Thu·Jun 4, 2020Thursday·June 4, 2020

1. 01*

   Electron and muon $g-2$ anomalies in general flavour conserving two Higgs doublets models

   Francisco J. Botella🇪🇸 · Fernando Cornet-Gomez (Valencia U. and IFIC)🇪🇸 · Miguel Nebot (Lisbon IST and CFTP)🇵🇹

   In general two Higgs doublet models (2HDMs) without scalar flavour changing neutral couplings (SFCNC) in the lepton sector, the electron, muon and tau interactions can be decoupled in a robust framework, stable under renormalization group evolution. In this framework, the breaking of lepton flavour universality (LFU) goes beyond the mass proportionality, opening the possibility to accommodate a different behaviour among charged leptons. We analyze the electron and muon $(g-2)$ anomalies in the context of these general flavour conserving models in the leptonic sector (g$\ell$FC). We consider two different models, I-g$\ell$FC and II-g$\ell$FC, in which the quark Yukawa couplings coincide, respectively, with the ones in type I and in type II 2HDMs. We find two types of solutions that fully reproduce both $(g-2)$ anomalies, and which are compatible with experimental constraints from LEP and LHC, from LFU, from flavour and electroweak physics, and with theoretical constraints in the scalar sector. In the first type of solution, all the new scalars have masses in the 1--2.5 TeV range, the vacuum expectation values (vevs) of both doublets are quite similar in magnitude, and both anomalies are dominated by two loop Barr-Zee contributions. This solution appears in both models. In a second type of solution, one loop contributions are dominant in the muon anomaly, all new scalars have masses below 1 TeV, and the ratio of vevs is in the range 10--100. The second neutral scalar $H$ is the lighter among the new scalars, with a mass in the 210--390 GeV range while the pseudoscalar $A$ is the heavier, with a mass in the range 400--900 GeV. The new charged scalar $H^{\pm }$ is almost degenerate either with the scalar or with the pseudoscalar. This second type of solution only appears in the I-g$\ell$FC model. Both solutions require the soft breaking of the ${\mathbb{Z}}_2$ symmetry of the Higgs potential.

   hep-phhep-exPRD(2020)·62 citations
2. 02*

   Understanding the MiniBooNE and the muon and electron $g-2$ anomalies with a light $Z^{\prime }$ and a second Higgs doublet

   Waleed Abdallah🇮🇳 · Raj Gandhi🇮🇳 · Samiran Roy🇮🇳

   Two of the most widely studied extensions of the Standard Model (SM) are $a)$ the addition of a new $U(1)$ symmetry to its existing gauge groups, and $b)$ the expansion of its scalar sector to incorporate a second Higgs doublet. We show that when combined, they allow us to understand the electron-like event excess seen in the MiniBooNE (MB) experiment as well as account for the observed anomalous values of the muon magnetic moment. A light $Z^{\prime }$ associated with an additional $U(1)$ coupled to baryons and to the dark sector, with flavor non-universal couplings to leptons, in conjunction with a second Higgs doublet is capable of explaining the MB excess. The $Z^{\prime }$ obtains its mass from a dark singlet scalar, which mixes with the two Higgs doublets. Choosing benchmark parameter values, we show that $U(1{)}_{B-3L_{\tau }}$, which is anomaly-free, and $U(1{)}_B$, both provide (phenomenologically) equally good solutions to the excess. We also point out the other (anomaly-free) $U(1)$ choices that may be possible upon fuller exploration of the parameter space. We obtain very good matches to the energy and angular distributions for neutrinos and anti-neutrinos in MB. The extended Higgs sector has two light CP-even scalars, $h^{\prime }$ and $H$, and their masses and couplings are such that in principle, both contribute to help explain the MB excess as well as the present observed values of the muon and electron $g-2$. We discuss the constraints on our model as well as future tests. Our work underlines the role that light scalars may play in understanding present-day low-energy anomalies. It also points to the possible existence of portals to the dark sector, i.e., a light gauge boson field $(Z^{\prime })$ and a dark neutrino which mixes with the active neutrinos, as well as a dark sector light scalar which mixes with the extended Higgs sector.

