Physics Seminar: Free Neutron Decay

Back in High School you probably learned that the atoms that make up everything around us are themselves made up of three types of particles, Protons and Neutron sit at the center of the atom in the nucleus while electrons go spinning around the nucleus. What you might not have learned in High School is that the Protons and Neutrons are made up of particles called quarks and that sometimes Neutrons can ‘decay’ into a Proton, electron and an anti-Neutrino!

Two days ago I attended a physics seminar at my old Alma Matter Drexel University entitled “The Life and Death of the Free Neutron’ given by Doctor Nadia Fomin, Assistant Professor at the University of Tennessee and a researcher at Oak Ridge Laboratory and the National Institute of Standards and Technology (NIST).

For those of you who have never had the pleasure of attending a science seminar let me take a brief moment to give you an idea of what it’s like. A visiting scientist is invited to come and give a talk by a member of the local faculty whose own research is in the same general field. First there is an introduction by the local faculty member mentioning where the visitor is currently working, where they received their degrees and a short description of their research.

Then we get the meat! For the next 45 minutes or so you get to listen to a lecture on the latest research being conducted, the cutting edge of science in action. If the visitor is an experimentalist as Doctor Fomin was you get to hear about the development of their instruments as well as their results but if the visitor is a theoretician you could be treated to 45 minutes of solid math, what could be better than that! After presenting their results the lecturer will then take about 5 minutes to relate what they think their results mean, how they effect what we know about the Universe. Finally there’s about ten minutes given to questions from the audience.

The question period can be the most interesting. I have attended several seminars where a member of the audience was well known to disagreed with everything the visiting speaker was saying and everybody else was just waiting for the clash when the two scientists argued their case. Now there’s no yelling or cursing, everything is calm and deliberate but this is the cutting edge of science in action. Two opposing models of how the Universe behaves, each side has some evidence and a lot of theories as support but neither side has enough to convince the other.

So that’s what attending a scientific seminar is like. Let’s get back to Professor Fomin and her measurements of the decay half life of a free Neutron. Ever since the Neutron was discovered by James Chadwick in 1932 scientists have know that a free Neutron, one that was not confined to the nucleus of an atom, would after some time decay into a Proton and an electron and it was some missing energy in this decay that led Wolfgang Pauli to predict the existence of the Neutrino (although in Neutron decay it’s actually an anti-Neutrino that gets produced). To understand the reaction take a look at the Feynman diagram below.

Free Neutron Decay

The Neutron and Proton are both composed of three quarks, two Ups and a Down for the Proton and two Downs and an Up for the Neutron. Now the decay of the Neutron takes place via the ‘Weak Nuclear Interaction’ and it’s half life was first measured after world war 2 to be something around 15 minutes. That doesn’t sound very scientific does it, well Neutrons are very hard to measure, they’re much smaller than an atom, they have to electric charge so it takes a lot effort to learn almost anything about them.

We have made progress since the 1940s, and Doctor Formin and her colleagues are a part of that progress. The best current estimate of the free Neutron half life is between 870 and 880 seconds and the hope is that with new instruments before long that range will be reduced to 0.3 seconds.

Why should we care? What difference does it make whether the Neutron’s half life is 874 or 875 seconds? Well, it does matter because the half life of the Neutron plays an important role in models of the early development of our Universe. Shortly after the Big Bang the universe was a foaming sea of elementary particles that quickly became atoms of hydrogen and helium along with a bit of lithium. Right now the biggest unknown in just how that process took place is the Neutron half life! Also, numerous theories uniting gravity to quantum mechanics, the so called ‘Theories of Everything’ make predictions about the half life of the Neutron and with a better measurement of the half life we can eliminate some of the wrong theories.

Physics began some four hundred years age with Galileo making measurements of falling objects. Measurement is central to what physics is and how it works. I look forward to hearing about Doctor Formin’s results when she gets her new instruments.

Welcome to 2017. What to look forward to in Science in the coming Year

Well it’s 2017 and I thought it might be nice to take some time to see what scientific discoveries and achievements we can expect in 2017.

Science in 2017

For me the most exciting event may be the upcoming TOTAL ECLIPSE of the SUN going across the USA on August the 17th. The path of totality is pretty narrow but it goes from sea to shining sea so if you really want to see it you only need to drive a day or two to get there. Here’s a link to a site giving all the details.

http://www.eclipse2017.org/2017/path_through_the_US.htm

Other Space events we can look forward to include the Cassini’s spacecraft’s final orbits through Saturn’s rings and it’s final plunge into the planet itself. Cassini has already given us so many discoveries but I’m sure there will be a few more to come.

