The half-life of $$^{39}$$ Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. Between 2016 and 2020, DEAP-3600 used a target mass of (3269 ± 24) kg of liquid argon distilled from the atmosphere in a direct-detection dark matter search. Such an argon mass also enables direct measurements of argon isotope properties. The decay of $$^{39}$$ Ar in DEAP-3600 is the dominant source of triggers by two orders of magnitude, ensuring high statistics and making DEAP-3600 well-suited for measuring this isotope’s half-life. Use of the pulse-shape discrimination technique in DEAP-3600 allows powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of $$^{39}$$ Ar decays. Observing over a period of 3.4 years, the $$^{39}$$ Ar half-life is measured to be $$(302 \pm 8_\textrm{stat} \pm 6_\textrm{sys})$$ years. This new direct measurement suggests that the half-life of $$^{39}$$ Ar is significantly longer than the accepted value, with potential implications for measurements using this isotope’s half-life as input.

Canada

P. Adhikari

R. Ajaj

Mexico

M. Alpízar-Venegas

P.A. Amaudruz

J. Anstey

D. Auty

M. Batygov

B. Beltran

M. Bigentini

C. Bina

Italy

W. Bonivento

M. Boulay

J. Bueno

M. Cadeddu

B. Cai

Spain

M. Cárdenas-Montes

S. Cavuoti

Y. Chen

Poland

S. Choudhary

B. Cleveland

R. Crampton

S. Daugherty

P. DelGobbo

P. Stefano

Russia

G. Dolganov

Germany

L. Doria

F. Duncan

M. Dunford

E. Ellingwood

A. Erlandson

S. Farahani

United Kingdom

N. Fatemighomi

G. Fiorillo

R. Ford

D. Gahan

D. Gallacher

A. Garai

P. García Abia

S. Garg

P. Giampa

A. Giménez-Alcázar

D. Goeldi

V. Golovko

P. Gorel

K. Graham

A. Grobov

A. Hallin

M. Hamstra

S. Haskins

J. Hu

J. Hucker

T. Hugues

A. Ilyasov

B. Jigmeddorj

C. Jillings

A. Joy

G. Kaur

A. Kemp

M. Khoshraftar Yazdi

M. Kuźniak

F. La Zia

United States

M. Lai

S. Langrock

B. Lehnert

J. LePage-Bourbonnais

N. Levashko

M. Lissia

L. Luzzi

I. Machulin

A. Maru

J. Mason

A. McDonald

T. McElroy

J. McLaughlin

C. Mielnichuk

L. Mirasola

A. Moharana

J. Monroe

A. Murray

C. Ng

G. Oliviéro

M. Olszewski

S. Pal

D. Papi

B. Park

M. Perry

V. Pesudo

Netherlands

T. Pollmann

F. Rad

C. Rethmeier

F. Retière

I. Rodríguez García

L. Roszkowski

R. Santorelli

F. Schuckman II

S. Seth

V. Shalamova

P. Skensved

T. Smirnova

K. Sobotkiewich

Direct measurement of the $$^{39}$$ Ar half-life from 3.4 years of data with the DEAP-3600 detector

