We investigate the frame dependence of distribution functions within the framework of generalized chiral kinetic theory. Based on the derived transformation rules governing the choice of frame, we analytically obtain the global equilibrium solutions in the presence of vorticity and electromagnetic fields. Our results show that, under the assumption of varying electromagnetic fields, these equilibrium solutions can be uniquely determined.

China

Shu-Xiang Ma

Jian-Hua Gao

Frame dependence in generalized chiral kinetic theory * Supported in part by the National Natural Science Foundation of China (12575147, 12321005, 12175123)

The second data release of the Dark Energy Spectroscopic Instrument (DESI DR2) has sharpened the question of whether late-time geometrical observations prefer a departure from the minimal $$\Lambda \textrm{CDM}$$ distance–redshift relation. We examine a deliberately restricted alternative interpretation: whether the same late-time distance information can be absorbed by an effective redshift dependence of the photon propagation factor. We introduce the dimensionless ratio $$C(z)\equiv c(z)/c_0$$ and adopt the bounded one-parameter form $$C(z)=1+\epsilon z/(1+z)$$ , with $$\epsilon =0$$ corresponding to the constant-speed limit. The analysis uses only late-time data: DESI DR2 compressed $$\textrm{BAO}$$ measurements, 31 cosmic-chronometer $$H(z)$$ points, and Type Ia supernova Hubble diagrams from DES-Dovekie and Pantheon-plus. The sound horizon $$r_d$$ is sampled as an independent free parameter with the uniform prior $$r_d\in [120,180]\,\textrm{Mpc}$$ , while the supernova intercept is profiled analytically; no CMB-calibrated sound-horizon prior and no distance-ladder prior are imposed. For the main DES-Dovekie+DESI DR2+ $$H(z)$$ combination we obtain $$\epsilon =-0.096^{+0.125}_{-0.114}$$ . Replacing DES-Dovekie by Pantheon-plus gives $$\epsilon =-0.048^{+0.142}_{-0.122}$$ . The VSL extension improves the minimum $$\chi ^2$$ by only $$1.05$$ relative to flat $$\Lambda \textrm{CDM}$$ , and is penalized by both AIC and BIC. Allowing spatial curvature changes the geometrical degeneracy directions but still gives $$\epsilon $$ consistent with zero. These results show that DESI DR2-era late-time geometry provides a useful null test of cosmological light-speed constancy, but does not support a one-parameter late-time VSL explanation of the DESI geometrical preference.

Shangyun Wang

Shengjia Wang

Late-time varying-speed-of-light test of the DESI DR2 geometrical preference

In order to find reliable and efficient numerical approximation schemes, we suggest to identify the functional renormalization group flow equations of one-particle irreducible two-point functions as Hamilton-Jacobi(-Bellman)-type partial differential equations. Based on this reformulation and reinterpretation we adopt a numerical scheme for the solution of field-dependent flow equations as nonlinear partial differential equations. We demonstrate this novel approach by first applying it to a simple fermion-boson system in zero spacetime dimensions—which itself presents as an interesting playground for method development. Afterwards, we show how the gained insights can be transferred to more interesting problems: one is the bosonic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math>-symmetric model in three Euclidean dimensions within a truncation that involves the field-dependent effective potential and field-dependent wave function renormalization. The other example is the (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mo>+</mo><mn>1</mn></mrow></math>)-dimensional Gross-Neveu model within a truncation that involves a field-dependent potential and a field-dependent fermion mass/Yukawa coupling at nonzero temperature, chemical potential, and finite fermion number.

Germany

Adrian Koenigstein

Martin J. Steil

Stefan Floerchinger

Functional renormalization group flows as diffusive Hamilton-Jacobi-type equations

Axions that couple to nuclear spins via the axial current interaction can be both produced and detected using nuclear magnetic resonance (NMR) techniques. In this scheme, nuclei driven by a real oscillating magnetic field in one device act as an axion source, which can drive NMR in a nearby spin-polarized sample interrogated with a sensitive magnetometer. We study the prospects for detecting axions through this method and identify two key characteristics that result in compelling detection sensitivity. First, the gradient of the generated axion field can be substantial, set by the inverse distance from the source. Near the source, it reduces to the inverse of the source’s geometric size. Second, because the generated axion field is produced at a known frequency, the detection medium can be tuned precisely to this frequency, enabling long interrogation times. We show that the experimental sensitivity of a pair of centimeter-scale NMR devices operating over a 15-day integration time can already surpass existing astrophysical bounds on the axion-nucleon coupling. A similar sensitivity can be achieved with 10 centimeter-scale NMR devices with only 1 hour of integration time. These dual NMR configurations are capable of probing a wide range of axion masses, up to values comparable to the inverse distance between the source and the sensor.

