Fri·Jan 31, 2020Friday·January 31, 2020

1. 01*

   Casimir effect in polymer scalar field theory

   C. A. Escobar🇲🇽 · E. Chan-López🇲🇽 · A. Martín-Ruiz🇲🇽

   In this paper, we study the Casimir effect in the classical geometry of two parallel conducting plates, separated by a distance $L$, due to the presence of a minimal length $\lambda$ arising from a background independent (polymer) quantization scheme. To this end, we polymer-quantize the classical Klein-Gordon Hamiltonian for a massive scalar field confined between the plates and obtain the energy spectrum. The minimal length scale of the theory introduces a natural cutoff for the momenta in the plane parallel to the plates and a maximum number of discrete modes between the plates. The zero-point energy is calculated by summing over the modes, and by assuming $\lambda \ll L$, we expressed it as an expansion in powers of $1/N$, being $N=L/\lambda$ the number of points between the plates. Closed analytical expressions are obtained for the Casimir energy in the cases of small and large scalar mass limits.

   hep-phPRD(2020)·5 citations
2. 02*

   Simulation of electron-proton scattering events by a Feature-Augmented and Transformed Generative Adversarial Network (FAT-GAN)

   Yasir Alanazi🇺🇸 · N. Sato🇺🇸 · Tianbo Liu🇺🇸 · W. Melnitchouk🇺🇸 · Pawel Ambrozewicz🇺🇸 · Florian Hauenstein🇺🇸 · Michelle P. Kuchera🇺🇸 · Evan Pritchard🇺🇸 · Michael Robertson🇺🇸 · Ryan Strauss🇺🇸 · Luisa Velasco🇺🇸 · Yaohang Li🇺🇸

   We apply generative adversarial network (GAN) technology to build an event generator that simulates particle production in electron-proton scattering that is free of theoretical assumptions about underlying particle dynamics. The difficulty of efficiently training a GAN event simulator lies in learning the complicated patterns of the distributions of the particles physical properties. We develop a GAN that selects a set of transformed features from particle momenta that can be generated easily by the generator, and uses these to produce a set of augmented features that improve the sensitivity of the discriminator. The new Feature-Augmented and Transformed GAN (FAT-GAN) is able to faithfully reproduce the distribution of final state electron momenta in inclusive electron scattering, without the need for input derived from domain-based theoretical assumptions. The developed technology can play a significant role in boosting the science of existing and future accelerator facilities, such as the Electron-Ion Collider.

   hep-phcs.LGhep-exstat.MLProceedings of the Thirtieth Internationa…·77 citations
3. 03*

   Electromagnetic radiation from the pre-equilibrium/pre-hydro stage of the quark-gluon plasma

   Jessica Churchill🇨🇦 · Li Yan🇨🇳 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

   Photons produced in the pre-equilibrium/pre-hydro stage of the quark-gluon plasma produced in relativistic heavy-ion collisions were computed using parton distribution functions obtained from solutions of the Boltzmann equation. The effect of the initial gluon momentum anisotropy $\xi$ and the dependence on the saturation momentum $Q_s$ was investigated. We see that small $Q_s$ results in a photon yield enhancement, whereas a larger $Q_s$ results in a pre-equilibrium photon suppression, owing to the strict constraint of matching to experimental energy density.

   hep-phnucl-exnucl-thNPA(2021)·8 citations
4. 04*

   $\mu$-$\tau$ symmetry breaking and CP violation in the neutrino mass matrix

   Takeshi Fukuyama🇯🇵 · Yukihiro Mimura🇯🇵

   The $\mu$-$\tau$ exchange symmetry in the neutrino mass matrix and its breaking as a perturbation are discussed. The exact $\mu$-$\tau$ symmetry restricts the 2-3 and 1-3 neutrino mixing angles as ${\theta }_{23}=\pi /4$ and ${\theta }_{13}=0$ at a zeroth order level. We claim that the $\mu$-$\tau$ symmetry breaking prefers a large CP violation to realize the observed value of ${\theta }_{13}$ and to keep ${\theta }_{23}$ nearly maximal, though an artificial choice of the $\mu$-$\tau$ breaking can tune ${\theta }_{23}$, irrespective of the CP phase. We exhibit several relations among the deviation of ${\theta }_{23}$ from $\pi /4$, ${\theta }_{13}$ and Dirac CP phase $\delta$, which are useful to test the $\mu$-$\tau$ breaking models in the near future experiments. We also propose a concrete model to break the $\mu$-$\tau$ exchange symmetry spontaneously and its breaking is mediated by the gauge interactions radiatively in the framework of the extended gauge model with $B-L$ and $L_{\mu }-L_{\tau }$ symmetries. As a result of the gauge mediated $\mu$-$\tau$ breaking in the neutrino mass matrix, the artificial choice is unlikely, and a large Dirac CP phase is preferable.

