A
bstract
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized ...protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos (
ϕ−ϕ
S
) modulations provide evidence for a sizable worm-gear (II) distribution,
g
1
T
q
x
p
T
2
. Most of the other modulations are found to be consistent with zero with the notable exception of large sin (
ϕ
S
) modulations for charged pions and
K
+
.
Abstract
Measuring the scintillation and ionization yields of liquid xenon in response to ultra-low energy nuclear recoil events is necessary to increase the sensitivity of liquid xenon experiments ...to light dark matter. Neutron capture on xenon can be used to produce nuclear recoil events with energies below 0.3 keV
NR
via the asymmetric emission of
γ
rays during nuclear de-excitation. The feasibility of an ultra-low energy nuclear recoil measurement using neutron capture was investigated for the Michigan Xenon (MiX) detector, a small dual-phase xenon time projection chamber that is optimized for a high scintillation gain. Simulations of the MiX detector, a partial neutron moderator, and a pulsed neutron generator indicate that a population of neutron capture events can be isolated from neutron scattering events. Further, the rate of neutron captures in the MiX detector was optimized by varying the thickness of the partial neutron moderator, neutron pulse width, and neutron pulse frequency.
Abstract
All experiments observing dilepton pairs (e.g.
e
+
e
-
,
μ
+
μ
-
) must confront the existence of a
combinatoric
background caused by the combining of tracks not arising from the
same ...physics vertex. Some method must be devised to calculate and
remove this background. In this document we describe a particular
event-mixing method relying on many of the unique aspects of the
SeaQuest spectrometer and data. The method described here
calculates the combinatoric background with correct normalization;
i.e., there is no need to assign a floating normalization factor
that is then determined in a subsequent fitting procedure. Numerous
tests are applied to demonstrate the reliability of the method.
Flux-dependent nonlinearity (reciprocity failure) in HgCdTe near-infrared detectors can severely impact an instrument’s performance, in particular, with respect to precision photometric measurements. ...The cause of this effect is presently not understood. To investigate reciprocity failure, a dedicated test system was built. For flux levels between 1 and50,000 photons s-1
50
,
000
photons
s
-
1
, a sensitivity to reciprocity failure of approximately0.1% decade-1
0.1
%
decade
-
1
was achieved. A wavelength-independent nonlinearity due to reciprocity failure of about0.35% decade-1
0.35
%
decade
-
1
was measured in a 1.7 μm HgCdTe detector.
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A detailed study of reciprocity failure in four 1.7 μm cutoff HgCdTe near-infrared detectors is presented. The sensitivity to reciprocity failure is approximately0.1% decade-1
0.1
%
decade
-
1
...over up to 5 orders of magnitude in illumination intensity. The four detectors, which represent three successive production runs with modified growth recipes, show large differences in amount and spatial structure of reciprocity failure. Reciprocity failure could be reduced to negligible levels by cooling the detectors to about 110 K. No wavelength dependence was observed. The observed spatial structure appears to be weakly correlated with image persistence.
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Wide‐field survey instruments are used to efficiently observe extended regions of the sky. To achieve a large field of view and to provide a high signal‐to‐noise ratio for faint sources, many modern ...instruments are undersampled. However, in undersampled detectors, sensitivity variations across individual pixels can severely impact science programs that require high photometric precision. To address this, a near‐infrared spot projection system has been developed. With this system, 1.7 μm cutoff detectors were characterized, and the effect of subpixel nonuniformity was studied. The measurements demonstrate that for detectors with near 100% internal quantum efficiency, 1% photometry can be achieved with a point‐spread function (PSF) size of about half a pixel. For detectors with large subpixel nonuniformity, photometric errors become negligible only if the PSF size is more than about two pixels.
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Solenoid Siberian snakes have successfully maintained polarization in particle rings below 1 GeV, but never in multi-GeV rings, because the spin rotation by a solenoid is inversely proportional to ...the beam momentum. High energy rings, such as Brookhaven’s 255 GeV Relativistic Heavy Ion Collider (RHIC), use only odd multiples of pairs of transverse B-field Siberian snakes directly opposite each other. When it became impractical to use a pair of Siberian Snakes in Fermilab’s 120GeV/c Main Injector, we searched for a new type of single Siberian snake that could overcome all depolarizing resonances in the 8.9–120GeV/c range. We found that a snake made of one 4-twist helix and 2 dipoles could maintain the polarization. This snake design could solve the long-standing problem of significant polarization loss during acceleration of polarized protons from a few GeV to tens of GeV, such as in the AGS, before injecting them into multi-hundred GeV rings, such as RHIC.
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Dual phase Xenon Time Projection Chambers (XeTPCs) are being used by several experiments as a promising technique for direct detection of dark matter. We report on the design and performance of a ...small 3-D sensitive dual phase XeTPC. The position resolution is 2 mm in the center of detector, limited by the hole size of the mesh at the proportional scintillation region. An energy resolution of 1.6%(sigma/E) for 662 keV gamma rays is achieved in the very center of the detector by combining the ionization and scintillation signals at a drift field of 0.5 kV/cm. This represents the best energy resolution achieved among liquid xenon detectors to date. The energy resolution is only slightly dependent on the drift field. Better than 2% energy resolution (sigma/E) for 662 keV gamma rays was achieved for drift fields between 100 V/cm and 2 kV/cm. If such a high position and energy resolution can be achieved in a large volume detector, the dual phase XeTPC will have potential applications in surveys of neutrinoless double-beta decay and in gamma ray imaging.
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