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COMPASS Papers

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2025-12-19
16:55
Dihadron Transverse-Spin Asymmetries in Muon-Deuteron Deep-Inelastic Scattering / Alexeev, G.D. (Unlisted) ; Alexeev, M.G. (INFN, Turin) ; Alice, C. (INFN, Turin) ; Amoroso, A. (INFN, Turin) ; Andrieux, V. (NCSA, Urbana) ; Anosov, V. (Unlisted) ; Asatryan, S. (Yerevan Phys. Inst.) ; Augsten, K. (Prague, Tech. U.) ; Augustyniak, W. (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Azevedo, C.D.R. (Aveiro U.) et al. /COMPASS
In 2022, the COMPASS collaboration performed semi-inclusive measurements of deep-inelastic muon-scattering on a transversely polarised deuteron (6LiD) target. From these data, transverse spin–dependent dihadron asymmetries are extracted using pairs of oppositely charged hadrons. [...]
arXiv:2512.22311; CERN-EP-2025-298.- Geneva : CERN, 2025 - 6 p. Draft (restricted): PDF; Fulltext: CERN-EP-2025-298 - PDF; 2512.22311 - PDF;

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2025-12-10
11:38
Addendum to multiplicities of charged pions, kaons and unidentified charged hadrons on an isoscalar target measured by COMPASS Collaboration / COMPASS Collaboration
The COMPASS Collaboration has recently published an article ``Multiplicities of positive and negative pions, kaons, and unidentified hadrons from deep-inelastic scattering of muons off a liquid hydrogen target'', Phys. Rev. [...]
arXiv:2512.23727; CERN-EP-2025-291.- Geneva : CERN, 2025 - 7 p. Draft (restricted): PDF; Fulltext: CERN-EP-2025-291 - PDF; 2512.23727 - PDF;

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2022-10-28
10:24
Collins and Sivers transverse-spin asymmetries in inclusive muoproduction of $\rho^0$ mesons / COMPASS Collaboration
The production of vector mesons in deep inelastic scattering is an interesting yet scarsely explored channel to study the transverse spin structure of the nucleon and the related phenomena. The COMPASS collaboration has performed the first measurement of the Collins and Sivers asymmetries for inclusively produced $\rho^0$ mesons. [...]
arXiv:2211.00093; CERN-EP-2022-234; CERN-EP-2022--234.- Geneva : CERN, 2023-06-16 - 9 p. - Published in : Phys. Lett. B 843 (2023) 137950 Draft (restricted): PDF; Fulltext: CERN-EP-2022-234_2 - PDF; 2211.00093 - PDF; Publication - PDF;

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2022-10-27
17:08
Spin density matrix elements in exclusive $\rho ^0$ meson muoproduction / COMPASS Collaboration
We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive $\rho ^0$ meson muoproduction at COMPASS using 160~GeV/$c$ polarised $ \mu ^{+}$ and $ \mu ^{-}$ beams impinging on a liquid hydrogen target. The measurement covers the kinematic range 5.0~GeV/$c^2$ $< W <$ 17.0~GeV/$c^2$, 1.0 (GeV/$c$)$^2$ $< Q^2 <$ 10.0 (GeV/$c$)$^2$ and 0.01 (GeV/$c$)$^2$ $< p_{\rm{T}}^2 <$ 0.5 (GeV/$c$)$^2$. [...]
arXiv:2210.16932; CERN-EP-2022-231.- Geneva : CERN, 2023-10-13 - 32 p. - Published in : Eur. Phys. J. C 83 (2023) 924 Draft (restricted): PDF; Fulltext: 2210.16932 - PDF; CERN-EP-2022-231 - PDF; Publication - PDF;

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2021-04-27
19:34
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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2020-09-06
15:46
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: CERN-EP-2020-169 - PDF; 2009.03271 - PDF;

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2020-06-03
07:55
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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2020-03-20
09:52
Antiproton over proton and K$^-$ over K$^+$ multiplicity ratios at high $z$ in DIS / COMPASS Collaboration
The $\bar{\rm p} $ over p multiplicity ratio is measured in deep-inelastic scattering for the first time using (anti-) protons carrying a large fraction of the virtual-photon energy, $z>0.5$. The data were obtained by the COMPASS Collaboration using a 160 GeV muon beam impinging on an isoscalar $^6$LiD target. [...]
arXiv:2003.11791; CERN-EP-2020-041.- Geneva : CERN, 2020-07-02 - 19 p. - Published in : Phys. Lett. B 807 (2020) 135600 Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2020-041 - PDF; 2003.11791 - PDF; Fulltext from publisher: PDF;

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2019-12-18
08:40
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: CERN-EP-2019-286 - PDF; 1912.10322 - PDF;

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2018-09-02
17:21
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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