Thu·Dec 10, 2020Thursday·December 10, 2020

1. 01*

   Parton distributions from LHC, HERA, Tevatron and fixed target data: MSHT20 PDFs

   S. Bailey🇬🇧 · T. Cridge🇬🇧 · L. A. Harland-Lang🇬🇧 · A. D. Martin🇬🇧 · R.S. Thorne🇬🇧

   We present the new MSHT20 set of parton distribution functions (PDFs) of the proton, determined from global analyses of the available hard scattering data. The PDFs are made available at NNLO, NLO, and LO, and supersede the MMHT14 sets. They are obtained using the same basic framework, but the parameterisation is now adapted and extended, and there are 32 pairs of eigenvector PDFs. We also include a large number of new data sets: from the final HERA combined data on total and heavy flavour structure functions, to final Tevatron data, and in particular a significant number of new LHC 7 and 8 TeV data sets on vector boson production, inclusive jets and top quark distributions. We include up to NNLO QCD corrections for all data sets that play a major role in the fit, and NLO EW corrections where relevant. We find that these updates have an important impact on the PDFs, and for the first time the NNLO fit is strongly favoured over the NLO, reflecting the wider range and in particular increased precision of data included in the fit. There are some changes to central values and a significant reduction in the uncertainties of the PDFs in many, though not all, cases. Nonetheless, the PDFs and the resulting predictions are generally within one standard deviation of the MMHT14 results. The major changes are the $u-d$ valence quark difference at small $x$, due to the improved parameterisation and new precise data, the $\bar{d},\bar{u}$ difference at small $x$, due to a much improved parameterisation, and the strange quark PDF due to the effect of LHC $W,Z$ data and inclusion of new NNLO corrections for dimuon production in neutrino DIS. We discuss the phenomenological impact of our results, and in general find reduced uncertainties in predictions for processes such as Higgs, top quark pair and $W,Z$ production at post LHC Run-II energies.

   hep-phhep-exEPJC(2021)·679 citations
2. 02*

   Ghost Imaging of Dark Particles

   Juan Estrada🇺🇸 · Roni Harnik🇺🇸 · Dario Rodrigues🇺🇸 · Matias Senger🇨🇭

   We propose a new way to use optical tools from quantum imaging and quantum communication to search for physics beyond the standard model. Spontaneous parametric down conversion (SPDC) is a commonly used source of entangled photons in which pump photons convert to a signal-idler pair. We propose to search for "dark SPDC" (dSPDC) events in which a new dark sector particle replaces the idler. Though it does not interact, the presence of a dark particle can be inferred by the properties of the signal photon. Examples of dark states include axion-like-particles and dark photons. We show that the presence of an optical medium opens the phase space of the down-conversion process, or decay, which would be forbidden in vacuum. Search schemes are proposed which employ optical imaging and/or spectroscopy of the signal photons. The signal rates in our proposal scales with the second power of the feeble coupling to new physics, as opposed to light-shining-through-wall experiments whose signal scales with coupling to the fourth. We analyze the characteristics of optical media needed to enhance dSPDC and estimate the rate. A bench-top demonstration of a high resolution ghost imaging measurement is performed employing a Skipper-CCD to demonstrate its utility in a dSPDC search.

   hep-phhep-exquant-phPRX Quantum(2021)·13 citations
3. 03*

   Precision physics with inclusive QCD processes

   Antonio Pich🇪🇸

   The inclusive production of hadrons through electroweak currents can be rigorously analysed with short-distance theoretical tools. The associated observables are insensitive to the involved infrared behaviour of the strong interaction, allowing for very precise tests of Quantum Chromodynamics. The theoretical predictions for $\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})$ and the hadronic decay widths of the $\tau$ lepton and the $Z$, $W$ and Higgs bosons have reached an impressive accuracy of $\mathcal{O}({\alpha }_s^4)$. Precise experimental measurements of the $Z$ and $\tau$ hadronic widths have made possible the accurate determination of the strong coupling at two very different energy scales, providing a highly significant experimental verification of asymptotic freedom. A detailed discussion of the theoretical description of these processes and their current phenomenological status is presented. The most precise determinations of ${\alpha }_s$ from other sources are also briefly reviewed and compared with the fully-inclusive results.

   hep-phhep-exPPNP(2021)·41 citations
4. 04*

   Production of Thermal Axions across the ElectroWeak Phase Transition

   Fernando Arias-Aragon🇪🇸 · Francesco D'Eramo🇮🇹 · Ricardo Z. Ferreira🇸🇪 · Luca Merlo🇪🇸 · Alessio Notari🇪🇸

   Light axions can potentially leave a cosmic background, just like neutrinos. We complete the study of thermal axion production across the electroweak scale by providing a smooth and continuous treatment through the two phases. Focusing on both flavor conserving and violating couplings to third generation quarks, we compute the amount of axions produced via scatterings and decays of thermal bath particles. We perform a model independent analysis in terms of axion effective couplings, and we also make predictions for specific microscopic QCD axion scenarios. This observable effect, parameterized as it is conventional by an effective number of additional neutrinos, is above the $1\sigma$ sensitivity of future CMB-S4 surveys. Moreover, if one assumes no large hierarchies among dimensionless axion couplings to standard model particles, future axion helioscopes will provide a complementary probe for the parameter region we study.

