Mon·Feb 15, 2021Monday·February 15, 2021

1. 01*

   Displaced new physics at colliders and the early universe before its first second

   Lorenzo Calibbi🇨🇳 · Francesco D'Eramo🇮🇹 · Sam Junius🇧🇪 · Laura Lopez-Honorez🇧🇪 · Alberto Mariotti🇧🇪

   Displaced vertices at colliders, arising from the production and decay of long-lived particles, probe dark matter candidates produced via freeze-in. If one assumes a standard cosmological history, these decays happen inside the detector only if the dark matter is very light because of the relic density constraint. Here, we argue how displaced events could very well point to freeze-in within a non-standard early universe history. Focusing on the cosmology of inflationary reheating, we explore the interplay between the reheating temperature and collider signatures for minimal freeze-in scenarios. Observing displaced events at the LHC would allow to set an upper bound on the reheating temperature and, in general, to gather indirect information on the early history of the universe.

   hep-phastro-ph.COhep-exJHEP(2021)·48 citations
2. 02*

   Resolving a challenging supersymmetric low-scale seesaw scenario at the ILC

   J. Masias🇵🇪 · N. Cerna-Velazco🇵🇪 · J. Jones-Perez🇵🇪 · W. Porod🇩🇪

   We investigate a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. For this the Minimal Supersymmetric Standard Model is extended by adding light right-handed neutrinos and their superpartners, the R-sneutrinos. Moreover, we consider the lightest neutralinos to be Higgsino-like. We first update a previous analysis and assess to which extent does existing LHC data constrain the allowed slepton masses. Here we find scenarios where sleptons with masses as low as 175 GeV are consistent with existing data. However, we also show that the upcoming run will either discover or rule out sleptons with masses of 300 GeV, even for these challenging scenarios. We then take a scenario which is on the borderline of observability of the upcoming LHC run assuming a luminosity of 300 fb${}^{-1}$. We demonstrate that a prospective international $e^{+}{e}^{-}$ linear collider with a center of mass energy of 1 TeV will be able to discover sleptons in scenarios which are difficult for the LHC. Moreover, we also show that a measurement of the spectrum will be possible within 1-3 percent accuracy.

   hep-phPRD(2021)·3 citations
3. 03*

   Rare Kaon Decay to Missing Energy: Implications of the NA62 Result for a $Z^{\prime }$ Model

   Téssio B. de Melo🇧🇷 · Sergey Kovalenko🇨🇱 · Farinaldo S. Queiroz🇧🇷 · C. Siqueira🇧🇷 · Yoxara S. Villamizar🇧🇷

   Meson decays offer a good opportunity to probe new physics. The rare kaon decay $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ is one of the cleanest of them and, for this reason, is rather sensitive to new physics, in particular, vector mediators. NA62 collaboration, running a fixed-target experiment at CERN, recently reported an unprecedented sensitivity to this decay, namely a branching fraction of $BR(K^{+}\to {\pi }^{+}\nu \bar{\nu })=(11_{-3.5}^{+4.0})\times 10^{-11}$ at 68\% C.L. Vector mediators that couple to neutrinos may yield a sizeable contribution to this decay. Motivated by the new measurement, we interpret this result in the context of a concrete $Z^{\prime }$ model, and put our findings into perspective with the correlated $K_L\to {\pi }^0\nu \bar{\nu }$ decay measured by KOTO collaboration, current, and future colliders, namely the High-Luminosity and High-Energy LHC.

   hep-phPRD(2021)·8 citations
4. 04*

   Chiral magnetic effect reveals the topology of gauge fields in heavy-ion collisions

   Dmitri E. Kharzeev🇺🇸 · Jinfeng Liao🇺🇸

   The topological structure of vacuum is the cornerstone of non-Abelian gauge theories describing strong and electroweak interactions within the standard model of particle physics. However, transitions between different topological sectors of the vacuum (believed to be at the origin of the baryon asymmetry of the Universe) have never been observed directly. An experimental observation of such transitions in Quantum Chromodynamics (QCD) has become possible in heavy-ion collisions, where the chiral magnetic effect converts the chiral asymmetry (generated by topological transitions in hot QCD matter) into an electric current, under the presence of the magnetic field produced by the colliding ions. The Relativistic Heavy Ion Collider program on heavy-ion collisions such as the Zr-Zr and Ru-Ru isobars, thus has the potential to uncover the topological structure of vacuum in a laboratory experiment. This discovery would have far-reaching implications for the understanding of QCD, the origin of the baryon asymmetry in the present-day Universe, and for other areas, including condensed matter physics.

