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1.
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Double J/ψ production in pion-nucleon scattering at COMPASS
/ COMPASS Collaboration
We present the study of the production of double $J/\psi$ mesons using COMPASS data collected with a 190 $\GeV/c$ $\pi^-$ beam scattering off NH$_{3}$, Al and W targets. Kinematic distributions of the collected double $J/\psi$ events are analysed, and the double $J/\psi$ production cross section is estimated for each of the COMPASS targets. [...]
arXiv:2204.01817; CERN-EP-2022-073.-
Geneva : CERN, 2023-03-10 - 8 p.
- Published in : Phys. Lett. B 838 (2023) 137702
Fulltext: Publication - PDF; CERN-EP-DRAFT-COMPASS-2022-001 - PDF; 2204.01817 - PDF;
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2.
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Probing transversity by measuring $\Lambda$ polarisation in SIDIS
/ Alexeev, M.G. ; Alexeev, G.D. (Dubna, JINR) ; Amoroso, A. ; Andrieux, V. ; Anosov, V. (Dubna, JINR) ; Augsten, K. ; Augustyniak, W. (NCBJ, Warsaw) ; Azevedo, C.D.R. (Aveiro U.) ; Badełek, B. (Warsaw U.) ; Balestra, F. et al.
/COMPASS
Based on the observation of sizeable target-transverse-spin asymmetries in single-hadron and hadron-pair production in Semi-Inclusive measurements of Deep Inelastic Scattering (SIDIS), the chiral-odd transversity quark distribution functions $h_1^q$ are nowadays well established. Several possible channels to access these functions were originally proposed. [...]
arXiv:2104.13585; CERN-EP-2021-072.-
Geneva : CERN, 2022-01-10 - 18 p.
Draft (restricted): PDF; Fulltext: CERN-EP-2021-072 - PDF; 2104.13585 - PDF;
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3.
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Spin Density Matrix Elements in Exclusive $\omega$ Meson Muoproduction $^*$
/ COMPASS Collaboration
We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive $\omega$ meson muoproduction on the proton at COMPASS using 160 GeV/$c$ polarised $ \mu ^{+}$ and $ \mu ^{-}$ beams impinging on a liquid hydrogen target. The measurement covers the range 5.0 GeV/$c^2$ $< W <$ 17.0 GeV/$c^2$, with the average kinematics $\langle Q^{2} \rangle=$ 2.1 (GeV/$c$)$^2$, $\langle W \rangle= 7.6$ GeV/$c^2$, and $\langle p^{2}_{\rm T} \rangle = 0.16$ (GeV/$c$)$^2$. [...]
arXiv:2009.03271; CERN-EP-2020-169.-
Geneva : CERN, 2021-02-05 - 22 p.
- Published in : Eur. Phys. J. C 81 (2021) 126
Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: 2009.03271 - PDF; CERN-EP-2020-169 - PDF;
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4.
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A Triangle Singularity as the Origin of the $a_1(1420)$
/ Alexeev, G.D. (Dubna, JINR) ; Alexeev, M.G. (Turin U. ; INFN, Turin) ; Amoroso, A. (Turin U. ; INFN, Turin) ; Andrieux, V. (CERN ; Illinois U., Urbana) ; Anosov, V. (Dubna, JINR) ; Antoshkin, A. (Dubna, JINR) ; Augsten, K. (Dubna, JINR ; CTU, Prague) ; Augustyniak, W. (NCBJ, Warsaw) ; Azevedo, C.D.R. (Aveiro U.) ; Badełek, B. (Warsaw U.) et al.
The COMPASS experiment recently discovered a new isovector resonance-like signal with axial-vector quantum numbers, the $a_1(1420)$, decaying to $f_0(980)\pi$. With a mass too close to and a width smaller than the axial-vector ground state $a_1(1260)$, it was immediately interpreted as a new light exotic meson, similar to the $X$, $Y$, $Z$ states in the hidden-charm sector. [...]
arXiv:2006.05342; CERN-EP-2020-104.-
Geneva : CERN, 2021-08-18 - 21 p.
- Published in : Phys. Rev. Lett.
Draft (restricted): PDF; Fulltext: CERN-EP-2020-104 - PDF; 2006.05342 - PDF;
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5.
