Journal of High Energy Physics最新文献

The Monte Carlo (MC) replica method quantifies parameter uncertainties in global fits of parton distribution functions (PDFs) and Standard Model Effective Field Theory (SMEFT) Wilson coefficients by fitting a model to many noise-perturbed copies of the data and taking the empirical distribution of the best-fit parameters as the uncertainty. The method reproduces the Bayesian posterior exactly only when the model is linear in its parameters, and departs from it in the nonlinear case. We derive the leading-order distribution the method produces and compare it with the Laplace approximation of the Bayesian posterior: the two differ by a single computable matrix, the residual-weighted Hessian of the model at the best fit, whose sign and magnitude set the over- or under-estimation of the parameter uncertainties. This closed-form expression quantifies when and by how much the MC method departs from Bayesian inference. We illustrate it on two single-parameter examples solvable in closed form and point to its evaluation in full PDF and SMEFT fits as a natural next step.

Thermal fluctuations are generally expected to destroy order and restore symmetries at sufficiently high temperatures. Recently, however, a family of scalar theories in 2 + 1 dimensions was shown to exhibit ℤ₂ symmetry breaking that persists to arbitrarily high temperatures using a variety of approaches, including the ϵ-expansion, the FRG, and large-N techniques. Although the similarities among these theories suggest that they belong to the same universality class, this connection has not been established explicitly. In this work, we fill this gap. Using large-N methods, we analytically study the biconical vector model in a range of spacetime dimensions, including 2 + 1, at leading and next-to-leading order in the 1/N expansion. We determine the RG flow, fixed-point structure, and the CFT data of the infrared theory, reproducing and extending previous results and thereby unifying the apparently distinct constructions within a common analytic framework. We derive the effective potential, establish its stable minima at zero and finite temperature, and demonstrate spontaneous ℤ₂ symmetry breaking at arbitrarily high temperatures for large finite N.

We calculate the “kinematic” corrections ( t/{P}_z^2 ) and ( {m}_N^2/{P}_z^2 ) to the short distance expansion of gauge-invariant nonlocal quark-antiquark operators sandwiched between nucleon states with different momenta. Here t is the momentum transfer, m_N is the nucleon mass and P_z is the momentum component in the direction of the quark-antiquark separation, which is assumed to be large. These matrix elements can be calculated in lattice QCD and, at leading twist, expressed in terms of moments of the generalized parton distributions (GPDs). Our results allow one to control one of principal uncertainties in such calculations and extend their region of applicability to larger momentum transfers, which is important in the quest to access the three-dimension image of the proton. The calculated corrections turn out to be significant for a realistic lattice QCD setup.

( Toverline{T} )-deformed CFTs are known to possess nonlocal Virasoro×Virasoro symmetries, whose currents depend on integration of the stress tensor. Unfortunately, these symmetries do not act in a tractable manner on the undeformed operators, which are defined by evolving local operators in the undeformed CFT on a constant-time slice using the deformed Hamiltonian. In this paper, we explicitly construct two distinct classes of operators: (i) dressed operators, which are primary with respect to the Virasoro×Virasoro symmetries, and (ii) physical operators, a new type of operator that depends on fundamental fields at specific points and is therefore local at the classical level. While dressed operators preserve the conformal symmetry structure, they are themselves nonlocal in the sense that they depend on integrated quantities. Physical operators, by contrast, depend only on local fields. Moreover, physical operators can be expressed in terms of dressed operators, and this relation can be promoted to a definition of such operators at the quantum level. This enables the use of Virasoro×Virasoro symmetries to systematically compute physical quantities such as correlation functions. We calculate the two-point correlation functions of these operators in momentum space and find that our results align with both string theory predictions and field theory calculations. Additionally, we explore the relationship between physical operators and alternative operator definitions proposed in the literature.

We study energy-energy correlators (EEC) in planar ( mathcal{N} ) = 4 super Yang-Mills theory at strong ’t Hooft coupling λ. We consider the EEC in states created by half-BPS operators of arbitrary dimension p, and determine the corresponding event-shape function up to order λ^−3/2 from the worldsheet representation of the AdS Virasoro-Shapiro amplitude with Kaluza-Klein external states. For p = 2 we compute the second curvature correction, which completes the EEC through order λ⁻²; the new contribution improves the agreement with recently derived non-perturbative bounds at intermediate coupling. We further develop a complementary method in which the strong-coupling expansion coefficients of the EEC are extracted directly from the Wilson coefficients of low-energy expansion of the AdS Virasoro-Shapiro amplitude, and find the two approaches in perfect agreement.

