New Boson Discovered – Anyone remember ?? (Pssst ….. it was called Higgs!)

Where were you the day they announced the new discovery??
Will you remember in ten years time?
Can you even remember now ?

Don’t forget this only happened ten months ago !
A big part of me can’t quite believe just how quickly it’s all calmed down again.
(Or was everyone just waiting for the end of the world …………. again! and even that’s now done and gone!)

For such a long awaited and much anticipated discovery….. where’s the follow up?
What has that gained us?

The sad thing is some of us know what the follow up has been but the vast majority of people out there neither know nor care.
If its not about celebrity cooking skating dancing or factor X wannabes, the majority are uninterested.
The science news just doesn’t really get the exposure it ought to. Fact and such a great shame!

The Higgs Field – Fact, Fiction or Football?

Update …. I really should finish a post in better time. Its been nearly a week since England lost to Italy at the football and I can hear the final (Italy vs Spain) on the telly, so please forgive my delay in getting this post out.

After the fuorre surrounding the press release given by the joint CMS and ATLAS teams at CERN last December, I thought I might take a short time to let things calm down a bit before I commented. Although a fair bit longer than I had anticipated waiting, it now seems that the dust has settled, so i thought I’d just have a quick look over the posted results and offer up my 2p worth. This is just before the upcoming ICHEP 2012 conference, which will undoubtedly see the dust well and truly stirred up again and set the cat amongst the pigeons (or at very least, set the world of the quantum spectator ‘flapping’ yet again).
The long and short of the last conference is that although the Higgs could not yet be confirmed, the main two ‘Higgsy’ experiments at the LHC, CMS and ATLAS, had closed the gap in the energy spectrum for where the Higgs can’t be. With the shrinking of the mass availability window to 110 to 145MeV the probability of successfully finding this elusive boson must surely be shrinking too??? It really is running out of hiding places !!!!
One glimmer of hope is the “spike” at approx 125GeV. This increased probability point has been independently seen by both of the main experiments and I guess the last six months furious data collection and analysis by the teams at ALTAS and CMS might (or might not) be further confirmed at the ICHEP conference in 3 days time.

Without the Higgs particle and it’s associated Higgs field, the standard model of particle physics starts to look a bit nervous.

I guess before we go too much further I ought to explain just exactly what a Higgs field is? I can’t really do that without talking about the much talked about (and often misunderstood or misquoted) “Higgs boson”.

I’ll try and keep it as simple as possible (for my own sake as much as anyone else I suspect!).
The Higgs boson or Higgs particle is the theorised member of the group of subatomic particles called bosons. I guess you might have read some of my other posts so you’ll know what a boson is. For those that don’t, a boson is the subatomic particle that carries or mediates a force or quality. In the case of the Higgs, this is mass. The standard model theorises that just as the photon is the carrier for the electromagnetic force, the gluon for the strong nuclear force and the W and Z bosons carry the weak force – there must be a subatomic particle that gives all the hadrons mass. This is what the Higgs does – in theory!
So whats this Higgs field ………? Well, putting aside explanations about SU(2) symmetry breaking etc the simplest explanation is that the Higgs field is a quantum effect that permeates everything. As a particle travels through this field it acquires (inertial) mass. The method by which things gain their mass from Higgs field is called the Higgs mechanism. Lastly, since Higgs is a quantum field it must also have a particle associated with it…….. and there we are back to the Higgs boson.

It is however, proving to be remarkably elusive! But as previously stated …….. without this missing link, the standard model of particle physics starts to fall down as there is nothing to explain the mechanism for why things have mass.
There are a number of problems facing experimental physics in search of the Higgs. The first is that it cannot be directly seen or detected. The only way to mark its discovery is to look for statistically significant events in the the decay remnants of high speed (and therefore high energy) proton/proton collisions, such as those at the LHC at CERN. The best indication of detection is the production of two high energy photons. Alas, This is also the rarest.
It is also very very short lived – somewhere in the region of 10-12 seconds. Lastly, even the mighty LHC produces only very small amounts of these bosons, completing the difficulty of detection.

With this in mind it seems almost a competition between the two experiments (ATLAS and LMS) at CERN to see who, if either, will get a glimpse of the Higgs first.

So….. to go back to the original question of whether the Higgs Field is fact or fiction, the answer is …… we’ll all just have to wait and see. In the mean time, as we’re just about to see the end of Euro 2012, I’ll stop pondering this and get back to the football !!!! 🙂

Detector Death Match @ CERN

With the up and coming ICHEP conference which kicks off with CERN’s intro on the latest round of Higgs searching, I felt I just had to post the following pic I hastily created this afternoon.
(Its never a good idea to let me get bored!)

