5,207 research outputs found
Geometric-phase-induced false electric dipole moment signals for particles in traps
Theories are developed to evaluate Larmor frequency shifts, derived from geometric phases, in experiments to measure electric dipole moments (EDMs) of trapped, atoms, molecules and neutrons. A part of these shifts is proportional to the applied electric field and can be interpreted falsely as an electric dipole moment. A comparison is made between our theoretical predictions for these shifts and some results from our recent experiments, which shows agreement to within the experimental errors of 15 %. The comparison also demonstrates that some trapped particle EDM experiments have reached the sensitivity where stringent precautions are needed to minimise and control such false EDMs. Computer simulations of these processes are also described. They give good agreement with the analytical results and they extend the study by investigating the influence of varying surface reflection laws in the hard walled traps considered. They also explore the possibility to suppress such false EDMs by introducing collisions with buffer gas particles. Some analytic results for frequency shifts proportional to the square of the E-field are also given and there are results for the averaging of the B-field in the absence of an E-field
An Improved Experimental Limit on the Electric Dipole Moment of the Neutron
An experimental search for an electric-dipole moment (EDM) of the neutron has
been carried out at the Institut Laue-Langevin (ILL), Grenoble. Spurious
signals from magnetic-field fluctuations were reduced to insignificance by the
use of a cohabiting atomic-mercury magnetometer. Systematic uncertainties,
including geometric-phase-induced false EDMs, have been carefully studied. Two
independent approaches to the analysis have been adopted. The overall results
may be interpreted as an upper limit on the absolute value of the neutron EDM
of |d_n| < 2.9 x 10^{-26} e cm (90% CL).Comment: 5 pages, 2 figures. The published PRL is slightly more terse (e.g. no
section headings) than this version, due to space constraints. Note a small
correction-to-a-correction led to an adjustment of the final limit from 3.0
to 2.9 E-26 e.cm compared to the first version of this preprin
CMS endcap RPC gas gap production for upgrade
The CMS experiment will install a RE4 layer of 144 new Resistive Plate Chambers (RPCs) on the existing york YE3 at both endcap regions to trigger high momentum muons from the proton-proton interaction. In this paper, we present the detailed procedures used in the production of new RPC gas gaps adopted in the CMS upgrade. Quality assurance is enforced as ways to maintain the same quality of RPC gas gaps as the existing 432 endcap RPC chambers that have been operational since the beginning of the LHC operation
Performance of the Gas Gain Monitoring system of the CMS RPC muon detector and effective working point fine tuning
The Gas Gain Monitoring (GGM) system of the Resistive Plate Chamber (RPC)
muon detector in the Compact Muon Solenoid (CMS) experiment provides fast and
accurate determination of the stability in the working point conditions due to
gas mixture changes in the closed loop recirculation system. In 2011 the GGM
began to operate using a feedback algorithm to control the applied voltage, in
order to keep the GGM response insensitive to environmental temperature and
atmospheric pressure variations. Recent results are presented on the feedback
method used and on alternative algorithms
The Upgrade of the CMS RPC System during the First LHC Long Shutdown
The CMS muon system includes in both the barrel and endcap region Resistive
Plate Chambers (RPC). They mainly serve as trigger detectors and also improve
the reconstruction of muon parameters. Over the years, the instantaneous
luminosity of the Large Hadron Collider gradually increases. During the LHC
Phase 1 (~first 10 years of operation) an ultimate luminosity is expected above
its design value of 10^34/cm^2/s at 14 TeV. To prepare the machine and also the
experiments for this, two long shutdown periods are scheduled for 2013-2014 and
2018-2019. The CMS Collaboration is planning several detector upgrades during
these long shutdowns. In particular, the muon detection system should be able
to maintain a low-pT threshold for an efficient Level-1 Muon Trigger at high
particle rates. One of the measures to ensure this, is to extend the present
RPC system with the addition of a 4th layer in both endcap regions. During the
first long shutdown, these two new stations will be equipped in the region
|eta|<1.6 with 144 High Pressure Laminate (HPL) double-gap RPCs operating in
avalanche mode, with a similar design as the existing CMS endcap chambers.
Here, we present the upgrade plans for the CMS RPC system for the fist long
shutdown, including trigger simulation studies for the extended system, and
details on the new HPL production, the chamber assembly and the quality control
procedures.Comment: 9 pages, 6 figures, presented by M.Tytgat at the XI workshop on
Resistive Plate Chambers and Related Detectors (RPC2012), INFN - Laboratori
Nazionali di Frascati, February 5-10, 201
Reply to Comment on An Improved Experimental Limit on the Electric Dipole Moment of the Neutron
Reply to the Comment of Lamoreaux and Golub. Our conclusions are unchanged
Gravitational depolarization of ultracold neutrons: comparison with data
We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin-depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data
Revised experimental upper limit on the electric dipole moment of the neutron
We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons; an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of dn=−0.21±1.82×10−26 e cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of 3.0×10−26 e cm (90% C.L.) or 3.6×10−26 e cm (95% C.L.)
Simulation of the CMS Resistive Plate Chambers
The Resistive Plate Chamber (RPC) muon subsystem contributes significantly to
the formation of the trigger decision and reconstruction of the muon trajectory
parameters. Simulation of the RPC response is a crucial part of the entire CMS
Monte Carlo software and directly influences the final physical results. An
algorithm based on the parametrization of RPC efficiency, noise, cluster size
and timing for every strip has been developed. Experimental data obtained from
cosmic and proton-proton collisions at TeV have been used for
determination of the parameters. A dedicated validation procedure has been
developed. A good agreement between the simulated and experimental data has
been achieved.Comment: to be published in JINS
Measurement of the permanent electric dipole moment of the neutron
We present the result of an experiment to measure the electric dipole moment EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons (UCN). Our measurement stands in the long history of EDM experiments probing physics violating time reversal invariance. The salient features of this experiment
were the use of a Hg-199 co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes. The statistical analysis was performed on blinded datasets by two separate groups while the estimation of systematic effects profited from an
unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{\rm n} = (0.0\pm1.1_{\rm stat}\pm0.2_{\rmsys})\times10^{-26}e\,{\rm cm}
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