Momentum correlation functions between <math><mi>π</mi><mo>,</mo><mo> </mo><mi>K</mi></math>, and <math><mi>p</mi></math> are calculated for several heavy-ion collision systems, namely <math><mrow><mmultiscripts><mi>B</mi><mprescripts></mprescripts><mn>5</mn><mn>10</mn></mmultiscripts><mo>+</mo><mmultiscripts><mi>B</mi><mprescripts></mprescripts><mn>5</mn><mn>10</mn></mmultiscripts></mrow><mo>,</mo><mo> </mo><mrow><mmultiscripts><mi>O</mi><mprescripts></mprescripts><mn>8</mn><mn>16</mn></mmultiscripts><mo>+</mo><mmultiscripts><mi>O</mi><mprescripts></mprescripts><mn>8</mn><mn>16</mn></mmultiscripts></mrow><mo>,</mo><mo> </mo><mrow><mmultiscripts><mi>Ca</mi><mprescripts></mprescripts><mn>20</mn><mn>40</mn></mmultiscripts><mo>+</mo><mmultiscripts><mi>Ca</mi><mprescripts></mprescripts><mn>20</mn><mn>40</mn></mmultiscripts></mrow></math>, and <math><mrow><mmultiscripts><mi>Au</mi><mprescripts></mprescripts><mn>79</mn><mn>197</mn></mmultiscripts><mo>+</mo><mmultiscripts><mi>Au</mi><mprescripts></mprescripts><mn>79</mn><mn>197</mn></mmultiscripts></mrow></math> in central collisions as well as <math><mrow><mmultiscripts><mi>Au</mi><mprescripts></mprescripts><mn>79</mn><mn>197</mn></mmultiscripts><mo>+</mo><mmultiscripts><mi>Au</mi><mprescripts></mprescripts><mn>79</mn><mn>197</mn></mmultiscripts></mrow></math> collision in different centralities at center-of-mass energy <math><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>39</mn></math> GeV within the framework of a multiphase transport model complemented by the Lednický and Lyuboshitz analytical method. The results present the centrality and system-size dependence of the momentum correlation functions among pairs of <math><mi>π</mi><mo>,</mo><mo> </mo><mi>K</mi></math>, and <math><mi>p</mi></math>, from which the emission source-size can be deduced. It is found that the deduced source sizes increase with the decreasing of centrality for Au <math><mo>+</mo></math> Au system or with the increasing of system size in central collisions with different nuclear size. In addition, through the momentum correlation functions of nonidentical particle pairs gated on velocity, the average emission sequence of nonidentical particles can be indicated. The results illustrate that in the small relative momentum region, protons are emitted in average earlier than <math><msup><mi>π</mi><mo>+</mo></msup></math> and <math><msup><mi>K</mi><mo>+</mo></msup></math>, and <math><msup><mi>K</mi><mo>+</mo></msup></math> are emitted averagely earlier than <math><msup><mi>π</mi><mo>+</mo></msup></math>. Furthermore, it seems that larger interval of the average emission order among them is exhibited for smaller collision systems. The present study sheds light on the dynamics of light particle emission at RHIC energy.

China

Ting-Ting Wang

Yu-Gang Ma

Song Zhang

Calculation of momentum correlation functions between <math><mi>π</mi><mo>,</mo><mo> </mo><mi>K</mi></math>, and <math><mi>p</mi></math> for several heavy-ion collision systems at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>39</mn></mrow></math> GeV

In this paper, the existence of a massive dark photon, associated with a new gauge group is considered. The dark photon can be kinetically mixed with the photon. To study some applications, the thermo field dynamics formalism is used. Exploring the topological structure of this approach, the influence of dark photons on the Stefan–Boltzmann law and the Casimir effect at zero and finite temperature is calculated.

Brazil

V. Prata

A. Santos

Faqir Khanna

Stefan–Boltzmann law and Casimir effect for dark photons

An evaluation method supported by robust statistical analysis was applied to historical measurements of  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar half-life. The method, based on the most frequent value (MFV) approach combined with bootstrap analysis, provides a more robust way to estimate  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar half-life, and results in  $$T_{1/2}($$  <math> <mrow> <msub> <mi>T</mi> <mrow> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </msub> <mrow> <mo>(</mo> </mrow> </mrow> </math>  MFV $$) = 268.2^{+3.1}_{-2.9}$$  <math> <mrow> <mrow> <mo>)</mo> <mo>=</mo> <mn>268</mn> <mo>.</mo> </mrow> <msubsup> <mn>2</mn> <mrow> <mo>-</mo> <mn>2.9</mn> </mrow> <mrow> <mo>+</mo> <mn>3.1</mn> </mrow> </msubsup> </mrow> </math>   years with uncertainty corresponding to the 68% confidence level. The uncertainty is a factor of 3 smaller than that of the most precise re-calculated  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar half-life measurements by Stoenner et al. and a factor of 2.7 smaller than that of the adopted half-life value in nuclear data sheets. Recently, the specific activity of the beta decay of  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar in atmospheric argon was measured in several underground facilities. Applying the MFV method to a specific activity of  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar from underground measurements results in  $$ SA_{{^{39}\text {Ar}}/\text {Ar}}(\text {MFV}) = 0.966^{+0.010}_{-0.018} \, \, \text {Bq/kg}_{\text {atmAr}}$$  <math> <mrow> <mi>S</mi> <msub> <mi>A</mi> <mrow> <mrow> <msup> <mrow></mrow> <mn>39</mn> </msup> <mtext>Ar</mtext> </mrow> <mo>/</mo> <mtext>Ar</mtext> </mrow> </msub> <mrow> <mo>(</mo> <mtext>MFV</mtext> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> <mo>.</mo> <msubsup> <mn>966</mn> <mrow> <mo>-</mo> <mn>0.018</mn> </mrow> <mrow> <mo>+</mo> <mn>0.010</mn> </mrow> </msubsup> <mspace width="0.166667em"></mspace> <mspace width="0.166667em"></mspace> <msub> <mtext>Bq/kg</mtext> <mtext>atmAr</mtext> </msub> </mrow> </math>   with uncertainty corresponding to the 68% confidence level. In this paper the method to determine the half-life of  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar using the specific activity of  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar in atmospheric argon is also discussed.

