 3.6 million people, of whom 125,000 consisted of the Roman army and their families and dependents. 
The urban population of Roman Britain was about 240,000 people at the end of the fourth century. The capital city of Londinium is estimated to have had a population of about 60,000 people. Londinium was an ethnically diverse city with inhabitants from across the Roman Empire, including natives of Britannia, continental Europe, the Middle East, and North Africa. There was also cultural diversity in other Roman-British towns, which were sustained by considerable migration, both within Britannia and from other Roman territories, including North Africa, Roman Syria, the Eastern Mediterranean, and continental Europe.
The limited Roman demic impact coincides with the shallowness of its cultural impact. For example, while Christianity arrived in Britain first from the Romans, as did Roman law, both nearly completely died out, with Christianity re-emerging from Irish and continental European missionaries, and Roman legal concepts returning only with the Norman elites.

The permanent Punic population appears to have been confined to expatriot neighborhoods in some select port cities.

The certainty with which we can say that the demographic impact of the Celts was small, however, is fairly weak. As noted above, the significant population exchange between Britain and Western Europe in the Bell Beaker era means that the population genetic makeup of the Celts may have been very similar to that of the British, to the point where limited ancient DNA samples, and population genetic studies of modern samples three thousand years removed, may not be able to discern the differences between the populations as distinct ancestral groups. If invading Celts were genetically very similar to Bell Beaker era Britons who were invaded, even a major population shift might have been almost invisible.

In the past, I have estimated Celtic demographic impact by assuming that the Celtic elite was initially mostly Y-DNA R1a and was a male dominated migration, and then assumed that the percentage of men with Y-DNA R1a (of the Northern European clade) in Western Europe is roughly double the percentage change in population due to Celtic migration. This was supported by ancient Urnfield Y-DNA R1a. This ranges from 0% to 8% in the British Isles, suggesting an average on the order of 4% which in turn suggests a 2% population turnover wit the Celts.

But, the trouble with this hypothesis is that the R1a distribution in the British Isles appears to be a better fit geographically for Angles, Saxon and Viking demographic impacts than it does for Celtic demographic impact. Ireland, Scotland and Wales, which should be higher than average if Celts are the source of Y-DNA R1a against a Bell Beaker R1b sourcing, are actually lower in Y-DNA R1a than England (Ireland is about 1% and Wales is 1%-2%) except on islands where maritime invaders would have had an edge, suggesting that Y-DNA R1a in Britain is more likely mostly Germanic than Celtic in its sourcing. Likewise, the Y-DNA R1a frequency in France which was historically Celtic before Romance languages replaced Celtic languages (excluding French Basque for which the percentage is 0%) is only about 2%, again disfavoring a hypothesis that even Celt elites had Y-DNA R1a.

Ancient dental remains also support a primarily cultural diffusion model of Celtic culture, rather than a mass migration, although if the populations are genetically and physically similar, that degeneracy may also be hard to resolve,

This doesn't detract from, however, and indeed reinforces, the possibility that degeneracy in population genetic makeup between the Bell Beaker people and the Celts could cause us to underestimate to the extent to which the Celtic cultural transition in Britain involved a mass migration of people from Europe to Britain.

It is also notable that: Celtic parts of the U.K. (presumably Scotland, Wales, Northern Ireland), have more steppe ancestry than Southern and Eastern England proper, presumably because Norman invaders ca. 1066 CE had less steppe ancestry than the pre-existing residents of the U.K. The modern residents of England proper also have less steppe ancestry than Anglo-Saxon ancient DNA. Keep in mind, however, that this is a subtle difference that is discernible only because of a huge sample size (N=113,851) in a generally very homogeneous population.

The hypothesis that the Norman invaders had less steppe ancestry is consistent with the evidence that the Bell Beaker people, who had significant steppe ancestry, almost fully replaced the population in Britain but less fully replaced populations in Continental Europe, the balance of whom would have been predominantly early European farmers with little or no steppe ancestry who were most similar to modern Sardinians and Basque people.

