<p>This Letter presents a combination of searches for Higgs boson pair (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi></math>) production performed by the ATLAS and CMS Collaborations using proton-proton collision datasets recorded at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> during the Large Hadron Collider Run 2, corresponding to integrated luminosities ranging between 126 and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>140</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. The upper limit at the 95% confidence level on the total <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi></math> signal strength, defined as the ratio of the measured cross section to the standard model (SM) prediction, corresponds to 2.5, with an expected value of 1.7 (2.8) assuming the absence (presence) of the SM <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi></math> signal. The strength of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi></math> signal is measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mn>0.8</mn><mrow><mo>−</mo><mn>0.7</mn></mrow><mrow><mo>+</mo><mn>0.9</mn></mrow></msubsup></math> relative to the SM prediction. The observed significance is found to be 1.1 standard deviations whereas 1.3 are expected for the SM <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi></math> signal. Constraints are set on the Higgs boson trilinear self-coupling and on the couplings of two Higgs bosons to two vector bosons, both normalized to the SM predictions and denoted as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>κ</mi><mi>λ</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>κ</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub></math>, respectively. The observed individual constraints at the 95% confidence level are <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo>−</mo><mn>0.71</mn><mo>&lt;</mo><msub><mrow><mi>κ</mi></mrow><mrow><mi>λ</mi></mrow></msub><mo>&lt;</mo><mn>6.1</mn></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>0.73</mn><mo>&lt;</mo><msub><mi>κ</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub><mo>&lt;</mo><mn>1.3</mn></math>, while the expected constraints assuming the presence of the SM <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>H</mi></math> signal are <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>−</mo><mn>1.3</mn><mo>&lt;</mo><msub><mi>κ</mi><mi>λ</mi></msub><mo>&lt;</mo><mn>6.7</mn></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>0.66</mn><mo>&lt;</mo><msub><mi>κ</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub><mo>&lt;</mo><mn>1.4</mn></math>.</p>

France

G. Aad

Norway

E. Aakvaag

United States

B. Abbott

United Arab Emirates

S. Abdelhameed

Germany

K. Abeling

N.J. Abicht

S.H. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

Italy

B.S. Acharya

A. Ackermann

C. Adam Bourdarios

Poland

L. Adamczyk

S.V. Addepalli

United Kingdom

M.J. Addison

J. Adelman

Türkiye

A. Adiguzel

T. Adye

A.A. Affolder

Y. Afik

Spain

M.N. Agaras

A. Aggarwal

Romania

C. Agheorghiesei

A. Ahmad

F. Ahmadov

S. Ahuja

China

X. Ai

G. Aielli

A. Aikot

M. Ait Tamlihat

B. Aitbenchikh

Sweden

T.P.A. Åkesson

Japan

D. Akiyama

N.N. Akolkar

S. Aktas

G.L. Alberghi

Canada

J. Albert

Switzerland

U. Alberti

P. Albicocco

G.L. Albouy

S. Alderweireldt

Z.L. Alegria

CERN

M. Aleksa

I.N. Aleksandrov

C. Alexa

Greece

T. Alexopoulos

F. Alfonsi

M. Algren

M. Alhroob

Czechia

B. Ali

H.M.J. Ali

S. Ali

S.W. Alibocus

South Africa

M. Aliev

G. Alimonti

C. Allaire

B.M.M. Allbrooke

D.R. Allen

J.S. Allen

J.F. Allen

Australia

C.S. Alley

E.R. Almazan

A. Aloisio

Argentina

F. Alonso

C. Alpigiani

Z.M.K. Alsolami

A. Alvarez Fernandez

M. Alves Cardoso

M.G. Alviggi

M. Aly

Brazil

Y. Amaral Coutinho

A. Ambler

C. Amelung

M. Amerl

T. Amezza

B. Amini

K. Amirie

A. Amirkhanov

Portugal

S.P. Amor Dos Santos

D. Amperiadou

S. An

C. Anastopoulos

T. Andeen

J.K. Anders

A.C. Anderson

A. Andreazza

S. Angelidakis

A. Angerami

A.V. Anisenkov

A. Annovi

C. Antel

E. Antipov

M. Antonelli

F. Anulli

M. Aoki

T. Aoki

M.A. Aparo

L. Aperio Bella

Combination of ATLAS and CMS Searches for Higgs Boson Pair Production at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>