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Contribution of exclusive diffractive processes to the measured azimuthal asymmetries in SIDIS
/ COMPASS Collaboration
Hadron leptoproduction in Semi-Inclusive measurements of Deep-Inelastic Scattering (SIDIS) on unpolarised nucleons allows one to get information on the intrinsic transverse momentum of quarks in a nucleon and on the Boer-Mulders function through the measurement of azimuthal modulations in the cross section. These modulations were recently measured by the HERMES experiment at DESY on proton and deuteron targets, and by the COMPASS experiment using the CERN SPS muon beam and a $^6$LiD target. [...]
arXiv:1912.10322; CERN-EP-2019-286.-
Geneva : CERN, 2020-07 - 13 p.
- Published in : Nucl. Phys. B 956 (2020) 115039
Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: 1912.10322 - PDF; CERN-EP-2019-286 - PDF;
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6.
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Measurement of the cross section for hard exclusive $\pi^0$ leptoproduction
/ COMPASS Collaboration
We report on a measurement of hard exclusive $\pi^0$ 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. From the average of the measured $\mu^+$ and $\mu^-$ cross sections, the virtual-photon proton cross section is determined as a function of the squared four-momentum transfer between initial and final proton in the range $0.08\,(\text{GeV/}c)^2 < |t| < 0.64\,(\text{GeV/}c)^2$. [...]
arXiv:1903.12030; CERN-EP-2019-049.-
2020-06-10 - 9 p.
- Published in : Phys. Lett. B 805 (2020) 135454
Article from SCOAP3: PDF; Fulltext: PDF; Fulltext from publisher: PDF;
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7.
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A New QCD facility at the M2 beam line of the CERN SPS: COMPASS++/AMBER
/ Adams, B. (Chicago U., EFI ; Xonics Inc.) ; Aidala, C.A. (Michigan U.) ; Akhunzyanov, R. (Dubna, JINR) ; Alexeev, G.D. (Dubna, JINR) ; Alexeev, M.G. (Turin U.) ; Amoroso, A. (Turin U. ; INFN, Turin) ; Andrieux, V. (Illinois U., Urbana) ; Anfimov, N.V. (Dubna, JINR) ; Anosov, V. (Dubna, JINR) ; Antoshkin, A. (Dubna, JINR) et al.
In this Letter of Intent, we propose a broad experimental programme for the ``New QCD facility at the M2 beam line of the CERN SPS''. [...]
arXiv:1808.00848 ; CERN-SPSC-2019-003 ; SPSC-I-250 ; SPSC-I-250.
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2019. - 91 p.
Full text - Fulltext
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8.
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Measurement of $P_T$-weighted Sivers asymmetries in leptoproduction of hadrons
/ COMPASS Collaboration
The transverse spin asymmetries measured in semi-inclusive leptoproduction of hadrons, when weighted with the hadron transverse momentum $P_T$, allow for the extraction of important transverse-momentum-dependent distribution functions. In particular, the weighted Sivers asymmetries provide direct information on the Sivers function, which is a leading-twist distribution that arises from a correlation between the transverse momentum of an unpolarised quark in a transversely polarised nucleon and the spin of the nucleon. [...]
arXiv:1809.02936; CERN-EP-2018-242.-
Geneva : CERN, 2019-03 - 20 p.
- Published in : Nucl. Phys. B 940 (2019) 34-53
Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2018-242 - PDF; 1809.02936 - PDF;
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9.
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Light isovector resonances in $\pi^- p \to \pi^-\pi^-\pi^+ p$ at 190 GeV/${\it c}$
/ COMPASS Collaboration
We have performed the most comprehensive resonance-model fit of $\pi^-\pi^-\pi^+$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction $\pi^- + p \to \pi^-\pi^-\pi^+ + p_\text{recoil}$ with a 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5 < m_{3\pi} < 2.5$ GeV/$c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1 < t' < 1.0$ $($GeV$/c)^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC} = 0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. [...]
arXiv:1802.05913; CERN-EP-2018-021.-
Geneva : CERN, 2018-11-02 - 72 p.
- Published in : Phys. Rev. D 98 (2018) 092003
Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2018-021 - PDF; 1802.05913 - PDF;
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10.
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Transverse extension of partons in the proton probed in the sea-quark range by measuring the DVCS cross section
/ COMPASS Collaboration
We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/$c$ polarized $\mu^+$ 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 final proton. [...]
arXiv:1802.02739; CERN-EP-2018-016.-
Geneva : CERN, 2019-06-10 - 7 p.
Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: 1802.02739 - PDF; CERN-EP-2018-016 - PDF; Fulltext from publisher: PDF;
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