439 research outputs found
Determination of Deuteron Beam Polarizations at COSY
The vector and tensor polarizations of a deuteron beam have been measured
using elastic deuteron-carbon scattering at 75.6 MeV and deuteron-proton
scattering at 270 MeV. After acceleration to 1170 MeV inside the COSY ring, the
polarizations of the deuterons were checked by studying a variety of nuclear
reactions using a cluster target at the ANKE magnet spectrometer placed at an
internal target position of the storage ring. All these measurements were
consistent with the absence of depolarization during acceleration and provide a
number of secondary standards that can be used in subsequent experiments at the
facility.Comment: 12 pages, 13 figure
Measurement of Spin Correlation Parameters A, A, and A_ at 2.1 GeV in Proton-Proton Elastic Scattering
At the Cooler Synchrotron COSY/J\"ulich spin correlation parameters in
elastic proton-proton (pp) scattering have been measured with a 2.11 GeV
polarized proton beam and a polarized hydrogen atomic beam target. We report
results for A, A, and A_ for c.m. scattering angles between
30 and 90. Our data on A -- the first measurement of this
observable above 800 MeV -- clearly disagrees with predictions of available of
pp scattering phase shift solutions while A and A_ are reproduced
reasonably well. We show that in the direct reconstruction of the scattering
amplitudes from the body of available pp elastic scattering data at 2.1 GeV the
number of possible solutions is considerably reduced.Comment: 4 pages, 4 figure
A Precision Measurement of pp Elastic Scattering Cross Sections at Intermediate Energies
We have measured differential cross sections for \pp elastic scattering with
internal fiber targets in the recirculating beam of the proton synchrotron
COSY. Measurements were made continuously during acceleration for projectile
kinetic energies between 0.23 and 2.59 GeV in the angular range deg. Details of the apparatus and the data analysis are
given and the resulting excitation functions and angular distributions
presented. The precision of each data point is typically better than 4%, and a
relative normalization uncertainty of only 2.5% within an excitation function
has been reached. The impact on phase shift analysis as well as upper bounds on
possible resonant contributions in lower partial waves are discussed.Comment: 23 pages 29 figure
Parity Violation in Proton-Proton Scattering at 221 MeV
The parity-violating longitudinal analyzing power, Az, has been measured in
pp elastic scattering at an incident proton energy of 221 MeV. The result
obtained is Az =(0.84 +/- 0.29 (stat.) +/- 0.17 (syst.)) x 10^{-7}. This
experiment is unique in that it selects a single parity violating transition
amplitude, 3P2-1D2, and consequently directly constrains the weak meson-nucleon
coupling constant h^pp_rho When this result is taken together with the existing
pp parity violation data, the weak meson-nucleon coupling constants h^pp_rho
and h^pp_omega can, for the first time, both be determined.Comment: 8 pages RevTeX4, 3 PostScript figures. Conclusion revised. New
information about weak coupling constants adde
Spin‐Flipping Polarized Deuterons At COSY
We recently stored a 1.85 GeV/c vertically polarized deuteron beam in the COSY Ring in Jülich; we then spin‐flipped it by ramping a new air‐core rf dipole’s frequency through an rf‐induced spin resonance to manipulate the polarization direction of the deuteron beam. We first experimentally determined the resonance’s frequency and set the dipole’s rf voltage to its maximum; then we varied its frequency ramp time and frequency range. We used the EDDA detector to measure the vector and tensor polarization asymmetries. We have not yet extracted the deuteron’s tensor polarization spin‐flip parameters from the measured data, since our short run did not provide adequate tensor analyzing‐power data at 1.85 GeV/c. However, with a 100 Hz frequency ramp and our longest ramp time of 400 s, the deuterons’ vector polarization spin‐flip efficiency was 48±1%. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87592/2/763_1.pd
Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering: Determined by the OLYMPUS Experiment
The OLYMPUS collaboration reports on a precision measurement of the
positron-proton to electron-proton elastic cross section ratio, ,
a direct measure of the contribution of hard two-photon exchange to the elastic
cross section. In the OLYMPUS measurement, 2.01~GeV electron and positron beams
were directed through a hydrogen gas target internal to the DORIS storage ring
at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and
time-of-flight scintillators detected elastically scattered leptons in
coincidence with recoiling protons over a scattering angle range of to . The relative luminosity between the two beam species
was monitored using tracking telescopes of interleaved GEM and MWPC detectors
at , as well as symmetric M{\o}ller/Bhabha calorimeters at
. A total integrated luminosity of 4.5~fb was collected. In
the extraction of , radiative effects were taken into account
using a Monte Carlo generator to simulate the convolutions of internal
bremsstrahlung with experiment-specific conditions such as detector acceptance
and reconstruction efficiency. The resulting values of , presented
here for a wide range of virtual photon polarization ,
are smaller than some hadronic two-photon exchange calculations predict, but
are in reasonable agreement with a subtracted dispersion model and a
phenomenological fit to the form factor data.Comment: 5 pages, 3 figures, 2 table
Parity Violation in Proton-Proton Scattering at 221 MeV
TRIUMF experiment 497 has measured the parity violating longitudinal
analyzing power, A_z, in pp elastic scattering at 221.3 MeV incident proton
energy. This paper includes details of the corrections, some of magnitude
comparable to A_z itself, required to arrive at the final result. The largest
correction was for the effects of first moments of transverse polarization. The
addition of the result, A_z=(0.84 \pm 0.29 (stat.) \pm 0.17 (syst.)) \times
10^{-7}, to the pp parity violation experimental data base greatly improves the
experimental constraints on the weak meson-nucleon coupling constants
h^{pp}_\rho and h^{pp}_\omega, and has implications for the interpretation of
electron parity violation experiments.Comment: 17 pages RevTeX, 14 PostScript figures. Revised version with
additions suggested by Phys. Rev.
Higher Order Spin Resonances in a 2.1 GeV/c Polarized Proton Beam
Spin resonances can depolarize or spin-flip a polarized beam. We studied 1st
and higher order spin resonances with stored 2.1 GeV/c vertically polarized
protons. The 1st order vertical ({\nu}y) resonance caused almost full
spin-flip, while some higher order {\nu}y resonances caused partial
depolarization. The 1st order horizontal ({\nu}x) resonance caused almost full
depolarization, while some higher order {\nu}x resonances again caused partial
depolarization. Moreover, a 2nd order {\nu}x resonance is about as strong as
some 3rd order {\nu}x resonances, while some 3rd order {\nu}y resonances are
much stronger than a 2nd order {\nu}y resonance. One thought that {\nu}y spin
resonances are far stronger than {\nu}x, and that lower order resonances are
stronger than higher order; the data do not support this.Comment: 5 pages, 5 figures Note that Fig. 5 did not appear in the PRL due to
space limitation, but did appear in the March 2012 CERN Courier News Item
"Results from SPIN@COSY may bode well for RHIC
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Improved Upper Limit on the Neutrino Mass from a Direct Kinematic Method by KATRIN.
We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (-1.0_{-1.1}^{+0.9}) eV^{2}. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation
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