A method for luminosity determination based on real-time hit reconstruction with the LHCb silicon pixel detector

LHCb Collaboration

doi:10.1088/1748-0221/21/04/P04011

A method for luminosity determination based on real-time hit reconstruction with the LHCb silicon pixel detector

LHCb Collaboration

National Institute for Subatomic Physics
University of Warwick
University of Zurich
University of Liverpool
Syracuse University
Instituto Galego de Física de Altas Enerxías (IGFAE)
University of Bristol
Uppsala University
Université Paris-Saclay
University of Michigan, Ann Arbor
Université Clermont Auvergne
National Institute for Nuclear Physics
TU Dortmund University
Lamarr Institute for Machine Learning and Artificial Intelligence
Vilnius University
CERN
University of Cambridge
Sorbonne Université
Universidade Federal do Rio de Janeiro
Peking University
University of A Coruna
University of Milan - Bicocca
University of Chinese Academy of Sciences
University of Rome Tor Vergata
Consejo Nacional de Rectores (CONARE)
CPPM
Swiss Federal Institute of Technology Lausanne
Massachusetts Institute of Technology
Laboratoire Leprince-Ringuet
University of Oxford
Heidelberg University
Ruhr University Bochum
Centro Brasileiro de Pesquisas Físicas
Pontifícia Universidade Católica do Rio de Janeiro
University of Manchester
University of Edinburgh
AGH University of Krakow
CAS - Institute of High Energy Physics
Ramon Llull University
Kyiv National Taras Shevchenko University
Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences
University of Bonn
Imperial College London
Université Savoie Mont Blanc
University of Modena and Reggio Emilia
University of Victoria BC
Los Alamos National Laboratory
Maastricht University
University of Ferrara
Monash University
Cracow University of Technology
Ohio State University
Wuhan University
University of Barcelona
Lanzhou University
Universidade Estadual de Campinas
University of Bologna
University of Genoa
Scuola Normale Superiore di Pisa
University of Milan
Tsinghua University
Eötvös Loránd University
NASU - Institute of Nuclear Research
Horia Hulubei National Institute of Physics and Nuclear Engineering
University of Glasgow
University of Cincinnati
National Autonomous University of Honduras
Hunan University
University of Cagliari
University of Groningen
Centro Federal de Educação Tecnológica Celso Suckow da Fonseca
University of Bari
Central China Normal University
University College Dublin
South China Normal University
Rutherford Appleton Laboratory
University of Perugia
University of Valencia
University of Maryland, College Park
NASU - Kharkov Institute of Physics and Technology
University of Freiburg
National Centre for Nuclear Research
University of Pisa
RWTH Aachen University
Universidad Nacional de Colombia
University of Birmingham
Vrije Universiteit Amsterdam
Henan Normal University
University of Padua
University of Bergamo
Universidad de Ingeniería y Tecnología
University of Siena
University of Basilicata
Max Planck Institute for Nuclear Physics
University of Alcalá
University of Urbino
Universidad Andrés Bello

Research output: Contribution to journal › Article › peer-review

Abstract

The data acquisition system of the upgraded LHCb experiment includes the fast reconstruction of all hits in the vertex locator (VELO) pixel detector at the beam-crossing rate of 40 MHz, implemented as on-the-fly clustering embedded in the firmware of the readout board FPGAs. The availability of a high rate of reconstructed clusters in real time enables a new fast approach for measuring luminosity and monitoring the LHCb luminous region, directly at the detector readout level. This methodology has been implemented as an array of real-time cluster counters in the VELO readout FPGAs and has been in operation since the start of the 2024 physics run of LHCb. This paper describes the methodology and its features and performance, both on proton-proton and lead-lead collision data. The method shows a statistical resolution better than the percent level, and a sensitivity to variable running conditions of the same level. This is achieved with an intrinsic time granularity better than 100 ms, undersampled to 3 s for analysis purposes. Nonlinear behaviour is compatible with zero in a luminosity range including the LHCb Run 3 operating point.

