arXiv subjects

Andreas Ringwald

Publications and source records attributed to Andreas Ringwald.

At least 55 records · Page 3Linked to original sources

arXiv2017

Stellar Recipes for Axion Hunters

There are a number of observational hints from astrophysics which point to the existence of stellar energy losses beyond the ones accounted for by neutrino emission. These excessive energy losses may be explained by the existence of a new sub-keV mass pseudoscalar Nambu--Goldstone boson with tiny couplings to photons, electrons, and nucleons. An attractive possibility is to identify this particle with the axion -- the hypothetical pseudo Nambu--Goldstone boson predicted by the Peccei--Quinn solution to the strong CP problem. We explore this possibility in terms of a DFSZ-type axion and of a KSVZ-type axion/majoron, respectively. Both models allow a good global fit to the data, prefering an axion mass around 10 meV. We show that future axion experiments -- the fifth force experiment ARIADNE and the helioscope IAXO -- can attack the preferred mass range from the lower and higher end, respectively. An axion in this mass range can also be the main constituent of dark matter.

hep-ph↗

arXiv2017

Standard Model-Axion-Seesaw-Higgs Portal Inflation. Five problems of particle physics and cosmology solved in one stroke

We present a minimal extension of the Standard Model (SM) providing a consistent picture of particle physics from the electroweak scale to the Planck scale and of cosmology from inflation until today. Three right-handed neutrinos $N_i$, a new color triplet $Q$ and a complex SM-singlet scalar $σ$, whose vacuum expectation value $v_σ\sim 10^{11}$ GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously, are added to the SM. At low energies, the model reduces to the SM, augmented by seesaw generated neutrino masses and mixing, plus the axion. The latter solves the strong CP problem and accounts for the cold dark matter in the Universe. The inflaton is comprised by a mixture of $σ$ and the SM Higgs, and reheating of the Universe after inflation proceeds via the Higgs portal. Baryogenesis occurs via thermal leptogenesis. Thus, five fundamental problems of particle physics and cosmology are solved at one stroke in this unified Standard Model - Axion - seesaw - Higgs portal inflation (SMASH) model. It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments.

hep-ph↗

arXiv2017

Unifying inflation with the axion, dark matter, baryogenesis and the seesaw mechanism

A minimal extension of the Standard Model (SM) with a single new mass scale and providing a complete and consistent picture of particle physics and cosmology up to the Planck scale is presented. We add to the SM three right-handed SM-singlet neutrinos, a new vector-like color triplet fermion and a complex SM singlet scalar $σ$ that stabilises the Higgs potential and whose vacuum expectation value at $\sim 10^{11}$ GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously. Primordial inflation is produced by a combination of $σ$ (non-minimally coupled to the scalar curvature) and the SM Higgs. Baryogenesis proceeds via thermal leptogenesis. At low energies, the model reduces to the SM, augmented by seesaw-generated neutrino masses, plus the axion, which solves the strong CP problem and accounts for the dark matter in the Universe. The model predicts a minimum value of the tensor-to-scalar ratio $r\simeq 0.004$, running of the scalar spectral index $α\simeq - 7\times 10^{-4}$, the axion mass $m_A\sim 100\,μ{\rm eV}$ and cosmic axion background radiation corresponding to an increase of the effective number of relativistic neutrinos of $\sim 0.03$. It can be probed decisively by the next generation of cosmic microwave background and axion dark matter experiments.

hep-ph↗

arXiv2016

Alternative dark matter candidates: Axions

The axion is arguably one of the best motivated candidates for dark matter. For a decay constant greater than about 10^9 GeV, axions are dominantly produced non-thermally in the early universe and hence are "cold", their velocity dispersion being small enough to fit to large scale structure. Moreover, such a large decay constant ensures the stability at cosmological time scales and its behaviour as a collisionless fluid at cosmological length scales. Here, we review the state of the art of axion dark matter predictions and of experimental efforts to search for axion dark matter in laboratory experiments.

hep-ph↗

arXiv2016

SMAS*H

We present a minimal model for particle physics and cosmology. The Standard Model (SM) particle content is extended by three right-handed SM-singlet neutrinos N_i and a vector-like quark Q, all of them being charged under a global lepton number and Peccei-Quinn (PQ) U(1) symmetry which is spontaneously broken by the vacuum expectation value v_sigma around 10^{11} GeV of a SM-singlet complex scalar field sigma. Five fundamental problems -- neutrino oscillations, baryogenesis, dark matter, inflation, strong CP problem -- are solved at one stroke in this model, dubbed "SM*A*S*H" (Standard Model*Axion*Seesaw*Higgs portal inflation). It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments.

