The European Physical Journal C最新文献

We propose a novel, data-driven method for determining total charm cross sections in proton–proton collisions by extrapolating measured fiducial cross sections without assuming any particular fragmentation model. The recently observed charm fragmentation non-universality at the LHC experimentally establishes strongly increased baryon production fractions and correspondingly decreased meson production fractions compared to electron–positron collisions, with a very significant (p_T) dependence. The novel method accounts for this non-universality and its (p_T)-dependence through a data-driven extrapolation function called ddFONLL. Applied to (D^0) production at 5 and 13 TeV, this approach yields total charm cross sections that fully incorporate the fragmentation non-universality and increase significantly compared to the previous measurements still based on fragmentation universality. The results are consistent with NNLO QCD predictions and enable direct comparisons free from fragmentation assumptions. We use this to evaluate the sensitivity of total cross-section measurements to parton distribution functions and the charm-quark mass. An outlook is given on the potential of further expanding the use of the ddFONLL method.

We address the equilibrium configurations and stability properties of anisotropic compact stars whose interior is described by a modified Chaplygin gas (MCG) equation of state in the framework of the regularized four-dimensional Einstein–Gauss–Bonnet (4DEGB) theory. Applying a quasi-local prescription for the pressure anisotropy, we derive the modified Tolman–Oppenheimer–Volkoff (TOV) equations and integrate them numerically over a large parameter space in the Gauss–Bonnet coupling (alpha ) and the degree of anisotropy (beta ). We provide mass–radius sequences, mass-compactness, energy density, and pressure profiles, and perform a full stability analysis based on the turning-point criterion, the radial adiabatic index (gamma _r), and the radial and transverse sound speeds (v_r^2) and (v_t^2). Our results show that positive (alpha ) and positive anisotropy ((beta > 0)) systematically increase the maximum mass and radius, enabling then configurations that exceed (2,M_odot ) while still obeying causality and the modified Buchdahl bound in 4DEGB gravity. A comparison with the latest astrophysical constraints (NICER, GW170817, GW190814, and massive-pulsar measurements) identifies regions of the ((alpha ,beta )) parameter space that are observationally allowable. In conclusion, anisotropic dark-energy stars in 4DEGB gravity provide viable, observationally testable ultra-compact alternatives to normal neutron stars and black holes, and also potentially open rich avenues for further multi-messenger searches for higher-curvature effects.

The detection of ultra-high-energy (UHE) neutrinos in the EeV range is the goal of current and future in-ice radio arrays at the South Pole and in Greenland. Here, we present a deep neural network that can reconstruct the main neutrino properties of interest from the raw waveforms recorded by the radio antennas: the neutrino direction, the energy of the particle shower induced by the neutrino interaction, and the event topology, thereby estimating the neutrino flavor. For the first time, we predict the full posterior PDF for the energy and direction reconstruction via neural posterior estimation utilizing conditional normalizing flows, enabling event-by-event uncertainty prediction. We improve over previous reconstruction algorithms and obtain a median resolution of 0.30 log(E) and 18 square degrees for a ‘shallow’ detector component and 0.08 log(E) and 28 square degrees for a ‘deep’ detector component for neutral current (NC) events at a shower energy of 1 EeV. This deep learning approach also allows us to reconstruct the more stochastic (nu _e) - charged current (CC) events. We quantify the impact of different antenna types and systematic uncertainties on the reconstruction and derive a goodness-of-fit score to test the compatibility of measured neutrino signals with the Monte Carlo simulations used to train the neural network.

The four principal energy conditions (ECs) in general relativity prohibit negative energies, repulsive gravity and superluminal energy flows. One must invoke exotic matter to violate any one of these, yet (varLambda )CDM does so quite prominently during inflation and in the epoch of dark energy dominance. In this paper, we carry out model selection between the standard model and the (R_{textrm{h}}=ct) universe using a combination of HII galaxy and cosmic chronometer measurements in the local Universe, and directly compare the results to the constraints imposed by the ECs. We find that the latter cosmology is not only strongly favored by these data, with a likelihood of (sim 92%) versus only (sim 8%) for the former, but that its optimized fit is fully compliant with all four ECs, while (varLambda )CDM’s best fit violates the so-called strong energy condition at (zlesssim 2).

We present a study of the impact of data from the upcoming Electron Ion Collider (EIC) on the determination of the strong coupling within the context of the global MSHT fitting framework. To achieve this, we generate EIC electron-proton scattering pseudodata according to both conservative and optimistic experimental uncertainty projections and perform a simultaneous fit to obtain the proton PDFs and the value of the strong coupling. In the conservative case the impact is found to be moderate, but non-negligible, while in the optimistic case it is observed to be rather significant. These results therefore underline the promising potential for the EIC in the determination of the strong coupling. We in addition explore the impact of any potential tensions between the EIC data and the rest of the data in the global fit by injecting explicit inconsistencies into the pseudodata generation. This can lead to a noticeable bias in the extracted value of the strong coupling, highlighting the importance of accounting for all sources of theoretical uncertainty in the fit as well as the relevance of an enlarged, conservative, error definition in the determination of the strong coupling.

