F. Gahbauer

Accelerator testing of the general antiparticle spectrometer, a novel approach to indirect dark matter detection

We report on recent accelerator testing of a prototype general antiparticle spectrometer (GAPS). GAPS uses a novel approach for indirect dark matter searches that exploits the antideuterons produced in neutralino–neutralino annihilations. GAPS captures these antideuterons into a target with the subsequent formation of exotic atoms. These exotic atoms decay with the emission of x-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. This signature uniquely characterizes the antideuterons. Preliminary analysis of data from a prototype GAPS in an antiproton beam at the KEK accelerator in Japan has confirmed the multiple x-ray/pion star topology and indicated x-ray yields consistent with prior expectations. Moreover, our success in utilizing solid rather than gas targets represents a significant simplification over our original approach and offers potential gains in sensitivity through reduced dead mass in the target area.

Composition of Primary Cosmic-Ray Nuclei at High Energies

The TRACER instrument (Transition Radiation Array for Cosmic Energetic Radiation) has been developed for direct measurements of the heavier primary cosmic-ray nuclei at high energies. The instrument had a successful long-duration balloon flight in Antarctica in 2003. The detector system and measurement process are described, details of the data analysis are discussed, and the individual energy spectra of the elements O, Ne, Mg, Si, S, Ar, Ca, and Fe (nuclear charge Z = 8-26) are presented. The large geometric factor of TRACER and the use of a transition radiation detector make it possible to determine the spectra up to energies in excess of 1014 eV per particle. A power-law fit to the individual energy spectra above 20 GeV amu−1 exhibits nearly the same spectral index (2.65 ± 0.05) for all elements, without noticeable dependence on the elemental charge Z.

A NEW MEASUREMENT OF THE INTENSITIES OF THE HEAVY PRIMARY COSMIC-RAY NUCLEI AROUND 1 TeV amu 1

We describe a new measurement of the intensities of the heavy primary cosmic-ray nuclei O, Ne, Mg, Si, and Fe from 10 GeV amu-1 to energies beyond 1 TeV amu-1. The measurement was conducted in 1999 during a 1 day test flight of the Transition Radiation Array for Cosmic Energetic Radiation (TRACER), a new cosmic-ray telescope designed for long-duration balloon flights. TRACER uses an array of thin-walled single-wire proportional tubes to determine the particle Lorentz factor from measurements of specific ionization and transition radiation. The nuclear charge is obtained with plastic scintillators, and low-energy background is identified with an acrylic Cerenkov counter. The results of this observation are consistent with previous measurements in this energy region. The current statistical limitations should be greatly improved with the planned long-duration exposure of TRACER.

The pGAPS experiment: an engineering balloon flight of prototype GAPS

The General Anti-Particle Spectrometer (GAPS) project is being carried out to search for primary cosmic-ray antiparticles especially for antideuterons produced by cold dark matter. GAPS plans to realize the science observation by Antarctic long duration balloon flights in the late 2010s. In preparation for the Antarctic science flights, an engineering balloon flight using a prototype of the GAPS instrument, “pGAPS”, was successfully carried out in June 2012 in Japan to verify the basic performance of each GAPS subsystem. The outline of the pGAPS flight campaign is briefly reported.

The flight of the GAPS prototype experiment

Abstract The General AntiParticle Spectrometer experiment (GAPS) is foreseen to carry out a dark matter search using low-energy cosmic ray antideuterons at stratospheric altitudes with a novel detection approach. A prototype flight from Taiki, Japan was carried out in June 2012 to prove the performance of the GAPS instrument subsystems (Lithium-drifted Silicon tracker and time-of-flight) and the thermal cooling concept as well as to measure background levels. The flight was a success and the stable flight operation of the GAPS detector concept was proven. During the flight about 10 6 charged particle triggers were recorded, extensive X-ray calibrations of the individual tracker modules were performed by using an onboard X-ray tube, and the background level of atmospheric and cosmic X-rays was measured. The behavior of the tracker performance as a function of temperature was investigated. The tracks of charged particle events were reconstructed and used to study the tracking resolution, the detection efficiency of the tracker, and coherent X-ray backgrounds. A timing calibration of the time-of-flight subsystem was performed to measure the particle velocity. The flux as a function of flight altitude and as a function of velocity was extracted taking into account systematic instrumental effects. The developed analysis techniques will form the basis for future flights.

A Measurement of Atomic X-ray Yields in Exotic Atoms and Implications for an Antideuteron-Based Dark Matter Search

The General AntiParticle Spectrometer (GAPS) is a novel approach for the indirect dark matter search that exploits cosmic antideuterons. GAPS utilizes a distinctive detection method using atomic X-rays and charged particles from the exotic atom as well as the timing, stopping range and dE/dX energy deposit of the incoming particle, which provides excellent antideuteron identification. In anticipation of a future balloon experiment, an accelerator test was conducted in 2004 and 2005 at KEK, Japan, in order to prove the concept and to precisely measure the X-ray yields of antiprotonic exotic atoms formed with di erent target materials [1]. The X-ray yields of the exotic atoms with Al and S targets were obtained as 75%, which are higher than were previously assumed in [2]. A simple, but comprehensive cascade model has been developed not only to evaluate the measurement results but also to predict the X-ray yields of the exotic atoms formed with any materials in the GAPS instrument. The cascade model is extendable to any kind of exotic atom (any negatively charged cascading particles with any target materials), and it was compared and validated with other experimental data and cascade models for muonic and antiprotonic exotic atoms. The X-ray yields of the antideuteronic exotic atoms are predicted with a simple cascade model and the sensitivity for the GAPS antideuteron search was estimated for the proposed long duration balloon program [3], which suggests that GAPS has a strong potential to detect antideuterons as a dark matter signature. A GAPS prototype flight (pGAPS) was launched successfully from the JAXA/ISAS balloon facility in Hokkaido, Japan in summer 2012 [4, 5] and a proposed GAPS science flight is to fly from Antarctica in the austral summer of 2017-2018.

Antideuterons as an indirect dark matter signature: design and preparation for a balloon-born GAPS experiment

The General Antiparticle Spectrometer (GAPS) exploits low energy antideuterons produced in neutralino-neutralino annihilations as an indirect dark matter (DM) signature that is effectively free from background. When an antiparticle is captured by a target material, it forms an exotic atom in an excited state which quickly decays by emitting X-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. We have successfully demonstrated the GAPS method in an accelerator environment and are currently planning a prototype flight from Japan for 2009. This will lead to a long duration balloon (LDB) mission that will complement existing and planned direct DM searches as well as other indirect techniques, probing a different, and often unique, region of parameter space in a variety of proposed DM models. Planes of coarsely pixellated Si(Li) detectors form the heart of the GAPS flight detector, providing both high X-ray energy resolution and good particle tracking. We will describe the proto-flight mission that will verify the performance of our Si(Li) detectors and cooling system in a flight-like configuration. We also will outline the LDB science payload design.

Longitudinal spin-relaxation in nitrogen-vacancy centers in electron irradiated diamond

We present systematic measurements of longitudinal relaxation rates (

F-resolved magneto-optical resonances in the D1 excitation of cesium: Experiment and theory

1/T_1

A new detector for the measurement of the energy spectrum of cosmic ray nuclei in the TeV region

) of spin polarization in the ground state of the nitrogen-vacancy (NV