As someone has just pointed out.....the hbar in the second formula of problem
4 should NOT be hbar**2 as I wrote earlier.....
A version of the problem set with various correction is now available below, including
the clarification of problem 2, which is really meant to ask the threshold energy for
copious production of charged kaons....not the threshold for production via some low-
cross-section Cabibbo-suppressed weak interaction.
The overheads from today's tutorial (with one correction) are
posted here .
Someone just pointed out that there is a mistatement in problem 1. The
charge and neutral currents can both cause the deuteron to dissociate,
but it's only the neutral current reaction that causes it to dissociate
into a proton and a neutron.
There are some other little glitches as well......somehow the first line
of text on page 2 went missing in the pdf conversion. It should read
"SNO detector (there can also be neutral current scattering from the protons).
The SNO detector is an enormous spherical vessel......"
Also, the hbar in front of the integral sign should be hbar**2
the first formula in problem 4.
I will extend the due date of the current assignment until Friday at 5PM.
For question 2 on the current problem set, you can assume the beam is of
negatively charged pions.
I have added a question to the current problem set. The version posted
below is now final, except perhaps for more introductory material for
question 1. I think, though, that everything you need is there. If I make
any changes I'll announce it here. But all the problems are now there.
A preliminary version of problem set #4 is now posted below.
For the current assignment I kind of botched parts a) and b) of question 2.
I have redone these, which amounted to combining the old a) and b) and making
a new part b). This is not so much additional work, but it allows me to make
the point that I had intended to make when I set the question.
As stated in tutorial yesterday, the assignments are now due in tutorial next
Thursday. I have to get them to the marker just after class, so they really are
due by 10AM this time, not later in the day.
The solutions to the first two problem sets are posted. If you spot any problems
or have any questions, please let me know. Especially for the first assignment
where the solutions may have some residual typos.
I've spoken with Professor Bailey about the problems some of you have on Monday.
It is impossible (i.e. against University rules) for me to alter the date of the
test. However, I will (at his request) report back to Professor Bailey about the
nature of the problem. He has indicated that he is willing to consider extending
the due date for the lab (though that decision has not been made). The only other
thing I can do for you is extend the due date for your current assignment, until
sometime next week....not before Wednesday....we can discuss the actual date tomorrow.
OK, the problems for the third assigment are now posted. As stated on the assignment there
will be numerous things that you need to look up for this assignment. You can find all of
them in the PDG, but you are welcome to use other references (but tell me what they are).
If you are having trouble finding things I will try to point you in the right direction.
I'm away in Geneva next week, but reachable by email. As usual, please let me know if there
are typos, or things that are unclear.
A number of people have asked about the problem set solutions. Sorry for the delay. I've
been typing them into computer rather than writing them by hand and it's taken longer than
I thought it would. I'm still working on them but I also need to finish the questions for
assignment #3,so I won't get the solutions up today and since I'm in Geneva next week they
probably won't be available until after the break, at which point I'll post the solutions
for the first two assignments. I might do this from Geneva if I can find a scanner there.
You all did fairly well on assignment 1, so hopefully the delay is not a problem.
Someone asked that I post the questions that we did in tutorial yesterday. You can
find them here .
Apologies. I meant to return your assignment #1 today in the tutorial. You are
welcome to pick them up from my office tomorrow. If you would just like to know
your grade, you can send me an email.
The additional information sheets (quark content of hadrons, Clebsch-Gordan coefficicents) has
been re-attached to the final version of the assignment. Sorry for leaving it off when I reposted
the final version. As announced in class today, I will extend the deadline for the assignments
until Friday at 5PM.
Some people came to ask me about the Lambda_0 and Sigma_0 states that we discussed
briefly in class yesterday (and which appear in various places on your current
assignment). They have the same quark content and the same spin-parity (1/2+). They
both have l=0 (no orbital angular momentum). The question is then, why are these
separate states with different masses. The answer lies in the baryon wavefunctions and
the fact that the u d and s quarks have different magnetic moments. If you are interested
in more explanation
see Perkins "Introduction to High-Energy Physics", second edition section 5.10 or
4th edition section 4.11 .... if you happen to come across only the third edition
then it's the section entitled "baryon magnetic moments". We might cover this
material after the break, but we also might not.
Someone pointed out to me that on slide 9 of the lecture on isospin (from 30/01/06)
the quark assignments to the charged and neutral kaons are incorrect. They are
reversed in each case, as is obvious from the charges of the quarks. I've corrected
the version posted on the website, but if you have printed versions you should make
the correction there yourself. I think the version that was posted was preliminary.
