| 1. |
- Singh, B. P., et al.
(författare)
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Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
- 2015
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:8
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Tidskriftsartikel (refereegranskat)abstract
- Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (pi N) TDAs from (p) over barp -> e(+)e(-)pi(0) reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q(2), the amplitude of the signal channel (p) over barp -> e(+)e(-)pi(0) admits a QCD factorized description in terms of pi N TDAs and nucleon Distribution Amplitudes (DAs) in the forward aid backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring (p) over barp -> e(+)e(-)pi(0) with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. (p) over barp -> pi(+)pi(-)pi(0) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q(2) < 4.3 GeV2 and 5 < q(2) < 9 GeV2, respectively, with a neutral pion scattered in the forward or backward cone vertical bar cos theta(pi 0)vertical bar > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10(7) (1 . 10(7)) at low (high) q(2) for s = 5 GeV2, and of 1 . 10(8) (6 . 10(6)) at low (high) q(2) for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing pi N TDAs.
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| 2. |
- Singh, B., et al.
(författare)
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Study of doubly strange systems using stored antiprotons
- 2016
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Ingår i: Nuclear Physics A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 954, s. 323-340
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Tidskriftsartikel (refereegranskat)abstract
- Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the PANDA experiment at FAIR. For the first time, high resolution gamma-spectroscopy of doubly strange Lambda Lambda-hypernuclei will be performed, thus complementing measurements of ground state decays of Lambda Lambda-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Xi(-) -atoms will be feasible and even the production of Omega(-) -atoms will be within reach. The latter might open the door to the vertical bar S vertical bar = 3 world in strangeness nuclear physics, by the study of the hadronic Omega(-) -nucleus interaction. For the first time it will be possible to study the behavior of Xi(+) in nuclear systems under well controlled conditions.
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| 3. |
- Collaboration, The PANDA, et al.
(författare)
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Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
- 2016
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Ingår i: European Physical Journal A. - : Springer Publishing Company. - 1434-6001 .- 1434-601X. ; 52:10
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Tidskriftsartikel (refereegranskat)abstract
- Simulation results for future measurements of electromagnetic proton form factors at P ¯ ANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel p¯ p→ e+e- is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e.p¯ p→ π+π-, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance.
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| 4. |
- Erni, W., et al.
(författare)
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Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
- 2013
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
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Tidskriftsartikel (refereegranskat)abstract
- This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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| 5. |
- Singh, B., et al.
(författare)
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Feasibility study for the measurement of pi N transition distribution amplitudes at (P)over-barANDA in (P)over-barp -> J/psi pi(0)
- 2017
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:3
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Tidskriftsartikel (refereegranskat)abstract
- The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is shown that the measurement can be done at (P) over bar 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.
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| 6. |
- Akhunzyanov, R., et al.
(författare)
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Transverse extension of partons in the proton probed in the sea-quark range by measuring the DVCS cross section
- 2019
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Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 793, s. 188-194
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/c polarised mu(+) and mu(-) beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured mu(+) and mu(-) cross sections for deeply virtual Compton scattering on the squared four-momentum transfer t from the initial to the final proton. The slope B of the t-dependence is fitted with a single exponential function, which yields B = (4.3 +/- 0.6(stat) (+0.1)(-0.3)vertical bar(sys)) (GeV/c)(-2). This result can be converted into a transverse extension of partons in the proton,root(r(perpendicular to)(2)) = (0.58 +/- 0.04(stat) (+0.01)(-0.02)vertical bar(sys) +/- 0.04(model)) fm. For this measurement, the average virtuality of the photon mediating the interaction is < Q(2)> = 1.8 (GeV/c)(2) and the average value of the Bjorken variable is < X-Bj > = 0.056.
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| 7. |
- Jackura, A., et al.