   hep-phPRD(2020)·6 citations
5. 05*

   Electromagnetic and weak probes: theory

   Ralf-Arno Tripolt🇩🇪

   An overview of the latest theoretical developments and results on electromagnetic and weak probes in relativistic heavy-ion collisions is presented. The possibilities to use electromagnetic probes, i.e., photons and dileptons, as a spectrometer, thermometer, chronometer, polarimeter, barometer, and multimeter of the collision system, as well as to explore the QCD phase diagram and to locate phase transitions such as the critical endpoint, are discussed.

   hep-phnucl-thNPA(2021)·10 citations
6. 06*

   Symmetric point flavour singlet axial vector current renormalization at two loops

   J.A. Gracey🇬🇧

   We calculate the two loop correction to the quark 2-point function with the non-zero momentum insertion of the flavour singlet axial vector current at the fully symmetric subtraction point for massless quarks in the modified minimal subtraction (MSbar) scheme. The Larin method is used to handle ${\gamma }^5$ within dimensional regularization at this loop order ensuring that the effect of the chiral anomaly is properly included within the construction.

   hep-phhep-latPRD(2020)·4 citations
7. 07*

   Linking the pseudo-Dirac dark matter and radiative neutrino mass in a singlet doublet scenario

   Partha Konar🇮🇳 · Ananya Mukherjee🇮🇳 · Abhijit Kumar Saha🇮🇳 · Sudipta Show🇮🇳

   We examine simple extension of the standard model with a pair of fermions, one singlet and a doublet, in a common thread linking the dark matter problem with the smallness of neutrino masses associated with several exciting features. In the presence of a small bare Majorana mass term, the singlet fermion brings in a pseudo-Dirac dark matter capable of evading the strong spin-independent direct detection bound by suppressing the dark matter annihilation processes mediated by the neutral current. In consequence, the allowed range of mixing angle between the doublet and the singlet fermions gets enhanced substantially. Presence of the same mass term in association of singlet scalars also elevates tiny but nonzero masses radiatively for light Majorana neutrino satisfying observed oscillation data.

   hep-phPRD(2020)·29 citations
8. 08*

   An $n$-point QCD two-loop amplitude

   David C. Dunbar🇬🇧 · Warren B. Perkins🇬🇧 · Joseph M.W. Strong🇬🇧

   We present an explicit expression for a particular $n$-gluon two loop scattering partial amplitude. Specifically we present an analytic form for the single trace $N_c$ independent colour partial amplitude for the case where all external gluons have positive helicity.

   hep-phhep-thPRD(2020)·22 citations
9. 09*

   Resummed Drell-Yan cross-section at N${}^3$LL

   Ajjath A. H.🇮🇳 · Goutam Das🇩🇪 · M. C. Kumar🇮🇳 · Pooja Mukherjee🇮🇳 · V. Ravindran🇮🇳 · Kajal Samanta🇮🇳

   We present the resummed predictions for inclusive cross-section for Drell-Yan (DY) production as well as onshell $Z,W^{\pm }$ productions at next-to-next-to-next-to leading logarithmic (N${}^3$LL) accuracy. Using the standard techniques, we derive the $N$-dependent coefficients in the Mellin-$N$ space as well as the $N$-independent constants and match the resummed result through the minimal prescription matching procedure with that of existing next-to next-to leading order (NNLO). In addition to the standard $\ln N$ exponentiation, we study the numerical impacts of exponentiating $N$-independent part of the soft function and the complete ${\bar{g}}_0$ that appears in the resummed predictions in $N$ space. All the analytical pieces needed in these different approaches are extracted from the soft-virtual part of the inclusive cross section known to next-to-next-to-next-to leading order (N${}^3$LO). We perform a detailed analysis on the scale and parton distribution function (PDF) variations and present predictions for the 13 TeV LHC for the neutral Drell-Yan process as well as onshell charged and neutral vector boson productions.

