7,963 research outputs found
Model Independent Searches In ep Collisions
The high energy program of the HERA collider ended in March 2007. In total
the H1 and ZEUS experiments collected an integrated luminosity of about 1
fb. Recent results of model independent searches for new physics from
both experiments are presented. Specifically, studies of the events with an
isolated lepton and missing transverse momentum and multi-lepton topologies,
where H1 and ZEUS data are combined, and a general signature based search are
discussed.Comment: 6 pages, 5 figures; To appear in the proceedings of the XLIIIth
Rencontres de Moriond on Electroweak Interactions and Unified Theories, La
Thuile, Aosta Valley (Italy), March 1-8, 200
H1 Diffractive Structure Functions Measurement from new data
New measurements of the reduced cross section for the
diffractive process in the kinematic domain
GeV, and \xpom<0.1 are presented. Data events
recorded by the H1 detector during the years 1999--2000 and 2004 have been
used, corresponding to a total integrated luminosity of 68 pb. The
measurements are derived in the same range as previous H1 data, namely GeV and GeV. Two different analysis methods, rapidity gap
and , are used and similar results are obtained in the kinematic domain of
overlap. Finally, together with previous data, the diffractive structure
function measurements are analysed with a model based on the dipole formulation
of diffractive scattering. It is found to give a very good description of the
data over the whole kinematic range.Comment: 4 pages, 4 figure; To appear in the proceedings of 14th International
Workshop on Deep Inelastic Scattering (DIS 2006), Tsukuba, Japan, 20-24 Apr
200
Single-Proton Removal Reaction Study of 16B
The low-lying level structure of the unbound system B has been
investigated via single-proton removal from a 35 MeV/nucleon C beam. The
coincident detection of the beam velocity B fragment and neutron allowed
the relative energy of the in-flight decay of B to be reconstructed. The
resulting spectrum exhibited a narrow peak some 85 keV above threshold. It is
argued that this feature corresponds to a very narrow (100 keV)
resonance, or an unresolved multiplet, with a dominant + configuration which decays by d-wave neutron
emission.Comment: 16 pages, 5 figures, 1 table, submitted to Phys. Lett.
Photon recycling in Fabry-Perot micro-cavities based on SiN waveguides
We present a numerical analysis and preliminary experimental results on
one-dimensional Fabry-Perot micro-cavities in SiN waveguides. The
Fabry-Perot micro-cavities are formed by two distributed Bragg reflectors
separated by a straight portion of waveguide. The Bragg reflectors are composed
by a few air slits produced within the SiN waveguides. In order to
increase the quality factor of the micro-cavities, we have minimized, with a
multiparametric optimization tool, the insertion loss of the reflectors by
varying the length of their first periods (those facing the cavity). To explain
the simulation results the coupling of the fundamental waveguide mode with
radiative modes in the Fabry-Perot micro-cavities is needed. This effect is
described as a recycling of radiative modes in the waveguide. To support the
modelling, preliminary experimental results of micro-cavities in SiN
waveguides realized with Focused Ion Beam technique are reported.Comment: 5 pages, 5 figure
Extended sudden approximation model for high-energy nucleon removal reactions
A model based on the sudden approximation has been developed to describe high
energy single nucleon removal reactions. Within this approach, which takes as
its starting point the formalism of Hansen \cite{Anne2}, the nucleon-removal
cross section and the full 3-dimensional momentum distributions of the core
fragments including absorption, diffraction, Coulomb and nuclear-Coulomb
interference amplitudes, have been calculated. The Coulomb breakup has been
treated to all orders for the dipole interaction. The model has been compared
to experimental data for a range of light, neutron-rich psd-shell nuclei. Good
agreement was found for both the inclusive cross sections and momentum
distributions. In the case of C, comparison is also made with the
results of calculations using the transfer-to-the-continuum model. The
calculated 3-dimensional momentum distributions exhibit longitudinal and
transverse momentum components that are strongly coupled by the reaction for
s-wave states, whilst no such effect is apparent for d-waves. Incomplete
detection of transverse momenta arising fromlimited experimental acceptances
thus leads to a narrowing of the longitudinal distributions for nuclei with
significant s-wave valence neutron configurations, as confirmed by the data.
Asymmetries in the longitudinal momentum distributions attributed to
diffractive dissociation are also explored.Comment: 16 figures, submitted to Phys. Rev.
Near-field spectroscopy of low-loss waveguide integrated microcavities
International audienceA scanning near-field spectroscopy method is used to observe loss reduction and Q-factor enhancement due to transverse-mode profile matching within photonic-crystal microcavities. Near-field measurements performed directly on cavity modes are compared with three-dimensional calculations and quantitative agreement is observed. (c) 2006 American Institute of Physics
One-neutron removal reactions on neutron-rich psd-shell nuclei
A systematic study of high energy, one-neutron removal reactions on 23
neutron-rich, psd--shell nuclei (Z=5-9, A=12-25) has been carried out. The
longitudinal momentum distributions of the core fragments and corresponding
single-neutron removal cross sections are reported for reactions on a carbon
target. Extended Glauber model calculations, weighted by the spectroscopic
factors obtained from shell model calculations, are compared to the
experimental results. Conclusions are drawn regarding the use of such reactions
as a spectroscopic tool and spin-parity assignments are proposed for 15B, 17C,
19-21N, 21,23O, 23-25F. The nature of the weakly bound systems 14B and 15,17C
is discussed.Comment: 11 pages + 2 figure
Asymptotic normalization coefficient of ^{8}B from breakup reactions and the S_{17} astrophysical factor
We show that asymptotic normalization coefficients (ANC) can be extracted
from one nucleon breakup reactions of loosely bound nuclei at 30-300 MeV/u. In
particular, the breakup of ^{8}B is described in terms of an extended Glauber
model. The 8B ANC extracted for the ground state of this nucleus from breakup
data at several energies and on different targets, C^2 = 0.450+/-0.039} fm^-1,
leads to the astrophysical factor S_{17}(0)= 17.4+/-1.5 eVb for the key
reaction for solar neutrino production 7Be(p,gamma)8B. The procedure described
here is more general, providing an indirect method to determine reaction rates
of astrophysical interest with beams of loosely bound radioactive nuclei.Comment: 4 pages, RevTex, 3 figures revised version to appear in Phys Rev Let
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