Snowmass Process

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The Snowmass Process is a particle physics community planning exercise sponsored by the Division of Particles and Fields of the American Physical Society. [1] During this process, scientists develop a collective vision for the next seven to ten years for particle physics research in the US. [2]

Contents

History

Original planning meetings were held beginning in 1982 in Snowmass, Colorado, [3] [4] but that has not been the location since 2005. [5] [6] More recent locations of the Snowmass Process include the University of Minnesota (2013) [7] and the University of Washington (2021), which was delayed until July 2022, due to COVID. [8]

Description

The modern Snowmass Process consists of a series of small meetings, which culminate in a community-wide meeting. The Snowmass Process solicits reports on progress and plans within "frontiers." Snowmass 2021 identified ten frontiers: "energy; neutrino physics; rare processes and precision measurements; cosmic; theory; accelerator; instrumentation; computation; underground facilities; and community engagement". [8]

Members of the particle physics community submit Letters of interest [9] and provide input to contributed whitepapers. [8] The frontiers use these whitepapers to provide web-based reports based on the material that they receive. The final output of the Snowmass Process is a Snowmass Summary for the Public, a Snowmass Summary Report, and the Snowmass Book. [10]

Outcomes of Snowmass 2013

The Snowmass Process outcomes of 2013 were used to inform the decisions of the 2014 Particle Physics Project Prioritization Panel. [11] A newsworthy outcome of the 2021 Snowmass Process was the announcement that the Deep Underground Neutrino Experiment would be pursued in two distinct phases. [12] [13]

Outcomes of Snowmass 2021

The outcomes of the Snowmass 2021 process, which extended into 2022, were determined at a final meeting held in July 2022 in Seattle, Washington that had 743 in-person attendees and 654 virtual participants. [14] Snowmass outcomes were covered in detailed articles by the scientific press. [15] [16] The title of the Scientific American article, “Physicists Struggle to Unite Around Future Plans,” summed up the problem of convergence of opinion. [16] The articles report that two major problems stymied the field: lack of observation of new particles and rocketing costs of ongoing projects.

No unexpected particles were observed in the first 15 years of data-taking at the Large Hadron Collider (LHC), the highest energy accelerator on Earth—a disappointment stated by many physicists throughout the Snowmass process, [16] and reflecting a view that has also been expressed outside of the Snowmass meetings. [17] Although LHC will continue to run with modest upgrades, this lack of discovery leaves no clear focus for the next decade of high energy searches, and may also point to a “nightmare-scenario” where the Standard Model that forms the present basis of particle physics is complete up to the Planck scale (an energy level far beyond the ability of any conceivable experiment to probe) and particle physics “wheeze[s] to its end.” [17]

However the 2012 the discovery of an expected particle, the Higgs Boson, has given the field hope of finding new physics through precision searches for unexpected Higgs interactions. As a result, during the Snowmass process, physicists argued for precision measurements at a Higgs factory constructed of an electron-positron collider. [15] [16] Many Higgs factories are proposed for outside of the US, including at the European center for particle physics, CERN, as well as in China, and so "a surprise at Snowmass 'was the grassroots support for a collider on US soil'" [15] that grew out of a new US-developed technology called the "cool copper collider." [18] An alternative if the world-wide competition for an electron-positron machine is too stiff would be to invest in a Muon collider that could act as a Higgs factory with an approach that is unique worldwide. Muon colliders were discussed at the 2013 Snowmass, but shelved due to insufficiently advanced technology. However, at the 2022 final Snowmass meeting there was an "enthusiastic revival" of the concept. [15]

The possibility of establishing any major new project in the US in the 2023-2033 decade, including a Higgs Factory, is limited due to the rising costs and multi-year delays of existing projects. In particular, at Snowmass, physicists expressed deep concern about the Deep Underground Neutrino Experiment (DUNE) project, which has risen from a base cost of $1.3B in 2015 to $3.1B for a de-scoped instrument. [15] Cost over-runs and delays of DUNE are problematic due to stiff competition from a similar experiment in Japan, [15] [16] leaving physicists to question the value of DUNE results when they are obtained. Worries were expressed by physicists that issues with DUNE were "smoothed over, not smoothed out." [15] Some physicists at Snowmass suggested that the DUNE project might be cancelled, comparing the ominous cost-growth to the Superconducting Super Collider (SSC) that was cancelled when the cost tripled. [16]

