This study explores the structure of compact stars using an extended theory of gravity known as <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi><mo stretchy='false'>)</mo></math> gravity, where <math altimg='si3.svg'><mi mathvariant='script'>R</mi></math>, is the Ricci scalar, <math altimg='si4.svg'><mi mathvariant='script'>G</mi></math>, the Gauss-Bonnet invariant, and <math altimg='si5.svg'><mi mathvariant='script'>T</mi></math> the trace of the energy-momentum tensor. Focusing on massive radio pulsars, specifically neutron stars with masses greater than 1.8 solar masses, utilize these extreme astrophysical environments to test gravity in regimes unreachable by Earth-based experiments. We adopt a linear form of the theory, <math altimg='si18.svg'><mi>f</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mi mathvariant='script'>R</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>&#945;</mi><mi mathvariant='script'>G</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>&#946;</mi><mi mathvariant='script'>T</mi></math>, with <italic>&#945;</italic>, <cross-ref refid='fn0010' id='crf0390'>1</cross-ref> and <italic>&#946;</italic> are dimensional constants, and derive an exact analytical solution for anisotropic perfect fluid spheres in hydrostatic equilibrium. This model incorporates the compactness factor <math altimg='si7.svg'><mi>C</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mn>2</mn><mi>G</mi><mi>M</mi></mrow><mrow><mi>R</mi><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math>, to describe all physical properties within the stellar interior. To constrain the model, we employ observational data from the pulsar <italic>U</italic>1724, using its mass and radius to fix the parameters at their upper bounds: <math altimg='si8.svg'><msub><mrow><mi>&#945;</mi></mrow><mrow><mn>1</mn></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>&#945;</mi></mrow><mrow><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo>&#177;</mo><mn>0.023</mn></math> and <math altimg='si9.svg'><msub><mrow><mi>&#946;</mi></mrow><mrow><mn>1</mn></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>&#946;</mi></mrow><mrow><msup><mrow><mi>&#954;</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo>&#177;</mo><mn>0.001</mn></math>. The resulting model is consistent with physical viability and observational constraints. Notably, the squared sound speed in this framework remains below the theoretical limit ( <math altimg='si10.svg'><mmultiscripts><mrow><mtext mathvariant='normal'>c</mtext></mrow><mrow><mi>s</mi></mrow><none /><none /><mrow><mn>2</mn></mrow></mmultiscripts><mo linebreak='goodbreak' linebreakstyle='after'>&lt;</mo><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup><mo stretchy='false'>/</mo><mn>3</mn></math>), contrasting with general relativity results. Without assuming a specific equation of state, the model exhibits linear behavior and predicts a core density several times higher than nuclear saturation density ( <math altimg='si11.svg'><msub><mrow><mi>&#961;</mi></mrow><mrow><mtext>nuc</mtext></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>2.6</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup></math> g/cm 3), with surface density <math altimg='si12.svg'><msub><mrow><mi>&#961;</mi></mrow><mrow><mi>s</mi></mrow></msub></math>, also exceeding this threshold. Additionally, the derived mass-radius relation agrees well with existing astrophysical observations.

Egypt

South Africa

G.G.L. Nashed

Constraining linear form of <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo></math> gravity from astrophysical observations of the Pulsar U1724

The arrival time of electromagnetic signals traveling in chiral cosmic media is investigated in the context of Maxwell-Carroll-Field-Jackiw electrodynamics. Considering the interstellar medium (ISM) as a cold, ionized, chiral plasma, we derive the time delay between two traveling signals, expressed in terms of a modified dispersion measure (DM) which receives additional contribution from the chiral parameters. Faraday rotation angle is also addressed in this chiral plasma scenario, yielding modified rotation measures (RM). Using DMs data from five pulsars, we establish constraints on the chiral parameter magnitude at the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>23</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>22</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>. On the other hand, the Faraday rotation retrieved from RM measurements implied upper constraints as tight as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>36</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>.

Brazil

Filipe S. Ribeiro

Pedro D.S. Silva

Manoel M. Ferreira

Constraining <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi><mi>T</mi></mrow></math>-odd electromagnetic chiral parameters with pulsar timing

In this paper, we investigate regular black hole solutions in the (2+1)-dimensional versions of general relativity and $\textit{f}$($\textit{R}$, $\textit{T}$) gravity, both coupled to nonlinear electrodynamics. By admitting that the matter content that generates such geometries satisfies the Maxwell limit condition, we obtain a class of regular black holes that give rise to new solutions and successfully reproduce particular cases found in earlier studies of (2+1)-dimensional general relativity. Moreover, we discover the first regular black hole solutions in (2+1)-dimensional $\textit{f}$($\textit{R}$, $\textit{T}$) gravity and explore both qualitatively and quantitatively the non-conservation of the energy–momentum tensor present in those solutions.

