Novel Measurement of the Neutron Magnetic Form Factor from A=3 Mirror Nuclei.

The electromagnetic form factors of the proton and neutron encode information on the spatial structure of their charge and magnetization distributions. While measurements of the proton are relatively straightforward, the lack of a free neutron target makes measurements of the neutron's electromagnetic structure more challenging and more sensitive to experimental or model-dependent uncertainties. Various experiments have attempted to extract the neutron form factors from scattering from the neutron in deuterium, with different techniques providing different, and sometimes large, systematic uncertainties. We present results from a novel measurement of the neutron magnetic form factor using quasielastic scattering from the mirror nuclei ^{3}H and ^{3}He, where the nuclear effects are larger than for deuterium but expected to largely cancel in the cross-section ratios. We extracted values of the neutron magnetic form factor for low-to-modest momentum transfer, 0.6

New Measurements of the Beam-Normal Single Spin Asymmetry in Elastic Electron Scattering over a Range of Spin-0 Nuclei.

We report precision determinations of the beam-normal single spin asymmetries (A_{n}) in the elastic scattering of 0.95 and 2.18 GeV electrons off ^{12}C, ^{40}Ca, ^{48}Ca, and ^{208}Pb at very forward angles where the most detailed theoretical calculations have been performed. The first measurements of A_{n} for ^{40}Ca and ^{48}Ca are found to be similar to that of ^{12}C, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with Z≤20. We also report A_{n} for ^{208}Pb at two new momentum transfers (Q^{2}) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the Z≤20 nuclei. These data confirm our basic understanding of the underlying dynamics that govern A_{n} for nuclei containing ≲50 nucleons, but point to the need for further investigation to understand the unusual A_{n} behavior discovered for scattering off ^{208}Pb.

Determination of the

We report the first measurement of the parity-violating elastic electron scattering asymmetry on ^{27}Al. The ^{27}Al elastic asymmetry is A_{PV}=2.16±0.11(stat)±0.16(syst) ppm, and was measured at ⟨Q^{2}⟩=0.02357±0.00010 GeV^{2}, ⟨θ_{lab}⟩=7.61°±0.02°, and ⟨E_{lab}⟩=1.157 GeV with the Q_{weak} apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the ^{27}Al neutron radius R_{n}=2.89±0.12 fm was determined using a many-models correlation technique. The corresponding neutron skin thickness R_{n}-R_{p}=-0.04±0.12 fm is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the ^{27}Al weak radius R_{w}=3.00±0.15 fm, and the weak skin thickness R_{wk}-R_{ch}=-0.04±0.15 fm. The weak form factor at this Q^{2} is F_{wk}=0.39±0.04.

Precision Determination of the Neutral Weak Form Factor of

We report a precise measurement of the parity-violating (PV) asymmetry A_{PV} in the elastic scattering of longitudinally polarized electrons from ^{48}Ca. We measure A_{PV}=2668±106(stat)±40(syst) parts per billion, leading to an extraction of the neutral weak form factor F_{W}(q=0.8733 fm^{-1})=0.1304±0.0052(stat)±0.0020(syst) and the charge minus the weak form factor F_{ch}-F_{W}=0.0277±0.0055. The resulting neutron skin thickness R_{n}-R_{p}=0.121±0.026(exp)±0.024(model) fm is relatively thin yet consistent with many model calculations. The combined CREX and PREX results will have implications for future energy density functional calculations and on the density dependence of the symmetry energy of nuclear matter.

Accurate Determination of the Neutron Skin Thickness of

We report a precision measurement of the parity-violating asymmetry A_{PV} in the elastic scattering of longitudinally polarized electrons from ^{208}Pb. We measure A_{PV}=550±16(stat)±8(syst) parts per billion, leading to an extraction of the neutral weak form factor F_{W}(Q^{2}=0.00616 GeV^{2})=0.368±0.013. Combined with our previous measurement, the extracted neutron skin thickness is R_{n}-R_{p}=0.283±0.071 fm. The result also yields the first significant direct measurement of the interior weak density of ^{208}Pb: ρ_{W}^{0}=-0.0796±0.0036(exp)±0.0013(theo) fm^{-3} leading to the interior baryon density ρ_{b}^{0}=0.1480±0.0036(exp)±0.0013(theo) fm^{-3}. The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.

Precision Measurement of the Beam-Normal Single-Spin Asymmetry in Forward-Angle Elastic Electron-Proton Scattering.

A beam-normal single-spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable related to the imaginary part of the two-photon exchange process. We report a 2% precision measurement of the beam-normal single-spin asymmetry in elastic electron-proton scattering with a mean scattering angle of θ_{lab}=7.9° and a mean energy of 1.149 GeV. The asymmetry result is B_{n}=-5.194±0.067(stat)±0.082 (syst) ppm. This is the most precise measurement of this quantity available to date and therefore provides a stringent test of two-photon exchange models at far-forward scattering angles (θ_{lab}→0) where they should be most reliable.