United States

Jeff A. Dror

Qiushi Wei

Fengwei Yang

Axion production and detection using a dual NMR-type experiment

Studying heavy-flavor jets in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> collisions is important since it can test perturbative QCD calculations and be used as a reference for heavy-ion collisions. Jets in this analysis are reconstructed from charged particles using the anti-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>k</mi><mi mathvariant="normal">T</mi></msub></math> algorithm with a resolution parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi><mo>=</mo><mn>0.4</mn></math> at midrapidity <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>η</mi><mo stretchy="false">|</mo><mo>&lt;</mo><mn>0.5</mn></math>. Beauty jets are tagged using a machine learning model that uses a convolutional neural network trained on information extracted from the jet, tracks, and secondary vertices. Results show that this model is superior in b-jet-tagging compared to other traditional tagging methods.

Japan

Hadi Hassan

Finland

Neelkamal Mallick

D.J. Kim

Machine learning-based b-jet tagging in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>

This paper presents a fully corrected measurement of the energy-energy correlator (EEC) within jets in pp collisions. The EEC traces the energy flow as a highly energetic parton undergoes a QCD shower followed by the confinement of partons into hadrons, probing the correlation function of the energy flow inside jets. The EEC observable is measured as a function of the charged particle pair angular distance, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mi mathvariant="normal">L</mi></msub></math>, for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>20</mn><mo>&lt;</mo><msubsup><mrow><mi>p</mi></mrow><mrow><mi mathvariant="normal">T</mi></mrow><mrow><mi>ch</mi><mtext> </mtext><mi>jet</mi></mrow></msubsup><mo>&lt;</mo><mrow><mn>80</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>/</mo><mi>c</mi></mrow></mrow></math>. In the perturbative region (large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mi mathvariant="normal">L</mi></msub></math>), a good agreement between the data and a next-to-leading-log perturbative QCD calculation is observed. In the nonperturbative region (small <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mi mathvariant="normal">L</mi></msub></math>), the data exhibit a linear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mi mathvariant="normal">L</mi></msub></math> dependence. There is a transition region in between, characterized by a turnover in the EEC distribution, indicating where hadronization effects begin to dominate. The peak of this transition region is located at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2.43</mn><mo>±</mo><mn>0.14</mn><mtext> </mtext><mtext> </mtext><mrow><mi>GeV</mi><mo>/</mo><mi>c</mi></mrow><mo>/</mo><mo stretchy="false">⟨</mo><msubsup><mi>p</mi><mi mathvariant="normal">T</mi><mrow><mi>ch</mi><mtext> </mtext><mi>jet</mi></mrow></msubsup><mo stretchy="false">⟩</mo></math> for jets of various energies, indicating a common energy scale for the hadronization process. State-of-the-art Monte Carlo event generators are compared with the measurements, and can be used to constrain the parton shower and hadronization mechanisms.

