2,012 research outputs found
Effect of the heliospheric interface on the distribution of interstellar hydrogen atom inside the heliosphere
This paper deals with the modeling of the interstellar hydrogen atoms (H
atoms) distribution in the heliosphere. We study influence of the heliospheric
interface, that is the region of the interaction between solar wind and local
interstellar medium, on the distribution of the hydrogen atoms in vicinity of
the Sun. The distribution of H atoms obtained in the frame of the
self-consistent kinetic-gasdynamic model of the heliospheric interface is
compared with a simplified model which assumes Maxwellian distribution of H
atoms at the termination shock and is called often as 'hot' model. This
comparison shows that the distribution of H atoms is significantly affected by
the heliospheric interface not only at large heliocentric distances, but also
in vicinity of the Sun at 1-5 AU. Hence, for analysis of experimental data
connected with direct or undirect measurements of the interstellar atoms one
necessarily needs to take into account effects of the heliospheric interface.
In this paper we propose a new model that is relatively simple but takes into
account all major effects of the heliospheric interface. This model can be
applied for analysis of backscattered Ly-alpha radiation data obtained on board
of different spacecraft.Comment: published in Astronomy Letter
The Beurling--Malliavin Multiplier Theorem and its analogs for the de Branges spaces
Let be a non-negative function on . We are looking for a
non-zero from a given space of entire functions satisfying The
classical Beurling--Malliavin Multiplier Theorem corresponds to and the
classical Paley--Wiener space as . We survey recent results for the case
when is a de Branges space \he. Numerous answers mainly depend on the
behaviour of the phase function of the generating function .Comment: Survey, 25 page
Singular perturbation theory for interacting fermions in two dimensions
We consider a system of interacting fermions in two dimensions beyond the
second-order perturbation theory in the interaction. It is shown that the
mass-shell singularities in the self-energy, arising already at the second
order of the perturbation theory, manifest a non-perturbative effect: an
interaction with the zero-sound mode. Resumming the perturbation theory for a
weak, short-range interaction and accounting for a finite curvature of the
fermion spectrum, we eliminate the singularities and obtain the results for the
quasi-particle self-energy and the spectral function to all orders in the
interaction with the zero-sound mode. A threshold for emission of zero-sound
waves leads a non-monotonic variation of the self-energy with energy (or
momentum) near the mass shell. Consequently, the spectral function has a
kink-like feature. We also study in detail a non-analytic temperature
dependence of the specific heat, . It turns out that although
the interaction with the collective mode results in an enhancement of the
fermion self-energy, this interaction does not affect the non-analytic term in
due to a subtle cancellation between the contributions from the real and
imaginary parts of the self-energy. For a short-range and weak interaction,
this implies that the second-order perturbation theory suffices to determine
the non-analytic part of . We also obtain a general form of the
non-analytic term in , valid for the case of a generic Fermi liquid,
\emph{i.e.}, beyond the perturbation theory.Comment: 53 pages, 10 figure
The Mu2e undoped CsI crystal calorimeter
The Mu2e experiment at Fermilab will search for Charged Lepton Flavor
Violating conversion of a muon to an electron in an atomic field. The Mu2e
detector is composed of a tracker, an electromagnetic calorimeter and an
external system, surrounding the solenoid, to veto cosmic rays. The calorimeter
plays an important role to provide: a) excellent particle identification
capabilities; b) a fast trigger filter; c) an easier tracker track
reconstruction. Two disks, located downstream of the tracker, contain 674 pure
CsI crystals each. Each crystal is read out by two arrays of UV-extended SiPMs.
The choice of the crystals and SiPMs has been finalized after a thorough test
campaign. A first small scale prototype consisting of 51 crystals and 102 SiPM
arrays has been exposed to an electron beam at the BTF (Beam Test Facility) in
Frascati. Although the readout electronics were not the final, results show
that the current design is able to meet the timing and energy resolution
required by the Mu2e experiment.Comment: 6 pages, 8 figures, proceedings of the "Calorimetry for the high
energy frontier (CHEF17)" conference, 2-6 October 2017, Lyon, Franc
Design, status and perspective of the Mu2e crystal calorimeter
The Mu2e experiment at Fermilab will search for the charged lepton flavor
violating process of neutrino-less coherent conversion in the field
of an aluminum nucleus. Mu2e will reach a single event sensitivity of about
that corresponds to four orders of magnitude improvements
with respect to the current best limit. The detector system consists of a straw
tube tracker and a crystal calorimeter made of undoped CsI coupled with Silicon
Photomultipliers. The calorimeter was designed to be operable in a harsh
environment where about 10 krad/year will be delivered in the hottest region
and work in presence of 1 T magnetic field. The calorimeter role is to perform
/e separation to suppress cosmic muons mimiking the signal, while
providing a high level trigger and a seeding the track search in the tracker.
In this paper we present the calorimeter design and the latest RD results.Comment: 4 pages, conference proceeding for a presentation held at TIPP'2017.
To be published on Springer Proceedings in Physic
Quality Assurance on a custom SiPMs array for the Mu2e experiment
The Mu2e experiment at Fermilab will search for the coherent
conversion on aluminum atoms. The detector system consists of a straw tube
tracker and a crystal calorimeter. A pre-production of 150 Silicon
Photomultiplier arrays for the Mu2e calorimeter has been procured. A detailed
quality assur- ance has been carried out on each SiPM for the determination of
its own operation voltage, gain, dark current and PDE. The measurement of the
mean-time-to-failure for a small random sample of the pro-production group has
been also completed as well as the determination of the dark current increase
as a function of the ioninizing and non-ioninizing dose.Comment: 4 pages, 10 figures, conference proceeding for NSS-MIC 201
Superfluid pairing in a polarized dipolar Fermi gas
We calculate the critical temperature of a superfluid phase transition in a
polarized Fermi gas of dipolar particles. In this case the order parameter is
anisotropic and has a nontrivial energy dependence. Cooper pairs do not have a
definite value of the angular momentum and are coherent superpositions of all
odd angular momenta. Our results describe prospects for achieving the
superfluid transition in single-component gases of fermionic polar molecules.Comment: 12 pages, 2 figure
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