Mon·Mar 25, 2019Monday·March 25, 2019

1. 01*

   New Observables in Inclusive Production of Quarkonia

   Jean-Philippe Lansberg🇫🇷

   After an introduction motivating the study of quarkonium production, we review the recent developments in the phenomenology of quarkonium production in inclusive scatterings of hadrons and leptons. We naturally address data and predictions relevant for the LHC, the Tevatron, RHIC, HERA, LEP, B factories and EIC. An up-to-date discussion of the contributions from feed downs within the charmonium and bottomonium families as well as from b hadrons to charmonia is also provided. This contextualises an exhaustive overview of new observables such as the associated production along with a Standard Model boson (photon, W and Z), with another quarkonium, with another heavy quark as well as with light hadrons or jets. We address the relevance of these reactions in order to improve our understanding of the mechanisms underlying quarkonium production as well as the physics of multi-parton interactions, in particular the double parton scatterings. An outlook towards future studies and facilities concludes this review.

   hep-phhep-exnucl-exnucl-thPhys.Rept.(2020)·238 citations
2. 02*

   Finite-volume and magnetic effects on the phase structure of the three-flavor Nambu--Jona-Lasinio model

   L. M. Abreu🇧🇷 · E. B. S. Corrêa🇧🇷 · C. A. Linhares🇧🇷 · A. P. C. Malbouisson🇧🇷

   In this work we analyze the finite-volume and magnetic effects on the phase structure of a generalized version of Nambu--Jona-Lasinio model with three quark flavors. By making use of mean-field approximation and Schwinger's proper-time method in a toroidal topology with antiperiodic conditions, we investigate the gap equation solutions under the change of the size of compactified coordinates, strength of magnetic field, temperature and chemical potential. The 't Hooft interaction contributions are also evaluated. The thermodynamic behavior is strongly affected by the combined effects of relevant variables. The findings suggest that the broken phase is disfavored due to both increasing of temperature and chemical potential, and the drop of the cubic volume of size $L$, whereas it is stimulated with the augmentation of magnetic field. In particular, the reduction of $L$ (remarkably at $L\approx 0.5-3$~fm) engenders a reduction of the constituent masses for $u,d,s$-quarks through a crossover phase transition to the their corresponding current quark masses. On the other hand, the presence of a magnetic background generates greater values constituent quark masses, inducing smaller sizes and greater temperatures at which the constituent quark masses drop to the respective current ones.

   hep-phPRD(2019)·29 citations
3. 03*

   Flavour-alignment in an $S_3$-symmetric Higgs sector and its RG-behaviour

   Nabarun Chakrabarty🇹🇼 · Indrani Chakraborty

   A three Higgs-doublet model admitting an $S_3$-symmetry can predict the observed pattern of the quark masses and their mixings. However the same symmetry also introduces potential flavour-changing neutral currents at the tree level. We assume in this work that the scalar potential contains appropriate \emph{soft} $S_3$-breaking terms in order to keep the choices of the scalar masses flexible. We identify the parameters in the Yukawa Lagrangian in the quark sector responsible for such FCNCs and constrain them using data from some of the flavour physics observables like meson-decays and meson-mixings. We also validate the corresponding model parameter space with renormalisation group (RG) evaluation.

   hep-phCPC(2022)·3 citations
4. 04*

   A U-spin prediction for the CP-forbidden transition $e^{+}{e}^{-}\to D^0{\bar{D}}^0\to (K^{+}{K}^{-}{)}_D({\pi }^{+}{\pi }^{-}{)}_D$

