8,842 research outputs found
Searches for long-lived charged particles with the ATLAS experiment
These conference proceedings for PLHC 2011 in Perugia, Italy summarize the
results from two searches for long-lived charged particles using 34-37 pb-1.
The searches are based on direct detection and exploits ionization energy loss
and time-of-flight measurements to separate slow-moving signal particles from
the Standard Model backgrounds. The observations are in all cases consistent
with the background-only hypotheses and limits are presented for long-lived
squarks, gluinos and sleptons.Comment: 2 pages, 2 figures, proceedings for Physics at the LHC in Perugia,
Italy, June 6-11, 201
\gamma-rays from starburst galaxies
In this paper the current status of \gamma-ray observations of starburst
galaxies from hundreds of MeV up to TeV energies with space-based instruments
and ground-based Imaging Atmospheric Cherenkov Telescopes (IACTs) is
summarised. The properties of the high-energy (HE; 100 MeV < E < 100 GeV) and
very-high-energy (VHE; E > 100 GeV) emission of the archetypical starburst
galaxies M 82 and NGC 253 are discussed and put into context with the HE
\gamma-ray emission detected from other galaxies that show enhanced
star-formation activity such as NGC 4945 and NGC 1068. Finally, prospects to
study the star-formation - \gamma-ray emission connection from Galactic systems
to entire galaxies with the forthcoming Cherenkov Telescope Array (CTA) are
outlined.Comment: 8 pages, 2 figures, solicited talk, to be published in High Energy
Gamma-Ray Astronomy (eds. F. Aharonian, W. Hofmann, F. Rieger) the
proceedings of the 5th Heidelberg international symposium on high energy
gamma-ray astronom
Majorana fermions coupled to electromagnetic radiation
We consider a voltage-biased Josephson junction between two nanowires hosting
Majorana zero modes which occur as topological protected zero-energy
excitations at the junction. We show that two Majorana fermions localized at
the junction, even though being neutral particles, interact with the
electromagnetic field and generate coherent radiation similar to the
conventional Josephson radiation. Within a semiclassical analysis of the
radiation field, we find that the optical phase gets locked to the
superconducting phase difference and that the radiation is emitted at half the
Josephson frequency. In order to confirm the coherence of the radiation, we
study correlations of the radiation emitted by two spatially-separated
junctions in a d.c.-SQUID geometry taking into account decoherence due to
spontaneous state-switches as well as due to quasi-particle poisoning.Comment: 18 pages, 4 figure
Quantum Hole Digging in Magnetic Molecular Clusters
Below 360 mK, Fe8 magnetic molecular clusters are in the pure quantum
relaxation regime. We showed recently that the predicted ``square-root time''
relaxation is obeyed, allowing us to develop a new method for watching the
evolution of the distribution of molecular spin states in the sample. We
measured the distribution P(H) of molecules which are in resonance at the
applied field H. Tunnelling initially causes rapid transitions of molecules,
thereby ``digging a hole'' in P(H). For small initial magnetisation values, the
hole width shows an intrinsic broadening which may be due to nuclear spins. We
present here hole digging measurements in the thermal activated regime which
may allow to study the effect of spin-phonon coupling.Comment: 3 pages, 2 figures, conference proceedings of LT22 (Helsinki,
Finland, August 4-11, 1999
On the expected -ray emission from nearby flaring stars
Stellar flares have been extensively studied in soft X-rays (SXR) by
basically every X-ray mission. Hard X-ray (HXR) emission from stellar
superflares, however, have only been detected from a handful of objects over
the past years. One very extreme event was the superflare from the young
M-dwarf DG CVn binary star system, which triggered Swift/BAT as if it was a
-ray burst (GRB). In this work, we estimate the expected -ray
emission from DG CVn and the most extreme stellar flares by extrapolating from
solar flares based on measured solar energetic particles (SEPs), as well as
thermal and non-thermal emission properties. We find that ions are plausibly
accelerated in stellar superflares to 100 GeV energies, and possibly up to TeV
energies in the associated coronal mass ejections. The corresponding
-decay -ray emission could be detectable from stellar
superflares with ground-based -ray telescopes. On the other hand, the
detection of -ray emission implies particle densities high enough that
ions suffer significant losses due to inelastic proton-proton scattering. The
next-generation Cherenkov Telescope Array (CTA) should be able to probe
superflares from M-dwarfs in the solar neighbourhood and constrain the energy
in interacting cosmic rays and/or their maximum energy. The detection of
-ray emission from stellar flares would open a new window for the study
of stellar physics, the underlying physical processes in flares and their
impact on habitability of planetary systems.Comment: 8 pages, 3 figures, 2 table
Measurement-induced entanglement of two transmon qubits by a single photon
On-demand creation of entanglement between distant qubits is a necessary
ingredient for distributed quantum computation. We propose an entanglement
scheme that allows for single-shot deterministic entanglement creation by
detecting a single photon passing through a Mach-Zehnder interferometer with
one transmon qubit in each arm. The entanglement production essentially relies
on the fact that superconducting microwave structures allow to achieve strong
coupling between the qubit and the photon. By detecting the photon via a photon
counter, a parity measurement is implemented and the wave function of the two
qubits is projected onto a maximally entangled state. Most importantly, the
entanglement generation is heralded such that our protocol is not susceptible
to photon loss due to the indivisible nature of single photons.Comment: 18 pages, 2 figures; to be published in NJ
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