It is demonstrated within the dibaryon-induced model for $NN$ interaction that $pp$ scattering in $P$ waves is governed mainly by the production of the intermediate dibaryon resonances. Two dibaryon resonances with a mass of about 2200 MeV discovered recently by the ANKE-COSY Collaboration are shown to determine both elastic $pp$ phase shifts and inelasticities in the ${{}^{3}P}_0$ and ${{}^{3}P}_2$–${{}^{3}F}_2$ channels from zero energy up to $T_p=0.7–0.9\mathrm{GeV}$. It is also demonstrated clearly that the ${{}^{3}P}_0$ dibaryon plays a decisive role in near-threshold neutral pion production in $pp$ collisions which is poorly understood to date. The missing dibaryon contribution is found to be the very possible reason for the failure of traditional approaches to explain near-threshold ${\pi }^0$ production.

We calculate cross sections for production of axial-vector $f_1(1285)$ mesons for double-tagged measurements of the $e^{+}{e}^{-}\to e^{+}{e}^{-}{f}_1(1285)$ reaction. Different ${\gamma }^{*}{\gamma }^{*}\to f_1(1285)$ vertices from the literature are used. Both integrated cross section as well as differential distributions are calculated. Predictions for a potential measurement at Belle II are presented. Quite different results are obtained for the different vertices proposed in the literature. Several observables are discussed. The distribution in photon virtuality asymmetry is especially sensitive to the ${\gamma }^{*}{\gamma }^{*}\to f_1$ vertex. Future measurements at $e^{+}{e}^{-}$ colliders could test and/or constrain the ${\gamma }^{*}{\gamma }^{*}\to f_1(a_1,f_1^{\prime })$ vertices and associated form factors, known to be important ingredients for calculating contributions to anomalous magnetic moment of muon and hyperfine splitting of levels of muonic atoms. In addition we present helicity amplitudes as a function of both photon virtualities. Only some amplitudes are different from zero. Different models have different relative size of LT, TL, and TT amplitudes.

We compare the primordial scalar power spectra in the loop cosmological models using the effective dynamics of the hybrid approach to cosmological perturbations in which the background is loop quantized, but the perturbations are Fock quantized. The three loop cosmological models under consideration are the standard loop quantum cosmology (LQC), the modified LQC-I (mLQC-I) and the modified LQC-II (mLQC-II) in the spatially flat Friedmann-Lemaître-Robertson-Walker universe with a Starobinsky potential. These models arise from different regularizations of the classical Hamiltonian constraint in the symmetry reduced spacetimes and aim to capture certain features of quantization in loop quantum gravity. When applying the techniques in the hybrid approach to mLQC-I/II, we find the effective Mukhanov-Sasaki equations take the same form as in LQC. The difference among the three models is encoded in the unique expressions of the effective masses in each model. We find that the relative difference in the amplitude of power spectrum between LQC and mLQC-II is approximately 50% in the infrared and the oscillatory regimes, whereas this difference can be as large as 100% between mLQC-I and LQC/mLQC-II. Interestingly, in the infrared and the oscillatory regimes of mLQC-I, we obtain a suppressed power spectrum from the hybrid approach which is far below the Planck scale. This result is in a striking contrast to the one obtained from the dressed metric approach to perturbations where the corresponding amplitude in this regime is extremely large. Our analysis shows that while the phenomenological predictions are in agreement between the two approaches for LQC and mLQC-II, for mLQC-I the differences between the dressed and hybrid approaches can be quite significant. Our result provides the first robust evidence of difference in predictions between the dressed and hybrid approaches due to respective underlying constructions.

A geometric approach to understanding recursion relations for scattering amplitudes is developed. We achieve this by studying intersection numbers of triangulated accordiohedra presented as hyperplane arrangements. The cancellation of spurious divergences is subsequently realized as a topological no-boundary condition.

We derive the multipole moments of the Kerr-Newman-Unti-Tamburino (NUT) black hole spacetime using the Geroch-Hansen formalism, even though the spacetime is not asymptotically flat. Intriguingly, in the presence of the NUT charge, the absence of reflection symmetry about the equatorial plane leads to mass and spin multipole moments of all orders, in stark contrast to Kerr-like spacetimes. This leads to a drastic departure of the multipolar structure of a compact object with NUT charge, whose implications for gravitational wave observations have been explored. Our analysis of multipole moments for the Kerr-NUT spacetime is also in tune with the Thorne’s approach.

