We investigate thermal photon production in the quark-gluon plasma (QGP) under strong magnetic fields using a magnetohydrodynamic (MHD) framework. We employ relativistic ideal fluid dynamics under the non-resistive approximation by adopting the Bjorken flow model with power-law decaying magnetic fields $ \mathbf{B}(\tau) = \mathbf{B}_0 (\tau_0/\tau)^a $ , span> $\textit{a}$ controls the decay rate, $ B_0 = \sqrt{\sigma} T_0^2 $ , and $\textit{σ}$ characterizes the initial field strength. The resulting QGP temperature evolution exhibits distinct $\textit{a}$- and $\textit{σ}$-dependent behaviors. Thermal photon production rates are calculated for three dominant processes: Compton scattering with $ q\bar{q} $ annihilation (C+A), bremsstrahlung (Brems), and $ q\bar{q} $ annihilation with additional scattering (A+S). These rates are integrated over the space-time volume to obtain the photon transverse momentum $ (p_T) $ spectrum. Our results demonstrate that increasing $\textit{a}$ enhances photon yields across all $ p_T $ , with $ a \to \infty $ (super-fast decay) providing an upper bound. For $ a = 2/3 $ , a larger $\textit{σ}$ suppresses yields through accelerated cooling, whereas for $ a \to \infty $ , a larger $\textit{σ}$ enhances yields via prolonged thermal emission. Low- $ p_T $ photons receive significant contributions from all QGP evolution stages, while high- $ p_T $ photons originate predominantly from early times. The central rapidity region $ (y=0) $ dominates the total yield. This work extends the photon yield studies to the MHD regime under strong magnetic fields, clarifying the magnetic field effects on QGP electromagnetic signatures and establishing foundations for future investigations of magnetization and dissipative phenomena.

China

Jie Xiong

Xiang Fan

Jing Jing

Weishan Yang

Duan She

Ze-Fang Jiang

Thermal photon emission from quark-gluon plasma: 1+1D magnetohydrodynamics results * Supported by the National Natural Science Foundation of China (NSFC) (12305138). Duan She's research is funded by the Startup Research Fund of Henan Academy of Sciences (231820058) and the 2024 Henan Province International Science and Technology Cooperation Projects (242102521068)

<p>In light of ongoing issues with the first-row unitarity test of the Cabibbo-Kobayashi-Maskawa matrix, we showcase a global fit to measurements of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mo stretchy="false">→</mo><mo>ℓ</mo><mi>ν</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mo stretchy="false">→</mo><mi>π</mi><mo>ℓ</mo><mi>ν</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi><mo stretchy="false">→</mo><mi>K</mi><mi>ν</mi></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi><mo stretchy="false">→</mo><mi>K</mi><mi>π</mi><mi>ν</mi></math> decays for the first time. Fitting the semileptonic and three-body <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> decay data simultaneously becomes computationally feasible because we employ a simple form factor parametrization for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mi>π</mi></math> form factor that manifestly connects the semileptonic and pair-production regions. We find good agreement with the data and use our analyses to infer <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>V</mi><mrow><mi>u</mi><mi>s</mi></mrow></msub><mo stretchy="false">|</mo></math> and the parameters for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mi>π</mi></math> form factors. Our result for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>V</mi><mrow><mi>u</mi><mi>s</mi></mrow></msub><mo stretchy="false">|</mo></math> sits close to the results extracted from exclusive <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mrow><mo>ℓ</mo><mn>2</mn></mrow></msub></math> and somewhat above the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mrow><mo>ℓ</mo><mn>3</mn></mrow></msub></math> decay and inclusive <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> decay result. Moreover, our results for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mo stretchy="false">→</mo><mi>π</mi></math> vector form factor at zero momentum transfer are compatible with lattice QCD determinations, despite not using lattice QCD inputs for this quantity in our fit of the hadronic matrix elements. We are further able to determine some of the pole parameters of the individual scalar and vector <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mi>π</mi></math> resonances with masses below the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> mass. We caution that our results account only for short-distance electromagnetic corrections but not long-distance contributions; this is due to the lack of a consistent description of long-distance corrections to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mi>π</mi></math> matrix elements both above and below threshold for an arbitrary model of the form factors.</p>

United Kingdom

Matthew Kirk

Danny van Dyk

Global determination of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">|</mo><msub><mrow><mi>V</mi></mrow><mrow><mi>u</mi><mi>s</mi></mrow></msub><mo stretchy="false">|</mo></mrow></math>

