372 research outputs found
The hunt for axions
Many theoretically well-motivated extensions of the Standard Model of
particle physics predict the existence of the axion and further ultralight
axion-like particles. They may constitute the mysterious dark matter in the
universe and solve some puzzles in stellar and high-energy astrophysics. There
are new, relatively small experiments around the globe, which started to hunt
for these elusive particles and complement the accelerator based search for
physics beyond the Standard Model.Comment: 11 pages, invited talk at XVI International Workshop on Neutrino
Telescopes, 2-6 March 2015, Palazzo Franchetti, Istituto Veneto, Venice,
Ital
Multi-W(Z) Production in High-Energy Collisions?
There exists the possibility that the cross-section for the nonperturbative
production of many, , weak gauge bosons may
be as large as b above a parton-parton
center-of-mass threshold in the range TeV. We review the
theoretical considerations which lead to this suggestion and outline its
phenomenological implications, both for present cosmic ray as well as for
future collider experiments. (Lecture presented at the 4th Hellenic School on
Elementary Particle Physics, September 2-20, 1992, Corfu, Greece) (Figures not
included, available by ordinary mail)Comment: 15 pages, CERN-TH.6862/9
Axion dark matter in the post-inflationary Peccei-Quinn symmetry breaking scenario
We consider extensions of the Standard Model in which a spontaneously broken
global chiral Peccei-Quinn (PQ) symmetry arises as an accidental symmetry of an
exact symmetry. For or , this symmetry can protect the accion
- the Nambu-Goldstone boson arising from the spontaneous breaking of the
accidental PQ symmetry - against semi-classical gravity effects, thus
suppressing gravitational corrections to the effective potential, while it can
at the same time provide for the small explicit symmetry breaking term needed
to make models with domain wall number , such as the popular
Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model (),
cosmologically viable even in the case where spontaneous PQ symmetry breaking
occurred after inflation. We find that DFSZ accions with mass - can account for cold dark matter and
simultaneously explain the hints for anomalous cooling of white dwarfs. The
proposed helioscope International Axion Observatory - being sensitive to solar
DFSZ accions with mass above a few meV - will decisively test this scenario.Comment: 12 pages, 4 figures; revised version of the manuscript, accepted for
publication in PR
Axion mass in the case of post-inflationary Peccei-Quinn symmetry breaking
The axion not only solves the strong CP puzzle, but it also may be the main
constituent of cold dark matter. We review the axion dark matter predictions
for the case that the Peccei-Quinn symmetry is restored after inflation.Comment: 4 pages, contribution to the Proceedings of the 53rd Rencontres de
Morion
Photon Regeneration from Pseudoscalars at X-ray Laser Facilities
Recently, the PVLAS collaboration has reported an anomalously large rotation
of the polarization of light in the presence of a magnetic field. As a possible
explanation they consider the existence of a light pseudoscalar particle
coupled to two photons. In this note, we propose a method of independently
testing this result by using a high-energy photon regeneration experiment (the
X-ray analogue of "invisible light shining through walls") using the
synchrotron X-rays from a free-electron laser (FEL). With such an experiment
the region of parameter space implied by PVLAS could be probed in a matter of
minutes.Comment: 3 pages, 2 figure
Axion dark matter (theory & experiment)
We review the motivation for the axion as a solution of the strong CP puzzle
and as a candidate for cold dark matter. Then we discuss benchmark axion models
and present their predictions concerning axion couplings to the Standard Model
and axion dark matter abundance. Finally, we give an overview on the discovery
potential of current and planned axion experiments, reaching from axion dark
matter direct detection, over searches for solar axions, to direct production
and detection of axions in the laboratory.Comment: 11 pages, 5 figures, contribution to the proceedings of the XVIII
International Conference on Topics in Astroparticle and Underground Physics
(TAUP2023
Limits on Electroweak Instanton-Induced Processes with Multiple Boson Production
Recently, the CMS collaboration has reported their search for electroweak
instanton-like processes with anomalous violation assuming multi-fermion
but zero-boson final states. On the other hand, many theoretical studies
suggest that anomalous processes may have an observably large production
rate only if their final state contains a large number of electroweak gauge
bosons. In this paper, we compare collider signatures of zero- and multi-boson
events of anomalous violation at the LHC and derive an upper limit on the
cross-section for the multi-boson process by recasting the CMS analysis.Comment: 14 pages, 6 figures; JHEP version with typographic errors fixe
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