   Zhi-zhong Xing🇨🇳

   The LHCb Collaboration has recently reported the discovery of direct CP violation in combined $D^0\to K^{+}{K}^{-}$ and $D^0\to {\pi }^{+}{\pi }^{-}$ decay modes at the $5.3\sigma$ level. Assuming U-spin symmetry (i.e., $d\leftrightarrow s$ interchange symmetry) for the strong-interaction parts of these two channels, we find that their corresponding direct CP-violating asymmetries are ${\mathcal{A}}_{\mathrm{CP}}^{}(K^{+}{K}^{-})\simeq \left(-7.7\pm 1.5\right)\times 10^{-4}$ and ${\mathcal{A}}_{\mathrm{CP}}^{}({\pi }^{+}{\pi }^{-})\simeq \left(7.7\pm 1.5\right)\times 10^{-4}$. The CP-forbidden transition $e^{+}{e}^{-}\to D^0{\bar{D}}^0\to {\left(K^{+}{K}^{-}\right)}_D^{}{\left({\pi }^{+}{\pi }^{-}\right)}_D^{}$ on the $\psi (3770)$ resonance is therefore expected to have a rate of $\mathcal{O}(10^{-10})$ or smaller under U-spin symmetry, and it can be observed at a high-luminosity super-$\tau$-charm factory if at least $10^{10}$ pairs of coherent $D^0$ and ${\bar{D}}^0$ events are accumulated.

   hep-phMod.Phys.Lett.A(2019)·13 citations
5. 05*

   Emerging patterns of New Physics with and without Lepton Flavour Universal contributions

   Marcel Algueró🇪🇸 · Bernat Capdevila🇪🇸 · Andreas Crivellin🇨🇭 · Sébastien Descotes-Genon🇫🇷 · Pere Masjuan🇪🇸 · Joaquim Matias🇪🇸 · Martín Novoa-Brunet🇫🇷 · Javier Virto🇩🇪

   We perform a model-independent global fit to $b\to s{\ell }^{+}{\ell }^{-}$ observables to confirm existing New Physics (NP) patterns (or scenarios) and to identify new ones emerging from the inclusion of the updated LHCb and Belle measurements of $R_K$ and $R_{K^{\ast }}$, respectively. Our analysis, updating Refs. [1,2] and including these new data, suggests the presence of right-handed couplings encoded in the Wilson coefficients ${\mathcal{C}}_{9^{\prime }\mu }$ and ${\mathcal{C}}_{10^{\prime }\mu }$. It also strengthens our earlier observation that a lepton flavour universality violating (LFUV) left-handed lepton coupling (${\mathcal{C}}_{9\mu }^{\mathrm{V}}=-{\mathcal{C}}_{10\mu }^{\mathrm{V}}$), often preferred from the model building point of view, accommodates the data better if lepton-flavour universal (LFU) NP is allowed, in particular in ${\mathcal{C}}_9^{\mathrm{U}}$. Furthermore, this scenario with LFU NP provides a simple and model-independent connection to the $b\to c\tau \nu$ anomalies, showing a preference of $\approx 7\sigma$ with respect to the SM. It may also explain why fits to the whole set of $b\to s{\ell }^{+}{\ell }^{-}$ data or to the subset of LFUV data exhibit stronger preferences for different NP scenarios. Finally, motivated by $Z^{\prime }$ models with vector-like quarks, we propose four new scenarios with LFU and LFUV NP contributions that give a very good fit to data. We provide also an addendum collecting our updated results after including the data for the $B\to K^{\ast }\mu \mu$ angular distribution released in 2020 by the LHCb collaboration.

   hep-phEPJC(2019)·292 citations
6. 06*

   Fifth forces and discrete symmetry breaking

   Peter Millington🇬🇧

   Modifications of general relativity often involve coupling additional scalar fields to the Ricci scalar, leading to scalar-tensor theories of Brans-Dicke type. If the additional scalar fields are light, they can give rise to long-range fifth forces, which are subject to stringent constraints from local tests of gravity. In this talk, we show that Yukawa-like fifth forces only arise for the Standard Model (SM) due to a mass mixing of the additional scalar with the Higgs field, and we emphasise the pivotal role played by discrete and continuous symmetry breaking. Quite remarkably, if one assumes that sufficiently light, non-minimally coupled scalar fields exist in nature, the non-observation of fifth forces has the potential to tell us about the structure of the SM Higgs sector and the origin of its symmetry breaking. Moreover, with these observations, we argue that certain classes of scalar-tensor theories are, up to and including their dimension-four operators, equivalent to Higgs-portal theories. In this way, ultra-light dark matter models may also exhibit fifth-force phenomenology, and we consider the impact on the dynamics of disk galaxies as an example.

