Mon·Dec 7, 2020Monday·December 7, 2020

1. 01*

   Electromagnetic form factors of ${\Sigma }^{+}$ and ${\Sigma }^{-}$ in the vector meson dominance model

   Zhong-Yi Li🇨🇳 · Ju-Jun Xie🇨🇳

   Based on the recently measurements of the $e^{+}{e}^{-}\to {\Sigma }^{+}{\bar{\Sigma }}^{-}$ and $e^{+}{e}^{-}\to {\Sigma }^{-}{\bar{\Sigma }}^{+}$ processes, the electromagnetic form factors of the hyperon ${\Sigma }^{+}$ and ${\Sigma }^{-}$ in the timelike region are investigate by using the vector meson dominance model. We have included the contributions from the $\rho$, $\omega$ and $\varphi$ mesons. The model parameters are determined with the BESIII experimental data on the timelike effective form factors $|G_{\mathrm{eff}}|$ of ${\Sigma }^{+}$ and ${\Sigma }^{-}$ for center-of-mass energy from 2.3864 to 3.02 GeV. Then, we analytically continue the electromagnetic form factors to spacelike region and evaluate the spacelike form factors of ${\Sigma }^{+}$ and ${\Sigma }^{-}$. The obtained electromagnetic form factors of the ${\Sigma }^{+}$ and ${\Sigma }^{-}$ baryons are comparable with other model calculations.

   hep-phCommun.Theor.Phys.(2021)·14 citations
2. 02*

   Ratio of cross-sections of kaons to pions produced in $pp$ collisions as a function of $\sqrt{s}$

   G.I. Lykasov🇷🇺 · A.I. Malakhov🇷🇺 · A.A. Zaitsev🇷🇺

   A calculation of the inclusive spectra of pions and kaons produced in $pp$ collisions as functions of their transverse momentum $p_t$ at mid-rapidity is presented within the self-similarity approach. A satisfactory description of the data within a wide range of initial energies is presented. We focus mainly on the ratio of cross-sections of $K^{\pm }$ to ${\pi }^{\pm }$ mesons produced in $pp$ collisions as a function of $\sqrt{s}$. A fast rise of this ratio, when the initial energy increases starting from the kaon production threshold up to $\sqrt{s}\simeq$ 20-30 Gev, is revealed together with its very slow increase up to LHC energies. The energy dependence of this ratio is due to the conservation laws of four-momenta and quantum numbers of the initial and produced hadrons, and to the Regge behavior of cross-sections at large energies. The more or less satisfactory agreement of these ratios with NA61-SHINE, RHIC and LHC data is demonstrated.

   hep-phEPJA(2021)·7 citations
3. 03*

   Relativistic Langevin dynamics: charm versus beauty

   Shuang Li🇨🇳 · Wei Xiong🇨🇳 · Renzhuo Wan🇨🇳

   The production of heavy quarks (charm and beauty) provides unique insights into the transport properties of the Quark-Gluon Plasma (QGP) in heavy-ion collisions. Experimentally, the nuclear modification factor $R_{\mathrm{AA}}$ and the azimuthal anisotropy coefficient $v_2$ of heavy-flavor mesons are powerful observables to study the medium-related effects, such as energy loss and collectivity, on the heavy quark propagation through the QGP evolution. The latest measurements of the prompt and non-prompt open heavy-flavor hadrons allow a systematic comparison of the transport behaviors probed by charm and beauty quarks. In this work we make such an attempt utilizing our recently developed framework. By performing a quantitative investigation of $R_{\mathrm{AA}}$ and $v_2$, it is found that both charm and beauty quarks are efficient probes to capture the dynamical features of QGP, in particular the resulting mass hierarchy for the energy loss and azimuthal anisotropy, which are well inherited by the various $D/B$-meson species. Moreover, our calculations can describe simultaneously $R_{\mathrm{AA}}$ and $v_2$ data for the prompt and non-prompt $D^0$ mesons in central ($0-10\%$) and semi-central ($30-50\%$) Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. The predictions for $B$-meson observables for upcoming experimental tests are also made down to the low momentum region.

