No backup? Seriously why the hell not?
Your database is corrupt, it may be possible to get it back with some data loss, it may not. You need to 'hack' the database back into SQL Server.
Copy those files somewhere safe for the moment.
Create a new database with the same file structure (same number of files, same logical names) as the files for the DB you can't attach.
Stop SQL Server
Delete the files for the newly created database and put the files from that damaged database in their place.
Restart SQL Server. The database will probably come up suspect.
Once you're that far, post the error log entries and the output of querying sysdatabases for that DB. DO NOTHING ELSE AT THIS POINT.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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