   hep-phastro-ph.COJCAP(2021)·76 citations
5. 05*

   Searching for dark sectors in multi lepton final state in e+ e- collisions

   Paolo Ciafaloni🇮🇹 · Gabriele Martelli🇮🇹 · Mauro Raggi🇮🇹

   Electron positron collisions are a very promising environment to search for new physics, and in particular for dark sector related observables. The most challenging experimental problem in detecting dark sector candidates is the very high associated Standard Model background. For this reason it is important to identify observables that are, at the same time, minimally suppressed in the dark sector and highly suppressed in the Standard Model. One example is the $e^{+}{e}^{-}\to 3(e^{+}{e}^{-})$ process that can be mediated either by the production and subsequent decay of dark Higgs ($h^{\prime }$), $e^{+}{e}^{-}\to A^{\prime }{h}^{\prime }\to 6e$ or produced by the Standards Model process $e^{+}{e}^{-}\to 3(e^{+}{e}^{-})$. In the following letter we study the relative contribution to observed $e^{+}{e}^{-}\to 3(e^{+}{e}^{-})$ total cross section, coming from the $h^{\prime }$ mediated and from the Standard Model processes in the contest of fixed target and low energy collider experiments, with particular attention to the PADME experiment at the INFN Laboratori Nazionali di Frascati.

   hep-phhep-exJHEP(2021)·8 citations
6. 06*

   Deep Learning Analysis of Deeply Virtual Exclusive Photoproduction

   Jake Grigsby🇺🇸 · Brandon Kriesten🇺🇸 · Joshua Hoskins🇺🇸 · Simonetta Liuti🇺🇸 · Peter Alonzi🇺🇸 · Matthias Burkardt🇺🇸

   We present a Machine Learning based approach to the cross section and asymmetries for deeply virtual Compton scattering from an unpolarized proton target using both an unpolarized and polarized electron beam. Machine learning methods are needed to study and eventually interpret the outcome of deeply virtual exclusive experiments since these reactions are characterized by a complex final state with a larger number of kinematic variables and observables, exponentially increasing the difficulty of quantitative analyses. Our deep neural network (FemtoNet) uncovers emergent features in the data and learns an accurate approximation of the cross section that outperforms standard baselines. FemtoNet reveals that the predictions in the unpolarized case systematically show a smaller relative median error than the polarized that can be ascribed to the presence of the Bethe Heitler process. It also suggests that the $t$ dependence can be more easily extrapolated than for the other variables, namely the skewness, $\xi$ and four-momentum transfer, $Q^2$. Our approach is fully scalable and will be capable of handling larger data sets as they are released from future experiments.

   hep-phnucl-exphysics.comp-phphysics.data-anPRD(2021)·30 citations
7. 07*

   The two-loop contributions to muon MDM in $U(1{)}_X$ SSM

   Lu-Hao Su🇨🇳 · Shu-Min Zhao🇨🇳 · Xing-Xing Dong🇨🇳 · Dan-Dan Cui🇨🇳 · Tai-Fu Feng🇨🇳 · Hai-Bin Zhang🇨🇳

   The MSSM is extended to the $U(1{)}_X$SSM, whose local gauge group is $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y\times U(1{)}_X$. To obtain the $U(1{)}_X$SSM, we add the new superfields to the MSSM, namely: three Higgs singlets $\hat{\eta },\hat{\bar{\eta }},\hat{S}$ and right-handed neutrinos ${\hat{\nu }}_i$. It can give light neutrino tiny mass at the tree level through the seesaw mechanism. The study of the contribution of the two-loop diagrams to the MDM of muon under $U(1{)}_X$SSM provides the possibility for us to search for new physics. In the analytical calculation of the loop diagrams (one-loop and two-loop diagrams), the effective Lagrangian method is used to derive muon MDM. Here, the considered two-loop diagrams include Barr-Zee type diagrams and rainbow type two-loop diagrams, especially Z-Z rainbow two-loop diagram is taken into account. The obtained numerical results can reach $7.4\times 10^{-10}$, which can remedy the deviation between SM prediction and experimental data to some extent.

   hep-phEPJC(2021)·15 citations
8. 08*

   Inhomogeneous confining-deconfining phases in rotating plasmas

   M. N. Chernodub🇫🇷

   We discuss the effects of rotation on confining properties of gauge theories focusing on compact electrodynamics in two spatial dimensions as an analytically tractable model. We show that at finite temperature, the rotation leads to a deconfining transition starting from a certain distance from the rotation axis. A uniformly rotating confining system possesses, in addition to the usual confinement and deconfinement phases, a mixed inhomogeneous phase which hosts spatially separated confinement and deconfinement regions. The phase diagram thus has two different deconfining temperatures. The first deconfining temperature can be made arbitrarily low by sufficiently rapid rotation while the second deconfining temperature is largely unaffected by the rotation. Implications of our results for the phase diagram of QCD are presented. We point out that uniformly rotating quark-gluon plasma should therefore experience an inverse hadronization effect when the hadronization starts from the core of the rotating plasma rather than from its boundary.