   hep-phEPJC(2020)·27 citations
4. 04*

   Exotic States in a Holographic Theory

   H. G. Dosch🇩🇪 · S. J. Brodsky🇺🇸 · G. F. de Téramond🇨🇷 · M. Nielsen🇧🇷 · Liping Zou🇨🇳

   Supersymmetric Light Front Holographic QCD is a holographic theory, which not only describes the spectroscopy of mesons and baryons, but also predicts the existence and spectroscopy of tetraquarks. A discussion of the limitations of the theory is also presented.

   hep-phhep-thNucl.Part.Phys.Proc.(2021)·14 citations
5. 05*

   Atomic Form Factors and Inverse Primakoff Scattering of Axion

   Tomohiro Abe🇯🇵 · Koichi Hamaguchi🇯🇵 · Natsumi Nagata🇯🇵

   We reexamine the inverse Primakoff scattering of axions, whose scattering cross section depends on the distribution of electrons in target atoms. We evaluate it using a form factor computed with a relativistic Hartree-Fock wave function and compare it with the previous results obtained with those based on the screened Coulomb potential for the electrostatic field in the atom. We take xenon as an example for the target atom and show that the scattering cross section was overestimated by more than an order of magnitude for axions with $\lesssim O(10)$ keV energies, like solar axions. It is also found that inelastic scattering processes, in which the final state contains an excited or ionized atom, can be comparable or even be dominant when the size of momentum transfer is $\lesssim 1$ keV. For more energetic axions, on the other hand, the total scattering cross section is found to be well approximated by a simple expression and has little dependence on the atomic structure. As an application of this result, we consider supernova axions, whose energy is 10-100 MeV, and show that $O(1)$ inverse Primakoff events are expected for axions from a nearby supernova in the future neutrino experiments, which may warrant a more detailed study on the search strategy of this process.

   hep-phastro-ph.COhep-exPLB(2021)·23 citations
6. 06*

   Quark Gluon Jet Discrimination with Weakly Supervised Learning

   Jason Sang Hun Lee🇰🇷 · Sang Man Lee🇰🇷 · Yunjae Lee🇰🇷 · Inkyu Park🇰🇷 · Ian James Watson🇰🇷 · Seungjin Yang🇰🇷

   Deep learning techniques are currently being investigated for high energy physics experiments, to tackle a wide range of problems, with quark and gluon discrimination becoming a benchmark for new algorithms. One weakness is the traditional reliance on Monte Carlo simulations, which may not be well modelled at the detail required by deep learning algorithms. The weakly supervised learning paradigm gives an alternate route to classification, by using samples with different quark--gluon proportions instead of fully labeled samples. The paradigm has, therefore, huge potential for particle physics classification problems as these weakly supervised learning methods can be applied directly to collision data. In this study, we show that realistically simulated samples of dijet and Z+jet events can be used to discriminate between quark and gluon jets by using weakly supervised learning. We implement and compare the performance of weakly supervised learning for quark--gluon jet classification using three different machine learning methods: the jet image-based convolutional neural network, the particle-based recurrent neural network and the feature-based boosted decision tree.

   hep-phhep-exJ.Korean Phys.Soc.(2019)·21 citations
7. 07*

   Inclusive production of $f_2(1270)$ tensor mesons at the LHC via gluon-gluon fusion in the $k_t$-factorization approach

   Antoni Szczurek🇵🇱 · Piotr Lebiedowicz🇵🇱

   The cross section for inclusive production of $f_2(1270)$ meson is calculated. We include both the mechanism of gluon-gluon fusion as well as the $\pi \pi$ final-state rescattering. The contribution of the gluon-gluon fusion is calculated within the $k_t$-factorization approach with modern unintegrated gluon distribution functions (UGDFs). Some parameters for the $g^{\ast }{g}^{\ast }\to f_2$ vertex are extracted from the $\gamma \gamma \to f_2(1270)\to \pi \pi$ reactions. The results strongly depend on the parametrization of the $g^{\ast }{g}^{\ast }\to f_2(1270)$ form factor. Results of our model are compared to the ALICE preliminary data. The gluon-gluon fusion does not explain low-$p_t$ data but could be the dominant mechanism at somewhat larger meson transverse momenta. By adjusting some parameters the pion-pion rescattering can explain the low-$p_t$ region.

   hep-phhep-exPoS(2021)·0 citations
8. 08*

   May the four be with you: Novel IR-subtraction methods to tackle NNLO calculations