hep-ph↗

arXiv2016

Probing axions with the neutrino signal from the next galactic supernova

We study the impact of axion emission in simulations of massive star explosions, as an additional source of energy loss complementary to the standard neutrino emission. The inclusion of this channel shortens the cooling time of the nascent protoneutron star and hence the duration of the neutrino signal. We treat the axion-matter coupling strength as a free parameter to study its impact on the protoneutron star evolution as well as on the neutrino signal. We furthermore analyze the observability of the enhanced cooling in current and next-generation underground neutrino detectors, showing that values of the axion mass $m_a \gtrsim 8 \times 10^{-3}$ eV can be probed. Therefore a galactic supernova neutrino observation would provide a valuable possibility to probe axion masses in a range within reach of the planned helioscope experiment, the International Axion Observatory (IAXO).

astro-ph.HE↗

arXiv2016

Cool WISPs for stellar cooling excesses

Several stellar systems (white dwarfs, red giants, horizontal branch stars and possibly the neutron star in the supernova remnant Cassiopeia A) show a mild preference for a non-standard cooling mechanism when compared with theoretical models. This exotic cooling could be provided by Weakly Interacting Slim Particles (WISPs), produced in the hot cores and abandoning the star unimpeded, contributing directly to the energy loss. Taken individually, these excesses do not show a strong statistical weight. However, if one mechanism could consistently explain several of them, the hint could be significant. We analyze the hints in terms of neutrino anomalous magnetic moments, minicharged particles, hidden photons and axion-like particles (ALPs). Among them, the ALP or a massless HP represent the best solution. Interestingly, the hinted ALP parameter space is accessible to the next generation proposed ALP searches, such as ALPS II and IAXO and the massless HP requires a multi TeV energy scale of new physics that might be accessible at the LHC.

astro-ph.HE↗

arXiv2016

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 $Z_N$ symmetry. For $N = 9$ or $10$, 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 $N_{\rm DW}>1$, such as the popular Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model ($N_{\rm DW}=6$), cosmologically viable even in the case where spontaneous PQ symmetry breaking occurred after inflation. We find that $N=10$ DFSZ accions with mass $m_A \approx 3.5$-$4.2\,\mathrm{meV}$ 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.

hep-ph↗

arXiv2016

ALPtraum: ALP production in proton beam dump experiments

With their high beam energy and intensity, existing and near-future proton beam dumps provide an excellent opportunity to search for new very weakly coupled particles in the MeV to GeV mass range. One particularly interesting example is a so-called axion-like particle (ALP), i.e. a pseudoscalar coupled to two photons. The challenge in proton beam dumps is to reliably calculate the production of the new particles from the interactions of two composite objects, the proton and the target atoms. In this work we argue that Primakoff production of ALPs proceeds in a momentum range where production rates and angular distributions can be determined to sufficient precision using simple electromagnetic form factors. Reanalysing past proton beam dump experiments for this production channel, we derive novel constraints on the parameter space for ALPs. We show that the NA62 experiment at CERN could probe unexplored parameter space by running in 'dump mode' for a few days and discuss opportunities for future experiments such as SHiP.

hep-ph↗

arXiv2015

WISPDMX: A haloscope for WISP Dark Matter between 0.8-2 $μ$eV

Weakly interactive slim particles (WISPs), including the QCD axion, axion-like particles (ALPs), and hidden photons, are considered to be strong candidates for the dark matter carrier particle. The microwave cavity experiment WISPDMX is the first direct WISP dark matter search experiment probing the particle masses in the 0.8-2.0 $μ$eV range. The first stage of WISPDMX measurements has been completed at nominal resonant frequencies of the cavity. The second stage of WISPDMX is presently being prepared, targeting hidden photons and axions within 60\% of the entire 0.8-2.0 $μ$eV mass range.

physics.ins-det↗

arXiv2015

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.

hep-ph↗

arXiv2015

A facility to Search for Hidden Particles at the CERN SPS: the SHiP physics case

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (Search for Hidden Particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, $τ\to 3μ$ and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the Standard Model and describe interactions between new particles and four different portals - scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the Standard Model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation

hep-ph↗

arXiv2015

Results from the Solar Hidden Photon Search (SHIPS)

