Neutron skin of (208)pb from coherent pion photoproduction.

Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.) fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.) fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.) fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of (208)Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.

Measurement of the 1H(γ, p)π0 reaction using a novel nucleon spin polarimeter.

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon. The measurement pioneers a novel polarimetry technique, which can be applied to many other nuclear and hadron physics experiments. The commissioning reaction of 1H(γ, p)π0 in the range 0.4

Photoproduction of π0 mesons off neutrons in the nucleon resonance region.

Precise angular distributions have been measured for the first time for the photoproduction of π0 mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasifree protons bound in the deuteron to the results for free protons and then applied as a correction to the quasifree neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 and 1.4 GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.

Narrow structure in the excitation function of η photoproduction off the neutron.

The photoproduction of η mesons off nucleons bound in 2H and 3He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the η→2γ and η→3π0 decays and the recoil nucleons were detected with an almost 4π electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of γn→nη. The results from the two measurements are consistent, taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are W=(1670±5) MeV and Γ=(30±15) MeV. For the first time precise results for the angular dependence of this structure have been extracted.

Measurement of the neutron F2 structure function via spectator tagging with CLAS.

We report on the first measurement of the F(2) structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲100 MeV/c and their angles to ≳100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F(2)(n) data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65

Measurement of single- and double-spin asymmetries in deep inelastic pion electroproduction with a longitudinally polarized target.

We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes ϕ have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q2. A significant nonzero sin2ϕ single spin asymmetry was observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton.

Absorption of the ω and ϕ mesons in nuclei.

Because of their long lifetimes, the ω and ϕ mesons are the ideal candidates for the study of possible modifications of the in-medium meson-nucleon interaction through their absorption inside the nucleus. During the E01-112 experiment at the Thomas Jefferson National Accelerator Facility, the mesons were photoproduced from 2H, C, Ti, Fe, and Pb targets. This Letter reports the first measurement of the ratio of nuclear transparencies for the e+e- channel. The ratios indicate larger in-medium widths compared with what have been reported in other reaction channels. The absorption of the ω meson is stronger than that reported by the CBELSA-TAPS experiment and cannot be explained by recent theoretical models.

Inventories of fallout 210Pb and 137Cs radionuclides in moorland and woodland soils around Edinburgh urban area (UK).

Inventories of fallout (210)Pb and (137)Cs have been measured in moorland and woodland soils around the Edinburgh urban area, using a high purity germanium detector. The (210)Pb inventories in moorland soils were relatively uniform, with a mean value of 2520+/-270Bqm(-2). The mean (137)Cs inventory in moorland soils varied greatly from 1310 to 2100Bqm(-2), with a mean value of 1580+/-310Bqm(-2). The variability was ascribed mainly to the non-uniform distribution of fallout Chernobyl (137)Cs. The mean (210)Pb and (137)Cs inventories in woodland canopy soils were found to be 3630+/-380Bqm(-2) and 2510+/-510Bqm(-2), respectively. At sites for which both moorland and woodland data were available, the mean inventories provided fairly similar average enhancements of (47+/-7)% and (46+/-18)% of (210)Pb and (137)Cs under woodland canopy soils relative to open grassland soils, respectively. The enhancement factors are broadly in line with other independent findings in literature. Enhancement of both (210)Pb and (137)Cs in woodland soils relative to moorland soils is, in part, due to deposition by impaction during air turbulence, wash-off, gravitational settling and deposition during leaf senescence. Results of this study suggest that these processes affect both (210)Pb and (137)Cs carrier aerosols in a similar way.

Treatment-emergent behavioural side effects with selective serotonin re-uptake inhibitors in adults with learning disabilities.

Selective serotonin re-uptake inhibitors are widely used for the treatment of depression suffered by adults with learning disabilities. However, the presentation, time of onset and prevalence of treatment emergent symptoms, have not been extensively studied in adults with learning disabilities. The aim of this study was to determine these aspects of treatment. The study design involved retrospective analysis of case notes of all adults with learning disabilities treated with either fluoxetine or paroxetine for depression. During 31% of treatment episodes, patients suffered treatment emergent symptoms during treatment with either selective serotonin re-uptake inhibitor (SSRI). These symptoms subsided on discontinuation of the SSRI. The common emergent symptoms in this group were elevated mood (39%), decreased sleep (35%), hyperactivity (30%), overtalkativeness (26%), agitation (24%) and aggression (37%). In 20% symptoms developed within 1 month and in 67% within 7 months of starting treatment with a SSRI. There were no significant differences noted in the frequency and nature of treatment emergent symptoms between fluoxetine and paroxetine. Few guidelines, if any, exist for initiating and continuing antidepressant treatment for therapeutic or prophylactic use in this patient population. Close monitoring of efficacy and tolerability, including treatment emergent psychiatric symptoms is warranted. Copyright 2001 John Wiley & Sons, Ltd.

Epilepsy in adults with learning disabilities.

Epilepsy is a common problem of adults with learning disabilities. Despite the high prevalence there have been few studies of the epilepsy suffered by adults with learning disabilities. The findings of a Leicestershire study are that multiple seizure types are a common presentation, and that for many (75%) the seizures remain refractory to treatment. Those who suffer tonic-clonic seizures are most likely to achieve remission, whereas for those with simple or complex partial seizures the prognosis is poor. For a significant proportion, status epilepticus, emergency admission to hospital and injuries occur on a regular basis.