Original language	English
Article number	P04011
Journal	Journal of Instrumentation
Volume	21
Issue number	4
DOIs	https://doi.org/10.1088/1748-0221/21/04/P04011
State	Published - 1 Apr 2026
Externally published	Yes

Keywords

Analysis
Beam-line instrumentation (beam position and profile monitors, beam-intensity monitors, bunch length monitors)
Particle tracking detectors (Solid-state detectors)
Performance of High Energy Physics Detectors
statistical methods

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10.1088/1748-0221/21/04/P04011

Cite this

@article{8b4076c94c87423785875f5771cb1e86,

title = "A method for luminosity determination based on real-time hit reconstruction with the LHCb silicon pixel detector",

abstract = "The data acquisition system of the upgraded LHCb experiment includes the fast reconstruction of all hits in the vertex locator (VELO) pixel detector at the beam-crossing rate of 40 MHz, implemented as on-the-fly clustering embedded in the firmware of the readout board FPGAs. The availability of a high rate of reconstructed clusters in real time enables a new fast approach for measuring luminosity and monitoring the LHCb luminous region, directly at the detector readout level. This methodology has been implemented as an array of real-time cluster counters in the VELO readout FPGAs and has been in operation since the start of the 2024 physics run of LHCb. This paper describes the methodology and its features and performance, both on proton-proton and lead-lead collision data. The method shows a statistical resolution better than the percent level, and a sensitivity to variable running conditions of the same level. This is achieved with an intrinsic time granularity better than 100 ms, undersampled to 3 s for analysis purposes. Nonlinear behaviour is compatible with zero in a luminosity range including the LHCb Run 3 operating point.",

keywords = "Analysis, Beam-line instrumentation (beam position and profile monitors, beam-intensity monitors, bunch length monitors), Particle tracking detectors (Solid-state detectors), Performance of High Energy Physics Detectors, statistical methods",

author = "\{LHCb Collaboration\} and R. Aaij and Abdelmotteleb, \{A. S.W.\} and \{Abellan Beteta\}, C. and F. Abudin{\'e}n and T. Ackernley and Adefisoye, \{A. A.\} and B. Adeva and M. Adinolfi and P. Adlarson and C. Agapopoulou and Aidala, \{C. A.\} and Z. Ajaltouni and S. Akar and K. Akiba and P. Albicocco and J. Albrecht and R. Aleksiejunas and F. Alessio and \{Alvarez Cartelle\}, P. and R. Amalric and S. Amato and Amey, \{J. L.\} and Y. Amhis and L. An and L. Anderlini and M. Andersson and P. Andreola and M. Andreotti and \{Andres Estrada\}, S. and A. Anelli and D. Ao and C. Arata and F. Archilli and Z. Areg and M. Argenton and \{Arguedas Cuendis\}, S. and L. Arnone and A. Artamonov and M. Artuso and E. Aslanides and \{Ata{\'i}de Da Silva\}, R. and M. Atzeni and B. Audurier and Authier, \{J. A.\} and D. Bacher and \{Bachiller Perea\}, I. and S. Bachmann and M. Bachmayer and Back, \{J. J.\} and \{Calderon Ramirez\}, S.",

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month = apr,

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doi = "10.1088/1748-0221/21/04/P04011",

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volume = "21",

journal = "Journal of Instrumentation",

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TY - JOUR

T1 - A method for luminosity determination based on real-time hit reconstruction with the LHCb silicon pixel detector

AU - LHCb Collaboration

AU - Aaij, R.

AU - Abdelmotteleb, A. S.W.

AU - Abellan Beteta, C.

AU - Abudinén, F.

AU - Ackernley, T.

AU - Adefisoye, A. A.

AU - Adeva, B.

AU - Adinolfi, M.

AU - Adlarson, P.

AU - Agapopoulou, C.

AU - Aidala, C. A.