   hep-phastro-ph.COastro-ph.GAgr-qcJ.Phys.Conf.Ser.(2020)·1 citation
7. 07*

   Continuing search for new physics in $b\to s\mu \mu$ decays: two operators at a time

   Ashutosh Kumar Alok🇮🇳 · Amol Dighe🇮🇳 · Shireen Gangal🇮🇳 · Dinesh Kumar🇵🇱

   The anomalies in the measurements of observables involving $b\to s\mu \mu$ decays, namely $R_K$, $R_{K^{\ast }}$, $P_5^{\prime }$, and $B_s^{\varphi }$, may be addressed by adding lepton-universality-violating new physics contributions to the effective operators ${\mathcal{O}}_9,{\mathcal{O}}_{10},{\mathcal{O}}_9^{\prime },{\mathcal{O}}_{10}^{\prime }$. We analyze all the scenarios where the new physics contributes to a pair of these operators at a time. We perform a global fit to all relevant data in the $b\to s$ sector to estimate the corresponding new Wilson coefficients, $C_9^{\mathrm{NP}},C_{10}^{\mathrm{NP}},C_9^{\prime },C_{10}^{\prime }$. In the light of the new data on $R_K$ and $R_{K^{\ast }}$ presented in Moriond 2019, we find that the scenarios with new physics contributions to the ($C_9^{\mathrm{NP}}$, $C_9^{\prime }$) or ($C_9^{\mathrm{NP}}$, $C_{10}^{\prime }$) pair remain the most favored ones. On the other hand, though the competing scenario ($C_9^{\mathrm{NP}}$, $C_{10}^{\mathrm{NP}}$) remains attractive, its advantage above the SM reduces significantly due to the tension that emerges between the $R_K$ and $R_{K^{\ast }}$ measurements with the new data. The movement of the $R_K$ measurement towards unity would also result in the re-emergence of the one-parameter scenario $C_9^{\mathrm{NP}}=-C_9^{\prime }$.

   hep-phhep-exJHEP(2019)·182 citations
8. 08*

   Generation of quasiparticles by flavor mixing and CP violation: heavy Majorana neutrinos, part I

   Chang-Hun Lee🇹🇼

   The phenomenology of flavor mixing of heavy Majorana neutrinos is studied. The physical degrees of freedom, which propagate like free particles until they decay in the presence of flavor mixing, are identified by diagonalizing the resummed propagator. It is shown that they should be interpreted as quasiparticles which lose Majorana nature.

   hep-ph0 citations
9. 09*

   New Physics in $b\to s{\ell }^{+}{\ell }^{-}$ confronts new data on Lepton Universality

   Marco Ciuchini🇮🇹 · António M. Coutinho🇮🇹 · Marco Fedele🇪🇸 · Enrico Franco🇮🇹 · Ayan Paul🇩🇪 · Luca Silvestrini🇮🇹 · Mauro Valli🇺🇸

   In light of the very recent updates on the $R_K$ and $R_{K^{\ast }}$ measurements from the LHCb and Belle collaborations, we systematically explore here imprints of New Physics in $b\to s{\ell }^{+}{\ell }^{-}$ transitions using the language of effective field theories. We focus on effects that violate Lepton Flavour Universality both in the Weak Effective Theory and in the Standard Model Effective Field Theory. In the Weak Effective Theory we find a preference for scenarios with the simultaneous presence of two operators, a left-handed quark current with vector muon coupling and a right-handed quark current with axial muon coupling, irrespective of the treatment of hadronic uncertainties. In the Standard Model Effective Field Theory we select different scenarios according to the treatment of hadronic effects: while an aggressive estimate of hadronic uncertainties points to the simultaneous presence of two operators, one with left-handed quark and muon couplings and one with left-handed quark and right-handed muon couplings, a more conservative treatment of hadronic matrix elements leaves room for a broader set of scenarios, including the one involving only the purely left-handed operator with muon coupling.

