Physicists Struggle to Unite Around Future Plans

Nearly 800 particle physicists descended on the University of Washington to share their scientific dreams and nightmares in person. They tried to build a unified vision of their field for 10 days at the end of July.

The Standard Model of particle physics describes quarks bound tight by gluons to make atomic nuclei, negatively charged electrons and their heavier counterparts, muons and taus, and the particles of light. The Standard Model divides the particles into fermions and building blocks of matter. Experiments of increasing complexity and size have been needed to search at the smallest of scales. Physicists sift through haystacks of data to find new particles. More than 5,000 scientists analyzed petabytes of data from detectors weighing thousands of tons at the biggest machine in the world in 2012 in order to discover the existence of the new particle.

The triumph of the Higgs discovery has been overshadowed by fears that particle physicists are stuck in a nightmare scenario with no clear path forward. The Standard Model should be bigger to account for phenomena such as dark matter and gravity, according to physicists. The searches for these new particles have come up empty so it is a nightmare for physicists.

At the conference, a panel discussion simply entitled "Where Are We Going?" faced the question head-on. The lack of new particles was argued to be a success by a theorist at the University of Pittsburgh. He said that the nightmare scenario was not a failure. Panelists insisted that particle physics was not in a nightmare scenario at all or that the nightmare was here but short-lived.

There is some intentional disgruntlement. Roughly once a decade, hundreds of particle physicists take part in the Snowmass process to decide what to ask nature and which tools they need for answers. Evaluating the true nature of dark matter and dark energy was one of the high priority tasks identified by the preceding in Snowmass.

The field has shifted for the better, despite the fact that the puzzles are not solved. Experiments can cut through noise and find signals that were thought to be out of reach. Next- generation facilities such as a muon collider have made a difference. The search for dark matter has grown to encompass a wide range of possibilities, once limited to a small number of candidate particles and types of detectors.

A popular fantasy of science is that the puzzles will be solved by a single thinker in a lab or on a chalkboard. The work of a career scientist isn't always different from the work of a politician or business person. Hitoshi Murayama, a theorist at the University of California, Berkeley, gave a talk at the beginning of the conference that emphasized the need for particle physicists to do more than argue for their own projects. He said that they needed to make a case for the whole field.

Getting particle physicists to agree on a vision is not easy. Dark matter experts believe that their search is more important than the work of researchers in the neutrino field. Particle physicists know that the debates are an important part of the process. On the first day of the new Snowmass, a Department of Energy representative warned thatickering scientists would get nothing.

Getting to know the program.

The U.S. particle physics is funded by the National Science Foundation and the Department of Energy.

The Deep Underground Neutrino Experiment is under construction and draws the lion's share of funds. 30 percent of researchers working on the experiments at the European project are from the U.S. DUNE has 1,400 people collaborating. The community at Snowmass was reminded by Lia Merminga that particle physics is global.

The one that was canceled looms large. The Superconducting Supercollider was scrapped by Congress in 1993 after 2 billion dollars had been spent. It was supposed to be the most powerful particle accelerator in the world. It was a big blow for particle physics around the world but it was also a big blow for American physics. Suddenly, researchers based in the U.S. found themselves without a collider. Many simply left the field and moved to other projects.

The price of DUNE has ballooned from $1.8 billion to $3.1 billion, causing some to worry that it could go the way of theSSC. One of the main goals of DUNE is to find out how much nature prefers producing neutrinos over antimatter twins. A Japanese neutrino detector called Hyper-Kamiokande is scheduled to begin operations in the near future. Critics wanted to know if DUNE would be redundant. If Hyper-K gets an upgrade costing an additional $900 million, supporters said DUNE has better sensitivity to the violation.

Merminga received applause when she said that DUNE had cleared the DOE reviews. Scientists uneasy about DUNE's scientific goals want it to succeed because it would hurt the whole community. One researcher said, "If DUNE's dead, we're dead."

Over the past 10 years, funding for the entire field has dwindled. With U.S. industrial policy on the rise, some physicists are hopeful they will get a piece of the pie. The CHIPS and Science Act signed into law by President Joe Biden includes provisions to boost quantum technology, which is key to some new dark matter experiments, as well as more funding for machine learning.

Daniel Whiteson is an experimental particle physicist at the University of California, Irvine. The idea of a data physicist was raised by him and others. David Shih is a theorist at Rutgers University. During his remote presentation, he said, "Here's a crazy idea." We could use a generative model. Powerful models can produce compelling images or write prose, just as physicists can produce collision explorable. The idea set off both laughter and concern.

About two thirds of particle physicists who spend years working toward a PhD are forced to leave their positions because of the lack of new funds. Thepipeline is rich with people who want to be researchers, but don't have the right positions to hold.

In order to reduce the stigma of leaving particle physics, the conveners of Snowmass held a mixer where more than a dozen former physicists now work. For early-career researchers looking for a job to actually do physics, the chances were not very good.

