The Assumption of the Blessed Virgin Mary is also defined dogma in the Catholic Church. No faithful Catholic can deny this event. The definition is found in MUNIFICENTISSIMUS DEUS (MD), and while that whole document is good, technically the only "infallible" part is the sentence which contains the definition of the Assumption, and that is:
by the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, we pronounce, declare, and define it to be a divinely revealed dogma:
that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory.
As you can see, in the definition - there is no mention of whether or not she died - only that she "completed the course of her earthly life." Thus you will find faithful Catholics who disagree on this particular point. In 2011 I wrote another article on this topic: Did Mary Die?
This is also an opportunity, yet another, for me to get on my soapbox about calling this particular season "Ordinary Time." There are SO MANY very EXTRA-ordinary feasts during this season, to refer to it as "ordinary" - by our modern use of the word, seems to downplay these HUGE feast days! The traditional reference to this season comes from the same root word - but makes it more clear - and that reference is "Ordinal Time" and "ordinal" means "counting." Along the same note, there are TWO "ordinal" seasons in the liturgical calendar where we "count days." The first ordinal season is the season after Epiphany which counts the Sundays after Epiphany up until the beginning of Lent. The second ordinal season is the season after Pentecost, where we count the Sundays from Pentecost to the end of the liturgical year which starts anew at Advent. In the modern lectionary these two seasons are combined - which, in my opinion, minimizes the importance of these season all the more.