While creating Search Service application getting the error

While creating search service application I got the below error. please give the solution

Errors were encountered during the configuration of the Search Service Application.
System.Data.SqlClient.SqlException: Windows NT user or group 'RW\administrator' not found. Check the name again. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) at System.Data.SqlClient.SqlCommand.ExecuteNonQuery() at Microsoft.Office.Server.Data.SqlSession.ExecuteNonQuery(SqlCommand command) at Microsoft.Office.Server.Data.SqlServerManager.GrantLogin(String user) at Microsoft.Office.Server.Search.Administration.SearchDatabase.GrantAccess(String username, String role) at Microsoft.Office.Server.Search.Administration.SearchDatabase.SynchronizeAccessRules(SearchServiceApplication searchApp) at Microsoft.Office.Server.Search.Administration.SearchServiceApplication.SynchronizeDatabases() at Microsoft.Office.Server.Search.Administration.SearchServiceApplication.Provision() at Microsoft.Office.Server.Search.Administration.SearchConfigWizard.b__22() at Microsoft.Office.Server.Search.Administration.SearchAdminUtils.UpdateIgnoreSPUpdatedConcurrencyException(String description, SearchAdminUtilsUpdateDelegate updateDelegate, SearchAdminUtilsRefreshObjectDelegate refreshObjectDelegate) at Microsoft.Office.Server.Search.Administration.SearchConfigWizard.CreateSearchApp() at Microsoft.Office.Server.Search.Administration.SearchConfigWizard.ProvisionSearchServiceApplication() at Microsoft.Office.Server.Search.Administration.SearchConfigurationJobDefinition.ExecuteTimerJob()