On a slightly more serious note, it will be very interesting to see which (if either) experiment manages to find some decent evidence of the Higgs particle first.

More Soup (part 3) – The Bosons

Ok so here we are again.
We’ve done the leptons…….
We’ve looked at the hadrons ……..
So what’s next ….?

Meet the Bosons !

So the first question that springs straight away to most peoples lips is the same as it was for the other ‘Soup’ posts concerning leptons and hadrons, namely ….. “what the hell is a boson?”

Great questions says I and unfortunately slightly more difficult to answer clearly to those without at least a modicum of science in their background.
The simplest answer I could come up with is that bosons are fundamental particles that are concerned with ‘force’ unlike the leptons and hadrons (which are collectively called the fermions) which are particles of ‘matter’.

Anticipating the blank stares of some readers ……. How can you have a particle that is concerned with a force ?????
A better way of thinking about it would be to imagine it as a particle that ‘carries’ or ‘mediates’ a force rather than actually is the force itself.

Let kick straight off with some names and descriptions.
The bosons are categorised into six types. There are four ‘gauge’ bosons – the photon (y), the gluon (g), the W boson (W±) and the Z boson (Z0) – all of which have been proved and observed experimentally.
In addition to these primary four, there are two other, much stranger, bosons. These are the Higgs boson (H0) and the graviton (G).

Proton-proton collision at the LHC – the search for the Higgs particle.

Each of these bosons is the force carrier for one of the fundamental forces in the universe.
The photon is the carrier of the electromagnetic force, the W and Z bosons mediate the weak nuclear force and the gluon mediates the strong nuclear force.
The graviton, as it’s name suggests, is theorised to be responsible for the force of gravity but what about the Higgs?
The Higgs boson is postulated to be the fundamental force carrying particle that is responsible for giving mass to all matter. Thats the easy way to put it.
The slightly (and by that I mean a lot!) more complex way of referring to this phenomenon is to say that under the standard model of particle physics, something called the “Higgs Field” gives mass to some fundamental particles via spontaneous symmetry breaking using the Higgs mechanism. Thats pretty mind blowing stuff so I’ll leave that thread right there for the time being. The next post might be my attempt at explaining it a little more clearly – you never know 😉

These forces ……..? What exactly are they? and what do they do?
Good questions.
We might as well start with the ‘biggie’ and the one most people will be familiar with.

Electromagnetism was originally thought to be two separate forces, electricity and magnetism, but is now unified into the single force. It is the force responsible for just about everything in the world around us. It gives shape to all matter through the intermolecular forces between individual molecules. It binds electrons to the atomic nucleus in various ‘shells or orbits’ (not the best description, chemists will know why, but good enough for here) to form atoms which are in turn used to build molecules. This electron binding (and subsequent interacting and releasing) is the basis for all chemistry. Electromagnetism manifests as both electric fields and magnetic fields. Both of these phenomena are simply different aspects of electromagnetism. A changing electric field generates a magnetic field and conversely a changing magnetic field generates an electric field.

What’s up next …..?

Strong nuclear force.
The strong nuclear force, sometimes called the strong interaction, is the force responsible for keeping the nucleus of an atom ‘stable’ for want of a better start point. It is present in two forms. The force that keeps the protons and neutrons bound together in an atomic nucleus and also the force that binds the quarks together to form these two nucleons and other hadrons. The strong nuclear force is about 100x stronger, at an atomic level, than electromagnetism.

Lastly ……

Weak nuclear force.
Weak nuclear force is very short ranged and its bosons (W & Z) primarily do not transmit or mediate a force. Their primary function is to transmutate particles. By exchanging a particle of weak nuclear force (the aforementioned W and Z bosons) electrons go to neutrinos, quarks mix types and a neutron changes into a proton emitting an electron in the process. This last interaction is called Beta Decay, a type of radiation, and is the most commonly used example of the weak nuclear force.
At extremely high energy levels, the weak nuclear force and electromagnetism begin to act the same, and this is called electroweak unification.

Confused ……? Yep, me too. Here are some real world examples that might help.

We have particles that make up matter (stuff like your laptop, the air you’re breathing, the chair you’re sitting on and you yourself) – the protons, neutrons and electrons.

