Saturday, August 13, 2016

A new top quark mass measurement from CMS

A first measurement is presented of the top quark mass using the decay channel t to (W to l nu) (b to J/psi+X to mu+mu- + X), in events selected in proton-proton collisions and recorded with the CMS detector at the LHC at a center-of-mass energy of 8TeV. The data correspond to an integrated luminosity of 19.7 inverse femtobarns, with 666 ttbar and single top quark candidate events containing a reconstructed J/psi candidate decaying into an oppositely-charged muon pair. The mass of the (J/psi+l) system, where l is an electron or a muon from W boson decay, is used to extract a top quark mass of 173.5 +/- 3.0 (stat) +/- 0.9 (syst) GeV
CMS Collaboration, "Measurement of the mass of the top quark in decays with a J/psi meson in pp collisions at 8 TeV" (August 11, 2016).

A combined margin of error of about +/- 3.13 GeV makes the new result almost useless, however, and even in a combined measurement, it would be weighted very minimally as a result of the lack of precision.

Still, the fact that the central result is quote close to the global average in a decay path not previously measured, does help make the existing estimate more robust and supports the integrity of the Standard Model in which the mass is calculated.

Tuesday, August 9, 2016

Prestige Necropolis In North America Better Understood

In Egypt, the pyramids were the ultimate prestige grave sites that shed light on their ancient civilization. Mound 72, discovered by archaeologists in 1967, is what appears to be Cahokia's greatest prestige necropolis.

Cahokia, in modern day Saint Louis, was the capitol of a great copper age, pre-Columbian maize and pumpkin farming civilization of North America which flourished around 1,000 CE. This civilization extended to more or less the entire Mississippi basin and has trade links and cultural influence, at least, that extended as far as the Carolina coast. At its peak, about 75,000 people lived in the capitol, making in a world class city by pre-Bronze Age standards.

Predecessors of the Cahokia civilization may have even been a cultural source for the Mayans, as its predecessor civilizations in Louisiana produced the earliest discovered pyramids in the Americas.

Until now, Mound 72 was believed to have six bodies, all men, presumably kings or heroes. But, further research has determined that there are at least twelve bodies there, including many male-female couples.

This tends to show that there may have been an aristocracy in this civilization in which aristocratic men and women played important roles, until male warrior dominated societies arose in the vicinity of this empire after its collapse. Cahokia's decline began around the 1160s and 1170s during a major New World drought, and eventually collapsed as an urban complex around 1350 CE around the time of the Little Ice Age. The last vestigial remnants of this culture were wiped out when European diseases struck relict communities shortly after Columbus and the conquistadors who followed him made contact with the New World.

The abstract and citation of the source paper are as follows:
The Beaded Burial central to F101 within Cahokia's mound 72Sub1 has been fundamental to some cosmological explanations of the founding of this North American precolumbian polity. The central burial, identified as two males surrounded by retainers, has been interpreted as paradigmatic of a paramount chiefdom, or conversely, as a mythic cosmogram. Recent bioarchaeological reanalysis and two independent osteological studies of F101 and associated burials have identified the presence of male/female pairs, numerous females, and at least one child, suggesting that previous explanations privileging the male Red Horn association should be reexamined. We suggest that 72Sub1 is most likely correlated with ritual practices promoting world creation, renewal, and fertility symbolism.
Thomas E. Emerson, et al., "Paradigms Lost: Reconfiguring Cahokia's Mound 72 Beaded Burial." 81(3) American Antiquity 405 (2016).

Chinese Legendary History Coroborated

China’s historiographical traditions tell of the successful control of a Great Flood leading to the establishment of the Xia dynasty and the beginning of civilization. However, the historicity of the flood and Xia remain controversial. Here, we reconstruct an earthquake-induced landslide dam outburst flood on the Yellow River about 1920 BCE that ranks as one of the largest freshwater floods of the Holocene and could account for the Great Flood. This would place the beginning of Xia at ~1900 BCE, several centuries later than traditionally thought. This date coincides with the major transition from the Neolithic to Bronze Age in the Yellow River valley and supports hypotheses that the primary state-level society of the Erlitou culture is an archaeological manifestation of the Xia dynasty.
Qinglong Wu, "Outburst flood at 1920 BCE supports historicity of China’s Great Flood and the Xia dynasty" Science (05 Aug 2016) Vol. 353, Issue 6299, pp. 579-582 via Dienekes' Anthropology Blog.

Lubos Motl on New Experimental Physics Results

All babies are being killed and embryos are being aborted these days.
- The Reference Frame.

In other words, beyond the Standard Model physics proposals are being ruled out left and right.

Sabine Hossenfelder at Backreaction likewise bemoans the arrival of the "Nightmare Scenario" in which the LHC is discovering no new physics other than the Higgs boson.  She thinks that there's a moral to the story:
That the LHC hasn’t seen evidence for new physics is to me a clear signal that we’ve been doing something wrong, that our experience from constructing the standard model is no longer a promising direction to continue. We’ve maneuvered ourselves into a dead end by relying on aesthetic guidance to decide which experiments are the most promising. I hope that this latest null result will send a clear message that you can’t trust the judgement of scientists whose future funding depends on their continued optimism.
I agree that particle physics has put too many of its eggs in the same SUSY/string theory basket, and even more on theories that have the same philosophical motivation.