Pion and kaon structural properties provide insights into the emergence of mass within the Standard Model and attendant modulations by the Higgs boson. Novel expressions of these effects, in impact parameter space and in mass and pressure profiles, are exposed via π and K generalised parton distributions, built using the overlap representation from light-front wave functions constrained by one-dimensional valence distribution functions that describe available data. Notably, e.g. K pressure profiles are spatially more compact than π profiles and both achieve near-core pressures of similar magnitude to that found in neutron stars.
In high energy particle collisions the shape of the event, i.e. the relative distribution of particles in momentum space, is often used to try to select events with certain topologies. It is claimed that an event shape observable like transverse sphericity is able to discriminate between jet-like events and events that are dominated by soft production from the underlying event. In this paper we investigate the relationship between the shape of the event and the number of jets found in the respective event for both e+e− and pp collisions using the PYTHIA model. In e+e− collisions, we find that the transverse sphericity of the event can be used effectively to either enhance or suppress the fraction of jets found in the selected sample, and can even discriminate between single, two, and multi-jet topologies. However, contrary to current literature, we find that in pp collisions this does not hold. It is shown that the transverse sphericity as well as the particle multiplicity is sensitive to the number of multi-parton interactions.
We make an updated review and a systematic and comprehensive analysis of the decays of Higgs bosons in the Standard Model (SM) and its three well-defined prototype extensions such as the complex singlet extension of the SM (cxSM), the four types of two Higgs-doublet models (2HDMs) without tree-level Higgs-mediated flavor-changing neutral current (FCNC) and the minimal supersymmetric extension of the SM (MSSM). We summarize the theoretical predictions for the decay widths of the SM Higgs boson and those of Higgs bosons appearing in its extensions taking account of all possible decay modes. We incorporate them to study and analyze decay patterns of CP-even, CP-odd, and CP-mixed neutral Higgs bosons and charged ones. We put special focus on the properties of a neutral Higgs boson with mass about 125 GeV discovered at the LHC and present constraints obtained from precision analysis of it. This review is intended to be self-contained and consolidated by coherently integrating relevant physics information for studying decays of Higgs bosons in the SM and beyond.
Recently, the LHCb Collaboration reported a new structure Pcs(4459) with a mass of 19 MeV below the ΞcDˉ∗ threshold. It may be a candidate of molecular state from the ΞcDˉ∗ interaction. In the current work, we perform a coupled-channel study of the Ξc∗Dˉ∗, Ξc′Dˉ∗, Ξc∗Dˉ, ΞcDˉ∗, Ξc′Dˉ, and ΞcDˉ interactions in the quasipotential Bethe-Salpeter equation approach. With the help of the heavy quark chiral effective Lagrangian, the potential is constructed by light meson exchanges. Two ΞcDˉ∗ molecular states are produced with spin parities JP=1/2− and 3/2−. The lower state with 3/2− can be related to the observed Pcs(4450) while two-peak structure cannot be excluded. Within the same model, other strange hidden-charm pentaquarks are also predicted. Two states with spin parities 1/2− and 3/2− are predicted near the Ξc′Dˉ, ΞcDˉ, and Ξc∗Dˉ thresholds, respectively. As two states near ΞcDˉ∗ threshold, two states are produced with 1/2− and 3/2− near the Ξc′Dˉ∗ threshold. The couplings of the molecular states to the considered channels are also discussed. The experimental research of those states are helpful to understand the origin and internal structure of the Pcs and Pc states.
We consider the minimal seesaw model, the Standard Model extended by two right-handed neutrinos, for explaining the neutrino masses and mixing angles measured in oscillation experiments. When one of right-handed neutrinos is lighter than the electroweak scale, it can give a sizable contribution to neutrinoless double beta (0νββ) decay. We show that the detection of the 0νββ decay by future experiments gives a significant implication to the search for such light right-handed neutrino.
We study the observability of new interactions which modify Higgs-pair production via vector-boson fusion processes at the LHC and at future proton-proton colliders. In an effective-Lagrangian approach, we explore in particular the effect of the operator h2WμνaWa,μν, which describes the interaction of the Higgs boson with transverse vector-boson polarization modes. By tagging highly boosted Higgs bosons in the final state, we determine projected bounds for the coefficient of this operator at the LHC and at a future 27 TeV or 100 TeV collider. Taking into account unitarity constraints, we estimate the new-physics discovery potential of Higgs pair production in this channel.
