134 research outputs found
Nuclear Polarization of Molecular Hydrogen Recombined on a Non-metallic Surface
The nuclear polarization of molecules formed by recombination
of nuclear polarized H atoms on the surface of a storage cell initially coated
with a silicon-based polymer has been measured by using the longitudinal
double-spin asymmetry in deep-inelastic positron-proton scattering. The
molecules are found to have a substantial nuclear polarization, which is
evidence that initially polarized atoms retain their nuclear polarization when
absorbed on this type of surfac
Precision bond lengths for Rydberg Matter clusters KN (N = 19, 37, 61 and 91) in excitation levels n = 4 - 8 from rotational radio-frequency emission spectra
Clusters of the electronically excited condensed matter Rydberg Matter (RM)
are planar and six-fold symmetric with magic numbers N = 7, 19, 37, 61 and 91.
The bond distances in the clusters are known with a precision of +- 5% both
from theory and Coulomb explosion experiments. Long series of up to 40
consecutive lines from rotational transitions in such clusters are now observed
in emission in the radio-frequency range 7-90 MHz. The clusters are produced in
five different vacuum chambers equipped with RM emitters. The most prominent
series with B = 0.9292 +- 0.0001 MHz agrees accurately with expectation (within
2%) for the planar six-fold symmetric cluster K19 in excitation level n = 4.
Other long series agree even better with K19 at n = 5 and 6. The ratio between
the interatomic distance and the theoretical electron orbit radius (the
dimensional ratio) for K19 in n = 4 is found to be 2.8470 +- 0.0003. For
clusters K19 (n = 6) and K37 (n = 7 and 8) the dimensional ratio 2.90 is the
highest value that is found, which happens to be exactly the theoretical value.
Clusters K61 and K91 in n = 5 and 6 have slightly lower dimensional ratios.
This is expected since the edge effects are smaller. Intensity alternations are
observed of approximately 7:3. The nuclear spins interact strongly with the
magnetic field from the orbiting electrons. Spin transitions are observed with
energy differences corresponding accurately (within 0.6%) to transitions with
apparent total (delta)F = -3 at excitation levels n = 5 and 6. The angular
momentum coupling schemes in the clusters are complex but well understood.Comment: 37 pages, 14 figure
The HERMES Polarized Hydrogen and Deuterium Gas Target in the HERA Electron Storage Ring
The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in
use since 1996 with the polarized electron beam of HERA at DESY to study the
spin structure of the nucleon. Polarized atoms from a Stern-Gerlach Atomic Beam
Source are injected into a storage cell internal to the HERA electron ring.
Atoms diffusing from the center of the storage cell into a side tube are
analyzed to determine the atomic fraction and the atomic polarizations. The
atoms have a nuclear polarization, the axis of which is defined by an external
magnetic holding field. The holding field was longitudinal during 1996-2000,
and was changed to transverse in 2001. The design of the target is described,
the method for analyzing the target polarization is outlined, and the
performance of the target in the various running periods is presented
Response of the ATLAS tile calorimeter prototype to muons
A study of high energy muons traversing the ATLAS hadron Tile calorimeter in the barrel region in the energy range between 10 and 300~GeV is presented. Both test beam experimental data and Monte Carlo simulations are given and show good agreement. The Tile calorimeter capability of detecting isolated muons over the above energy range is demonstrated. A signal to background ratio of about 10 is expected for the nominal LHC luminosity (). The photoelectron statistics effect in the muon shape response is shown. The e/mip ratio is found to be ; the e/ ratio is in the range 0.91 - 0.97. The energy loss of a muon in the calorimeter, dominated by the energy lost in the absorber, can be correlated to the energy loss in the active material. This correlation allows one to correct on an event by event basis the muon energy loss in the calorimeter and therefore reduce the low energy tails in the muon momentum distribution
Results from a combined test of an electromagnetic liquid argon calorimeter with a hadronic scintillating-tile calorimeter
The first combined test of an electromagnetic liquid argon accordion calorimeter and a hadronic scintillating-tile calorimeter was carried out at the CERN SPS. These devices are prototypes of the barrel calorimeter of the future ATLAS experiment at the LHC. The energy resolution of pions in the energy range from 20 to 300~GeV at an incident angle of about 11 is well-described by the expression \sigma/E = ((46.5 \pm 6.0)\%/\sqrt{E} +(1.2 \pm 0.3)\%) \oplus (3.2 \pm 0.4)~\mbox{GeV}/E. Shower profiles, shower leakage, and the angular resolution of hadronic showers were also studied
Evaluation of Fermi Read-out of the ATLAS Tilecal Prototype
Prototypes of the \fermi{} system have been used to read out a prototype of the \atlas{} hadron calorimeter in a beam test at the CERN SPS. The \fermi{} read-out system, using a compressor and a 40 MHz sampling ADC, is compared to a standard charge integrating read-out by measuring the energy resolution of the calorimeter separately with the two systems on the same events. Signal processing techniques have been designed to optimize the treatment of \fermi{} data. The resulting energy resolution is better than the one obtained with the standard read-out
A measurement of the energy loss spectrum of 150 GeV muons in iron
The energy loss spectrum of 150 GeV muons has been measured with a prototype of the ATLAS hadron calorimeter in the H8 beam of the CERN SPS.\\ The differential probability per radiation length of a fractional energy loss has been measured in the range ; it is then compared with the theoretical predictions for energy losses due to bremsstrahlung and production of electron-positron pairs or of energetic knock-on electrons.\\ The integrated probability is in agreement with the theoretical predictions of and . %7.8.96 - start Agreement with theory is also found in two intervals of where production of electron-positron pairs and knock-on electrons dominates. In the region of bremsstrahlung dominance () the measured integrated probability is in agreement with the theoretical value of , obtained using Petrukhin and Shestakov's \cite{PS} description of the bremsstrahlung process. The same result is about 3.6 standard deviations (defined as the quadratic sum of statistical and systematic errors) lower than the theoretical prediction of , obtained using Tsai's \cite{TS} description of bremsstrahlung
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