Victor Golovko

Application of the most frequent value method for  $$^{39}$$  <math> <msup> <mrow></mrow> <mn>39</mn> </msup> </math>  Ar half-life determination

The identification of jets originating from quarks and gluons, often referred to as quark/gluon tagging, plays an important role in various analyses performed at the Large Hadron Collider, as Standard Model measurements and searches for new particles decaying to quarks often rely on suppressing a large gluon-induced background. This paper describes the measurement of the efficiencies of quark/gluon taggers developed within the ATLAS Collaboration, using $\sqrt{s} = 13$ TeV proton–proton collision data with an integrated luminosity of 140 fb $^{-1}$ collected by the ATLAS experiment. Two taggers with high performances in rejecting jets from gluon over jets from quarks are studied: one tagger is based on requirements on the number of inner-detector tracks associated with the jet, and the other combines several jet substructure observables using a boosted decision tree. A method is established to determine the quark/gluon fraction in data, by using quark/gluon-enriched subsamples defined by the jet pseudorapidity. Differences in tagging efficiency between data and simulation are provided for jets with transverse momentum between 500 GeV and 2 TeV and for multiple tagger working points.

France

G. Aad

B. Abbott

K. Abeling

N.J. Abicht

S.H. Abidi

Morocco

A. Aboulhorma

Israel

H. Abramowicz

H. Abreu

Y. Abulaiti

B.S. Acharya

C. Adam Bourdarios

L. Adamczyk

S.V. Addepalli

M.J. Addison

J. Adelman

A. Adiguzel

T. Adye

A.A. Affolder

Switzerland

Y. Afik

M.N. Agaras

J. Agarwala

A. Aggarwal

Romania

C. Agheorghiesei

A. Ahmad

Azerbaijan

F. Ahmadov

W.S. Ahmed

S. Ahuja

X. Ai

G. Aielli

A. Aikot

M. Ait Tamlihat

B. Aitbenchikh

I. Aizenberg

M. Akbiyik

Sweden

T.P.A. Åkesson

A.V. Akimov

Japan

D. Akiyama

N.N. Akolkar

K. Al Khoury

G.L. Alberghi

J. Albert

P. Albicocco

G.L. Albouy

S. Alderweireldt

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

M. Aliev

G. Alimonti

W. Alkakhi

C. Allaire

B.M.M. Allbrooke

J.F. Allen

Chile

C.A. Allendes Flores

Performance and calibration of quark/gluon-jet taggers using 140 fb$^{−1}$ of $\textit{pp}$ collisions at ${{\sqrt{\boldsymbol s}\bf = 13}}$ TeV with the ATLAS detector * We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; ANID, Chile; CAS, MOST and NSFC, China; Minciencias, Colombia; MEYS CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS and CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF and MPG, Germany; GSRI, Greece; RGC and Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MEiN, Poland; FCT, Portugal; MNE/IFA, Romania; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DSI/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taipei; TENMAK, Türkiye; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, CANARIE, CRC and DRAC, Canada; PRIMUS 21/SCI/017 and UNCE SCI/013, Czech Republic; COST, ERC, ERDF, Horizon 2020, ICSC-Next Generation EU and Marie Skłodowska-Curie Actions, European Union; Investissements d'Avenir Labex, Investissements d'Avenir Idex and ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and MINERVA, Israel; Norwegian Financial Mechanism 2014-2021, Norway; NCN and NAWA, Poland; La Caixa Banking Foundation, CERCA Programme Generalitat de Catalunya and PROMETEO and GenT Programmes Generalitat Valenciana, Spain; Göran Gustafssons Stiftelse, Sweden; The Royal Society and Leverhulme Trust, United Kingdom.