   W.J. Torres Bobadilla🇩🇪 · G.F.R. Sborlini🇩🇪 · P. Banerjee🇨🇭 · S. Catani🇮🇹 · A.L. Cherchiglia🇧🇷 · L. Cieri🇮🇹 · P.K. Dhani🇮🇹 · F. Driencourt-Mangin🇪🇸 · T. Engel🇨🇭 · G. Ferrera🇮🇹 · C. Gnendiger🇨🇭 · R.J. Hernandez-Pinto🇲🇽 and 12 other authors

   In this report, we present a discussion about different frameworks to perform precise higher-order computations for high-energy physics. These approaches implement novel strategies to deal with infrared and ultraviolet singularities in quantum field theories. A special emphasis is devoted to the local cancellation of these singularities, which can enhance the efficiency of computations and lead to discover novel mathematical properties in quantum field theories.

   hep-phhep-thEPJC(2021)·86 citations
9. 09*

   Coulomb Law in the Non-Uniform Euler-Heisenberg Theory

   A. D. Bermúdez Manjarres🇨🇴 · M. Nowakowski🇨🇴 · D. Batic🇦🇪

   We consider the non-linear classical field theory which results from adding to the Maxwell's Lagrangian the contributions from the weak-field Euler-Heisenberg Lagrangian and a non-uniform part which involves derivatives of the electric and magnetic fields. We focus on the electrostatic case where the magnetic field is set to zero, and we derive the modified Gauss law, resulting in a higher order differential equation. This equation gives the electric field produced by stationary charges in the higher order non-linear electrodynamics. Specializing for the case of a point charge, we investigate the solutions of the modified Gauss law and calculate the correction to the Coulomb law.

   hep-phphysics.atom-phInt.J.Mod.Phys.A(2020)·2 citations
10. 10*

    Towards a precision calculation of $N_{\mathrm{eff}}$ in the Standard Model II: Neutrino decoupling in the presence of flavour oscillations and finite-temperature QED

    Jack J. Bennett🇦🇺 · Gilles Buldgen🇧🇪 · Pablo F. de Salas🇸🇪 · Marco Drewes🇧🇪 · Stefano Gariazzo🇮🇹 · Sergio Pastor🇪🇸 · Yvonne Y. Y. Wong🇦🇺

    We present in this work a new calculation of the standard-model benchmark value for the effective number of neutrinos, $N_{\mathrm{eff}}^{\mathrm{SM}}$, that quantifies the cosmological neutrino-to-photon energy densities. The calculation takes into account neutrino flavour oscillations, finite-temperature effects in the quantum electrodynamics plasma to $\mathcal{O}(e^3)$, where $e$ is the elementary electric charge, and a full evaluation of the neutrino--neutrino collision integral. We provide furthermore a detailed assessment of the uncertainties in the benchmark $N_{\mathrm{eff}}^{\mathrm{SM}}$ value, through testing the value's dependence on (i)~optional approximate modelling of the weak collision integrals, (ii)~measurement errors in the physical parameters of the weak sector, and (iii)~numerical convergence, particularly in relation to momentum discretisation. Our new, recommended standard-model benchmark is $N_{\mathrm{eff}}^{\mathrm{SM}}=3.0440\pm 0.0002$, where the nominal uncertainty is attributed predominantly to errors incurred in the numerical solution procedure ($|\delta N_{\mathrm{eff}}|\sim 10^{-4}$), augmented by measurement errors in the solar mixing angle ${\sin }^2{\theta }_{12}$ ($|\delta N_{\mathrm{eff}}|\sim 10^{-4}$).

    hep-phastro-ph.COJCAP(2021)·406 citations
11. 11*

    Probing the muon g-2 anomaly with the Higgs boson at a Muon Collider

    Dario Buttazzo🇮🇹 · Paride Paradisi🇮🇹

    We point out that heavy new physics contributions in leptonic dipole moments and high-energy cross-sections of lepton pairs into Higgs bosons and photons are connected model-independently. In particular, we demonstrate that a muon collider, running at center-of-mass energies of several TeV, can provide a unique test of new physics in the muon g-2 through the study of high-energy processes such as mu+ mu- -> h gamma. This high-energy test would be of the utmost importance to shed light on the long-standing muon g-2 anomaly as it is not affected by the hadronic and experimental uncertainties entering the current low-energy determination of the muon g-2. Furthermore, we show that the current bound on the muon electric dipole moment can be improved by three orders of magnitude, down to few x 10^-22 e cm.

