High Energy Physics
Particle physics theory, phenomenology, and experiments
Particle physics theory, phenomenology, and experiments
A cat state localized in the right Rindler wedge is employed to study the violation of the Bell-CHSH inequality in a relativistic scalar free Quantum Field Theory. By means of the bounded Hermitian operator $sign(\varphi(f))$, where $\varphi(f)$ stands for the smeared scalar field, it turns out that the Bell-CHSH correlator can be evaluated in closed analytic form in terms of the imaginary error function. Being the superposition of two coherent states, cat states allow for the existence of interference terms which give rise to a violation of the Bell-CHSH inequality. As such, the present setup can be considered as an explicit realization of the results obtained by Summers-Werner.
We investigate the quantum geometry of the Seiberg-Witten curve for $\mathcal{N}=2$, $\mathrm{SU(2)}^n$ linear quiver gauge theories. By applying the Weyl quantization prescription to the algebraic curve, we derive the corresponding second-order differential equation and demonstrate that it is isomorphic to the Extended Heun Equation with $n+3$ regular singular points. The physical parameters of the gauge theory are linked to the canonical coefficients of the Heun equation via a polynomial representation of the Seiberg-Witten curve. This framework provides the necessary mathematical foundation to apply non-perturbative gauge-theoretic techniques, such as instanton counting, to spectral problems in gravitational physics, most notably for higher-dimensional black holes.
We investigate the viability of non-thermal leptogenesis in the gauged $U(1)_{B-L}$ extension of the Standard Model (BLSM) with an inverse seesaw (ISS) mechanism for neutrino mass generation. In this framework, right-handed neutrinos typically have $\mathcal{O}(1)$ Yukawa couplings, which induce strong washout effects and render conventional thermal leptogenesis ineffective. We demonstrate that a successful baryogenesis scenario can nevertheless be realized through non-thermal leptogenesis, where right-handed neutrinos are produced from the decay of the heavy $B\!-\!L$ Higgs boson $χ$. We explicitly analyze the interplay between the dilution factor $T_R/M_χ$ and the washout parameter characteristic of the ISS, highlighting the tension between suppressing washout effects and maintaining sufficient reheating. We show that a viable lepton asymmetry can be generated provided the scalar mass spectrum is appropriately tuned, allowing for a reduced reheating temperature while keeping washout under control. The resulting lepton asymmetry is efficiently converted into the observed baryon asymmetry of the Universe via sphaleron processes. Our results establish that the inverse-seesaw $B\!-\!L$ model remains a predictive and robust framework for non-thermal leptogenesis and baryogenesis.
In this contribution, we summarize our results on the complete NLO predictions for the production of off-shell top quark pairs in the $\ell+j$ channel at the LHC. All NLO QCD and electroweak corrections are consistently included across the full set of LO contributions and partonic subprocesses, while retaining finite-width effects of the top quarks and the electroweak gauge bosons. Resonant and non-resonant contributions as well as interference effects are included in the complete calculation. We pay special attention to infrared singularities associated with photons and jets appearing simultaneously in the final state. Fiducial integrated and differential cross-section results are presented for $pp$ collisions at $\sqrt{s}=13.6$ TeV.
2601.05055Light bosonic fields may suffer an instability around a rotating compact object. This process, known as superradiance, leads to the exponential amplification of the field around a black hole or neutron star, while the spin of the central object is correspondingly depleted. The discovery of a highly spinning black hole could therefore be used to constrain the existence of light bosons such as axions in a particular range of masses. These constraints apply for very low non-gravitational couplings between the boson and the Standard Model, offering a powerful search strategy for new physics. However, care must be taken to include the more complex effects of the black hole's astrophysical environment. Conversely, stellar superradiance could allow us to probe additional non-gravitational interactions between a new boson at the stellar matter. In this article, I will discuss the current status and future directions of axion superradiance. This is a contribution to the proceedings of the 3rd General Meeting of the COST Action COSMIC WISPers.