We also have the particles that “cause” (in the loosest sense) forces to work – eg the “photons” of light coming from your screen, the “gluons” present in the nucleus of all matter that prevents its building blocks from flying apart at crazy speeds and the “W and Z bosons” without whose transforming power we would have no radioactivity.

Bang! – thats your bosons done!

More Soup (part 2) – The Hadrons

We have already looked at the leptons in part 1, so now we’re moving on to the hadrons. Please don’t forget that I’m keeping this purposefully simple and hopefully jargon-free(ish) to give the greatest degree of accessibility, to as wide an audience as possible.

A beginners guide to the Hadrons.

So ….what the hell is a hadron?
This a question many people ask but few find a satisfactorily simple answer to.
Simply put, a hadron is a composite subatomic particles made up of quarks and gluons. We’ll look at quarks in a little more detail further on in this post but for now we can just think of them as little building blocks. As for gluons, we’ll be looking at them in a future post (probably ‘More Soup – part 3’) but temporarily, just think of them as the force that binds the quarks together. This a somewhat simplistic view but suits our purposes for now.

Hadrons can be grouped into two main types. The mesons, that are made up of a quark and an antiquark, and the baryons, that are composed of three quarks.
To put this into a little bit of context lets use some examples. Some of the best and most commonly known baryons (a type of hadron) are the proton (p) and neutron (n) found in the atomic nuclei.

Both of these particles are stable when found in the nucleus. The neutron is unstable when outside of the nucleus (called a free neutron) and decays into a proton via the emission of an electron and an antineutrino.

The mesons, however, are a different kettle of fish!
Tending to be very short lived, with durations of 10-8 secs and shorter, the most common of the mesons are the Pion (pi-meson) and the Kaon (k-meson). There are many other varieties of meson, including the rho, B zero and eta-c meson but unlike the pion and kaon, these three, and most other mesons, are only detectable by the products of their decay.
What does this mean in real terms? Well ….. they are so short lived (10-23 secs in the case of eta-c) that the only way we can “see” them is to look for the ‘things’ they break down into when they decay into more stable products. It the case of eta-c (the charmed eta meson or ηc) the products could be a pair of photons or a trio of pions.

Pion decay in an early bubble chamber at CERN.

Like the leptons that we have looked at before, both the baryons and mesons have antiparticles that correspond to each positive particle. The proton (p) has an antiproton ( p ) and the positive pion (π+) has the negative pion (π) as an antiparticle. However, there are some mesons, such as the neutral pion (π0), that are there own antiparticle!
Quite unlike the leptons mentioned previously, all hadrons are affected by the strong interaction as well as the weak interaction, electromagnetism and gravitation. This is an important difference as it is this strong interaction that holds the nucleus together. Were it not so, why would the two protons in a helium nucleus stay together? The force of electrostatic repulsion would surely push them apart at a high velocity! We shall return to these binding forces in later posts.

So now we know what a hadron is, well …. we have a better idea anyway.
They are two or three of these little quark ‘building blocks’ stuck together. Great.
Quarks however …..erm ….. ok, off we go again.

Realistically, the quarks really deserve a whole “More Soup” post all to themselves, but what the hell, lets keep it simple and give you a quick guide now.

A quick guide to quarks.

As we’ve seen, these little guys are the very very simplest things that matter can be comprised of. They are held together in threes (baryons) or twos (mesons) and are a fundamental particle i.e. they’re not made of anything simpler – well thats what physicists currently think anyway.

Just like the leptons, they are categorised into six types or ‘flavours’, arranged into three generations.

In the first generation is the up (u) and down (d) quark. [both discovered SLAC 1968]
In the second generation are strange (s) and the charm (c) quark. [discovered SLAC 1968 and SLAC & Brookhaven 1974]
Lastly, in the third generation are the bottom (b) and top (t) quarks [discovered Fermilab 1977 and Fermilab 1995]
As before, each of these quarks has its own antiparticle – an antiquark e.g. the anti top quark (t) or the anti strange quark (s).
Note – All anti particles are designated with a little bar above the letter.

An example of some hadrons with their component quarks are listed below.
Proton (p) – up, up, down. (abbreviated to ‘uud’)
Neutron (n) – up, down, down. (udd)
Sigma minus (Σ) – down, down, strange (dds)
Charmed eta meson (ηc) – charm, anticharm (cc)
Pi minus meson (π) – down, antiup (du)

Before we leave this article, there are plenty of physicists out there who will be yelling about various qualities such as spin (isospin), parity (both C and G), strangeness, charm, charge, baryonic number and colour that can also apply to hadrons.
For you guys and gals – don’t worry. We’re taking this subatomic soup stuff a little at a time don’t forget. All those attributes will come up again later, in the future ‘More Soup (part 5) – Everything Else!’ post (probably).