Unique Access to u-Channel Physics: Exclusive Backward-Angle Omega Meson Electroproduction.

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 Q^{2} values of 1.60, 2.45 GeV^{2}, at W=2.21 GeV. The results of our pioneering -u≈-u_{min} 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 Q^{2}=2.45 GeV^{2}, the observed dominance of σ_{T} over σ_{L}, 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.

Separated response function ratios in exclusive, forward π(±) electroproduction.

The study of exclusive π(±) electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio RL=σL(π-)/σL(π+) is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of RT=σT(π-)/σT(π+) from unity at small -t, to 1/4 at large -t, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks. Furthermore, the mentioned ratios may show an earlier approach to perturbative QCD than the individual cross sections. We have performed the first complete separation of the four unpolarized electromagnetic structure functions above the dominant resonances in forward, exclusive π(±) electroproduction on the deuteron at central Q(2) values of 0.6, 1.0, 1.6 GeV(2) at W=1.95 GeV, and Q(2)=2.45 GeV(2) at W=2.22 GeV. Here, we present the L and T cross sections, with emphasis on RL and RT, and compare them with theoretical calculations. Results for the separated ratio RL indicate dominance of the pion-pole diagram at low -t, while results for RT are consistent with a transition between pion knockout and quark knockout mechanisms.

First determination of the weak charge of the proton.

The Q(weak) experiment has measured the parity-violating asymmetry in ep elastic scattering at Q(2)=0.025(GeV/c)(2), employing 145 µA of 89% longitudinally polarized electrons on a 34.4 cm long liquid hydrogen target at Jefferson Lab. The results of the experiment's commissioning run, constituting approximately 4% of the data collected in the experiment, are reported here. From these initial results, the measured asymmetry is A(ep)=-279±35 (stat) ± 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in ep scattering. The small Q(2) of this experiment has made possible the first determination of the weak charge of the proton Q(W)(p) by incorporating earlier parity-violating electron scattering (PVES) data at higher Q(2) to constrain hadronic corrections. The value of Q(W)(p) obtained in this way is Q(W)(p)(PVES)=0.064±0.012, which is in good agreement with the standard model prediction of Q(W)(p)(SM)=0.0710±0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES+APV analysis reveals the neutron's weak charge to be Q(W)(n)(PVES+APV)=-0.975±0.010.

Measurement of the parity-violating asymmetry in inclusive electroproduction of π- near the Δ0 resonance.

The parity-violating (PV) asymmetry of inclusive π- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasifree photoproduction off the neutron via the Δ0 resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant d(Δ)- that characterizes the parity-violating γNΔ coupling. Zhu et al. calculated d(Δ)- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A(γ)-=-5.2 to +5.2 ppm. The measurement performed in this work leads to A(γ)-=-0.36±1.06±0.37±0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to V(ud)/V(us). The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-Δ axial transition form factors using PV electron scattering.

Transverse beam spin asymmetries at backward angles in elastic electron-proton and quasielastic electron-deuteron scattering.

We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108°) for Q² = 0.22 GeV²/c² and 0.63 GeV²/c² at beam energies of 362 and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single-photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (πN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasistatic deuterium approximation, and is also in agreement with theory.

Microcoulomb (0.7 ± [Formula: see text] µC) laser plasma accelerator on OMEGA EP.

Laser-plasma accelerators (LPAs) driven by picosecond-scale, kilojoule-class lasers can generate particle beams and x-ray sources that could be utilized in experiments driven by multi-kilojoule, high-energy-density science (HEDS) drivers such as the OMEGA laser at the Laboratory for Laser Energetics (LLE) or the National Ignition Facility at Lawrence Livermore National Laboratory. This paper reports on the development of the first LPA driven by a short-pulse, kilojoule-class laser (OMEGA EP) connected to a multi-kilojoule HEDS driver (OMEGA). In experiments, electron beams were produced with electron energies greater than 200 MeV, divergences as low as 32 mrad, charge greater than 700 nC, and conversion efficiencies from laser energy to electron energy up to 11%. The electron beam charge scales with both the normalized vector potential and plasma density. These electron beams show promise as a method to generate MeV-class radiography sources and improved-flux broadband x-ray sources at HEDS drivers.

Enhancements in laser-generated hot-electron production via focusing cone targets at short pulse and high contrast.