2601.05037The Taub-NUT and Eguchi-Hanson gravitational instantons, along with the self-dual Plebanski-Demianski metric, form a set of Euclidean metrics which can naturally be called `self-dual black holes', as they arise from self-dual slices of the most general vacuum, asymptotically flat black hole metric. These self-dual black holes are of interest for many reasons, and can famously be described through the non-linear graviton construction of twistor theory. However, the implicit nature of this twistor description obscures some features of the underlying geometry, particularly for the most general self-dual black holes. In this paper, we give a new construction of all asymptotically flat self-dual black holes based on holomorphic quadrics in flat dual twistor space, rather than the usual twistor space associated with self-duality. Remarkably, the geometry of the self-dual black holes -- including their hyperkahler structure, as well as Kerr-Schild and Gibbons-Hawking forms -- is directly encoded in the corresponding quadric. As a consequence, we obtain a previously unknown single Kerr-Schild form of the self-dual Plebanski-Demianski metric.
We study the entanglement negativity for the free, scalar chiral current in two spacetime dimensions, which is a simple model violating the Haag duality in regions with nontrivial topology. For the ground state of the system, both on the line and on the circle, we consider the setups given by two intervals, either adjacent or disjoint. We find analytic expressions for the moments of the partial transpose of the reduced density matrix and the logarithmic negativity. In the limit of small separation distance, this expression yields the same subleading topological contribution occurring in the mutual information. In the limit of large separation distance between the two intervals, the exponential decay of the logarithmic negativity is obtained from its analytic expression. The analytic formulas are checked against exact numerical results from a bosonic lattice model, finding a perfect agreement. We observe that, since the chiral current generates the neutral subalgebra of the full chiral Dirac fermion theory, this analysis highlights how symmetries produce nontrivial features in the entanglement structure that are analogue to those ones already observed in the mutual information for regions with nontrivial topology.
A model-independent parameterization of the low-energy scattering amplitude that incorporates the left-hand cut from one-particle exchange, an extension of the conventional effective-range expansion (ERE), was recently proposed and successfully applied to the low-energy $DD^*$ system [Phys. Rev. Lett. 135, 011903 (2025)]. While the original formulation is based on a nonrelativistic approximation and is thus limited to a [1,1] approximant for self-consistency, we extend the framework by explicitly including the higher-order terms up to $\mathcal{O}(k^6)$. We systematically investigate the reliability and robustness of the generalized ERE by incorporating relativistic kinematic effects. In addition, we develop a relativistic version of the ERE that accounts for lhc contributions. These results affirm the generalized ERE as a robust and systematically improvable framework for near-threshold scattering processes, providing both analytical and numerical reliability for applications in two-body scattering problems with a particle exchange.
We study the sensitivity of the upcoming electron-ion (EIC) collider to purely electrophilic new physics in the GeV mass range. Within an effective field theory framework, we consider two different scenarios: an axion-like particle (ALP) and a new heavy neutral vector gauge boson $Z^\prime $, each couples to electrons only. We analyze electron-proton collisions at $\sqrt{s}= 141$ GeV with an integrated luminosity of $100~{\rm fb}^{-1}$, focusing primarily on the tri-electron final state. Additionally, loop-induced ALP-photon couplings driven photon final states are also explored. Incorporating realistic detector effects and systematic uncertainties, we obtain projected exclusion limits on the relevant cross-sections and couplings. We find that the results from EIC can significantly extend the sensitivity to electrophilic axion-like particles and $Z^\prime $ bosons in regions of parameter space that remain weakly constrained by existing experiments.
We present an NLO QCD sum rules analysis of $J^{PC}=1^{-+}$ light four-quark states, investigated several compact tetraquark and four-quark molecule states, we obtain $1^{-+}$ light four-quark states masses,. Crucially, we have not find four-quark states with mass $\sim 1.4\,\text{GeV}$, which is the interpreted to be $π_1(1400)$ exotic state in previous leading-order studies. This result do not support the existence of $π_1(1400)$ state, agrees with the current experimental observation.
