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

@article{collaboration2026measurement,
  title = {{Measurement of di-muons from 400 GeV/c protons interacting in a thick molybdenum/tungsten target}},
  author = {The SHiP Collaboration and A. Aksoy and R. Albanese and K. Albrecht and F. Alessio and A. Alexandrov and F. Aloschi and T. Arndt and D. Arutinov and A. Ballarino and L. Baudin and V. Bautin and A. Bay and I. Bekman and C. Betancourt and I. Bezshyiko and O. Bezshyyko and D. Bick and M. Birch and A. Blanco Castro and M. Bogomilov and P. Borges De Sousa and K. Bondarenko and W. M. Bonivento and M. Borisyak and N. Bourcey and T. Bowcock and A. Boyarsky and D. Breton and A. Brignoli and L. Brombach and V. Büscher and S. Buontempo and C.S. Caillot and M. Campanelli and D. Centanni and A. Cervelli and S. Charity and K. -Y. Choi and D. Chokheli and A. Chukanov and M. Climescu and M. Cristinziani and G. M. Dallavalle and M. Dam and N. D’Ambrosio and G. D’Appollonio and D. Davino and R. de Asmundis and P. de Bryas and J. De Carvalho Saraiva and G. De Lellis and M. de Magistris and A. De Roeck and M. De Serio and G. Del Giudice and P. Deucher and A. Devred and A. Di Crescenzo and C. Di Cristo},
  journal = {The European Physical Journal C},
  year = {2026},
  month = oct,
  doi = {10.1140/epjc/s10052-026-16148-3},
  url = {https://link.springer.com/article/10.1140/epjc/s10052-026-16148-3},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Measurement of di-muons from 400 GeV/c protons interacting in a thick molybdenum/tungsten target
AU  - The SHiP Collaboration
AU  - A. Aksoy
AU  - R. Albanese
AU  - K. Albrecht
AU  - F. Alessio
AU  - A. Alexandrov
AU  - F. Aloschi
AU  - T. Arndt
AU  - D. Arutinov
AU  - A. Ballarino
AU  - L. Baudin
AU  - V. Bautin
AU  - A. Bay
AU  - I. Bekman
AU  - C. Betancourt
AU  - I. Bezshyiko
AU  - O. Bezshyyko
AU  - D. Bick
AU  - M. Birch
AU  - A. Blanco Castro
AU  - M. Bogomilov
AU  - P. Borges De Sousa
AU  - K. Bondarenko
AU  - W. M. Bonivento
AU  - M. Borisyak
AU  - N. Bourcey
AU  - T. Bowcock
AU  - A. Boyarsky
AU  - D. Breton
AU  - A. Brignoli
AU  - L. Brombach
AU  - V. Büscher
AU  - S. Buontempo
AU  - C.S. Caillot
AU  - M. Campanelli
AU  - D. Centanni
AU  - A. Cervelli
AU  - S. Charity
AU  - K. -Y. Choi
AU  - D. Chokheli
AU  - A. Chukanov
AU  - M. Climescu
AU  - M. Cristinziani
AU  - G. M. Dallavalle
AU  - M. Dam
AU  - N. D’Ambrosio
AU  - G. D’Appollonio
AU  - D. Davino
AU  - R. de Asmundis
AU  - P. de Bryas
AU  - J. De Carvalho Saraiva
AU  - G. De Lellis
AU  - M. de Magistris
AU  - A. De Roeck
AU  - M. De Serio
AU  - G. Del Giudice
AU  - P. Deucher
AU  - A. Devred
AU  - A. Di Crescenzo
AU  - C. Di Cristo
PY  - 2026
DA  - 2026/10/26
JO  - The European Physical Journal C
DO  - 10.1140/epjc/s10052-026-16148-3
UR  - https://link.springer.com/article/10.1140/epjc/s10052-026-16148-3
AB  - 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−1.111ptψ hspace1.111pt 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−1.111ptψ hspace1.111pt 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_T p T are more difficult to deflect by the active muon shield.  For the center of mass rapidity ( y_cm y cm ) interval with the largest overlap with the NA50 measurement, 0.3< y_cm < 0.6 0.3 < y cm < 0.6 , we obtain the production cross-section per nucleon σ (J hspace−1.66656pt/hspace−1.111ptψ hspace1.111pt)/A σ ( J / ψ ) / A including the branching ratios of J hspace−1.66656pt/hspace−1.111ptψ hspace1.111pt J / ψ decays into muons, B_μ ^+μ ^- B μ + μ - :  B_μ ^+μ ^-σ (J hspace−1.66656pt/hspace−1.111ptψ hspace1.111pt)/A=(1.18 ± 0.04 ± 0.10) 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_μ ^+μ ^-σ (J hspace−1.66656pt/hspace−1.111ptψ hspace1.111pt)/A=(0.99 ± 0.04) 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−1.111ptψ hspace1.111pt 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.
SN  - 1434-6044
SN  - 1434-6052
ER  -