Also coming up this year will be a Chinese unmanned Lunar mission which will hopefully bring back some samples making China only the third nation to bring back pieces of the Moon. China also plans on continuing their missions to their new Tiangong-2 space station including their first unmanned resupply vehicle the Tianzhou-1.

Meanwhile NASA is continuing development of their Space Launch System (SLS) which will eventually be the biggest rocket ever built, a bit bigger than the Saturn 5. The actual first launch of the SLS is scheduled for early in 2018.

Commercial development of space will continue as Space X and Orbital Science continue to resupply the International Space Station. Additionally Space X and Boeing will continue development of their manned spacecraft including unmanned test launches. The first manned missions for both Space X and Boeing are scheduled for early 2018 under NASA’s Commercial Crew Development Program. Space X also intends to perform the first re-launch of one of their previously used Falcon 9 rockets in the first half of 2017 along with the first flight of their Falcon Heavy rocket.

In Physics of course there’s the possibility of new discoveries coming from the Large Hadron Collider (LHC) at CERN. As the world’s largest and most power scientific instrument the LHC in well into it’s second full scale run after completing an upgrade in 2015. The LHC’s initial run only gave us the confirmed detection of the Higgs Boson and with its increased power maybe this year the LHC will finally provide firm evidence for, or against Supersymmetry.

Another series of experiments going on at CERN is the Alpha experiment to study anti-hydrogen. The Alpha team have made great progress in containing and cooling anti-protons and positrons, allowing them to form actual atoms of anti-hydrogen. Anti-matter, just like in Star Trek! The researchers are looking for some tiny difference between anti-hydrogen and normal hydrogen, a difference that could help to explain why our Universe appears to be made almost entirely of matter only.

There will surely be great discoveries in the fields of Paleontology and Archeology as well but it’s hard to predict just which team of researchers will make the big finds. There’s a element of luck in finding fossils and relics as you can imagine.

So we should have a lot to look forward to in the coming months. Scientific progress can sometimes be expected, but just as often you cannot predict what amazing new discoveries will be made. Of course that’s a big part of the fun. I’ll keep you informed of anything interesting I hear about.

 

Have Scientists discovered a Fifth Force of Nature. Probably not, but it would be really cool

During the past week there’s been a lot of talk about Theoretical Physics at the University of California Irvine analyzing data from the Institute for Nuclear Research at Debrecen Hungary, some news articles have even called the UC Irvine analysis a conformation. What’s all this about.

First of all, a little background. Modern Physics recognizes four Forces of nature: Gravity, Electromagnetism and two Forces that only work over the immensely short nuclear distances. These are called the Strong (or color) force and the Weak force.

For nearly forty years now physicists have been looked for something beyond the standard model of particles and forces because the standard model cannot describe gravity at the nuclear scale, nor does it describe the motions of galaxies attributed to “Dark Matter” nor finally the accelerated expansion of the universe attributed to “Dark Energy”.

Now, what the researchers in Hungary were doing was to take nuclei of Lithium and bombard them with energetic protons turning them into nuclei of Beryllium in an excited state, excited state in important. The excited Beryllium nuclei would then sometimes decay into Beryllium in the ground state by emitting a gamma ray photon (a very high energy particle of light) and the gamma ray would then split into an electron-positron pair.

Measuring the energy spectrum of the gamma rays the group in Hungary found a bump at an energy of 17 million electron volts that could be due to a particle other than the gamma photons, an unknown particle. The theoreticians at UC Irvine then looked at the Hungarian data and determined that the new particle would be a force carrying Boson. The data implied not just a new particle but a new force.

First of all, the work at UC Irvine is not a conformation it is an analysis. Conformation requires another laboratory to replicate the data from Hungary. Fortunately the energy levels involved are low enough to allow many laboratories to do the experiment and confirm the Hungarian’s work, or otherwise. we should have an answer soon, a year or so.

This is the fourth time in my career someone has announced a fifth force and each time previously the new force quickly disappeared when subject to additional scrutiny. I’m hopeful, because a new force would be really cool, and I’ll keep reading the published articles, but I’m not holding my breath.