Audible Axions

Conventional approaches to probing axions and axion-like particles (ALPs) typically rely on a coupling to photons. However, if this coupling is extremely weak, ALPs become invisible and are effectively decoupled from the Standard Model. Here we show that such invisible axions, which are viable candidates for dark matter, can produce a stochastic gravitational wave background in the early universe. This signal is generated in models where the invisible axion couples to a dark gauge boson that experiences a tachyonic instability when the axion begins to oscillate. Incidentally, the same mechanism also widens the viable parameter space for axion dark matter. Quantum fluctuations amplified by the exponentially growing gauge boson modes source chiral gravitational waves. For axion decay constants $f \gtrsim 10^{17}$ GeV, this signal is detectable by either pulsar timing arrays or space/ground-based gravitational wave detectors for a broad range of axion masses, thus providing a new window to probe invisible axion models.Comment: 8 pages, 4 figures. References added, version submitted to JHE

Looking for a light Higgs boson in the overlooked channel

The final state obtained when a Higgs boson decays to a photon and a Z boson has been mostly overlooked in current searches for a light Higgs boson. However, when the Z boson decays leptonically, all final state particles in this channel can be measured, allowing for accurate reconstructions of the Higgs mass and angular correlations. We determine the sensitivity of the Large Hadron Collider (LHC) running at center of masses energies of 8 and 14 TeV to Standard Model (SM) Higgs bosons with masses in the 120 - 130 GeV range. For the 8 TeV LHC, sensitivity to several times the the SM cross section times branching ratio may be obtained with 20 inverse femtobarns of integrated luminosity, while for the 14 TeV LHC, the SM rate is probed with about 100 inverse femtobarns of integrated luminosity.Comment: 4 pages, 4 figures. Improves on version 1 in that 8 and 14 TeV LHC running is considered, the case of a 125 GeV Higgs is treated specifically, and the effect of an additional jet in the final state has been taken into account in studying experimental sensitivit

Search for Higgs Bosons in SUSY Cascade Decays and Neutralino Dark Matter

The Minimal Supersymmetric Extension of the Standard Model (MSSM) is a well motivated theoretical framework, which contains an extended Higgs sector, including a light Higgs with Standard Model-like properties in most of the parameter space. Due to the large QCD background, searches for such a Higgs, decaying into a pair of bottom quarks, is very challenging at the LHC. It has been long realized that the situation may be ameliorated by searching for Higgs bosons in supersymmetric decay chains. Moreover, it has been recently suggested that the bobber decay channel may be observed in standard production channels by selecting boosted Higgs bosons, which may be easily identified from the QCD background. Such boosted Higgs bosons are frequent in the MSSM, since they are produced from decays of heavy colored supersymmetric particles. Previous works have emphasized the possibility of observing boosted Higgs bosons in the light higgsino region. In this work, we study the same question in the regions of parameter space consistent with a neutralino dark matter relic density, analyzing its dependence on the non-standard Higgs boson, slepton and squark masses, as well as on the condition of gaugino mass unification. In general, we conclude that, provided sleptons are heavier than the second lightest neutralinos, the presence of boosted Higgs is a common MSSM feature, implying excellent prospects for observation of the light MSSM Higgs boson in the near future.Comment: 30 pages, 9 figures. v2: New Xenon 100 results implemented, version to appear in PR

Influence of the pre-treatment of glass substrates on Laser-Induced Backside Wet Etching using NIR Nanosecond-Pulses and Cu-based solutions

Laser induced backside wet etching (LIBWE) has shown to be a promising tool for the micro-structuring of transparent materials. Our group has investigated LIBWE using NIR ns-laser pulses and Cu-based absorber liquids. Focus of this paper is to investigate the influence of the pre-treatment of the transparent substrate on ablation. For this purpose experiments were done on untreated and silanized soda lime glass surfaces. Our results show that depending on the absorber liquid the silanization of the substrate either enhances or delays the ablation. Possible ablation models for the different experimental settings will be discussed

Laser-induced chemical liquid-phase deposition of copper on transparent substrates