8. Anglo-Saxons, Vikings, Normans and Jews. There were subsequent waves of Angles and Saxons (early Middle Ages after the fall of Rome ca. 400 CE) who are the source of the Germanic Old English language, Vikings (late first millennium in the middle Middle Ages ca. 865 CE or 800 CE-950 CE) with a lasting genetic impact mostly limited to the Orkney Islands and a few other coastal and island localities in Northern Scotland and between Britain and Ireland, and Normans (in the late Middle Ages, conventionally 1066 CE) whose Norman French influences caused the transition from Old English to Middle English. 

Traces of these migrations are visible in modern British regional population genetics despite the fact that Britain is actually very homogeneous in terms of population genetics, due to the large sample sizes and precision genetic sampling of individuals whose genomes are sampled in the latest genetic surveys of the British people, and despite the fact that Angles, Saxons, Vikings and Normans are all genetically only subtly different from the pre-existing mostly Bell Beaker and Celtic derived populations of Britain.

Anglo-Saxon demic impact may have been as high as 38% in Eastern England, although it declines with distance from that epicenter (other regional estimates are in the 10%-40% range with considerable regional variation).

As noted here
A study into the Norwegian Viking ancestry of British people found that there is evidence of particular concentrations in several areas; especially in Lowland and Eastern Scotland - and the North Sea islands Shetland and Orkney, Western Scotland and the Western Isles including Skye in Scotland, Anglesey in Wales, the Isle of Man and the Wirral, Mid-Cheshire, West Lancashire and Cumbria in England.
The percentage of modern British ancestry attributable to the Normans is more slippery to determine, and although it is not zero, it is closer in order of magnitude to the Viking and Roman contributions to British population genetics which are small. An article in the New York Times from 2007 references some historical information regarding this issue:
Dr. Oppenheimer . . . cites figures from the archaeologist Heinrich Haerke that the Anglo-Saxon invasions that began in the fourth century A.D. added about 250,000 people to a British population of one to two million, an estimate Dr. Oppenheimer notes is larger than his but considerably less than the substantial replacement of the English population assumed by others. The Norman invasion of 1066 A.D. brought not many more than 10,000 people, according to Dr. Haerke.
This would suggest a Norman genetic impact of about 0.5% or less on the British gene pool, which would make it almost impossible to discern outside the British aristocracy, many of whom hold hereditary titles traceable to those 10,000 or so Normans.

Britain does not have anything approaching the endogamous caste features in its gene pool that India does, but there are subtle enhancements of Norman ancestry in the British upper classes and there are some very subtle but traceable genetic connections between the modern British upper classes/lower classes and their ancestors many generations earlier with corresponding traces in surnames.

The earliest evidence of Jews in England is from shortly after the Norman invasion in 1070 CE. Also notable from a population genetic perspective is the fact that in the post-Norman era in Britain (as a result of attitudes associated Norman involvement in the Crusades) is the expulsion of every Jew from England and Gascony (4,000-16,000 people), except 128 Jewish converts to Christianity in a single communal building in London (following multiple prior massacres), by the Normans in 1290 CE, which left the entire region without any Jews for the next 365 years, i.e. until 1655 CE, more than a century after the Church of England broke from the Roman Catholic Church in 1534 CE so the King could get a divorce.

9. Irish Travelers.  "Travelers" in Ireland, who also emerged in the modern era (ca. 1650 CE), while culturally similar to European Roma with South Asian ancestral roots, are genetically, pretty much indistinguishable from other native of Ireland. They make up about 0.1% of the population of the U.K.

10. Modern Era Migration. Modern era immigrants from the British empire began to arrive starting around the 16th century CE and has had a modest demographic impact on the British gene pool, at least regionally, but has never come remotely close to total replacement. 

