Direct-photon production in inelastic and high-multiplicity proton–proton collisions at s= 13 TeV

ALICE Collaboration

doi:10.1016/j.physletb.2025.139645

Direct-photon production in inelastic and high-multiplicity proton–proton collisions at s= 13 TeV

ALICE Collaboration

Physics Education

Université Clermont Auvergne
Variable Energy Cyclotron Centre India
CERN
National Institute for Nuclear Physics
Aligarh Muslim University
Korea Institute of Science and Technology Information
Pavol Jozef Šafárik University
Goethe University Frankfurt
GSI Helmholtz Centre for Heavy Ion Research
Central China Normal University
Universidad Nacional Autónoma de México
University of Houston
Sungkyunkwan University
University of Bergen
Technical University of Munich
Benemerita Universidad Autonoma de Puebla
Horia Hulubei National Institute of Physics and Nuclear Engineering
University of Derby
University of Münster
Heidelberg University
Lawrence Berkeley National Laboratory
Nantes Université
Université Grenoble Alpes
Universidade de São Paulo
University of Oslo
Yale University
The University of Tokyo

Research output: Contribution to journal › Journal article › peer-review

2 Scopus citations

Abstract

In this letter, we present the first measurement of direct photons at the transverse momentum of 1<p_T<6 GeV/c at midrapidity |η|<0.8 in inelastic and high-multiplicity proton–proton collisions at a centre-of-mass energy of s= 13 TeV. The fraction of virtual direct photons in the inclusive virtual photon spectrum is obtained from a fit to the dielectron invariant mass spectrum. In the limit of zero invariant mass, this fraction is equal to the relative contribution of real direct photons in the inclusive real photon spectrum. Contributions from decays of light-flavour neutral mesons are estimated using independent measurements in proton–proton collisions at the same energy and the same event class. For the first time at the LHC energies, a direct-photon signal is observed at low p_T in both inelastic and high-multiplicity event classes, with a significance of 3.2σ and 1.9σ in terms of standard deviations, correspondingly. The yield of direct photons in inelastic pp collisions is compared to perturbative QCD calculations. The integrated photon yield is studied as a function of charged-particle multiplicity and is compared to the results from other experiments and theoretical calculations. The results show a significant increase of direct-photon yield with charged-particle multiplicity.

Original language	English
Article number	139645
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	868
DOIs	https://doi.org/10.1016/j.physletb.2025.139645
State	Published - 2025.09

Quacquarelli Symonds(QS) Subject Topics

Physics & Astronomy

Access to Document

10.1016/j.physletb.2025.139645

Cite this

@article{c1747a30e4874a7d8b9aee52331e2c7a,

title = "Direct-photon production in inelastic and high-multiplicity proton{\textendash}proton collisions at s= 13 TeV",

abstract = "In this letter, we present the first measurement of direct photons at the transverse momentum of 1T<6 GeV/c at midrapidity |η|<0.8 in inelastic and high-multiplicity proton{\textendash}proton collisions at a centre-of-mass energy of s= 13 TeV. The fraction of virtual direct photons in the inclusive virtual photon spectrum is obtained from a fit to the dielectron invariant mass spectrum. In the limit of zero invariant mass, this fraction is equal to the relative contribution of real direct photons in the inclusive real photon spectrum. Contributions from decays of light-flavour neutral mesons are estimated using independent measurements in proton{\textendash}proton collisions at the same energy and the same event class. For the first time at the LHC energies, a direct-photon signal is observed at low pT in both inelastic and high-multiplicity event classes, with a significance of 3.2σ and 1.9σ in terms of standard deviations, correspondingly. The yield of direct photons in inelastic pp collisions is compared to perturbative QCD calculations. The integrated photon yield is studied as a function of charged-particle multiplicity and is compared to the results from other experiments and theoretical calculations. The results show a significant increase of direct-photon yield with charged-particle multiplicity.",

author = "\{ALICE Collaboration\} and S. Acharya and A. Agarwal and \{Aglieri Rinella\}, G. and L. Aglietta and M. Agnello and N. Agrawal and Z. Ahammed and S. Ahmad and Ahn, \{S. U.\} and I. Ahuja and A. Akindinov and V. Akishina and M. Al-Turany and D. Aleksandrov and B. Alessandro and Alfanda, \{H. M.\} and \{Alfaro Molina\}, R. and B. Ali and A. Alici and N. Alizadehvandchali and A. Alkin and J. Alme and G. Alocco and T. Alt and Altamura, \{A. R.\} and I. Altsybeev and Alvarado, \{J. R.\} and Anaam, \{M. N.\} and C. Andrei and N. Andreou and A. Andronic and E. Andronov and V. Anguelov and F. Antinori and P. Antonioli and N. Apadula and L. Aphecetche and H. Appelsh{\"a}user and C. Arata and S. Arcelli and R. Arnaldi and Arneiro, \{J. G.M.C.A.\} and Arsene, \{I. C.\} and M. Arslandok and A. Augustinus and R. Averbeck and D. Averyanov and Azmi, \{M. D.\} and H. Baba and Kim, \{E. J.\}",

note = "Publisher Copyright: {\textcopyright} 2025 CERN for the benefit of the ALICE Collaboration",

year = "2025",

month = sep,

doi = "10.1016/j.physletb.2025.139645",

language = "English",

volume = "868",

journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",

issn = "0370-2693",

}

TY - JOUR

T1 - Direct-photon production in inelastic and high-multiplicity proton–proton collisions at s= 13 TeV

AU - ALICE Collaboration

AU - Acharya, S.