   hep-phJHEP(2020)·48 citations
10. 10*

    Rational Terms of UV Origin at Two Loops

    Stefano Pozzorini🇨🇭 · Hantian Zhang🇨🇭 · Max F. Zoller🇨🇭

    The advent of efficient numerical algorithms for the construction of one-loop amplitudes has played a crucial role in the automation of NLO calculations, and the development of similar algorithms at two loops is a natural strategy for NNLO automation. Within a numerical framework the numerator of loop integrals is usually constructed in four dimensions, and the missing rational terms, which arise from the interplay of the $(D-4)$-dimensional parts of the loop numerator with $1/(D-4)$ poles in $D$ dimensions, are reconstructed separately. At one loop, such rational terms arise only from UV divergences and can be restored through process-independent local counterterms. In this paper we investigate the behaviour of rational terms of UV origin at two loops. The main result is a general formula that combines the subtraction of UV poles with the reconstruction of the associated rational parts at two loops. This formula has the same structure as the R-operation, and all poles and rational parts are described through a finite set of process-independent local counterterms. We also present a general formula for the calculation of all relevant two-loop rational counterterms in any renormalisable theory based on one-scale tadpole integrals. As a first application, we derive the full set of two-loop rational counterterms for QED in the $R_{\xi }$-gauge.

    hep-phhep-thJHEP(2020)·29 citations
11. 11*

    Numerical resummation at subleading color in the strongly ordered soft gluon limit

    Stefan Hoeche🇺🇸 · Daniel Reichelt🇩🇪

    We present a Monte Carlo approach to soft-gluon resummation at subleading color which can be used to improve existing parton shower algorithms. At the single-emission level, soft-collinear enhancements of the splitting functions are explicitly linked to quadratic Casimir operators, while wide angle single-soft enhancements are connected to nontrivial color correlators. We focus on a numerically stable implementation of color matrix element corrections to all orders and approximate the virtual corrections by requiring unitarity at the single-emission level. We provide a proof-of-concept implementation to compute nonglobal event shapes at lepton colliders.

    hep-phPRD(2021)·41 citations
12. 12*

    A little theory of everything, with heavy neutral leptons

    James M. Cline🇨🇦 · Matteo Puel🇨🇦 · Takashi Toma🇨🇦

    Recently a new model of "Affleck-Dine inflation" was presented, that produces the baryon asymmetry from a complex inflaton carrying baryon number, while being consistent with constraints from the cosmic microwave background. We adapt this model such that the inflaton carries lepton number, and communicates the lepton asymmetry to the standard model baryons via quasi-Dirac heavy neutral leptons (HNLs) and sphalerons. One of these HNLs, with mass $\lesssim 4.5$GeV, can be (partially) asymmetric dark matter (DM), whose asymmetry is determined by that of the baryons. Its stability is directly related to the vanishing of the lightest neutrino mass. Neutrino masses are generated by integrating out heavy sterile neutrinos whose mass is above the inflation scale. The model provides an economical origin for all of the major ingredients missing from the standard model: inflation, baryogenesis, neutrino masses, and dark matter. The HNLs can be probed in fixed-target experiments like SHiP, possibly manifesting $N$-$\bar{N}$ oscillations. A light singlet scalar, needed for depleting the DM symmetric component, can be discovered in beam dump experiments and searches for rare decays, possibly explaining anomalous events recently observed by the KOTO collaboration. The DM HNL is strongly constrained by direct searches, and could have a cosmologically interesting self-interaction cross section.

    hep-phastro-ph.COJHEP(2020)·51 citations
13. 13*

    Self Destructing Atomic DM

    Michael Geller🇮🇱 · Ofri Telem🇺🇸

    Self-Destructing Dark Matter (SDDM) is a class of dark sector models in which the collision of a dark sector particle with the earth induces its prompt decay into Standard Model particles, generating unique signals at neutrino detectors. The inherent fragility of SDDM makes its survival from the early universe unlikely, implying a late time production mechanism. We present an efficient late time production mechanism for SDDM based on atomic rearrangement, the mechanism responsible for muon or anti-proton capture in hydrogen. In this model, an atomic rearrangement process occurs in our galaxy, converting dark atoms into highly excited bound states - our SDDM candidates. While the resulting SDDM is only a small fraction of the dark matter flux, its striking self-destruction signals imply a significant discovery reach in the existing data from the Super-Kamiokande experiment.

    hep-phhep-exPRD(2021)·10 citations
14. 14*

    Computing real time correlation functions on a hybrid classical/quantum computer

    Niklas Mueller🇺🇸 · Andrey Tarasov🇺🇸 · Raju Venugopalan🇺🇸

    Quantum devices may overcome limitations of classical computers in studies of nuclear structure functions and parton Wigner distributions of protons and nuclei. In this talk, we discuss a worldline approach to compute nuclear structure functions in the high energy Regge limit of QCD using a hybrid quantum computer, by expressing the fermion determinant in the QCD path integral as a quantum mechanical path integral over $0+1$-dimensional fermionic and bosonic world-lines in background gauge fields. Our simplest example of computing the well-known dipole model result for the structure function $F_2$ in the high energy Regge limit is feasible with NISQ era technology using few qubits and shallow circuits. This example can be scaled up in complexity and extended in scope to compute structure functions, scattering amplitudes and other real-time correlation functions in QCD, relevant for example to describe non-equilibrium transport of quarks and gluons in a Quark-Gluon-Plasma.

