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G. Wolf

Publications and source records attributed to G. Wolf.

11 recordsLinked to original sources
arXiv2013

Temperature dependence of the switching field distributions in all-perpendicular spin-valve nanopillars

We present temperature dependent switching measurements of the Co/Ni multilayered free element of 75 nm diameter spin-valve nanopillars. Angular dependent hysteresis measurements as well as switching field measurements taken at low temperature are in agreement with a model of thermal activation over a perpendicular anisotropy barrier. However, the statistics of switching (mean switching field and switching variance) from 20 K up to 400 K are in disagreement with a Néel-Brown model that assumes a temperature independent barrier height and anisotropy field. We introduce a modified Néel-Brown model thats fit the experimental data in which we take a $T^{3/2}$ dependence to the barrier height and the anisotropy field due to the temperature dependent magnetization and anisotropy energy.

cond-mat.mes-hall↗
arXiv2012

Mode conversion by symmetry breaking of propagating spin waves

We study spin-wave transport in a microstructured Ni81Fe19 waveguide exhibiting broken translational symmetry. We observe the conversion of a beam profile composed of symmetric spin-wave width modes with odd numbers of antinodes n=1,3,... into a mixed set of symmetric and asymmetric modes. Due to the spatial homogeneity of the exciting field along the used microstrip antenna, quantized spin-wave modes with an even number n of antinodes across the stripe's width cannot be directly excited. We show that a break in translational symmetry may result in a partial conversion of even spin-wave waveguide modes

cond-mat.mes-hall↗
arXiv2009

Review of High Energy Diffraction in Real and Virtual Photon Proton scattering at HERA

The electron-proton collider HERA at DESY opened the door for the study of diffraction in real and virtual photon-proton scattering at center-of-mass energies W up to 250 GeV and for large negative mass squared -Q^2 of the virtual photon up to Q^2 = 1600 GeV^2. At W = 220 GeV and Q^2 = 4 GeV^2, diffraction accounts for about 15% of the total virtual photon proton cross section decreasing to ~5% at Q^2 = 200 GeV^2. An overview of the results obtained by the experiments H1 and ZEUS on the production of neutral vectormesons and on inclusive diffraction up to the year 2008 is presented.

hep-ex↗
arXiv2007

Analysis of Dilepton Invariant Mass Spectrum in C+C at 2 and 1 AGeV

Recently the HADES collaboration has published the invariant mass spectrum of $e^+e^-$ pairs, dN/dM$_{e^+e^-}$, produced in C+C collisions at 2 AGeV. Using electromagnetic probes, one hopes to get in this experiment information on hadron properties at high density and temperature. Simulations show that firm conclusions on possible in-medium modifications of meson properties will only be possible when the elementary meson production cross sections, especially in the pn channel, as well as production cross sections of baryonic resonances are better known. Presently one can conclude that a) simulations overpredict by far the cross section at $M_{e^+e^-} \approx M_ω{^0}$ if free production cross sections are used and that b) the upper limit of the $η$ decay into $e^+e^-$ is smaller than the present upper limit of the Particle Data Group. This is the result of simulations using the Isospin Quantum Molecular Dynamics (IQMD) approach.

nucl-th↗
arXiv2000

From meson-nucleon scattering to vector mesons in nuclear matter

We employ meson-nucleon scattering data to deduce the properties of the low-mass vector mesons in nuclear matter, and present results for the $ρ$ and $ω$ in-medium spectral functions. The corresponding thermal emission rate for lepton pairs is also discussed.

nucl-th↗
arXiv1999

The ZEUS Forward Plug Calorimeter with Lead-Scintillator Plates and WLS Fiber Readout

A Forward Plug Calorimeter (FPC) for the ZEUS detector at HERA has been built as a shashlik lead-scintillator calorimeter with wave length shifter fiber readout. Before installation it was tested and calibrated using the X5 test beam facility of the SPS accelerator at CERN. Electron, muon and pion beams in the momentum range of 10 to 100 GeV/c were used. Results of these measurements are presented as well as a calibration monitoring system based on a $^{60}$Co source.

hep-ex↗
arXiv1998

Masses of hadrons in nuclei

We emphasize the central role played by the spectral function in the description of hadrons in matter and discuss the applicability of the quasiparticle concept to the propagation of hadrons in dense nuclear matter. Theoretical and experimental results relevant for the in medium properties of vector mesons and kaons are briefly reviewed. We also present novel results for the $ρ$ and $ω$ spectral functions in nuclear matter, deduced from a coupled channel analysis of pion-nucleon scattering data.

nucl-th↗
arXiv1997

Subthreshold K+ production in deuteron and alpha induced nuclear reactions

Double differential cross sections have been measured for pi+ and K+ emitted around midraidity in d+A and He+A collisions at a beam kinetic energy of 1.15 GeV/nucleon. The total pi+ yield increases by a factor of about 2 when using an alpha projectile instead of a deuteron whereas the K+ yield increases by a factor of about 4. According to transport calculations, the K+ enhancement depends both on the number of hadron-hadron collisions and on the energy available in those collisions: their center-of-mass energy increases with increasing number of projectile nucleons.

nucl-ex↗
arXiv1996

Higgs Physics at LEP2

In this report we review the prospects for Higgs physics at LEP2. The theoretical aspects and the phenomenology of Higgs particles are discussed within the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM). The experimental search techniques are described and the discovery limits for Higgs bosons in the LEP2 energy range are summarized. In addition, opportunities of detecting Higgs particles in non-minimal extensions of the SM and the MSSM are investigated.

hep-ph↗
arXiv1993

Alpha scattering and capture reactions in the A = 7 system at low energies

Differential cross sections for $^3$He-$α$ scattering were measured in the energy range up to 3 MeV. These data together with other available experimental results for $^3$He $+ α$ and $^3$H $+ α$ scattering were analyzed in the framework of the optical model using double-folded potentials. The optical potentials obtained were used to calculate the astrophysical S-factors of the capture reactions $^3$He$(α,γ)^7$Be and $^3$H$(α,γ)^7$Li, and the branching ratios for the transitions into the two final $^7$Be and $^7$Li bound states, respectively. For $^3$He$(α,γ)^7$Be excellent agreement between calculated and experimental data is obtained. For $^3$H$(α,γ)^7$Li a $S(0)$ value has been found which is a factor of about 1.5 larger than the adopted value. For both capture reactions a similar branching ratio of $R = σ(γ_1)/σ(γ_0) \approx 0.43$ has been obtained.

nucl-th↗