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1.
Exotic meson $\pi_1(1600)$ with $J^{PC} = 1^{-+}$ and its decay into $\rho(770)\pi$ / COMPASS Collaboration
We study the spin-exotic $J^{PC} = 1^{-+}$ amplitude in single-diffractive dissociation of 190 GeV$/c$ pions into $\pi^-\pi^-\pi^+$ using a hydrogen target and confirm the $\pi_1(1600) \to \rho(770) \pi$ amplitude, which interferes with a nonresonant $1^{-+}$ amplitude. We demonstrate that conflicting conclusions from previous studies on these amplitudes can be attributed to different analysis models and different treatment of the dependence of the amplitudes on the squared four-momentum transfer and we thus reconcile their experimental findings. [...]
arXiv:2108.01744; CERN-EP-2021–162.- 2022-01-01 - 30 p. - Published in : Phys. Rev. D 105 (2022) 012005 Fulltext: 2108.01744 - PDF; PhysRevD.105.012005 - PDF;
2.
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;
3.
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;
4.
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;
5.
Search for muoproduction of $X (3872)$ at COMPASS and indication of a new state $\widetilde{X}(3872)$ / COMPASS Collaboration
We have observed exclusive production of the exotic $X(3872)$ hadron in the reaction $\mu^+~N \rightarrow \mu^+ (J\!/\!\psi\pi^+\pi^-)\pi^{\pm}~N'$ using COMPASS data collected with incoming muons of 160~GeV/$c$ and 200~GeV/$c$ momentum. The statistical significance of the $X(3872)$ signal is 6$\sigma$. [...]
arXiv:1707.01796; CERN-EP-2017-165.- Geneva : CERN, 2018-08-10 - 7 p. - Published in : Phys. Lett. B 783 (2018) 334-340 Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2017-165 - PDF; SCOAP3 Fulltext - PDF; arXiv:1707.01796 - PDF;
6.
Longitudinal double-spin asymmetry $A_1^{\rm p}$ and spin-dependent structure function $g_1^{\rm p}$ of the proton at small values of $x$ and $Q^2$ / COMPASS Collaboration
We present a precise measurement of the proton longitudinal double-spin asymmetry $A_1^{\rm p}$ and the proton spin-dependent structure function $g_1^{\rm p}$ at photon virtualities $0.006~({\rm GeV}/c)^2<Q^2 < 1~({\rm GeV}/c)^2$ in the Bjorken $x$ range of $4 \times 10^{-5} < x < 4 \times 10^{-2}$. The results are based on data collected by the COMPASS Collaboration at CERN using muon beam energies of $160~{\rm GeV}$ and $200~{\rm GeV}$. [...]
arXiv:1710.01014; CERN-EP-2017-263.- Geneva : CERN, 2018-06-10 - 9 p. Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2017-263 - PDF; arXiv:1710.01014 - PDF;
7.
K$^{-}$ over K$^{+}$ multiplicity ratio for kaons produced in DIS with a large fraction of the virtual-photon energy / COMPASS Collaboration
The K$^{-}$ over K$^{+}$ multiplicity ratio is measured in deep-inelastic scattering, for the first time for kaons carrying a large fraction $z$ of the virtual-photon energy. The data were obtained by the COMPASS collaboration using a 160 GeV muon beam and an isoscalar $^6$LiD target. [...]
arXiv:1802.00584; CERN-EP-2018-012.- Geneva : CERN, 2018-11-10 - 9 p. - Published in : Phys. Lett. B 786 (2018) 390-398 Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2018-012 - PDF; 1802.00584 - PDF; arXiv:1802.00584 - PDF;
8.
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;
9.
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;
10.
Leading-order determination of the gluon polarisation from semi-inclusive deep inelastic scattering data / COMPASS collaboration
Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive single-hadron muoproduction with photon virtuality $Q^2>1~({\rm GeV}/c)^2$. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/$c$ polarised muon beam impinging on a polarised $^6$LiD target. [...]
arXiv:1512.05053; CERN-PH-EP-2015-328.- Geneva : CERN, 2017-04-03 - 14 p. - Published in : Eur. Phys. J. C 77 (2017) 209 Article from SCOAP3: PDF; Fulltext: arXiv:1512.05053 - PDF; CERN-PH-EP-2015-328 - PDF; Springer Open Access article: PDF;

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