We derive a Higgs inflationary model in the context of holographic cosmology, where we consider a universe filled with a Higgs field nonminimally coupled to gravity in a slow-roll regime. The amplitude of density (scalar) perturbations is calculated. In this regard, we show that the background and perturbative parameters characterizing the inflationary era are related to the standard one through corrections terms. We found that for the $e$-fold number $N\sim 58$, the spectral index, $n_r$, and the tensor-to-scalar ratio, $r$, values are 0.965 and 0.021, respectively, which are in agreement with 2018 Planck observational data. However, as soon as we move from $N\sim 58$, the model is ruled out by the current data.

The no-boundary proposal is a theory of the initial conditions of the universe formulated in semiclassical gravity and relies on the existence of regular (complex) solutions of the equations of motion. We show by explicit computation that regular no-boundary solutions are modified, but not destroyed, upon inclusion of expected quantum gravity corrections that involve higher powers of the Riemann tensor as well as covariant derivatives thereof. We illustrate our results with examples drawn from string theory. Our findings provide a crucial self-consistency test of the no-boundary framework.

We present a simple approximation that can speed up the computation of the mode-coupling matrices, which are usually the bottleneck for computing unbiased angular power spectra, as well as their associated covariance matrices, of the cosmic microwave background temperature and polarization anisotropies. The approximation results in the speed-up of the MASTER algorithm by more than an order of magnitude with very little loss of precision. We demonstrate the performance on simulations of forthcoming cosmic microwave background surveys such as the Simons Observatory and CMB-S4 for a wide variety of survey window functions.

In this paper, we study the adiabatic matter creation process in holographic dark energy (HDE) with the motivation of considering it as an alternative choice to explain the recent accelerating phase of the Universe. In the background, we consider a homogeneous and isotropic flat Friedmann-Robertson-Walker geometry. It has been observed that the HDE with Hubble horizon as an IR cutoff does not show an accelerating Universe. Instead of assuming other IR cutoffs in order to have a transition at low redshifts, we consider the HDE model with the gravitationally induced matter creation processes. The matter creation rate is phenomenologically parametrized by a linear combination in terms of Hubble parameter, that is, $\mathrm{\Gamma }=3\alpha H_0+3\beta H$, where $\alpha$ and $\beta$ are positive constants. Some particular cases like HDE with $\mathrm{\Gamma }=0$ and $\mathrm{\Gamma }\propto H$ are also studied. The evolution of such models are tested by the latest observational data of a type Ia supernova, observational Hubble data, and latest local $H_0$ by SH0ES. We discuss the evolution of the Universe by plotting the trajectory of cosmological parameters using best-fit values. We find that the HDE model $\mathrm{\Gamma }=3\alpha H_0+3\beta H$ corresponds to early deceleration and then a smooth transition into an accelerated epoch. We discuss the cosmographic parameters and $Om$ to distinguish models with other standard dark energy models. By using the Akaike information criterion and the Bayesian information criterion, we also assess the viability of models corresponding to the $\mathrm{\Lambda }\mathrm{CDM}$ model. Finally, we discuss the thermodynamics of HDE model with matter creation and find that the model satisfies the generalized second law of thermodynamic under certain conditions.

Even though neutrino oscillations have been conclusively established, there are a few unanswered questions pertaining to leptonic charge parity violation, mass hierarchy, and ${\theta }_{23}$ octant degeneracy. Addressing these questions is of paramount importance at the current and future neutrino experiments including the Deep Underground Neutrino Experiment, which has a baseline of 1300 km. In the standard mode, DUNE is expected to run with a low energy tuned beam which peaks around the first oscillation maximum (2–3 GeV) (and then sharply falls off as we go to higher energies). However, the wide band nature of the beam available at long baseline neutrino facility allows for the flexibility in utilizing beam tunes that are well suited at higher energies as well. In this work, we utilize a beam that provides high statistics at higher energies which is referred to as the medium energy beam. This opens up the possibility of exploring not only the usual oscillation channels but also the ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillation channel which was otherwise not accessible. Our goal is to find an optimal combination of beam tune and runtime (with the total runtime held fixed) distributed in neutrino and antineutrino mode that leads to an improvement in the sensitivities of these parameters at the Deep Underground Neutrino Experiment. In our analysis, we incorporate all the three channels (${\nu }_{\mu }\to {\nu }_e,{\nu }_{\mu }\to {\nu }_{\mu },{\nu }_{\mu }\to {\nu }_{\tau }$) and develop an understanding of their relative contributions in sensitivities at the level of $\mathrm{\Delta }{\chi }^2$. Finally, we obtain the preferred combination of runtime using both the beam tunes as well as neutrino and antineutrino mode that lead to enhanced sensitivity to the current unknowns in neutrino oscillation physics, i.e., charge parity violation, mass hierarchy, and ${\theta }_{23}$ octant.

