Anti-matter ion cosmic rays : An international consortium is presently building

Question

Anti-matter ion cosmic rays :

An international consortium is presently building a device to look for anti-matter nuclei in cosmic rays to

help us decide if there are galaxies made of anti-matter. Anti-matter is just like ordinary matter except the

basic particles (anti-protons and anti-electrons) have opposite charge from ordinary matter counterparts.

(Anti-protons are negative, and anti-electrons are positive.)

A schematic of the device is shown at the right. A cosmic ray -- say a carbon nucleus or an anti-carbon

nucleus -- enters the device at the left where its position is measured. It then passes through a (reasonably

uniform) magnetic field. Its path is bent in one direction if its charge is positive, in the opposite direction if

its charge is negative. Its deflection is measured as it goes out of the device.

a. On the figure shown, does the B field point into or out of the page?

How do you know?

b. Describe the path followed by each particle in the device (is it circular, parabolic, etc).

Why?

c. If you were given the magnetic field, B, the size of the device, D, the amount of charge

on the incoming particle, q, and the mass of the incoming particle, M, would this be

enough to calculate the displacement of the charge, d? If so, describe briefly how you

would do it (but don't do it). If not, explain what additional information you would need

(but don't estimate it).

http://www.physics.umd.edu/perg/abp/TPProbs/Problems/MG/MG04.htm

An international consortium is presently building a device to look for anti-matter nuclei in cosmic rays to help us decide if there are galaxies made of anti-matter. Anti-matter is just like ordinary matter except the basic particles (anti-protons and anti-electrons) have opposite charge from ordinary matter counterparts. (Anti-protons are negative, and anti-electrons are positive.) A schematic of the device is shown at the right. A cosmic ray -- say a carbon nucleus or an anti-carbon nucleus -- enters the device at the left where its position is measured. It then passes through a (reasonably uniform) magnetic field. Its path is bent in one direction if its charge is positive, in the opposite direction if its charge is negative. Its deflection is measured as it goes out of the device. On the figure shown, does the B field point into or out of the page? How do you know? Describe the path followed by each particle in the device (is it circular, parabolic, etc). Why? If you were given the magnetic field, B, the size of the device, D, the amount of charge on the incoming particle, q, and the mass of the incoming particle, M, would this be enough to calculate the displacement of the charge, d? If so, describe briefly how you would do it (but don't do it). If not, explain what additional information you would need

Explanation / Answer

a) out of the page, by right hand rule

b) circular

c) yes since the particle will move in a cricle with radius mv^2/r = q v B
so r = m v/(qB)

then you can use that both points are on a circle to find d

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