Photoproduction of K+K− meson pairs on the proton

The exclusive reaction γp→pK+K− was studied in the photon energy range 3.0–3.8  GeV and momentum transfer range 0.6<−t<1.3  GeV2. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately 20  pb−1. The reaction was isolated by detecting the K+ and the proton in CLAS, and reconstructing the K− via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the ϕ meson in the P wave, evidence for S−P interference was found. The differential production cross sections dσ/dt for individual waves in the mass range of the ϕ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the t-dependent cross section of the S-wave contribution to the elastic K+K− photoproduction has been measured

Observation of beam spin asymmetries in the process ep→e^{'}π^{+}π^{-}X with CLAS12

The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e(x), which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function G_{1}^{⊥}. A clear sign change is observed around the ρ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark

Measurement of the neutron electric form factor at Q²=0.8 (GeV/c)²

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Measurement of the Neutron electric form factor at Q2=0.8 2(GeV\\c)

Nucleon form factors allow a sensitive test for models of the nucleon. Recent experiments utilising polarisation observables have resulted, for the first time, in a model-independent determination of the neutron electric form factor GnE. This method employed an 80% longitudinally polarised, high intensity (10 uA) electon beam (883 MeV) that was quasi-elastically scattered off a liquid deuterium target in the reaction D (e, en)p. A neutron polarimeter was designed and installed to measure the ratio of transverse-to-longitudinal polarisation using neutron scattering asymmetries. This ratio allowed a determination of the neutron elastic form factor, GnE, free of the previous large systematic uncertainties associated with the deuterium wave function. The experiment took place in the A1 experimental hall at MAMI taking advantage of a high resolution magnetic spectrometer. A detailed investigation was carried out into the performance of the neutron polarimeter

Transcutaneous Electrical Stimulation and Postoperative Total Knee Arthroplasty Pain

OBJECTIVE: To determine the efficacy of the Synaptic 2000 in reducing total knee replacement postoperative pain in a prospective randomized controlled trial.DESIGN: Patients were prospectively randomly assigned to two groups, one receiving seven days of transcutaneous electrical stimulation (TES) therapy in addition to standard postoperative care, and the other receiving standard postoperative care. Both groups received postoperative patient-controlled analgesia and were switched to oral opiates.SETTING: Patients were treated at a university teaching hospital for elective primary unilateral total knee replacement.PATIENTS: All patients consented to enter the study. All had primary osteoarthritis. Fifteen patients were entered into each arm of the study, and all patients completed the study. The mean age of patients was 64 years for treatment and 71 years for controls.OUTCOME MEASURES: Outcome measures were analgesic consumption, return of knee range of motion and score on a visual analogue pain scale.RESULTS: No significant differences were noted in postoperative analgesic use, knee range of motion, length of stay or visual analogue pain scale score. Mean total analgesic use of morphine was 148 mg in the TES group and 108 mg in the control group. The TES group mean knee range of motion on postoperative day 7 was 75.3°; it was 73.6° in the control group. Group mean length of stay was 9.5 days in the TES group and 8.3 days in the control group.Peer Reviewe

Pixel-based tracking detectors for a Low Q2 Tagger at EIC -- status report

The design of pixel-based tracking detectors for a Low Q2 Tagger in the Far Backward region of the ePIC detector at EIC is presented. The physics case is outlined, together with estimates of rates and resolutions, and the current design based on Timepix4 technology is introduced.Comment: Fix author nam

The focusing disc DIRC for the PANDA experiment at FAIR

The Focusing Disc DIRC is a novel detector concept for particle identification based on the detection of internally-reflected Cherenkov light. A thin synthetic silica disc of 1 m radius will be used as radiator and for light transportation. At the rim LiF bars are foreseen to passively correct for dispersion. Focusing elements map the angles of the propagating photons to spatial positions on the focal plane covered with position sensitive photon detection devices. This novel 2D(+1t) detector concept will contribute to the outstanding particle identification performance of the general purpose PANDA detector. The aims of the PANDA experiment are to address fundamental questions of the strong force, to explore the structure of the nucleon and to search for new matter. The technical design, the current status of the development and recent results from prototype test experiments for the Focusing Disc DIRC are presented

Neutron polarisation transfer, Cx′, in π+ photoproduction off the proton, d(γ⊙,n→π+)nspec

We report a first measurement of the double-polarisation observable, Cx′, in π+ photoproduction off the proton. The double-polarisation observable represents the transfer of polarisation from a circularly polarised photon beam to the recoiling neutron. The MAMI circularly polarised photon beam impinged on a liquid deuterium target cell, with reaction products detected in the Crystal Ball calorimeter. Ancillary apparatus surrounding the target provided tracking, particle identification and determination of recoil nucleon polarisation. The Cx′ observable is determined for photon energies 800-1400 MeV, providing new constraints on models aiming to elucidate the spectrum and properties of nucleon resonances. This is the first determination of any polarisation observable from the beam-recoil group of observables for this reaction. Inclusion of the new data in the database of the SAID partial wave analysis shifted the solution to a new global minima which, not only gives better agreement with the current data, but also improves the description of a range of other single and double polarisation observables for charged pion photoproduction