AU - Agarwal, A.

AU - Aglieri Rinella, G.

AU - Aglietta, L.

AU - Agnello, M.

AU - Agrawal, N.

AU - Ahammed, Z.

AU - Ahmad, S.

AU - Ahn, S. U.

AU - Ahuja, I.

AU - Akindinov, A.

AU - Akishina, V.

AU - Al-Turany, M.

AU - Aleksandrov, D.

AU - Alessandro, B.

AU - Alfanda, H. M.

AU - Alfaro Molina, R.

AU - Ali, B.

AU - Alici, A.

AU - Alizadehvandchali, N.

AU - Alkin, A.

AU - Alme, J.

AU - Alocco, G.

AU - Alt, T.

AU - Altamura, A. R.

AU - Altsybeev, I.

AU - Alvarado, J. R.

AU - Anaam, M. N.

AU - Andrei, C.

AU - Andreou, N.

AU - Andronic, A.

AU - Andronov, E.

AU - Anguelov, V.

AU - Antinori, F.

AU - Antonioli, P.

AU - Apadula, N.

AU - Aphecetche, L.

AU - Appelshäuser, H.

AU - Arata, C.

AU - Arcelli, S.

AU - Arnaldi, R.

AU - Arneiro, J. G.M.C.A.

AU - Arsene, I. C.

AU - Arslandok, M.

AU - Augustinus, A.

AU - Averbeck, R.

AU - Averyanov, D.

AU - Azmi, M. D.

AU - Baba, H.

AU - Kim, E. J.

PY - 2025/9

Y1 - 2025/9

N2 - In this letter, we present the first measurement of direct photons at the transverse momentum of 1T<6 GeV/c at midrapidity |η|<0.8 in inelastic and high-multiplicity proton–proton collisions at a centre-of-mass energy of s= 13 TeV. The fraction of virtual direct photons in the inclusive virtual photon spectrum is obtained from a fit to the dielectron invariant mass spectrum. In the limit of zero invariant mass, this fraction is equal to the relative contribution of real direct photons in the inclusive real photon spectrum. Contributions from decays of light-flavour neutral mesons are estimated using independent measurements in proton–proton collisions at the same energy and the same event class. For the first time at the LHC energies, a direct-photon signal is observed at low pT in both inelastic and high-multiplicity event classes, with a significance of 3.2σ and 1.9σ in terms of standard deviations, correspondingly. The yield of direct photons in inelastic pp collisions is compared to perturbative QCD calculations. The integrated photon yield is studied as a function of charged-particle multiplicity and is compared to the results from other experiments and theoretical calculations. The results show a significant increase of direct-photon yield with charged-particle multiplicity.

AB - In this letter, we present the first measurement of direct photons at the transverse momentum of 1T<6 GeV/c at midrapidity |η|<0.8 in inelastic and high-multiplicity proton–proton collisions at a centre-of-mass energy of s= 13 TeV. The fraction of virtual direct photons in the inclusive virtual photon spectrum is obtained from a fit to the dielectron invariant mass spectrum. In the limit of zero invariant mass, this fraction is equal to the relative contribution of real direct photons in the inclusive real photon spectrum. Contributions from decays of light-flavour neutral mesons are estimated using independent measurements in proton–proton collisions at the same energy and the same event class. For the first time at the LHC energies, a direct-photon signal is observed at low pT in both inelastic and high-multiplicity event classes, with a significance of 3.2σ and 1.9σ in terms of standard deviations, correspondingly. The yield of direct photons in inelastic pp collisions is compared to perturbative QCD calculations. The integrated photon yield is studied as a function of charged-particle multiplicity and is compared to the results from other experiments and theoretical calculations. The results show a significant increase of direct-photon yield with charged-particle multiplicity.

UR - https://www.scopus.com/pages/publications/105008771873

U2 - 10.1016/j.physletb.2025.139645

DO - 10.1016/j.physletb.2025.139645

M3 - Journal article

AN - SCOPUS:105008771873

SN - 0370-2693

VL - 868

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

M1 - 139645

ER -

Direct-photon production in inelastic and high-multiplicity proton–proton collisions at s= 13 TeV

Abstract

Quacquarelli Symonds(QS) Subject Topics

Access to Document

Other files and links

Fingerprint

Cite this