False statements (defamation) used in disciplinary action

I work for a higher education institution. There were a couple coworkers that were upset with me over a schedule situation. They made false accusations against me in a situation that, in turn, caused disciplinary action and possible termination to be put on the table. I have never received any type of disciplinary action in all the years I have been with the organization. They will not tell me who said what and say they are protected, yet my character and integrity are on the line and I have been disciplined due to these outright false accusations. I have other witnesses that are willing to tell the truth, but they have not talked with them. What can I do? This has greatly impacted my character, reputation, and integrity. It caused an unjustified disciplinary action. What can I do? What recourse do I have over this direct defamation, especially when the institution will not give names of those who said these things. ??