26 research outputs found
Energy flow calibration of LHCb ECAL
ECAL is a part of the LHCb calorimeter system consisting of more than 6000 individual readout cells. A good ECAL calibration is essential for overall detector performance. In this article one possible calibration method is described in details
Trade-off between quantum and thermal fluctuations in mirror coatings yields improved sensitivity of gravitational-wave interferometers
We propose a simple way to improve the laser gravitational-wave detectors
sensitivity by means of reduction of the number of reflective coating layers of
the core optics mirrors. This effects in the proportional decrease of the
coating thermal noise, the most notorious among the interferometers technical
noise sources. The price for this is the increased quantum noise, as well as
high requirements for the pump laser power and power at the beamsplitter.
However, as far as these processes depend differently on the coating thickness,
we demonstrate that a certain trade-off is possible, yielding a 20-30% gain
(for diverse gravitational wave signal types and interferometer
configurations), providing that feasible values of laser power and power on the
beamsplitter are assumed.Comment: 11 pages, 4 figures, 4 table
Cosmic Rays during BBN as Origin of Lithium Problem
There may be non-thermal cosmic rays during big-bang nucleosynthesis (BBN)
epoch (dubbed as BBNCRs). This paper investigated whether such BBNCRs can be
the origin of Lithium problem or not. It can be expected that BBNCRs flux will
be small in order to keep the success of standard BBN (SBBN). With favorable
assumptions on the BBNCR spectrum between 0.09 -- 4 MeV, our numerical
calculation showed that extra contributions from BBNCRs can account for the
Li abundance successfully. However Li abundance is only lifted an order
of magnitude, which is still much lower than the observed value. As the
deuteron abundance is very sensitive to the spectrum choice of BBNCRs, the
allowed parameter space for the spectrum is strictly constrained. We should
emphasize that the acceleration mechanism for BBNCRs in the early universe is
still an open question. For example, strong turbulent magnetic field is
probably the solution to the problem. Whether such a mechanism can provide the
required spectrum deserves further studies.Comment: 34 pages, 21 figures, published versio
Structure of the mirror nuclei Be and B in a microscopic cluster model
The structure of the mirror nuclei Be and B is studied in a
microscopic and three-cluster model
using a fully antisymmetrized 9-nucleon wave function. The two-nucleon
interaction includes central and spin-orbit components and the Coulomb
potential. The ground state of Be is obtained accurately with the
stochastic variational method, while several particle-unbound states of both
Be and B are investigated with the complex scaling method.The
calculation for Be supports the recent identification for the existence of
two broad states around 6.5 MeV, and predicts the and
states at about 4.5 MeV and 8 MeV, respectively. The
similarity of the calculated spectra of Be and B enables one to
identify unknown spins and parities of the B states. Available data on
electromagnetic moments and elastic electron scatterings are reproduced very
well. The enhancement of the 1 transition of the first excited state in
Be is well accounted for. The calculated density of Be is found to
reproduce the reaction cross section on a Carbon target. The analysis of the
beta decay of Li to Be clearly shows that the wave function of Be
must contain a small component that cannot be described by the simple model. This small component can be well accounted for by extending a
configuration space to include the distortion of the -particle to
and partitions.Comment: 24 page
Beam Test Results of the LHCb Electromagnetic Calorimeter.
The main properties of the LHCb electromagnetic calorimeter and a prototype of the monitoring system was studied at the X7 CERN test-beam facility. A dedicated MC simulation for light propagation in the scintillator tiles was developed and tuned with experimental data
Dibaryon model for nuclear force and the properties of the system
The dibaryon model for interaction, which implies the formation of an
intermediate six-quark bag dressed by a -field, is applied to the
system, where it results in a new three-body force of scalar nature between the
six-quark bag and a third nucleon. A new multicomponent formalism is developed
to describe three-body systems with nonstatic pairwise interactions and
non-nucleonic degrees of freedom. Precise variational calculations of
bound states are carried out in the dressed-bag model including the new scalar
three-body force. The unified coupling constants and form factors for and
force operators are used in the present approach, in a sharp contrast to
conventional meson-exchange models. It is shown that this three-body force
gives at least half the total binding energy, while the weight of
non-nucleonic components in the H and He wavefunctions can exceed 10%.
The new force model provides a very good description of bound states with
a reasonable magnitude of the coupling constant. A new Coulomb
force between the third nucleon and dibaryon is found to be very important for
a correct description of the Coulomb energy and r.m.s. charge radius in He.
In view of the new results for Coulomb displacement energy obtained here for
A=3 nuclei, an explanation for the long-term Nolen--Schiffer paradox in nuclear
physics is suggested. The role of the charge-symmetry-breaking effects in the
nuclear force is discussed.Comment: 64 pages, 7 figures, LaTeX, to be published in Phys. At. Nucl. (2005
Design, construction, quality control and performance study with cosmic rays of modules for the LHCb electromagnetic calorimeter
Abstract This article addresses the design and construction of modules for the LHCb electromagnetic calorimeter. Quality control and preinstallation tests, including cells pre-calibration, are described and the results of light yield measurements are given