What is the Quark structure, Baryon number, and antiparticle of a kaon, K+, which has a strangeness of 1.

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Firstly we must figure out what we know about this particle. We have its stangeness which is 1 and we know its charge from the "+" symbol in the question, which is also 1.

For the first bit we should write out all of the quarks we know, along with their relevent properties. These are:

The up quark with charge of +2/3 and a strangeness of 0.

The down quark with a charge of -2/3 and a strangeness of 0.

The Strange quark with a charge of -1/3 and a strangeness of -1.

For this question we also need to know that an antiparticle has the opposite charge and strangeness to its particle counterpart.

From this information we can see that clearly an anti strange quark must be in the Kaon. Then to make the charge up to 1, we must have an up quark. This is the quark structure. 

A particle made up of an anti quark and a quark is called a meson, and you should know that all mesons have a baryon number of 0.

The antiparticle of the positive Kaon is the K- meson. Its quark structure is an anti up and a strange quark.

When doing a question like this in an exam the most difficult part is determining the quark structure. I would recommend focusing on one known quantity such as charge, and determining how many ways of adding quarks will get you the required charge, then determine the other known quantity, such as baryon number or strangeness. There will only be one possible combination. This question requires you to recall quite a lot of information and so old fashioned book work is the key to scoring well.

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