2601.04910We apply the conformal compensating technique for constructing matter couplings to conformal scalars on a $D$-dimensional foliated conformal Carroll manifold dividing the tangent space into $(p+1)$-dimensional longitudinal and $(D-p-1)$-dimensional transversal directions corresponding to $p$-branes. We show that the conformal Carroll algebra that was used for particle-like foliated geometries with $p=0$ cannot be used for higher-dimensional objects, called $p$-branes, with $0 < p \le D-2$. Furthermore, string-like foliated geometries are not suitable for the conformal compensating technique due to the conformal invariance in the longitudinal directions that is present for $p=1$. All other cases can be dealt with provided one uses a different conformal extension of the Carroll algebra that amounts to a conformal extension in the longitudinal directions only supplemented with an additional an-isotropic dilatation. By brane-duality similar results hold for foliated Galilean geometries which we present as well. Our results nicely fit in with recent work on foliated Aristotelian geometries.
We demonstrate that primordial magnetic fields (PMF) play a decisive role in the braneworld baryogenesis scenario of [Phys. Rev. D $\textbf{110}$, 023520 (2024)], where C/CP violation arises from the coupling of visible and hidden matter-antimatter sectors through a pseudo-scalar field. Although this mechanism generates baryon number efficiently only after the quark-hadron transition, by incorporating a realistic stochastic PMF within a semi-analytical framework, we find that matching the observed baryon-antibaryon asymmetry robustly requires PMF strengths of order $10^{10}$ T right after the transition, in agreement with causal QCD-era magnetogenesis. We further reveal that magnetic fluctuations drive the baryon-density spectrum to white noise on large scales, yielding an isocurvature component compatible with Cosmic Microwave Background (CMB) bounds. This establishes a predictive link between the braneworld baryogenesis model and realistic early-Universe magnetic fields.
We investigate the possibility of neutrinos interacting with a scalar dark matter field and the resulting implications for neutrino oscillations in the long-baseline sector. As our Universe is predominantly composed of dark matter, neutrinos propagating over astrophysical and terrestrial baselines inevitably traverse a dark matter background. The coherent forward scattering of neutrinos in such a background induces a medium-dependent correction to the mass-squared term in the effective neutrino Hamiltonian having opposing signs for neutrinos and antineutrinos. We study how the elements of this correction matrix, arising from coherent forward scattering of neutrinos with scalar dark matter background referred to as dark non-standard interactions (dark NSI), modify neutrino oscillation probabilities. Furthermore, we also study the effect of the off-diagonal elements and the associated phases on the measurement of leptonic CP violating phase focusing on the upcoming long-baseline superbeam experiments DUNE and T2HK. We show that dark NSI can lead to substantial enhancement or suppression of CP-violation sensitivity, depending on the true values of the dark NSI phases $φ_{αβ}$. We further explored how the synergy of DUNE and T2HK can effectively mitigate the degeneracies due to the dark NSI phases, and can restore or even enhance the CP sensitivity as compared to the standard oscillation scenario.
We provide the first lattice-QCD estimate of the crossover line down to $T\simeq108$~MeV. We introduce a new method that combines the Lee-Yang edge in the complex plane of baryon chemical potential $μ_B$ with universal chiral scaling to determine the $μ_B$ dependence of the QCD chiral critical and pseudo-critical temperatures. By performing $(2\!+\!1)$-flavor lattice QCD simulations at $T\simeq108$~MeV and purely imaginary $μ_B$ with a single lattice spacing and two volumes, we compute $μ_B$-dependent baryon-number susceptibilities and extract the location of the Lee-Yang edge. Together with universal scaling near the QCD chiral transition, it constrains the mapping function between $\{T,μ_B\}$ and the scaling variable (\textit{i.e.}\ the argument of the universal scaling functions). This mapping function then yields the $μ_B$ dependence of the critical and pseudo-critical temperatures for $T\gtrsim108$~MeV. While our calculation is performed only at a single value of low temperature without explicit input from small-$μ_B$ expansion, the resulting $μ_B$ dependence of the pseudo-critical temperature is consistent with established lattice-QCD determinations at small $μ_B$ and compatible with chemical freeze-out parameters of heavy-ion collisions down to low temperatures, demonstrating the validity and robustness of the method. Application of this method can be systematically extended to additional temperatures and finer discretizations, opening a pathway to charting the QCD phase diagram in the low-$T$, high-$μ_B$ regime.