Within the framework of nonrelativistic quantum chromodynamics (NRQCD) factorization, we compute the $$ \mathcal{O}\left({v}^4\right) $$ relativistic corrections to the fragmentation of a heavy quark into the color-singlet $$ {}^1{S}_0^{\left[1\right]} $$ and $$ {}^3{S}_1^{\left[1\right]} $$ quarkonium states. Using the Collins-Soper definition of the fragmentation function, we reproduce the known $$ \mathcal{O}\left({v}^2\right) $$ results. We find that the $$ \mathcal{O}\left({v}^4\right) $$ correction gives a positive contribution relative to the leading order result over a wide range of the light-cone momentum fraction $\textit{z}$, while its magnitude remains much smaller than that of the $$ \mathcal{O}\left({v}^2\right) $$ correction. This behavior indicates a good convergence of the NRQCD relativistic expansion in this process. We further extend the calculation to the fragmentation functions in the unequal-mass case at $$ \mathcal{O}\left({v}^4\right) $$ and obtain the corresponding analytical expressions.

Sai Cui

Yi-Jie Li

Guang-Zhi Xu

Kui-Yong Liu

Order-$\textit{v}$ 4 corrections to heavy quark fragmentation to $\textit{S}$-wave heavy quarkonium

This paper presents a search for new physics through the process where a massive particle, X, decays into a Higgs boson and a second particle, Y. The Higgs boson subsequently decays into a bottom quark–antiquark pair, which is reconstructed as a single large-radius jet. The decay products of Yare also assumed to produce a single large-radius jet. The identification of the Yparticle is enhanced by computing the anomaly score of its candidate jet using an autoencoder, which measures deviations from typical quark- or gluon-induced jets. This allows a simultaneous search for multiple Ydecay scenarios within a single analysis. In the main benchmark process, Yis a scalar particle that decays into a Wboson pair. Two other scalar Ydecay processes are also considered as benchmarks: decays to a light quark–antiquark pair, and decays to a top quark–antiquark pair. A fourth benchmark process considers Yas a hadronically decaying top quark, arising from the decay of a vector-like quark into a top quark and a Higgs boson. Data recorded by the CMS experiment at a center-of-mass energy of 13 $$\,\text {Te}\hspace{-.08em}\text {V}$$ in 2016–2018, corresponding to an integrated luminosity of 138 $$\,\text {fb}^{-1}$$ , are analyzed. The search covers Xmasses between 1.4 and 3.0 $$\,\text {Te}\hspace{-.08em}\text {V}$$ and Ymasses between 90 and 400 $$\,\text {Ge}\hspace{-.08em}\text {V}$$ , with all simulated signals produced in the narrow-width approximation. No significant excess above the standard model background expectation is observed. The most stringent upper limits to date are placed on benchmark signal cross sections for various masses of X and Y particles

Armenia

A. Hayrapetyan

V. Makarenko

A. Tumasyan

Austria

W. Adam

J. Andrejkovic

L. Benato

T. Bergauer

M. Dragicevic

C. Giordano

P. Hussain

M. Jeitler

N. Krammer

A. Li

D. Liko

M. Matthewman

I. Mikulec

J. Schieck

R. Schöfbeck

D. Schwarz

M. Shooshtari

M. Sonawane

W. Waltenberger

C.E. Wulz

Belgium

T. Janssen

H. Kwon

D. Ocampo Henao

T. Laer

P. Mechelen

J. Bierkens

N. Breugelmans

J. D’Hondt

S. Dansana

A. Moor

M. Delcourt

F. Heyen

Y. Hong

P. Kashko

S. Lowette

I. Makarenko

D. Müller

J. Song

S. Tavernier

M. Tytgat

G. Onsem

S. Putte

D. Vannerom

B. Bilin

B. Clerbaux

A. Das

I. Bruyn

G. Lentdecker

H. Evard

L. Favart

P. Gianneios

A. Khalilzadeh

F. Khan

A. Malara

M. Shahzad

L. Thomas

M. Vanden Bemden

C. Vander Velde

P. Vanlaer

F. Zhang

M. Coen

D. Dobur

G. Gokbulut

J. Knolle

D. Marckx

K. Skovpen

N. Bossche

J. Linden

J. Vandenbroeck

L. Wezenbeek

S. Bein

A. Benecke

A. Bethani

G. Bruno

A. Cappati

J. Favereau De Jeneret

C. Delaere

A. Giammanco

A. Guzel

V. Lemaitre

J. Lidrych

P. Malek

P. Mastrapasqua

S. Turkcapar

Brazil

G. Alves

M. Barroso Ferreira Filho

E. Coelho

C. Hensel

T. Oliveira

C. Mora Herrera

P. Rebello Teles

M. Soeiro

E. Tonelli Manganote

A. Vilela Pereira

W. Aldá Júnior

H. Brandao Malbouisson

W. Carvalho

Search for resonances decaying to an anomalous jet and a Higgs boson in proton–proton collisions at $$\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} $$