   hep-phhep-exEPJC(2019)·223 citations
10. 10*

    Gravitational wave energy budget in strongly supercooled phase transitions

    John Ellis🇬🇧 · Marek Lewicki🇬🇧 · José Miguel No🇪🇸 · Ville Vaskonen🇬🇧

    We derive efficiency factors for the production of gravitational waves through bubble collisions and plasma-related sources in strong phase transitions, and find the conditions under which the bubble collisions can contribute significantly to the signal. We use lattice simulations to clarify the dependence of the colliding bubbles on their initial state. We illustrate our findings in two examples, the Standard Model with an extra $|H{|}^6$ interaction and a classically scale-invariant $U(1{)}_{\mathrm{B}-\mathrm{L}}$ extension of the Standard Model. The contribution to the GW spectrum from bubble collisions is found to be negligible in the $|H{|}^6$ model, whereas it can play an important role in parts of the parameter space in the scale-invariant $U(1{)}_{\mathrm{B}-\mathrm{L}}$ model. In both cases the sound-wave period is much shorter than a Hubble time, suggesting a significant amplification of the turbulence-sourced signal. We find, however, that the peak of the plasma-sourced spectrum is still produced by sound waves with the slower-falling turbulence contribution becoming important off-peak.

    hep-phastro-ph.COJCAP(2019)·371 citations
11. 11*

    Jet grooming through reinforcement learning

    Stefano Carrazza🇮🇹 · Frédéric A. Dreyer🇬🇧

    We introduce a novel implementation of a reinforcement learning (RL) algorithm which is designed to find an optimal jet grooming strategy, a critical tool for collider experiments. The RL agent is trained with a reward function constructed to optimize the resulting jet properties, using both signal and background samples in a simultaneous multi-level training. We show that the grooming algorithm derived from the deep RL agent can match state-of-the-art techniques used at the Large Hadron Collider, resulting in improved mass resolution for boosted objects. Given a suitable reward function, the agent learns how to train a policy which optimally removes soft wide-angle radiation, allowing for a modular grooming technique that can be applied in a wide range of contexts. These results are accessible through the corresponding GroomRL framework.

    hep-phcs.LGhep-exstat.MLPRD(2019)·31 citations
12. 12*

    Heavy quarkonium electric dipole transitions in non-relativistic quantum field theory

    Sebastian Steinbeißer🇩🇪

    In this work we use the low-energy EFT called potential non-relativistic QCD (pNRQCD) to calculate the partial decay width of different $b\bar{b}$-states undergoing an electric dipole transition at next-to-next-to leading order (NNLO). Explicitly, the ${\chi }_{bJ}$, for $J=0,1,2$, and the $h_b$ are investigated by computing the processes ${\chi }_{bJ}\to {\rm Y}+\gamma$ and $h_b\to {\eta }_b+\gamma$. Relativistic corrections of relative order $v^2$ to the leading electric dipole operator are included. The analysis separates those contributions that account for the electromagnetic interaction terms in the pNRQCD Lagrangian, which are $v^2$ suppressed, and those that account for quarkonium state corrections of relative order $v$ and $v^2$. Within the last ones, corrections come from higher order potentials ($\frac{1}{m}$ and $\frac{1}{m^2}$ terms), and from higher order Fock states which account for the coupling of the quark-antiquark state to other low-energy degrees of freedom and thus demand non-perturbative input. Finally, the experimentally known branching fractions are used to predict the total decay with of the respective initial states.