The total decay widths of heavy mesons can be systematically calculated in terms of an expansion in the two parameters 1/$\textit{m}$ and $\textit{α}$ ($\textit{m}$ ), where $\textit{Q}$ = $\textit{c}$, $\textit{b}$ denotes the heavy quark. The dominant contributions to meson lifetime splittings stem from terms which are suppressed by $$ 1/{m}_Q^3 $$ with respect to the leading universal contribution to the total decay width. We calculate three-loop contributions of order $$ {\alpha}_s^2/{m}_q^3 $$ to the lifetime ratios $$ \tau \left({B}^{+}\right)/\tau \left({B}_d^0\right) $$ , $\textit{τ}$($\textit{D}$ )/$\textit{τ}$($\textit{D}$ ), and $$ \tau \left({D}_s^{+}\right)/\tau \left({D}^0\right) $$ in the limit of exact isospin and V-spin symmetry, respectively. Furthermore, we present new $$ {\alpha}_s/{m}_q^3 $$ corrections to the Cabibbo-suppressed terms in $$ \tau \left({B}^{+}\right)/\tau \left({B}_d^0\right) $$ . Combining our perturbative coefficients with hadronic matrix elements calculated from Heavy Quark Effective Theory sum rules, we find $$ \tau \left({B}^{+}\right)/\tau \left({B}_d^0\right) $$ = 1.072 ± 0.024. Using hadronic matrix elements from a recent lattice QCD calculation we find $\textit{τ}$($\textit{D}$ )/$\textit{τ}$($\textit{D}$ ) = 2.344 ± 0.170 and $$ \tau \left({D}_s^{+}\right)/\tau \left({D}^0\right) $$ = 1.289 ± 0.042. We find good agreement of our predictions with experimental data, which constitutes a successful probe of the calculations of hadronic matrix elements and permits estimates of the unknown $$ 1/{m}_Q^4 $$ contributions as well as the V-spin breaking terms in $$ \tau \left({D}_s^{+}\right)/\tau \left({D}^0\right) $$ .

Francesco Moretti

Ulrich Nierste

Pascal Reeck

Matthias Steinhauser

Next-to-next-to-leading QCD corrections to the $$ {\mathrm{B}}^{+}-{\mathrm{B}}_{\mathrm{d}}^0 $$ , D+ − D0, and $$ {\mathrm{D}}_{\mathrm{s}}^{+}-{\mathrm{D}}^0 $$ lifetime ratios

The Schwinger model is perhaps the simplest non-trivial exactly-solvable QFT. In this note we examine the perturbative structure of the theory on the sphere and provide evidence that its quantum corrections match those predicted by the expansion of the exact solution.

Joseph Smith

A note on the perturbative expansion of the Schwinger model on $\textit{S}$ 2

Measurements of the production of the W $$^{\pm }$$ and Z $$^0$$ bosons at midrapidity in pp collisions at $$\sqrt{s} = 13$$ TeV with ALICE at the Large Hadron Collider (LHC) are presented. The W $$^{\pm }$$ and Z $$^0$$ bosons are detected via their (di)electronic decay channels, with the electron reconstruction performed in the midrapidity region $$(|y|< 0.6).$$ The $$p_{{\text {T}}}$$ -integrated and $$p_{\textrm{T}}$$ -differential production cross sections of electrons from W $$^{\pm }$$ decays in the interval $$30<p_{{\text {T}}}< 60$$ GeV/$\textit{c}$, as well as the $$p_{{\text {T}}}$$ -integrated production cross section of Z $$^0$$ bosons, are measured. The results are described by perturbative QCD calculations using different sets of parton distribution functions. The production of W $$^{\pm }$$ bosons and azimuthally correlated associated hadrons is also measured as a function of the charged-particle multiplicity for the first time at the LHC. The former increases approximately linearly with the charged-particle multiplicity, while for the latter, there are hints of a faster-than-linear increase. These observations are compared with theoretical calculations.

I. Abualrob

S. Acharya

G. Aglieri Rinella

L. Aglietta

N. Agrawal

India

Z. Ahammed

S. Ahmad

Slovakia

I. Ahuja

Indonesia

Z. Akbar

A. Akindinov

V. Akishina

M. Al-Turany

D. Aleksandrov

B. Alessandro

Mexico

R. Alfaro Molina

A. Alici

South Korea

A. Alkin

J. Alme

G. Alocco

T. Alt

I. Altsybeev

C. Andrei

N. Andreou

A. Andronic

E. Andronov

M. Angeletti

V. Anguelov

F. Antinori

P. Antonioli

N. Apadula

H. Appelshäuser

S. Arcelli

R. Arnaldi

I. Arsene

M. Arslandok

A. Augustinus

R. Averbeck

M. Azmi

H. Baba

A. Babu

A. Badalà

J. Bae

Y. Bae

Y. Baek

X. Bai

R. Bailhache

Y. Bailung

R. Bala

A. Baldisseri

B. Balis

S. Bangalia

Z. Banoo

V. Barbasova

F. Barile

L. Barioglio

M. Barlou

B. Barman

Hungary

G. Barnaföldi

Measurements of the production of W $$^{\pm }$$ and Z $$^0$$ bosons in pp collisions at $$\sqrt{s} = 13$$ TeV