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Preprint
Report number arXiv:2412.19923
Title Measurement of the hard exclusive $\pi^{0}$ muoproduction cross section at COMPASS
Author(s)

Alexeev, G.D. (Unlisted) ; Alexeev, M.G. (INFN, Turin) ; Alice, C. (INFN, Turin) ; Amoroso, A. (INFN, Turin) ; Andrieux, V. (NCSA, Urbana) ; Anosov, V. (Unlisted) ; Augsten, K. (Prague, Tech. U.) ; Augustyniak, W. (NCBJ, Warsaw) ; Azevedo, C.D.R. (Aveiro U.) ; Badelek, B. (Warsaw U.) ; Barth, J. (Bonn U., HISKP) ; Beck, R. (Bonn U., HISKP) ; Beckers, J. (TUM-IAS, Munich) ; Bedfer, Y. (IRFU, Saclay) ; Bernhard, J. (CERN) ; Bodlak, M. (Charles U.) ; Bradamante, F. (INFN, Trieste) ; Bressan, A. (INFN, Trieste) ; Chang, W.-C. (Taiwan, Inst. Phys.) ; Chatterjee, C. (INFN, Trieste ; City Coll., N.Y.) ; Chiosso, M. (INFN, Turin) ; Chung, S.-U. (TUM-IAS, Munich ; Pusan Natl. U. ; Brookhaven) ; Cicuttin, A. (INFN, Trieste ; ICTP, Trieste) ; Correia, P.M.M. (Aveiro U.) ; Crespo, M.L. (INFN, Trieste ; ICTP, Trieste) ; D'Ago, D. (INFN, Trieste) ; Dalla Torre, S. (INFN, Trieste) ; Dasgupta, S.S. (Saha Inst.) ; Dasgupta, S. (INFN, Trieste ; Wollongong U.) ; Delcarro, F. (INFN, Turin) ; Denisenko, I. (Unlisted) ; Denisov, O.Yu. (INFN, Turin) ; Dehpour, M. (Charles U.) ; Donskov, S.V. (Unlisted) ; Doshita, N. (Yamagata U.) ; Dreisbach, Ch. (TUM-IAS, Munich) ; Dünnweber, W. (LMU Munich (main) ; Munich, Tech. U.) ; Dusaev, R.R. (Yerevan Phys. Inst. ; Unlisted) ; Ecker, D. (TUM-IAS, Munich) ; Eremeev, D. (Unlisted) ; Faccioli, P. (LIP, Lisbon) ; Faessler, M. (LMU Munich (main) ; Munich, Tech. U.) ; Finger, M. (Charles U.) ; jr., M.Finger (Charles U.) ; Fischer, H. (Freiburg U.) ; Flöthner, K.J. (Bonn U., HISKP) ; Florian, W. (INFN, Trieste ; ICTP, Trieste) ; Friedrich, J.M. (TUM-IAS, Munich) ; Frolov, V. (Unlisted) ; Ordòñez, L.G. Garcia (INFN, Trieste ; ICTP, Trieste) ; Gavrichtchouk, O.P. (Unlisted) ; Gerassimov, S. (Unlisted ; TUM-IAS, Munich) ; Giarra, J. (Mainz U., Inst. Kernphys.) ; Giordano, D. (INFN, Turin) ; Gorzellik, M. (Freiburg U.) ; Grasso, A. (INFN, Turin) ; Gridin, A. (Unlisted) ; Grosse Perdekamp, M. (NCSA, Urbana) ; Grube, B. (TUM-IAS, Munich) ; Grüner, M. (Bonn U., HISKP) ; Guskov, A. (Unlisted) ; Haas, P. (TUM-IAS, Munich) ; von Harrach, D. (Mainz U., Inst. Kernphys.) ; Hoffmann, M. (Bonn U., HISKP ; City Coll., N.Y.) ; d'Hose, N. (IRFU, Saclay ; City Coll., N.Y.) ; Hsieh, C.