A search is presented for the production of a single narrow-width vectorlike <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>′</mo></msup></math> quark that decays to a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>t</mi></mrow></math> quark and a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>W</mi></mrow></math> boson. This search targets a single-lepton final state, where a muon or electron originates either from the semileptonic decay of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>t</mi></mrow></math> quark or from the leptonic decay of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>W</mi></mrow></math> boson, with the other particle decaying hadronically. The (semi)leptonic portion of the event is reconstructed from an electron or muon, missing transverse momentum, and a small-radius jet identified as a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>b</mi></mrow></math> quark jet if the muon or electron originates from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>t</mi></mrow></math> quark. The hadronic portion of the event is reconstructed as a single large-radius jet. The originating particle of the large-radius jet is identified using a neural-network-based tagger, and the dominant background contributions are modeled from data using a neural autoregressive flow network. The data were collected from 2016 to 2018 by the CMS experiment at the LHC in proton-proton collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>, corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>138</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. This search is the most sensitive to date to the production of single narrow-width <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>′</mo></msup></math> quarks. It excludes electroweak-singlet <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>′</mo></msup></math> quarks with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Γ</mi><mo>/</mo><msub><mrow><mi>m</mi></mrow><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo>=</mo><mn>5</mn><mo>%</mo></mrow></math> for masses between 0.8 and 1.23 TeV. Limits are also placed on the production cross section of single <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>′</mo></msup></math> quarks produced in association with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>t</mi></mrow></math> quarks, and on the coupling factor of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>′</mo></msup></math> quark to electroweak bosons.

Albania

K. Tauqeer

Armenia

A. Gevorgyan

A. Hayrapetyan

V. Makarenko

A. Tumasyan

Austria

W. Adam

L. Benato

T. Bergauer

M. Dragicevic

S. Gundacker

A.K. Guven

P.S. Hussain

M. Jeitler

N. Krammer

A. Li

D. Liko

M. Matthewman

J. Schieck

R. Schöfbeck

M. Shooshtari

M. Sonawane

N. Van Den Bossche

W. Waltenberger

C.E. Wulz

Belgium

T. Janssen

D. Ocampo Henao

T. Van Laer

P. Van Mechelen

D. Ahmadi

J. Bierkens

N. Breugelmans

S. Dansana

A. De Moor

M. Delcourt

S. Duponcheel

C. Gupta

F. Heyen

Y. Hong

K. Kang

P. Kashko

S. Lowette

I. Makarenko

S. Nandakumar

S. Tavernier

M. Tytgat

G.P. Van Onsem

S. Van Putte

T. Wybouw

A. Beshr

B. Bilin

F. Caviglia Roman

B. Clerbaux

A.K. Das

I. De Bruyn

G. De Lentdecker

E. Ducarme

H. Evard

L. Favart

I. Kalaitzidou

A. Khalilzadeh

A. Malara

M.A. Shahzad

L. Thomas

M. Vanden Bemden

C. Vander Velde

P. Vanlaer

C. Yuan

F. Zhang

A. Cauwels

M. De Coen

D. Dobur

C. Giordano

G. Gokbulut

K. Kaspar

D. Kavtaradze

D. Marckx

A. Mehta

K. Skovpen

A.M. Tomaru

J. van der Linden

J. Vandenbroeck

H. Aarup Petersen

A. Benecke

A. Bethani

G. Bruno

A. Cappati

J. De Favereau De Jeneret

C. Delaere

F. Gameiro Casalinho

A. Giammanco

A.O. Guzel

M. Hussain

Z. Lawrence

V. Lemaitre

J. Lidrych

P. Malek

S. Turkcapar

Brazil

G. Alves

M. Barroso Ferreira Filho

E. Coelho

Search for single production of a vectorlike <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>′</mo></msup></math> quark decaying to a top quark and a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> boson in the single-lepton final state in proton-proton 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>

We show that operator growth in large-central-charge conformal field theories with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="script">W</mi><mn>3</mn></msub></math> symmetry can violate the universal operator growth hypothesis once the Liouvillian is enlarged to probe the higher-spin generators. For the generalized Liouvillian <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">L</mi><mo>=</mo><msub><mi>κ</mi><mn>1</mn></msub><mrow><mo stretchy="false">(</mo><msub><mi>L</mi><mn>1</mn></msub><mo>+</mo><msub><mi>L</mi><mrow><mo>−</mo><mn>1</mn></mrow></msub><mo stretchy="false">)</mo></mrow><mo>+</mo><msub><mi>κ</mi><mn>2</mn></msub><mrow><mo stretchy="false">(</mo><msub><mi>W</mi><mn>2</mn></msub><mo>+</mo><msub><mi>W</mi><mrow><mo>−</mo><mn>2</mn></mrow></msub><mo stretchy="false">)</mo></mrow></math>, we compute the Lanczos coefficients in the descendant module of a heavy primary and find several classes with faster-than-linear growth in the descendant level <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>, including maximally violating sectors with asymptotic behavior <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>N</mi></msub><mo>∼</mo><msup><mi>N</mi><mn>2</mn></msup></math>. This superlinear growth exceeds the conjectured bound and renders the Krylov complexity divergent. We further show that the same quadratic asymptotic growth already arises in the global <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>L</mi><mo stretchy="false">(</mo><mn>3</mn><mo>,</mo><mi mathvariant="double-struck">R</mi><mo stretchy="false">)</mo></math> subalgebra, indicating that the violation is rooted in the extended higher-rank symmetry itself. Our results demonstrate that extended <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">W</mi></math> symmetries can qualitatively modify operator growth and evade conventional bounds on information scrambling.