More Soup (part 1) – The Leptons

Time for another post so I thought I’d go back to the particle physics.

Wow there’s a lot of subatomic particles.
The more I stir this quantum soup, the more I need to get to grips with my mesons, baryons, quarks, antineutrinos and lambda particles. Not forgetting, of course, the gluons, photons and bosons!
Ok …. so lets start explaining what’s what. I want to keep it really simple for now, so it’s as accessible as possible.
Most particles already get grouped together to form families, so I’m thinking some sort of list or glossary might be in order!

Evidence of neutrino interactions in a bubble chamber.

Let’s start with……..

A beginners guide to the Leptons.

Leptons are fundamental particles. By fundamental, we mean that they are composed of nothing smaller (by current thinking). They are divided into two main groups: the charged leptons (ie electrons) and the neutral leptons (ie. neutrinos).
These leptons are further classified into six distinct types, also known as flavours, occurring in what is known as three generations. Lots of sub atomic particles have favours and generations as we’ll see in subsequent posts but lets not worry about this now.

In the first generation is the electron (e) and the electron neutrino (Ve).

In the second generation are muon (μ) and the muon neutrino (Vμ).

Lastly, in the third and final generation are the tau (τ) and tau neutrino (Vτ)

This last lepton, the tau neutrino, was only discovered eleven years ago in 2000 at Fermilab in the US and indicates just how recently new discoveries are being made in the field of particle physics.

Each of these six fundamental particles also has a corresponding anti particle. Its exact opposite, if you like. An example of this would be an electron (e) and the corresponding antiparticle, an anti-electron , often called a positron (e+). They  differ from each other only in that some of their properties have equal magnitude but opposite sign.

All leptons have some intrinsic properties like mass, charge and spin (that’s quantum spin by the way). Unlike hadrons, they are not affected by the strong interaction, only by weak interaction, electromagnetism (except neutrinos which are electrically neutral) and gravitation.

Ok … so now we know what they are and how we classify them but ….. what exactly do they do and where can we find some ??
I guess most people know about electrons. Go back to some fairly standard secondary school science and we are told that they spin round the nucleus of an atom and are divided up into “energy shells”. Sort of like this —>

However that’s not really the case. We need to really think more along the line of an electron cloud – a little like an electron probability map. This diagram (left) shows what I mean. The purple spot in the centre representing the nucleus and the haze around the outside representing the probability of finding an electron in that location. The darker the haze the greater the chance that an electron could be found there.
Its all to do with quantum mechanics and a gentleman called Heisenberg. He came up with a principle – the aptly named Heisenberg Uncertainty Principle – that stated that you could not know a particles exact speed and position with 100% certainty. This is better stated as – the more precisely one of these qualities is known, the less precisely the other one can be determined.

But, again… I digress, so …. back to the leptons then.

Electrons (wherever they are!) control most of the chemical properties of the elements and govern how elements react with each other. They are very light weight, having a very small mass and are very stable.
Muons are heavier, with taus being the real heavyweights. Both muons and taus are very very unstable and short lived with lifespans ranging from 2.1×10-6 in the case of muons, to 2.9×10−13 for taus. Both muons and taus can only be created by high energy collisions such as those created by cosmic rays or in particle accelerators. Both particles break down readily, via particle decay, explaining their short lifespans. Muons decay into electrons and various neutrinos. Taus however, are much more complicated and are the only leptons that can decay to various hadrons as well as other leptons.

Faster than light neutrinos or “Einstein – give the guy a break!”

So ….. these faster than light neutrinos are still setting the science world ablaze. Does this really mean we have to consign the most recognisable scientific formula in world ever to the rubbish bin ???

Personally, I think not. Well …… not quite yet anyway.
Although there have been subsequent runs from CERN to Gran Sasso that certainly appear to verify the initial findings of a neutrino stream travelling faster than light, I still think its too early to to give categorical results.
Don’t get me wrong, history is filled with instances of scientific discovery that people at first scoffed at, strongly refuted and resolutely refused to believe, but in this case, the general consensus seems to be that the error margins are currently too high between the point of particle creation and detection to give totally conclusive results.

It will be interesting to see the results of Fermilab’s Minos Plus runs which are due to begin within the next six months to a year.

In the mean time, lets cut old Einstein a little slack. He has, after all, been one of the single most influential figures in the human understanding of the way the universe works.

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