Laser-induced chemical liquid phase deposition allows maskless manufacturing of metallic structures on the surface of dielectrics and is prospected to be a promising tool in the field of microelectronics and microfluidics. The aim of the work presented here is to combine this deposition method with a related micro-structuring method known as laser-induced backside wet etching. Fabricating both, microstructured surface structures and subsequent deposition of conducting patterns within the same setup would be an interesting tool for rapid prototyping.To demonstrate the functional principle of this combined approach conductive copper lines were deposited at the backside of both polished and structured soda lime glass substrates by using a focused, scanning ns-pulsed Ytterbium fiber laser at 532nm wavelength. The deposition process is initiated by a photo induced reaction of a CuSO4-based liquid precursor in contact with the backside of the substrate. The obtained metallic copper deposits are crystalline, stable under ambient conditions and have a conductivity in the same order of magnitude as bulk copper

A novel Model for the Mechanism of Laser-Induced Back Side Wet Etching in Aqueous Cu Solutions using ns Pulses at 1064nm

Laser induced back side wet etching has shown to be a promising tool for the micro-structuring of transparent materials. Detailed studies have been performed using UV excimer laser sources, aromatic hydrocarbon and liquid metal absorbers. Only little work is reported however using aqueous Cu solutions as absorbers and ns laser pulses at 1064 nm wavelength. We present a novel model for this specific setup. Our experiments indicate that physisorbed Cu2+ ions at the polar glass surface absorb the laser light. This leads to local thermal stresses in the glass and subsequent micro-ablation

Micro structuring of transparent materials with NIR ns-laser pulses

A current challenge in laser processing is high precision micromachining of transparent materials, e.g. to manufacture micro-optical elements. This can be achieved amongst others by using laser induced backside wet etching. Research has been done by several groups in the last years. Most of the published results were obtained by using UV excimer lasers. Our approach deals withthe implementation of the technique for NIR laser sources. We investigated the effects of different pulse widths and repetitionrates on laser induced back side wet etching for 1064nm wavelength and for different absorbers

Loss of CCDC6 Affects Cell Cycle through Impaired Intra-S-Phase Checkpoint Control

In most cancers harboring Ccdc6 gene rearrangements, like papillary thyroid tumors or myeloproliferative disorders, the product of the normal allele is supposed to be functionally impaired or absent. To address the consequence of the loss of CCDC6 expression, we applied lentiviral shRNA in several cell lines. Loss of CCDC6 resulted in increased cell death with clear shortening of the S phase transition of the cell cycle. Upon exposure to etoposide, the cells lacking CCDC6 did not achieve S-phase accumulation. In the absence of CCDC6 and in the presence of genotoxic stress, like etoposide treatment or UV irradiation, increased accumulation of DNA damage was observed, as indicated by a significant increase of pH2Ax Ser139. 14-3-3σ, a major cell cycle regulator, was down-regulated in CCDC6 lacking cells, regardless of genotoxic stress. Interestingly, in the absence of CCDC6, the well-known genotoxic stress-induced cytoplasmic sequestration of the S-phase checkpoint CDC25C phosphatase did not occur. These observations suggest that CCDC6 plays a key role in cell cycle control, maintenance of genomic stability and cell survival and provide a rational of how disruption of CCDC6 normal function contributes to malignancy

Measuring Optical Properties On Rough And Liquid Metal Surfaces

For understanding and optimizing laser processing of metals and alloys the optical properties, especially the absorption of the work piece in function of the temperature up to the liquid phase have to be known [1]. There are several approaches to extend the Drude-Model [2] for optical properties of metal to temperature dependence [3, 4, 5]. However, a verification of these models is difficult due to the lack of sufficient experimental data. Even though measuring optical properties with ellipsometry is well established, such measurements on metals and alloys at elevated temperatures up to the liquid state are very challenging. To collect the optical properties of different metals and alloys like Al, Ti, Ag, Cu and steel in the solid and liquid state a custom-made high-temperature ellipsometer was used. The instrument is also used to investigate the influence of curved and rough surfaces which may occur due to the heating of the samples during the ellipsometric measurements