Frequently, researchers try to screen out modern immigration when characterizing a country's gene pool, but in Britain this is more problematic than in most places, because Britain's maritime capabilities has been a global population draw (from Europe to India, Indonesia, Africa and China) for people from its empire for five or six hundred years, which is long enough to make these introgressions part of what is the indigenous Britain gene pool at this time.

Modern global migration has probably contributed more to the British gene pool, for example, than Western hunter-gatherers like Cheddar man have, and more than the Romans or the Vikings or the Punic people. The impact of modern migration in Britain is closer to the population genetic impact of Anglo-Saxon migration to Britain in magnitude and timing.

For example, about 14% of the current population of the U.K. is foreign born, and that percentage has never been less than 4% in the post-World War II period. About 13% of the population of the U.K. is non-white. About 7% of the population of the U.K. is Muslim, Hindu, Sikh or Buddhist. The largest share of the foreign born population is South Asian, followed by Chinese. About two-thirds of foreign born citizens of the U.K. have "Asian" ancestry and about a third have African ancestry (often Afro-Caribbean). These are rapidly growing sectors of the population relative to the native born population (mostly due to immigration). Several percent of people in the U.K. are native born and are not of British or Irish ancestry, roughly in accord with the historical 4% of the population was the foreign born in earlier times.

Modern migrants have settled mostly in Greater London (which has about 47% of the population that is white from the U.K. or Ireland, and about 60% white of any kind) and a few other major British cities.

UPDATE March 12, 2018:

A chart showing the population of the regions of the British Isles since the Norman Invasion:


Monday, February 26, 2018

Recent Direct Top Quark Width Measurement

According to this paper (recently updated from an earlier September version) containing the latest top quark width measurement (which is a function of its mean lifetime, a large decay width translates to a short mean lifetime with a top quark having a mean lifetime a bit more than 10^-25 seconds), the Standard Model prediction for the top quark width is:
The top quark is the heaviest particle in the Standard Model (SM) of elementary particle physics, discovered more than 20 years ago in 1995. Due to its large mass of around 173 GeV, the lifetime of the top quark is extremely short. Hence, its decay width is the largest of all SM fermions. A next-to-leading-order (NLO) calculation predicts a decay width of Γt = 1.33 GeV for a top-quark mass (mt) of 172.5 GeV. Variations of the parameters entering the NLO calculation, the W-boson mass, the strong coupling constant αS, the Fermi coupling constant GF and the Cabibbo–Kobayashi–Maskawa (CKM) matrix element Vtb, within experimental uncertainties yield an uncertainty of 6%. The recent next-to-next-to-leading-order (NNLO) calculation predicts Γt = 1.322 GeV for mt = 172.5 GeV and αS = 0.1181.
A 6% uncertainty is +/- 0.08 GeV, although the error from NLO to NNLO differences is surprisingly small, which suggests that this is a sufficient number of loops for this calculation. This implies that the top quark width at a mass of 172.5 GeV is in a one sigma range of 1.25 to 1.41 GeV if the Standard Model is correct.

This compares to the following direct measurement of the top quark width from the Run-1 LHC data from the ATLAS experiment:
This paper presents a direct measurement of the decay width of the top quark using tt¯ events in the lepton+jets final state. The data sample was collected by the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 8 TeV and corresponds to an integrated luminosity of 20.2 fb^−1. The decay width of the top quark is measured using a template fit to distributions of kinemat ic observables associated with the hadronically and semileptonically decaying top quarks. The result, 
Γt=1.76±0.33(stat.)+0.79−0.68(syst.)GeV 
for a top-quark mass of 172.5 GeV, is consistent with the prediction of the Standard Model.
The value with the combined error on the latest combined width measurement of the top quark is 1.76+0.86-0.76, which expressed as a one sigma range is 1.00 to 2.62.

Of course, experimental consistency with the predictions of the Standard Model isn't very impressive when the error bars on your experimental measurement are huge (at least on a percentage basis).

