Lottery spokeswoman Maura McCann wouldn’t reveal the winner’s name because the claims process is still underway.

She wouldn’t say whether the winner is a resident of the small town of Barrington, where the winning ticket was sold July 10 at George Calef Fine Foods.

Store owner Jim Calef says lottery officials are planning a party at the store Monday to publicly introduce the winner of the July 13 drawing, announcing it amid banners, balloons and flowers.

He or she will be able to choose between a lump sum of $750,000 after taxes or the full $1.5 million in annual payments over 30 years.

Calef says he will share with his 11 employees the 1 percent bonus the store gets for selling the winning ticket.

“We all sell the tickets,” Calef said. “It’s just luck one of us sold it.”

Calef said he was driving around town running errands when the news broke that the winning ticket was sold at his store. He got the news from friends and patrons who congratulated him.

“I still don’t really believe all this yet,” Calef said.

Calef said Tuesday he knows the winner went to lottery headquarters in Concord late Monday to claim the jackpot, but said he does not know who it is.

Calef said his family’s store, which has been in business 30 years, has sold plenty of winning lottery tickets but never one that exceeded the $600 threshold that requires winners to claim their prizes in Concord.

The Tri-State Megabucks Plus jackpot had grown steadily since the last winning ticket was sold in Vermont in early June.

The last New Hampshire jackpot winner was a Windham woman in October of 2010. She bought her winning ticket in Londonderry.

Tri-State Megabucks is also played in Maine.