1,585 research outputs found
Synthetic Frequency Protocol in the Ramsey Spectroscopy of Clock Transitions
We develop an universal method to significantly suppress probe-induced shifts
in any types of atomic clocks using the Ramsey spectroscopy. Our approach is
based on adaptation of the synthetic frequency concept [V. I. Yudin, et al.,
Phys. Rev. Lett. 107, 030801 (2011)] (previously developed for BBR shift
suppression) to the Ramsey spectroscopy with the use of interrogations for
different dark time intervals. Universality of the method consists in
arbitrariness of the possible Ramsey schemes. However, most extremal results
are obtained in combination with so-called hyper-Ramsey spectroscopy [V. I.
Yudin, et al., Phys. Rev. A 82, 011804(R) (2010)]. In the latter case, the
probe-induced frequency shifts can be suppressed considerably below a
fractional level of 10 practically for any optical atomic clocks, where
this shift previously was metrologically significant. The main advantage of our
method in comparison with other radical hyper-Ramsey approaches [R. Hobson, et
al., Phys. Rev. A 93, 010501(R) (2016); T. Zanon-Willette, et al., Phys. Rev. A
93, 042506 (2016)] consist in much greater efficiency and resistibility in the
presence of decoherentization.Comment: 9 pages, 7 figure
Theory of nonlinear sub-Doppler laser spectroscopy taking into account atomic-motion-induced density-dependent effects in a gas
We develop a field-nonlinear theory of sub-Doppler spectroscopy in a gas of
two-level atoms, based on a self-consistent solution of the Maxwell-Bloch
equations in the mean field and single-atom density matrix approximations. This
makes it possible to correctly take into account the effects caused by the free
motion of atoms in a gas, which lead to a nonlinear dependence of the
spectroscopic signal on the atomic density even in the absent of a direct
interatomic interaction (e.g., dipole-dipole interaction). Within the framework
of this approach, analytical expressions for the light field were obtained for
an arbitrary number of resonant waves and arbitrary optical thickness of a gas
medium. Sub-Doppler spectroscopy in the transmission signal for two
counterpropagating and co-propagating waves has been studied in detail. A
previously unknown red shift of a narrow sub-Doppler resonance is predicted in
a counterpropagating waves scheme, when the frequency of one wave is fixed and
the frequency of the other wave is varied. The magnitude of this shift depends
on the atomic density and can be more than an order of magnitude greater than
the known shift from the interatomic dipole-dipole interaction (Lorentz-Lorenz
shift). The found effects, caused by the free motion of atoms, require a
significant revision of the existing picture of spectroscopic effects depending
on the density of atoms in a gas. Apart of fundamental aspect, obtained results
are important for precision laser spectroscopy and optical atomic clocks.Comment: 18 pages, 12 figure
Probe field ellipticity-induced shift in an atomic clock
We investigate the probe field induced shift for atomic lattice-based and
ion-trap clocks, which can be considered as a near resonant ac-Stark shift,
connected to the Zeeman structure of atomic levels and their splitting in a dc
magnetic field. This shift arises from possible residual ellipticity in the
polarization of the probe field and uncertainty in the magnetic field
orientation. Such a shift can have an arbitrary sign and, for some experimental
conditions, can reach the fractional value of the order of
10-10, i.e., it is not negligible. Thus, it should be taken
into account in the uncertainty budgets for the modern ultra-precise atomic
clocks. In addition, it is shown that when using hyper-Ramsey spectroscopy,
this shift can be reduced to a level much lower than .Comment: 8 pages, 6 figure
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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