# 6805: 1094 Activities 1

Write your name and answers on this sheet and hand it in at the end.

There are a variety of activities today and you may not have time to get through them all. Work with others at your table on these activities. Argue about the answers but work efficiently!

## Using Piazza

Goal: get some practice using Piazza.

1. Go to the Piazza page and log in (you can get there directly or from the 6850 home page).
2. Note the preferences in the menu at the upper right. You may want to adjust the Account/Email settings (e.g., "Edit Email Notification").
3. Go to the Q&A section. Look at some examples (click on questions). Try searching for "QCD".
4. Start a New Post. Choose "other" as the folder if there isn't an appropriate one. Enter this text using LaTeX:
Einstein showed that E = γmc2
Preview it (but don't post) Did you succeed?
Try adding $$\gamma \equiv \frac{1}{\sqrt{1-(v/c)^2}}$$ and previewing. Cancel (don't submit).
5. Create and submit (for real) at least one new question, answer, or comment. Did you succeed?

## arXiv and inSPIRE look-up

Goal: to be able to look up nuclear physics papers based on the author(s).

1. Go to arxiv.org and find the papers for today ("new") in Nuclear Theory (nucl-th) and pick one that looks interesting. Get a pdf version. Put the title of the paper here:

2. Go to inspirehep.net and look up Prof. J. Shigemitsu's papers. Find her most cited paper (use "- or rank by -" pulldown and "Search" again). What do you think it is about? (speculate!)

## Looking up properties of isotopes and particles

Goal: Do some warm-ups that we'll need for future activities.

1. Go to the Interactive Table of Nuclides (under "Online references"). Find the oxygen isotopes. (Note that you can zoom and then move around with the blue arrows.) Which isotope has the least neutrons? Which has the most neutrons? What is the isotope you are mostly breathing (most abundant)?

(Later we'll see it is recently possible to calculate properties of all these nuclides!)
2. Go to the Particle Data Group site and then the Summary tables for mesons and baryons. How do you characterize what is a meson and what is a baryon?

3. In the meson table, find the mass and lifetime of the charged pi mesons (pion) and give them here. What are the units of "mass"?

4. In the baryon table, find the masses and lifetimes of the proton and neutron and give them here. How long does the neutron live in minutes?

## Diffraction and elastic scattering from nuclei

Goal: deduce the sizes of nuclei from elastic scattering of various beams of particles.

1. From the "in class" links, go to "elastic scattering from nuclei" and look at the pictures. The plotted "differential cross section" is proportional to the intensity (number of counts) at that angle. Questions?

2. In what ways do these graphs look like the diffraction patterns for light through slits or holes? (E.g., pattern as function of angle, spacing of minima.)

3. Let's start with 208Pb in the right figure of proton scattering. The energy is 0.8 GeV, which is the kinetic energy of the proton. With c=1, find the momentum in MeV:

4. Use the de Broglie relation and the "hbar-c = 200 MeV-fm" conversion factor to find the wavelength of the particles in fm (femtometers):

5. Use an appropriate formula to relate the first minima to the diameter of the nucleus. What do you get? (show your work here)

6. As time permits, do the negative-charged pion and then the electron for 208Pb. Are the answers consistent?

6805: 1094 Activities 1. Last modified: .
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