   hep-phhep-lathep-thPRD(2021)·100 citations
9. 09*

   Di-photon decay of a light Higgs state in the BLSSM

   Ahmed Ali Abdelalim🇪🇬 · Biswaranjan Das🇪🇬 · Shaaban Khalil🇪🇬 · Stefano Moretti🇬🇧

   In the context of the $B-L$ Supersymmetric Standard Model (BLSSM), we investigate the consistency of a light Higgs boson, with mass around $90-95$ GeV, with the results of a search performed by the CMS collaboration in the di-photon channel at the integrated luminosity of 35.9 fb${}^{-1}$ and $\sqrt{s}$ = 13 TeV.

   hep-phNPB(2022)·44 citations
10. 10*

    Invisible neutrino decay : First vs second oscillation maximum

    Kaustav Chakraborty🇮🇳 · Debajyoti Dutta🇮🇳 · Srubabati Goswami🇮🇳 · Dipyaman Pramanik🇮🇳

    We study the physics potential of the long-baseline experiments T2HK, T2HKK and ESS$\nu$SB in the context of invisible neutrino decay. We consider normal mass ordering and assume that the state ${\nu }_3$ as unstable, decaying into sterile states during the flight and obtain constraints on the neutrino decay lifetime (${\tau }_3$). We find that T2HK, T2HKK and ESS$\nu$SB are sensitive to the decay-rate of ${\nu }_3$ for ${\tau }_3/m_3\le 2.72\times 10^{-11}$s/eV, ${\tau }_3/m_3\le 4.36\times 10^{-11}$s/eV and ${\tau }_3/m_3\le 2.43\times 10^{-11}$s/eV respectively at 3$\sigma$ C.L. We compare and contrast the sensitivities of the three experiments and specially investigate the role played by the mixing angle ${\theta }_{23}$. It is seen that for experiments with flux peak near the second oscillation maxima, the poorer sensitivity to ${\theta }_{23}$ results in weaker constraints on the decay lifetime. Although, T2HKK has one detector close to the second oscillation maxima, having another detector at the first oscillation maxima results in superior sensitivity to decay. In addition, we find a synergy between the two baselines of the T2HKK experiment which helps in giving a better sensitivity for ${\theta }_{23}$ in the higher octant. We discuss the octant sensitivity in presence of decay and show that there is an enhancement in sensitivity which occurs due to the contribution from the survival probability $P_{\mu \mu }$ which is more pronounced for the experiments at the second oscillation maxima. We also obtain the combined sensitivity of T2HK+ESS$\nu$SB and T2HKK+ESS$\nu$SB as ${\tau }_3/m_3\le 4.36\times 10^{-11}$s/eV and ${\tau }_3/m_3\le 5.53\times 10^{-11}$s/eV respectively at 3$\sigma$ C.L.

    hep-phJHEP(2021)·20 citations
11. 11*

    Observing the Minkowskian dynamics of the pion on the null-plane

    W. de Paula (ITA, S. Jose' dos Campos Brazil)🇧🇷 · E. Ydrefors (ITA, S. José dos Campos Brazil)🇧🇷 · J.H. Alvarenga Nogueira (ITA, SJC Brazil & INFN, Rome Italy)🇧🇷 · T. Frederico (ITA, S.Jose' dos Campos Brazil)🇧🇷 · G. Salmè (INFN, Rome Italy)🇮🇹

    A dynamical model is applied to the study of the pion valence light-front wave function, obtained from the actual solution of the Bethe-Salpeter equation in Minkowski space, resorting to the Nakanishi integral representation. The kernel is simplified to a ladder approximation containing constituent quarks, an effective massive gluon exchange, and the scale of the extended quark-gluon interaction vertex. These three input parameters carry the infrared scale {\Lambda}QCD and are fine-tuned to reproduce the pion weak decay constant, within a range suggested by lattice calculations. Besides f{\pi}, we present and discuss other interesting quantities on the null-plane, like: (i) the valence probability, (ii) the dynamical functions depending upon the longitudinal or the transverse components of the light-front (LF) momentum, represented by LF-momentum distributions and distribution amplitudes, and (iii) the probability densities both in the LF-momentum space and the 3D space given by the Cartesian product of the covariant Ioffe-time and transverse coordinates, in order to perform an analysis of the dynamical features in a complementary way. The proposed analysis of the Minkowskian dynamics inside the pion, though carried out at the initial stage, qualifies the Nakanishi integral representation as an appealing effective tool, with still unexplored potentialities to be exploited for addressing correlations between dynamics and observable properties.

