DOI: 10.1140/epjc/s10052-026-16148-3 ISSN: 1434-6044

Measurement of di-muons from 400 GeV/c protons interacting in a thick molybdenum/tungsten target

, A. Aksoy, R. Albanese, K. Albrecht, F. Alessio, A. Alexandrov, F. Aloschi, T. Arndt, D. Arutinov, A. Ballarino, L. Baudin, V. Bautin, A. Bay, I. Bekman, C. Betancourt, I. Bezshyiko, O. Bezshyyko, D. Bick, M. Birch, A. Blanco Castro, M. Bogomilov, P. Borges De Sousa, K. Bondarenko, W. M. Bonivento, M. Borisyak, N. Bourcey, T. Bowcock, A. Boyarsky, D. Breton, A. Brignoli, L. Brombach, V. Büscher, S. Buontempo, C.S. Caillot, M. Campanelli, D. Centanni, A. Cervelli, S. Charity, K. -Y. Choi, D. Chokheli, A. Chukanov, M. Climescu, M. Cristinziani, G. M. Dallavalle, M. Dam, N. D’Ambrosio, G. D’Appollonio, D. Davino, R. de Asmundis, P. de Bryas, J. De Carvalho Saraiva, G. De Lellis, M. de Magistris, A. De Roeck, M. De Serio, G. Del Giudice, P. Deucher, A. Devred, A. Di Crescenzo, C. Di Cristo, H. Dijkstra, D. Dobur, D. Duarte Ramos, T. Enik, O. Fecarotta, F. Fedotov, T. Ferber, M. Ferrillo, M. Ferro-Luzzi, A. Fiorillo, H. Fischer, R. Fresa, G. Frisella, S. J. Fuenzalida Garrido, T. Fukuda, G. Galati, E. Gamberini, K. Genovese, B. Goddard, L. Golinka-Bezshyyko, A. Golutvin, D. Gorbunov, V. Gorkavenko, E. Graverini, A. M. Guler, V. Guliaeva, C. Gwilliam, G. J. Haefeli, C. Hagner, J. C. Helo Herrera, M. J. Henriquez Zeren’e, E. van Herwijnen, A. Hollnagel, C. Issever, S. Izquierdo Bermudez, A. Iuliano, R. Jacobsson, D. Jokovic, C. Kamiscioglu, V. Kholoimov, S. H. Kim, Y. G. Kim, V. Koch, K. Kodama, T. Koettig, D. I. Kolev, L. Kolupaeva, M. Komatsu, V. Kostyukhin, I. Krasilnikova, A. Krolla, K. Kuznetsova, S. Kuleshov, H. M. Lacker, M. Lamont, O. Lantwin, A. Lauria, K. Y. Lee, W. C. Lee, N. Leonardo, V. P. Loschiavo, I. Lomidze, F. Lyons, J. Maalmi, A. M. Magnan, F. J. Mangiarotti, J. P. Marquez Hernandez, S. N. Medina Figueroa, G. H. Mendizabal, A. Miano, S. Mikado, A. Mikulenko, A. Milanese, J. A. Molinsĩ Bertram, T. A. Molzberger, M. C. Montesi, K. Morishima, A. S. Müller, Y. Mukhamejanov, N. Naganawa, T. Nakano, S. L. Ochoa Guaman, S. Ogawa, O. Olshevskiy, M. Ovchynnikov, P. Owen, U. Parzefall, A. Pastore, M. Patel, K. Petridis, O. Pirotte, N. Polukhina, L. F. Prates Cattelan, J. D. Price, S. R. Qasim, A. Quercia, A. Rademakers, F. Ratnikov, F. Redi, A. Reghunath, D. Riester, S. Ritter, T. J. Rock, E. Rodrigues, H. Rokujo, O. Ruchayskiy, T. Ruf, A. Saba, S. Sakhiyev, K. Salamatin, O. Samoylov, P. Santos D’iaz, O. Sato, F. Savary, C. Scharf, W. Schmidt-Parzefall, E. Schopf, M. Schumann, P. Schupp, N. Serra, M. Shaposhnikov, T. Schedrina, L. Shchutska, H. Shibuya, A. Sidoti, C. Silano, S. Simone, K. Skovpen, M. Smith, G. Soares, J. Y. Sohn, O. Soto Sandoval, O. Steinkamp, W. Sutcliffe, S. Tapia, H. Tilquin, I. Timiryasov, C. Touramanis Douramanis, D. Treille, Z. Tsamalaidze, N. Tsverava, P. Ulloa Poblete, E. Ursov, A. Ustyuzhanin, C. Valdivieso, G. Vasquez, N. Viaux, L. A Viera Lopes, S. Vilchinskii, C. Visone, S. van Waasen, R. Wanke, J. M. Webb, C. Weiser, J. Wenk, I. M. Wöstheinrich, M. Wurm, S. Yamamoto, D. Yilmaz, S. M. Yoo, C. S. Yoon, A. Zaitsev, J. Zamora Saa, T. Zholdybayev

Abstract

Di-muon events emanating from a replica of the SHiP target at the CERN SPS (with a 400 GeV/c proton beam) contain a clear signal of

$${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}}$$ J / ψ
production. The target consisted of 13 interaction lengths of molybdenum and tungsten, followed by a 2.4m iron hadron absorber. The di-muon rate is in reasonable agreement with Monte Carlo simulation based on Pythia v8. However, the
$${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}} $$ J / ψ
rate observed in the data is much lower than predicted by the Monte Carlo simulation, which is advantageous for SHiP since muons with a large
$$p_\textrm{T} $$ p T
are more difficult to deflect by the active muon shield.

For the center of mass rapidity (

$$y_{\textrm{cm}} $$ y cm
) interval with the largest overlap with the NA50 measurement,
$$0.3< y_{\textrm{cm}} < 0.6$$ 0.3 < y cm < 0.6
, we obtain the production cross-section per nucleon
$$\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A$$ σ ( J / ψ ) / A
including the branching ratios of
$${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}} $$ J / ψ
decays into muons,
$$B_{\mu ^+\mu ^-}$$ B μ + μ -
:

$$B_{\mu ^+\mu ^-}\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A=(1.18~\pm ~0.04~\pm ~0.10)~\textrm{nb}$$ B μ + μ - σ ( J / ψ ) / A = ( 1.18 ± 0.04 ± 0.10 ) nb
/nucleon.

This is to be compared to the NA50 extrapolated result (using a much thinner target):

$$B_{\mu ^+\mu ^-}\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A=(0.99~\pm ~0.04)~\textrm{nb}$$ B μ + μ - σ ( J / ψ ) / A = ( 0.99 ± 0.04 ) nb
/nucleon. Within the systematic errors, no significant enhancement due to secondary production of
$${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}}$$ J / ψ
inside the target is observed. An upper limit at 90% confidence level of possible contributions from secondary collisions of
$$<32\%$$ < 32 %
is obtained.

More from our Archive