    hep-ph0 citations
13. 13*

    Gravitational form factors of light mesons

    Adam Freese🇺🇸 · Ian C. Cloët🇺🇸

    We calculate the gravitational form factors of the pion, sigma meson, and rho meson in the Nambu-Jona-Lasinio (NJL) model of quantum chromodynamics. The canonical energy-momentum tensor (EMT) is used in their derivation, allowing the possibility of an antisymmetric contribution when the hadron has intrinsic spin. We show that the asymmetric graviton vertex arising from the canonical EMT satisfies a simpler Ward-Takahashi identity (WTI) than the symmetric graviton vertex of the Belinfante EMT. The necessity of fully dressing the graviton vertex through the relevant Bethe-Salpeter equation is demonstrated for observing both the WTI and a low-energy pion theorem. Lastly, we calculate static moments of the meson EMT decompositions, obtaining predictions for the meson mass radii. We find light cone mass radii of 0.27 fm for the pion, 0.32 fm for the sigma, and 0.25 fm for the rho. For the pion and rho, these are smaller than the light cone charge radii, respectively 0.51 fm and 0.45 fm, while we have a sigma charge radius of zero. Our light cone pion mass radius agrees with a phenomenological extraction from KEKB data.

    ↳ nucl-thhep-phPRC(2019)·84 citations
14. 14*

    Planck and Electroweak Scales Emerging from Weyl Conformal Gravity

    Ichiro Oda🇯🇵

    We show that the Planck mass scale can be generated from conformal gravity in the Weyl conformal geometry via the Coleman-Weinberg mechanism of dimensional transmutation where quantum corrections stemming from the gravitational field and the Weyl gauge field trigger the symmetry breakdown of a local Weyl symmetry. It is also shown that the vacuum expectation value of a scalar field is transmitted to a sector of the standard model through a potential involving the scale invariant part and the contribution from the Coleman-Weinberg mechanism, thereby generating the electroweak scale.

    ↳ hep-thgr-qchep-phPoS(2019)·10 citations
15. 15*

    Lattice calculation of the pion transition form factor with $N_f=2+1$ Wilson quarks

    Antoine Gérardin🇩🇪 · Harvey B. Meyer🇩🇪 · Andreas Nyffeler🇩🇪

    We present a lattice QCD calculation of the double-virtual neutral pion transition form factor, with the goal to cover the kinematic range relevant to hadronic light-by-light scattering in the muon $g-2$. Several improvements have been made compared to our previous work. First, we take into account the effects of the strange quark by using the $N_f=2+1$ CLS gauge ensembles. Secondly, we have implemented the on-shell $\mathcal{O}(a)$-improvement of the vector current to reduce the discretization effects associated with Wilson quarks. Finally, in order to have access to a wider range of photon virtualities, we have computed the transition form factor in a moving frame as well as in the pion rest-frame. After extrapolating the form factor to the continuum and to physical quark masses, we compare our results with phenomenology. We extract the normalization of the form factor with a precision of 3.5\% and confirm within our uncertainty previous somewhat conflicting estimates for a low-energy constant that appears in chiral perturbation theory for the decay ${\pi }^0\to \gamma \gamma$ at NLO. With additional input from experiment and theory, we reproduce recent estimates for the decay width $\Gamma ({\pi }^0\to \gamma \gamma )$. We also study the asymptotic large-$Q^2$ behavior of the transition form factor in the double-virtual case. Finally, we provide as our main result a more precise model-independent lattice estimate of the pion-pole contribution to hadronic light-by-light scattering in the muon $g-2$: $a_{\mu }^{\mathrm{HLbL};{\pi }^0}=(59.7\pm 3.6)\times 10^{-11}$. Using in addition the normalization of the form factor obtained by the PrimEx experiment, we get the lattice and data-driven estimate $a_{\mu }^{\mathrm{HLbL};{\pi }^0}=(62.3\pm 2.3)\times 10^{-11}$.

    ↳ hep-lathep-phPRD(2019)·462 citations
16. 16*

    Forward proton detectors in heavy ion physics

    Rafał Staszewski🇵🇱 · Krzysztof Cieśla🇵🇱 · Janusz J. Chwastowski🇵🇱

    The forward proton detectors, already existing at the LHC, are considered in the context of heavy ion collisions. It is shown that such detectors have the potential to measure nuclear debris originating from spectator nucleons. The geometric acceptance for different nuclei is studied, and how it is affected by the motion of the nucleons in the nucleus and by the experimental conditions. A possibility of reconstructing the impact parameter of the collision from the measurement of the nuclear fragments is discussed.