We report on the increase in the accelerated electron number and energy using compound parabolic concentrator (CPC) targets from a short-pulse (∼150 fs), high-intensity (>10^{18} W/cm^{2}), and high-contrast (∼10^{8}) laser-solid interaction. We report on experimental measurements using CPC targets where the hot-electron temperature is enhanced up to ∼9 times when compared to planar targets. The temperature measured from the CPC target is 〈T_{e}〉=4.4±1.3 MeV. Using hydrodynamic and particle in cell simulations, we identify the primary source of this temperature enhancement is the intensity increase caused by the CPC geometry that focuses the laser, reducing the focal spot and therefore increasing the intensity of the laser-solid interaction, which is also consistent with analytic expectations for the geometrical focusing.

Strange quark contributions to parity-violating asymmetries in the backward angle G0 electron scattering experiment.

We have measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2=0.22 and 0.63 GeV2. They are sensitive to strange quark contributions to currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of approximately < 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. We also present the first measurement of anapole moment effects in the axial-vector current at these four-momentum transfers.

A qualitative evaluation of patients' experiences of an enhanced recovery programme for colorectal cancer.

AIM: We explored the patients' views and experiences of surgery for colorectal cancer within an enhanced recovery programme (ERP). METHOD: Semi-structured home interviews were performed within 6 weeks of hospital discharge with participants of a randomized trial comparing laparoscopically assisted surgery with open surgery for colorectal cancer within an ERP. Interviews were tape-recorded, transcribed and analysed using qualitative techniques of constant comparison based upon grounded theory. RESULTS: Interviewees (n = 22) had similar baseline characteristics and clinical outcomes to participants in the full trial. Many participants were pleased to be discharged quickly and they considered that being in their own home-improved recovery because it allowed them to choose how and when to undertake daily activities rather than following the hospital routine. Some participants (n = 9) were less satisfied with the process, and the reasons for this were related to complications requiring readmission or needing to contact a health professional for information after discharge. CONCLUSION: Although many participants reported benefits from an ERP, the study highlighted areas for improvement. In particular participants reported the need for better access to information and specialist advice in the early days after hospital discharge.

A modified lateral approach to parastomal hernia repair.

AIM: Parastomal hernia commonly occurs following the formation of a stoma. This is a review of parastomal hernia repair using a modified lateral approach to access the defect. PATIENTS/METHODS: A case series of 17 patients, with a median age of 65, who underwent parastomal hernia repair via a lateral approach over a five year period, is presented. RESULTS: Of the 17 repairs, there were four minor complications in the form of a superficial cellulitis and conservatively managed ileus. In total there were four recurrences, though only one recurrence occurred in 11 cases after slight modification of the technique. The period of follow-up ranged from 6 to 60 months. DISCUSSION: The lateral approach is a viable option for repair of parastomal hernia. It does not necessitate a laparotomy or relocation of the stoma.

X-ray analysis methods for sources from self-modulated laser wakefield acceleration driven by picosecond lasers.

A versatile set of methods for analyzing x-ray energy spectra and photon flux has been developed for laser plasma accelerator experiments driven by picosecond lasers. Forward fit provides extrapolated broad energy spectrum measurements, while Ross pair and differential average transmission analysis provide directly measured data points using a particular diagnostic. Combining these methods allows the measurement of x-ray energy spectra with improved confidence. We apply the methods to three diagnostics (filter wheel, stacked image plate spectrometer, and step wedge), each sensitive to a different region of x-ray energies (<40 keV, 35-100 keV, and 60-1000 keV, respectively), to characterize the analysis methods using laser-driven bremsstrahlung x-rays. We then apply the methods to measure three x-ray mechanisms, betatron, inverse Compton scattering, and bremsstrahlung, driven by a laser plasma accelerator. The analysis results in the measurement of x-ray energy spectra ranging from 10 keV to 1 MeV with peak flux greater than 1010 photons/keV/Sr. The combined analysis methods provide a robust tool to accurately measure broadband x-ray sources (keV to MeV) driven by laser plasma acceleration with picosecond, kilojoule-class lasers.

Assessing quality of life in patients with colorectal cancer: an update of the EORTC quality of life questionnaire.

The European Organisation for Research and Treatment of Cancer (EORTC) has a portfolio of questionnaire modules to supplement the QLQ-C30 to assess patient reported outcomes in cancer clinical trials. This study updated the module for colorectal cancer. A review of the literature identified 20 articles that used the EORTC colorectal module. Eight papers did not report data from scales addressing sexual function and 8 added additional scales to assess ano-rectal function. Interviews with patients (n=79) and professionals (n=11) informed item selection, reduction and modification. A new 29 item module was devised and further patient interviews (n=120) examined its format and content validity. Patients found the new module acceptable with relevant content. The new module, the EORTC QLQ-CR29, is hypothesised as containing 6 scales and 11 single items. An international study examining its clinical and psychometric validity will be performed.

Healing by primary versus secondary intention after surgical treatment for pilonidal sinus.