    hep-phPRD(2021)·32 citations
12. 12*

    Thermodynamics from the quark condensate

    Philipp Isserstedt🇩🇪 · Christian S. Fischer🇩🇪 · Thorsten Steinert🇩🇪

    We present a method to compute thermodynamic quantities within functional continuum frameworks that is independent of the employed truncation. As a proof of principle, we first apply it to a Nambu-Jona-Lasinio model in mean-field approximation. Then, we use the method with solutions obtained from a coupled set of truncated Dyson-Schwinger equations for the quark and gluon propagators of (2+1)-flavor quantum chromodynamics in Landau gauge to obtain the pressure, entropy density, energy density, and interaction measure across the phase diagram of strong-interaction matter. We also discuss the limitation of the proposed method.

    hep-phPRD(2021)·22 citations
13. 13*

    Understanding the $f_0(980)$ and $a_0(980)$ masses as well as their widths

    Eef van Beveren🇵🇹 · George Rupp🇵🇹

    The low and approximately equal masses of the scalar mesons $f_0(980)$ and $a_0(980)$, as well as their relatively small decay widths, are impossible to understand in terms of standard $P$-wave quark-antiquark states. Here, these mesons are studied in a unitarised quark-meson model, together with the other light isoscalar scalar $f_0(500)$, as members of a complete scalar nonet below about 1 GeV. They are shown to be dynamical states generated by a combination of quark-confinement and strong-decay interactions, resulting in a large breaking of $SU(3{)}_{\mathrm{flavour}}$ symmetry. This is illustrated with several pole trajectories in the complex-energy plane as a function of the model's decay coupling constant. Also, experimental evidence is presented of a still much lighter scalar boson called $E(38)$, which may correspond to a novel kind of mesons predicted by V. N. Gribov, as an observable manifestation of a condensate of light quarks.

    hep-phhep-exWorld Scientific, Gribov-90 Memorial Volu…·3 citations
14. 14*

    Dual Subtractions

    Renato Maria Prisco🇮🇹 · Francesco Tramontano🇮🇹

    We propose a novel local subtraction scheme for the computation of Next-to-Leading Order contributions to theoretical predictions for scattering processes in perturbative Quantum Field Theory. With respect to well known schemes proposed since many years that build upon the analysis of the real radiation matrix elements, our construction starts from the loop diagrams and exploit their loop-tree dual representation. Our scheme implements exact phase space factorization, handles final state as well as initial state singularities and is suitable for both massless and massive particles.

    hep-phhep-exhep-thJHEP(2021)·33 citations
15. 15*

    Recent Progress in the Physics of Axions and Axion-Like Particles

    Kiwoon Choi🇰🇷 · Sang Hui Im🇰🇷 · Chang Sub Shin🇰🇷

    The axion is a light pseudoscalar particle postulated to solve issues with the Standard Model, including the strong CP problem and the origin of dark matter. In recent years, there has been remarkable progress in the physics of axions in several directions. An unusual type of axion-like particle termed the relaxion was proposed as a new solution to the weak scale hierarchy problem. There are also new ideas for laboratory, astrophysical, or cosmological searches for axions; such searches can probe a wide range of model parameters that were previously inaccessible. On the formal theory side, the weak gravity conjecture indicates a tension between quantum gravity and a trans-Planckian axion field excursion. Many of these developments involve axions with hierarchical couplings. In this article, we review recent progress in axion physics, with particular attention paid to hierarchies between axion couplings. We emphasize that the parameter regions of hierarchical axion couplings are the most accessible experimentally. Moreover, such regions are often where important theoretical questions in the field are addressed, and they can result from simple model-building mechanisms.

    hep-phhep-thAnn.Rev.Nucl.Part.Sci.(2021)·256 citations
16. 16*

    Insights into $Z_b(10610)$ and $Z_b(10650)$ from dipion transitions from ${\rm Y}(10860)$

    V. Baru🇩🇪 · E. Epelbaum🇩🇪 · A.A. Filin🇩🇪 · C. Hanhart🇩🇪 · R.V. Mizuk🇷🇺 · A.V. Nefediev🇷🇺 · S. Ropertz🇩🇪

    The dipion transitions ${\rm Y}(10860)\to {\pi }^{+}{\pi }^{-}{\rm Y}(nS)$ ($n=1,2,3$) are studied in the framework of a unitary and analytic coupled-channel formalism previously developed for analysing experimental data on the bottomoniumlike states $Z_b(10610)$ and $Z_b(10650)$ [Phys. Rev. D 98, 074023 (2018)] and predicting the properties of their spin partners [Phys. Rev. D 99, 094013 (2019)]. In this work we use a relatively simple but realistic version of this approach, where the scattering and production amplitudes are constructed employing only short-ranged interactions between the open- and hidden-flavour channels consistent with the constraints from heavy quark spin symmetry, for an extended analysis of the experimental line shapes. In particular, the transitions from the ${\rm Y}(10860)$ to the final states $\pi \pi h_b(mP)$ ($m=1,2$) and $\pi B^{(\ast )}{\bar{B}}^{\ast }$ already studied before, are now augmented by the ${\rm Y}(10860)\to {\pi }^{+}{\pi }^{-}{\rm Y}(nS)$ final states ($n=1,2,3$). This is achieved by employing dispersion theory to account for the final state interaction of the $\pi \pi$ subsystem including its coupling to the $K\bar{K}$ channel. Fits to the two-dimensional Dalitz plots for the ${\pi }^{+}{\pi }^{-}{\rm Y}$ final states were performed. Two real subtraction constants are adjusted to achieve the best description of the Dalitz plot for each ${\rm Y}(nS)$ $(n=1,2,3)$ while all the parameters related to the properties of the $Z_b$'s are kept fixed from the previous study. A good overall description of the data for all ${\rm Y}(10860)\to {\pi }^{+}{\pi }^{-}{\rm Y}(nS)$ channels achieved in this work provides additional strong support for the molecular interpretation of the $Z_b$ states.

