<p>We generalize the nature of the so-called beam-dump “ceiling” beyond which the improvement on the sensitivity reach in the search for fast-decaying mediators dramatically slows down, and we point out its experimental implications that motivate tabletop-sized beam-dump experiments for the search. Light (bosonic) mediators are well-motivated new-physics particles, as they can appear in dark-sector portal scenarios and models to explain various laboratory-based anomalies. Due to their low mass and feebly interacting nature, beam-dump-type experiments, utilizing high-intensity particle beams, can play a crucial role in probing the parameter space of such visibly decaying mediators—in particular, the “prompt decay” region, where the mediators feature relatively large coupling and mass. We present a general and semianalytic proof that the ceiling effectively arises in the prompt-decay region of an experiment and show its insensitivity to data statistics, background estimates, and systematic uncertainties, considering a concrete example, the search for axion-like particles interacting with ordinary photons at three benchmark beam facilities: PIP-II at FNAL, and SPS and LHC-dump at CERN. We then identify optimal criteria to perform a cost-effective and short-term experiment to reach the ceiling, demonstrating that very short-baseline compact experiments enable access to the parameter space unreachable thus far.</p>

United States

Doojin Kim

Jaehoon Yu

South Korea

Jong-Chul Park

Hyunyong Kim

Beam-dump ceiling and its experimental implications: The case of a portable experiment

The azimuthal-correlation distributions between electrons from the decays of heavy-flavor hadrons and associated charged particles in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}} = 5.02$$ TeV are reported for the 0–10% and 30–50% centrality classes. This measurement provides access to the jet-like correlation observables in the heavy-flavor sector in Pb–Pb collisions. The analysis is performed for trigger electrons from heavy-flavor hadron decays with transverse momentum $$4< p_\textrm{T}^\textrm{e} < 16~\textrm{GeV}/c$$ , considering associated particles within the transverse-momentum range $$1< p_\textrm{T}^\textrm{assoc} < 7$$ $$\textrm{GeV}/c$$ , and a pseudorapidity difference of $$|\Delta \eta |<1$$ between the trigger electron and associated particles. The per-trigger nuclear modification factor ( $$I_\textrm{AA}$$ ) is calculated to compare the near- and away-side peak yields to those in pp collisions at $$\sqrt{s} = 5.02$$ TeV. In 0–10% central collisions, the $$I_\textrm{AA}$$ indicates a hint of enhancement of associated-particle yields with $$p_\textrm{T}<3$$ GeV/$\textit{c}$ on the near side, and a suppression of yields with $$p_\textrm{T}>4$$ GeV/$\textit{c}$ on the away side. The $$I_\textrm{AA}$$ for electron triggers from heavy-flavor hadron decays is compared with that for light-flavor and strange-particle triggers to investigate the dependence on different fragmentation processes and parton-medium dynamics, and is found to be the same within uncertainties.

I. Abualrob

Italy

S. Acharya

G. Aglieri Rinella

L. Aglietta

M. Agnello

N. Agrawal

India

Z. Ahammed

S. Ahmad

Slovakia

I. Ahuja

Indonesia

Z. Akbar

A. Akindinov

Germany

V. Akishina

M. Al-Turany

D. Aleksandrov

B. Alessandro

China

H. Alfanda

Mexico

R. Alfaro Molina

B. Ali

A. Alici

A. Alkin

Norway

J. Alme

G. Alocco

T. Alt

A. Altamura

I. Altsybeev

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

M. Azmi

Japan

H. Baba

A. Babu

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

G. Batigne

D. Battistini

B. Batyunya

D. Bauri

Peru

J. Alba

Denmark

I. Bearden

P. Becht

D. Behera

S. Behera

I. Belikov

V. Bella

F. Bellini

R. Bellwied

L. Beltran

Y. Beltran

G. Bencedi

A. Bensaoula

S. Beole

Y. Berdnikov

A. Berdnikova

L. Bergmann

L. Bernardinis

L. Betev

P. Bhaduri

T. Bhalla

A. Bhasin

B. Bhattacharjee

S. Bhattarai

L. Bianchi

Czechia

J. Bielčík

Medium-induced modification of azimuthal correlations of electrons from heavy-flavor hadron decays with charged particles in Pb–Pb collisions at $$\mathbf {\sqrt{s_{\textrm{NN}}} = 5.02}$$ TeV

<p>Super-Kamiokande (SK) has observed <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi mathvariant="normal">B</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>8</mn></mrow></mmultiscripts></mrow></math> solar neutrino elastic scattering at recoil electron kinetic energies (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>E</mi><mi>kin</mi></msub></math>) as low as 3.49 MeV to study neutrino flavor conversion within the Sun. At SK-observable energies, these conversions are dominated by the Mikheyev-Smirnov-Wolfenstein effect. An upturn in the electron neutrino survival probability in which vacuum neutrino oscillations become dominant is predicted to occur at lower energies, but radioactive background increases exponentially with decreasing energy. New machine learning approaches provide substantial background reduction below 3.49 MeV such that statistical extraction of solar neutrino interactions becomes feasible. This article presents an analysis of the solar neutrino interaction rate at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>E</mi><mi>kin</mi></msub><mo>&lt;</mo><mn>3.49</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> with the full SK-IV period, using data from a wideband intelligent trigger when available and with a boosted decision tree for event selection. A solar neutrino signal is observed between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2.99</mn><mtext> </mtext><mtext> </mtext><mrow><mi>MeV</mi></mrow><mo>&lt;</mo><msub><mi>E</mi><mi>kin</mi></msub><mo>&lt;</mo><mn>3.49</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2.76</mn><mi>σ</mi></math> significance and a data to unoscillated Monte Carlo ratio of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mn>0.307</mn><mrow><mo>−</mo><mn>0.111</mn></mrow><mrow><mo>+</mo><mn>0.112</mn></mrow></msubsup></math>. These additional low-energy data have a negligible effect on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mi>σ</mi></math> intervals of the fits to the solar neutrino energy spectrum but have a noticeable effect on the best fit when using the exponential parametrization.</p>

A. Yankelevich

K. Abe

Y. Asaoka

M. Harada

Y. Hayato

K. Hiraide

T.H. Hung

K. Hosokawa

K. Ieki

M. Ikeda

J. Kameda

Y. Kanemura

Y. Kataoka

S. Miki

S. Mine

M. Miura

S. Moriyama

K. Nakagiri

M. Nakahata

S. Nakayama

Y. Noguchi

G. Pronost

K. Sato

H. Sekiya

R. Shinoda

M. Shiozawa

Y. Suzuki

A. Takeda

Y. Takemoto

H. Tanaka

T. Yano

S. Chen

Y. Itow

T. Kajita

R. Nishijima

K. Okumura

T. Tashiro

T. Tomiya

X. Wang

Spain

F.J. de Garay Arcones

P. Fernandez

L. Labarga

D. Samudio

B. Zaldivar

C. Yanagisawa

B. Jargowsky

E. Kearns

J. Mirabito

L. Wan

T. Wester

Canada

B.W. Pointon

J. Bian

B. Cortez

N.J. Griskevich

Y. Jiang

M.B. Smy

H.W. Sobel

V. Takhistov

J. Hill

M.C. Jang

S.H. Lee

D.H. Moon

R.G. Park

B.S. Yang

B. Bodur

K. Scholberg

C.W. Walter

A. Beauchêne

O. Drapier

Measurement of the solar neutrino interaction rate below 3.49 MeV in Super-Kamiokande-IV