AU - Ajaltouni, Z.

AU - Akar, S.

AU - Akiba, K.

AU - Albicocco, P.

AU - Albrecht, J.

AU - Aleksiejunas, R.

AU - Alessio, F.

AU - Alvarez Cartelle, P.

AU - Amalric, R.

AU - Amato, S.

AU - Amey, J. L.

AU - Amhis, Y.

AU - An, L.

AU - Anderlini, L.

AU - Andersson, M.

AU - Andreola, P.

AU - Andreotti, M.

AU - Andres Estrada, S.

AU - Anelli, A.

AU - Ao, D.

AU - Arata, C.

AU - Archilli, F.

AU - Areg, Z.

AU - Argenton, M.

AU - Arguedas Cuendis, S.

AU - Arnone, L.

AU - Artamonov, A.

AU - Artuso, M.

AU - Aslanides, E.

AU - Ataíde Da Silva, R.

AU - Atzeni, M.

AU - Audurier, B.

AU - Authier, J. A.

AU - Bacher, D.

AU - Bachiller Perea, I.

AU - Bachmann, S.

AU - Bachmayer, M.

AU - Back, J. J.

AU - Calderon Ramirez, S.

PY - 2026/4/1

Y1 - 2026/4/1

N2 - The data acquisition system of the upgraded LHCb experiment includes the fast reconstruction of all hits in the vertex locator (VELO) pixel detector at the beam-crossing rate of 40 MHz, implemented as on-the-fly clustering embedded in the firmware of the readout board FPGAs. The availability of a high rate of reconstructed clusters in real time enables a new fast approach for measuring luminosity and monitoring the LHCb luminous region, directly at the detector readout level. This methodology has been implemented as an array of real-time cluster counters in the VELO readout FPGAs and has been in operation since the start of the 2024 physics run of LHCb. This paper describes the methodology and its features and performance, both on proton-proton and lead-lead collision data. The method shows a statistical resolution better than the percent level, and a sensitivity to variable running conditions of the same level. This is achieved with an intrinsic time granularity better than 100 ms, undersampled to 3 s for analysis purposes. Nonlinear behaviour is compatible with zero in a luminosity range including the LHCb Run 3 operating point.

AB - The data acquisition system of the upgraded LHCb experiment includes the fast reconstruction of all hits in the vertex locator (VELO) pixel detector at the beam-crossing rate of 40 MHz, implemented as on-the-fly clustering embedded in the firmware of the readout board FPGAs. The availability of a high rate of reconstructed clusters in real time enables a new fast approach for measuring luminosity and monitoring the LHCb luminous region, directly at the detector readout level. This methodology has been implemented as an array of real-time cluster counters in the VELO readout FPGAs and has been in operation since the start of the 2024 physics run of LHCb. This paper describes the methodology and its features and performance, both on proton-proton and lead-lead collision data. The method shows a statistical resolution better than the percent level, and a sensitivity to variable running conditions of the same level. This is achieved with an intrinsic time granularity better than 100 ms, undersampled to 3 s for analysis purposes. Nonlinear behaviour is compatible with zero in a luminosity range including the LHCb Run 3 operating point.

KW - Analysis

KW - Beam-line instrumentation (beam position and profile monitors, beam-intensity monitors, bunch length monitors)

KW - Particle tracking detectors (Solid-state detectors)

KW - Performance of High Energy Physics Detectors

KW - statistical methods

UR - https://www.scopus.com/pages/publications/105036297471

U2 - 10.1088/1748-0221/21/04/P04011

DO - 10.1088/1748-0221/21/04/P04011

M3 - Artículo

AN - SCOPUS:105036297471

SN - 1748-0221

VL - 21

JO - Journal of Instrumentation

JF - Journal of Instrumentation

IS - 4

M1 - P04011

ER -

A method for luminosity determination based on real-time hit reconstruction with the LHCb silicon pixel detector

Abstract

Keywords

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