Quantum Diaries

Some years ago, when I decided to start blogging, I wrote about an interesting advertisement that Ford Motor Company put up in all major magazines (it was even placed on the side of their headquarters in Dearborn, MI):

Here is what I said in that post of mine from several years ago: “What is interesting about this ad is the equations that this lady is writing — they look like the equations from the famous Peskin and Schroeder’s book on Quantum Field Theory (QFT), equations describing renormalization of phi^4 theory! How did Ford get a hold of them?

As it turns out, I happen know the answer. This ad was made by a company that is headquartered in Detroit — I have a business card of one of the authors of this ad!

What happened is that a couple of months ago I was sitting in my office at Wayne State University, looking over my QFT notes that I’m supposed to teach next Fall. A guy showed up at my door and asked to “write down a complicated-looking equation.” Now, that’s not a usual question that I get when I sit in my office during the lunchtime! He quickly explained that he works for this advertisement company (called JWT) and they were contracted by Ford to produce a series of ads that should highlight the talent of Ford engineers and at the same time appeal to young people. (He showed me a prototype of an ad with that girl sitting next to the blackboard.) So his boss sent him to the closest university (which happen to be WSU, we are located 5 min down Woodward Avenue from their office) to fish out a “complicated equation.” The rest is simple — I use Peskin and Schroeder as a main text for my graduate QFT  course, so that list of equations was indeed about renormalization of phi^4 theory… I must add that I received no monetary (or any other) compensation…

Amazing, isn’t it?”

The reason I re-post part of that old post is the following. I recently went to Florida to participate in CIPANP-2012 conference (I’ll post my impressions of this conference later this week). Now, Kennedy Space Center is on Cape Canaveral in Florida, so I rented a car and went to visit that marvelous place. The place is truly amazing! Lots of things to see. The place is still making history: I visited it just a couple of days after the historic launch of the Space X‘s Dragon capsule.

I also visited a gift shop and bought the following souvenir there:

See how many mistakes they got in there? And it’s not “rocket science”, it’s freshman physics! Quite embarrassing… Clearly, people from that JWT advertising agency in the example above take their job responsibilities much more seriously.

See that NASA seal in the upper left corner? Since I am sure that NASA scientists know physics, I take it as indication that they never visit their gift shop.

I’m blogging from the site of CHARM-2012 conference, which has just started in Honolulu, Hawaii. This is a fantastic conference at a fantastic place! The conference will have four full-packed days filled with many aspects of physics related to charmed quark. As I reported earlier, many exciting recent results are associated with charm quark.

Why is the conference taking part in Hawaii? Besides being a nice place in general, it is almost exactly half way between Japan and the US. This meeting alternates between Asian, US and European locations, and last meeting, in 2009, was in Beijing — so it is US’ turn.  There will be many talks from KEK‘s Belle collaboration (which University of Hawaii is a member of), LHC experiments, as well as from Tevatron experiments. Besides, world’s only operating charm experiment (BES 3) is located in Beijing, China. Indeed, there would be many theory talks as well. It shapes to be a very nice conference — and I’ll be reporting about exciting results to be discussed here.

In a couple of Hours we shall know more than we did before — the CERN experiments, ATLAS and CMS are about to announce their findings about the Higgs boson. In particular, its mass. Why is it interesting? The mass of Higgs, a fundamental particle in the Standard Model (SM) and a manifestation of a Higgs mechanism (discovered by at least five people besides Dr. Peter Higgs), cannot be predicted within the Standard Model. Similarly to masses of quarks and leptons, it comes out from the combination of unknown parameters of the SM.

Yet, Higgs boson would affect precision measurements — its effects could be seen via its quantum effects.  So physicists would come out with pictures like the one that accompany this post (from which, incidentally, one can learn that the most likely value of the the Higgs mass given by the minimum of that plot, is already excluded by the direct measurements; what can one say — it’s a tough game).

