Antiproton over proton and K\(^-\) over K\(^+\) multiplicity ratios at high \(z\) in DIS

• Published in: arXiv.org 2020-03
• Main Authors: Amoroso, A, Anosov, V, Azevedo, C D R, Balestra, F, Barth, J, Beck, R, Bernhard, J, Bodlak, M, Bressan, A, Buechele, M, Burtsev, V E, Chiosso, M, S -U Chung, Correia, P M M, Crespo, M L, Donskov, S V, Doshita, N, Dusaev, R R, Faccioli, P, Faessler, M, Finger, M, Franco, C, Friedrich, J M, Gavrichtchouk, O P, Gorzellik, M, Gridin, A, Grube, B, Guskov, A, D von Harrach, Herrmann, F, Horikawa, N, C -Y Hsieh, Ishimoto, S, Iwata, T, Joosten, R, Joerg, P, Ketzer, B, Khaustov, G V, Kolosov, V N, Konorov, I, Konstantinov, V F, Kotzinian, A M, Kouznetsov, O M, Koval, A, Kral, Z, Kunne, F, Kurek, K, Lavickova, K, Levorato, S, Y -S Lian, P -J Lin, Makke, N, Mallot, G K, Marianski, B, Martin, A, Matousek, J, Matsuda, T, Mattson, G, Meshcheryakov, G V, Meyer, W, Mikhasenko, M, Mitrofanov, E, Moretti, A, Naim, C, Novy, J, Nukazuka, G, Nunes, A S, Ostrick, M, Panzieri, D, Paul, S, Peskova, M, Platchkov, S, Pochodzalla, J, Pretz, J, Quaresma, M, Reicherz, G, Ryabchikov, D I, Rychter, A, Sandacz, A, Savin, I A, Schmieden, H, Sinha, L, Slunecka, M, Srnka, A, Steffen, D, Sznajder, P, Tessaro, S, Tessarotto, F, Thiel, A, Tomsa, J, Townsend, A, Tskhay, V, Veloso, J, Vidon, A, Wagner, M, Zaremba, K, Zavada, P, Zavertyaev, M, Zemko, M
• Format: Article
• Language: English
• Subjects: Antiparticles; Antiprotons; Inelastic scattering; Muons; Particle beams; Photons; Protons; Quantum chromodynamics; Quarks
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2003.11791

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. The regime of deep-inelastic scattering is ensured by requiring \(Q^2\) > 1 (GeV/\(c\))\(^2\) for the photon virtuality and \(W > 5\) GeV/\(c^2\) for the invariant mass of the produced hadronic system. The range in Bjorken-\(x\) is restricted to \(0.01 < x < 0.40\). Protons and antiprotons are identified in the momentum range \(20 \div 60\) GeV/\(c\). In the whole studied \(z\)-region, the \(\bar{\rm p}\) over p multiplicity ratio is found to be below the lower limit expected from calculations based on leading-order perturbative Quantum Chromodynamics (pQCD). Extending our earlier analysis of the K\(^-\) over K\(^+\) multiplicity ratio by including now events with larger virtual-photon energies, this ratio becomes closer to the expectation of next-to-leading order pQCD. The results of both analyses strengthen our earlier conclusion that the phase space available for hadronisation should be taken into account in the pQCD formalism.