Recent anomalies observed in $ e^+e^- $ nuclear transitions of $ ^8 {{\rm{Be}}} $ , $ ^4 {\rm{He}} $ , and $ ^{12} {\rm{C}} $ by the ATOMKI collaboration may hint at the existence of a vector boson with a mass around 17 MeV, which is referred to as X17. If it exists, this boson would affect similar processes in particle physics, including the Dalitz decays of vector mesons. Recently, the BESIII collaboration measured the Dalitz decay $ D^{*0}\to D^0e^+e^- $ for the first time and reported a $ 3.5\sigma $ excess over the theoretical prediction based on the vector meson dominance (VMD) model. This excess may be another signal of X17. In this study, we investigate the possible effects of X17 on the Dalitz decays $ D^*_{(s)}\to D_{(s)}e^+e^- $ , $ B^*_{(s)}\to B_{(s)}e^+e^- $ , and $ J/\psi\to \eta_ce^+e^- $ . The required hadronic form factors are calculated within the framework of our covariant confined quark model without relying on heavy quark effective theory or the VMD model. We present predictions for the Dalitz decay widths and the ratios $ R_{ee}(V)\equiv \Gamma(V\to Pe^+e^-)/\Gamma(V\to P\gamma) $ within the standard model and in several new physics scenarios involving modifications attributed to X17. Our results are compared with other theoretical calculations.

Vietnam

C.T. Tran

Russia

M.A. Ivanov

A.T.T. Nguyen

Probing the ATOMKI X17 vector boson using Dalitz decays $\textit{V}$ → $\textit{Pe}$ $^{+}$ $\textit{e}$ $^{−}$ * Supported by Ho Chi Minh City University of Technology and Education (T2024-65)

In this study, we utilize light-cone QCD sum rules at twist-3 accuracy to compute the coupling parameters of the $$\chi _{c1}(2P)$$ state with $\textit{D}$ and $$D^*$$ mesons. The analysis reveals that the observed $$\chi _{c1}(3872)$$ meson incorporates significant amounts of both charmonium and molecular components. The interplay between these components highlights the exotic nature of $$\chi _{c1}(3872)$$ . Furthermore, implications for a possible mixing between the $$\chi _{b1}(2P)$$ state and a potential $$B\bar{B}^*$$ molecule is discussed. These findings contribute to the understanding of exotic hadron states and their intricate internal structures.

Türkiye

T. Akan

Mehmet Olpak

A. Özpineci

Charmonium content of $$\chi _{c1}(3872)$$ in light-cone sum rules at twist 3

Using (2712$\textit{.}$4 $\textit{±}$ 14$\textit{.}$3) $\textit{×}$ 10 $\textit{ψ}$(3686) candidates collected by the BESIII detector operating at the BEPCII storage ring, the decays $$ {\chi}_{cJ}\left(J=0,1,2\right)\to p\overline{p}\eta \eta $$ are observed for the first time through the radiative transition $\textit{ψ}$(3686) $\textit{→ γχ}$ . The statistical significances for $\textit{χ}$ signals are all larger than 5$\textit{σ}$. The branching fractions of $$ {\chi}_{c0,1,2}\to p\overline{p}\eta \eta $$ are determined to be (5$\textit{.}$75 ± 0$\textit{.}$59 ± 0$\textit{.}$42) × 10 , (1$\textit{.}$40 ± 0$\textit{.}$33 ± 0$\textit{.}$17) × 10 , and (2$\textit{.}$64 ± 0$\textit{.}$40 ± 0$\textit{.}$27) × 10 , respectively, where the first uncertainties are statistical and the second systematic. No evident resonant structures are found in the $$ p\overline{p} $$ and $$ p\eta /\overline{p}\eta $$ systems.

