Today’s Halacha is Dedicated Leilui Nishmat Simha bat Esther z”l
Rabbi Ovadia Yosef (Teshuva in Yalkut Yosef, Hilchot Nefilat Apaim, § 23) and Rabbi Betzalel Stern (Shu”t Betzel HaHochma, vol. 3, § 14) write that on the day of a Hachnasat Sefer Torah (inaugurating a new Torah scroll), Tahanun is not recited, and this is the Moroccan custom as well. A new Sefer Torah imbues a day with immense joy and therefore the supplication prayers are suspended. Similarly, Rabbi Yehuda Ayash (Bet Yehuda, vol. 1, Yore De’a, § 23) writes that the “Sheheheyanu” blessing should be recited the first time a new Sefer Torah is taken out and read, and this was also the custom in Morocco.
Rabbi Haim Benvenisti (Sheyare Knesset HaGedola), Rabbi Haim Palagi (Kaf HaHaim) and Rabbi Davi Pardo (Michtam LeDavid) write that in several Sephardic lands, including Morocco, the sponsor of the new Torah scroll would host a feast in his home for seven days and this would culminate with escorting the scroll to the synagogue. Nowadays, such lavishness is less common and the sponsors tend to host a festive meal on the day of the Hachnasat Sefer Torahitself.
Summary: Tahanun is ommitted on the day of Hachnasat Sefer Torah. “Sheheheyanu” is recited the first time a new Sefer Torah is read.