   hep-phcond-mat.str-elhep-thnucl-ex+1Nature Rev.Phys.(2021)·109 citations
5. 05*

   WKB Electron Wave Functions in a Tightly Focused Laser Beam

   A. Di Piazza🇩🇪

   Available laser technology is opening the possibility of testing QED experimentally in the so-called strong-field regime. This calls for developing theoretical tools to investigate strong-field QED processes in electromagnetic fields of complex spacetime structure. Here, we propose a scheme to compute electron wave functions in tightly focused laser beams by taking into account exactly the complex spacetime structure of the fields. The scheme is solely based on the validity of the Wentzel-Kramers-Brillouin (WKB) approximation and the resulting wave functions, unlike previously proposed ones [Phys. Rev. Lett. \textbf{113}, 040402 (2014)], do not rely on approximations on the classical electron trajectory. Moreover, a consistent procedure is indicated to take into account higher-order quantum effects within the WKB approach depending on higher-and-higher powers of the Planck constant. In the case of a plane-wave background field the found wave functions exactly reduce to the Volkov states, which are then written in a new and fully quasiclassical form. Finally, by using the leading-order WKB wave functions to compute the probabilities of nonlinear Compton scattering and nonlinear Breit-Wheeler pair production, it is explicitly shown that, if additionally the energies of the charges are sufficiently large that the latter are not significantly deflected by the field, the corresponding Baier's formulas are exactly reproduced for an otherwise arbitrary classical electron/positron trajectory.

   hep-phPRD(2021)·25 citations
6. 06*

   CP Symmetry and Symplectic Modular Invariance

   Gui-Jun Ding🇨🇳 · Ferruccio Feruglio🇮🇹 · Xiang-Gan Liu🇨🇳

   We analyze CP symmetry in symplectic modular-invariant supersymmetric theories. We show that for genus $g\ge 3$ the definition of CP is unique, while two independent possibilities are allowed when $g\le 2$. We discuss the transformation properties of moduli, matter multiplets and modular forms in the Siegel upper half plane, as well as in invariant subspaces. We identify CP-conserving surfaces in the fundamental domain of moduli space. We make use of all these elements to build a CP and symplectic invariant model of lepton masses and mixing angles, where known data are well reproduced and observable phases are predicted in terms of a minimum number of parameters.

   hep-phhep-thSciPost Phys.(2021)·69 citations
7. 07*

   The Compton Scattering Total Cross Section at Next-to-Leading Order

   Roman N. Lee🇷🇺 · Matthew D. Schwartz🇺🇸 · Xiaoyuan Zhang🇺🇸

   An analytic formula is given for the total scattering cross section of an electron and a photon at order ${\alpha }^3$. This includes both the double-Compton scattering real-emission contribution as well as the virtual Compton scattering part. When combined with the recent analytic result for the pair-production cross section, the complete ${\alpha }^3$ cross section is now known. Both the next-to-leading order calculation as well as the pair-production cross section are computed using modern multiloop calculation techniques, where cut diagrams are decomposed into a set of master integrals that are then computed using differential equations.

   hep-phPRL(2021)·16 citations
8. 08*

   Lattice Simulations of Inflation

   Angelo Caravano🇩🇪 · Eiichiro Komatsu🇩🇪 · Kaloian D. Lozanov🇺🇸 · Jochen Weller🇩🇪

   The scalar field theory of cosmological inflation constitutes nowadays one of the preferred scenarios for the physics of the early universe. In this paper we aim at studying the inflationary universe making use of a numerical lattice simulation. Various lattice codes have been written in the last decades and have been extensively used for understating the reheating phase of the universe, but they have never been used to study the inflationary phase itself far from the end of inflation (i.e. about 50 e-folds before the end of inflation). In this paper we use a lattice simulation to reproduce the well-known results of some simple models of single-field inflation, particularly for the scalar field perturbation. The main model that we consider is the standard slow-roll inflation with an harmonic potential for the inflaton field. We explore the technical aspects that need to be accounted for in order to reproduce with precision the nearly scale invariant power spectrum of inflaton perturbations. We also consider the case of a step potential, and show that the simulation is able to correctly reproduce the oscillatory features in the power spectrum of this model. Even if a lattice simulation is not needed in these cases, that are well within the regime of validity of linear perturbation theory, this sets the basis to future work on using lattice simulations to study more complicated models of inflation.

