There is a long-standing anomaly in the ratio of the decay width for  $$\psi (3770)\rightarrow D^0\overline{D^0}$$  <math> <mrow> <mi>ψ</mi> <mrow> <mo>(</mo> <mn>3770</mn> <mo>)</mo> </mrow> <mo>→</mo> <msup> <mi>D</mi> <mn>0</mn> </msup> <mover> <msup> <mi>D</mi> <mn>0</mn> </msup> <mo>¯</mo> </mover> </mrow> </math>   to that for  $$\psi (3770)\rightarrow D^+D^-$$  <math> <mrow> <mi>ψ</mi> <mrow> <mo>(</mo> <mn>3770</mn> <mo>)</mo> </mrow> <mo>→</mo> <msup> <mi>D</mi> <mo>+</mo> </msup> <msup> <mi>D</mi> <mo>-</mo> </msup> </mrow> </math>   at the level of  $$9.5\,\sigma $$  <math> <mrow> <mn>9.5</mn> <mspace width="0.166667em"></mspace> <mi>σ</mi> </mrow> </math>  . A similar anomaly exists for the ratio of  $$\phi (1020)\rightarrow K_\text {L}^0K_\text {S}^0$$  <math> <mrow> <mi>ϕ</mi> <mrow> <mo>(</mo> <mn>1020</mn> <mo>)</mo> </mrow> <mo>→</mo> <msubsup> <mi>K</mi> <mtext>L</mtext> <mn>0</mn> </msubsup> <msubsup> <mi>K</mi> <mtext>S</mtext> <mn>0</mn> </msubsup> </mrow> </math>   to  $$\phi (1020)\rightarrow K^+K^-$$  <math> <mrow> <mi>ϕ</mi> <mrow> <mo>(</mo> <mn>1020</mn> <mo>)</mo> </mrow> <mo>→</mo> <msup> <mi>K</mi> <mo>+</mo> </msup> <msup> <mi>K</mi> <mo>-</mo> </msup> </mrow> </math>   at  $$2.1\,\sigma $$  <math> <mrow> <mn>2.1</mn> <mspace width="0.166667em"></mspace> <mi>σ</mi> </mrow> </math>  . In this study, we reassess the anomaly through the lens of a Gaussian wave-packet formalism. Our comprehensive calculations include the localization of the overlap of the wave packets near the mass thresholds and the composite nature of the initial-state vector mesons. The results align within a  $$\sim 1 \sigma $$  <math> <mrow> <mo>∼</mo> <mn>1</mn> <mi>σ</mi> </mrow> </math>   confidence level with the Particle Data Group’s central values for a physically reasonable value of the form-factor parameter, indicating a resolution to these anomalies. We also check the deviation of a wave-packet resonance from the Briet–Wigner shape and find that wide ranges of the wave-packet size are consistent with the experimental data.

Japan

Kenzo Ishikawa

Osamu Jinnouchi

India

Kenji Nishiwaki

Kin-ya Oda

Wave-packet effects: a solution for isospin anomalies in vector-meson decay

A variety of new-physics models predict metastable particles whose decay length is ≲ 1 mm. Conventional displaced-vertex searches are less sensitive to this sub-millimeter decay range, and thus such metastable particles have been looked for only in usual prompt decay searches. In this paper, we show that an additional event-selection cut based on the vertex reconstruction using charged tracks considerably improves the sensitivity of ordinary searches which rely only on kinematic selection criteria, for particles with a decay length of ≳ 100 μm. To that end, we consider a metastable gluino as an example, and study the impact of this new event-selection cut on gluino searches at the LHC by simulating both the signal and Standard Model background processes. Uncertainty of the displaced-vertex reconstruction due to the limited resolution of track reconstruction is taken into account. We also discuss possibilities for optimization of the kinematic selection criteria, which takes advantage of significant reduction of background through the requirement of displaced vertices. In addition, we demonstrate that using the method discussed in this paper it is possible to measure the lifetime of metastable particles with an  <math><mi>O</mi><mfenced><mn>1</mn></mfenced></math> $$ \mathcal{O}(1) $$ accuracy at the high-luminosity LHC. Implications for a future 100 TeV collider are also studied, where produced particles tend to be more boosted and thus it is easier to detect the longevity of metastable particles.

Hayato Ito

Takeo Moroi

Natsumi Nagata

Hidetoshi Otono

Searching for metastable particles with sub-millimeter displaced vertices at hadron colliders

Particles with a sub-millimeter decay length appear in many models of physics beyond the Standard Model. However, their longevity has been often ignored in their LHC searches and they have been regarded as promptly-decaying particles. In this letter, we show that, by requiring displaced vertices on top of the event selection criteria used in the ordinary search strategies for promptly-decaying particles, we can considerably extend the LHC reach for particles with a decay length of <math><mo>≳</mo><mn>100</mn><mtext> </mtext><mtext>μm</mtext></math>. We discuss a way of reconstructing sub-millimeter displaced vertices by exploiting the same technique used for the primary vertex reconstruction on the assumption that the metastable particles are always pair-produced and their decay products contain high-<math><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math> jets. We show that, by applying a cut based on displaced vertices on top of standard kinematical cuts for the search of new particles, the LHC reach can be significantly extended if the decay length is <math><mo>≳</mo><mn>100</mn><mtext> </mtext><mtext>μm</mtext></math>. In addition, we may measure the lifetime of the target particle through the reconstruction of displaced vertices, which plays an important role in understanding the new physics behind the metastable particles.