Portugal

Miguel Pinto

Roberto Maluf

Spain

Gonzalo Olmo

Regular black hole solutions in $$(2 + 1)$$ -dimensional $\textit{f}$($\textit{R}$, $\textit{T}$) gravity coupled to nonlinear electrodynamics

The first observation of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>5.4</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>, collected with the LHCb detector at a center-of-mass energy of 13 TeV. A yield of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>237</mn><mo>±</mo><mn>16</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi mathvariant="normal">Σ</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> decays is obtained, where the uncertainty is statistical only. A branching fraction of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><mn>1.08</mn><mo>±</mo><mn>0.17</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>8</mn></mrow></msup></mrow></math> is measured, where the uncertainty includes statistical and systematic sources. No evidence of resonant structures is found in the dimuon invariant-mass distribution. All results are compatible with standard model expectations. This represents the rarest decay of a baryon ever observed.

Netherlands

R. Aaij

United Kingdom

A.S.W. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

United States

A.A. Adefisoye

B. Adeva

M. Adinolfi

P. Adlarson

France

C. Agapopoulou

C.A. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

Italy

P. Albicocco

Germany

J. Albrecht

CERN

F. Alessio

Z. Aliouche

P. Alvarez Cartelle

R. Amalric

S. Amato

J.L. Amey

Y. Amhis

China

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.J. Back

P. Baladron Rodriguez

V. Balagura

A. Balboni

W. Baldini

L. Balzani

H. Bao

J. Baptista de Souza Leite

C. Barbero Pretel

M. Barbetti

I.R. Barbosa

R.J. Barlow

M. Barnyakov

S. Barsuk

W. Barter

J. Bartz

Poland

S. Bashir

B. Batsukh

P.B. Battista

A. Bay

A. Beck

M. Becker

F. Bedeschi

I.B. Bediaga

N.A. Behling

S. Belin

K. Belous

I. Belov

I. Belyaev

G. Benane

G. Bencivenni

E. Ben-Haim

A. Berezhnoy

R. Bernet

S. Bernet Andres

A. Bertolin

C. Betancourt

F. Betti

J. Bex

Ia. Bezshyiko

O. Bezshyyko

J. Bhom

M.S. Bieker

N.V. Biesuz

P. Billoir

A. Biolchini

M. Birch

F.C.R. Bishop

A. Bitadze

A. Bizzeti

T. Blake

F. Blanc

J.E. Blank

S. Blusk

V. Bocharnikov

Observation of the Very Rare <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi mathvariant="normal">Σ</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> Decay

We explore dark matter phenomenology in Myrzakulov <math altimg='si1.svg'><mi>F</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo stretchy='false'>)</mo></math> gravity, formulated via the vielbein approach in Weitzenb&#246;ck spacetime. In this torsion-based extension of gravity, dark matter emerges as a geometric effect rather than a particle species, with curvature and torsion contributing dynamically to the field equations.

Davood Momeni

Kazakhstan

Ratbay Myrzakulov

Dark matter constraints in Myrzakulov <italic>F</italic>( <italic>R</italic>, <italic>T</italic>) gravity: A vielbein approach in Weitzenb&#246;ck spacetime with observational data

The first observation of the $${{{{\varXi } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }}$$ decay and the most precise measurement of the branching fraction of the $${{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} }$$ decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016–2018 at a centre-of-mass energy of 13 $$\text {\,Te\hspace{-1.00006pt}V}$$ , corresponding to an integrated luminosity of 5.4 $$\text {\,fb} ^{-1}$$ . Using the $${{{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {\varLambda } }}$$ and $${{{{\varXi } ^-_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} }}$$ decays as normalisation channels, the ratios of branching fractions are measured to be where the first uncertainty is statistical and the second systematic.

A. Abdelmotteleb

C. Beteta

A. Adefisoye

Sweden

C. Aidala

M. Alexander

P. Cartelle

J. Amey

S. Cuendis

R. Silva

I. Perea

J. Back

P. Rodriguez

J. Souza Leite

C. Pretel

I. Barbosa

R. Barlow

J. Basels

G. Bassi

P. Battista

I. Bediaga

N. Behling

S. Andres

M. Bieker

N. Biesuz

F. Bishop

J. Blank

Observation of the $${{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} }$$ and $${{{{\varXi } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }}$$ decays

The ratio of prompt production cross-sections of $\textit{ψ}$(2$\textit{S}$) and $\textit{J/ψ}$ mesons in their dimuon final state is measured as a function of centrality, using data collected by the LHCb detector in PbPb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ = 5$\textit{.}$02 TeV, for the first time in the forward rapidity region. The measured ratio shows no dependence on the collision centrality, and is compared to the latest theory predictions and to the recent measurements in literature.

