Mon·Jan 11, 2021Monday·January 11, 2021

1. 01*

   Limits on Intrinsic Charm Production from the SeaQuest Experiment

   R. Vogt🇺🇸

   Background: A nonperturbative charm production contribution, known as intrinsic charm, has long been speculated but has never been satisfactorily proven. The SeaQuest experiment at FNAL is in an ideal kinematic region to provide evidence of $J/\psi$ production by intrinsic charm. Purpose: $J/\psi$ production in the SeaQuest kinematics is calculated with a combination of perturbative QCD and intrinsic charm to see whether the SeaQuest data can put limits on an intrinsic charm contribution. Methods: $J/\psi$ production in perturbative QCD is calculated to next-to-leading order in the cross section. Cold nuclear matter effects include nuclear modification of the parton densities, absorption by nucleons, and $p_T$ broadening by multiple scattering. The $J/\psi$ contribution from intrinsic charm is calculated assuming production from a $|uudc\overline{c}⟩$ Fock state. Results: The nuclear modification factor, $R_{pA}$, is calculated as a function of $x_F$ and $p_T$ for $p+$C, $p+$Fe, and $p+$W interactions relative to $p+$d. Conclusions: The SeaQuest kinematic acceptance is ideal for testing the limits on intrinsic charm in the proton.

   hep-phPRC(2021)·35 citations
2. 02*

   Radiative decay of the $\Xi (1620)$ in a hadronic molecule picture

   HongQiang Zhu🇨🇳 · Feng Yang🇨🇳 · Yin Huang🇨🇳

   Last year, the $\Xi (1620)$ state that is cataloged in the Particle Data Group (PDG) with only one star is reported again in the ${\Xi }^{-}{\pi }^{+}$ final state by the Belle Collaboration. Its properties not only the spectroscopy but also the decay width cannot be simply explained in the context of conventional constituent quark models. This intrigues an active discussion on the structure of this resonance. In this work, we study the radiative decays of the newly observed $\Xi (1620)$ assuming that it is a meson-baryon molecular state of $\Lambda \bar{K}$ and $\Sigma \bar{K}$ with spin-parity $J^P=1/2^{-}$ in our previous work. The partial decay widths of the $\Lambda \bar{K}-\Sigma \bar{K}$ molecular state into $\Xi \gamma$ and $\Xi \pi \gamma$ final states through hadronic loops are evaluated with the help of the effective Lagrangians. The partial widths for the $\Xi (1620{)}^0\to \gamma \Xi$ and $\Xi (1620{)}^0\to \gamma \Xi \pi$ are evaluated to be about $118.76-174.21$ KeV and $58.19-68.75$ eV, respectively, which may be accessible for the LHCb. If the $\Xi (1620)$ is $\Lambda \bar{K}-\Sigma \bar{K}$ molecule, the radiative transition strength $\Xi (1620{)}^0\to \gamma \bar{K}\Lambda$ is quite small and the decay width is of the order of 0.01 eV. Future experimental measurements of these processes can be useful to test the molecule interpretations of the $\Xi (1620)$.

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

   Leading Logs in QCD Axion Effective Field Theory

   Gonzalo Alonso-Álvarez🇩🇪 · Fatih Ertas🇩🇪 · Joerg Jaeckel🇩🇪 · Felix Kahlhoefer🇩🇪 · Lennert J. Thormaehlen🇩🇪

   The axion is much lighter than all other degrees of freedom introduced by the Peccei-Quinn mechanism to solve the strong CP problem. It is therefore natural to use an effective field theory (EFT) to describe its interactions. Loop processes calculated in the EFT may, however, explicitly depend on the ultraviolet cutoff. In general the UV cutoff is not uniquely defined, but the dimensionful couplings suggest to identify it with the Peccei-Quinn symmetry-breaking scale. An example are $K\to \pi +a$ decays that will soon be tested to improved precision in NA62 and KOTO and whose amplitude is dominated by the term logarithmically dependent on the cutoff. In this paper, we critically examine the adequacy of using such a naive EFT approach to study loop processes by comparing EFT calculations with ones performed in complete QCD axion models. In DFSZ models, for example, the cutoff is found to be set by additional Higgs degrees of freedom and to therefore be much closer to the electroweak scale than to the Peccei-Quinn scale. In fact, there are non-trivial requirements on axion models where the cutoff scale of loop processes is close to the Peccei-Quinn scale, such that the naive EFT result is reproduced. This suggests that the existence of a suitable UV embedding may impose restrictions on axion EFTs. We provide an explicit construction of a model with suitable fermion couplings and find promising prospects for NA62 and IAXO.