   ↳ astro-ph.COgr-qchep-phJCAP(2021)·30 citations
9. 09*

   Gamma-ray image reconstruction of the Andromeda galaxy

   Celine Armand🇫🇷 · Francesca Calore🇫🇷

   We analyze about 12 years of Fermi-LAT data in the direction of the Andromeda galaxy (M31). We robustly characterize its spectral and morphological properties against systematic uncertainties related to the modeling of the Galactic diffuse emission. We perform this work by adapting and exploiting the potential of the skyFACT adaptive template fitting algorithm. We reconstruct the gamma-ray image of M31 in a template-independent way, and we show that flat spatial models are preferred by data, indicating an extension of the $\gamma$-ray emission of about 0.3-0.4 degree for the bulge of M31. This study also suggests that a second component, extending to at least 1 degree, contributes to the observed total emission. We quantify systematic uncertainties related to mis-modeling of Galactic foreground emission at the level of 2.9%.

   ↳ astro-ph.HEhep-phPRD(2021)·9 citations
10. 10*

    Corrections to the hadron resonance gas from lattice QCD and their effect on fluctuation-ratios at finite density

    Rene Bellwied🇺🇸 · Szabolcs Borsanyi🇩🇪 · Zoltan Fodor🇩🇪 · Jana N. Guenther🇫🇷 · Sandor D. Katz🇭🇺 · Paolo Parotto🇩🇪 · Attila Pasztor🇭🇺 · David Pesznyak🇭🇺 · Claudia Ratti🇺🇸 · Kalman K. Szabo🇩🇪

    The hadron resonance gas (HRG) model is often believed to correctly describe the confined phase of QCD. This assumption is the basis of many phenomenological works on QCD thermodynamics and of the analysis of hadron yields in relativistic heavy ion collisions. We use first-principle lattice simulations to calculate corrections to the ideal HRG. Namely, we determine the sub-leading fugacity expansion coefficients of the grand canonical free energy, receiving contributions from processes like kaon-kaon or baryon-baryon scattering. We achieve this goal by performing a two dimensional scan on the imaginary baryon number chemical potential (${\mu }_B$) - strangeness chemical potential (${\mu }_S$) plane, where the fugacity expansion coefficients become Fourier coefficients. We carry out a continuum limit estimation of these coefficients by performing lattice simulations with temporal extents of $N_{\tau }=8,10,12$ using the 4stout-improved staggered action. We then use the truncated fugacity expansion to extrapolate ratios of baryon number and strangeness fluctuations and correlations to finite chemical potentials. Evaluating the fugacity expansion along the crossover line, we reproduce the trend seen in the experimental data on net-proton fluctuations by the STAR collaboration.

    ↳ hep-lathep-phnucl-thPRD(2021)·25 citations
11. 11*

    Near future MeV telescopes can discover asteroid-mass primordial black hole dark matter

    Anupam Ray🇮🇳 · Ranjan Laha🇮🇳 · Julian B. Muñoz🇺🇸 · Regina Caputo🇺🇸

    Primordial black holes (PBHs), formed out of large overdensities in the early Universe, are a viable dark matter (DM) candidate over a broad range of masses. Ultra-light, asteroid-mass PBHs with masses around $10^{17}$ g are particularly interesting as current observations allow them to constitute the entire DM density. PBHs in this mass range emit $\sim$ MeV photons via Hawking radiation which can directly be detected by the gamma ray telescopes, such as the upcoming AMEGO. In this work we forecast how well an instrument with the sensitivity of AMEGO will be able to detect, or rule out, PBHs as a DM candidate, by searching for their evaporating signature when marginalizing over the Galactic and extra-Galactic gamma-ray backgrounds. We find that an instrument with the sensitivity of AMEGO could exclude non-rotating PBHs as the only DM component for masses up to $7\times 10^{17}$ g at 95% confidence level (C.L.) for a monochromatic mass distribution, improving upon current bounds by nearly an order of magnitude. The forecasted constraints are more stringent for PBHs that have rotation, or which follow extended mass distributions.

    ↳ astro-ph.COastro-ph.HEhep-exhep-phPRD(2021)·134 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.