M. Bartolini

Measurement of the $\textit{ψ}$(2S) to J$\textit{/ψ}$ cross-section ratio as a function of centrality in PbPb collisions at $$ \sqrt{{\textrm{s}}_{\textrm{NN}}} $$ = 5$\textit{.}$02 TeV

The self-dual condition, which ensures invariance under electromagnetic duality, manifests as a partial differential equation in nonlinear electromagnetism theories. The general solution to this equation is expressed in terms of an auxiliary field, $\textit{τ}$, and Courant-Hilbert functions, $\textit{ℓ}$($\textit{τ}$), which depend on $\textit{τ}$. Recent studies have shown that duality-invariant nonlinear electromagnetic theories fulfill the principle of causality under the conditions $$ \frac{\partial \ell }{\partial \tau}\ge 1 $$ and $$ \frac{\partial^2\ell }{\partial {\tau}^2}\ge 0 $$ .

H. Babaei-Aghbolagh

Iran

Komeil Babaei Velni

Song He

Zahra Pezhman

Root- $$ T\overline{T} $$ deformations on causal self-dual electrodynamic theories

A test of lepton universality between muons and electrons is performed using $\textit{B}$ → $\textit{K}$ $\textit{ℓ}$ $\textit{ℓ}$ decays (where $\textit{ℓ}$ = $\textit{e}$, $\textit{μ}$), in the dilepton invariant-mass-squared region above 14.3 GeV $\textit{/c}$ . The data used for the measurement consists of beauty meson decays produced in proton-proton collisions, corresponding to an integrated luminosity of 9 fb , collected by the LHCb experiment between 2011 and 2018. The ratio of branching fractions for $\textit{B}$ $\textit{→ K}$ $\textit{μ}$ $\textit{μ}$ and $\textit{B}$ $\textit{→ K}$ $\textit{e}$ $\textit{e}$ decays is measured to be $$ {R}_K=1.0{8}_{-0.09}^{+0.11}{\left(\textrm{stat}\right)}_{-0.04}^{+0.04}\left(\textrm{syst}\right) $$ , which is consistent with the Standard Model prediction of unity. This constitutes the most precise test of lepton flavour universality using $\textit{B}$ → $\textit{K}$ $\textit{ℓ}$ $\textit{ℓ}$ decays with dilepton invariant-mass-squared above the $\textit{ψ}$(2$\textit{S}$) mass, whilst being the first of its kind at a hadron collider.

Ukraine

Measurement of the branching fraction ratio $\textit{R}$

Big Bang nucleosynthes describes a significant process in the early universe, responsible for the formation of light nuclei a while after the Big Bang explosion. Its sensitivity to the expansion rate makes BBN an effective probe for testing deviations from standard cosmology, particularly within the framework of modified theories of gravity. In this article, we investigate the evolution of the Universe through Big Bang nucleosynthesis within the framework of <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> gravity. Here, <math altimg='si3.svg'><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub></math> and <math altimg='si4.svg'><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub></math> correspond to the torsion, boundary term, teleparallel Gauss-Bonnet term, and Gauss-Bonnet boundary term, respectively. To explore the deviation from the teleparallel equivalent of general relativity, we apply the transformation <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> = <math altimg='si5.svg'><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi mathvariant='script'>F</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math>. For an in-depth analysis of the Big Bang nucleosynthesis, we choose five distinct models from gravity and compared the results with the observational limits on <math altimg='si6.svg'><mo stretchy='true'>|</mo><mfrac><mrow><mi mathvariant='normal'>&#916;</mi><msub><mrow><mi mathvariant='script'>T</mi></mrow><mrow><mi>f</mi></mrow></msub></mrow><mrow><msub><mrow><mi mathvariant='script'>T</mi></mrow><mrow><mi>f</mi></mrow></msub></mrow></mfrac><mo stretchy='true'>|</mo></math> to examine restrictions on the free parameters associated with these models. Our outcomes indicate that <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> gravity can agree with the constraint of big bang nucleosynthesis, and hence build a valid view of the universe. Moreover, we take the limiting cases of the assumed theory, that is, <math altimg='si7.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mi>B</mi><mo stretchy='false'>)</mo></math> and <math altimg='si8.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo stretchy='false'>)</mo></math> theories, which also ensure consistency with BBN data.

Pakistan

Abdul Malik Sultan

Manahil Ali

Shamaila Rani

Azerbaijan

Nadeem Azhar

N. Myrzakulov

Uzbekistan

Sanjar Shaymatov

Constraining Big Bang nucleosynthesis in <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mi>B</mi><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> gravity