India

Dileep P. Jatkar

Sujoy Mahato

Sukrut Mondkar

Praveen Thalore

Violation of universal operator growth hypothesis in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="script">W</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></math> conformal field theories

We study the phase structure of a model containing two flavors of massless staggered fermions interacting through two independent four-fermion couplings, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>U</mi><mi>I</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>U</mi><mi>B</mi></msub></math>, formulated on a three-dimensional Euclidean space-time lattice. At <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>U</mi><mi>B</mi></msub><mo>=</mo><mn>0</mn></math>, this model is known to exhibit a direct second-order quantum phase transition between a massless fermion (MF) phase and a phase in which fermions acquire masses through the mechanism commonly referred to as symmetric mass generation (SMG). We demonstrate that introducing a small nonzero value of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>U</mi><mi>B</mi></msub></math> qualitatively alters this structure: the single exotic transition at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>U</mi><mi>B</mi></msub><mo>=</mo><mn>0</mn></math> splits into two distinct, conventional transitions, separated by an intermediate phase in which fermion masses arise through the standard mechanism of spontaneous symmetry breaking (SSB). The first of these is a Gross–Neveu transition separating the MF phase from the SSB-induced massive phase, while the second is a three-dimensional XY transition between the SSB phase and the SMG phase. Using the fermion bag Monte Carlo method, we verify that the critical exponents associated with both transitions are consistent with the literature, thereby yielding a quantitative characterization of the resulting phase structure of the model.

China

Sandip Maiti

United Kingdom

Debasish Banerjee

United States

Shailesh Chandrasekharan

Switzerland

Marina K. Marinkovic

Phase diagram of a lattice fermion model with symmetric mass generation

We introduce a novel method to compute structure constants from Q functions in the scalar sector of planar <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">N</mi><mo>=</mo><mn>4</mn></math> super Yang-Mills (SYM) and related theories. The method derives from operatorial as well as functional separation of variables, and the structure constants are expressed as determinants of matrices whose entries are integrals over products of Q functions. In this framework, each operator is twisted by an external angle, mirroring the cusped Maldacena-Wilson loop. The structure constants of local single-trace operators in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">N</mi><mo>=</mo><mn>4</mn></math> SYM are recovered in the untwisting limit, where we obtain a one-to-one correspondence between our key building blocks and those of the hexagon formalism. Retaining appropriate twists, our structure constants also perfectly match those of the orbifold points of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">N</mi><mo>=</mo><mn>4</mn></math> SYM. Our results thus far are valid at leading order in the weak-coupling expansion, but their formulation in terms of Q functions provides a natural starting point for including loop corrections. Many of the methods we develop in this work apply more generally to the computation of correlation functions in integrable models.

Germany

Till Bargheer

Carlos Bercini

France

Gabriel Lefundes

Paul Ryan

Structure constants from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Q</mi></math> systems and separation of variables

In this work, we studied the spectroscopic masses, decay constants, oscillation frequencies, and Isgur–Wise function parameters of $\textit{B}$, $$B_s$$ , and $$B_c$$ mesons within the framework of a non-relativistic potential model. The interaction is modelled using the Killingbeck potential, with calculations performed using two complementary approaches: the matrix Numerov method for solving the Schrödinger equation and the quantum mechanical variational method employing the Gaussian wave function. We determined the unknown parameters of the Killingbeck potential by fitting it to the Cornell potential using the ordinary least squares (OLS) method. These calibrated parameters are then used to compute the aforementioned physical observables. We obtained the masses of the heavy mesons with deviations of less than 0.5% from the highly precise experimental data. We also discussed the drawbacks and limitations of the non-relativistic model and highlighted its domain of applicability. At the end, we compare our results obtained from both methods with those from other theoretical frameworks, including QCD sum rules, lattice QCD, and alternative potential model studies.

Pritom Kumar Nath

Rishan Dev Choudhury

Jugal Lahkar

Spectroscopic and structural properties of $\textit{B}$, $$B_s$$ , and $$B_c$$ mesons within a non-relativistic potential model: a comparative analysis via matrix Numerov and variational methods

We study cosmological models in which the late time accelerated expansion is driven by a bulk viscous dark energy fluid, motivated by the possibility that dissipative processes in the cosmic medium can generate an effective negative pressure without requiring a cosmological constant. Restricting our analysis to the homogeneous background evolution, we consider both minimally and non-minimally coupled viscous scenarios and analyze them using Type Ia supernovae, DESI DR2 baryon acoustic oscillation measurements, and the $\textit{Planck}$ 2018 cosmic microwave background data. We show that bulk viscosity naturally gives rise to dynamical dark energy behavior and can provide an alternative description of the observed expansion history. Compared to $$\Lambda $$ CDM, we find the interacting non–minimal model produces a marginal preference over $$\Lambda $$ CDM using different evidence estimations. The results demonstrate that bulk-viscous dark energy remains an observationally viable phenomenological framework at the background level however some viscous parameters remain prior-sensitive.

