Journal of High Energy Physics最新文献

We propose to use the winding number of the gradient of a scalar potential as a simple topological index that relates critical points in the interior of the scalar field space to the behavior of the potential at the (asymptotic) boundary of the field space. We demonstrate this technique for supersymmetric flux compactifications of M-theory on Calabi-Yau four-folds, and use the Fermat sextic as a simple, one-parameter example.

The b → c semileptonic sum rules provide relations between the decay rates of (Bto {D}^{(*)}tau overline{nu }) and ({Lambda }_{b}to {Lambda }_{c}tau overline{nu }). Starting from the heavy quark and zero-recoil limits, we revisit the derivation of the sum rule for total decay rates. We then examine deviations from the limits and investigate corrections arising from realistic hadron masses and higher-order contributions to form factors, taking account of uncertainties. We show that these corrections are negligible compared to current experimental uncertainties, indicating that the sum rule is useful for cross-checking experimental consistency and testing the validity of the Standard Model predictions. In future, precise determinations of the form factors particularly for the tensor operator will be necessary to compare the sum rule predictions with ({Lambda }_{b}to {Lambda }_{c}tau overline{nu }) data from the LHCb experiment and the Tera-Z projects.

We consider properties of the gravitational path integral, ({mathcal{Z}}_{text{grav}}), of a four-dimensional gravitational effective field theory with Λ > 0 at the quantum level. To leading order, ({mathcal{Z}}_{text{grav}}) is dominated by a four-sphere saddle subject to small fluctuations. Beyond this, ({mathcal{Z}}_{text{grav}}) receives contributions from additional geometries that may include Einstein metrics of positive curvature. We discuss how a general positive curvature Einstein metric contributes to ({mathcal{Z}}_{text{grav}}) at one-loop level. Along the way, we discuss Einstein-Maxwell theory with Λ > 0, and identify an interesting class of closed non-Einstein gravitational instantons. We provide a detailed study for the specific case of ({mathbb{C}}{P}^{2}) which is distinguished as the saddle with second largest volume and positive definite tensor eigenspectrum. We present exact one-loop results for scalar particles, Maxwell theory, and Einstein gravity about the Fubini-Study metric on ({mathbb{C}}{P}^{2}).

We present integrated subtraction terms and finite remainders for arbitrary processes with massless partons at hadron and lepton colliders in the context of the nested soft-collinear subtraction scheme. These results provide the very last ingredients needed to make this scheme a fully local, analytic and process-independent framework for treating infrared singularities at next-to-next-to-leading order in perturbative QCD. The explicit infrared finiteness of all required contributions, as well as their process-independence, puts these results on par with subtraction schemes developed for next-to-leading order computations and opens up a clear path towards the automation of next-to-next-to-leading order computations in QCD.

The axion-like particle (ALP), a pseudo Nambu-Goldstone boson that couples to two photons, has been studied extensively in recent years as a dark matter candidate. For initial field configurations in a minimal ALP model explaining the observed dark matter abundance, we need the potential height to exceed the ALP energy density at redshift z ≈ 5.5 × 10⁶ leading to:({f}_{phi }gtrsim 4times {10}^{13}{text{GeV}}left(frac{{10}^{-18}{text{eV}}}{{m}_{phi }}right),)

where m_ϕ and f_ϕ denote the ALP mass and decay constant, respectively. This bound is known for the ALP dark matter dominated by the homogeneous zero-momentum mode, under the requirement that coherent oscillations begin early enough to satisfy the late-forming dark matter constraint. One loop hole to evade this limit may be to introduce a large amount of the non-relativistic modes of the ALP with non-vanishing momenta. Here we show that the same limit remains valid even if nonzero-momentum modes dominate. Interestingly, when nonrelativistic gradient and kinetic modes prevail, the ALP behaves relativistic radiation rather than matter, if it violates the limit. Moreover, if the typical momentum is sufficiently small, Baumkuchen-like domain walls form, which play an important role in understanding the transition.

When a pair of dark matter particles interacts via a long-range force mediated by a light particle, their nonrelativistic annihilation cross section can be significantly enhanced — a phenomenon known as the Sommerfeld enhancement. This enhancement exhibits resonant behavior if the long-range potential supports shallow bound states or narrow resonances, which can lead to violations of the partial-wave unitarity bound. We identify the origin of this pathological behavior as the emergence of secular terms in perturbative expansions associated with low-energy composite states of the long-range potential. To address this issue, we propose a renormalization group improvement of the perturbative series. The resulting improved amplitude provides a unitarity-consistent form of the Sommerfeld enhancement, with its poles acquiring an imaginary part that reflects the decay width of the annihilating bound states. We also briefly discuss the implications of our approach from the perspective of Wilsonian renormalization group, and comment on its potential application to higher-order annihilation processes such as bound-state formation.