The updated one has one additional slide, with the isospin assignements of a variety
of particles (slide 10). The table contained the strangeness quantum number of various states as
well. Note that, by convention, a state containing one strange quark has S=-1, not S=+1.
Someone pointed out that my previous message about the signs of the electron in
a) and f) (below) was not reflected in the version of the assignment that was
posted. Sorry. I've corrected it. It's a positron in f) as I wrote in the earlier
As stated in tutorial today, the final version of assignment #2 is now linked below.
There is one additional problem and an additional component of question 1, asking
that you draw Feynman diagrams for allowed decays (only decays, not scattering
processes). Someone pointed out that the charge was missing from the electron in
processes a) and f). I have added this.....it is an electron in a) and a positron
in f), contrary to what I told the person who came to my office to point this out
to me. Sorry about that.....
Someone asked me on Monday about the definition of cross-section, since I have
asked a question on the problem set that makes reference to this, though we have
not yet really defined it. We will do so in the lecture tomorrow, for which I have
posted notes below. These are from Professor Orr's lectures and I will probably
use them unchanged tomorrow since they cover exactly the topic I want to discuss.
For those of you have asked about correpondence to the text, for the next few lectures
we are going to cover material that is presented in Chapters 5 and 6 as well as
Chapter 2 which discusses accelerators. The material that we have covered over the
last little while is dealt with in Chapter 7 (Symmetries and Conservation Laws),
8 (Angular Momentum and Isospin) and 9 (P, C, and T). It is well worth your while
to read these chapters in their entirety, thought there a few sections covering
material that we have not done in class. I will try to post a note on the the textbook
sections with the relevant lectures below from now on.
One of you handed in your assignment Wednesday afternoon, a day early. Could
that person please identify themself to me by sending me an email ? Thanks.
The bulk of the second problem set is now posted below, in case anyone wants to get
started on it over the weekend. There will probably be one additional problem in the
final version as well as some additional entries in problem 1. I may give you a hint
on problem 4 as well, though we may just discuss it in class if people are having
trouble getting started with it. If you spot any typos, please let me know.
Apologies, I forgot to post the numbers of diagrams yesterday, for questions 5 and 6
of the problem set. Here they are.
For problem 5:
a) 1 leading-order + 4 next-to-leading order (otherwise known as leading-order corrections)
b) 2 diagrams
c) 2 diagrams
For problem 6 a,b,c and d there are 2,2,3 and 2 diagrams, respectively.
The link to
the slides from yesterday's lecture still points to the preliminary version. I will
update this before the next class, and post the slides for Wednesday as well.
A preliminary version of the slides for todays class is posted below.
I'm still working on the lecture.....I'll update the link after class.
I have told a number of you that I will let you know how many digrams there
are for each part of the last two questions on the assignment. I will do this,
but not until Monday. I'd really like you to try to do the questions without
this information before I give it to you. I will post the information on
Monday after class.....I'll try to remember to tell you in class as well.
Please feel free to remind me.
A preliminary version of tomorrow's lecture is linked below. I will probably
work on it a little more this evening, but this should be good enough for
taking notes on tomorrow. If there are any changes I'll post the updated
version after class tomorrow.
There is a typo on the assignment, in question 2b) where the atomic number of
the initial gold isotope should be 197, not 179. Also a couple of people have
asked me about the branching ratio definition in the first question. For a
particle that can decay into N different final states, the branching ratio for
a particular final state is just the probability that a given decay will be into that
final state. This is not something which depends on time or the number of particles
that you start off with. Your answer should only involve the two decay constants.
We can discuss this more in the tutorial if anyone is still confused. We can also
talk about the last two questions. I might be convinced to tell you how many diagrams
there are in each case...
The overheads for today's class are now posted below. As advertised in a previous
announcement, we are diverging from the outline below. I apologize for not updating
it, I will try to do so later today. See the announcement from 18/01/06 for more
information on what we will do for the next little while. We will do conservation
laws and spin in the next couple of classes.
I haven't quite finished the lecture notes for tomorrow's class, but I will
have them posted before class, hopefully before noon tomorrow.
