71 research outputs found
Axion interpretation of the PVLAS data?
The PVLAS collaboration has recently reported the observation of a rotation
of the polarization plane of light propagating through a transverse static
magnetic field. Such an effect can arise from the production of a light, m_A ~
meV, pseudoscalar coupled to two photons with coupling strength g_{A\gamma} ~
5x10^{-6} GeV^{-1}. Here, we review these experimental findings, discuss how
astrophysical and helioscope bounds on this coupling can be evaded, and
emphasize some experimental proposals to test the scenario.Comment: 4 pages, 1 figure, jpconf.cls, talk presented at the ninth
International Conference on Topics in Astroparticle and Underground Physics,
TAUP 2005, Zaragoza, Spain, September 10-14, 200
New Experimental Limit on Photon Hidden-Sector Paraphoton Mixing
We report on the first results of a search for optical-wavelength photons
mixing with hypothetical hidden-sector paraphotons in the mass range between
10^-5 and 10^-2 electron volts for a mixing parameter greater than 10^-7. This
was a generation-regeneration experiment using the "light shining through a
wall" technique in which regenerated photons are searched for downstream of an
optical barrier that separates it from an upstream generation region. The new
limits presented here are approximately three times more sensitive to this
mixing than the best previous measurement. The present results indicate no
evidence for photon-paraphoton mixing for the range of parameters investigated.Comment: 9 pages, 3 figure
External Fields as a Probe for Fundamental Physics
Quantum vacuum experiments are becoming a flexible tool for investigating
fundamental physics. They are particularly powerful for searching for new light
but weakly interacting degrees of freedom and are thus complementary to
accelerator-driven experiments. I review recent developments in this field,
focusing on optical experiments in strong electromagnetic fields. In order to
characterize potential optical signatures, I discuss various low-energy
effective actions which parameterize the interaction of particle-physics
candidates with optical photons and external electromagnetic fields.
Experiments with an electromagnetized quantum vacuum and optical probes do not
only have the potential to collect evidence for new physics, but
special-purpose setups can also distinguish between different particle-physics
scenarios and extract information about underlying microscopic properties.Comment: 12 pages, plenary talk at QFEXT07, Leipzig, September 200
Do Instantons Like a Colorful Background?
We investigate chiral symmetry breaking and color symmetry breaking in QCD.
The effective potential of the corresponding scalar condensates is discussed in
the presence of non-perturbative contributions from the semiclassical
one-instanton sector. We concentrate on a color singlet scalar background which
can describe chiral condensation, as well as a color octet scalar background
which can generate mass for the gluons. Whereas a non-vanishing singlet chiral
field is favored by the instantons, we have found no indication for a
preference of color octet backgrounds.Comment: 25 pages, 7 figure
Axion-like particle effects on the polarization of cosmic high-energy gamma sources
Various satellite-borne missions are being planned whose goal is to measure
the polarization of a large number of gamma-ray bursts (GRBs). We show that the
polarization pattern predicted by current models of GRB emission can be
drastically modified by the existence of very light axion-like particles
(ALPs), which are present in many extensions of the Standard Model of particle
physics. Basically, the propagation of photons emitted by a GRB through cosmic
magnetic fields with a domain-like structure induces photon-ALP mixing, which
is expected to produce a strong modification of the original photon
polarization. Because of the random orientation of the magnetic field in each
domain, this effect strongly depends on the orientation of the photon line of
sight. As a consequence, photon-ALP conversion considerably broadens the
original polarization distribution. Searching for such a peculiar feature
through future high-statistics polarimetric measurements is therefore a new
opportunity to discover very light ALPs.Comment: Final version (21 pages, 8 eps figures). Matches the version
published on JCAP. Added a Section on the effects of cosmic expansion on
photon-ALP conversions. Figures modified to take into account this effect.
References updated. Conclusions unchanged
Axions, their Relatives and Prospects for the Future
The observation of a non-vanishing rotation of linear polarized laser light
after passage through a strong magnetic field by the PVLAS collaboration has
renewed the interest in light particles coupled to photons. Axions are a
species of such particles that is theoretically well motivated. However, the
relation between coupling and mass predicted by standard axion models conflicts
with the PVLAS observation. Moreover, light particles with a coupling to
photons of the strength required to explain PVLAS face trouble from
astrophysical bounds. We discuss models that can avoid these bounds. Finally,
we present some ideas to test these possible explanations of PVLAS
experimentally.Comment: 11 pages, 4 figures. Contributed to the ``Third Symposium on Large
TPCs for Low Energy Rare Event Detection'' in Paris, December 200
Feebly-interacting particles: FIPs 2020 workshop report
With the establishment and maturation of the experimental programs searching for new physics with sizeable couplings at the LHC, there is an increasing interest in the broader particle and astrophysics community for exploring the physics of light and feebly-interacting particles as a paradigm complementary to a New Physics sector at the TeV scale and beyond. FIPs 2020 has been the first workshop fully dedicated to the physics of feebly-interacting particles and was held virtually from 31 August to 4 September 2020. The workshop has gathered together experts from collider, beam dump, fixed target experiments, as well as from astrophysics, axions/ALPs searches, current/future neutrino experiments, and dark matter direct detection communities to discuss progress in experimental searches and underlying theory models for FIPs physics, and to enhance the cross-fertilisation across different fields. FIPs 2020 has been complemented by the topical workshop Physics Beyond Colliders meets theory, held at CERN from 7 June to 9 June 2020. This document presents the summary of the talks presented at the workshops and the outcome of the subsequent discussions held immediately after. It aims to provide a clear picture of this blooming field and proposes a few recommendations for the next round of experimental results
Dark Matter Candidates: A Ten-Point Test
An extraordinarily rich zoo of non-baryonic Dark Matter candidates has been
proposed over the last three decades. Here we present a 10-point test that a
new particle has to pass, in order to be considered a viable DM candidate: I.)
Does it match the appropriate relic density? II.) Is it {\it cold}? III.) Is it
neutral? IV.) Is it consistent with BBN? V.) Does it leave stellar evolution
unchanged? VI.) Is it compatible with constraints on self-interactions? VII.)
Is it consistent with {\it direct} DM searches? VIII.) Is it compatible with
gamma-ray constraints? IX.) Is it compatible with other astrophysical bounds?
X.) Can it be probed experimentally?Comment: 29 pages, 12 figure
Future axion searches with the International Axion Observatory (IAXO)
The International Axion Observatory (IAXO) is a new generation axion helioscope aiming at a sensitivity to the axion-photon coupling of ga\u3b3 3c few
7 10-12 GeV-1, i.e. 1-1.5 orders of magnitude beyond the one achieved by CAST, currently the most sensitive axion helioscope. The main elements of IAXO are an increased magnetic field volume together with extensive use of x-ray focusing optics and low background detectors, innovations already successfully tested in CAST. Additional physics cases of IAXO could include the detection of electron-coupled axions invoked to explain the white dwarf cooling, relic axions, and a large variety of more generic axion-like particles (ALPs) and other novel excitations at the low-energy frontier of elementary particle physics
- âŠ