<p>A sample of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>365</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></mrow><mo stretchy="false">→</mo><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>4</mn><mi>S</mi><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mrow><mi>B</mi><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover></mrow></math> data collected by the Belle II experiment is used to measure the partial branching fractions of charmless semileptonic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi></math> meson decays and determine the magnitude of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>V</mi><mrow><mi>u</mi><mi>b</mi></mrow></msub></math>. Events containing a signal electron or muon <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>ℓ</mo></math> and a fully reconstructed hadronic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi></math> decay that constrains the signal kinematics are selected, while the rest of the event defines the hadronic system <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>X</mi><mi>u</mi></msub></math> associated with the signal. To discriminate the signal from the 50-times larger background originating from CKM-favored semileptonic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi></math> decays, a template fit is performed in both signal and control regions after applying an optimized selection. The partial branching fraction measured for lepton energies greater than 1 GeV in the signal <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi></math> meson rest frame is <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Δ</mi><mi mathvariant="script">B</mi></mrow><mo stretchy="false">(</mo><mrow><mi>B</mi><mo stretchy="false">→</mo><msub><mi>X</mi><mi>u</mi></msub><mo>ℓ</mo><mi>ν</mi></mrow><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>1.54</mn><mo>±</mo><mn>0.08</mn><mrow><mo stretchy="false">(</mo><mi>stat</mi><mo stretchy="false">)</mo></mrow><mo>±</mo><mn>0.12</mn><mrow><mo stretchy="false">(</mo><mi>syst</mi><mo stretchy="false">)</mo></mrow><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math>. From this measurement, using the Gambino, Giordano, Ossola, Uraltsev theoretical framework, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>V</mi><mrow><mi>u</mi><mi>b</mi></mrow></msub><mo stretchy="false">|</mo><mo>=</mo><mo stretchy="false">(</mo><mn>4.01</mn><mo>±</mo><mn>0.1</mn><msubsup><mn>9</mn><mrow><mo>−</mo><mn>0.08</mn></mrow><mrow><mo>+</mo><mn>0.07</mn></mrow></msubsup><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math> is determined, where the uncertainties are experimental and theoretical, respectively. This value is consistent with the world average obtained from previous inclusive measurements. Different theoretical predictions and partial branching fractions measured in other phase-space regions, defined by additional selections on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>X</mi><mi>u</mi></msub></math> and leptonic system masses, are also used to determine <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>V</mi><mrow><mi>u</mi><mi>b</mi></mrow></msub><mo stretchy="false">|</mo></math>. This allows for a comparison of the resulting values across theoretical frameworks and phase-space regions.</p>

M. Abumusabh

I. Adachi

K. Adamczyk

L. Aggarwal

H. Ahmed

Y. Ahn

H. Aihara

N. Akopov

S. Alghamdi

M. Alhakami

A. Aloisio

N. Althubiti

K. Amos

N. Anh Ky

C. Antonioli

D.M. Asner

H. Atmacan

T. Aushev

R. Ayad

V. Babu

H. Bae

N.K. Baghel

S. Bahinipati

P. Bambade

Sw. Banerjee

M. Barrett

M. Bartl

J. Baudot

A. Beaubien

F. Becherer

J. Becker

J.V. Bennett

F.U. Bernlochner

V. Bertacchi

M. Bertemes

E. Bertholet

M. Bessner

S. Bettarini

V. Bhardwaj

B. Bhuyan

F. Bianchi

T. Bilka

D. Biswas

A. Bobrov

D. Bodrov

G. Bonvicini

J. Borah

A. Boschetti

A. Bozek

M. Bračko

P. Branchini

R.A. Briere

T.E. Browder

A. Budano

S. Bussino

Q. Campagna

M. Campajola

L. Cao

G. Casarosa

C. Cecchi

P. Chang

P. Cheema

L. Chen

B.G. Cheon

C. Cheshta

H. Chetri

K. Chilikin

J. Chin

K. Chirapatpimol

H.E. Cho

K. Cho

S.J. Cho

S.K. Choi

S. Choudhury

Measurement of inclusive <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo stretchy="false">→</mo><msub><mi>X</mi><mi>u</mi></msub><mo>ℓ</mo><mi>ν</mi></math> partial branching fractions and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>V</mi><mrow><mi>u</mi><mi>b</mi></mrow></msub><mo stretchy="false">|</mo></math> at Belle II