34 research outputs found
Measurement of the Spin-Dependence of the pbar-p Interaction at the AD-Ring
We propose to use an internal polarized hydrogen storage cell gas target in
the AD ring to determine for the first time the two total spin-dependent pbar-p
cross sections sigma_1 and sigma_2 at antiproton beam energies in the range
from 50 to 450 MeV. The data obtained are of interest by themselves for the
general theory of pbar-p interactions since they will provide a first
experimental constraint of the spin-spin dependence of the nucleon-antinucleon
potential in the energy range of interest. In addition, measurements of the
polarization buildup of stored antiprotons are required to define the optimum
parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to
feed a double-polarized asymmetric pbar-p collider with polarized antiprotons.
Such a machine has recently been proposed by the PAX collaboration for the new
Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany.
The availability of an intense stored beam of polarized antiprotons will
provide access to a wealth of single- and double-spin observables, thereby
opening a new window on QCD spin physics.Comment: 51 pages, 23 figures, proposal submitted to the SPS committee of CER
Controlling Cherenkov angles with resonance transition radiation
Cherenkov radiation provides a valuable way to identify high energy particles
in a wide momentum range, through the relation between the particle velocity
and the Cherenkov angle. However, since the Cherenkov angle depends only on
material's permittivity, the material unavoidably sets a fundamental limit to
the momentum coverage and sensitivity of Cherenkov detectors. For example, Ring
Imaging Cherenkov detectors must employ materials transparent to the frequency
of interest as well as possessing permittivities close to unity to identify
particles in the multi GeV range, and thus are often limited to large gas
chambers. It would be extremely important albeit challenging to lift this
fundamental limit and control Cherenkov angles as preferred. Here we propose a
new mechanism that uses constructive interference of resonance transition
radiation from photonic crystals to generate both forward and backward
Cherenkov radiation. This mechanism can control Cherenkov angles in a flexible
way with high sensitivity to any desired range of velocities. Photonic crystals
thus overcome the severe material limit for Cherenkov detectors, enabling the
use of transparent materials with arbitrary values of permittivity, and provide
a promising option suited for identification of particles at high energy with
enhanced sensitivity.Comment: There are 16 pages and 4 figures for the manuscript. Supplementary
information with 18 pages and 5 figures, appended at the end of the file with
the manuscript. Source files in Word format converted to PDF. Submitted to
Nature Physic
Past Achievements and Future Challenges in 3D Photonic Metamaterials
Photonic metamaterials are man-made structures composed of tailored micro- or
nanostructured metallo-dielectric sub-wavelength building blocks that are
densely packed into an effective material. This deceptively simple, yet
powerful, truly revolutionary concept allows for achieving novel, unusual, and
sometimes even unheard-of optical properties, such as magnetism at optical
frequencies, negative refractive indices, large positive refractive indices,
zero reflection via impedance matching, perfect absorption, giant circular
dichroism, or enhanced nonlinear optical properties. Possible applications of
metamaterials comprise ultrahigh-resolution imaging systems, compact
polarization optics, and cloaking devices. This review describes the
experimental progress recently made fabricating three-dimensional metamaterial
structures and discusses some remaining future challenges
Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility
The search for 4He-eta bound states was performed with the WASA-at-COSY
facility via the measurement of the excitation function for the dd->3He n pi0
and dd->3He p pi- processes. The beam momentum was varied continuously between
2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd->4He
eta reaction ranging from Q=-70 MeV to Q=30 MeV. The luminosity was determined
based on the dd->3He n reaction and quasi-free proton-proton scattering via
dd->pp n_spectator n_spectator reactions. The excitation functions determined
independently for the measured reactions do not reveal a structure which could
be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the
total cross sections for the bound state production and decay in
dd->(4He-eta)_bound->3He n pi0 and dd->(4He-eta)_bound->3He p pi- processes
were determined taking into account the isospin relation between both the
channels considered. The results of the analysis depend on the assumptions of
the N* momentum distribution in the anticipated mesic-4He. Assuming as in the
previous works, that this is identical with the distribution of nucleons bound
with 20 MeV in 4He, we determined that (for the mesic bound state width in the
range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about
3 nb and about 6 nb for npi0 and ppi- channels, respectively. However, based on
the recent theoretical findings of the N*(1535) momentum distribution in the
N*-3He nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector
acceptance decreases and hence the corresponding upper limits are 5 nb and 10
nb for npi0 and ppi- channels respectively.Comment: This article will be submitted to JHE
Search for the eta-mesic 4He with WASA-at-COSY detector
An exclusive measurement of the excitation function for the dd->3Heppi-
reaction was performed at the Cooler Synchrotron COSY-Juelich with the
WASA-at-COSY detection system. The data were taken during a slow acceleration
of the beam from 2.185 GeV/c to 2.400 GeV/c crossing the kinematic threshold
for the eta meson production in the dd->4He-eta reaction at 2.336 GeV/c. The
corresponding excess energy with respect to the 4He-eta system varied from
-51.4MeV to 22MeV. The integrated luminosity in the experiment was determined
using the dd->3Hen reaction. The shape of the excitation function for the
dd->3Heppi- was examined. No signal of the 4He-eta bound state was observed. An
upper limit for the cross-section for the bound state formation and decay in
the process dd->(4He-eta)bound->3Heppi- was determined on the 90% confidence
level and it varies from 20nb to 27nb for the bound state width ranging from
5MeV to 35MeV, respectively.Comment: 8 pages, 9 figure
Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets
This document is the Technical Design Report covering the two large
spectrometer magnets of the PANDA detector set-up. It shows the conceptual
design of the magnets and their anticipated performance. It precedes the tender
and procurement of the magnets and, hence, is subject to possible modifications
arising during this process.Comment: 10 pages, 14MB, accepted by FAIR STI in May 2009, editors: Inti
Lehmann (chair), Andrea Bersani, Yuri Lobanov, Jost Luehning, Jerzy Smyrski,
Technical Coordiantor: Lars Schmitt, Bernd Lewandowski (deputy),
Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy
Anapole nanolasers for mode-locking and ultrafast pulse generation
Nanophotonics is a rapidly developing field of research with many suggestions for a design of nanoantennas, sensors and miniature metadevices. Despite many proposals for passive nanophotonic devices, the efficient coupling of light to nanoscale optical structures remains a major challenge. In this article, we propose a nanoscale laser based on a tightly confined anapole mode. By harnessing the non-radiating nature of the anapole state, we show how to engineer nanolasers based on InGaAs nanodisks as on-chip sources with unique optical properties. Leveraging on the near-field character of anapole modes, we demonstrate a spontaneously polarized nanolaser able to couple light into waveguide channels with four orders of magnitude intensity than classical nanolasers, as well as the generation of ultrafast (of 100 fs) pulses via spontaneous mode locking of several anapoles. Anapole nanolasers offer an attractive platform for monolithically integrated, silicon photonics sources for advanced and efficient nanoscale circuitry
Physics Performance Report for PANDA: Strong Interaction Studies with Antiprotons
To study fundamental questions of hadron and nuclear physics in interactions
of antiprotons with nucleons and nuclei, the universal PANDA detector will be
built. Gluonic excitations, the physics of strange and charm quarks and nucleon
structure studies will be performed with unprecedented accuracy thereby
allowing high-precision tests of the strong interaction. The proposed PANDA
detector is a state-of-the art internal target detector at the HESR at FAIR
allowing the detection and identification of neutral and charged particles
generated within the relevant angular and energy range. This report presents a
summary of the physics accessible at PANDA and what performance can be
expected.Comment: 216 page