Incidentally, a somewhat higher than predicted width tends to favor a somewhat higher than currently estimated mass for the top quark. But, given that the precision of the top quark mass measurement is so much greater than the precision of the top quark width measurement, it doesn't make a lot of sense to make determinations in that direction.

By the end of the LHC experiment's run, the statistical error will decrease by quite a bit, and the systemic error will decrease by a little, and averaging this result with measurements by other means that do not have correlated systemic errors will improve a global estimate further. But, the error will still remain quite significant, so this won't necessarily provide any great insights.

Thursday, February 22, 2018

Triton Station

I've added the blog Triton Station to the sidebar. It is the blog of Stacy McGaugh, the astrophysicist who is best known for compiling the mountains of data the support either modified gravity along the lines of MOND or some other mechanism that achieves the same result to bring about the phenomena often attribute to dark matter.

It debuted on April 16, 2016. Before that McGaugh had a webpage with aesthetics on a par with pong, PacMan, and Usenet, that was packed with great links, but lacked a narrative and flash. It's still out there. But, the blog is updated fairly regularly and the posts are cogent and persuasive, in addition to being 21st century pretty.

Full disclosure: McGaugh and I got our graduate degrees at the same school (he graduated around the same time I arrived on campus), so I could be biased, although this is highly unlikely as I didn't learn this fact until today, and I've followed McGaugh's work for many years.

Fun fact: Papers that I tag on this blog as "dark matter", I first save in a browser bookmarks folder labeled "gravity".

Sunday, February 18, 2018

The Mighty Mandarin

Citrus fruits are all hybrids of one of five original kinds of fruit, with the ancestral version of the mandarin orange in the mix of most of them. Source fruits citrons and pummelos are also frequent contributors to the genetic mix.


Friday, February 16, 2018

The Biggest Mammal You Didn't Learn About In School


Takin (Budorcas taxicolor)

The Takin is a bovid (in the same clade as sheep, antelope, bison and cows) that lives in mountainous Asian bamboo forests, overlapping in habitat with giant pandas. It is the national mammal of Bhutan. In addition to Bhutan, it is found in parts of India, Burma and China. 

A detailed account of them can be found here. Like most wild megafauna, it is endangered throughout its range.

Thursday, February 15, 2018

Gordon Kane Still Suffering From Severe Cognitive Dissonance

You have to be a big name in fundamental physics, like Gordon Kane, (and must have lost all sense of perspective) to have the gall to interpret evidence that the Higgs boson discovered experimentally is exactly like the one predicted by the Standard Model, to conclude that Beyond the Standard Model physics must exist right around the corner. He is, of course, full of shit, albeit in a particularly erudite fashion in this regard. His new pre-print is as follows:
Naively, the LHC Higgs boson looks like a Standard Model Higgs boson, with no guidance to physics beyond the Standard Model, as has often been remarked. The data show that what was discovered is the true Higgs boson. If one includes the full information available, experimental and theoretical, there are actually four significant clues implied by data. They point toward a supersymmetric two-doublet decoupling theory, and a hierarchy problem solution via TeV scale supersymmetry. That in turn suggests an underlying compactified string/M theory with a de Sitter vacuum, so we can be confident that the low scale model has an ultraviolet completion.
Gordon Kane, "Exciting Implications of LHC Higgs Boson Data" (February 14, 2018).

What are his so called clues?

Clue 1
In the minimal supersymmetric world there is an upper limit on the Higgs boson mass of at most about 130 GeV, which is satisfied for the observed Higgs mass. The tree level lightest eigenstate is less than MZ and with top loop radiative corrections its mass increases up to about 130 GeV. The observed Higgs boson mass is indeed lighter than that limit.
In other words, another theory that he likes is also consistent with a Higgs boson mass of 125.09 +/- 0.24 GeV. There were about a hundred theories that made such predictions before the Higgs boson mass was known.

Also, the minimal supersymmetric model has pretty much been ruled out experimentally by the LHC. Myriad non-minimal SUSY models remain, but those models are all over the map in terms of what they predicted regarding the Higgs boson mass.