BACKGROUND: Pilonidal sinus arises in the hair follicles in the buttock cleft at the bottom of the backbone. The estimated incidence is 26 per 100,000, people, affecting men twice as often as women. The mean age of presentation is 21 years (men) and 19 years (women) respectively.Pilonidal sinus results in chronic discharging wounds that cause pain and impact upon quality of life and social function. These sinuses may become infected and present as acute abscesses. Management of these abscesses is uncontroversial and revolves around incision and drainage, however, the mode of surgical management of the chronic discharging sinus is debatable. Surgical strategies traditionally centre on excision of the sinus tracts followed by primary closure and healing by primary intention or leaving the wound open to heal by secondary intention. There is uncertainty as to whether open or closed surgical management is more effective. OBJECTIVES: To determine the relative effects of open compared with closed surgical treatment for pilonidal sinus on the outcomes of time to healing, infection and recurrence rate. SEARCH STRATEGY: We sought relevant trials from the Wounds Group Specialised Register (Searched 13/6/07); The Cochrane Central Register of Controlled Trials (CENTRAL) (2007, Issue 2); Ovid MEDLINE (1950 - May Week 5 200& ); Ovid EMBASE (1980 - 2007 Week 23); Ovid CINAHL (1982 - June Week 2 2007). We checked the bibliographies of review and primary articles for relevant studies and contacted authors of all included studies. SELECTION CRITERIA: All randomised controlled trials (RCTs) evaluating open with closed surgical treatment for pilonidal sinus. Exclusion criteria were: non-RCTs; children aged younger than 14 years and studies of pilonidal abscess. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, data extraction and methodological quality assessment of trials were conducted independently by two review authors. Data from eligible studies were recorded using data extraction forms and any disagreements were referred to a third review author. Results were presented using mean differences for continuous outcomes and relative risk with 95% confidence intervals for dichotomous outcomes. MAIN RESULTS: Eighteen studies were included (1573 patients). Twelve RCTs compared open healing with primary closure, 10 of which used midline closure and 2 trials used off-midline closure. Six studies compared midline and off-midline closure. Open compared with closed techniques: Evidence suggested more rapid healing after primary closure although there was no difference in the infection rate after wound closure. Recurrence was less likely to occur after open healing (RR 0.42; 95% CI 0.26 to 0.66) suggesting a 58% lower risk of recurrence after open wound healing compared with primary closure. Patients returned to work earlier after primary closure (WMD 10.48 days 95% CI 5.75 to 15.21 days). There was no difference between the two groups for other complications and length of stay. There were few useable data on cost, patient satisfaction and pain. Closed midline compared with closed off-midline: there was good evidence of slower healing, higher rates of infection (RR 4.70; 95% CI 1.93 to 11.45), higher rates of recurrence (Peto OR 4.95; 95% CI 2.18 to 11.24) and other complications (RR 8.94; 95% CI 2.10 to 38.02) after midline primary closure compared with off-midline closure techniques. AUTHORS' CONCLUSIONS: No clear benefit was shown for surgical management by primary closure or open healing by secondary intention. A clear benefit was shown for off-midline closure rather than midline closure after pilonidal sinus surgery. Off-midline closure should be the standard management when primary closure is the desired surgical option.

The accuracy of clinical data: a comparison between central and local data collection.

BACKGROUND: The recent liberalisation of public access to information, including surgical performance, emphasises the necessity for accurate data collection. The Information and Statistics Division of the Scottish Executive (ISD) collect such data for each patient episode, but there is concern about the reliability of this information compared with that collected in local surgical departmental audit. AIM: To determine if diagnostic and operative details were consistent between local audited and national non-audited data sets. METHODS: Three surgical units comprising eight consultants were studied. Epidemiological, diagnostic and operative data for each consultant were accessed from the eScrips Internet resource (ISD Data) and from the departmental database. A unique patient number and date of birth matched individual patient episodes and the correlation between datasets graded for accuracy and consistency. RESULTS: 8375 individual data entries were recorded (ISD 4642, local databases 3733). 3402 pairs, 6408 (76.5%) of the total, matched accurately. 742 (16%) of the ISD entries were duplicates, and in 21% of unpaired entries the wrong consultant was recorded. Overall a clinically acceptable match occurred in 86.9% of paired entries for diagnosis and 84.0% for operation. The highest match with ISD data for diagnosis (88.8%) and operation (91.8%) occurred in the unit which holds a weekly audit meeting to validate information. DISCUSSION: There are significant discrepancies in surgical data between the local audit databases and central data. There is significant duplication of entries and inaccurate consultant allocation in ISD data. The promulgation of inaccurate information could threaten reputation or career and clinicians should play a more active role in ensuring clinical data are correct.