We present the results of a search for transversely polarised hidden photons (HPs) with $\sim 3$ eV energies emitted from the Sun. These hypothetical particles, known also as paraphotons or dark sector photons, are theoretically well motivated for example by string theory inspired extensions of the Standard Model. Solar HPs of sub-eV mass can convert into photons of the same energy (photon$\leftrightarrow$HP oscillations are similar to neutrino flavour oscillations). At SHIPS this would take place inside a long light-tight high-vacuum tube, which tracks the Sun. The generated photons would then be focused into a low-noise photomultiplier at the far end of the tube. Our analysis of 330 h of data (and {330 h} of background characterisation) reveals no signal of photons from solar hidden photon conversion. We estimate the rate of newly generated photons due to this conversion to be smaller than 25 mHz/m$^2$ at the 95$%$ C.L. Using this and a recent model of solar HP emission, we set stringent constraints on $χ$, the coupling constant between HPs and photons, as a function of the HP mass.

hep-ph↗

arXiv2015

Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles

We revise the bound from the supernova SN1987A on the coupling of ultralight axion-like particles (ALPs) to photons. In a core-collapse supernova, ALPs would be emitted via the Primakoff process, and eventually convert into gamma rays in the magnetic field of the Milky Way. The lack of a gamma-ray signal in the GRS instrument of the SMM satellite in coincidence with the observation of the neutrinos emitted from SN1987A therefore provides a strong bound on their coupling to photons. Due to the large uncertainty associated with the current bound, we revise this argument, based on state-of-the-art physical inputs both for the supernova models and for the Milky-Way magnetic field. Furthermore, we provide major amendments, such as the consistent treatment of nucleon-degeneracy effects and of the reduction of the nuclear masses in the hot and dense nuclear medium of the supernova. With these improvements, we obtain a new upper limit on the photon-ALP coupling: g_{aγ} < 5.3 x 10^{-12} GeV^{-1}, for m_a < 4.4 x 10^{-10} eV, and we also give its dependence at larger ALP masses. Moreover, we discuss how much the Fermi-LAT satellite experiment could improve this bound, should a close-enough supernova explode in the near future.

astro-ph.HE↗

arXiv2014

WISP Dark Matter eXperiment and Prospects for Broadband Dark Matter Searches in the $1\,μ$eV--$10\,$meV Mass Range

Light cold dark matter consisting of weakly interacting slim (or sub-eV) particles (WISPs) has been in the focus of a large number of studies made over the past two decades. The QCD axion and axion-like particles with masses in the $0.1\,μ$eV--$100\,$meV are strong candidates for the dark matter particle, together with hidden photons with masses below $\lesssim 100\,$meV. This motivates several new initiatives in the field, including the WISP Dark Matter eXperiment (WISPDMX) and novel conceptual approaches for broad-band WISP searches using radiometry measurements in large volume chambers. First results and future prospects for these experiments are discussed in this contribution.

hep-ex↗

arXiv2014

A 3.55 keV hint for decaying axion-like particle dark matter

Recently, indications for an emission line at 3.55 keV have been found in the combined spectra of a large number of galaxy clusters and also in Andromeda. This line could not be identified with any known spectral line. It is tempting to speculate that it has its origin in the decay of a particle contributing all or part of the dark matter. In this note we want to point out that axion-like particles being all or part of the dark matter are an ideal candidate to produce such a feature. More importantly the parameter values necessary are quite feasible in extensions of the Standard Model based on string theory and could be linked up to a variety of other intriguing phenomena, which also potentially allow for new tests of this speculation.

hep-ph↗

arXiv2013

WISPers from the Dark Side: Radio Probes of Axions and Hidden Photons

Measurements in the radio regime embrace a number of effective approaches for WISP searches, often covering unique or highly complementary ranges of the parameter space compared to those explored in other research domains. These measurements can be used to search for electromagnetic tracers of the hidden photon and axion oscillations, extending down to ~10^-19 eV the range of the hidden photon mass probed, and closing the last gaps in the strongly favoured 1-5 micro-eV range for axion dark matter. This provides a strong impetus for several new initiatives in the field, including the WISP Dark Matter eXperiment (WISPDMX) and novel conceptual approaches for broad-band WISP searches in the 0.1-1000 micro-eV range.

physics.ins-det↗

arXiv2013

Any Light Particle Search II -- Technical Design Report

This document constitutes an excerpt of the Technical Design Report for the second stage of the "Any Light Particle Search" (ALPS-II) at DESY as submitted to the DESY PRC in August 2012 and reviewed in November 2012. ALPS-II is a "Light Shining through a Wall" experiment which searches for photon oscillations into weakly interacting sub-eV particles. These are often predicted by extensions of the Standard Model and motivated by astrophysical phenomena. The first phases of the ALPS-II project were approved by the DESY management on February 21st, 2013.

physics.ins-det↗