    hep-phhep-exPRD(2021)·117 citations
12. 12*

    Top, Higgs, Diboson and Electroweak Fit to the Standard Model Effective Field Theory

    John Ellis🇬🇧 · Maeve Madigan🇬🇧 · Ken Mimasu🇬🇧 · Veronica Sanz🇪🇸 · Tevong You🇨🇭

    The search for effective field theory deformations of the Standard Model (SM) is a major goal of particle physics that can benefit from a global approach in the framework of the Standard Model Effective Field Theory (SMEFT). For the first time, we include LHC data on top production and differential distributions together with Higgs production and decay rates and Simplified Template Cross-Section (STXS) measurements in a global fit, as well as precision electroweak and diboson measurements from LEP and the LHC, in a global analysis with SMEFT operators of dimension 6 included linearly. We present the constraints on the coefficients of these operators, both individually and when marginalised, in flavour-universal and top-specific scenarios, studying the interplay of these datasets and the correlations they induce in the SMEFT. We then explore the constraints that our linear SMEFT analysis imposes on specific ultra-violet completions of the Standard Model, including those with single additional fields and low-mass stop squarks. We also present a model-independent search for deformations of the SM that contribute to between two and five SMEFT operator coefficients. In no case do we find any significant evidence for physics beyond the SM. Our underlying $\mathtt{Fitmaker}$ public code provides a framework for future generalisations of our analysis, including a quadratic treatment of dimension-6 operators.

    hep-phhep-exJHEP(2021)·391 citations
13. 13*

    A Time-Varying Fine Structure Constant from Naturally Ultralight Dark Matter

    Dawid Brzeminski🇺🇸 · Zackaria Chacko🇺🇸 · Abhish Dev🇺🇸 · Anson Hook🇺🇸

    We present a class of models in which the coupling of the photon to an ultralight scalar field that has a time-dependent vacuum expectation value causes the fine structure constant to oscillate in time. The scalar field is assumed to constitute all or part of the observed dark matter. Its mass is protected against radiative corrections by a discrete ${\mathbb{Z}}_N$ exchange symmetry that relates the Standard Model to several copies to itself. The abundance of dark matter is set by the misalignment mechanism. We show that the oscillations in the fine structure constant are large enough to be observed in current and near-future experiments.

    hep-phPRD(2021)·57 citations
14. 14*

    Left-right symmetry and electric dipole moments. A global analysis

    Michael J. Ramsey-Musolf🇨🇳 · Juan Carlos Vasquez🇺🇸

    We perform a global fit using results of searches for electric dipole moments (EDM) of diamagnetic systems within the context of the minimal left-right symmetric model. In this way, we disentangle the new "left-right" electroweak and $\bar{\theta }$ contributions that cannot be separated using a single EDM system. Although the fit is done for a specific model, the approach can be applied to any particle physics model. Finally, we revisit the constraint on the $D$ coefficient in $\beta$-decay and find that current EDM bounds do not preclude observation of this T-violating effect in a possible next generation $\beta$-decay experiment.

    hep-phnucl-thPLB(2021)·21 citations
15. 15*

    Reconciling low and high redshift GRB luminosity correlations

    Lu Huang🇨🇳 · Zhiqi Huang🇨🇳 · Xiaolin Luo🇨🇳 · Xinbo He🇨🇳 · Yuhong Fang🇨🇳

    The correlation between the peak spectra energy ($E_p$) and the equivalent isotropic energy ($E_{\mathrm{iso}}$) of long gamma-ray bursts (GRBs), the so-called Amati relation, is often used to constrain the high-redshift Hubble diagram. Assuming Lambda cold dark matter ($\Lambda$CDM) cosmology, Wang et al. found a $\gtrsim 3\sigma$ tension in the data-calibrated Amati coefficients between low- and high-redshift GRB samples. To reduce the impact of fiducial cosmology, we use the Parameterization based on cosmic Age (PAge), an almost model-independent framework to trace the cosmological expansion history. We find that the low- and high-redshift tension in Amati coefficients stays almost the same for the broad class of models covered by PAge, indicating that the cosmological assumption is not the dominant driver of the redshift evolution of GRB luminosity correlation. Next, we analyze the selection effect due to flux limits in observations. We find Amati relation evolves much more significantly across energy scales of $E_{\mathrm{iso}}$. We debias the GRB data by selectively discarding samples to match low-$z$ and high-$z$ $E_{\mathrm{iso}}$ distributions. After debiasing, the Amati coefficients agree well between low-$z$ and high-$z$ data groups, whereas the evidence of $E_{\mathrm{iso}}$-dependence of Amati relation remains to be strong. Thus, the redshift evolution of GRB luminosity correlation can be fully interpreted as a selection bias, and does not imply cosmological evolution of GRBs.

