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Joerg Jaeckel

Publications and source records attributed to Joerg Jaeckel.

At least 145 records · Page 8Linked to original sources
arXiv2008

Searching Hidden-sector Photons inside a Superconducting Box

We propose an experiment to search for extra "hidden-sector" U(1) gauge bosons with gauge kinetic mixing with the ordinary photon, predicted by many extensions of the Standard Model. The setup consists of a highly sensitive magnetometer inside a superconducting shielding. This is then placed inside a strong (but sub-critical) magnetic field. In ordinary electrodynamics the magnetic field cannot permeate the superconductor and no field should register on the magnetometer. However, photon -- hidden-sector photon -- photon oscillations would allow to penetrate the superconductor and the magnetic field would "leak" into the shielded volume and register on the magnetometer. Although this setup resembles a classic ``light shining though a wall experiment'' there are two crucial differences. First, the fields are (nearly) static and the photons involved are virtual. Second, the magnetometer directly measures the field-strength and not a probability. This improves the dependence of the signal on the kinetic mixing chi (\ll 1) to chi^2 instead of chi^4. For hidden photon masses in the range 0.002-200 meV the projected sensitivity for the mixing parameter lies in the 5 10^-9 to 10^-6 range. This surpasses current astrophysical and laboratory limits by several orders of magnitude -- ample room to discover new physics.

hep-ph↗
arXiv2008

Signatures of a hidden cosmic microwave background

If there is a hidden photon -- i.e. a light abelian gauge boson in the hidden sector -- its kinetic mixing with the standard photon can produce a hidden cosmic microwave background (hCMB). For meV masses, resonant photon-hidden photon oscillations happen after nucleosynthesis (BBN) but before CMB decoupling, increasing the effective number of neutrinos but also the baryon to photon ratio. The current agreement between BBN and CMB data provides new constraints on the kinetic mixing. However, if one includes Lyman-alpha data, an effective number of neutrinos higher than 3 is preferred. It is tempting to interpret this effect in terms of the hCMB. Interestingly, the required parameters will be tested in the near future by laboratory experiments.

astro-ph↗
arXiv2008

Illuminating the Hidden Sector of String Theory by Shining Light through a Magnetic Field

Many models of physics beyond the Standard Model predict minicharged particles to which current and near future low-energy experiments are highly sensitive. Such minicharges arise generically from kinetic-mixing in theories containing at least two U(1) gauge factors. Here, we point out that the required multiple U(1) factors, the size of kinetic-mixing, and suitable matter representations to allow for a detection in the near future occur naturally in the context of string theory embeddings of the Standard Model. A detection of minicharged particles in a low energy experiment would likely be a signal of an underlying string theory and may provide a means of testing it.

hep-ph↗
arXiv2007

Dynamical breaking of U(1)_{R} and supersymmetry in a metastable vacuum

We consider the metastable N=1 QCD model of Intriligator, Seiberg and Shih (ISS), deformed by adding a baryon term to the superpotential. This simple deformation causes the spontaneous breaking of the approximate R-symmetry of the metastable vacuum. We then gauge the flavour SU(5)_f and identify it with the parent gauge symmetry of the Standard Model (SM). This implements direct mediation of supersymmetry breaking without the need for an additional messenger sector. A reasonable choice of parameters leads to gaugino masses of the right order. Finally, we speculate that the entire ``ISS x SM'' model should be interpreted as a magnetic dual of an (unknown) asymptotically free theory.

hep-ph↗
arXiv2007

A Cavity Experiment to Search for Hidden Sector Photons

We propose a cavity experiment to search for low mass extra U(1) gauge bosons with gauge-kinetic mixing with the ordinary photon, so-called paraphotons. The setup consists of two microwave cavities shielded from each other. In one cavity, paraphotons are produced via photon-paraphoton oscillations. The second, resonant, cavity is then driven by the paraphotons that permeate the shielding and reconvert into photons. This setup resembles the classic ``light shining through a wall'' setup. However, the high quality factors achievable for microwave cavities and the good sensitivity of microwave detectors allow for a projected sensitivity for photon-paraphoton mixing of the order of χ~10^{-12} to 10^{-8}, for paraphotons with masses in the μeV to meV range -- exceeding the current laboratory- and astrophysics-based limits by several orders of magnitude. Therefore, this experiment bears significant discovery potential for hidden sector physics.

hep-ph↗
arXiv2007

Photons as a Probe of Minicharged Particles

Low energy experiments with photons can provide deep insights into fundamental physics. In this note we concentrate on minicharged particles. We discuss how they can arise in extensions of the standard model and how we can search for them using a variety of laboratory experiments.

hep-ph↗
arXiv2007

Naturalised Supersymmetric Grand Unification

We construct a simple model of an SU(5) GUT with gauge mediated supersymmetry breaking from a metastable vacuum of a hidden sector. All mass parameters and hierarchies of our model are generated dynamically from retrofitting. This includes the mu-parameter and the GUT scale. However, as typical for SU(5) GUTs, proton longevity remains a problem.

hep-ph↗
arXiv2007

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.

hep-ph↗
arXiv2007

SUSY breaking by a metastable ground state: Why the early Universe preferred the non-supersymmetric vacuum

Supersymmetry breaking in a metastable vacuum is re-examined in a cosmological context. It is shown that thermal effects generically drive the Universe to the metastable minimum even if it begins in the supersymmetry-preserving one. This is a generic feature of the ISS models of metastable supersymmetry breaking due to the fact that SUSY preserving vacua contain fewer light degrees of freedom than the metastable ground state at the origin. These models of metastable SUSY breaking are thus placed on an equal footing with the more usual dynamical SUSY breaking scenarios.