In principle, Higgs boson mass (or mass of a Higgs-like particle) can be predicted in some models beyond the Standard Model. So, if you have any last-minute predictions, please through your hat in the ring! There are still about two hours before it becomes a “postdiction.”  My long-time prediction (as of two years ago) was m_H = 125 +- 5 GeV. What is it based on? A principle that life is tough — the Nature is not always kind to us and we have to work hard to measure what we want to measure. It is true for most measurements/parameters that were studied before, including the most recent study of CP-violation in charm. How scientific is this prediction? I’d say almost as scientific as those based on anthropic principle. 🙂

Meanwhile, let’s see what CERN physicists have to say. Tune in here and let’s hope that we don’t overwhelm CERN’s servers.

One of CERN’s collaborations, the LHCb, has reported observation of direct CP-violation in the decays of charmed mesons at the Hadronic Collider Physics Symposium 2011 (HCP 2011) in Paris today. This is a fantastic news! While I am not at HCP 2011, kind folks at LHCb let me know about this fantastic measurement — since charm physics is my specialty.

So, what are we talking about here?

First things first. CP (or Charge Parity) is a set of (discrete) transformations performed on a theory’s Lagrangian — a function that describes what particles we have in a theory and how they interact. If your Lagrangian is symmetric  under this transformation, then particles and antiparticles — matter and antimatter — have the same properties. If not — interactions of matter particles are different from interactions of antimatter particles.  This possible difference is a crucial property of a theory because, according to three Sakharov criteria, the Universe could evolve in what we see around us only if matter and antimatter have different interaction properties. Otherwise, at best, we’d have big chanks of antimatter floating around — or at worst would not not exist at all.

This is why many huge experiments built to study CP violation. Big national labs’ flagship experiments were designed to search and study CP-violation (BaBar at SLAC, Belle at KEK, LHCb at CERN), with hopes to see glimpses of New Physics that could explain matter-antimatter asymmetry in the Universe. This new result from LHCb can in principle provide one.

LHCb experiment

So, what did LHCb see? The reported analysis looks at the difference of a difference — i.e. a difference of CP-violating asymmetries in kaons and pions. The CP-violating asymmetry is defined as the difference between decay widths (roughly speaking, decay probabilities) of a neutral D-meson to decay into a final state, say positive K-meson and a negative K-meson and the same quantity for the D-anti-particle to decay to the same final state. This quantity is also defined for the final state of two pions — and it is CP-violating!

The structure of this CP-violating asymmetry, a_CP, is not that simple. Because D⁰ is a neutral particle it can, in principle, mix with its antiparticle (see here) — and this antiparticle can also decay into the same final state! This process can be also CP-violating (this type of CP-violation is called indirect CP-violation). So the result would depend on both types of CP-violation!

Moreover, experimentally, the asymmetries like this are not easy to measure — there are experimental systematics associated with D-production asymmetries, difference of interactions of positive and negative kaons with matter, etc. For this reason, experimentalists at LHCb decided to report the difference of CP-violating asymmetries, in which many of those effects, like productions asymmetries, would cancel. So, here is the result:

Δa_CP = -0.82 ± 0.21 (stat) ±0.11 (syst)%

In other words, this quantity is 3.5 sigmas away from being zero. The first question that one should ask is whether this quantity is consistent with previous measurements. The biggest question, however, is whether this quantity is consistent with Standard Model expectations.

There is a bunch of previous measurements available for a_CP (KK) and a_CP (ππ) separately. The thing is that

a_CP (KK) = – a_CP (ππ)

or approximately so. So by subtracting those quantities we not only subtract the experimental uncertainties, but also enhance the signal! However, looking at the table on page 6 of the talk, one can immediately realize that this measurement is at least consistent with the previous ones.