    hep-phhep-exnucl-thPRD(2021)·26 citations
17. 17*

    Is $X(7200)$ the heavy anti-quark diquark symmetry partner of $X(3872)$?

    Ming-Zhu Liu🇨🇳 · Li-Sheng Geng🇨🇳

    The $D^{(\ast )}{\Xi }_{cc}^{(\ast )}$ system and ${\bar{\Xi }}_{cc}^{(\ast )}{\Xi }_{cc}^{(\ast )}$ system can be related to the $D^{(\ast )}{\bar{D}}^{(\ast )}$ system via heavy anti-quark di-quark symmetry (HADS). In this work, we employ a contact-range effective field theory to systematically investigate the likely existence of molecules in these systems in terms of the hypothesis that X(3872) is a $1^{++}$~$D{\bar{D}}^{\ast }$ bound state in the isospin symmetry limit, with some of the unknown low energy constants estimated using the light-meson saturation approximation. In the meson-meson system, a $J^{PC}=2^{++}$~${\bar{D}}^{\ast }{D}^{\ast }$ molecule commonly referred to as $X(4013)$ is reproduced, which is the heavy quark spin partner of $X(3872)$. In the meson-baryon system, we predict two triply charmed pentaquark molecules, $J^P=1/2^{-}$~$D^{\ast }{\Xi }_{cc}$ and $J^P=5/2^{-}$~$D^{\ast }{\Xi }_{cc}^{\ast }$. In the baryon-baryon system, there exist seven di-baryon molecules, $J^{PC}=0^{-+}$~${\bar{\Xi }}_{cc}{\Xi }_{cc}$, $J^{PC}=1^{--}$~${\bar{\Xi }}_{cc}{\Xi }_{cc}$, $J^{PC}=1^{-+}$~${\bar{\Xi }}_{cc}{\Xi }_{cc}^{\ast }$, $J^{PC}=1^{--}$~${\bar{\Xi }}_{cc}{\Xi }_{cc}^{\ast }$, $J^{PC}=2^{-+}$~${\bar{\Xi }}_{cc}{\Xi }_{cc}^{\ast }$, $J^{PC}=2^{-+}$~${\bar{\Xi }}_{cc}^{\ast }{\Xi }_{cc}^{\ast }$ and $J^{PC}=3^{--}$~${\bar{\Xi }}_{cc}^{\ast }{\Xi }_{cc}^{\ast }$. Among them, the $J^{PC}=0^{-+}$~${\bar{\Xi }}_{cc}{\Xi }_{cc}$ and/or $J^{PC}=1^{--}$~${\bar{\Xi }}_{cc}{\Xi }_{cc}$ molecules may contribute to the $X(7200)$ state recently observed by the LHCb Collaboration, which implies that $X(7200)$ can be related to $X(3872)$ via HADS. As a byproduct, with the heavy quark flavor symmetry we also study likely existence of molecular states in the $B^{(\ast )}{\bar{B}}^{(\ast )}$, ${\bar{B}}^{(\ast )}{\Xi }_{bb}^{(\ast )}$, and ${\bar{\Xi }}_{bb}^{(\ast )}{\Xi }_{bb}^{(\ast )}$ systems.

    hep-phEPJC(2021)·27 citations
18. 18*

    N${}^3$LO extraction of the Sivers function from SIDIS, Drell-Yan, and $W^{\pm }/Z$ data

    Marcin Bury🇩🇪 · Alexei Prokudin🇺🇸 · Alexey Vladimirov🇩🇪

    We perform the global analysis of polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS), pion-induced polarized Drell-Yan (DY), and $W^{\pm }/Z$ boson production data and extract the Sivers function for $u$, $d$, $s$ and for sea-quarks. We use the framework of transverse momentum dependent factorization at N${}^3$LO accuracy. The Qiu-Sterman function is determined in a model-independent way from the extracted Sivers function. We also evaluate the significance of the predicted sign change of Sivers function in DY with respect to SIDIS.