hep-th↗
arXiv2006

On the Particle Interpretation of the PVLAS Data: Neutral versus Charged Particles

Recently the PVLAS collaboration reported the observation of a rotation of linearly polarized laser light induced by a transverse magnetic field - a signal being unexpected within standard QED. Two mechanisms have been proposed to explain this result: production of a single (pseudo-)scalar particle coupled to two photons or pair production of light millicharged particles. In this work, we study how the different scenarios can be distinguished. We summarize the expected signals for vacuum magnetic dichroism (rotation) and birefringence (ellipticity) for the different types of particles - including new results for the case of millicharged scalars. The sign of the rotation and ellipticity signals as well as their dependencies on experimental parameters, such as the strength of the magnetic field and the wavelength of the laser, can be used to obtain information about the quantum numbers of the particle candidates and to discriminate between the different scenarios. We perform a statistical analysis of all available data resulting in strongly restricted regions in the parameter space of all scenarios. These regions suggest clear target regions for upcoming experimental tests. As an illustration, we use preliminary PVLAS data to demonstrate that near future data may already rule out some of these scenarios.

hep-ph↗
arXiv2006

Why the early Universe preferred the non-supersymmetric vacuum: Part II

It was recently shown in hep-th/0610334 that in the context of the ISS models with a metastable supersymmetry breaking vacuum, thermal effects generically drive the Universe to the metastable vacuum even if it began after inflation in the supersymmetry-preserving one. We continue this programme and specifically take into account two new effects. First is the effect of the mass-gap of the gauge degrees of freedom in the confining supersymmetry preserving vacua, and second, is the effect of the back reaction of the MSSM sector on the SUSY breaking ISS sector. It is shown that, even though the mass-gap is parametrically smaller than the <ϕ> vevs, it drastically reduces the temperature required for the Universe to be driven to the metastable vacuum: essentially any temperature larger than the supersymmetry breaking scale μis sufficient. On the other hand we also find that any reasonable transmission of SUSY breaking to the MSSM sector has no effect on the vacuum transitions to, and the stability of the SUSY breaking vacuum. We conclude that for these models the early Universe does end up in the SUSY breaking vacuum.

hep-th↗
arXiv2006

Entropy Growth and the Dark Energy Equation of State

We revisit the conjecture of a generalized second law of thermodynamics which states that the combined entropy of matter and horizons must grow. In an expanding universe a generalized second law restricts the equation of state. In particular, it conflicts with long phases of a phantom, w<-1, equation of state.

astro-ph↗
arXiv2006

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.

hep-ph↗
arXiv2006

Vacuum Birefringence as a Probe of Planck Scale Noncommutativity

Because of ultraviolet/infrared (UV/IR) mixing, the low energy physics of noncommutative gauge theories in the Moyal-Weyl approach seems to depend crucially on the details of the ultraviolet completion. However, motivated by recent string theory analyses, we argue that their phenomenology with a very general class of UV completions can be accurately modelled by a cutoff close to the Planck scale. In the infrared the theory tends continuously to the commutative gauge theory. If the photon contains contributions from a trace-U(1), we would observe vacuum birefringence, i.e. a polarisation dependent propagation speed, as a residual effect of the noncommutativity. Constraints on this effect require the noncommutativity scale to be close to the Planck scale.

hep-ph↗
arXiv2006

Polarized Light Propagating in a Magnetic Field as a Probe of Millicharged Fermions

Possible extensions of the standard model of elementary particle physics suggest the existence of particles with small, unquantized electric charge. Photon initiated pair production of millicharged fermions in an external magnetic field would manifest itself as a vacuum magnetic dichroism. We show that laser polarization experiments searching for this effect yield, in the mass range below 0.1 eV, much stronger constraints on millicharged fermions than previously considered laboratory searches. Vacuum magnetic birefringence originating from virtual pair production gives a slightly better constraint for masses between 0.1 eV and a few eV. We comment on the possibility that the vacuum magnetic dichroism observed by PVLAS arises from pair production of such millicharged fermions rather than from single production of axion-like particles. Such a scenario can be confirmed or firmly excluded by a search for invisible decays of orthopositronium with a sensitivity of about 10^(-9) in the corresponding branching fraction.

hep-ph↗
arXiv2006

What measurable zero point fluctuations can(not) tell us about dark energy

We show that laboratory experiments cannot measure the absolute value of dark energy. All known experiments rely on electromagnetic interactions. They are thus insensitive to particles and fields that interact only weakly with ordinary matter. In addition, Josephson junction experiments only measure differences in vacuum energy similar to Casimir force measurements. Gravity, however, couples to the absolute value. Finally we note that Casimir force measurements have tested zero point fluctuations up to energies of ~10 eV, well above the dark energy scale of ~0.01 eV. Hence, the proposed cut-off in the fluctuation spectrum is ruled out experimentally.

astro-ph↗
arXiv2006

We need lab experiments to look for axion-like particles

The PVLAS signal has renewed the interest in light bosons coupled to the electromagnetic field. However, astrophysical bounds coming from the lifetime of the sun and the CAST experiment are seemingly in conflict with this result. We discuss effective models that allow to suppress production of axion-like particles in the sun and thereby relax the bounds by some orders of magnitude. This stresses the importance of laboratory searches.

hep-ph↗