China

M. Ablikim

M. Achasov

Sweden

P. Adlarson

X. Ai

Germany

R. Aliberti

Italy

A. Amoroso

Q. An

Y. Bai

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

United States

R. Briere

A. Brueggemann

H. Cai

M. Cai

X. Cai

A. Calcaterra

G. Cao

N. Cao

S. Cetin

X. Chai

J. Chang

G. Che

Y. Che

G. Chelkov

C. Chen

Chao Chen

G. Chen

H. Chen

M. Chen

S. Chen

T. Chen

X. Chen

Y. Chen

Z. Chen

South Korea

S. Choi

X. Chu

G. Cibinetto

F. Cossio

J. Cui

H. Dai

J. Dai

A. Dbeyssi

R. Boer

D. Dedovich

C. Deng

Z. Deng

A. Denig

I. Denysenko

M. Destefanis

F. Mori

B. Ding

X. Ding

Y. Ding

J. Dong

L. Dong

M. Dong

X. Dong

M. Du

S. Du

Y. Duan

Z. Duan

P. Egorov

G. Fan

J. Fan

Y. Fan

J. Fang

S. Fang

W. Fang

Y. Fang

R. Farinelli

L. Fava

F. Feldbauer

G. Felici

C. Feng

J. Feng

Y. Feng

M. Fritsch

C. Fu

J. Fu

Observation of $$ {\chi}_{cJ}\left(J=0,1,2\right)\to p\overline{p}\eta \eta $$

This paper presents the first measurement of $$\psi {(2S)}$$ and $$\chi _{c1}(3872)$$ meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed via its decay to the $${{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} $$ ( $$\rightarrow $$ $$\mu ^+\mu ^-$$ ) $$\pi ^+\pi ^-$$ final state in the forward region using proton-proton collision data collected by the LHCb experiment at the center-of-mass-energy of $$13\text {TeV} $$ in 2016, corresponding to an integrated luminosity of $$1.64\,\text {\,fb} ^{-1} $$ . The fragmentation function, presented as the ratio of the quarkonium-tag transverse momentum to the full jet transverse momentum ( $$p_{\textrm{T}} (\text {tag})/p_{\textrm{T}} (\text {jet})$$ ), is measured differentially in $$p_{\textrm{T}} (\text {jet})$$ and $$p_{\textrm{T}} (\text {tag})$$ bins. The distributions are separated into promptly produced quarkonia from proton-proton collisions and quarkonia produced from displaced $\textit{b}$-hadron decays. While the displaced quarkonia fragmentation functions are in general well described by parton-shower predictions, the prompt quarkonium distributions differ significantly from fixed-order non-relativistic QCD (NRQCD) predictions followed by a QCD parton shower.

Netherlands

R. Aaij

United Kingdom

A. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

A. Adefisoye

Spain

B. Adeva

M. Adinolfi

France

C. Agapopoulou

C. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

P. Albicocco

J. Albrecht

F. Alessio

M. Alexander

Z. Aliouche

P. Alvarez Cartelle

R. Amalric

Brazil

S. Amato

J. Amey

Y. Amhis

L. An

L. Anderlini

M. Andersson

A. Andreianov

P. Andreola

M. Andreotti

D. Andreou

A. Anelli

D. Ao

F. Archilli

M. Argenton

Costa Rica

S. Arguedas Cuendis

A. Artamonov

M. Artuso

E. Aslanides

R. Ataíde Da Silva

M. Atzeni

B. Audurier

D. Bacher

I. Bachiller Perea

S. Bachmann

M. Bachmayer

J. Back

P. Baladron Rodriguez

V. Balagura

W. Baldini

L. Balzani

H. Bao

J. Baptista de Souza Leite

C. Barbero Pretel

M. Barbetti

I. Barbosa

R. Barlow

M. Barnyakov

S. Barsuk

W. Barter

M. Bartolini

J. Bartz

J. Basels

S. Bashir

G. Bassi

B. Batsukh

P. Battista

A. Bay

A. Beck

M. Becker

F. Bedeschi

I. Bediaga

N. Behling

S. Belin

V. Bellee

K. Belous

I. Belov

I. Belyaev

G. Benane

G. Bencivenni

E. Ben-Haim

Measurements of $$\psi (2S)$$ and $$\chi _{c1}(3872)$$ production within fully reconstructed jets