(författare)
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New analysis of eta pi tensor resonances measured at the COMPASS experiment
- 2018
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 779, s. 464-472
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Tidskriftsartikel (refereegranskat)abstract
- We present a new amplitude analysis of the eta pi D-wave in the reaction pi(-) p -> eta pi(-) p measured by COMPASS. Employing an analytical model based on the principles of the relativistic S-matrix, we find two resonances that can be identified with the a(2)(1320) and the excited a(2)(1700), and perform a comprehensive analysis of their pole positions. For the mass and width of the a(2) we find M = (1307 +/- 1 6) MeV and Gamma=(112 +/- 1 +/- 8) MeV, and for the excited state a(2)' we obtain M = (1720 +/- 10 +/- 60) MeV and Gamma = (280 +/- 10 +/- 70) MeV, respectively.
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| 8. |
- Adolph, C., et al.
(författare)
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Interplay among transversity induced asymmetries in hadron leptoproduction
- 2016
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 753, s. 406-411
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Tidskriftsartikel (refereegranskat)abstract
- In the fragmentation of a transversely polarized quark several left-right asymmetries are possible for the hadrons in the jet. When only one unpolarized hadron is selected, it exhibits an azimuthal modulation known as the Collins effect. When a pair of oppositely charged hadrons is observed, three asymmetries can be considered, a di-hadron asymmetry and two single hadron asymmetries. In lepton deep inelastic scattering on transversely polarized nucleons all these asymmetries are coupled with the transversity distribution. From the high statistics COMPASS data on oppositely charged hadron-pair production we have investigated for the first time the dependence of these three asymmetries on the difference of the azimuthal angles of the two hadrons. The similarity of transversity induced single and di-hadron asymmetries is discussed. A new analysis of the data allows quantitative relationships to be established among them, providing for the first time strong experimental indication that the underlying fragmentation mechanisms are all driven by a common physical process.
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| 9. |
- Adolph, C., et al.
(författare)
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Multiplicities of charged pions and charged hadrons from deep-inelastic scattering of muons off an isoscalar target
- 2017
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Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 764, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Multiplicities of charged pions and charged hadrons produced in deep-inelastic scattering were measured in three-dimensional bins of the Bjorken scaling variable x, the relative virtual-photon energy y and the relative hadron energy z. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and an isoscalar target ((LiD)-Li-6). They cover the kinematic domain in the photon virtuality Q(2) > 1 (GeV/c) 2, 0.004 < x < 0.4, 0.2 < z < 0.85 and 0.1 < y < 0.7. In addition, a leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions.
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| 10. |
- Adolph, C., et al.
(författare)
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Final COMPASS results on the deuteron spin-dependent structure function g(1)(d) and the Bjorken sum rule
- 2017
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 769, s. 34-41
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Tidskriftsartikel (refereegranskat)abstract
- Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a 6LiD target. The data were taken at 160 GeV beam energy and the results are shown for the kinematic range 1 (GeV/c)2 < Q2 < 100 (GeV/c)2 in photon virtuality, 0.004 < x < 0.7 in the Bjorken scaling variable and W > 4GeV/c2 in the mass of the hadronic final state. The deuteron double-spin asymmetry A(1)(d) and the deuteron longitudinal-spin structure function g(1)(d) are presented in bins of x and Q2. Towards lowest accessible values of x, g(1)(d) decreases and becomes consistent with zero within uncertainties. The presented final g(1)(p) values together with the recently published final g(1)(p) values of COMPASS are used to again evaluate the Bjorken sum rule and perform the QCD fit to the g1 world data at next-to-leading order of the strong coupling constant. In both cases, changes in central values of the resulting numbers are well within statistical uncertainties. The flavour singlet axial charge a0, which is identified in the MS renormalisation scheme with the total contribution of quark helicities to the nucleon spin, is extracted at next-to-leading order accuracy from only the COMPASS deuteron data: a0(Q2 = 3 (GeV/c)2) = 0.32 +/- 0.02stat +/- 0.04syst +/- 0.05evol. Together with the recent results on the proton spin structure function g(1)(p), the results on g(1)(d) constitute the COMPASS legacy on the measurements of g1 through inclusive spin-dependent deep inelastic scattering.
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