2601.04718Motivated by recent claims questioning the existence of strong CP violation, we present a pedagogical review of CP violation in Quantum Chromodynamics (QCD). Using fundamental properties of the QCD partition function, we analyze the dependence of the chiral quark and CP violating gluon condensates on the theta parameter and the quark masses in the chiral limit. We show explicitly how CP violation arises, clarify the role of the axial U(1) anomaly and the ordering of the infinite-volume limit, and discuss the conditions under which CP symmetry may or may not be realized, including in the large-N framework. Our results reaffirm the presence of strong CP violation for physically relevant parameters and thus the theoretical basis of the strong CP problem and axion physics.
We investigate how the gravitational effects of a black hole manifest themselves as thermal behavior in the dual finite-temperature conformal field theory (CFT). In the holographic framework of AdS/CFT, we analyze a wave packet propagating into a black hole geometry in the bulk by computing three-point functions of a scalar primary operator in the boundary CFT. Our setup captures thermal signatures such as exponential damping of the expectation value, which are absent at zero-temperature. This provides a concrete and analytically tractable example of how black hole physics can be probed from the CFT side.
2601.04642We construct a four-dimensional conformal amplitude whose four-point structure matches the Virasoro-Shapiro form familiar from string theory. The construction uses only general principles of conformal field theory - radial quantization, scale invariance, and analyticity - and does not rely on worldsheet geometry or string degrees of freedom. The resulting object is a kinematical, first quantized amplitude defined by symmetry and consistency, providing a four-dimensional realization of stringlike analytic structure and a concrete target for amplitude bootstrap approaches.
2601.04624We construct the index saddle for the supersymmetric F1--P black ring. Our construction proceeds by taking a supersymmetric limit of a non-supersymmetric doubly spinning F1--P black ring. We express the resulting saddle as a three-center Bena--Warner solution. The black ring saddle possesses a finite-area event horizon, yet the two-derivative index vanishes. The solution is singular on certain subspaces of the horizon, where higher-derivative corrections are expected to become important. We argue that, once such corrections are taken into account, the solution can yield a finite result. In particular, we present a scaling analysis showing that the index agrees with the microscopic result, up to an overall numerical constant that cannot be fixed by the scaling argument alone. This analysis applies only within a restricted region of parameter space, whose full significance is not yet fully understood.
2601.04623We construct singly and doubly spinning non-supersymmetric F1--P black ring solutions in five-dimensional supergravity. These black rings have regular horizons and non-zero temperature. The singly spinning configuration lies in the duality orbit of the black ring constructed by Elvang, Emparan, and Figueras, while the doubly spinning configuration is a charged extension of the black ring constructed by Chen, Hong, and Teo. We analyze the physical properties of these solutions and the various limits they admit. In particular, the doubly spinning solution admits an extremal limit in which the entropy satisfies the relation S= 2 πJ_φ, thereby linking it directly to the angular momentum on the S^2.
We present a search for ultralight axion dark matter coupled to electron spins using a levitated ferromagnetic torsional oscillator (FMTO). This platform directly measures axion-induced torques on a macroscopic spin-polarized body, combining large spin density with strong mechanical isolation to probe magnetic fluctuations below 10 Hz while suppressing gradient-field noise. In a first implementation, the experiment yielded 18000 s of analyzable data at room temperature under high vacuum with optical readout and triple-layer magnetic shielding. A likelihood-based statistical framework, incorporating stochastic fluctuations in the axion-field amplitude, was used to evaluate the data. No excess consistent with an axion-induced pseudo-magnetic field was observed near 2e-14 eV. To account for possible shielding-induced signal attenuation, we quantify its effect and report both the uncorrected (g_aee < 1e-7) and attenuation-corrected (g_aee < 6e-5) 90% CL limits on the axion-electron coupling. Looking ahead, improvements guided by both noise-budget analysis and shielding-attenuation considerations, including optimized levitation geometry, cryogenic operation, and superconducting shielding, are expected to boost sensitivity by multiple orders of magnitude.