We study cosmic-ray-atmosphere collisions as a permanent production source of exotic millicharged particles (MCPs) for all terrestrial experiments. [MCPs are also known as charged massive particles (CHAMPs).] Based on data from Super-K, this allows us to derive new limits on MCPs that are competitive with, or improve, the currently leading bounds from accelerator-based searches for masses up to 1.5 GeV. In models where a subdominant component of dark matter (DM) is fractionally charged, these constraints probe parts of the parameter space that is inaccessible for conventional direct-detection DM experiments, independently of assumptions about the DM abundance.

We present a systematic numerical study of $\theta$ dependence around $\theta =0$ in the small-$N$ limit of $2d$ $C{P}^{N-1}$ models, aimed at clarifying the possible presence of a divergent topological susceptibility in the continuum limit. We follow a twofold strategy, based on one side on direct simulations for $N=2$ and $N=3$ on lattices with correlation lengths up to $O({10}^2)$ and, on the other side, on the small-$N$ extrapolation of results obtained for $N$ up to 9. Based on that, we provide conclusive evidence for a finite topological susceptibility at $N=3$, with a continuum estimate ${\xi }^2\chi =0.110(5)$. On the other hand, results obtained for $N=2$ are still inconclusive: They are consistent with a logarithmically divergent continuum extrapolation but do not yet exclude a finite continuum value, ${\xi }^2\chi \sim 0.4$, with the divergence taking place for $N$ slightly below 2 in this case. Finally, results obtained for the nonquadratic part of $\theta$ dependence, in particular, for the so-called $b_2$ coefficient, are consistent with a $\theta$ dependence, matching that of the dilute instanton gas approximation at the point where ${\xi }^2\chi$ diverges.

In the present work, we investigate the dipion transitions between $\mathrm{\Upsilon }(5S)$ and ${\mathrm{\Upsilon }}_J(1D)$ with $J=1$, 2, 3. Our analysis indicates that the dominant sources of the anomalously large widths of $\mathrm{\Upsilon }(5S)\to {\mathrm{\Upsilon }}_J(1D){\pi }^{+}{\pi }^{-}$ should be $Z_b^{(\prime )}$, i.e., the dipion transitions occur via the cascade decays $\mathrm{\Upsilon }(5S)\to Z_b^{(\prime )\pm }{\pi }^{\mp }\to {\mathrm{\Upsilon }}_J(1D){\pi }^{+}{\pi }^{-}$. With the assumption that all the short ranged dynamics could be absorbed in a single cutoff with a model parameter $\alpha$, the present estimations indicate that in a reasonable parameter range the measured branching ratios of $\mathrm{\Upsilon }(5S)\to {\mathrm{\Upsilon }}_J(1D){\pi }^{+}{\pi }^{-}$ can be reproduced in magnitude, which further proves that the decays via $Z_b^{(\prime )}$ dominate the dipion transitions of $\mathrm{\Upsilon }(5S)$ to ${\mathrm{\Upsilon }}_J(1D)$. Moreover, we also predict the ratios of the branching fractions of $Z_b^{(\prime )}\to {\mathrm{\Upsilon }}_J(1D)\pi$, which in our calculations are largely independent of the parameter $\alpha$ and could be tested by further experiments in Belle II.

We introduce a new jet observable zest defined on exclusively constructed jets and study its potential to discriminate jets originated from Standard Model heavy particles like $W$, $Z$ bosons and top quark from gluon initiated jets. Zest exhibits properties such as boost invariance, stability against global color exchange among partons, and inclusion or exclusion of a few soft particles in the jet. We also observe that for gluon jets, zest distribution is mostly insensitive to the jet mass. These properties make zest a suitable candidate for vetoing gluon jets at the colliders. Zest, when used in conjunction with other substructure observables that are uncorrelated to it, can further improve gluon jet veto. We generalize zest and show that in one limit it is synonymous to particle multiplicity and in the other limit, it projects only the leading particle. Optimization on the parameter of generalized zest further improves the discrimination ability of the observable. We find that for the top quark-initiated jets, the discrimination provided by generalized zest is in close comparison with a class of machine learning-based top taggers. We propose that studying other nonlinear infrared and collinear unsafe observables may help in unveiling the hidden physics of machine learning-based observables.