We present a measurement of the time-dependent CP asymmetry in ({B}^{0}to {K}_{text{S}}^{0}{pi }^{+}{pi }^{-}gamma ) decays using a data set of 365 fb⁻¹ recorded by the Belle II experiment and the final data set of 711 fb⁻¹ recorded by the Belle experiment at the Υ(4S) resonance. The direct and mixing-induced time-dependent CP violation parameters C and S are determined along with two additional quantities, S⁺ and S⁻, defined in the two halves of the ({m}^{2}left({K}_{text{S}}^{0}{pi }^{+}right)-{m}^{2}left({K}_{text{S}}^{0}{pi }^{-}right)) plane. The measured values are C = −0.17 ± 0.09 ± 0.04, S = −0.29 ± 0.11 ± 0.05, S⁺ = −0.57 ± 0.23 ± 0.10 and S⁻ = 0.31 ± 0.24 ± 0.05, where the first uncertainty is statistical and the second systematic.

We investigate the solution-generating technique based on the Breitenlohner-Maison (BM) linear system, for asymptotically flat, stationary, bi-axisymmetric black hole solutions with various horizon topologies in 5D vacuum Einstein theory. We construct the monodromy matrix associated with the BM linear system, which provides a unified framework for describing three distinct asymptotically flat, vacuum black hole solutions with a single angular momentum in five dimensions, each with a different horizon topology: (i) the singly rotating Myers-Perry black hole, (ii) the Emparan-Reall black ring, and (iii) the Chen-Teo rotating black lens. Conversely, by solving the corresponding Riemann-Hilbert problem using the procedure developed by Katsimpouri et al., we demonstrate that factorization of the monodromy matrix exactly reproduces these vacuum solutions, thereby reconstructing the three geometries. These constitute the first explicit examples in which the factorization procedure has been carried out for black holes with non-spherical horizon topologies. In addition, we discuss how the asymptotic behavior of 5D vacuum solutions at spatial infinity is reflected in the asymptotic structure of the monodromy matrix in the spectral parameter space.

Many contributions to the decay rate of the inclusive radiative (overline{B}to {X }_{s}gamma ) transition have been calculated to NNLO in QCD during the past decades. However, there are still a few unknown contributions from multi-parton final states which are formally NLO. In the present work, we compute those four-body (bto sqoverline{q }gamma ) contributions at NLO in QCD which need to be supplemented by the five-body (bto sqoverline{q }ggamma ) bremsstrahlung. This calculation formally completes the purely perturbative contributions to (overline{B}to {X }_{s}gamma ) at NLO. Our results are obtained by applying modern techniques of integral reduction and evaluation of master integrals. In particular, the analytic integration over the four and five-particle phase space in the presence of a cut on the photon energy turns out to be technically involved. We give our results completely analytically in terms of multiple polylogarithms, including the dependence on the collinear logarithms which arise from the mass-regularisation of collinear divergences. The numerical impact of multi-parton corrections on the (overline{B}to {X }_{s}gamma ) decay rate turns out to be small, owing to a partial cancellation between LO and NLO contributions.

We extend the Standard Model (SM) by introducing a U(1)′ gauge boson and a real pseudo-scalar field, both odd under a ℤ₂ symmetry. The resulting low-energy spectrum consists of a stable vector as the dark matter candidate, and a pseudo-scalar mediator, which interacts with the SM via a Higgs portal coupling and a dimension-five portal connecting it to both the dark and visible photons. We explore the freeze-in of both particles at low reheating temperature, finding a rich yield evolution dynamics in the early Universe. This setup brings a consistent dark matter scenario in which the dark photon relic abundance is generated through freeze-in at low reheating temperatures. In addition to its cosmological viability, the model can be tested at the LHC: Higgs bosons can decay into dark photons and displaced visible photons via the long-lived mediator. These signatures allow us to constrain the Higgs portal coupling using recent searches for non-pointing photons and limits on invisible or undetected Higgs decays. We derive meaningful constraints on the dark matter parameter space, in particular excluding a thermalized mediator in the region compatible with the observed relic abundance.