As I understand the documentation for besseli (link), the ‘nu’ argument is 0, corresponding to the notation in your image. So the ‘Z’ argument becomes the quantity in the second set of square brackets.
Then code the other expressions and multiply and divide them appropriately, using element-wise operators for multiplication (.*), division (./) and exponentiation (.^).
After that, it works the same way as the code in How do you write this equation correctly in MATLAB? (link) to limit the expression to (sigma>0), and with the same logic.