We determine the sensitivities of short-baseline coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) experiments using a pion decay at rest neutrino source as a probe for nonunitarity in the lepton sector, as expected in low-scale type-I seesaw schemes. We also identify the best configuration for probing light sterile neutrinos at future ton-scale liquid argon $\mathrm{CE}\nu \mathrm{NS}$ experiments, estimating the projected sensitivities on the sterile neutrino parameters. Possible experimental setups at the Spallation Neutron Source, Lujan facility and the European Spallation Source are discussed. Provided that systematic uncertainties remain under control, we find that $\mathrm{CE}\nu \mathrm{NS}$ experiments will be competitive with oscillation measurements in the long run.

Even though the Standard Model has achieved great success, its application to the field of low energy still lacks solid foundation due to our limited knowledge on nonperturbative QCD. Practically, all theoretical calculations of the hadronic transition matrix elements are based on various phenomenological models. There indeed exist some anomalies in the field that are waiting for interpretations. The goal of this work is trying to solve one of the anomalies: the discrepancy between the theoretical prediction on the sign of the up-down asymmetry parameter of ${\mathrm{\Lambda }}_c\to \mathrm{\Sigma }\pi$ and the experimental measurement. In the literatures several authors calculated the rate and determined the asymmetry parameter within various schemes, but there exist obvious loopholes in those adopted scenarios. To solve the discrepancy between theory and data, we suggest that not only the direct transition process contributes to the observed ${\mathrm{\Lambda }}_c\to \mathrm{\Sigma }\pi$, but also other portals such as ${\mathrm{\Lambda }}_c\to \mathrm{\Lambda }\rho$ play a substantial role via an isospin-conserving rescattering $\mathrm{\Lambda }\rho \to \mathrm{\Sigma }\pi$. Taking into account the effects induced by the final state interaction, we reevaluate the relevant quantities. Our theoretical prediction based on this scenario involving an interference between the direct transition of ${\mathrm{\Lambda }}_c\to \mathrm{\Sigma }\pi$ and the portal ${\mathrm{\Lambda }}_c\to \mathrm{\Lambda }\rho \to \mathrm{\Sigma }\pi$ can make both the decay rate and sign of the asymmetry parameter to be consistent with data.

The exact way of treating flux shape uncertainties in unfolded, flux-averaged neutrino cross-section measurements can lead to subtle issues when comparing the results to model predictions. There is a difference between reporting a cross section in the (unknown) real flux, and reporting a cross section that was extrapolated from the real flux to a well-defined, fixed reference flux. Many current analyses do the former, while the results are compared to model predictions as if they were the latter. This leads to the flux shape uncertainty being ignored at least partially, potentially leading to wrong physics conclusions. A somewhat qualitative study of two results from T2K and MINERvA as examples suggests that the size of the effect is subdominant, but non-negligible for those measurements. This paper describes how the issue arises and details possible methods for treating the flux shape uncertainties correctly.

We obtain the gravitational form factors (GFFs) and investigate their applications for the description of the mechanical properties, i.e., the distributions of pressures, shear forces inside proton, and the mechanical radius, in a light-front quark-diquark model constructed by the soft-wall AdS/QCD. The GFFs, $A(Q^2)$ and $B(Q^2)$ are found to be consistent with the lattice QCD, while the qualitative behavior of the $D$-term form factor is in agreement with the extracted data from the deeply virtual Compton scattering (DVCS) experiments at JLab, the lattice QCD, and the predictions of different phenomenological models. The pressure and shear force distributions are also consistent with the results of different models.

We search for lepton-number- and baryon-number-violating decays ${\tau }^{-}\to \overline{p}{e}^{+}{e}^{-}$, $p{e}^{-}{e}^{-}$, $\overline{p}{e}^{+}{\mu }^{-}$, $\overline{p}{e}^{-}{\mu }^{+}$, $\overline{p}{\mu }^{+}{\mu }^{-}$, and $p{\mu }^{-}{\mu }^{-}$ using $921{\mathrm{fb}}^{-1}$ of data, equivalent to $(841\pm 12)\times {10}^6$ ${\tau }^{+}{\tau }^{-}$ events, recorded with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. In the absence of a signal, 90% confidence-level upper limits are set on the branching fractions of these decays in the range $(1.8-4.0)\times {10}^{-8}$. We set the world’s first limits on the first four channels and improve the existing limits by an order of magnitude for the last two channels.