France

S. Acharya

India

A. Agarwal

CERN

G. Aglieri Rinella

Italy

L. Aglietta

M. Agnello

N. Agrawal

Z. Ahammed

S. Ahmad

South Korea

S.U. Ahn

Slovakia

I. Ahuja

A. Akindinov

V. Akishina

M. Al-Turany

D. Aleksandrov

B. Alessandro

H.M. Alfanda

Mexico

R. Alfaro Molina

B. Ali

A. Alici

N. Alizadehvandchali

A. Alkin

Norway

J. Alme

G. Alocco

T. Alt

A.R. Altamura

I. Altsybeev

J.R. Alvarado

M.N. Anaam

Romania

C. Andrei

United Kingdom

N. Andreou

A. Andronic

E. Andronov

V. Anguelov

F. Antinori

P. Antonioli

N. Apadula

L. Aphecetche

H. Appelshäuser

C. Arata

S. Arcelli

R. Arnaldi

Brazil

J.G.M.C.A. Arneiro

I.C. Arsene

M. Arslandok

A. Augustinus

R. Averbeck

D. Averyanov

M.D. Azmi

H. Baba

A. Badalà

J. Bae

Y. Bae

Y.W. Baek

X. Bai

R. Bailhache

Y. Bailung

R. Bala

A. Balbino

A. Baldisseri

Poland

B. Balis

Z. Banoo

V. Barbasova

F. Barile

L. Barioglio

Greece

M. Barlou

B. Barman

Hungary

G.G. Barnaföldi

L.S. Barnby

E. Barreau

V. Barret

L. Barreto

C. Bartels

K. Barth

E. Bartsch

N. Bastid

Sweden

S. Basu

G. Batigne

D. Battistini

B. Batyunya

D. Bauri

Peru

J.L. Bazo Alba

Denmark

I.G. Bearden

C. Beattie

P. Becht

D. Behera

I. Belikov

A.D.C. Bell Hechavarria

F. Bellini

R. Bellwied

S. Belokurova

L.G.E. Beltran

Y.A.V. Beltran

G. Bencedi

A. Bensaoula

S. Beole

Y. Berdnikov

A. Berdnikova

L. Bergmann

M.G. Besoiu

L. Betev

Exposing the parton-hadron transition within jets with energy-energy correlators in pp collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>5.02</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>

This work sets out to compute the corrections to the Euler-Heisenberg effective action that arise from spacetime-dependent background anisotropies that violate Lorentz symmetry. To accomplish our task, we evaluate the functional determinant of the modified Dirac operator using the spectral regularization method. Within the framework of the Standard Model extension (SME), these Lorentz-violating parameters correspond to the coefficients <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mn>5</mn></msub><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mi>μ</mi></msub><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>μ</mi></msub><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></math>. The corrected effective action is attained up to the second-order in the background parameters. Our results indicate a violation of Furry’s theorem at second-order for specific C-odd combinations of these parameters, in agreement with previous analyses based on explicit Feynman diagram calculations in scenarios with Lorentz-symmetry violation. In the kinetic (bilinear) piece of the effective action, nondynamical axionlike terms emerge, resembling structures commonly encountered in condensed-matter systems, such as Weyl semimetals. We show how this procedure modifies the Maxwell equations, from which we present both the corresponding (non)conservation of the energy-momentum tensor and the wave equation. We also notice that the vacuum behaves as an inhomogeneous medium, and compute the local dispersion relation by working in the eikonal approximation. As a result of the spacetime-dependence of the background, there appear imaginary contributions in the dispersion relation and, consequently, the wave amplitudes may be amplified or attenuated, which expresses the energy-momentum exchange between the waves and the background.

Wagno Cesar e Silva

João Paulo S. Melo

José A. Helayël-Neto

Extending the Euler-Heisenberg action to include effects of local Lorentz-symmetry violating backgrounds

The first search for the lepton-flavor violating decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><mrow><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>∓</mo></mrow></msup></mrow></mrow></math> in proton-proton collisions is presented, using data collected by the LHCb experiment between 2011 and 2018, corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>9</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. No significant signal is observed and an upper limit on the branching fraction is set at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><mrow><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>∓</mo></mrow></msup></mrow></mrow><mo stretchy="false">)</mo><mo>&lt;</mo><mn>1.8</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>9</mn></mrow></msup></mrow></math> at the 90% confidence level, 2 orders of magnitude more restrictive than the most stringent upper limit to date. This is the first constraint on lepton-flavor violating <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mo stretchy="false">→</mo><mi>d</mi></math> quark transitions at the LHC and also sets the most stringent upper limits to date on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mo stretchy="false">→</mo><mrow><mi>d</mi><msup><mi>μ</mi><mo>±</mo></msup><msup><mi>e</mi><mo>∓</mo></msup></mrow></math> transitions. Limits on left-handed and scalar scenarios beyond the standard model are also reported.

Netherlands

R. Aaij

M. Abdelfatah

A.S.W. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

A.A. Adefisoye

Spain

B. Adeva

M. Adinolfi

P. Adlarson

C. Agapopoulou

C.A. Aidala

S. Akar

K. Akiba

P. Albicocco

J. Albrecht

R. Aleksiejunas

F. Alessio

P. Alvarez Cartelle

S. Amato

J.L. Amey

Y. Amhis

L. An

L. Anderlini

M. Andersson

P. Andreola

M. Andreotti

S. Andres Estrada

A. Anelli

D. Ao

F. Archilli

Z. Areg

M. Argenton

Costa Rica

S. Arguedas Cuendis

L. Arnone

M. Artuso

E. Aslanides

R. Ataíde Da Silva

M. Atzeni

B. Audurier

J.A. Authier

D. Bacher

I. Bachiller Perea

S. Bachmann

Search for the Lepton-Flavor Violating Decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>∓</mo></mrow></msup></mrow></math>