All 6 entries tagged Physics

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July 09, 2007

First Week: ββ(0ν) Background

So its monday again, and i thought i should write an entry about what our first week has entailed!

Three words sum it up: Reading, Reading and Reading.
(plus a little scrounging, lugging, and reformatting!)

We arrived on monday to be given a large reading list, found the papers and got reading, this went on through tuesday too.

Wednesday involved more reading, and trying to locate computors and a room to put them in! Eventually the kind people in engineering were able to provide us with computors, and a physics meetingroom was booked for 8 weeks solid!

Ill post some pictures of our “office” when i get a chance.

The rest of the week was spent reading, and installing Linux on the three machines.

Friday afternoon saw me start a initial design for the website, which you can see in its rough form below:

website preview

Im going to have a meeting with my supervisor today to get links to all the data I need to include. Until then, adios!


Modelling the neutrinoless double beta–decay (ββ(0v))

Our (Andrew’s and mine) project involves the design and implementation of a Monte Carlo simulation of the ββ(0v) decay event, which should help in the search for the event. Tim has already outlined the basic theory of the decay, but not the implications of its observation.

If the ββ(0v) decay is observed then some assertions about neutrinos in the Standard Model (SM) of physics are incorrect. For example, the SM explains the observation of only left handed neutrinos by asserting that neutrinos propagate at the speed of light, and therefore are massless. However if the ββ(0v) is observed then it implies neutrinos have a finite mass, which is a big problem in the SM.

Neutrino physics has advanced rapidly and more theory suggests that this is the case, and the SM will need more and more augmentation if these theories are proved correct by observation.


July 04, 2007

My Project

Project Intro: Title: Development of an e-resource for Low Background Physics: ββ(0v)

My project is basicly to create a website where physicists researching into double beta decay can come to quickly and easily produce graphs showing background levels experienced in various experiments going on worldwide. To understand why this is needed, some basic theory is required:

Beta Decay

Beta Decay is the process in which a neutron decays, via the weak interaction to a proton, releasing an electron and an electron anti neutrino.

Beta Decay

In in normal beta decay two such events happen simultaneously, with the emission of two electrons and two antineutrinos. Neutrinos are assumed to be massless. This is as far as the “standard model” of particle physics can take us.

Double Beta 2v

Neutrinoless Double Beta

Certain theories beyond the standard model predict that neutrinos are actually Majorana particles (they are there own antiparticle) with non zero mass. In order to test these theories you can look at there prediction that Neutrinoless Double beta decay could occur, as shown below:

Neutrinoless

A virtual neutrino is exchanged between the two decaying nuclei, leaving only two electrons to be released. This is a testable prediction, as the two electrons must share the energy avaliable equally, and hence produce a sharp single peak on an energy distribution graph.

The reason this has not yet been conclusivly done arises because the half life of this process is very long! Around the order of ~10^25 years! This means even with a ton of source material only one or two of these event would happen within a year!

This is where my project comes in. If we are to spot the one or two events in a year, then the background noise must be very low. My project is to build a resource that will collate all the current experimental evidence around background noise, in a simple and easy to use format.


July 02, 2007

NMR Week 3

This week mainly involved reading about NMR theory (in particular about expected locations of spectral peaks). The aim of this reading was to help me to identify which spectral peaks derived from which bonds in the molecule. To enable this to be done in a logical manner I have started to number the different bonds of each molecule, noting which bonds appear in more than one sample (which should be able to be identified from the spectra also). One spectra was collected and I observed a double quantum spectra, which provides information on distances between atoms.

On Thursday Amy went away for a week so I am left to run some simulations. During Thursday and Friday I read up on the background material and theory required for me to properly understand the workings of the simulations and how all of the parameters correspond to a real situation. I know I started a little on this reading last week, but after three years of not having to read much I find that it’s quite a slow process! It certainly is a change from labs when you’re more or less given all of the information you will need.

Monkey

Thursday also meant Craft Day at WSAF during which I made a hat for the monkey that is perched over my desk:

I’ll take some proper science-related photos at some point.


June 23, 2007

NMR Week 2

Had a good second week (or second three days due to the Final Fling)! Ran another two guanosine spectra and felt a lot more confident with the use of the 300MHz spectrometer. One of our samples gave an abnormal spectrum initially, but after weighing it and noting that there was more of it than the previous samples the problem was proposed to be due to too much signal being given out. After decreasing the spectrometer gain and rerunning it, a better spectrum was obtained.

I practised using the Simpson simulation program for a good few hours by making notes on all of the parameters and then running and adapting example simulations to test whether I really knew what everything meant.

A comparison of two of the samples:
Spectral comparison of two samples (updated 05/07/07)


June 13, 2007

NMR: The first week

Day 1

The aim of my project is to use NMR to determine the structure of six synthetic guanosine-based compounds. My supervisor and the PhD student I’ll be working with gave me an outline of the tasks I will be doing..

So far I have helped to pack one of the samples into a Bruker 4mm rotor which is then placed into a probe which fits into a 300MHz spectrometer.

Using the spectrometer requires a lot of setup, for example the probe has to be tuned and the system and settings calibrated (by comparing the spectra of an alanine sample to one made previously). After going through it all, Amy and I set the sample to run overnight, using the NMR pulse sequence known as Cross Polarisation. I hadn’t come across this sequence before so it’s likely that there’ll be a fair bit of reading involved before I can be confident that I understand the procedures!

Day 2

We got results! The spectra was compared to the known spectra of guanosine so the extra peaks were identified as being those corresponding to the additional parts of the molecule. I learnt a bit about Double Quantum Coherence: a phenomenon which will be of great use in determining which atoms are adjacent to which in a molecule and their separation distances.

The second guanosine based sample was set to run overnight. I had a bigger part to play in the spectrometer set-up this time, which was quite a test of my 24 hour memory!

Day 3

Learnt more about Double Quantum Coherence and the pulse sequence that is used to exploit it. We set histidine (another amino acid) spinning in the spectrometer and saw results which matched known information.

Also managed to prepare a plan! A lot of it presumes we can get spectrometer time though.

Day 4

Drew lots of molecules using various software…was really fun! And they look so cool! Scoured databases to find molecules similar to the ones we are working on. When one was found we downloaded the structure and tried to see if the software used would allow us to add molecules in it to make our specimens. From there it will be possible to run computer simulations on it in order to obtain spectra without actually doing one experimentally.

Day 5

Observed and assisted with the use of the 600MHz spectrometer and then read the instruction manual to try and remember key points about its use. I find it really hard to remember things I’m told so making notes and rereading manuals is a must for me! Started learning how to use the simulation program too.


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