165 research outputs found
The Drell-Yan process with pions and polarized nucleons
No full textThe Drell-Yan process provides important information on the internal struc- ture of hadrons including transverse momentum dependent parton distribution functions (TMDs). In this work we present calculations for all leading twist structure functions de- scribing the pion induced Drell-Yan process. The non-perturbative input for the TMDs is taken from the light-front constituent quark model, the spectator model, and available parametrizations of TMDs extracted from the experimental data. TMD evolution is im- plemented at Next-to-Leading Logarithmic precision for the first time for all asymmetries. Our results are compatible with the first experimental information, help to interpret the data from ongoing experiments, and will allow one to quantitatively assess the models in future when more precise data will become available
New target transverse spin dependent azimuthal asymmetries from COMPASS experiment
No full textIn general, eight target transverse spin-dependent azimuthal modulations are allowed in semi inclusive deep inelastic scattering of polarized leptons on a transversely polarized target. In the QCD parton model four of these asymmetries can be interpreted within the leading order approach. Two of them, namely Collins and Sivers effects were already measured by HERMES and COMPASS experiments. Other two leading twist and remaining four azimuthal asymmetries which can be interpreted as twist-three contributions have been measured for the first time in COMPASS using a 160 GeV/c longitudinally polarized () muon beam and a transversely polarized target. We present here the preliminary results from the 2002-2004 data.In general, eight target transverse spin-dependent azimuthal modulations are allowed in semi inclusive deep inelastic scattering of polarized leptons on a transversely polarized target. In the QCD parton model four of these asymmetries can be interpreted within the leading order approach. Two of them, namely Collins and Sivers effects were already measured by HERMES and COMPASS experiments. Other two leading twist and remaining four azimuthal asymmetries which can be interpreted as twist-three contributions have been measured for the first time in COMPASS using a 160 GeV/c longitudinally polarized () muon beam and a transversely polarized target. We present here the preliminary results from the 2002-2004 data
COMPASS Status Report 2023
No full textThe report reviews the activities and achievements of the Collaboration from July 2022 to October 2023. An overview of the 2022 data-taking is presented. The results and ongoing analysis of the data collected in 2022 and previous years are discussed
Strong interaction physics at the luminosity frontier with 22 GeV electrons at Jefferson Lab
No full textOn the physics potential to study the gluon content of proton and deuteron at NICA SPD
No full textThe Spin Physics Detector (SPD) is a future multipurpose experiment foreseen to run at the NICA collider, which is currently under construction at the Joint Institute for Nuclear Research (JINR, Dubna, Russia). The physics program of the experiment is based on collisions of longitudinally and transversely polarized protons and deuterons at s up to 27 GeV and luminosity up to 1032 cm−2 s−1. SPD will operate as a universal facility for the comprehensive study of the unpolarized and polarized gluon content of the nucleon, using complementary probes such as: charmonia, open-charm, and prompt-photon production processes. The aim of this work is to provide a thorough review of the physics objectives that can potentially be addressed at SPD, underlining related theoretical aspects and discussing relevant experimental results when available. Among different pertinent phenomena particular attention is drawn to the study of the gluon helicity, gluon Sivers and Boer-Mulders functions in the nucleon, as well as the gluon transversity distribution in the deuteron, via the measurement of single and double spin asymmetries
CCD polarimetry as a probe of regions of recent star-formation
No full textChapter 1 of this thesis details the incorporation of a Charged Coupled Device (CCD) detector system with the Durham Imaging Polarimeter. The details include the physical characteristics of the device and the electronics and software associated with the device control and data storage. The introduction of the CCD detector system haa made necessary the inclusion of a super-achromatic half-wave plate in the polarimeter which has an inherent variability in its optic axis. Chapter 2of this work describes fully how suitable corrections for this effect can be made, and derives "first order" results. The CCD performance is examined in comparison with the detector used previously and hence the veracity of the new results is established. Chapter 3 is a relevant summary of the status of the astronomy of the immediate regions of recent star-formation. Chapter 4 describes multicolour polarimetry of NGC2261/R Mon covering the period 1979 to 1986. The data conclusively proves that the polarisation of R Mon must be due to effects close to R Mon (~ 14 astronomical units). This is evident because of the dynamic timescale of the variations of the polarisation of R Mon and the anomalous band of polarisations seen across the head of the nebula. The interpretation presented is an extension of the Elsasser and Staude (1978) method of polarising objects embedded within the confines of a nearly edge-on disk. Detailed polarisations within the main nebula body provide evidence for this extended interpretation and also for an extensive helical magnetic field which may extend into the disk. Also it is seen that R Mon must still be "shrouded" in material preventing light from directly reflecting in the main nebula body. It is not thought that the variations in the region close to R Mon are due to planetary bodies but to accretion from the disk. The results of this re-interpretation of the polarising mechanism are tentatively applied to other similar objects
Transverse extension of partons in the proton probed in the sea-quark range by measuring the DVCS cross section
No full textWe report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/ polarized and beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured and cross sections for deeply virtual Compton scattering on the squared four-momentum transfer from the initial to the final final proton. The slope of the -dependence is fitted with a single exponential function, which yields . This result can be converted into an average transverse extension of partons in the proton, . For this measurement, the average virtuality of the photon mediating the interaction is and the average value of the Bjorken variable is .We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/ polarised and beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured and cross sections for deeply virtual Compton scattering on the squared four-momentum transfer from the initial to the final proton. The slope of the -dependence is fitted with a single exponential function, which yields (GeV/). This result can be converted into a transverse extension of partons in the proton, fm . For this measurement, the average virtuality of the photon mediating the interaction is =1.8(GeV/) and the average value of the Bjorken variable is =0.056.We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/ polarized and beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured and cross sections for deeply virtual Compton scattering on the squared four-momentum transfer from the initial to the final final proton. The slope of the -dependence is fitted with a single exponential function, which yields . This result can be converted into an average transverse extension of partons in the proton, . For this measurement, the average virtuality of the photon mediating the interaction is and the average value of the Bjorken variable is
Pion induced reactions on (4)He in the Delta resonance energy region
No full textMeasurement of the in-medium modifications of the resonance, signatures of the excitation of nuclear collective states and the first experimental evidence for a thermal emission of photons have been obtained from the analysis of new He data at =106 MeV at PAINUC experiment
On the physics potential to study the gluon content of proton and deuteron at NICA SPD
No full textInternational audienceThe Spin Physics Detector (SPD) is a future multipurpose experiment foreseen to run at the NICA collider, which is currently under construction at the Joint Institute for Nuclear Research (JINR, Dubna, Russia). The physics program of the experiment is based on collisions of longitudinally and transversely polarized protons and deuterons at s up to 27 GeV and luminosity up to 10 32 cm −2 s −1 . SPD will operate as a universal facility for the comprehensive study of the unpolarized and polarized gluon content of the nucleon, using complementary probes such as: charmonia, open-charm, and prompt-photon production processes.The aim of this work is to provide a thorough review of the physics objectives that can potentially be addressed at SPD, underlining related theoretical aspects and discussing relevant experimental results when available. Among different pertinent phenomena particular attention is drawn to the study of the gluon helicity, gluon Sivers and Boer-Mulders functions in the nucleon, as well as the gluon transversity distribution in the deuteron, via the measurement of single and double spin asymmetries
- …