    ↳ astro-ph.COastro-ph.HEgr-qchep-phPRD(2021)·20 citations
16. 16*

    A Twistorial Foundation for the Classical Double Copy

    Chris D. White🇬🇧

    The classical double copy relates exact solutions of gauge, gravity and other theories. Although widely studied, its origins and domain of applicability have remained mysterious. In this letter, we show that a particular incarnation - the Weyl double copy - can be derived using well-established ideas from twistor theory. As well as explaining where the Weyl double copy comes from, the twistor formalism also shows that it is more general than previously thought.

    ↳ hep-thgr-qchep-phmath-ph+1PRL(2021)·127 citations
17. 17*

    Quark-Gluon Jet Discrimination Using Convolutional Neural Networks

    Jason Sang Hun Lee🇰🇷 · Inkyu Park🇰🇷 · Ian James Watson🇰🇷 · Seungjin Yang🇰🇷

    Currently, newly developed artificial intelligence techniques, in particular convolutional neural networks, are being investigated for use in data-processing and classification of particle physics collider data. One such challenging task is to distinguish quark-initiated jets from gluon-initiated jets. Following previous work, we treat the jet as an image by pixelizing track information and calorimeter deposits as reconstructed by the detector. We test the deep learning paradigm by training several recently developed, state-of-the-art convolutional neural networks on the quark-gluon discrimination task. We compare the results obtained using various network architectures trained for quark-gluon discrimination and also a boosted decision tree (BDT) trained on summary variables.

    ↳ hep-exhep-phJ.Korean Phys.Soc.(2019)·37 citations
18. 18*

    Detecting the brightest HAWC sources with IceCube in the upcoming years

    Viviana Niro🇫🇷

    Among the gamma-ray sources detected by the HAWC observatory, we consider in details in this work the gamma-ray sources eHWC J1907+063 and eHWC J2019+368. These two sources belong to the three most luminous sources detected by HAWC, with emission above 100 TeV. In addition to those, we have considered also a source for which IceCube currently report an excess in neutrinos, the 2HWC J1857+027 source. For these sources, we show the prediction for neutrinos at the IceCube detector. Moreover, we present the calculation of the statistical significance, considering 10 and 20 years of running time, and we comment on the current results reported by the collaboration. We found that a detection at 3$\sigma$ or more should be within reach of the next decade for the sources eHWC J1907+063 and eHWC J2019+368. Instead, the detection at about 3$\sigma$ of the 2HWC J1857+027 source will depend on the specific value of the flux, on the extension of the source and on the cut-off energy.

    ↳ astro-ph.HEhep-phPRD(2021)·7 citations
19. 19*

    Two populations of LIGO-Virgo black holes

    Gert Hütsi🇪🇪 · Martti Raidal🇪🇪 · Ville Vaskonen🇪🇸 · Hardi Veermäe🇪🇪

    We analyse the LIGO-Virgo data, including the recently released GWTC-2 dataset, to test a hypothesis that the data contains more than one population of black holes. We perform a maximum likelihood analysis including a population of astrophysical black holes with a truncated power-law mass function whose merger rate follows from star formation rate, and a population of primordial black holes for which we consider log-normal and critical collapse mass functions. We find that primordial black holes alone are strongly disfavoured by the data, while the best fit is obtained for the template combining astrophysical and primordial merger rates. Alternatively, the data may hint towards two different astrophysical black hole populations. We also update the constraints on primordial black hole abundance from LIGO-Virgo observations finding that in the $2-400M_{\odot }$ mass range they must comprise less than 0.2% of dark matter.

    ↳ astro-ph.COastro-ph.HEhep-phJCAP(2021)·256 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.