The majority of physics PhDs awarded in the last four years have gone to white men. Some people can't agree on how to address diversity. Bryan Ramson, a research scientist at the Fermilab, told Scientific American that the younger generation isn't interested in the debate about the trade-off between excellence and diversity. If everyone is good enough, physics would be better off.

There are dreams and nightmares.

The dream of particle physicists is to double their particulate pantheon so that each boson has a fermion counterpart and each fermion has a boson twin. Supersymmetry is a set of theories that have shaped generations of researchers. Under SUSY's rules, the photon would be mirrored by selectrons. The symmetry between force-carrying bosons and fermionic particles of matter could act as dark matter if the Standard Model is correct.

The most likely places where the particles could have been hidden have been ruled out by the experiments. SUSY is proud of its place among theories. Many particle physicists, particularly those of an older vintage, still speak of it in the present tense.

Even though SUSY is not dead, many younger researchers are moving on. They are looking for dark matter wherever they can find it, not just for the weakly interacting massive particles predicted by SUSY. The baby is not being thrown out with the bathwater. The principle of naturalness should be salvaged regardless of SUSY, according to Nathaniel Craig, a theorist at the University of California, Santa Barbara.

Naturalness is the idea that the universe isn't really lucky. Craig said that if a pencil could be balanced on its tip, it would be easy to use. Should we expect the universe to be lucky or should we look for something hidden?

Naturalness stems from the theoretical physicist Victor Weisskopf's 1939 work showing how the positron stabilizing the electron, and in 1974 Ben Lee and Mary Gaillard predicted the charm. Craig said that naturalness is a strategy to help us focus in the infinite places. Physicists should consider more than one theory inspired by naturalness because of SUSY.

Theorists aren't the only people leaving SUSY. Experiments using giant containers of liquid xenon to spot dark matter set impressive new limits on the possibilities of WIMPs. The results were only a small part of the discussion. Researchers no longer need to fulfill SUSY, which predicts dark matter in a relatively narrow mass range, and are now looking for dark matter particles with different mass ranges. They are trying to find a way to get into theneutrino floor, the level at which noise from cosmic neutrinos wouldn't drown out dark matter signals. A motto workshopped at the conference is "delve deep, search wide."

New methods are being tried by physicists. Long-lived particles will be looked for by both the ATLAS and theCMS during the third run. Researchers at Snowmass discussed how to find such particles, which can putter around before decaying, leading to unusual looking events.

Particle flavor is a quantum property that defines the species of fermion. There are anomalies that show flavor-based behavioral differences between electrons and muons that have reawakened interest in the subject. No one knows the answer toFlavor is something that no one knows the answer to Any theorist who says they know what the right model of flavor is is lying to you. Physicists might have to wait for more data. If the flavor anomalies seen in the Muon g-2 experiments are confirmed, it will become a top priority unknown.

There are visions from the frontier.

You could ask, "Which particle is the best to study?" if you wanted to conduct a quick version of Snowmass. Some physicists would choose mysterious neutrinos and others would choose muons or bottom quarks for their rare decays.

The drive to study the Higgs might be the most important choice. The measurement of the mass to one part per 1,000 is accurate, but there is still a lot of mystery about it. It's not clear how it ties to lighter particles. Through an upgrade later this decade, the LHC will accumulate more data than it has so far, which will allow it to make more precise measurements. The particle is fertile ground for new physics and models with multiple types of Higgs are easy to make. The field will be shaped regardless of what researchers learn about the particle.

Physicists want a new collider. They are tired of smashing protons and would prefer the more orderly collision of electrons and positrons. They could create a factory with more scrutiny if they created a cleaner collision. The International Linear collider could be built in Japan. Though it is shovel- ready, the project has been delayed for years and was dealt a blow when the Japanese government refused to allow it to go forward.

There is a proposed ring under a wide swathe of Swiss countryside. The FCC is likely to begin operations in the year 2050 according to the director general. The next collider will be hosted by physicists in the U.S. In a white paper released late last October, a team of researchers introduced a new technology that could allow for a smaller, cheaper and more feasible collider.

Many researchers don't like the idea of waiting 20 years or more for a factory. They would like to explore high energies far away from the LHC. The idea of a muon collider has been around for two years. Few theorists mourned the demise of the Muon Accelerator Program. The muon collider faces a lot of technical challenges. Many of the younger researchers wore stylish muon collider T-shirts at Snowmass, a propaganda feat that was later mimicked by cold- copper-collider proponents.

Where physicists want the most is where Snowmass struggles the most. The goal of the P5 is to outline a scientific vision without setting priorities. It is impractical to ignore all resources and constraints in order to create a scientific vision. At the latest Snowmass particle physicists could point to the promise of investigating Higgs parameters with a muon collider but not endorse a muon collider over any other alternative.

A clear vision was not immediately apparent. The task of refining 10 days and 500 white papers is now in the hands of P5.

Discussing the role of theorists with words that might also apply to his new role, Murayama said, "I hope we can provide guidance."