Jennifer Lopez enjoys a relaxed evening at Ben Affleck’s 52nd birthday

Jennifer Lopez has fun without Ben Affleck.

The Atlas The 55-year-old star stepped out to see performances by Bruno Mars and Lady Gaga and celebrate opening night at the Intuit Dome in Inglewood, California on Thursday, August 15, which would have been Affleck’s 52nd birthday.

Lopez was seen at the event wearing a casual outfit: a white tank top and a ponytail. She accessorized the outfit with large gold hoop earrings, a gold bracelet and a silver rhinestone necklace that read “Jennifer.” She can be seen laughing in photos while sitting and chatting with Ashton Kutcher.

She was also spotted hanging out backstage before the 38-year-old “Leave the Door Open” singer took the stage and was seen in high spirits in the venue’s VIP area during the show, which featured Bruno Mars and Lady Gaga singing their new duet “Die with a Smile” live.

The Air The 52-year-old actor was conspicuously absent from the event and was not seen with Lopez as she wandered around the new venue and chatted with friends.

Earlier in the evening, Lopez shared a photo of herself in full glamour on Instagram. In the photo, she appeared alone in a Dior dress with a sheer wrap design and a black belt around her waist that featured silver embellishments in a vertical pattern. She paired the look with a sleek ponytail and silver drop earrings.

This comes amid reports that there is tension in the couple’s marriage. Sources previously told PEOPLE in May that Lopez and Affleck’s marriage was “not in the best shape right now” and they were living separate lives.

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On August 6, a source told PEOPLE that Lopez and Affleck had not seen each other “in weeks.” The insider added, “They are moving on separately. Jennifer is trying to find a new home to start over.”

However marry me The actress stopped by Affleck’s rental home in Brentwood, California, on Sunday, August 11, while he was there for his birthday, a source said. She was also spotted accompanying his son Samuel, 12, to the mall that same day.

Lopez, who has 16-year-old twins Max and Emme with his ex-husband Marc Anthony, is keen to spend time with Affleck’s children Violet (18), Seraphina (15) and Samuel (whom he has with his ex-wife Jennifer Garner) before school starts.

“Just because she’s not with Ben doesn’t mean she doesn’t care about his kids,” the source said.

“They have always taken care of her,” the source continued. “Last year, she spent months looking for the perfect house for her blended family. Now that she’s back in LA, she wants to spend quality time with them before school starts again and Violet heads off to college.”

As for Affleck, an insider told PEOPLE earlier this month that he is “doing well” and “thrives when he’s busy, and he’s been working nonstop.”

“The kids are still off school. He’s spending a lot of time with them, too,” the insider said, adding, “It hasn’t been the easiest summer for him, either. He’s just trying to stay focused and make each day the best it can be.”