The LHCb Collaboration announced the observation of doubly charmed baryon through Ξcc++→Λc+K−π+π+ in 2017. Since then, a series of studies of doubly heavy baryons have been presented. Ξcc++ was discovered through nonleptonic four-body decay mode, and experimental data has indicated that the decay modes of Ξcc++ are not saturated by two and three-body intermediate states. In this work, we analyze the four-body weak decays of doubly heavy baryons Ξcc++,Ξcc+, and Ωcc+. Decay amplitudes for various channels are parametrized in terms of SU(3) irreducible amplitudes. We point out that branching fractions for Cabibbo-allowed processes Ξcc+→Λc+π+π0K−, Ωcc+→Λc+π+K0K− would be helpful to search for Ξcc+ and Ωcc+ in future measurements at experimental facilities like LHC, Belle II, and CEPC.
We show that using renormalization-group summation to generate the QCD radiative corrections to the π−γ transition form factor, calculated with lightcone sum rules (LCSR), renders the strong coupling free of Landau singularities while preserving the QCD form-factor asymptotics. This enables a reliable applicability of the LCSR method to momenta well below 1 GeV2. This way, one can use the new preliminary BESIII data with unprecedented accuracy below 1.5 GeV2 to fine tune the prefactor of the twist-six contribution. Using a combined fit to all available data below 3.1 GeV2, we are able to determine all nonperturbative scale parameters and a few Gegenbauer coefficients entering the calculation of the form factor. Employing these ingredients, we determine a pion distribution amplitude with conformal coefficients (b2,b4) that agree at the 1σ level with the data for Q2⩽3.1 GeV2 and fulfill at the same time the lattice constraints on b2 at N3LO together with the constraints from QCD sum rules with nonlocal condensates.The form-factor prediction calculated herewith reproduces the data below 1 GeV2 significantly better than analogous predictions based on a fixed-order power-series expansion in the strong coupling constant.
We investigate features of the deconfinement phase transition in an SU(Nc) gauge theory as revealed by fluctuations of the order parameter. The tool of choice is an effective model built from one-loop expressions of the field determinants of gluon and ghost, in the presence of a Polyakov loop background field. We show that the curvature masses associated with the Cartan angles, which serve as a proxy to study the A0-gluon screening mass, show a characteristic dip in the vicinity of the transition temperature. The strength of the observables, which reflects a competition between the confining and the deconfining forces, is sensitive to assumptions of dynamics, thus provides an interesting link between the Z(Nc) vacuum structure and the properties of gluon and ghost propagators.
We combine SU(5) Grand Unified Theories (GUTs) with A4 modular symmetry and present a comprehensive analysis of the resulting quark and lepton mass matrices for all the simplest cases. Classifying the models according to the representation assignments of the matter fields under A4, we find that there are seven types of SU(5) models with A4 modular symmetry. We present 53 benchmark models with the fewest free parameters. The parameter space of each model is scanned to optimize the agreement between predictions and experimental data, and predictions for the masses and mixing parameters of quarks and leptons are given at the best fitting points. The best fit predictions for the leptonic CP violating Dirac phase, the lightest neutrino mass and the neutrinoless double beta decay parameter when displayed graphically are observed to cover a wide range of possible values, but are clustered around particular regions, allowing future neutrino experiments to discriminate between the different types of models.
The high energy Operator Product Expansion for the product of two electromagnetic currents is extended to the sub-eikonal level in a rigorous way. I calculate the impact factors for polarized and unpolarized structure functions, define new distribution functions, and derive the evolution equations for unpolarized and polarized structure functions in the flavor singlet and non-singlet case.
Recently unpolarized and polarized J/ψ(Υ) production at the Electron-Ion Collider (EIC) has been proposed as a new way to extract two poorly known color-octet NRQCD long-distance matrix elements: ⟨0∣O8J/ψ(1S0)∣0⟩ and ⟨0∣O8J/ψ(3P0)∣0⟩. The proposed method is based on a comparison to open heavy-quark pair production ideally performed at the same kinematics. In this paper we analyze this proposal in more detail and provide predictions for the EIC based on the available determinations of the color-octet matrix elements. We also propose two additional methods that do not require comparison to open heavy-quark pair production.
After inflation the Universe presumably undergoes a phase of reheating which in effect starts the thermal big bang cosmology. However, so far we have very little direct experimental or observational evidence of this important phase of the Universe. In this letter, we argue that measuring the spectrum of freely propagating relativistic particles, i.e. dark radiation, produced during reheating may provide us with powerful information on the reheating phase. To demonstrate this possibility we consider a situation where the dark radiation is produced in the decays of heavy, non-relativistic particles. We show that the spectrum crucially depends on whether the heavy particle once dominated the Universe or not. Characteristic features caused by the dependence on the number of the relativistic degrees of freedom may even allow to infer the temperature when the decay of the heavy particle occurred.