-Y. (Taiwan, Inst. Phys.) ; Ishimoto, S. (Yamagata U. ; KEK, Tsukuba) ; Ivanov, A. (Unlisted) ; Iwata, T. (Yamagata U.) ; Jary, V. (Prague, Tech. U.) ; Joosten, R. (Bonn U., HISKP) ; Jörg, P. (Freiburg U.) ; Kabuß, E. (Mainz U., Inst. Kernphys. ; City Coll., N.Y.) ; Kaspar, F. (TUM-IAS, Munich) ; Kerbizi, A. (INFN, Trieste) ; Ketzer, B. (Bonn U., HISKP) ; Khaustov, G.V. (Unlisted) ; Klein, F. (Bonn U.) ; Koivuniemi, J.H. (Ruhr U., Bochum ; NCSA, Urbana) ; Kolosov, V.N. (Unlisted) ; Kondo Horikawa, K. (Yamagata U.) ; Konorov, I. (Unlisted ; TUM-IAS, Munich) ; Korzenev, A.Yu. (Unlisted) ; Kotzinian, A.M. (Yerevan Phys. Inst. ; INFN, Turin) ; Kouznetsov, O.M. (Unlisted) ; Koval, A. (NCBJ, Warsaw) ; Kral, Z. (Charles U.) ; Kunne, F. (IRFU, Saclay) ; Kurek, K. (NCBJ, Warsaw) ; Kurjata, R.P. (Warsaw U. of Tech.) ; Lavickova, K. (Prague, Tech. U. ; Brookhaven) ; Levorato, S. (INFN, Trieste) ; Lian, Y.-S. (Taiwan, Inst. Phys. ; Taiwan, Natl. Normal U.) ; Lichtenstadt, J. (Tel Aviv U. (main)) ; Lin, P.-J. (Taiwan, Natl. Central U. ; City Coll., N.Y.) ; Longo, R. (NCSA, Urbana) ; Lyubovitskij, V.E. (Unlisted ; Tubingen U.) ; Maggiora, A. (INFN, Turin) ; Makke, N. (INFN, Trieste) ; Mallot, G.K. (CERN ; Freiburg U.) ; Maltsev, A. (Unlisted) ; Martin, A. (INFN, Trieste) ; Marzec, J. (Warsaw U. of Tech.) ; Matoušek, J. (Charles U.) ; Matsuda, T. (Miyazaki U.) ; Pires, C. Menezes (LIP, Lisbon) ; Metzger, F. (Bonn U., HISKP) ; Meyer, W. (Ruhr U., Bochum) ; Mikhasenko, M. (LMU Munich (main) ; ORIGINS, Garching) ; Mitrofanov, E. (Unlisted) ; Miura, D. (Yamagata U.) ; Miyachi, Y. (Yamagata U.) ; Molina, R. (INFN, Trieste ; ICTP, Trieste) ; Moretti, A. (INFN, Trieste) ; Nagaytsev, A. (Unlisted) ; Neyret, D. (IRFU, Saclay) ; Niemiec, M. (Warsaw U.) ; Nový, J. (Prague, Tech. U.) ; Nowak, W.-D. (Mainz U., Inst. Kernphys.) ; Nukazuka, G. (Yamagata U. ; Nishina Ctr., RIKEN) ; Olshevsky, A.G. (Unlisted) ; Ostrick, M. (Mainz U., Inst. Kernphys.) ; Panzieri, D. (INFN, Turin ; Piemonte Orientale U., Novara ; Hannover U.) ; Parsamyan, B. (Yerevan Phys. Inst. ; INFN, Turin ; CERN) ; Paul, S. (TUM-IAS, Munich) ; Pekeler, H. (Bonn U., HISKP) ; Peng, J.-C. (NCSA, Urbana) ; Pešek, M. (Charles U.) ; Peshekhonov, D.V. (Unlisted) ; Pešková, M. (Charles U. ; City Coll., N.Y.) ; Platchkov, S. (IRFU, Saclay) ; Pochodzalla, J. (Mainz U., Inst. Kernphys.) ; Polyakov, V.A. (Unlisted) ; Quintans, C. (LIP, Lisbon) ; Reicherz, G. (Ruhr U., Bochum) ; Riedl, C. (NCSA, Urbana) ; Ryabchikov, D.I. (Unlisted ; TUM-IAS, Munich) ; Rychter, A. (Warsaw U. of Tech.) ; Rymbekova, A. (Unlisted) ; Samoylenko, V.D. (Unlisted) ; Sandacz, A. (NCBJ, Warsaw ; City Coll., N.Y.) ; Sarkar, S. (Saha Inst.) ; Savin, I.A. (Unlisted) ; Sbrizzai, G. (INFN, Trieste) ; Schmieden, H. (Bonn U.) ; Selyunin, A. (Unlisted) ; Sinha, L. (Saha Inst.) ; Spülbeck, D. (Bonn U., HISKP) ; Srnka, A. (Inst. Sci. Instruments, Brno) ; Stolarski, M. (LIP, Lisbon) ; Sulc, M. (Liberec Tech. U.) ; Suzuki, H. (Yamagata U. ; Chubu