229 research outputs found
A Simple Procedure for the Calculation of the Shake-Off Ratio of Double-To- Single Ionization of a Helium-Like Ion by Photoabsorption of a High- Energy Photon
Back-to-back emission of the electrons in double photoionization of helium
We calculate the double differential distributions and distributions in
recoil momenta for the high energy non-relativistic double photoionization of
helium. We show that the results of recent experiments is the pioneering
experimental manifestation of the quasifree mechanism for the double
photoionization, predicted long ago in our papers. This mechanism provides a
surplus in distribution over the recoil momenta at small values of the latter,
corresponding to nearly "back-to-back" emission of the electrons. Also in
agreement with previous analysis the surplus is due to the quadrupole terms of
the photon-electron interaction. We present the characteristic angular
distribution for the "back-to-back" electron emission. The confirmation of the
quasifree mechanism opens a new area of exiting experiments, which are expected
to increase our understanding of the electron dynamics and of the bound states
structure. The results of this Letter along with the recent experiments open a
new field for studies of two-electron ionization not only by photons but by
other projectiles, e.g. by fast electrons or heavy ions.Comment: 10 pages, 2 figure
Few Body Reserch - Summary
Few-body research history, achievements, current development and challenges
are presented.Comment: 21 pages, 2 tables, Summary talk at 18th International IUPAP
Conference on Few-Body Problems in Physics August 21-26. 2006 Santos SP
Brazil; to be published in Nuclear Physic
MAGIC Upper Limits for two Milagro-detected, Bright Fermi Sources in the Region of SNR G65.1+0.6
We report on the observation of the region around supernova remnant G65.1+0.6
with the stand-alone MAGIC-I telescope. This region hosts the two bright GeV
gamma-ray sources 1FGL J1954.3+2836 and 1FGL J1958.6+2845. They are identified
as GeV pulsars and both have a possible counterpart detected at about 35 TeV by
the Milagro observatory. MAGIC collected 25.5 hours of good quality data, and
found no significant emission in the range around 1 TeV. We therefore report
differential flux upper limits, assuming the emission to be point-like (<0.1
deg) or within a radius of 0.3 deg. In the point-like scenario, the flux limits
around 1 TeV are at the level of 3 % and 2 % of the Crab Nebula flux, for the
two sources respectively. This implies that the Milagro emission is either
extended over a much larger area than our point spread function, or it must be
peaked at energies beyond 1 TeV, resulting in a photon index harder than 2.2 in
the TeV band.Comment: 8 pages, 3 figures, 1 tabl
Simultaneous multi-frequency observation of the unknown redshift blazar PG 1553+113 in March-April 2008
The blazar PG 1553+113 is a well known TeV gamma-ray emitter. In this paper,
we determine its spectral energy distribution using simultaneous
multi-frequency data in order to study its emission processes. An extensive
campaign was carried out between March and April 2008, where optical, X-ray,
high-energy (HE) gamma-ray, and very-high-energy (VHE) gamma-ray data were
obtained with the KVA, Abastumani, REM, RossiXTE/ASM, AGILE and MAGIC
telescopes, respectively. This is the first simultaneous broad-band (i.e.,
HE+VHE) gamma-ray observation, though AGILE did not detect the source. We
combine data to derive source's spectral energy distribution and interpret its
double peaked shape within the framework of a synchrotron self compton modelComment: 5 pages, 2 figures, publishe
Study of the reaction e^{+}e^{-} -->J/psi\pi^{+}\pi^{-} via initial-state radiation at BaBar
We study the process with
initial-state-radiation events produced at the PEP-II asymmetric-energy
collider. The data were recorded with the BaBar detector at center-of-mass
energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454
. We investigate the mass
distribution in the region from 3.5 to 5.5 . Below 3.7
the signal dominates, and above 4
there is a significant peak due to the Y(4260). A fit to
the data in the range 3.74 -- 5.50 yields a mass value
(stat) (syst) and a width value (stat)(syst) for this state. We do not
confirm the report from the Belle collaboration of a broad structure at 4.01
. In addition, we investigate the system
which results from Y(4260) decay
Revised Strategic Research Agenda for Social Sciences and Humanities in Radiation Protection
This document describes the research priorities and the Strategic Research Agenda (SRA) for Social Sciences and Humanities (SSH) in radiation protection for the next 20 years. It also reports on the results of a first gap analysis.
The SSH SRA is a living document, under constant development through the engagement of the SSH community in radiation protection field and other stakeholders, especially technical and research platforms. To this end, the SSH community in radiation protection field will structure and enhance dialogue at the European level among the different stakeholders, fostering the sharing of knowledge and information among various disciplines working on aspects of radiation protection and identify the SSH research needs in the field of radiation protection. The objective of Strategic Research Agenda (SRA) for Social Sciences and Humanities (SSH) in radiation protection is to contribute towards improvement of the Radiation Protection (RP) system by coordinating European SSH research in the field of radiation protection; supporting education and training; knowledge management and sharing; and identifying SSH state of the art across domains. It is only by enabling SSH research to play a fuller and stronger role through a coordinated SRA mechanism that societal perspectives on research relating to radiation protection will be realised.
The SSH SRA has been developed through a broad stakeholder engagement process. The research topics to be included in the SSH SRA have been collected through various activities carried out in the H2020 projects CONCERT and the FP7 projects OPERRA, PREPARE and EAGLE, notably the RICOMET 2015, 2016 an RICOMET 2017 conferences and Symposium on Ethics of Environmental Health, as well as in dialogues with members of the radiation protection platforms, carried out in a context of the CONCERT 2.6 task group. These research topics have been prioritised for the first time at the Radiation Protection Week in Oxford (19-23 September 2016) with task 2.6 members, SSH community and platforms, and further debated upon at the RICOMET Conference 2017 (June 27th to 29th, Vienna) with a large audience. The version summarised in this report is the most recent revision on of the SSH SRA (D2.8 and D2.10)
Statistics of VHE γ -rays in temporal association with radio giant pulses from the Crab pulsar
Aims. The aim of this study is to search for evidence of a common emission engine between radio giant pulses (GPs) and very-high-energy (VHE, E > 100 GeV) γ-rays from the Crab pulsar. Methods. We performed 16 h of simultaneous observations of the Crab pulsar at 1.4 GHz with the Effelsberg radio telescope and the Westerbork Synthesis Radio Telescope (WSRT), and at energies above 60 GeV we used the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes. We searched for a statistical correlation between the radio and VHE γ-ray emission with search windows of different lengths and different time lags to the arrival times of a radio GP. A dedicated search for an enhancement in the number of VHE γ-rays correlated with the occurrence of radio GPs was carried out separately for the P1 and P2 phase ranges, respectively. Results. In the radio data sample, 99444 radio GPs were detected. We find no significant correlation between the GPs and VHE photons in any of the search windows. Depending on phase cuts and the chosen search windows, we find upper limits at a 95% confidence level on an increase in VHE γ-ray events correlated with radio GPs between 7% and 61% of the average Crab pulsar VHE flux for the P1 and P2 phase ranges, respectively. This puts upper limits on the flux increase during a radio GP between 12% and 2900% of the pulsed VHE flux, depending on the search window duration and phase cuts. This is the most stringent upper limit on a correlation between γ-ray emission and radio GPs reported so far
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