Of Particular Significance

Author: Matt Strassler

A busy week and a computer crash has delayed my report on a number of new results on the Higgs particle from the current Moriond conference on particle physics, but the quiet not only on my blog but on some others should be a clue: the new results shown do not significantly change what we have previously known, and to the extent they do, they do not point to anything unexpected.

The rate for events with two lepton/anti-lepton pairs (data is the black dots, with uncertainties given by the black bars) as a function of the mass-energy of a particle that might have produced them; the Z particle is the bump around 90 GeV.  The bump near 125 GeV due to the Higgs-like particle is now difficult to miss, even if one ignores the blue and red lines which are there to guide the eye.
The rate for events with two lepton/anti-lepton pairs (data from CMS is the black dots, with uncertainties given by the black bars) as a function of the mass-energy of a particle that might have produced them; the Z particle is the bump around 90 GeV. The bump near 125 GeV due to the Higgs-like particle is now difficult to miss, even if one ignores the blue and red lines which are there to guide the eye.

As a summary before I mention a few details, let me say that all in all, I think it is pretty safe now to award the Nobel prize to the theoretical physicists behind this story; last year was too early, but this year is not. Confidence is steadily growing that this “Higgs-like” particle really is a type of Higgs (Brout-Englert) (Guralnik-Hagen-Kibble) boson [what’s a boson?], and most alternatives are now significantly disfavored.  Whether it is the one and only type of Higgs particle in nature, and whether it is exactly of Standard Model type (the simplest possible type of Higgs particle), we cannot yet be sure, but its properties are more or less in line with what Higgs and friends proposed, enough to give them credit for having correctly imagined (to greater and lesser degrees) how nature might provide mass to force-carrier particles like the W and Z particles, and how we might test this notion experimentally. We should also remember some theorists who came before them and some who came after, but that’s a story for another day.

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Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON March 8, 2013

As many of you will have already noticed, today’s Science Times section of the New York Times newspaper is devoted to articles by Dennis Overbye on the search for the Higgs particle.  At first read, the articles seem pretty good; several key players are interviewed (though inevitably, given page constraints, a number of important players in the experiments are not mentioned) and the science seems mostly accurate, with a few small errors, omissions, or misleading ways of saying things in the glossary and elsewhere.  I’m busy preparing a new public talk for tomorrow, so I’ll have to reserve any detailed comments for later in the week.

But one thing you will notice, if you read the long article which describes the ins and outs of the search process, is that several of the responsible scientists quoted indicate, directly or indirectly, that the December 2011 data did not convince them that a Higgs particle had yet been found.  That was the position I took on this blog, and I reported to you that most responsible scientists I had spoken to (which didn’t happen to include any of the ones quoted in the Science Times today) viewed the December data as inconclusive — meaning that it was still quite possible that the apparent signal of a Higgs particle might evaporate.  Almost every other major particle physics blogger disagreed with me, both on my opinion and on my characterization of others’ opinions.  But I stand by my statements: that though the data reported in July 2012 was essentially definitive, the data in December 2011 was, not only from my perspective but from that of many serious scientists, suggestive yet inconclusive.  And you can now read that in the New York Times.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON March 5, 2013

The Structure of Matter series continues: last week’s article on the basics of atomic nuclei is now supplemented with an article discussing the “residual” strong nuclear force which binds protons and neutrons inside of nuclei.  It further explains why nuclei are so small compared to atoms.  Or rather, it explains it in part, because I have to also explain why protons and neutrons themselves are so small — which I will do soon enough.

As always, readers are encouraged to comment on things that don’t seem clear or correct.  And any nuclear physics experts who want to weigh in on my presentation — suggesting how it might be improved or extended, or identifying misconceptions on my part — are encouraged to speak up (publicly or privately as you prefer).

Meanwhile, we’re entering the March conference season, when many new results from the Large Hadron Collider [LHC] (based on analysis of last year’s data) and from other important experiments will start appearing.  Since the LHC’s proton-proton collisions went til December in 2012 (in 2011 they stopped in October) the time for LHC data analysis has been rather short.  I therefore think it likely that any really surprising results from the LHC will be delayed for extra scrutiny — and may not appear until late spring or summer, when there are other conferences.  But I could be wrong!  And one thing we’re all waiting for is the measurement by CMS (one of the two general purpose LHC experiments) of the rate for the recently discovered Higgs particle to decay to two photons.   However, we won’t see that result until CMS is absolutely confident in it.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON March 4, 2013

Posts have been notably absent, due mainly to travel with very limited internet; apologies for the related lack of replies to comments, which I hope to correct later this week.

Meanwhile I’ve been working on a couple of articles related to the nuclei of atoms, part of my Structure of Matter series, which serves to introduce non-experts to the basics of particle physics.  The first of these articles is done.  In it I describe why it was so easy (relatively speaking) to figure out that nuclei are made from certain numbers of protons and neutrons, and how it was understood that nuclei are very small compared to atoms.   Comments welcome as always!

A related article, which should appear later this week, will clarify why nuclei are so tiny relative to atoms, and describe the force of nature that keeps them intact.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON February 25, 2013

We’re gearing up for another big-time storm predicted for the northeastern United States — we’ve had more than we need over recent months — so before we perhaps lose power (or you do)…

…I want to remind you that Sean Carroll and I were interviewed last night by science writer Alan Boyle.  My impression is that the conversation (which touched on issues involving the Higgs particle, dark matter, and the nature of science as a process) went well, and I hope that you enjoy it.  Just click on this link http://www.blogtalkradio.com/virtually-speaking-science/2013/02/07/sean-carroll-matt-strassler-alan-boyle , endure the commercial, and you should get the radio broadcast (just about 60 minutes).

As for that big blizzard threatening Boston with over two feet (0.6 meters) of snow, and winds over 60 miles (100 km) per hour, along with some coastal flooding, it is interesting that the European Weather Model, which did the better job on forecasting Hurricane Sandy, appears to be doing better on this one too.  The US-based Global Forecasting System may again have been a bit late to the party.  The difference in the scientific approach of the two forecasting models was described in a previous post, after Sandy, thanks to one of my readers; if you missed it then, you may find it worth a read now.

Well, it will be interesting to see how the reality plays out; but given how well the European model forecast Sandy, it would seem prudent not to underestimate this storm.  Be careful out there!

[Note Added: Julianne Dalcanton, professor of astronomy at the University of Washington, pointed me to her university colleague Cliff Mass’s article about various problems at the US National Weather Forcasting agency.  See also this article.  This is seriously disturbing stuff, if you live in the U.S.]

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON February 7, 2013

A quick reminder that tonight at 6 Pacific/9 Eastern, Sean Carroll and I will be interviewed by Alan Boyle on the online radio show “Virtually Speaking Science”.  Topics will cover the LHC and other hot issues in physics, astrophysics, gravity and cosmology, as well as the scientific process.  See Monday’s post for the link to the show and other details.

Continuing my more careful summary of the Higgs Symposium (held January 9-11 at the University of Edinburgh, as part of the new Higgs Center for Theoretical Physics), and improving on my quick blog posts that I put up during and just after the symposium (#1, #2 and #3), I’ve finished another article about our current knowledge and ignorance concerning the recently discovered Higgs-like particle.  The new article

covers a topic that I spoke about extensively at the Symposium.  The other completed articles in this series are

One or two more segments to go.

 

 

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON February 6, 2013

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