    ↳ physics.ins-dethep-exhep-phActa Phys.Polon.B(2019)·2 citations
17. 17*

    Resolving phase transitions with Discontinuous Galerkin methods

    Eduardo Grossi🇩🇪 · Nicolas Wink🇩🇪

    We demonstrate the applicability and advantages of Discontinuous Galerkin (DG) schemes in the context of the Functional Renormalization Group (FRG). We investigate the $O(N)$-model in the large $N$ limit. It is shown that the flow equation for the effective potential can be cast into a conservative form. We discuss results for the Riemann problem, as well as initial conditions leading to a first and second order phase transition. In particular, we unravel the mechanism underlying first order phase transitions, based on the formation of a shock in the derivative of the effective potential.

    ↳ hep-thcond-mat.stat-mechhep-phphysics.comp-phSciPost Phys.Core(2023)·73 citations
18. 18*

    Investigating the dark matter signal in the cosmic ray antiproton flux with the machine learning method

    Su-Jie Lin🇨🇳 · Xiao-Jun Bi🇨🇳 · Peng-Fei Yin🇨🇳

    We investigate the implications on the dark matter (DM) signal from the AMS-02 cosmic antiproton flux. Global fits to the data are performed under different propagation and hadronic interaction models. The uncertainties from the injection spectrum, propagation effects and solar modulation of the cosmic rays are taken into account comprehensively. Since we need to investigate extended parameter regions with multiple free parameters in the fit, the machine learning method is adopted to maintain a realistic time cost. We find all the effects considered in the fitting process interplay with each other, among which the hadronic interaction model is the most important factor affecting the result. In most hadronic interaction and CR propagation models no DM signal is found with significance larger than $2\sigma$ except that the EPOS-LHC interaction model requires a more than $3\sigma$ DM signal with DM mass around $1\mathrm{TeV}$. For the diffusive reacceleration propagation model there is a highly significant DM signal with mass around $100\mathrm{GeV}$. However, the signal becomes less than $1\sigma$ if we take a charge dependent solar modulation potential in the analysis.

    ↳ astro-ph.HEhep-phPRD(2019)·35 citations
19. 19*

    Primordial Black Holes from Thermal Inflation

    Konstantinos Dimopoulos🇬🇧 · Tommi Markkanen🇬🇧 · Antonio Racioppi🇪🇪 · Ville Vaskonen🇬🇧

    We present a novel mechanism for the production of primordial black holes (PBHs). The mechanism is based on a period of thermal inflation followed by fast-roll inflation due to tachyonic mass of order the Hubble scale. Large perturbations are generated at the end of the thermal inflation as the thermal inflaton potential turns from convex to concave. These perturbations can lead to copious production of PBHs when the relevant scales re-enter horizon. We show that such PBHs can naturally account for the observed dark matter in the Universe when the mass of the thermal inflaton is about $10^6$GeV and its coupling to the thermal bath preexisting the late inflation is of order unity. We consider also the possibility of forming the seeds of the supermassive black holes. In this case we find that the mass of the thermal inflaton is about $1$GeV, but its couplings have to be very small, $\sim 10^{-7}$. Finally we study a concrete realisation of our mechanism through a running mass model.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2019)·34 citations
20. 20*

    Measuring the Inflaton Coupling in the CMB

    Marco Drewes🇧🇪

    We study the perspectives to extract information about the microphysical parameters that governed the reheating process after cosmic inflation from CMB data. We identify conditions under which the inflaton coupling to other fields can be constrained for a given model of inflation without having to specify the details of the particle physics theory within which this model is realised. This is possible when the effective potential during reheating is approximately parabolic, and when the coupling constants are smaller than an upper bound that is determined by the ratios between the inflaton mass and the Planck mass or the scale of inflation. We consider scalar, Yukawa, and axion-like interactions and estimate that these conditions can be fulfilled if the inflaton coupling is comparable to the electron Yukawa coupling or smaller, and if the inflaton mass is larger than $10^5$ GeV. Constraining the order of magnitude of the coupling constant requires measuring the scalar-to-tensor ratio at the level of $10^{-3}$, which is possible with future CMB observatories. Such a measurement would provide an important clue to understand how a given model of inflation may be embedded into a more fundamental theory of nature.

