Beam dump experiments proposed at the SPS are perfectly suited to explore the parameter space of models with long-lived particles, thanks to the combination of a large intensity with a high proton beam energy. In this paper, we study how the exploration power may be augmented further by installing a detector based on liquid argon time projection chamber technology. In particular, we consider several signatures of new physics particles that may be uniquely searched for with such a detector, including double bang events with heavy neutral leptons, inelastic light dark matter, and millicharged particles.

Switzerland

Martina Ferrillo

Germany

Netherlands

Maksym Ovchynnikov

CERN

Filippo Resnati

Albert Roeck

Improving the potential of BDF@SPS to search for new physics with liquid argon time projection chambers

We report the first direct observation of neutrino interactions at a particle collider experiment. Neutrino candidate events are identified in a 13.6 TeV center-of-mass energy <math><mi>p</mi><mi>p</mi></math> collision dataset of <math><mrow><mn>35.4</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> using the active electronic components of the FASER detector at the Large Hadron Collider. The candidates are required to have a track propagating through the entire length of the FASER detector and be consistent with a muon neutrino charged-current interaction. We infer <math><mrow><msubsup><mrow><mn>153</mn></mrow><mrow><mo>−</mo><mn>13</mn></mrow><mrow><mo>+</mo><mn>12</mn></mrow></msubsup></mrow></math> neutrino interactions with a significance of 16 standard deviations above the background-only hypothesis. These events are consistent with the characteristics expected from neutrino interactions in terms of secondary particle production and spatial distribution, and they imply the observation of both neutrinos and anti-neutrinos with an incident neutrino energy of significantly above 200 GeV.

Israel

Henso Abreu

John Anders

Claire Antel

Japan

Akitaka Ariga

Tomoko Ariga

Jeremy Atkinson

Florian U. Bernlochner

Tobias Blesgen

Tobias Boeckh

Jamie Boyd

Lydia Brenner

Franck Cadoux

United States

David W. Casper

United Kingdom

Charlotte Cavanagh

China

Xin Chen

Italy

Andrea Coccaro

Ansh Desai

Sergey Dmitrievsky

Monica D’Onofrio

Yannick Favre

Deion Fellers

Jonathan L. Feng

Carlo Alberto Fenoglio

Didier Ferrere

Stephen Gibson

Sergio Gonzalez-Sevilla

Yuri Gornushkin

Carl Gwilliam

Daiki Hayakawa

Shih-Chieh Hsu

Zhen Hu

Giuseppe Iacobucci

Tomohiro Inada

Sune Jakobsen

Hans Joos

Enrique Kajomovitz

Hiroaki Kawahara

Alex Keyken

Felix Kling

Daniela Köck

Umut Kose

Rafaella Kotitsa

Susanne Kuehn

Helena Lefebvre

Lorne Levinson

Ke Li

Jinfeng Liu

Jack MacDonald

Chiara Magliocca

Fulvio Martinelli

Josh McFayden

Matteo Milanesio

Dimitar Mladenov

Théo Moretti

Magdalena Munker

Mitsuhiro Nakamura

Toshiyuki Nakano

Marzio Nessi

Friedemann Neuhaus

Laurie Nevay

Hidetoshi Otono

Hao Pang

Lorenzo Paolozzi

Brian Petersen

Francesco Pietropaolo

Markus Prim

Michaela Queitsch-Maitland

Hiroki Rokujo

Elisa Ruiz-Choliz

Jorge Sabater-Iglesias

Osamu Sato

Paola Scampoli

Kristof Schmieden

Matthias Schott

Anna Sfyrla

Savannah Shively

Yosuke Takubo

Noshin Tarannum

Ondrej Theiner

Eric Torrence

Serhan Tufanli

Svetlana Vasina

Benedikt Vormwald

Di Wang

Eli Welch

Stefano Zambito

First Direct Observation of Collider Neutrinos with FASER at the LHC

<math><mi>FASER</mi><mi>ν</mi></math> at the CERN Large Hadron Collider (LHC) is designed to directly detect collider neutrinos for the first time and study their cross sections at TeV energies, where no such measurements currently exist. In 2018, a pilot detector employing emulsion films was installed in the far-forward region of ATLAS, 480 m from the interaction point, and collected <math><mrow><mn>12.2</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> of proton-proton collision data at a center-of-mass energy of 13 TeV. We describe the analysis of this pilot run data and the observation of the first neutrino interaction candidates at the LHC. This milestone paves the way for high-energy neutrino measurements at current and future colliders.