Clue 2
In a supersymmetry world with low scale superpartners the hierarchy problem is solved. That would hold here if gauginos were around the TeV scale. That is still a possible result. 
I'll leave an explanation of why the hierarchy problem isn't really a "problem" at all to Sabine Hossenfelder at her blog Backreaction (also here). The view of investigators like Kane that "naturalness" is a useful guide to physicists is the most noxious meme in the physics community for the last generation, and has done untold harm to the discipline of fundamental physics.

Also, the direct searches for the gaugino at the LHC already exclude it in excess of 1 TeV, and any new particles at that scale would have multiple detectable indirect effects that have not been observed.

Clue 3
The well-known model [1,2] with large soft Higgs mass terms and two Higgs doublets, satisfying the electroweak symmetry breaking conditions, has one light Higgs eigenstate, two heavy neutral states, and a heavy charged pair. It automatically has decay branching ratios that are very close to the Standard Model ones, just as the data does. This is called the decoupling solution, and has been familiar for over two decades. Such a solution arises naturally in some UV complete theories, as we will briefly discuss below. 
Kane is apparently not familiar with Occam's razor. When you can describe the data with both a simpler model and a much more baroque one, the simple model is preferred.

Clue 4
The fourth clue is more subtle. For a single Standard Model Higgs boson the effective Higgs potential is V = µ2h2 + λh4 . In the Standard Model λ can run to go negative at larger scales, so the potential becomes unbounded from below, and there is no resulting world. Most people reacting to this situation have shrugged and said probably the universe would be long lived so the instability can be ignored. But it was pointed out [3-7] that without vacuum stability, fluctuations in the Higgs field during inflation and in the hot early universe would have taken most of the universe into an anti-De Sitter phase, giving a massive collapse, and the expansion of the universe would never have occurred. The point was basically raised explicitly in 2008, and there was some uncertainty in how to properly calculate, over several years. Probably it was settled by the significant paper [7] in 2017. The result is that for generic expectations for the Hubble parameter during inflation, the Higgs field fluctuations generated during inflation, or the hot, high density early universe, probe the instability region, take most of the universe into the unstable AdS phase, so the usual expansion of the universe fails to occur. Thus the message is that the apparent instability is not acceptable, and new physics must arise to stabilize the vacuum. In supersymmetry λ is determined by the gauge couplings (λ = (g12 + g22)).
To restate "Clue 4" in more understandable form, you first need to understand that all physical constants in the Standard Model and kindred theories change in value in a predictable, gradual way with energy scale. In particular, the Higg potential, which gives rise to the masses of all of the fundamental particles, goes to zero or negative values at very high energies if naively extrapolated to the "GUT scale" of  about 1016 GeV. This would suggest that the vacuum in the Universe is merely "metastable" rather than "stable".

Of course, we have no experimental data beyond about 104 GeV, and no data that can be reliably discerned from astronomy observations beyond about 105 GeV. So, we really don't know if the domain of applicability of the physics that we know extends up to such high energies where factors like quantum gravity could have an impact.

Kane's speculations on what happens at such high energies are just that, speculations, in areas where there are countless competing hypotheses among published physicists in the field.

For example, a far more conservative tweak to the fundamental laws of physics, asymptotic safety in quantum gravity (which also made a much more precise and accurate prediction of the Higgs boson mass based upon the same boundary conditions issues that Kane addresses in his "Clue 4" which is consistent with a "desert" of new physics before one reaches extremely high energies, can also solve the problem that he identified.

One More Thing

Needless to say, Kane also ignores the mountains of other evidence (or more precisely, the absence of evidence where evidence is expected) that disfavor his "New Physics around the corner at the TeV scale" hypothesis.

