We report the first measurement of the average of the electron-proton and positron-proton elastic scattering cross sections. This lepton charge-averaged cross section is insensitive to the leading ...effects of hard two-photon exchange, giving more robust access to the proton's electromagnetic form factors. The cross section was extracted from data taken by the OLYMPUS experiment at DESY, in which alternating stored electron and positron beams were scattered from a windowless gaseous hydrogen target. Elastic scattering events were identified from the coincident detection of the scattered lepton and recoil proton in a large-acceptance toroidal spectrometer. The luminosity was determined from the rates of Møller, Bhabha, and elastic scattering in forward electromagnetic calorimeters. The data provide some selectivity between existing form factor global fits and will provide valuable constraints to future fits.
The article presents a method for forming the trajectory of an automatic lawnmower, describes the architecture of mobile robot control and suggests a method for estimating the productivity of its ...work.
The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R_{2γ}, a direct measure of the contribution of hard two-photon ...exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved gas electron multiplier and multiwire proportional chamber detectors at 12°, as well as symmetric Møller or Bhabha calorimeters at 1.29°. A total integrated luminosity of 4.5 fb^{-1} was collected. In the extraction of R_{2γ}, radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of R_{2γ}, presented here for a wide range of virtual photon polarization 0.456<ε<0.978, are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.
PANDA Phase One Liu, Z.; Liu, B.; Shen, X. ...
The European physical journal. A, Hadrons and nuclei,
06/2021, Letnik:
57, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future ...antiProton ANnihilations at DArmstadt (PANDA or
P
¯
ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton–nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model,
e.g.
through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the
Phase One
setup. The physics programme that is achievable during Phase One is outlined in this paper.
A
bstract
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized ...protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos (
ϕ−ϕ
S
) modulations provide evidence for a sizable worm-gear (II) distribution,
g
1
T
q
x
p
T
2
. Most of the other modulations are found to be consistent with zero with the notable exception of large sin (
ϕ
S
) modulations for charged pions and
K
+
.
Azimuthal single-spin asymmetries of leptoproduced pions and charged kaons were measured on a transversely polarized hydrogen target. Evidence for a naive-T-odd, transverse-momentum-dependent parton ...distribution function is deduced from nonvanishing Sivers effects for pi(+), pi(0), and K(+/-), as well as in the difference of the pi(+) and pi(-) cross sections.
The exclusive charmonium production process in p¯p annihilation with an associated π0 meson p¯p→J/ψπ0 is studied in the framework of QCD collinear factorization. The feasibility of measuring this ...reaction through the J/ψ→e+e− decay channel with the AntiProton ANnihilation at DArmstadt (P¯ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the p¯p→π+π−π0 and p¯p→J/ψπ0π0 reactions are performed with PandaRoot, the simulation and analysis software framework of the P¯ANDA experiment. It is shown that the measurement can be done at P¯ANDA with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.
Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. The ...dependence of the cross section on the azimuthal angles of the target polarization (ϕS) and the produced hadron (ϕ) is found to have a substantial sin(ϕ+ϕS) modulation for the production of π+, π− and K+. This Fourier component can be interpreted in terms of non-zero transversity distribution functions and non-zero favored and disfavored Collins fragmentation functions with opposite sign. For π0 and K− production the amplitude of this Fourier component is consistent with zero.
The Autonomous Non-Commercial Organization “Minority Report” Research Center carried out a complex all-Russian monitoring of accessibility of higher education for students with disabilities in 1/3 of ...state universities (165 universities in 51 regions). The authors explored the issue from the point of view of organizations offering services in higher education (universities) as well as from the point of view of their customers (disabled students and their parents) and completed the picture with the data obtained through monitoring and participant observation; this enabled the authors to reveal the main problems that students with disabilities experience in getting higher education – in the stages of career guidance, university admission, studying at university and further employment. For instance, the authors point out to the legal restriction ‘one university – one profession’ referring to admission quotas for students with disabilities; problems with getting documents required for university application; low accessibility of educational environment and insufficient supply of special teaching devices; low accessibility of university websites etc. The authors propose the following specific measures for raising the accessibility of higher education for the disabled: introducing changes to legal acts restricting the opportunities of the disabled in higher education; changing the practices in organizations responsible for medical and social assessment in how they provide documents required for university application; expanding the services offered by resource and training centers; introducing a unified standard for university websites in sections referring to disability services, etc.
This project was supported by state grant funds, Executive Order of the President of the Russian Federation issued on April 01, 2015 #79-рп, and on the basis of the contest carried out by the All-Russian Non-Governmental Organization «Liga Zdorovya Natsii».
АНО «НИЦ «Особое мнение» провела комплексный всероссийский мониторинг доступности высшего профессионального образования для инвалидов и лиц с ограниченными возможностями здоровья (ОВЗ), охвативший треть государственных вузов РФ (165 вузов в 51 регионе). Авторы изучили данный вопрос с точки зрения организаций, предоставляющих услуги высшего образования (вузы), потребителя этих услуг (студенты-инвалиды и их родители) и дополнили полученную картину данными мониторинга и включенного наблюдения, что позволило выделить основные блоки проблем на пути получении инвалидами и лицами с ОВЗ высшего образования на этапах профориентации, поступления в вуз, непосредственно обучения и дальнейшего трудоустройства. В частности, исследователи указывают на законодательное ограничение «один вуз – одна специальность» для поступления инвалидов по квоте, проблемы при получении инвалидами необходимых для поступления в вуз документов, недостаточную обеспеченность вузов элементами доступной среды и специальными техническими средствами обучения инвалидов, низкую информативность сайтов вузов и пр. Также авторы предлагают конкретные шаги по повышению доступности высшего образования для инвалидов, например, внесение поправок в законодательные акты, ограничивающие возможности инвалидов в сфере высшего образования, изменение практики работы органов медико-социальной экспертизы (МСЭ) в части предоставления необходимых для поступления в вуз документов, дополнение функционала ресурсных учебно-методических центров (РУМЦ) инженерно-технической и кадровой составляющей, введение единого стандарта раздела сайтов вузов, посвященного обучению инвалидов, и т. д.
PDF