As I said to some of you, while I will not teach the course straight out
of the textbook, I do recommend that you do have some reference material
that you can read, rather than referring only to the notes. For instance
you might want to try to read about virtual particles somewhere (though
not, it seems in Frauenfelder and Henley, where this does not even appear
in the index. In any case, since this is our primary reference, I thought
I would at least advertise what section of the text correspond to the material
that we will cover in upcoming classes. I think we are going to slightly
diverge from the ordering of professor Orr's lectures. I would like to spend
the next couple of weeks filling out our discussion of the Standard Model,
which includes the discussion of symmetries and spin, as will as some discussion
on how hadrons are formed from quarks. Once we have done that we will return to
looking at scattering experiments and talk a little about accelerators and
detectors. So for the next few of weeks will be covering material that is
discussed in chapters 5, 7, 8 and 9 of the textbook. I encourage you to
read some of this in advance. You can also look at professor Orr's lecture
notes on (for example) "Angular Momentum and Spin", "Particle Classification
and Lepton Number", and Lectures 16-21.
I have posted your first assignment below. I posted a couple of versions with typos
earlier, so if you have seen it before reading this announcement please get a new version.
If I find other mistakes I will correct them and repost, with a new announcement.
If you find any problems, or things that are confusing, please let me know. If you
have questions you can come to see me, or send me an email.
For the tutorial tomorrow I suggest that we do the following. First, address any questions
arising from either of the lectures this week, particularly the Monday class which some
people said they had difficultly following. We can also address questions from today's class
but we will also do some excercises with Feynman diagrams that will hopefully clarify some
of the issues to discuss. Before we do that, we will quickly go over the last couple of
transparencies that I did not have time to cover today (I flashed one of them quickly, but
not the other). The problems for the first assignment will also be posted sometime tomorrow.
In an attempt to slow things to a more manageable pace, I will give most
of tomorrow's lecture on the blackboard. I will briefly discuss some of the
material in Professor Orr's (few) slides (on anti-particles) since it is relevant
for the following discussion. For those of you who attended the lectures last night,
by Professors Burgess and Smolin, the issue covered in Professor Orr's slides that
we will briefly review is the one discussed by Cliff Burgess in his talk, about
the conflict between Special Relativity and Quantum Mechanics that requires the
existence of anti-particles. We will then discuss Feynman diagrams for
the interactions that make up the Standard Model. I hope then that we can
make use of these for the rest of the course without any confusion. Of
course, we'll do some examples in class and in the tuorial and I'll put some on
your assignment so that we can make sure that you've understood. I will make a few
transparencies for the lecture, but they will largely be for reference. These slides
will be posted by sometime this evening at the latest. Note that these are NOT lecture
notes, just reference material. You don't necessarily need to read them in advance,
but it would be good to bring them along.
One of you commented today that the pace of the lecture was a little too fast
(and others were nodding their heads at this....). I will certainly try to slow
things down a little, but you should also feel free
to interrupt me to ask questions. Covering some of the material well is better
than covering all of it poorly. We can use the next lecture to try to renormalize
the speed, but that will only work if people pipe up in class to say that we are
going to fast (so that we come to some understanding of how much material we can
cover in one lecture).
Someone also asked about the tutorials, specifically whether I would be announcing
in advance what problems we would cover. As I said at the end of the
last tutorial (having forgotten to say it at the start) I think people in the class
should tell me what structure they would like for the tutorial. Certainly we can
go over lecture material that people have questions about (perhaps that is a good idea
this week). I can simply do problems on the board, if that is helpful, and I can try
to announce the problems in advance so that you have a chance to look at them first,
but I'm not sure I can promise to always manage this. For the first tutorial I did
one exercise that was a derivation of something I quoted in class. The next problem
was simple relativistic kinematics. The final problem was from one of the problem
sets and solutions that Professor Orr has posted on his website. As I said in class,
I encourage you to use his website as a resource. Try doing the problems that he has
assigned in past years. If you have questions about those we can try dealing with
them in the tutorial.
Overheads for today's lecture are now posted below. I apologize for the
quality, but they should be adequate for taking notes on.
The overheads from today's lecture are now posted below.
I've posted a pdf version of the first lecture. There are some problems with some
of the slides that used animations. I'll fix this and repost the slides. But I'll
leave what's there now until that gets done.
In response to the question asked in the first lecture about the implication
of the second law of thermodynamics on a possible eventual collapse of the
Universe, you can find a this question addressed
Any announcements made outside of class time will appear here. I will endeavour to
also post any announcements that are made verbally in class. However, I cannot promise
that this will always occur. It is YOUR responsibility to attend class or, if you do
not, to ensure that you are aware of what was discussed, including issues
not directly related to course material.