The whitepapers from the Snowmass process provide input to the 2023 P5 study. The 2023 P5 committee was announced in December 2022. [19]

See also

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<span class="mw-page-title-main">Large Electron–Positron Collider</span> Particle accelerator at CERN, Switzerland

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]

A Higgs factory is a particle accelerator designed to produce Higgs bosons at a very high rate, allowing precision studies of this particle. A Higgs factory was identified as the highest future priority of particle physics in the 2020 European Strategy Report. This view was reaffirmed in 2022 by the International Committee on Future Accelerators.

References

  1. ↑ Shiltsev, V. "Snowmass'21: the US particle physics community planning". SIF Primapagina. Retrieved 26 April 2022.
  2. ↑ Herschberger, Scott (1 October 2020). "Defining the next decade of US particle physics". Symmetry Magazine. Retrieved 25 April 2022.
  3. ↑ "Proceedings, 1982 DPF Summer Study on Elementary Particle Physics and Future Facilities (Snowmass 82) : Snowmass, Colorado, June 28-July 16,1982". inspirehep.net. Retrieved 27 April 2022.
  4. ↑ "Snowmass Meeting Charts Course for High Energy Physics". aps.org. Retrieved 26 April 2022.
  5. ↑ "2005 International Linear Collider Physics and Detector Workshop and 2nd ILC Accelerator Workshop". inspirehep.net. 2005. Retrieved 27 April 2022.
  6. ↑ "Proceedings, 2013 Community Summer Study on the Future of U.S. Particle Physics: Snowmass on the Mississippi (CSS2013) : Minneapolis, MN, USA, July 29-August 6, 2013". inspirehep.net. Retrieved 27 April 2022.
  7. ↑ "Snowmass on the Mississippi". indico.fnal.gov. 2013. Retrieved 26 April 2022.
  8. 1 2 3 Han, Tao (24 January 2022). "Snowmass promises bright future". The CERN Courier. CERN.
  9. ↑ Sundermier, Ali. "Physicists submit avalanche of ideas to 'Snowmass' process". symmetry magazine. Retrieved 26 April 2022.
  10. ↑ "Preparation Site for the Snowmass Report, SnowMass2021". snowmass21.org. Retrieved 26 April 2022.
  11. ↑ Adrian Cho (22 May 2014). "New Plan for U.S. Particle Physics: Go International". Science, American Association for the Advancement of Science.
  12. ↑ Adrian Cho (29 March 2022). "Trying to stay ahead of competition, U.S. pares down troubled $3 billion neutrino experiment". Science, American Association for the Advancement of Science.
  13. ↑ Lewton, Thomas (13 April 2022). "Troubled U.S. Neutrino Project Faces Uncertain Future–and Fresh Opportunities". Scientific American. Retrieved 13 April 2022.
  14. ↑ "Workshop Participant List". Snowmass Community Summer Study Workshop. American Physical Society Division of Particles and Fields. Retrieved 27 December 2022.
  15. 1 2 3 4 5 6 7 Feder, Toni (October 2022). "US particle physicists envision future of the field". Physics Today. 75 (10): 22–23. Bibcode:2022PhT....75j..22F. doi: 10.1063/PT.3.5097 .
  16. 1 2 3 4 5 6 Garisto, Daniel (8 September 2022). "Physicists Struggle to Unite around Future Plans". Scientific American. Retrieved 27 December 2022.
  17. 1 2 Cho, Adrian (12 June 2022). "Ten years after the Higgs, physicists face the nightmare of finding nothing else". Science.
  18. ↑ Schirber, Michael (6 October 2022). "A "Retro" Collider Design for a Higgs Factory". Physics Magazine. Vol. 15, no. 155. Retrieved 27 December 2022.
  19. ↑ "Particle Physics Planning Process Moves Into Final Phase". No. The Week of December 5, 2022. American Institute of Physics. FYI: Science Policy News from AIP. 5 December 2022. Retrieved 27 December 2022.
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