Tuesday, February 13, 2018

Strong Force Coupling Constant And Quark Masses Measured With High Precision

Imprecision in the measurement of the strong force coupling constant is the single greatest barrier to precision predictions in QCD, so every new, independent precision determination will boost every single QCD prediction going forward.
We present a determination of the strong coupling constant αs(mZ) based on the NNPDF3.1 determination of parton distributions, which for the first time includes constraints from jet production, top-quark pair differential distributions, and the Z pT distributions using exact NNLO theory. Our result is based on a novel extension of the NNPDF methodology - the correlated replica method - which allows for a simultaneous determination of αs and the PDFs with all correlations between them fully taken into account. We study in detail all relevant sources of experimental, methodological and theoretical uncertainty. At NNLO we find αs(mZ)=0.1185±0.0005(exp)±0.0001(meth), showing that methodological uncertainties are negligible. We conservatively estimate the theoretical uncertainty due to missing higher order QCD corrections (N3LO and beyond) from half the shift between the NLO and NNLO αs values, finding Δαths=0.0011.
Richard D. Ball, et al., "Precision determination of the strong coupling constant within a global PDF analysis" (February 9, 2018).

More specifically, the NNLO result is: αsNNLO(mZ) = 0.11845 ± 0.00052 (0.4%) and the combined measurement, combining all sources of error is 0.1185 ± 0.0012, which matches the precision of the Particle Data Group global average value for this constant as of 2017 which is 0.1182 +/- 0.0012. As noted below, this error estimate is probably an overestimate.

From the Introduction to the paper:
The value of the strong coupling constant αs (mZ) is a dominant source of uncertainty in the computation of several LHC processes. This uncertainty is often combined with that on parton distributions (PDFs), with which it is strongly correlated. However, while PDF uncertainties have reduced considerably over the years, as it is clear for example by comparing the 2012 [1] and 2015 [2] PDF4LHC recommendations, the uncertainty on the αs PDG average [3] remains substantially unchanged since 2010 [4]. As a consequence, the uncertainty on αs is now the dominant source of uncertainty for several Higgs boson production cross-sections [5]. 
Possibly the cleanest [6, 7] determinations of αs come from processes that do not require a knowledge of the PDFs, such as the global electroweak fit [8]. These are free from the need to control all sources of bias which may affect the PDF determination and contaminate the resulting αs value. A determination of αs jointly with the PDFs, however, has the advantage that it is driven by the combination of a large number of experimental measurements from several different processes. This is advantageous because possible sources of uncertainties related to specific measurements, either of theoretical or experimental origin, are mostly uncorrelated amongst each other and will average out to some extent in the final αs result. In addition to the above, the simultaneous global fit of αs and the PDFs is likely to be more precise and possibly also more accurate than individual determinations based on pre-existing PDF sets, many of which have recently appeared [9–15]. This is due to the fact that it fully exploits the information contained in the global dataset while accounting for the correlation of αs with the underlying PDFs.
From the Conclusion:
The main limitation of our result comes from the lack of a reliable method to estimate the uncertainties related to missing higher order perturbative corrections. Theoretical progress in this direction is needed, and perhaps expected, and would be a major source of future improvement. For the time being, even with a very conservative estimate of the theoretical uncertainty, our result provides one of the most accurate determinations of αs (mZ) available, and thus provides valuable input for precision tests of the Standard Model and for searches for new physics beyond it.
The quark masses are another set of critical constants in the Standard Model, and in QCD in particular, which are not known particularly precisely and except in the case of the top quark, cannot be measured directly. A new paper also makes progress on that front:
We calculate the up-, down-, strange-, charm-, and bottom-quark masses using the MILC highly improved staggered-quark ensembles with four flavors of dynamical quarks. We use ensembles at six lattice spacings ranging from a0.15 fm to 0.03 fm and with both physical and unphysical values of the two light and the strange sea-quark masses. We use a new method based on heavy-quark effective theory (HQET) to extract quark masses from heavy-light pseudoscalar meson masses. Combining our analysis with our separate determination of ratios of light-quark masses we present masses of the up, down, strange, charm, and bottom quarks. 
Our results for the MS¯¯¯¯¯¯¯-renormalized masses are  
mu(2 GeV)=2.118(38) MeV,  
md(2 GeV)=4.690(54) MeV,  
ms(2 GeV)=92.52(69) MeV,  
mc(3 GeV)=984.3(5.6) MeV, and  