Is it a sign of something beyond the Standard Model? This one is hard to answer. I usually put an upper bound on the SM value (that is, absolute value) of asymmetries like a_CP (KK) at 0.1% — which would make Δa_CP to be about 0.2%. Is it consistent with LHCb findings? Maybe. The size of this asymmetry is notoriously difficult to estimate due to hadronic effects. Maybe it is a sign of New Physics — this could be an exciting conclusion, as we have never seen CP-violation in up-quark sector.

It is interesting that the first “big” result from LHC comes in the realm of charm physics, not Higgs searches. Moreover, all “big” results in the last decade were from the experiments searching for New Physics indirectly, in the “intensity frontier” (this is lingo of US Department of Energy) — with most of them coming from charm physics. Maybe at the very least LHC-b should be renamed as LHC-c?

4 October 2011 is a day to remember. And I’m not talking about unveiling of the new iPhone, although it is also quite a remarkable event. Today, a 2011 Nobel Prize in Physics was awarded. As expected, in its annual failure, Thompson Reuters got it wrong in predicting 2011 Nobel Prize in Physics (to give them credit, they do put up the names of the right people, but always in the wrong year; this year they were predicting people from quantum entaglement). Anyways, this year’s Nobel Prize is totally deserving. The Nobel Prize in Physics 2011 was awarded jointly to Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae.”

This Nobel Prize is for the 1998 analysis of data from two collaborations, Supernova Cosmology Project (SCP), headed by Perlmutter, and High-z Supernova Search Team, headed by Schmidt and Reiss. The analyses centered on the the so-called Ia-type supernovae that have consistent peak brightness, which makes them “standard candles” of the Universe. This is an important property, which allows unambiguous measurement of distances (via the Hubble relation between the distance and the redshift) to the galaxy hosts of those supernovae. Using this data, they concluded that the Universe is going through the stage of accelerated expansion! This is a very interesting fact, especially taking into account the fact that the gravitational interaction is attractive!

This led to reevaluation of what we know about the Universe. It is widely accepted now that Dark Energy (i.e. something that permeates space and tends to increase the rate of expansion of the universe) accounts for about 74% of the total mass of the universe! Recalling that Dark Matter is responsible for about 22% of total mass gives us a fact that we really know almost next to nothing about the place we live in…

What is Dark Energy? This is a very good question. The simplest possibility is that it is the old good cosmological constant introduced by Einstein in the beginning of the last century. This leads to a particularly simple model of the Universe called Lambda-CDM model. Whether or not it is true remains to be seen. At any rate, Dark Energy/Dark Matter are currently one of the most exciting avenues for research in astrophysics (which is, of course, my subjective opinion!).

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Meanwhile, the annual 2011 Ig Nobel Prizes were awarded on September 29, 2011. Among the most remarkable are

“PHYSICS PRIZE: Philippe Perrin, Cyril Perrot, Dominique Deviterne and Bruno Ragaru (of FRANCE), and Herman Kingma (of THE NETHERLANDS), for determining why discus throwers become dizzy, and why hammer throwers don’t.”  As expected, for a work of this magnitude, the prize-winning research was published in the widely-read physics journal Acta Oto-laryngologica.

“MATHEMATICS PRIZE: Dorothy Martin of the USA (who predicted the world would end in 1954), Pat Robertson of the USA (who predicted the world would end in 1982), Elizabeth Clare Prophet of the USA (who predicted the world would end in 1990), Lee Jang Rim of KOREA (who predicted the world would end in 1992), Credonia Mwerinde of UGANDA (who predicted the world would end in 1999), and Harold Camping of the USA (who predicted the world would end on September 6, 1994 and later predicted that the world will end on October 21, 2011), for teaching the world to be careful when making mathematical assumptions and calculations.” This prize is quite timely, as the world once again is predicted to end 21 December 2012, although, frankly, they could have waited one year for this one.

