A beam of protons with speed $4 \times 10^5 \mathrm{~ms}^{-1}$ enters a uniform magnetic field of 0.3 T at an angle of $60^{\circ}$ to the magnetic field. The pitch of the resulting helical path of protons is close to (Mass of the proton $=1.67 \times 10^{-27} \mathrm{~kg}$, charge of the proton $= \left.1.69 \times 10^{-19} \mathrm{C}\right)$