A naturalistic study of the use of vigabatrin, lamotrigine and gabapentin in adults with learning disabilities.

Epilepsy is a common condition in people with learning disabilities with many patients continuing to suffer from seizures despite antiepileptic drug (AED) treatment. Although the advent of newer AEDs offers hope for better treatment, there is a need to compare the efficacy of each new AED in adults with both drug-resistant epilepsy and learning disabilities. This retrospective casenote study involves the analysis of the outcome for those adults with learning disabilities treated with either vigabatrin, lamotrigine or gabapentin. The information obtained from the casenote analysis was used to both compare the efficacies of the three drugs and also the side-effects and drop-out rates, including reasons for drop-out. The total number of patients involved was 51 who underwent 71 treatment episodes. All three AEDs had similar efficacies. Although vigabatrin was found to be associated with a higher incidence of behaviour problems, behaviour problems occurred with the other drugs as well. Lamotrigine caused increased seizures in 24% of patients, especially when prescribed at a higher dose. Gabapentin appeared to be associated with fewer serious side-effects.

A follow-up study of adults with learning disabilities and epilepsy.

A programme to review the drug treatment of 215 adults with epilepsy and learning disabilities occurred in Leicestershire between 1982 and 1985. In 1997, a Leicestershire-wide study of epilepsy suffered by adults with learning disabilities was undertaken. The study sought information about many aspects of the epilepsy including the prescribing of medicines. One hundred and thirty-eight adults were common to both studies. A greater proportion was suffering active epilepsy in 1997 than in 1985. The deterioration in seizure control occurred despite an increase in polypharmacy, the introduction of new antiepileptic drugs and in some cases increases in dosage.

Drug administration in day centres for people with learning disabilities.

A study was made of the problems associated with the need to administer medicines at day centres for people with learning disabilities. In Leicestershire, 167 (13%) of 1317 people with learning disabilities who attended day centres required the administration of medicines. The percentage of attenders requiring drug administration varied from day centre to day centre (minimum 4%, maximum 23%). Antiepileptics were the most commonly administered drugs, followed by antipsychotics. The administration of medicines took up a significant amount of time for senior members of the day centre staff and had a great potential for errors. In only 32 cases was it deemed essential that the drug administration occurred at the day centre.

Pharmaceutical services to the mentally ill.

This paper provides an overview of the pharmaceutical services to the mentally ill within the community, the District General Hospital, Psychiatric Hospital, Regional Secure Unit, Special Hospital and Prison. With an overall picture of underfunding and underprovision a number of models of service are proposed for the future.

Measurement of direct f0(980) photoproduction on the proton.

We report on the results of the first measurement of exclusive f_{0}(980) meson photoproduction on protons for E_{gamma}=3.0-3.8 GeV and -t=0.4-1.0 GeV2. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the pi;{+}pi;{-} channel by performing a partial wave analysis of the reaction gammap-->ppi;{+}pi;{-}. Clear evidence of the f_{0}(980) meson was found in the interference between P and S waves at M_{pi;{+}pi;{-}} approximately 1 GeV. The S-wave differential cross section integrated in the mass range of the f_{0}(980) was found to be a factor of about 50 smaller than the cross section for the rho meson. This is the first time the f_{0}(980) meson has been measured in a photoproduction experiment.

Search for the photoexcitation of exotic mesons in the pi+pi+pi- system.

A search for exotic mesons in the pi;{+}pi;{+}pi;{-} system photoproduced by the charge exchange reaction gammap-->pi;{+}pi;{+}pi;{-}(n) was carried out by the CLAS Collaboration at Jefferson Lab. A tagged-photon beam with energies in the 4.8 to 5.4 GeV range, produced through bremsstrahlung from a 5.744 GeV electron beam, was incident on a liquid-hydrogen target. A partial wave analysis was performed on a sample of 83 000 events, the highest such statistics to date in this reaction at these energies. The main objective of this study was to look for the photoproduction of an exotic J;{PC}=1;{-+} resonant state in the 1 to 2 GeV mass range. Our partial wave analysis shows production of the a_{2}(1320) and the pi_{2}(1670) mesons, but no evidence for the a_{1}(1260), nor the pi_{1}(1600) exotic state at the expected levels. An upper limit of 13.5 nb is determined for the exotic pi_{1}(1600) cross section, less than 2% of the a_{2}(1320) production.

Precise measurement of the neutron magnetic form factor G(M)n in the few-GeV2 region.

The neutron elastic magnetic form factor was extracted from quasielastic electron scattering on deuterium over the range Q;{2}=1.0-4.8 GeV2 with the CLAS detector at Jefferson Lab. High precision was achieved with a ratio technique and a simultaneous in situ calibration of the neutron detection efficiency. Neutrons were detected with electromagnetic calorimeters and time-of-flight scintillators at two beam energies. The dipole parametrization gives a good description of the data.

Beam-helicity asymmetries in double-pion photoproduction off the proton.

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels gamma[over -->]p-->pi(+)pi(0)n, gamma[over -->]p-->pi(0)pi(0)p, and gamma[over -->]p-->pi(+)pi(-)p. The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of pi(0) mesons were detected in a 4pi electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.