Editing Particle physics (section)

==Future==
The primary goal, which is pursued in several distinct ways, is to find and understand what physics may lie [[beyond the standard model]]. There are several powerful experimental reasons to expect new physics, including [[dark matter]] and [[neutrino mass]]. There are also theoretical hints that this new physics should be found at accessible energy scales.

Much of the effort to find beyond Standard Model physics has been focused on new collider experiments.   As of March, 2023,   no beyond-Standard-Model signatures are observed at the [[Large Hadron Collider]] (LHC).   This implies that new physics signals must be too rare or else manifest at too high energy to be observed at LHC.    To address rare signals, one builds a very high rate source with low backgrounds.    This is the concept behind the multiple [[Higgs factory]] proposals.   These consist of lepton-lepton (either electron-positron or muon-antimuon) colliders with center of mass energy chosen to produce Higgs particles.  Because the leptons annihilate, the events in the detector have few extraneous particles, unlike hadron colliders.   This allows for accurate event reconstruction.  New physics is probed by high precision reconstruction of the large sample of Higgs bosons.   A hadron or [[muon collider]] is necessary to reach higher energies. The [[Future Circular Collider]] proposed for CERN is an example of a 100 TeV center of mass proton collider proposal, representing an order of magnitude energy increase over the LHC with a 90 km circumference. A 10 TeV muon collider would probe similar energies to a 100 TeV proton collider, with a circumference of just 10 km.<ref>{{Cite web |title=Muon Colliders Hold a Key to Unraveling New Physics |url=http://www.aps.org/publications/apsnews/202111/muon.cfm |access-date=2023-09-17 |website=www.aps.org |language=en}}</ref> 

There are important non-collider experiments that attempt to find and understand [[physics beyond the Standard Model]]. One is the determination of the [[neutrino]] masses, since these masses may arise from neutrinos mixing with very heavy particles. Another is [[physical cosmology|cosmological]] observations that provide constraints on the dark matter, although it may be impossible to determine the exact nature of the dark matter without the colliders. Finally, lower bounds on the very long [[proton decay|lifetime of the proton]] put constraints on [[Grand Unified Theory|Grand Unified Theories]] at energy scales much higher than collider experiments will be able to probe any time soon.

In 2023, the [[Particle Physics Project Prioritization Panel]] (P5) began a new decadal study on the future of particle physics in the US that will update the 2014 P5 study that recommended the [[Deep Underground Neutrino Experiment]], among other experiments.