Ruling out Color Transparency in Quasielastic

Quasielastic ^{12}C(e,e^{'}p) scattering was measured at spacelike 4-momentum transfer squared Q^{2}=8, 9.4, 11.4, and 14.2 (GeV/c)^{2}, the highest ever achieved to date. Nuclear transparency for this reaction was extracted by comparing the measured yield to that expected from a plane-wave impulse approximation calculation without any final state interactions. The measured transparency was consistent with no Q^{2} dependence, up to proton momenta of 8.5 GeV/c, ruling out the quantum chromodynamics effect of color transparency at the measured Q^{2} scales in exclusive (e,e^{'}p) reactions. These results impose strict constraints on models of color transparency for protons.

First Precision Measurement of the Parity Violating Asymmetry in Cold Neutron Capture on

We report the first precision measurement of the parity-violating asymmetry in the direction of proton momentum with respect to the neutron spin, in the reaction ^{3}He(n,p)^{3}H, using the capture of polarized cold neutrons in an unpolarized active ^{3}He target. The asymmetry is a result of the weak interaction between nucleons, which remains one of the least well-understood aspects of electroweak theory. The measurement provides an important benchmark for modern effective field theory and potential model calculations. Measurements like this are necessary to determine the spin-isospin structure of the hadronic weak interaction. Our asymmetry result is A_{PV}=[1.55±0.97(stat)±0.24(sys)]×10^{-8}, which has the smallest uncertainty of any hadronic parity-violating asymmetry measurement so far.

Probing the Deuteron at Very Large Internal Momenta.

We measure ^{2}H(e,e^{'}p)n cross sections at 4-momentum transfers of Q^{2}=4.5±0.5 (GeV/c)^{2} over a range of neutron recoil momenta p_{r}, reaching up to ∼1.0 GeV/c. We obtain data at fixed neutron recoil angles θ_{nq}=35°, 45°, and 75° with respect to the 3-momentum transfer q[over →]. The new data agree well with previous data, which reached p_{r}∼500 MeV/c. At θ_{nq}=35° and 45°, final state interactions, meson exchange currents, and isobar currents are suppressed and the plane wave impulse approximation provides the dominant cross section contribution. We compare the new data to recent theoretical calculations, where we observe a significant discrepancy for recoil momenta p_{r}>700 MeV/c.

Searching for Flavor Dependence in Nuclear Quark Behavior.

The observed correlation between the EMC effect and the contribution of short-range correlations (SRCs) in nuclei suggests that the modification of the quark distributions of bound protons and neutrons might occur within SRCs. This raises the possibility that the EMC effect may have an isospin dependence arising from the np dominance of SRCs. We discuss previous attempts to test this possibility and perform a new analysis of existing data. We find no experimental support for the observation of an isospin dependence of the EMC effect.

First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen.

We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.0±1.4(stat)±0.2(syst)]×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=[2.6±1.2(stat)±0.2(syst)]×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=[-7.4±3.5(stat)±0.5(syst)]×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.

Probing the repulsive core of the nucleon-nucleon interaction via the (4)He(e,e'pN) triple-coincidence reaction.

We studied simultaneously the (4)He(e,e'p), (4)He(e,e'pp), and (4)He(e,e'pn) reactions at Q(2)=2(GeV/c)(2) and x(B)>1, for an (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum, in a region where the nucleon-nucleon (NN) force is expected to change from predominantly tensor to repulsive. The abundance of neutron-proton pairs is reduced as the nucleon momentum increases beyond ∼500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum. Our data are compared with calculations of two-nucleon momentum distributions in (4)He and discussed in the context of probing the elusive repulsive component of the NN force.

New measurements of high-momentum nucleons and short-range structures in nuclei.

We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate.

Scaling of the F2 structure function in nuclei and quark distributions at x>1.

We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for x>1, which is sensitive to short-range contributions to the nuclear wave function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the "superfast" quarks probed at x>1. The falloff at x>1 is noticeably stronger in 2H and 3He, but nearly identical for all heavier nuclei.

New measurements of the European Muon Collaboration effect in very light nuclei.

New Jefferson Lab data are presented on the nuclear dependence of the inclusive cross section from (2)H, (3)He, (4)He, (9)Be and (12)C for 0.3 < x < 0.9, Q(2) approximately 3-6 GeV(2). These data represent the first measurement of the EMC effect for (3)He at large x and a significant improvement for (4)He. The data do not support previous A-dependent or density-dependent fits to the EMC effect and suggest that the nuclear dependence of the quark distributions may depend on the local nuclear environment.

Measurement of nuclear transparency for the A(e,e'pi+) reaction.

We have measured the nuclear transparency of the A(e,e'pi+) process in 2H, 12C, 27Al, 63Cu, and 197Au targets. These measurements were performed at the Jefferson Laboratory over a four momentum transfer squared range Q2=1.1 to 4.7 (GeV/c)2. The nuclear transparency was extracted as the super-ratio of (sigmaA/sigmaH) from data to a model of pion-electroproduction from nuclei without pi-N final-state interactions. The Q2 and atomic number dependence of the nuclear transparency both show deviations from traditional nuclear physics expectations and are consistent with calculations that include the quantum chromodynamical phenomenon of color transparency.