mc(mc)=1273(10)  MeV, with four active flavors, and
  
mb(mb)=4197(14) MeV with five active flavors. 
We also obtain ratios of quark masses mc/ms=11.784(22)mb/ms=53.93(12), and mb/mc=4.577(8). 
The result for mc matches the precision of the most precise calculation to date, and the other masses and all quoted ratios are the most precise to date. Moreover, these results are the first with a perturbative accuracy of α4s. 
As byproducts of our method, we obtain the matrix elements of HQET operators with dimension 4 and 5: Λ¯¯¯¯MRS=552(30) MeV in the minimal renormalon-subtracted (MRS) scheme, μ2π=0.06(22) GeV2, and μ2G(mb)=0.38(2) GeV2. The MRS scheme [Phys. Rev. D97, 034503 (2018), arXiv:1712.04983 [hep-ph]] is the key new aspect of our method.
A. Bazavov, et al., "Up-, down-, strange-, charm-, and bottom-quark masses from four-flavor lattice QCD" (February 12, 2018).

The global average PDG values as of 2017 are:

Up quark mass (2 GeV) 2.2 + 0.6 - 0.4 MeV

Down quark mass (2 GeV) 4.7 + 0.5 - 0.4 MeV

Strange quark mass (2 GeV)  96 +8 -4 MeV

Charm quark mass (at charm quark energy scale) 1,280 +/- 30 MeV

Bottom quark mass (at bottom quark energy scale) 4,180 + 40 -30 MeV

The ratios from PDG are:

Charm mass/strange mass: 11.72 +/- 0.25

Bottom mass/charm mass: 4.53 +/- 0.05

The new results are consistent with the PDG values but more precise.
+0.6+0.6

The imprecision in the strong force coupling constant value is one of the main sources of the imprecision in the non-top quark mass estimates, which has to be inferred from the behavior of bound quarks in composite particles made up of quarks bound by gluons called hadrons. The masses of scores of hadrons have been measured with spurious accuracy that are exact for the practical purpose of determining quark masses but without a more precise measurement of the strong force coupling constant, the precise measurements of the hadron masses can't be translated into equally precise measurements of the quark masses.

Ultimately, there are also uncertainties in the determinations of all of these constants that arise, both directly and indirectly, from truncating infinite series formulas in the QCD calculations involved that are usually done to NNLO or NNNLO in this kind of study. This accounted for half of the error in the most recent strong force coupling constant determination, and is also an independent source of error in addition to the indirect effect on the strong force coupling constant determination, on the quark mass determinations. There are methodologies that can minimize the additional error due to calculation imprecision by, for example, comparing pairs of hadrons whose mass calculations are identical in most respects except for a residual attributable to the mass difference between otherwise identical quarks, however, which is why the percentage error in the mass ratios of the quark masses is lower than the percentage error in the absolute quark masses.

Meanwhile, the diphoton Higgs boson decay channel signal strength predicted by the Standard Model is now an almost perfect match to run two data from the ATLAS experiment at the LHC has been collected:
The global signal strength measurement of 0.99±0.14 improves on the precision of the ATLAS measurement at s=7 and 8 TeV by a factor of two. . . . The cross section for the production of the Higgs boson decaying to two isolated photons in a fiducial region closely matching the experimental selection of the photons is measured to be 55±10 fb, which is in good agreement with the Standard Model prediction of 64±2 fb.
This observable is purely function of the Higgs boson mass in the Standard Model, together with the spectrum of Standard Model particles in the Standard Model:

The dominant source of error in the Higgs diphoton decay signal study is statistical, which means that the precision of these measurements will increase significantly as more data is collected at the LHC.