   hep-phhep-thJHEP(2021)·14 citations
4. 04*

   SMEFT analysis of vector boson scattering and diboson data from the LHC Run II

   Jacob J. Ethier🇳🇱 · Raquel Gomez-Ambrosio🇮🇹 · Giacomo Magni🇳🇱 · Juan Rojo🇳🇱

   We present a systematic interpretation of vector boson scattering (VBS) and diboson measurements from the LHC in the framework of the dimension-six Standard Model Effective Field Theory (SMEFT). We consider all available measurements of VBS fiducial cross-sections and differential distributions from ATLAS and CMS, in most cases based on the full Run II luminosity, and use them to constrain 16 independent directions in the dimension-six EFT parameter space. Compared to the diboson measurements, we find that VBS provides complementary information on several of the operators relevant for the description of the electroweak sector. We also quantify the ultimate EFT reach of VBS measurements via dedicated projections for the High Luminosity LHC. Our results motivate the integration of VBS processes in future global SMEFT interpretations of particle physics data.

   hep-phhep-exEPJC(2021)·84 citations
5. 05*

   Cumulants and factorial cumulants in the 3-dimensional Ising universality class

   Xue Pan🇨🇳 · Mingmei Xu🇨🇳 · Yuanfang Wu🇨🇳

   The high-order cumulants and factorial cumulants of conserved charges are suggested to study the critical dynamics in heavy ion collisions. In this paper, using parametric representation of the 3-dimensional Ising model, the sign distribution on the phase diagram and temperature dependence of the cumulants and factorial cumulants is studied and compared. In the vicinity of the critical point, the cumulants and factorial cumulants can not be distinguished. Far away from the critical point, sign changes occur in the factorial cumulants comparing with the same order cumulants. The cause of these sign changes is analysed. They may be used to measure the distance to the critical point.

   ↳ nucl-thhep-phIJMPE(2021)·3 citations
6. 06*

   Anisotropic fluid dynamical simulations of heavy-ion collisions

   M. McNelis🇺🇸 · D. Bazow🇺🇸 · U. Heinz🇺🇸

   We present VAH, a (3+1)-dimensional simulation that evolves the far-from-equilibrium quark-gluon plasma produced in ultrarelativistic heavy-ion collisions with anisotropic fluid dynamics. We solve the hydrodynamic equations on an Eulerian grid using the Kurganov-Tadmor algorithm in combination with a new adaptive Runge-Kutta method. Our numerical scheme allows us to start the simulation soon after the nuclear collision, largely avoiding the need to integrate it with a separate pre-equilibrium dynamics module. We test the code's performance by simulating on the Eulerian grid conformal and non-conformal Bjorken flow as well as conformal Gubser flow, whose (0+1)-dimensional solutions are precisely known. Finally, we compare non-conformal anisotropic hydrodynamics to second-order viscous hydrodynamics in central Pb+Pb collisions and find that the former's longitudinal flow profile responds more consistently to the fluid's gradients along the spacetime rapidity direction.

   ↳ nucl-thhep-phComput.Phys.Commun.(2021)·32 citations
7. 07*

   Learning scattering amplitudes by heart

   Severin Barmeier🇩🇪 · Koushik Ray🇮🇳

   The canonical forms associated to scattering amplitudes of planar Feynman diagrams are interpreted in terms of masses of projectives, defined as the modulus of their central charges, in the hearts of certain $t$-structures of derived categories of quiver representations and, equivalently, in terms of cluster tilting objects of the corresponding cluster categories.

   ↳ hep-thhep-phmath-phmath.MP+2PLB(2021)·1 citation
8. 08*

   The string theory swampland in the Euclid, SKA and Vera Rubin observatory era

   Aurélien Barrau🇫🇷 · Cyril Renevey🇫🇷 · Killian Martineau🇫🇷

   This article aims at drawing the attention of astronomers on the ability of future cosmological surveys to put constraints on string theory. The fact that "quantum gravity" might be constrained by large scale astrophysical observations is a remarkable fact that has recently concentrated a great amount of interest. In this work, we focus on future observatories and investigate their capability to put string theory, which is sometimes said to be "unfalsifiable", under serious pressure. We show that the combined analysis of SKA, Euclid, and the Vera Rubin observatory - together with Planck results - could improve substantially the current limits on the relevant string swampland parameter. In particular, our analysis leads to a nearly model-independent prospective upper bound on the quintessence potential, |V'|/V<0.16, in strong contradiction with the so-called de Sitter conjecture. Some lines of improvements for the very long run are also drawn, together with generic prospective results, underlining the efficiency of this approach. The conjectures used in this work are discussed pedagogically, together with the cosmological models chosen in the analysis.

   ↳ astro-ph.COgr-qchep-phhep-thApJ(2021)·7 citations
9. 09*

   Negative-curvature spacetime solutions for graphene

   Antonio Gallerati🇮🇹

   We provide a detailed analysis of the electronic properties of graphene-like materials with charge carriers living on a curved substrate, focusing in particular on constant negative-curvature spacetime. An explicit parametrization is also worked out in the remarkable case of Beltrami geometry, with an analytic solution for the pseudoparticles modes living on the curved bidimensional surface. We will then exploit the correspondent massless Dirac description, to determine how it affects the sample local density of states.

   ↳ hep-thcond-mat.mes-hallcond-mat.mtrl-scihep-ph+1J.Phys.Condens.Matter(2021)·23 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.