We present extractions of the nucleon nonsinglet moments utilizing new precision data on the deuteron F 2 structure function at large Bjorkenx determined via the Rosenbluth separation technique at ...Jefferson Lab Experimental Hall C. These new data are combined with a complementary set of data on the proton previously measured in Hall C at similar kinematics and world datasets on the proton and deuteron at lower x measured at SLAC and CERN. The new Jefferson Lab data provide coverage of the upper third of the x range, crucial for precision determination of the higher moments. In contrast to previous extractions, these moments have been corrected for nuclear effects in the deuteron using a new global fit to the deuteron and proton data. The obtained experimental moments represent an order of magnitude improvement in precision over previous extractions using high x data. Moreover, recent exciting developments in lattice QCD calculations provide a first ever comparison of these new experimental results with calculations of moments carried out at the physical pion mass, as well as a new approach that first calculates the quark distributions directly before determining moments.
The lifetime of a Λ particle embedded in a nucleus (hypernucleus) decreases from that of free Λ decay mainly due to the opening of the ΛN→NN weak decay channel. However, it is generally believed that ...the lifetime of a hypernucleus attains a constant value (saturation) for medium to heavy hypernuclear masses, yet this hypothesis has been difficult to verify. This paper presents a direct measurement of the lifetime of medium-heavy hypernuclei that were hyper-fragments produced by fission or break-up from heavy hypernuclei initially produced with a 2.34 GeV photon-beam incident on thin Fe, Cu, Ag, and Bi target foils. For each event, fragments were detected in coincident pairs by a low-pressure multi-wire proportional chamber system. The lifetime was extracted from decay time spectrum formed by the difference of the time zeros between the pairs. The measured lifetime from each target is actually a statistical average over a range of mass with mean about 1/2 of the target mass and appears to be a constant of about 200 ps. Although this result cannot exclude unexpected shorter or longer lifetimes for some specific hypernuclei or hypernuclear states, it shows that a systematic decrease in lifetime as hypernuclear mass increases is not a general feature for hypernuclei with mean mass up to A≈130. On the other hand, the success of this experiment and its technique shows that the time delayed fissions observed and used by all the lifetime measurements done so far on heavy hypernuclei could likely have originated from hyper-fragments lighter than the assumed masses.
Backward-angle meson electroproduction above the resonance region, which was previously ignored, is anticipated to offer unique access to the three quark plus sea component of the nucleon wave ...function. In this Letter, we present the first complete separation of the four electromagnetic structure functions above the resonance region in exclusive ω electroproduction off the proton, ep→e′pω, at central Q2 values of 1.60, 2.45 GeV2, at W=2.21 GeV. The results of our pioneering −u≈−umin study demonstrate the existence of a unanticipated backward-angle cross section peak and the feasibility of full L/T/LT/TT separations in this never explored kinematic territory. At Q2=2.45 GeV2, the observed dominance of σT over σL, is qualitatively consistent with the collinear QCD description in the near-backward regime, in which the scattering amplitude factorizes into a hard subprocess amplitude and baryon to meson transition distribution amplitudes: universal nonperturbative objects only accessible through backward-angle kinematics.
We describe a new aerogel threshold Cherenkov detector installed in the HMS spectrometer in Hall C at Jefferson Lab. The Hall C experimental program in 2003 required an improved particle ...identification system for better identification of
π
/
K
/
p
, which was achieved by installing an additional threshold Cherenkov counter. Two types of aerogel with
n
=
1.030
and
n
=
1.015
allow one to reach
∼
10
-
3
proton and
10
-
2
kaon rejection in the 1–5
GeV/
c momentum range with pion detection efficiency better than 99% (97%). The detector response shows no significant position dependence due to a diffuse light collection technique. The diffusion box was equipped with 16 Photonis XP4572 photo multiplier tubes (PMTs). The mean number of photo-electrons in saturation was
∼
16
and
∼
8
, respectively. This allows even for separation of slower particles slightly above threshold.
Backward-angle meson electroproduction above the resonance region, which was previously ignored, is anticipated to offer unique access to the three quark plus sea component of the nucleon wave ...function. In this Letter, we present the first complete separation of the four electromagnetic structure functions above the resonance region in exclusive ω electroproduction off the proton, ep → e'pω , at central Q2 values of 1.60, 2.45 GeV2 , at W=2.21 GeV . The results of our pioneering -u≈-umin study demonstrate the existence of a unanticipated backward-angle cross section peak and the feasibility of full L / T / LT / TT separations in this never explored kinematic territory. At Q2=2.45 GeV2 , the observed dominance of σT over σL , is qualitatively consistent with the collinear QCD description in the near-backward regime, in which the scattering amplitude factorizes into a hard subprocess amplitude and baryon to meson transition distribution amplitudes: universal nonperturbative objects only accessible through backward-angle kinematics.
Microvascular decompression of the trigeminal nerve root entry zone has become a standard treatment for trigeminal neuralgia. It has been widely reported with a low morbidity. This case report ...details an unusual and previously unreported complication of this procedure.
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