Texans are celebrating the decision to build the world's largest atom smasher in their state, but funding for the $4.4 billion project may be jeopardized already because leaders of other states are complaining of political favoritism.

Sen. Dennis DeConcini, D-Ariz., and other disgruntled lawmakers fired off a letter to President Reagan after the Energy Department decision was announced Thursday voicing concern about the "widespread perception that this decision was not based on scientific valuation (but) on political and other factors."House Republican leader Robert Michel of Illinois called on Reagan to "insist on a re-evaluation" of the choice, and Illinois Gov. James Thompson said even he would protest to the president despite his alliance with the administration through his national co-chairmanship of Vice President George Bush's campaign.

What irks those in states that lost the competition for the superconducting supercollider - Arizona, Colorado, Illinois, Michigan, North Carolina and Tennessee also were finalists for the economic prize - is that the Texas selection came just two days after Texas Republican Bush won the White House.

Moreover, pointed out Rep. Dennis Hastert, R-Ill., "Texas does have the speaker of the House," Democrat Jim Wright, "who has the votes and the clout when he wants something done."

"The other piece was put into place the other day," added Hastert, whose congressional district would have been home to the project had Illinois been selected. He was referring to the re-election of Texas Sen. Lloyd Bentsen, the unsuccessful Democratic vice presidential nominee who will return as chairman ofthe powerful Senate Finance Committee.

Energy Secretary John Herrington denied his decision was tainted and noted it is up to Reagan to designate the site formally before leaving office Jan. 20.

"I have to tell you there are no politics in this," Herrington told a packed news conference. "We were faced with picking the best of the best."

He defended the site around Waxahachie, Texas, as the one that showed "the highest overall technical evaluation ratings of any proposal and exhibited no significant overall weaknesses. No other proposal received outstanding ratings on geology and tunneling, regional resources, environment and setting."

Herrington said his department's political appointees were not told of the choice until Tuesday and Reagan and Bush were not informed until 9 a.m. EST Thursday _ about the same time governors were told the result.

Herrington also noted the site announcement purposely was delayed until after the election to eliminate any possible charges that the choice was designed to curry favor with a politically important state.

The collider is envisioned as an a oval underground ring of supermagnets 53 miles in circumference in a tunnel 10 feet in diameter. It would cover 16,000 acres of rolling prairie near Waxahachie, about 30 miles south of Dallas.

Beams of protons could race around the tunnel in opposite directions at nearly the speed of light, with the payoff coming when the beams collide, releasing a shower of subatomic particles that scientists could study to decipher more about the nature of matter and energy.

Supporters say the research likely would produce breakthroughs in medicine, transportation, communications and military technology. The collider would be 20 times more powerful than the largest existing particle accelerator at Fermi National Accelerator Laboratory in Batavia, Ill., west of Chicago.

While under construction, the $4.4 billion collider is expected to employ several thousand workers, and when finished in the mid-1990s it would employ 2,500 scientists and technicians with an annual budget of $270 million.

Herrington's announcement was attended by a contingent of jubilant Texas officials, including Wright, Bentsen and Republican Sen. Phil Gramm.

"We did it!" Texas Gov. Bill Clements exulted after taking an early morning telephone call in Austin from Herrington. "It's a great day for Texas. It means jobs, jobs, jobs. I couldn't be more pleased. Texas is the best site and there's no question about that."