Radiogenic neutrons emitted by detector materials are one of the most challenging backgrounds for the direct search of dark matter in the form of weakly interacting massive particles (WIMPs). To mitigate this background, the XENONnT experiment is equipped with a novel gadolinium-doped water Cherenkov detector, which encloses the xenon dual-phase time projection chamber (TPC). The neutron veto (NV) can tag neutrons via their capture on gadolinium or hydrogen, which release $$\gamma $$ -rays that are subsequently detected as Cherenkov light. In this work, we present the first results of the XENONnT NV when operated with demineralized water only, before the insertion of gadolinium. Its efficiency for detecting neutrons is $$({82\pm 1}){\%}$$ , the highest neutron detection efficiency achieved in a water Cherenkov detector. This enables a high efficiency of $$({53\pm 3}){\%}$$ for the tagging of WIMP-like neutron signals, inside a tagging time window of $${250}~{\upmu }\hbox {s}$$ between TPC and NV, leading to a livetime loss of $${1.6}{\%}$$ during the first science run of XENONnT.

United States

E. Aprile

Netherlands

J. Aalbers

Japan

K. Abe

France

S. Ahmed Maouloud

Germany

L. Althueser

B. Andrieu

Italy

E. Angelino

D. Antón Martin

United Arab Emirates

F. Arneodo

Switzerland

L. Baudis

M. Bazyk

L. Bellagamba

R. Biondi

A. Bismark

K. Boese

A. Brown

G. Bruno

Israel

R. Budnik

China

C. Cai

C. Capelli

Portugal

J. Cardoso

A. Cimental Chávez

A. Colijn

Sweden

J. Conrad

J. Cuenca-García

V. D’Andrea

L. Daniel Garcia

M. Decowski

A. Deisting

C. Di Donato

P. Di Gangi

S. Diglio

K. Eitel

S. el Morabit

A. Elykov

A. Ferella

C. Ferrari

H. Fischer

T. Flehmke

M. Flierman

W. Fulgione

C. Fuselli

P. Gaemers

R. Gaior

M. Galloway

F. Gao

S. Ghosh

R. Giacomobono

R. Glade-Beucke

L. Grandi

J. Grigat

H. Guan

M. Guida

P. Gyorgy

R. Hammann

A. Higuera

C. Hils

L. Hoetzsch

N. Hood

M. Iacovacci

Y. Itow

J. Jakob

F. Joerg

Y. Kaminaga

M. Kara

P. Kavrigin

S. Kazama

M. Kobayashi

D. Koke

A. Kopec

H. Landsman

R. Lang

L. Levinson

I. Li

S. Li

S. Liang

Y.T. Lin

S. Lindemann

M. Lindner

K. Liu

M. Liu

J. Loizeau

F. Lombardi

J. Long

J.A.M. Lopes

T. Luce

Y. Ma

C. Macolino

J. Mahlstedt

A. Mancuso

L. Manenti

F. Marignetti

T. Marrodán Undagoitia

K. Martens

J. Masbou

E. Masson

S. Mastroianni

A. Melchiorre

J. Merz

M. Messina

The neutron veto of the XENONnT experiment: results with demineralized water

The real Higgs singlet extension of the Standard Model (SM) without $\textit{Z}$ symmetry, the RxSM, is the simplest extension of the SM that features a First Order Electroweak Phase Transition (FOEWPT) in the early universe. The FOEWPT is one of the requirements needed for electroweak baryogenesis to explain the baryon asymmetry of the universe (BAU). Thus, the RxSM is a perfect example to study features related to the FOEWPT at current and future collider experiments. The RxSM has two $$ \mathcal{CP} $$ -even Higgs bosons, $\textit{h}$ and $\textit{H}$, with masses $\textit{m}$ $\textit{< m}$ , where we assume that $\textit{h}$ corresponds to the Higgs boson discovered at the LHC. Our analysis is based on a benchmark plane that ensures the occurence of a strong FOEWPT, where $\textit{m}$ $\textit{>}$ 2$\textit{m}$ is found. In a first step we analyze the