    ↳ astro-ph.COhep-phJCAP(2022)·40 citations
21. 21*

    Symmetry properties of non-Hermitian PT-symmetric quantum field theories

    Peter Millington🇬🇧

    We describe recent progress in understanding the continuous symmetry properties of non-Hermitian, PT-symmetric quantum field theories. Focussing on a simple non-Hermitian theory composed of one complex scalar and one complex pseudoscalar, we revisit the derivation of Noether's theorem to show that the conserved currents of non-Hermitian theories correspond to transformations that do not leave the Lagrangian invariant. We illustrate the impact that this has on the consistent formulation of (Abelian) gauge theories by studying a non-Hermitian extension of scalar quantum electrodynamics. We consider the spontaneous breakdown of both global and local symmetries, and describe how the Goldstone theorem and the Englert-Brout-Higgs mechanism are borne out for non-Hermitian, PT-symmetric theories.

    ↳ hep-thhep-phquant-phJ.Phys.Conf.Ser.(2020)·12 citations
22. 22*

    The muon $g-2$: a brief overview of hadronic cross section data

    Alexander Keshavarzi🇺🇸

    The hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_{\mu }^{\mathrm{had},\mathrm{VP}}$ are evaluated dispersively via a combination of experimentally measured $e^{+}{e}^{-}\to \mathrm{hadrons}$ cross section data. Many experiments have dedicated programmes to precisely measure these final states, meaning that a vast amount of data is now available and that, in some cases, overall precision has reached the sub-percent level. However, data tensions are evident between measurements of the same hadronic channels from different experiments, which reduces the overall quality of the data combinations used to determine $a_{\mu }^{\mathrm{had},\mathrm{VP}}$. The inclusion of these data in the KNT18 analysis results in $a_{\mu }^{\mathrm{had},\mathrm{LO}\mathrm{VP}}=(693.26\pm 2.46)\times 10^{-10}$ and $a_{\mu }^{\mathrm{had},\mathrm{NLO}\mathrm{VP}}=(-9.82\pm 0.04)\times 10^{-10}$. The corresponding new estimate for the Standard Model prediction is found to be $a_{\mu }^{\mathrm{SM}}=(11659182.04\pm 3.56)\times 10^{-10}$, which is $3.7\sigma$ below the current experimental measurement.

    ↳ hep-exhep-phPoS(2019)·2 citations
23. 23*

    Coupled channels approach to $\eta N$ and ${\eta }^{\prime }N$ interactions

    Ales Cieply🇨🇿 · Peter C. Bruns🇨🇿

    We present a coupled channels separable potential approach to $\eta N$ and ${\eta }^{\prime }N$ interactions using a chiral-symmetric interaction kernel. The s-wave $\pi N$ amplitudes and ${\pi }^{-}p$ induced total cross sections are reproduced satisfactorily in a broad interval of energies despite limiting the channel space to two-body interactions of pseudoscalar mesons with the baryon ground-state octet. It is demonstrated that an explicit inclusion of the ${\eta }_0$ meson singlet field leads to a more attractive $\eta N$ interaction, with the real part of the scattering length exceeding 1 fm. The ${\eta }^{\prime }N$ diagonal coupling appears sufficient to generate an ${\eta }^{\prime }N$ bound state but the inter-channel dynamics moves the respective pole far from physical region making the ${\eta }^{\prime }N$ interaction repulsive at energies around the channel threshold. The $N^{\ast }(1535)$ and $N^{\ast }(1650)$ resonances are generated dynamically and the origin and properties of the $S$-matrix poles assigned to them are studied in detail. We also hint at a chance that the $N^{\ast }(1895)$ state might also be formed provided a suitably varied model setting is found.

    ↳ nucl-thhep-phNPA(2019)·16 citations

* 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.