This paper presents the measurement of the isolated prompt photon inclusive production cross section in pp and p–Pb collisions by the ALICE Collaboration at the LHC. The measurement is performed in p–Pb collisions at centre-of-mass energies per nucleon pair of $$\sqrt{s_{\text {NN}}}={5.02}\,\textrm{TeV}$$ and 8.16 TeV, as well as in pp collisions at $$\sqrt{s}={5.02}\,\textrm{TeV}$$ and 8 TeV. The cross section is obtained at midrapidity $$(|y|<0.7)$$ using a charged-track based isolation momentum $$p_\textrm{T}^{\text {iso,~ch}}<{1.5}\,\textrm{GeV}/c$$ in a cone with radius $$R=0.4$$ . The data for both collision systems are well reproduced by perturbative QCD (pQCD) calculations at next-to-leading order (NLO) using recent parton distribution functions for free (PDF) and bound (nPDF) nucleons. Furthermore, the nuclear modification factor $$R_{\text {pA}}$$ for both collision energies is consistent with unity for $$p_{\textrm{T}}$$ $$>{20}\,\textrm{GeV}/c$$ . However, deviations from unity ( $$R_\textrm{pA}<1$$ ) of up to 20% are observed for $$p_{\textrm{T}}$$ $$<{20}\,\textrm{GeV}/c$$ with limited significance, indicating the possible presence of nuclear effects in the initial state of the collision. The suppression increases with decreasing $$p_{\textrm{T}}$$ with a significance of $$2.3\upsigma $$ for a non-zero slope and yields $$R_{\textrm{pA}}<1$$ with a significance of $$1.8\upsigma $$ at $$\sqrt{s_{\textrm{NN}}}={8.16}\,\textrm{TeV}$$ for $$p_{\textrm{T}}$$ $$<{20}\,\textrm{GeV}/c$$ . In addition, a significance of $$1.1\upsigma $$ is observed for $$R_{\textrm{pA}}<1$$ at the lower collision energy $$\sqrt{s_{\textrm{NN}}}={5.02}\,\textrm{TeV}$$ for $$p_{\textrm{T}} < {14}\,\textrm{GeV}/c$$ . The magnitude and shape of the suppression are consistent with pQCD predictions at NLO using nPDFs that incorporate nuclear shadowing effects in the Pb nucleus.

Italy

S. Acharya

India

A. Agarwal

Switzerland

G. Aglieri Rinella

L. Aglietta

M. Agnello

N. Agrawal

Z. Ahammed

S. Ahmad

South Korea

S. Ahn

Slovakia

I. Ahuja

A. Akindinov

Germany

V. Akishina

M. Al-Turany

D. Aleksandrov

B. Alessandro

China

H. Alfanda

Mexico

R. Alfaro Molina

B. Ali

A. Alici

United States

N. Alizadehvandchali

A. Alkin

Norway

J. Alme

G. Alocco

T. Alt

A. Altamura

I. Altsybeev

J. Alvarado

M. Anaam

Romania

C. Andrei

United Kingdom

N. Andreou

A. Andronic

E. Andronov

V. Anguelov

F. Antinori

P. Antonioli

N. Apadula

H. Appelshäuser

France

C. Arata

S. Arcelli

R. Arnaldi

Brazil

J. Arneiro

I. Arsene

M. Arslandok

A. Augustinus

R. Averbeck

D. Averyanov

M. Azmi

Japan

H. Baba

A. Badalà

J. Bae

Y. Bae

Y. Baek

X. Bai

R. Bailhache

Y. Bailung

R. Bala

A. Baldisseri

Poland

B. Balis

S. Bangalia

Z. Banoo

V. Barbasova

F. Barile

L. Barioglio

Greece

M. Barlou

B. Barman

Hungary

G. Barnaföldi

L. Barnby

E. Barreau

V. Barret

L. Barreto

K. Barth

E. Bartsch

N. Bastid

Sweden

S. Basu

G. Batigne

D. Battistini

B. Batyunya

D. Bauri

Peru

J. Bazo Alba

Denmark

I. Bearden

P. Becht

D. Behera

I. Belikov

A. Bell Hechavarria

F. Bellini

R. Bellwied

S. Belokurova

L. Beltran

Y. Beltran

G. Bencedi

A. Bensaoula

S. Beole

Y. Berdnikov

A. Berdnikova

L. Bergmann

L. Bernardinis

L. Betev

P. Bhaduri

A. Bhasin

B. Bhattacharjee

Measurement of isolated prompt photon production in pp and p–Pb collisions at the LHC

Higgs boson production cross-sections via gluon–gluon fusion and vector-boson fusion in proton–proton collisions are measured in the $$H\rightarrow WW^*\rightarrow \ell \nu \ell \nu $$ decay channel. The Large Hadron Collider delivered proton–proton collisions at a centre-of-mass energy of $$13\,\text {TeV}$$ between 2015 and 2018, which were recorded by the ATLAS detector, corresponding to an integrated luminosity of $$140\,\text {fb}^{-1}.$$ The total cross-sections for Higgs boson production by gluon–gluon fusion and vector-boson fusion times the $$H\rightarrow WW^*$$ branching ratio are measured to be $$12.4^{+1.3}_{-1.2}\,\text {pb}$$ and $$0.79^{+0.18}_{-0.16}\,\text {pb},$$ respectively, in agreement with the Standard Model predictions. Higgs boson production is further characterised through measurements of Simplified Template Cross-Sections in a total of fifteen kinematic fiducial regions. A new scheme of kinematic fiducial regions has been introduced to enhance the sensitivity to CP-violating effects in Higgs boson interactions. Both schemes are used to constrain CP-even and CP-odd dimension-six operators in the Standard Model effective field theory

G. Aad

E. Aakvaag

B. Abbott

United Arab Emirates

S. Abdelhameed

K. Abeling

N. Abicht

S. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

Y. Abulaiti

B. Acharya

A. Ackermann

C. Adam Bourdarios

L. Adamczyk

S. Addepalli

M. Addison

J. Adelman

Türkiye

A. Adiguzel

T. Adye

A. Affolder

Y. Afik

Spain

M. Agaras

A. Aggarwal

C. Agheorghiesei

Azerbaijan

F. Ahmadov

S. Ahuja

X. Ai

G. Aielli

A. Aikot

M. Ait Tamlihat

B. Aitbenchikh

M. Akbiyik

T. Åkesson

A. Akimov

D. Akiyama

N. Akolkar

S. Aktas

G. Alberghi

Canada

J. Albert

P. Albicocco

G. Albouy

S. Alderweireldt

Z. Alegria

M. Aleksa

I. Aleksandrov

C. Alexa

T. Alexopoulos

F. Alfonsi

M. Algren

M. Alhroob

Czechia

Saudi Arabia

H. Ali

S. Ali

S. Alibocus

South Africa

M. Aliev

G. Alimonti

W. Alkakhi

C. Allaire

B. Allbrooke

J. Allen

P. Allport

A. Aloisio

Argentina

F. Alonso

C. Alpigiani

Z. Alsolami

A. Alvarez Fernandez

Measurements of Higgs boson production via gluon–gluon fusion and vector-boson fusion using $$H\rightarrow WW^*\rightarrow \ell \nu \ell \nu $$ decays in $\textit{pp}$ collisions with the ATLAS detector and their effective field theory interpretations