    ↳ hep-thhep-phnucl-thquant-phNPA(2021)·10 citations
15. 15*

    Updated constraints on superconducting cosmic strings from the astronomy of fast radio bursts

    Batool Imtiaz🇨🇳 · Rui Shi🇨🇳 · Yi-Fu Cai🇨🇳

    In this article we update constraints on superconducting cosmic strings (SCSs) in light of the recent observational developments of fast radio bursts (FRBs) astronomy. Assuming strings follow an exponential distribution characterized by current, we show that two parameters in our context, which are the characteristic tension ($G\mu$) and a parameter which describes the aforementioned exponential distribution ($I_c$), can be constrained by FRB experiments. Particularly, we investigate data sets from Parkes and ASKAP. We looked through a parameter space where $G\mu \sim [10^{-17},10^{-12}]$ and $I_c\sim [10^{-1},10^2]$ GeV, and found our results show that Parkes jointly with ASKAP can constrain the parameter space for SCSs.

    ↳ astro-ph.HEgr-qchep-phhep-thEPJC(2020)·10 citations
16. 16*

    Hints of dark energy anisotropic stress using Machine Learning

    Rubén Arjona🇪🇸 · Savvas Nesseris🇪🇸

    Recent analyses of the Planck data and quasars at high redshifts have suggested possible deviations from the flat $\Lambda$ cold dark matter model ($\Lambda$CDM), where $\Lambda$ is the cosmological constant. Here we use machine learning methods to investigate any possible deviations from $\Lambda$CDM at both low and high redshifts by using the latest cosmological data. Specifically, we apply the Genetic Algorithms to explore the nature of dark energy (DE) in a model independent fashion by reconstructing its equation of state $w(z)$, the growth index of matter density perturbations $\gamma (z)$, the linear DE anisotropic stress ${\eta }_{\text{DE}}(z)$ and the adiabatic sound speed $c_{\text{s,DE}}^2(z)$ of DE perturbations. We find a $\sim 2\sigma$ deviation of $w(z)$ from -1 at high redshifts, the adiabatic sound speed is negative at the $\sim 2.5\sigma$ level at $z=0.1$ and a $\sim 2\sigma$ deviation of the anisotropic stress from unity at low redshifts and $\sim 4\sigma$ at high redshifts. These results hint towards either the presence of an non-adiabatic component in the DE sound speed or the presence of DE anisotropic stress, thus hinting at possible deviations from the $\Lambda$CDM model.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·58 citations
17. 17*

    Constraining galactic structures of mirror dark matter

    Jean-Samuel Roux🇨🇦 · James M. Cline🇨🇦

    The simplest model of mirror sector dark matter maintains exact mirror symmetry, but has a baryon abundance ${\Omega }_{b^{\prime }}=\beta {\Omega }_b$ and a suppressed temperature $T^{\prime }=xT$ in the mirror sector; hence it depends only on two parameters, $\beta ,x$. For sufficiently small $x$, early cosmological observables may not constrain mirror baryons from constituting all of the dark matter despite their strong self-interactions, depending on the unknown details of structure formation in the hidden sector. Here we close this loophole by simulating mirror structure formation, mapping out the allowed regions of parameter space using cosmological and astronomical data. We find that the Milky Way disk surface density and bulge mass constrain ${\Omega }_{b^{\prime }}\lesssim 0.3{\Omega }_b$ at the highest $T^{\prime }$ allowed by BBN and CMB ($T^{\prime }=0.5T$), or ${\Omega }_{b^{\prime }}\lesssim 0.8{\Omega }_b$ at lower values of $T^{\prime }$. We also briefly discuss the realization of the necessary temperature asymmetry between the SM and the mirror sector in our model with unbroken mirror symmetry.

    ↳ astro-ph.COastro-ph.GAhep-phPRD(2020)·29 citations
18. 18*

    Analytical investigations on formations of hairy neutral reflecting shells in the scalar-Gauss-Bonnet gravity

    Yan Peng🇨🇳

    We study scalarization of spherically symmetric neutral reflecting shells in the scalar-tensor gravity. We consider neutral static massless scalar fields non-minimally coupled to the Gauss-Bonnet invariant. We obtain a relation representing the existence regime of hairy neutral reflecting shells. For parameters unsatisfying this relation, the massless scalar field cannot exist outside the neutral reflecting shell. In the parameter region where this relation holds, we get analytical solutions of scalar field hairs outside neutral reflecting shells.

    ↳ gr-qchep-phhep-thEPJC(2020)·9 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.