Extending the LHC reach for new physics with sub-millimeter displaced vertices

The search for high-mass diphoton resonance is ongoing at the LHC, and will provide definite evidence of physics beyond the Standard Model once it is discovered. Along with the diphoton resonance, many theoretical models also predict resonances decaying not into a pair of photons but into a pair of highly collimated photon-jets. In this paper, we study how well we can distinguish such diphoton resonance imposters, i.e. diphoton-jet resonances, from diphoton resonances by examining detector responses to the photon-jets. We find that the sum of pT of the first e+e− pair from the photon conversion provides strong discrimination power. We also discuss determination of the lifetime of the light intermediate particle by measuring the photon conversion points.

Hajime Fukuda

Masahiro Ibe

Mihoko Nojiri

Cracking down on fake photons: Cases of diphoton resonance imposters

The prompt and non-prompt production cross-sections for ψ (2S) mesons are measured using 2.1 fb −1 of pp collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. The measurement exploits the ψ (2S) → J/ψ (→ μ + μ − ) π + π − decay mode, and probes ψ (2S) mesons with transverse momenta in the range 10 ≤ p T &lt; 100 GeV and rapidity | y | &lt; 2 . 0. The results are compared to other measurements of ψ (2S) production at the LHC and to various theoretical models for prompt and non-prompt quarkonium production.

France

Georges Aad

United States

Brad Abbott

China

Jalal Abdallah

Samah Abdel Khalek

Azerbaijan

Ovsat Abdinov

Netherlands

Rosemarie Aben

Babak Abi

Maris Abolins

Canada

Ossama AbouZeid

Israel

Halina Abramowicz

Henso Abreu

CERN

Ricardo Abreu

Sweden

Yiming Abulaiti

United Kingdom

Bobby Samir Acharya

Poland

Leszek Adamczyk

David Adams

Jahred Adelman

Germany

Stefanie Adomeit

Tim Adye

Montenegro

Tatjana Agatonovic-Jovin

Spain

Juan Antonio Aguilar-Saavedra

Switzerland

Marco Agustoni

Steven Ahlen

Faig Ahmadov

Italy

Giulio Aielli

Henrik Akerstedt

Torsten Paul Ake Åkesson

Ginga Akimoto

Russia

Andrei Akimov

Gian Luigi Alberghi

Justin Albert

Solveig Albrand

Argentina

Maria Josefina Alconada Verzini

Martin Aleksa

Igor Aleksandrov

Romania

Calin Alexa

Gideon Alexander

Gauthier Alexandre

Greece

Theodoros Alexopoulos

Muhammad Alhroob

Gianluca Alimonti

Lion Alio

John Alison

Benedict Allbrooke

Lee John Allison

Phillip Allport

John Almond

Alberto Aloisio

Denmark

Alejandro Alonso

Francisco Alonso

Cristiano Alpigiani

Andrew David Altheimer

Barbara Alvarez Gonzalez

Mariagrazia Alviggi

Katsuya Amako

Brazil

Yara Amaral Coutinho

Christoph Amelung

Dante Amidei

Portugal

Susana Patricia Amor Dos Santos

Antonio Amorim

Simone Amoroso

Nir Amram

Glenn Amundsen

Christos Anastopoulos

Lucian Stefan Ancu

Nansi Andari

Timothy Andeen

Christoph Falk Anders

Gabriel Anders

Kelby Anderson

Attilio Andreazza

George Victor Andrei

Xabier Anduaga

Stylianos Angelidakis

Ivan Angelozzi

Philipp Anger

Aaron Angerami

Francis Anghinolfi

Alexey Anisenkov

Nuno Anjos

Alberto Annovi

Ariadni Antonaki

Mario Antonelli

Alexey Antonov

Slovakia

Jaroslav Antos

Fabio Anulli

Masato Aoki

Ludovica Aperio Bella

Rudi Apolle

Giorgi Arabidze

Ignacio Aracena

Yasuo Arai

Juan Pedro Araque

Ayana Arce

Jean-Francois Arguin

Spyridon Argyropoulos

Türkiye

Metin Arik

Aaron James Armbruster

Olivier Arnaez

Vanessa Arnal

Measurement of the production cross-section of ψ (2S) → J/ψ (→ μ + μ − ) π + π − in pp collisions at s $$ \sqrt{s} $$ = 7 TeV at ATLAS