We explore whether the axion which solves the strong CP problem can naturally be much lighter than the canonical QCD axion. The ZN symmetry proposed by Hook, with N mirror and degenerate worlds coexisting in Nature and linked by the axion field, is considered in terms of generic effective axion couplings. We show that the total potential is safely approximated by a single cosine in the large N limit, and we determine the analytical formula for the exponentially suppressed axion mass. The resulting universal enhancement of all axion interactions relative to those of the canonical QCD axion has a strong impact on the prospects of axion-like particle experiments such as ALPS II, IAXO and many others. The finite density axion potential is also analyzed and we show that the ZN asymmetric background of high-density stellar environments sets already significant model-independent constraints: 3≤N≲47 for an axion scale fa≲2.4×1015 GeV, with tantalizing discovery prospects for any value of fa and down to N∼9 with future neutron star and gravitational wave data, down to the ultra-light mass region. In addition, two specific ultraviolet ZN completions are developed: a composite axion one and a KSVZ-like model with improved Peccei-Quinn quality.
We quantify the impact of unpolarized lepton-proton and lepton-nucleus inclusive deep-inelastic scattering (DIS) cross section measurements from the future Electron-Ion Collider (EIC) on the proton and nuclear parton distribution functions (PDFs). To this purpose we include neutral- and charged-current DIS pseudodata in a self-consistent set of proton and nuclear global PDF determinations based on the NNPDF methodology. We demonstrate that the EIC measurements will reduce the uncertainty of the light quark PDFs of the proton at large values of the momentum fraction x, and, more significantly, of the quark and gluon PDFs of heavy nuclei, especially at small and large x. We illustrate the implications of the improved precision of nuclear PDFs for the interaction of ultra-high energy cosmic neutrinos with matter.
After the discovery of the double-charm baryon Ξcc++ by LHCb, one of the most important topics is to search for the bottom-charm baryons which contain a b quark, a c quark and a light quark. In this work, we study the two-body non-leptonic weak decays of a bottom-charm baryon into a spin-1/2 bottomed baryon and a light pseudoscalar meson with the short-distance contributions calculated under the factorization hypothesis and the long-distance contributions considering the final-state-interaction effects. The branching fractions of all fifty-seven decay channels are estimated. The results indicate that Ξbc+→Ξb0π+, Ξbc0→Ξb−π+ and Ωbc0→Ωb−π+ decay modes have relatively large decay rates and thus could be used to experimentally search for the bottom-charm baryons. The topological diagrams and the SU(3) symmetry of bottom-charm baryon decays are discussed.
In the same base setup as Sakharov's induced gravity, we investigate emergence of gravity in effective quantum field theories (QFT), with particular emphasis on the gauge sector in which gauge bosons acquire anomalous masses in proportion to the ultraviolet cutoff Λ℘. Drawing on the fact that Λ℘2 corrections explicitly break the gauge and Poincare symmetries, we find that it is possible to map Λ℘2 to spacetime curvature as a covariance relation and we find also that this map erases the anomalous gauge boson masses. The resulting framework describes gravity by the general relativity (GR) and matter by the QFT itself with logΛ℘ corrections (dimensional regularization). This QFT-GR concord predicts existence of new physics beyond the Standard Model such that the new physics can be a weakly-interacting or even a non-interacting sector comprising the dark matter, dark energy and possibly more. The concord has consequential implications for collider, astrophysical and cosmological phenomena.
STAR Collaboration: M. S. Abdallah · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · A. Aparin and 379 other authors
We report a systematic measurement of cumulants, Cn, for net-proton, proton and antiproton multiplicity distributions, and correlation functions, κn, for proton and antiproton multiplicity distributions up to the fourth order in Au+Au collisions at sNN = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4 and 200 GeV. The Cn and κn are presented as a function of collision energy, centrality and kinematic acceptance in rapidity, y, and transverse momentum, pT. The data were taken during the first phase of the Beam Energy Scan (BES) program (2010 -- 2017) at the BNL Relativistic Heavy Ion Collider (RHIC) facility. The measurements are carried out at midrapidity (∣y∣< 0.5) and transverse momentum 0.4 <pT< 2.0 GeV/c, using the STAR detector at RHIC. We observe a non-monotonic energy dependence (sNN = 7.7 -- 62.4 GeV) of the net-proton C4/C2 with the significance of 3.1σ for the 0-5\% central Au+Au collisions. This is consistent with the expectations of critical fluctuations in a QCD-inspired model. Thermal and transport model calculations show a monotonic variation with sNN. For the multiparticle correlation functions, we observe significant negative values for a two-particle correlation function, κ2, of protons and antiprotons, which are mainly due to the effects of baryon number conservation. Furthermore, it is found that the four-particle correlation function, κ4, of protons plays a role in determining the energy dependence of proton C4/C1 below 19.6 GeV, which cannot be understood by the effect of baryon number conservation.
LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 micro K-arcmin with a typical angular resolution of 0.5 deg. at 100GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes.
* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.