    hep-phhep-exnucl-thPRL(2021)·59 citations
19. 19*

    Minimal scoto-seesaw mechanism with spontaneous CP violation

    D. M. Barreiros🇵🇹 · F. R. Joaquim🇵🇹 · R. Srivastava🇮🇳 · J. W. F. Valle🇪🇸

    We propose simple scoto-seesaw models to account for dark matter and neutrino masses with spontaneous CP violation. This is achieved with a single horizontal ${\mathcal{Z}}_8$ discrete symmetry, broken to a residual ${\mathcal{Z}}_2$ subgroup responsible for stabilizing dark matter. CP is broken spontaneously via the complex vacuum expectation value of a scalar singlet, inducing leptonic CP-violating effects. We find that the imposed ${\mathcal{Z}}_8$ symmetry pushes the values of the Dirac CP phase and the lightest neutrino mass to ranges already probed by ongoing experiments, so that normal-ordered neutrino masses can be cornered by cosmological observations and neutrinoless double beta decay experiments.

    hep-phJHEP(2021)·37 citations
20. 20*

    Two-loop corrections to the Higgs trilinear coupling in models with extended scalar sectors

    Johannes Braathen🇩🇪 · Shinya Kanemura🇯🇵

    The Higgs trilinear coupling provides a unique opportunity to study the structure of the Higgs sector and probe indirect signs of BSM Physics -- even if new states are somehow hidden. In models with extended Higgs sectors, large deviations in the Higgs trilinear coupling can appear at one loop because of non-decoupling effects in the radiative corrections involving the additional scalar states. It is then natural to ask how two-loop corrections modify this result, and whether new large corrections can appear again. We present new results on the dominant two-loop corrections to the Higgs trilinear coupling in several models with extended scalar sectors. We illustrate the analytical expressions with numerical examples and show that, while they remain smaller than their one-loop counterparts and do not modify significantly the non-decoupling effects observed at one loop, the two-loop corrections are not entirely negligible -- a typical size being 10-20% of the one-loop corrections.

    hep-phPoS(2021)·1 citation
21. 21*

    Production of ${\eta }_c(1S,2S)$ in $e^{+}{e}^{-}$ and $pp$ collisions

    Izabela Babiarz🇵🇱 · Wolfgang Schäfer🇵🇱 · Antoni Szczurek🇵🇱

    We derive the light-front wave function (LFWF) representation of the ${\gamma }^{\star }{\gamma }^{\star }\to {\eta }_c(1S),{\eta }_c(2S)$ transition form factor $F(Q_1^2,Q_2^2)$ for two virtual photons in the initial state. For the LFWF, we use different models obtained from the solution of the Schrödinger equation for a variety of $c\bar{c}$ potentials. We compare our results to the BaBar experimental data for the ${\eta }_c(1S)$ transition form factor, for one real and one virtual photon. We observe that the onset of the asymptotic behaviour is strongly delayed and discuss applicability of the collinear and/or massless limit. In addition, we present a thorough analysis of ${\eta }_c(1S,2S)$ quarkonia hadroproduction in $k_{\perp }$-factorisation in the framework of the light-front potential approach for the quarkonium wave function. The off-shell matrix elements for the $g^{\star }{g}^{\star }\to {\eta }_c(1S,2S)$ vertices are derived. We discuss the importance of taking into account the gluon virtualities. We present the transverse momentum distributions of ${\eta }_c$ for several models of the unintegrated gluon distributions. Our calculations are performed for four distinct parametrizations for the $c\bar{c}$ interaction potential consistent with the meson spectra. We compare our results for ${\eta }_c(1S)$ to measurements by the LHCb collaboration and present predictions for ${\eta }_c(2S)$ production.

    hep-phPoS(2021)·3 citations
22. 22*

    Crossing Symmetric Dispersion Relations in QFTs

    Aninda Sinha🇮🇳 · Ahmadullah Zahed🇮🇳

    For 2-2 scattering in quantum field theories, the usual fixed $t$ dispersion relation exhibits only two-channel symmetry. This paper considers a crossing symmetric dispersion relation, reviving certain old ideas in the 1970s. Rather than the fixed $t$ dispersion relation, this needs a dispersion relation in a different variable $z$, which is related to the Mandelstam invariants $s,t,u$ via a parametric cubic relation making the crossing symmetry in the complex $z$ plane a geometric rotation. The resulting dispersion is manifestly three-channel crossing symmetric. We give simple derivations of certain known positivity conditions for effective field theories, including the null constraints, which lead to two sided bounds and derive a general set of new non-perturbative inequalities. We show how these inequalities enable us to locate the first massive string state from a low energy expansion of the four dilaton amplitude in type II string theory. We also show how a generalized (numerical) Froissart bound, valid for all energies, is obtained from this approach.

    ↳ hep-thhep-phPRL(2021)·174 citations
23. 23*

    Objective Bayesian approach to the Jeffreys-Lindley paradox

    Andrew Fowlie🇨🇳

    We consider the Jeffreys-Lindley paradox from an objective Bayesian perspective by attempting to find priors representing complete indifference to sample size in the problem. This means that we ensure that the prior for the unknown mean and the prior predictive for the $t$-statistic are independent of the sample size. If successful, this would lead to Bayesian model comparison that was independent of sample size and ameliorate the paradox. Unfortunately, it leads to an improper scale-invariant prior for the unknown mean. We show, however, that a truncated scale-invariant prior delays the dependence on sample size, which could be practically significant. Lastly, we shed light on the paradox by relating it to the fact that the scale-invariant prior is improper.