We investigate the discovery potential of the (3~textrm{TeV}) Compact Linear Collider (CLIC) for a singlet vector-like bottom partner B decaying via (B rightarrow tW.) Focusing on the fully hadronic final state (Bbar{B} rightarrow tW,tW,) we reconstruct boosted top and W candidates using large-R Valencia jets, supplemented by a merging strategy for partially resolved decays. A systematic scan of the jet-radius parameter identifies (R=0.8) as the optimal choice, balancing boosted-jet containment with jet multiplicity. Using a cut-based analysis optimized for the ((2t+2W)) topology and an integrated luminosity of (5~textrm{ab}^{-1},) CLIC can achieve sensitivity to (m_B lesssim 1.5~textrm{TeV}.) These results highlight CLIC’s excellent capability to probe heavy vector-like quarks in high jet multiplicity environments, extending well beyond the reach of current hadron collider searches.

In addition to the gravitational-wave (GW) tensor modes of general relativity, more general metric theories of gravity allow up to four additional polarization states. Sensitivity curves for these additional GW polarizations are key quantities for assessing how well a detector can constrain such theories. In this work, we derive analytical expressions and high-accuracy approximate formulas for the sensitivity curves for the vector-x,  vector-y,  breathing, and longitudinal modes of the second-generation time-delay interferometry (TDI). Our analysis covers the TDI Michelson, ((alpha ,beta ,gamma ),) Monitor, Beacon, Relay, and Sagnac combinations, together with the orthogonal A, E, T channels constructed from them. The validity of analytical expressions is confirmed by Monte Carlo integration. We find that, in the high-frequency limit, the sensitivity curves for the tensor and breathing modes scale as (f^{2},) whereas those for the vector and longitudinal modes approach the explicit asymptotic forms (frac{c^{textrm{op}}f^{2}}{ln f}) and (frac{4c^{textrm{op}}}{pi ^{2} L^{2}} f,) respectively. In the low-frequency limit, for all GW modes, the sensitivity curves of the (zeta ) combination and of the T channel scale as (f^{-6},) whereas those of the other TDI combinations and of the A, E channels scale as (f^{-4}.) In this limit, the sensitivity curves for the tensor and vector modes coincide, and likewise for the breathing and longitudinal modes. For the breathing mode, the sensitivity curves of the ((alpha ,beta ,gamma )) and (zeta ) combinations and of the T channel exhibit singularities at frequencies (f = k/L) and do not exhibit a frequency range with nearly flat sensitivity. LISA and Taiji exhibit better sensitivity for (f lesssim 0.01) Hz due to their longer arm lengths, whereas TianQin performs better at (f gtrsim 0.1) Hz. We also highlight the advantage of utilizing the uncorrelated A, E, T channels to maximize the signal-to-noise ratio. These analytical formulas are useful for estimating the capability of future space-based GW detectors to constrain additional GW polarizations.

We calculate the leading order amplitude and probability for the elastic scattering of an elementary meson and a kink in the (phi ^4) double-well model. Classically, the kink is reflectionless, and so the leading contribution arises at one loop. At this order, the scattering amplitude exhibits a pole when the incoming meson energy is twice the shape mode energy, corresponding to the excitation of an unstable resonance with the twice excited shape mode. We expect that higher order corrections will give this resonance a width equal to the inverse of the known lifetime of this unstable excitation.

In this work, we explore the new agegraphic dark energy model within the framework of Loop Quantum Cosmology (LQC). A quantum gravitational perspective on the dark energy evolution is explored. A combination of cold dark matter and dark energy in the form of New Agegraphic dark energy is considered with LQC as the background gravity theory. Both the interacting and non-interacting scenarios between dark energy and matter are considered. Various cosmological parameters, like the equation of state parameter, deceleration parameter, and statefinder parameters, are studied. The squared speed of sound is investigated to get an idea about the stability of the system. An observational data analysis using recent cosmological data and the Markov chain Monte Carlo algorithm is performed to constrain the free parameter space of the model. Our findings imply that the interaction of loop quantum effects with agegraphic dark energy offers a nonsingular origin scenario and a theoretically sound and observationally compatible explanation of the universe’s late-time acceleration.

In this draft, we investigate constant redshift function Morris–Thorne-like traversable wormhole (WH) models which described as a relativistic static fluid distribution in Schwarzschild-type coordinates with a topological global monopole charge under the influence of D-dimensional Einstein gravity. In this scenario we consider three distinct shape functions, while matter sector is supported by anisotropic fluid configuration. We show some basic criteria for the viability of all three shape function models, the radial null energy condition is generally violated while tangential components are satisfied in the vicinity of the throat for appropriately chosen parameter values. We examine that the active gravitational mass becomes negative near the throat which indicates the existence of exotic matter (EM) and positive anisotropy parameter helps in maintaining the throat stability, while the adiabatic indices lie above the relativistic threshold supporting the stability of the WH configurations. We also employ the complexity factor as a diagnostic tool for anisotropy and density inhomogeneity which reveals that the WH geometries evolve toward minimal complexity at large radial distances. We analyze the influence of monopole parameter on the WH’s throat and curvature through 2D and 3D embedding diagrams, however, the total amount of EM is estimated by utilizing volume integral quantifier (VIQ) approach in our considered gravity theory.