Is there a way to eliminate white noise from my guitar head. (Gain channel)
It's pretty much even when the guitar is unplugged.
You should use a noise gate. My favorite is the ISP Pro Rack G Decimator stereo modded rack unit. You can also use the 2 complimentary pedals that they use as well. One will go before the amp, the other in the loop. I think the pedal setup is the decimator+ g-string set with the link cable.
Anyway, the gin channel on pretty much any head will be noisy. There is always noise in every electrical system, as the gain channel is massively amplifying the signal to distort it, it will also amplify the noise coming into the amp, and the noise as generated by electrical components. If it's a tube amp you will also have possible cycle hum from the AC power bleeding into the tubes as well as thermionic noise.
Any case, there are a few noise gates but i recommend the ISP stuff as it's a "fire and forget" type thing, you set it up once and it works nicely across gain and clean channels without readjusting, plus it will gate when you want it to, and provide feedback when you want to. Brilliant stuff.