70 research outputs found
What have we learned from antiproton proton scattering?
From recent charge exchange measurements in the extreme forward direction, an
independent and precise determination of the pion nucleon coupling constant is
possible. This determination has reopened the debate on the value of this
fundamental coupling constant of nuclear physics. Precise measurements of
charge exchange observables at forward angles below 900 MeV/c would also give a
better understanding of the long range part of the two-pion exchange potential.
For example, the confirmation of the coherence of the tensor forces from the
pion exchange and the isovector two-pion exchange would be very valuable. With
the present data first attempts at an \NbarN partial wave analysis have been
made where, as in nucleon nucleon scattering, the antinucleon nucleon high J
partial waves are mainly given by one-pion exchange. Finally a recent \pbarp
atomic cascade calculation and the fraction of P-state annihilation in gas
targets is commented on.Comment: 10 pages, Latex, to be published in Nucl. Phy
Polarised Quark Distributions in the Nucleon from Semi-Inclusive Spin Asymmetries
We present a measurement of semi-inclusive spin asymmetries for positively
and negatively charged hadrons from deep inelastic scattering of polarised
muons on polarised protons and deuterons in the range 1
GeV. Compared to our previous publication on this subject, with the new
data the statistical errors have been reduced by nearly a factor of two.
From these asymmetries and our inclusive spin asymmetries we determine the
polarised quark distributions of valence quarks and non-strange sea quarks at
=10 GeV. The polarised valence quark distribution, , is positive and the polarisation increases with . The polarised
valence quark distribution, , is negative and the non-strange
sea distribution, , is consistent with zero over the measured
range of . We find for the first moments , and
, where we assumed
. We also determine for the first time the
second moments of the valence distributions .Comment: 17 page
Large enhancement of deuteron polarization with frequency modulated microwaves
We report a large enhancement of 1.7 in deuteron polarization up to values of
0.6 due to frequency modulation of the polarizing microwaves in a two liters
polarized target using the method of dynamic nuclear polarization. This target
was used during a deep inelastic polarized muon-deuteron scattering experiment
at CERN. Measurements of the electron paramagnetic resonance absorption spectra
show that frequency modulation gives rise to additional microwave absorption in
the spectral wings. Although these results are not understood theoretically,
they may provide a useful testing ground for the deeper understanding of
dynamic nuclear polarization.Comment: 10 pages, including the figures coming in uuencoded compressed tar
files in poltar.uu, which also brings cernart.sty and crna12.sty files neede
Spin Structure of the Proton from Polarized Inclusive Deep-Inelastic Muon-Proton Scattering
We have measured the spin-dependent structure function in inclusive
deep-inelastic scattering of polarized muons off polarized protons, in the
kinematic range and . A
next-to-leading order QCD analysis is used to evolve the measured
to a fixed . The first moment of at is .
This result is below the prediction of the Ellis-Jaffe sum rule by more than
two standard deviations. The singlet axial charge is found to be . In the Adler-Bardeen factorization scheme, is
required to bring in agreement with the Quark-Parton Model. A
combined analysis of all available proton and deuteron data confirms the
Bjorken sum rule.Comment: 33 pages, 22 figures, uses ReVTex and smc.sty. submitted to Physical
Review
Polarised quark distributions in the nucleon from semi-inclusive spin asymmetries
We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 1~GeV. Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nearly a factor of two. From these asymmetries and our inclusive spin asymmetries we determine the polarised quark distributions of valence quarks and non-strange sea quarks at =10~GeV. The polarised valence quark distribution, , is positive and the polarisation increases with . The polarised valence quark distribution, , is negative and the non-strange sea distribution, , is consistent with zero over the measured range of . We find for the first moments , and , where we assumed . We also determine for the first time the second moments of the valence distributions .We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 1 GeV. Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nearly a factor of two. From these asymmetries and our inclusive spin asymmetries we determine the polarised quark distributions of valence quarks and non-strange sea quarks at =10 GeV. The polarised valence quark distribution, , is positive and the polarisation increases with . The polarised valence quark distribution, , is negative and the non-strange sea distribution, , is consistent with zero over the measured range of . We find for the first moments , and , where we assumed . We also determine for the first time the second moments of the valence distributions .We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 1 GeV. Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nearly a factor of two. From these asymmetries and our inclusive spin asymmetries we determine the polarised quark distributions of valence quarks and non-strange sea quarks at =10 GeV. The polarised valence quark distribution, , is positive and the polarisation increases with . The polarised valence quark distribution, , is negative and the non-strange sea distribution, , is consistent with zero over the measured range of . We find for the first moments , and , where we assumed . We also determine for the first time the second moments of the valence distributions .We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 1 GeV. Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nearly a factor of two. From these asymmetries and our inclusive spin asymmetries we determine the polarised quark distributions of valence quarks and non-strange sea quarks at =10 GeV. The polarised valence quark distribution, , is positive and the polarisation increases with . The polarised valence quark distribution, , is negative and the non-strange sea distribution, , is consistent with zero over the measured range of . We find for the first moments , and , where we assumed . We also determine for the first time the second moments of the valence distributions .We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 1 GeV. Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nearly a factor of two. From these asymmetries and our inclusive spin asymmetries we determine the polarised quark distributions of valence quarks and non-strange sea quarks at =10 GeV. The polarised valence quark distribution, , is positive and the polarisation increases with . The polarised valence quark distribution, , is negative and the non-strange sea distribution, , is consistent with zero over the measured range of . We find for the first moments , and , where we assumed . We also determine for the first time the second moments of the valence distributions .We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0.0031 GeV 2 . Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nearly a factor of two. From these asymmetries and our inclusive spin asymmetries we determine the polarised quark distributions of valence quarks and non-strange sea quarks at Q 2 =10 GeV 2 . The polarised u valence quark distribution, Δu v ( x ), is positive and the polarisation increases with x . The polarised d valence quark distribution, Δd v ( x ), is negative and the non-strange sea distribution, Δ q ̄ (x) , is consistent with zero over the measured range of x . We find for the first moments ∫ 0 1 Δu v (x) d x=0.77±0.10±0.08 , ∫ 0 1 Δd v (x) d x=−0.52±0.14±0.09 and ∫ 0 1 Δ q ̄ (x) d x=0.01±0.04±0.03 , where we assumed Δ u ̄ (x)=Δ d ̄ (x) . We also determine for the first time the second moments of the valence distributions ∫ 0 1 xΔq v (x) d x
Spin asymmetries A1 and structure functions g1 of the proton and the deuteron from polarized high energy muon scattering.
Adeva B, Akdogan T, Arik E, et al. Spin asymmetries A(1) and structure functions g(1) of the proton and the deuteron from polarized high energy muon scattering. Phys.Rev. D. 1998;58(11): 112001.We present the final results of the spin asymmetries A(1) and the spin structure functions g(1) of the proton and the deuteron in the kinematic range 0.0008 < x < 0.7 and 0.2 < Q(2) < 100 GeV2. For the determination of A(1), in addition to the usual method which employs inclusive scattering events and includes a large radiative background at low x, we use a new method which minimizes the radiative background by selecting events with at least one hadron as well as a muon in the final state. We find that this hadron method gives smaller errors for x < 0.02, so it is combined with the usual method to provide the optimal set of results. [S0556-2821(98)07017-9]
Measurement of the spin-dependent structure function g1(x) of the proton
Adams D, Adeva B, Arik E, et al. Measurement of the spin-dependent structure function g1(x) of the proton. Phys.Lett. B. 1994;329(2-3):399-406.We have measured the spin-dependent structure function of the proton in deep inelastic scattering of polarized muons off polarized protons, in the kinematic range and 1\,\mbox{GeV}~2
. Its first moment, , is found to be 0.136 \pm 0.011\,(\mbox{stat.})\pm 0.011\,(\mbox{syst.}) at Q~2=10\,\mbox{GeV}~2. This value is smaller than the prediction of the Ellis--Jaffe sum rule by two standard deviations, and is consistent with previous measurements. A combined analysis of all available proton, deuteron and neutron data confirms the Bjorken sum rule to within of the theoretical value
Measurement of the polarized valence and sea quark distributions of the nucleon in at CERN
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