What is going to happen since an "anonymous" person called Arkansas APS and said that my daughter is physicaly abusing me?

They will visit and interview both of you. Be honest. If mom has delusions or other let them know and be sure to refer them over to physician. Request a copy of the final report and assessment. Make sure u get for your records. If there is anything disputable or needle ping clarified--do so in writing and make sure they acknowledge receipt.

I'm sure this is a routine investigation for them.

Don't get defensive or indignant. You both want what is best for mom so acknowledge that.