Once again, the biology prize went for sexuality-related research. This time, among certain type of beetles and certain types of beer bottles (which should make a nice commercial of the type “Fosters is Australian for beer” (C)):

“BIOLOGY PRIZE: Darryl Gwynne (of CANADA and AUSTRALIA and the UK and the USA) and David Rentz (of AUSTRALIA and the USA) for discovering that a certain kind of beetle mates with a certain kind of Australian beer bottle.”

And my personal favorite is this year’s literature prize:

“LITERATURE PRIZE: John Perry of Stanford University, USA, for his Theory of Structured Procrastination, which says: To be a high achiever, always work on something important, using it as a way to avoid doing something that’s even more important.”

I would like to remind my readers that so far, there is only one “Grand Slam winner” — a person who got both Ig Nobel and a Nobel prizes: last year’s recipient of the Physics Nobel Prize Andre Geim.

Today, September 30th, is the last day of operations of the largest US particle accelerator, the venerable Tevatron. Form many years it defined the American (and world’s) program in high energy particle physics. It saw its share of discoveries and trained a  ton of graduate students. For a theorist, Tevatron has continuously been a source of new data to explain or a machine that can confirm or rule out a model. What are the most significant papers that came out of the Tevatron?

In order to answer this question, let us use a tool that every theorist has in its disposal: SLAC SPIRES database. To be exact, we’ll use its modern incarnation, the INSPIRE. A quick search reveals that the most influential paper that came out of Tevatron (and the forth most influential that came out of Fermilab) is “Observation of top quark production in pˉp collisions” by  the CDF Collaboration, closely followed by a similar paper “Observation of the top quark” from the DO collaboration. Those papers from the two biggest Tevatron experiments describe the discovery of the sixth quark, the heaviest known so far — and probably the heaviest we shall ever see!

What is more striking is that while Tevatron was built to explore the “energy frontier“, i.e. to directly observe New Physics particles, the most influential papers that came out of CDF and D0 collaborations have to do with flavor physics (see also my recent colloquium)! In particular, papers on top quark discovery, discovery and precision measurements of of Bs-meson oscillations (see CDF and D0 papers),  measurements of J/psi (a bound state of charm and anti-charm quars) and b-quark production cross sections were sited by hundreds of researchers worldwide. Many of those analyses — as well as others, e.g. related to precision measurements of properties of W-bosons — greatly influenced indirect searches for physics beyond the Standard Model. I use those results routinely in my work! So maybe the decision to move Fermilab towards “intensity frontier” (i.e. careful precision studies of particle processes at lower energies to catch a glimpse of virtual New Physics particles) is the wise move based on the legacy of Tevatron.

While the most obvious answer to this question is “to ski”, it is, nonetheless, not the correct one. Yes, skiing is great here in the winter (and hiking is great in the summer), but most of the time physicists come here to work. The reason is Aspen Center for Physics. I write “here” because I’m currently participating in one of the programs organized by the Center (the program is called “Flavor Origins” — it brought together theorists working on the problems of neutrinos, heavy and light quarks, CP-violation, etc.). The Center, which exists here since 1961, organizes workshops and conferences. But the main reason that theorists (and occasional experimentalists) come here is to talk to other theorists.  In short, it is as if you are visiting a huge theory group — you can work individually or with your colleagues, but you can always knock on an office door and bounce your ideas off someone else visiting the Center, etc. It is great to have such a concentration of theorists of different trades. And it leads to breakthroughs and simply good papers. As it is said on the Center’s website:

“Many seminal papers have been written in Aspen, which has grown to be the largest center for theoretical physics in the world during its summer sessions. Among many other subjects, the theories of superstrings, chaos, evolution of stars and galaxies, and high temperature superconductivity have all made large strides in recent Aspen seasons.”

There is almost always someone with an expertise in a subject that you have a question about. And that makes this Center great. And, of course, hiking and skiing is also good. The only “downside” (note the quotes) is that you can meet a real bear (even at the Center) or other wildlife. Today a snake came to check out a lecture on conformal field theories…