di-Higgs production at the (HL-)LHC, $\textit{gg → hh}$, with a focus on the impact of the trilinear Higgs couplings (THCs), $\textit{λ}$ and $\textit{λ}$ . The interferences of the resonant $\textit{H}$-exchange diagram involving $\textit{λ}$ and the non-resonant diagrams result in a characteristic peak-dip (or dip-peak) structure in the $\textit{m}$ distribution. We analyze how $\textit{λ}$ can be accessed, taking into account the experimental smearing and binning. We also demonstrate that the approximation used by ATLAS and CMS for the resonant di-Higgs searches may fail to capture the relevant effects and lead to erroneous results. In a second step we analyze the benchmark plane at a future high-energy $\textit{e}$ $\textit{e}$ collider with $$ \sqrt{s} $$ = 1000 GeV (ILC1000). We analyze the potential sensitivity to $\textit{λ}$ via an experimental determination at the ILC1000 and demonstrate that it is nearly independent of the heavy Higgs-boson mass, as long as it is kinematically accessible.

F. Arco

Spain

S. Heinemeyer

M. Mühlleitner

A. Parra Arnay

N. Rivero González

A. Verduras Schaeidt

Sensitivity to triple Higgs couplings via di-Higgs production in the RxSM at the (HL-)LHC and future $\textit{e}$

<p>Using <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> collision data corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>10.6</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> collected at center-of-mass energies between 4.258 and 4.681 GeV with the BESIII detector at the BEPCII collider, we search for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>1</mn><mrow><mo>−</mo><mo>+</mo></mrow></msup></math> charmoniumlike hybrid via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msub><mi>η</mi><mi>c</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><msup><mi>η</mi><mo>′</mo></msup><msub><mi>η</mi><mi>c</mi></msub></math> decays for the first time. No significant signal is observed, and the upper limits on the Born cross sections for both processes are set at the 90% confidence level.</p>

M. Ablikim

Russia

M.N. Achasov

P. Adlarson

X.C. Ai

R. Aliberti

A. Amoroso

Q. An

Y. Bai

JINR

O. Bakina

Y. Ban

H.R. Bao

Poland

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M. Bertani

D. Bettoni

F. Bianchi

E. Bianco

A. Bortone

I. Boyko

R.A. Briere

A. Brueggemann

H. Cai

M.H. Cai

X. Cai

A. Calcaterra

G.F. Cao

N. Cao

Türkiye

S.A. Cetin

X.Y. Chai

J.F. Chang

G.R. Che

Y.Z. Che

C.H. Chen

Chao Chen

G. Chen

H.S. Chen

H.Y. Chen

M.L. Chen

S.J. Chen

S.L. Chen

S.M. Chen

T. Chen

X.R. Chen

X.T. Chen

X.Y. Chen

Y.B. Chen

Y.Q. Chen

Z.J. Chen

Z.K. Chen

South Korea

S.K. Choi

X. Chu

G. Cibinetto

F. Cossio

United Kingdom

J. Cottee-Meldrum

J.J. Cui

H.L. Dai

J.P. Dai

A. Dbeyssi

R.E. de Boer

D. Dedovich

C.Q. Deng

Z.Y. Deng

A. Denig

I. Denysenko

M. Destefanis

F. De Mori

B. Ding

X.X. Ding

Search for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>1</mn><mrow><mo>−</mo><mo>+</mo></mrow></msup></math> charmoniumlike hybrid via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><mi>γ</mi><msup><mrow><mi>η</mi></mrow><mrow><mo stretchy="false">(</mo><mo>′</mo><mo stretchy="false">)</mo></mrow></msup><msub><mrow><mi>η</mi></mrow><mrow><mi>c</mi></mrow></msub></mrow></math> at center-of-mass energies between 4.258 and 4.681 GeV