    ↳ stat.MEhep-phphysics.data-an0 citations
24. 24*

    GW190426_152155: a merger of neutron star-black hole or low mass binary black holes?

    Yin-Jie Li🇨🇳 · Ming-Zhe Han🇨🇳 · Shao-Peng Tang🇨🇳 · Yuan-Zhu Wang🇨🇳 · Yi-Ming Hu🇨🇳 · Qiang Yuan🇨🇳 · Yi-Zhong Fan🇨🇳 · Da-Ming Wei🇨🇳

    GW190426_152155 was recently reported as one of the 39 candidate gravitational wave (GW) events in \citet{2020arXiv201014527A}, which has an unusual source-frame chirp mass $\sim 2.4M_{\odot }$ and may be the first GW signal from a neutron star-black hole (NSBH) merger. Assuming an astrophysical origin, we reanalyze GW190426_152155 using several waveforms with different characteristics, and consider two different priors for the mass ratio of the binary (Uniform and LogUniform). We find that the results are influenced by the priors of mass ratio, and this candidate could also be from the merger of two low mass black holes (BH). In the case for a binary black hole (BBH) merger, the effective spin is likely negative and the effective precession spin is non-negligible. As for the NSBH merger, supposing the mass of the light object follow the distribution of current neutron stars (NSs) with a reasonably measured/constrained mass, the spin of the low mass BH is so small that is hard to generate bright electromagnetic emission. Finally, we estimate a merger rate of GW190426\_152155-like systems to be $59_{-51}^{+137}{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$.

    ↳ astro-ph.HEhep-ph11 citations
25. 25*

    A 5% measurement of the gravitational constant in the Large Magellanic Cloud

    Harry Desmond🇬🇧 · Jeremy Sakstein🇺🇸 · Bhuvnesh Jain🇺🇸

    We perform a novel test of General Relativity by measuring the gravitational constant in the Large Magellanic Cloud (LMC). The LMC contains six well-studied Cepheid variable stars in detached eclipsing binaries. Radial velocity and photometric observations enable a complete orbital solution, and precise measurements of the Cepheids' periods permit detailed stellar modelling. Both are sensitive to the strength of gravity, the former via Kepler's third law and the latter through the gravitational free-fall time. We jointly fit the observables for stellar parameters and the gravitational constant. Performing a full Markov Chain Monte Carlo analysis of the parameter space including all relevant nuisance parameters, we constrain the gravitational constant in the Large Magellanic Cloud relative to the Solar System to be $G_{\text{LMC}}/G_{\text{SS}}=0.93_{-0.04}^{+0.05}$. We discuss the implications of this 5% measurement of Newton's constant in another galaxy for dark energy and modified gravity theories. This result excludes one Cepheid, CEP-1812, which is an outlier and needs further study: it is either a highly unusual system to which our model does not apply, or it prefers $G_{\text{LMC}}<G_{\text{SS}}$ at $2.6\sigma$. We also obtain new bounds on critical parameters that appear in semi-analytic descriptions of stellar processes. In particular, we measure the mixing length parameter to be $\alpha =0.90_{-0.26}^{+0.36}$ (when assumed to be constant across our sample), and obtain constraints on the parameters describing turbulent dissipation and convective flux.

    ↳ astro-ph.COastro-ph.GAastro-ph.SRgr-qc+1PRD(2021)·10 citations
26. 26*

    Plasma-photon interaction in curved spacetime I: formalism and quasibound states around nonspinning black holes

    Enrico Cannizzaro🇮🇹 · Andrea Caputo🇮🇱 · Laura Sberna🇨🇦 · Paolo Pani🇮🇹

    We investigate the linear dynamics of an electromagnetic field propagating in curved spacetime in the presence of plasma. The dynamical equations are generically more involved and richer than the effective Proca equation adopted as a model in previous work. We discuss the general equations and focus on the case of a cold plasma in the background of a spherically-symmetric black hole, showing that the system admits plasma-driven, quasibound electromagnetic states that are prone to become superradiantly unstable when the black hole rotates. The quasibound states are different from those of the Proca equation and have some similarities with the case of a massive scalar field, suggesting that the linear instability can be strongly suppressed compared to previous estimates. Our framework provides the first step towards a full understanding of the plasma-photon interactions around astrophysical black holes.

    ↳ gr-qcastro-ph.HEhep-phPRD(2021)·41 citations
27. 27*

    Jets and elliptic flow correlations at low and high transverse momenta in ultrarelativistic A+A collisions

    L.V. Bravina🇳🇴 · G.Kh. Eyyubova🇷🇺 · V.L. Korotkikh🇷🇺 · I.P. Lokhtin🇷🇺 · S.V. Petrushanko🇷🇺 · A.M. Snigirev🇷🇺 · E.E. Zabrodin🇳🇴

    Data from the Large Hadron Collider on elliptic flow correlations at low and high $p_T$ from Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$~TeV are analyzed and interpreted in the framework of the HYDJET++ model. This model allows us to describe simultaneously the region of both low and high transverse momenta and, therefore, to reproduce the experimentally observed nontrivial centrality dependence of elliptic flow correlations. The origin of the correlations between low and high-$p_T$ flow components in peripheral lead-lead collisions is traced to correlations of particles in jets.