How do dark matter-nucleus interactions transition from the regimes of coherent scattering, where single phonons are produced, to that of individual nuclear recoils? Answering this question relies on understanding multiphonon excitations. Multiphonons are important for interpreting low-threshold direct detection experiments, yet are computationally prohibitive to compute. In this paper, we employ a 1D N -site crystal lattice model where dark matter scattering can be computed exactly. We show that the only difference between coherent and incoherent scattering is that conservation of crystal momentum is enforced in coherent scattering. The momentum conservation constraint becomes less important as more phonons are produced, yielding the transition to incoherent scattering. Using numerical calculations of the 1D structure factor, we also obtain quantitative validation of using an incoherent approximation to compute sub-GeV dark matter scattering in realistic 3D crystals.

Quark portal interactions qqqN with a light singlet fermion N make baryon number testable through missing transverse energy (MET). We find that present LHC data constrain scales up to 10 TeV (MET plus jet), 8 TeV (MET plus top) and 11 TeV (MET plus bjet). With increasing mass, or larger portal couplings, N becomes less long-lived, and gives clean displaced vertex signatures, which encourage dedicated searches. We also narrow down viable mesogenesis models with color triplet scalars to a mass range ~ y · 3 TeV (with charm) and ~ y · 5 TeV (charmless) couplings y to b and lighter quarks, a window that can be scrutinized by HL-LHC. Interactions also induce rare decays of type baryon (meson) to meson (baryon) plus invisible, which complement high-p_T searches and can prove baryon number violation. We explore charm decays Λ_c → (π, K) + invisible. Their branching ratios are subject to sizable hadronic uncertainties and require high luminosity flavor facilities such as a Tera-Z facility (FCC-ee, CEPC). Branching ratios of top quarks into one or two b-jets plus N can reach few×10⁻⁶.

The Mielke-Baekler geometries are three-dimensional reductive homogeneous spacetimes together with a choice of invariant connection which is compatible with a lorentzian metric. The spacetimes generalise Minkowski and (anti)de Sitter spacetimes in that the invariant metric connection can have torsion, a peculiarity of three dimensions. Using coadjoint orbits and the techniques of nonlinear realisations, we construct worldline actions for massive and massless spinning particles moving in these spacetimes. We pay particular attention to the so-called teleparallel branch, in which the curvature of the invariant connection vanishes. Apart from the trivial Minkowski case, this singles out anti-de Sitter spacetime, as the only of these lorentzian manifolds admitting an invariant Weitzenböck connection; that is, a flat connection with torsion. The introduction of a Wess-Zumino term describing spin has, as a main consequence, the appearance of dynamical sectors (denoted “regular” and “critical”), with a different number of physical degrees of freedom. In particular, in the massive case, we discuss the formulation of the dynamics in terms of either the Weitzenböck or the Levi-Civita connection, and the emergence of a Papapetrou-type forcing term in the critical sector. For the massless particle we study the Noether symmetries of the action, which, for the spinless case, include the conformal transformations. For nonzero spin, only the Killing subset survives as genuine Noether transformations in the regular sector, while in the critical sector any conformal Killing contribution can be set to zero by a gauge transformation.

Near-extremal black holes contain infrared-enhanced quantum fluctuations in their near-horizon near-AdS₂ throat, governed in part by Schwarzian modes. We study the effect of these fluctuations on the zero-frequency stress-tensor response of a near-extremal asymptotically AdS₄ Reissner-Nordström black brane whose transverse directions are regulated by a finite toroidal quotient. Working directly in four dimensions, we compute the leading correction in the weakly coupled Schwarzian regime T_q ≪ T ≪ r₀/L². At one loop, the shear perturbation couples to the n = 2 would-be zero mode and produces a correction proportional to T_q/T. Together with the logarithmic correction to the entropy, this yields a finite-volume correction to η/s. Our calculation provides a direct four-dimensional benchmark, complementary to exact two-dimensional treatments, while keeping the asymptotic AdS₄ source explicit.

We study four-dimensional conformal field theories (CFTs) with an abelian U(1) global symmetry using the conformal bootstrap approach. We obtain numerical bounds on the scaling dimensions of low-lying operators, the stress-tensor central charge, and a particular combination of the ’t Hooft anomaly and the current central charge. Our analysis provides the first non-perturbative constraints on four-dimensional CFTs with conserved abelian currents and establishes a framework that can be extended to theories with non-abelian global symmetries.