U.) ; Tessaro, S. (INFN, Trieste) ; Tessarotto, F. (INFN, Trieste) ; Thiel, A. (Bonn U., HISKP) ; Tosello, F. (INFN, Turin) ; Townsend, A. (NCSA, Urbana ; West Virginia U.) ; Triloki, T. (INFN, Trieste ; City Coll., N.Y.) ; Tskhay, V. (Unlisted) ; Valinoti, B. (INFN, Trieste ; ICTP, Trieste) ; Veit, B.M. (Mainz U., Inst. Kernphys.) ; Veloso, J.F.C.A. (Aveiro U.) ; Ventura, B. (IRFU, Saclay ; City Coll., N.Y.) ; Vidon, A. (IRFU, Saclay ; City Coll., N.Y.) ; Vijayakumar, A. (NCSA, Urbana) ; Virius, M. (Prague, Tech. U.) ; Wagner, M. (Bonn U., HISKP) ; Wallner, S. (TUM-IAS, Munich) ; Zaremba, K. (Warsaw U. of Tech.) ; Zavertyaev, M. (Unlisted) ; Zemko, M. (Charles U. ; Prague, Tech. U.) ; Zemlyanichkina, E. (Unlisted)

Document contact Contact: arXiv
Imprint 2024-12-27
Subject category hep-ph ; Particle Physics - Phenomenology ; hep-ex ; Particle Physics - Experiment
Accelerator/Facility, Experiment CERN SPS ; NA58
Abstract A new and detailed measurement of the cross section for hard exclusive neutral-pion muoproduction on the proton was performed in a wide kinematic region, with the photon virtuality $Q^2$ ranging from 1 to 8 (GeV/$c$)$^{\rm\, 2}$ and the Bjorken variable $x_{\rm Bj}$ ranging from 0.02 to 0.45. The data were collected at COMPASS at CERN using 160 GeV/$c$ longitudinally polarised $\mu^+$ and $\mu^-$ beams scattering off a 2.5 m long 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 the initial and final state proton in the range 0.08 (GeV/$c$)$^{\rm\, 2}$$< |t| <$ 0.64 (GeV/$c$)$^{\rm\, 2}$. From its angular distribution, the combined contribution of transversely and longitudinally polarised photons are determined, as well as transverse--transverse and longitudinal--transverse interference contributions. They are studied as functions of four-momentum transfer $|t|$, photon virtuality $Q^2$ and virtual-photon energy $\nu$. The longitudinal--transverse interference contribution is found to be compatible with zero. The significant transverse--transverse interference contribution reveals the existence of a dominant contribution by transversely polarized photons. This provides clear experimental evidence for the chiral-odd GPD $\overline{E}_T$. In addition, the existence of a non-negligible contribution of longitudinally polarized photons is suggested by the $|t|$-dependence of the cross section at $x_{\rm Bj} < $ 0.1 . Altogether, these results provide valuable input for future modelling of GPDs and thus of cross sections for exclusive pseudo-scalar meson production. Furthermore, they can be expected to facilitate the study of next-to-leading order corrections and higher-twist contributions.
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