Science & Technology

“Search for lifetime” of supersymmetric particles at CERN

University of Chicago Researchers look for suggested particles that can explain the habits of the universe.

A team of researchers at the University of Chicago recently set out to search for lifetimes, the lifetimes of long-lived supersymmetric particles.

Supersymmetry is a theory proposed to extend the Standard Model of particle physics. Like the Periodic Table of the Elements, the Standard Model is the best description we have of subatomic particles in nature and the forces acting on them.

However, physicists know that this model is incomplete. For example, there is no room for gravity or dark matter. Supersymmetry aims to complete the big picture by combining each Standard Model particle with a supersymmetric partner to open a new class of virtual particles for detection and New research, UChicago physicists have clarified restrictions on what properties these superpartners can have in the presence of them.

“Supersymmetry is the most promising theory we have to solve as many problems as possible with the Standard Model,” said the University of Tennessee, Knoxville, where he worked as a postdoctoral fellow at the University of Chicago. Associate Professor Tova Holmes said. “Our work fits in with the greater effort to rethink new ways of exploring physics with the Large Hadron Collider.”

Resha Chulainn

Inside the ATLAS detector is Lesya Horyn, a researcher at UChicago. He recently completed a treatise on the search for long-lived sleptons, existing electronic, muon, and tau lepton supersymmetric partners.Credit: University of Chicago

Large Hadron Collider in Europe CERN, Accelerate the protons to almost the speed of light before forcing them to collide. These proton-proton collisions produce many additional particles that researchers want to find new physics.

“But with the Large Hadron Collider, it is very rare and difficult to identify new physical events with colliding particle debris,” said UChicago, physics chair and co-author of the study. One Young-Kee Kim professor said. Completely led by a woman.

The UChicago team used data collected by CERN’s particle detector, ATLAS, to search for the generation of sleptons, the hypothetical superpartners of existing electrons, muons, and taurepton. In the tested supersymmetry model, sleptons are theorized to have a long lifespan. This means that you can move much more before it collapses into something that ATLAS can detect.

Toba Homes

Tova Holmes, an ATLAS count room physicist, has a lot of data collection and triggering infrastructure. At some point in the next decade, these systems will be upgraded to improve the next generation of supersymmetric searches.Credit: University of Chicago

“One of the ways we can miss new physics is if the particles don’t collapse immediately when they are created,” Holmes said. “Usually, the search doesn’t recognize long-lived particles because it cuts out anything that doesn’t look like standard prompt attenuation for the detector.”

Sleptons are expected to eventually collapse into regular slepton partners. However, unlike traditional collapses, these leptons are displaced. That is, it never returns to the original proton-proton collision point. It was this unique feature that physicists were looking for.

However, in the four years of ATLAS data collected, UChicago researchers did not find a replaced lepton event. Due to their lack of discovery, they were able to set so-called limits, excluding the range of mass and lifetime that long-lived Sfermion could have.

“If sleptons are present in this model, we are at least 95% confident that there is no mass and lifetime in the shaded areas. Of this plot“Resya Horyn, who recently received a PhD from UChicago, who completed a treatise on this measurement, said.

Will the null result disappoint the team? You are welcome.

“Finding nothing tells you a lot,” Chulainn said. Knowing that long-lived sfermions do not have a specific mass and lifetime allows researchers to know where to focus their future searches.

“Supersymmetry is the most promising theory we have to solve as many problems as possible with the Standard Model.”

— — Tova Holmes, Associate Professor, University of Tennessee, Knoxville

“From my point of view, this search was the first thing the theorists called for coverage,” Holmes said. “We seemed to be able to do it — and we did!”

As a result, the team was able to push the boundaries even further. At some point in the next decade, the Large Hadron Collider will go into a regular shutdown, leaving enough time to upgrade the ATLAS hardware.

“This was the first path in the analysis, so there’s definitely a place to improve,” Horyn said.

One of the imminent upgrades is an improvement in the trigger system that allows you to choose whether to save or discard the event. Triggers are now optimized to preserve decay from short-lived particles rather than the long-lived sleptons that are central to this supersymmetric search.

You can make quicker improvements without having to wait for a shutdown.

“Future steps could include searching for the same model using more robust data from the next run of the Large Hadron Collider,” he said as an undergraduate student at UChicago. But Harvard graduate student Xiaohe Jia said. Another route to explore could be to extend long-lived particle search as well as sleptons using similar techniques, she said.

For now, the completion of the Standard Model remains a mystery, but the team is proud to have led the first search for this supersymmetric model at ATLAS.

“Discovering new physics is like finding a needle in a haystack,” Kim said. “I didn’t see anything in the current data, but there are great opportunities in the future!”

See also: “Searching for Displacement Lepton in √s = 13 TeV pp Collision with ATLAS Detector”, ATLAS Collaboration, October 6, 2020, ATLAS CONF Note.

Funding: National Science Foundation.

“Search for lifetime” of supersymmetric particles at CERN “Search for lifetime” of supersymmetric particles at CERN

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