My Study Chat Group is Full of Real Big Shots

Chapter 362: Chapter 296: Salute to the Backbone of a Great Nation

Halfway through the meal.

Zhang Wenping signaled for Li Dong to go outside with him.

Outside the private room was a small corridor, and at its end was a small tea room.

Zhang Wenping pushed the door open, went in, and pulled it shut behind him.

”Li Dong.”

”The main reason I called you out is that there’s something I want to discuss with you.”

Li Dong raised an eyebrow, a little confused.

”Teacher Zhang, please, go ahead.”

Zhang Wenping smiled.

”That man at the table just now, Shen Che, you remember him, right?”

Li Dong nodded.

Only then did Zhang Wenping continue.

”Old Shen and his team have been working on something big lately.”

”Actually, it’s not just them.”

”It’s led by the Jinling University School of Physics and the Zijin Mountain Observatory, in a joint effort with the Chinese Academy of Sciences High Energy Physics Institute and the Shanghai Microsystem Institute.”

”It’s a preliminary research project called the ’Next-Generation High-Energy Cosmic Ray and Dark Matter Indirect Detection Space Payload.’”

”It’s a mouthful, I know.”

”But to put it in layman’s terms...”

”We’re going to build the next generation of satellite payloads based on the Wukong Satellite.”

”We’re extending the detection energy range at both ends—a bit lower and a bit higher.”

”On the high-energy end, we need to be able to measure PeV-level electrons and gamma rays.”

As Li Dong listened, his eyebrows twitched slightly.

’Heh, I actually know about this. And I knew about it even before I joined the Cyan Dragon Study Group.’

Physics was his favorite subject, so he had read a lot of popular science books. Even though they didn’t go into great depth, he definitely remembered this.

Zhang Wenping continued.

”We don’t have to worry about the hardware side.”

”Detectors, calorimeters, trackers—Old Shen and his group are the experts on all that.”

”They and the Zijin Mountain Observatory have already revised the engineering proposal to its sixth version.”

”But they’ve hit a snag.”

”And where’s the snag?”

”It’s the data.”

”To be more specific, they’re stuck on the energy spectrum unfolding.”

Li Dong now understood the meaning behind Shen Che’s knowing smile. They were here to press-gang him into service.

While he hadn’t personally worked in space astrophysics, when it came to unfolding, he was indeed an expert.

To use a crude analogy for unfolding...

A satellite orbits in space, and high-energy particles that have traveled from the deep, distant universe arrive packed with energy.

But the satellite can’t measure this energy directly.

It can only measure the footprints the particle leaves behind, layer by layer, as it hits the silicon microstrips, the scintillators, and the BGO crystals of the calorimeter.

And these footprints never reflect the particle’s original energy.

A particle’s original signal is like a smooth, flat sheet of white paper.

But when it crashes into the detector, it first gets brutally mangled by the underlying electronics system.

Then, it gets mangled a second time by the complex trigger logic.

Finally, when you factor in the blind spots of geometric acceptance, errors in energy resolution, and the inevitable energy leakage... that’s like mangling the paper a third and fourth time.

By the time this string of data is transmitted back to the servers on the ground, it has long since become a crumpled-up ball of waste paper.

So, what everyone has to do is take that ball of waste paper, look at every single physical crease, and use mathematical methods to painstakingly iron it flat, forcing it to return to its original state as a clean white sheet.

This is called unfolding.

Just then, Zhang Wenping spoke up.

”This is where the difficulty lies.”

”With the current generation Wukong Satellite, the statistical data is already quite sparse by the time it reaches the TeV energy range.”

”The next generation needs to reach even higher, to the PeV scale, where the data will be even thinner.”

Li Dong nodded.

He understood. ’In reality, there were words written on that white paper.’

’You’re taking a piece of paper that’s been practically pulped and trying to reconstruct the original manuscript, which only had a few words on it to begin with.’

’In the resulting energy spectrum, once you pass a certain energy threshold, you can’t confidently say that any new spike that pops up is real.’

This phenomenon has a particularly vivid name within the field.

”Illusion Peak.”

When the data becomes sparse enough, the unfolding operator starts to ”run a fever” on the high-energy tail of the spectrum. As the fever rages, it starts producing all sorts of hallucinations.

For the indirect detection of dark matter, this is fatal.

Whether it’s from annihilation or decay, the characteristic signature left by dark matter particles is just a very faint step or bump hidden in the energy spectrum.

Meanwhile, your unfolding method is running a fever and seeing Illusion Peaks everywhere.

You get a spike one day and say, ”Look, dark matter has arrived!”

But the first thing the international experts will ask you is...

”Buddy, isn’t that just an Illusion Peak your algorithm spit out on the high-energy arm?”

How do you argue against that?

Zhang Wenping continued.

”The members of Old Shen’s group have spent the last five or six years wrestling with unfolding, and they’ve gone through several generations of frameworks.”

”Before, they were mainly using a combination of Bayes’ method and the standard Tikhonov regularization.”

”How should I put it... It could barely handle the low-energy range, but once you got to the high-energy range, the old method became completely inaccurate.”

”At their last group meeting, Old Shen was so frustrated he was slamming his hand on the table.”

Zhang Wenping chuckled.

”He said that if the data from the next-generation payload doesn’t have a much tougher yardstick set up beforehand—one that can slice away the Illusion Peaks on the high-energy arm—then the project will be dead in the water from the start.”

At that moment, Li Dong understood completely.

’A tougher yardstick, huh?’

’The Li Criterion.’

Seeing the expression on his face, Zhang Wenping knew the kid had already figured it out.

”So, Old Shen asked me to come and sound you out.”