    ↳ nucl-thhep-phnucl-exPRC(2021)·11 citations
28. 28*

    Superfactory of bottomed hadrons Belle II

    S.I. Eidelman🇷🇺 · A.V. Nefediev🇷🇺 · P.N. Pakhlov🇷🇺 · V.I. Zhukova🇷🇺

    In 2018 the Belle II experiment, aimed at detailed studies of B-mesons, started operation at the electron-positron collider SuperKEKB at KEK (Japan). This was preceded by a long and quite successful work of the B-factories of previous generations, including the Belle experiment for which Belle II is a successor. This experiment is unique and has no analogues or competitors in the world. The spectrum of problems it is aimed at is quite broad: from studies of hadronic states containing heavy quarks to precision measurements and searches for New Physics beyond the Standard Model. This review describes specific features of the Belle II experiment, its ambitious goals and specific tasks, expected results of its work and the hopes related to its successful accomplishment.

    ↳ hep-exhep-phPhys.Usp.(2021)·6 citations
29. 29*

    Numerical Study of the Chiral Separation Effect in Two-Color QCD at Finite Density

    P. V. Buividovich🇬🇧 · D. Smith🇩🇪 · L. von Smekal🇩🇪

    We study the Chiral Separation Effect (CSE) in finite-density SU(2) lattice gauge theory with dynamical quarks. We find that the CSE is well described by the free quark result in the high-temperature quark-gluon plasma phase. As one enters the confinement regime with broken chiral symmetry at chemical potential smaller than half of the pion mass, the CSE response is gradually suppressed towards low temperatures in comparison to the free quark result. This suppression can be approximately described by assuming that the CSE current is proportional to the charge density, rather than the chemical potential, as suggested in the literature (ArXiv:1712.01256, Phys.Rev.D97(2018)085020). We also provide an upper bound on the contribution of disconnected fermionic diagrams to the CSE, which is consistent with zero within our statistical errors and small compared to that of the connected diagrams. Our results are obtained mainly in the QCD-like regime of SU(2) gauge theory at low densities, and hence should be at least qualitatively applicable to QCD as well.

    ↳ hep-lathep-phhep-thPRD(2021)·25 citations
30. 30*

    Tidal effects for spinning particles

    Rafael Aoude🇧🇪 · Kays Haddad🇩🇰 · Andreas Helset🇺🇸

    Expanding on the recent derivation of tidal actions for scalar particles, we present here the action for a tidally deformed spin-$1/2$ particle. Focusing on operators containing two powers of the Weyl tensor, we combine the Hilbert series with an on-shell amplitude basis to construct the tidal action. With the tidal action in hand, we compute the leading-post-Minkowskian tidal contributions to the spin-1/2 -- spin-1/2 amplitude, arising at $\mathcal{O}(G^2)$. Our amplitudes provide evidence that the observed long range spin-universality for the scattering of two point particles extends to the scattering of tidally deformed objects. From the scattering amplitude we find the conservative two-body Hamiltonian, linear and angular impulses, eikonal phase, spin kick, and aligned-spin scattering angle. We present analogous results in the electromagnetic case along the way.

    ↳ hep-thgr-qchep-phJHEP(2021)·80 citations
31. 31*

    Non-trivial black hole solutions in $f(R)$ gravitational theory

    G.G.L. Nashed🇪🇬 · S. Nojiri🇯🇵

    Recent observation shows that general relativity (GR) is not valid in the strong regime. $f(R)$ gravity where $R$ is the Ricci scalar, is regarded to be one of good candidates able to cure the anomalies appeared in the conventional general relativity. In this realm, we apply the equation of motions of $f(R)$ gravity to a spherically symmetric spacetime with two unknown functions and derive original black hole (BH) solutions without any constrains on the Ricci scalar as well as on the form of $f(R)$ gravity. Those solutions depend on a convolution function and are deviating from the Schwarzschild solution of the Einstein GR. These solutions are characterized by the gravitational mass of the system and the convolution function that in the asymptotic form gives extra terms that are responsible to make such BHs different from GR. Also, we show that these extra terms make the singularities of the invariants much weaker than those of the GR BH. We analyze such BHs using the trend of thermodynamics and show their consistency with the well known quantities in thermodynamics like the Hawking radiation, entropy and quasi-local energy. We also show that our BH solutions satisfy the first law of thermodynamics. Moreover, we study the stability analysis using the odd-type mode and shows that all the derived BHs are stable and have radial speed equal to one. Finally, using the geodesic deviations we derive the stability conditions of these BHs.

    ↳ gr-qchep-phhep-thPRD(2020)·65 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.