Mexico

Shahnawaz Adil

Sonej Alam

Somasri Sen

J. Vazquez

Dissipative cosmology and the nature of dark energy: insights from bulk viscosity with DESI DR2 observations

We study the post-inflationary open-string Hagedorn phase in perturbatively moduli stabilized brane– antibrane inflation. In this class of models, the volume modulus is stabilized by perturbative corrections rather than by non-perturbative effects to the superpotential, thereby avoiding the standard brane–antibrane $$\eta $$ -problem. Since inflation ends through tachyon condensation and brane–antibrane annihilation, the endpoint is intrinsically stringy and need not be described immediately by an ordinary radiation bath. We analyze whether the energy released at annihilation can drive the visible sector into an open-string Hagedorn phase, and study the consequences for dark radiation. If the Standard Model (SM) branes lie in the same throat as where the annihilation occurs, we find that a modest fraction of the released energy deposited into surviving visible open strings is sufficient to enter the Hagedorn regime and can suppress the effective number of relativistic species $$\Delta N_\textrm{eff}$$ below current observational bounds. If the SM lies in a different throat, the result depends on inter-throat energy transfer: prompt or delayed transfer can still yield a visible Hagedorn phase. However, the mechanism is most efficient when the local string scale in the SM throat is lower than or comparable to that in the annihilation throat.

Dibya Chakraborty

Czechia

Bangladesh

Ahmed Kamal

Fire at the tip of the throat: Hagedorn phase after brane–antibrane inflation?

Many exact solutions of Einstein–Maxwell and Einstein–Maxwell-dilaton theory share a common structural pattern in which the metric functions are built from harmonic functions on a specified spatial base, often taken to be flat. We investigate this pattern by considering the Einstein–Maxwell-dilaton theory in arbitrary dimensions, where the dilaton field is non-trivially coupled to the Maxwell field and to a Liouville-type potential proportional to the cosmological parameter. Without imposing either the base geometry or the harmonic form of the metric function in advance, we show that for the generic branch, the field equations force the dilaton couplings to be equal, restrict the spatial base geometry to be Ricci flat, and make the metric function harmonic on this base. The resulting spacetime can then be written in terms of a conformal potential. We also consider a purely spatial branch, which instead leads to a distinct constraint on the coupling constants. These results provide a unified field-equation derivation of the harmonic behavior and conformal structure that appear in several classes of solutions, including multi-center geometries, cosmological solutions, and dynamical black holes.

Canada

Bardia Fahim

Joshua Fenwick

Consistency conditions and the derivation of harmonic structure in Einstein-Maxwell-dilaton theory

The mass spectrum of tetraquark states is examined using the spinless Salpeter equation alongside the Cornell potential. Analytical wave functions are derived through a variational approach, resulting in a specific mass formula for the bound states. This study investigates the mass spectra of heavy tetraquark states within a constituent diquark-antidiquark model. We employ a spinless Salpeter equation framework, incorporating the Cornell potential to describe the interaction between the diquark and antidiquark constituents. To account for relativistic effects, we utilize first-order perturbation theory to include the leading-order kinetic energy corrections arising from the expansion of the relativistic kinetic energy operator. A variational approach is adopted to determine the ground state masses, where the optimal variational parameter $${\beta }$$ is found by minimizing the system’s energy and then for higher states. We systematically calculate the masses of several experimentally observed and predicted tetraquark candidates, across a range of strong coupling constant values. Our results demonstrate a sensitivity of the calculated tetraquark masses, and the model provides theoretical mass predictions that are in reasonable agreement with experimental observations for these exotic hadronic states. This work contributes to a deeper understanding of the internal structure and dynamics of heavy tetraquarks.

Pranami Baishya

Bhaskar Hazarika

Mass spectra of tetraquark states from the spinless Salpeter equation

Bern-Carrasco-Johansson relations are helicity-independent constraints among the partial amplitudes of tree-level processes containing gluons and possibly also matter fields. They are a consequence of color-kinematic duality, but alternatively can be derived using the color-factor symmetry of tree-level amplitudes. We use recursive perturbiner methods to present a general, streamlined proof of the color-factor symmetry of all tree-level amplitudes containing an arbitrary number of fundamental spin-zero or spin-one-half matter fields and at least one gluon.

Abigail Chriss

Mia Karlsson

Stephen Naculich

Color-factor symmetry using perturbiner methods for tree-level amplitudes of Yang-Mills theory coupled to matter