[Clinico-anatomical grounds of using flaps with the axial type of blood supply in treatment of patients with open (gunshot) fractures of the crus]. / Kliniko-anatomicheskoe obosnovanie ispol'zovaniia loskutov s osevym tipom krovosnabzheniia pri lechenii bol'nykh s otkrytymi (ognestrel'nymi) perelomami kostei goleni.

The main aim and task of the investigation was to present clinico-anatomical substantiation for plastic operations with the application of flaps with the axial type of blood circulation in treatment of this category of patients. The investigation included 348 clinical cases (for exact statistical data); 65 volunteers (for the assessment of physiological parameters) and 16 topographo-anatomical preparations (variants of the vascular network of the leg). The methods of clinical and rentgenological control were used. The work consisted of 4 stages: 1) clinico-statistical analysis by the materials of 348 clinical observations which allowed to establish the dependence of functional results of the treatment on the sizes of leg soft tissue defects; 2) topographo-anatomical investigations which allowed the topography of the leg vessels to be associated with the typical disposition of the flaps with the axial type of blood supply; 3) physiological investigation using ultrasonic dopplerography and active distance thermography on whose basis the methods were created for exact identification of the sites of the outlet of cutaneous arteries and finding the zones of optimal blood supply of the complex skin flaps being formed; 4) clinical approbation of the results of the investigation. The operations performed on 15 patients have demonstrated high effectiveness the new developed means of preoperative planning.

[Clinico-anatomic rationale for the access and technique in video-endoscopic adrenalectomy]. / Kliniko-anatomicheskoe obosnovanie dostupov i tekhniki éndovideokhirurgicheskoi adrenalektomii.

The results of surgical treatment of 60 patients with tumors of the adrenals with the help of endovideosurgical techniques were analyzed and described. The article also presents the data of experimental investigations performed in 31 corpses of subjects of different constitution and topography of the adrenals in the retroperitoneal space and different accesses to them with the help of endovideosurgical technique. The most effective and safe accesses and the method of endovideosurgical adrenalectomy have been developed, substantiated and approbated in clinical practical work. In most cases the right laparoscopic and left retroperitoneoscopic adrenalectomies should be considered the operations of choice in treatment of patients with tumors of the adrenals. It was proved that the decision for the optimal endovideosurgical access and the corresponding adrenalectomy should be made individually for each patient with special reference to the clinicoanatomical criteria found. The endovideosurgical adrenalectomy should not be opposed to open methods of surgery which are expedient in patients with large size of the tumor, signs of malignancy and possible intraoperative complications.

[A topographic anatomical validation of the choice of the approach in reconstructive operations on the extracranial portion of the internal carotid artery]. / Topografoanatomicheskoe obosnovanie vybora dostupa pri rekonstruktivnykh operatsiiakh na ékstrakranial'nom otdele vnutrennei sonnoi arterii.

The purpose of the research was to give a topographical substantiation of the choice of an approach to the extracranial internal carotid artery (ICA) in view of individual anatomical variability of ICA and various localizations of stenosis or occlusion. In 38 human corpses ICA was uncovered using operative methods proposed by Cooper. DePalma, Pauliukas and Nelson. A comparative estimation of the approaches was given with calculation of standard parameters of the operative wound. It was established that the approach to the subcranial ICA was dependent on the type of constitution, features of the anatomical shape of the mandible, distance between the mandibular angle and mastoid process. The statistical processing of the findings has shown that all the factors in question made up 91.5% which is enough for the mathematical description of the position of ICA. Regression models of accessibility of the ICA segment for each of the four investigated approaches were made. The PC program for Windows 95/NT which allows the estimation of accessibility of ICA in each patient before operation was created. These mathematical models were used in the clinic for surgical treatment of the ICA pathology in 24 patients. The difference between the calculated data of ICA accessibility and intraoperative measurements was +/- 3 mm. It demonstrates reliability of the estimation of the approach parameters before operation.

[The cardioprotective action of the anticonvulsant preparation sodium valproate in disorders of cardiac contractile function caused by acute myocardial infarct in rats]. / Kardioprotektivnoe deistvie protivososudorozhnogo preparata val'proata natriia pri narusheniiakh sokratitel'noi funktsii serdtsa, vyzvannye ostrym infarktom miokarda u krys.

The preventive and therapeutical effects of sodium valproate (SV), 200 mg/kg, on cardiac contractile disorders (developed pressure, rate-pressure products, dp/dt) were studied in rats having 2-day myocardial infarction (MI). The postinfarction rather than preinfarction use of SV substantially restricted the depressed resting left ventricular function. Given by two regimens, SV increased cardiac resistance to the maximum isometric load induced by 60-sec ligation of the ascending aorta. The cardioprotective effect of the drug was shown due to its positive chronotropic action rather than its inotropic one. Thus, SV may be used as an effective drug for the prevention and treatment of postinfarct cardiac dysfunctions.