90 research outputs found
Enhanced Sensitivity to the Time Variation of the Fine-Structure Constant and in Diatomic Molecules: A Closer Examination of Silicon Monobromide
Recently it was pointed out that transition frequencies in certain diatomic
molecules have an enhanced sensitivity to variations in the fine-structure
constant and the proton-to-electron mass ratio due to a near
cancellation between the fine-structure and vibrational interval in a ground
electronic multiplet [V.~V.~Flambaum and M.~G.~Kozlov, Phys. Rev. Lett.~{\bf
99}, 150801 (2007)]. One such molecule possessing this favorable quality is
silicon monobromide. Here we take a closer examination of SiBr as a candidate
for detecting variations in and . We analyze the rovibronic
spectrum by employing the most accurate experimental data available in the
literature and perform \emph{ab initio} calculations to determine the precise
dependence of the spectrum on variations in . Furthermore, we calculate
the natural linewidths of the rovibronic levels, which place a fundamental
limit on the accuracy to which variations may be determined.Comment: 8 pages, 2 figure
Transverse Profile Monitor using Ion Probe Beams
A profile monitor is described that makes use of a low-intensity and low-energy ion beam to measure the transverse profile of a dense proton beam of small dimensions. Three tehcniques are considered based on the use of ion beams having a pencil, curtain, or cylindrical shape. The detector is almost non-interceptive for the proton beam and does not introduce disturbances in the machine environment. The theroretical aspects of the techniques used, together with experimental results obtained at the CERN SPS and Linac, are presented
Test of a dispersion sweep correction system using a centroid in the DIRAC beam line
A new proton beam position detector named "centroid" is placed in the DIRAC target situation and is aligned with respect to the beam. Behind it there is a set of various targets used for the DIRAC experiment. The "centroid" itself collects the secondary electrons, which are emitted by the target when hit by the proton beam. This provides an on-line verification of the beam position without obstructing the beam path by a screen, and without perturbing the experiment. A computer application then calculates the corrections needed to centre the beam in both planes as a function of time. This report will explain how this is done
Zero Order Estimates for Analytic Functions
The primary goal of this paper is to provide a general multiplicity estimate.
Our main theorem allows to reduce a proof of multiplicity lemma to the study of
ideals stable under some appropriate transformation of a polynomial ring. In
particular, this result leads to a new link between the theory of polarized
algebraic dynamical systems and transcendental number theory. On the other
hand, it allows to establish an improvement of Nesterenko's conditional result
on solutions of systems of differential equations. We also deduce, under some
condition on stable varieties, the optimal multiplicity estimate in the case of
generalized Mahler's functional equations, previously studied by Mahler,
Nishioka, Topfer and others. Further, analyzing stable ideals we prove the
unconditional optimal result in the case of linear functional systems of
generalized Mahler's type. The latter result generalizes a famous theorem of
Nishioka (1986) previously conjectured by Mahler (1969), and simultaneously it
gives a counterpart in the case of functional systems for an important
unconditional result of Nesterenko (1977) concerning linear differential
systems. In summary, we provide a new universal tool for transcendental number
theory, applicable with fields of any characteristic. It opens the way to new
results on algebraic independence, as shown in Zorin (2010).Comment: 42 page
Elliptic logarithms, diophantine approximation and the Birch and Swinnerton-Dyer conjecture
Most, if not all, unconditional results towards the abc-conjecture rely
ultimately on classical Baker's method. In this article, we turn our attention
to its elliptic analogue. Using the elliptic Baker's method, we have recently
obtained a new upper bound for the height of the S-integral points on an
elliptic curve. This bound depends on some parameters related to the
Mordell-Weil group of the curve. We deduce here a bound relying on the
conjecture of Birch and Swinnerton-Dyer, involving classical, more manageable
quantities. We then study which abc-type inequality over number fields could be
derived from this elliptic approach.Comment: 20 pages. Some changes, the most important being on Conjecture 3.2,
three references added ([Mas75], [MB90] and [Yu94]) and one reference updated
[BS12]. Accepted in Bull. Brazil. Mat. So
Commissioning and First Operation of the Antiproton Decelerator (AD)
The Antiproton Decelerator (AD) is a simplified source of antiprotons which provides low energy antiprotons for experiments, replacing four machines: AC (Antiproton Collector), AA (Antiproton Accumulator), PS and LEAR (Low Energy Antiproton Ring), shutdown in 1996. The former AC was modified to include deceleration and electron cooling. The AD started operation in July 2000 and has since delivered cooled beam at 100 MeV/c (kinetic energy of 5.3 MeV) to 3 experiments (ASACUSA, ATHENA and ATRAP) for 1500 h. The flux (up to 2.5´105pbars /s delivered in short pulses of 330 ns every 110 s) and the quality of the ejected beam are not far from the design specifications. A linear RF Quadrupole Decelerator (RFQD) was commissioned in November 2000 to post-decelerate the beam for ASACUSA from 5.3 MeV to about 15 keV. Problems encountered in converting the fixed energy AC into a decelerating machine will be outlined, and the present status of the AD, including the performance of the cooling systems and the special diagnostics to cope with beams of less than 107 pbars, will be reviewed. Possible future developments will be sketche
An Antiproton Decelerator in the CERN PS Complex
The present CERN PS low-energy antiproton complex involves 4 machines to collect, cool, decelerate and supply experiments with up to 1010 antiprotons per pulse and per hour of momenta ranging from 0.1 to 2 GeV/c. In view of a possible future physics programme requiring low energy antiprotons, mainly to carry out studies on antihydrogen, a simplified scheme providing at low cost antiprotons at 100 MeV/c has been studied. It requires only one machine, the present Antiproton Collector (AC) converted into a cooler and decelerator (Antiproton Decelerator, AD) and delivering beam to experiments in the hall of the present Antiproton Accumulator Complex (AAC) [1]. This paper describes the feasibility study of such a scheme [2]
The antiproton decelerator: AD
A simplified scheme for the provision of antiprotons at 100 MeV/c based on fast extraction is described. The scheme uses the existing production target area and the modified Antiproton Collector Ring in their current location. The physics programme is largely based on capturing and storing antiprotons in Penning traps for the production and spectroscopy of antihydrogen. The machine modifications necessary to deliver batches of 1 107 /min at 100 MeV/c are described. Details of the machine layout and the experimental area in the existing AAC Hall are given
The antiproton decelerator (AD), a simplified antiproton source (feasibility study)
In view of a possible future physics programme concerning antihydrogen a simplified scheme for the provision of antiprotons of a few MeV has been studied. It uses the present target area and the modified Antiproton Collector (AC) in its present location. In this report all the systems are reviewed and their modifications discussed
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