   hep-phhep-exJHEP(2020)·62 citations
3. 03*

   A connection between flavour anomaly, neutrino mass, and axion

   Seungwon Baek🇰🇷

   We propose a minimal model in which the flavour anomaly in the $b\to s{\mu }^{+}{\mu }^{-}$ transition is connected to the breaking of Peccei-Quinn (PQ) symmetry. The flavour anomaly is explained from new physics contribution by introducing one generation of heavy quark and heavy lepton which are vector-like under the standard model (SM) gauge group but charged under a local $U(1{)}_X$ group. They mix with the SM quarks and leptons, inducing flavour-changing $Z^{\prime }$ couplings, which generates the $b\to s{\mu }^{+}{\mu }^{-}$ anomaly at tree level. On the other hand the new fermions are chiral under the global Peccei-Quinn(PQ) symmetry. The pseudo-Goldstone boson coming from the spontaneous breaking of the PQ symmetry becomes an axion, solving the strong CP problem and providing a cold dark matter candidate. The same symmetry prevents the right-handed neutrino from having a Majorana mass term. But the introduction of a neutrino-specific Higgs doublet allows neutrino to have Dirac mass term without fine-tuning problem. The model shows an interplay between axion, neutrino, dark matter, and flavour physics.

   hep-phJHEP(2020)·10 citations
4. 04*

   Inhomogeneous phases in the quark-meson model with explicit chiral-symmetry breaking

   Michael Buballa🇩🇪 · Stefano Carignano🇪🇸 · Lennart Kurth🇩🇪

   We investigate the existence of inhomogeneous chiral phases in the quark-meson model with explicit chiral-symmetry breaking. We find that the inhomogeneous region shrinks with increasing pion masses but survives for the physical value of m_pi. The instability towards inhomogeneous matter occurs in the scalar channel, while pseudoscalar modes are disfavored.

   hep-phnucl-thEur.Phys.J.ST(2020)·26 citations
5. 05*

   Fermion pair production at $e^{-}{e}^{+}$ linear collider experiments in GUT inspired gauge-Higgs unification

   Shuichiro Funatsu🇨🇳 · Hisaki Hatanaka🇯🇵 · Yutaka Hosotani🇯🇵 · Yuta Orikasa🇨🇿 · Naoki Yamatsu🇯🇵

   Fermion pair production at $e^{-}{e}^{+}$ linear collider experiments with polarized $e^{-}$ and $e^{+}$ beams is examined in the GUT inspired $SO(5)\times U(1)\times SU(3)$ gauge-Higgs unification. There arises large parity violation in the couplings of leptons and quarks to Kaluza-Klein (KK) excited neutral vector bosons $Z^{\prime }$s, which leads to distinctive polarization dependence in cross sections, forward-backward asymmetries, left-right asymmetries, and left-right forward-backward asymmetries in various processes. Those effects are detectable even for the KK mass scale up to about 15 TeV at future $e^{-}{e}^{+}$ linear collider experiments with energies 250GeV to 1TeV.

   hep-phPRD(2020)·27 citations
6. 06*

   Probing heavy scalars with an effective $Hb\bar{b}g$ coupling at the LHC

   Katri Huitu🇫🇮 · Subhadeep Mondal🇫🇮 · Biswarup Mukhopadhyaya🇮🇳

   We have explored the prospect of probing a neutral scalar ($H$) produced in association with one $b$-quark and decaying either invisibly or into a pair of $b$-quarks at the LHC with centre of mass energy $\sqrt{s}=14$ TeV. In this regard, we adopt an effective theory approach to parameterize a $Hb\bar{b}g$ vertex arising from a dimension six operator that encompasses the effect of some new physics setting in at a high scale. We concentrate solely on the five-flavor scheme to ascertain the sensitivity of the 14 TeV LHC in probing such an effective coupling as a function of the scalar mass at the highest possible projected luminosity, $3000{\mathrm{fb}}^{-1}$. Through our multivariate analysis using machine learning algorithm we show that staying within the perturbative limit of the Wilson coefficient of the effective interaction, evidence with statistical significance of $3\sigma$ can be obtained in two different signal regions for $m_H\lesssim 2$ TeV and the scale of new physics $\Lambda =3$ TeV.

   hep-ph0 citations
7. 07*

   Gravitational reheating and superheavy Dark Matter creation after inflation with non-minimal coupling

   E. Babichev🇫🇷 · D. Gorbunov🇷🇺 · S. Ramazanov🇨🇿 · L. Reverberi🇨🇿

   We discuss the gravitational creation of superheavy particles $\chi$ in an inflationary scenario with a quartic potential and a non-minimal coupling between the inflaton $\phi$ and the Ricci curvature: $\xi {\phi }^{2}R/2$. We show that for large constants $\xi >>1$, there can be abundant production of particles $\chi$ with masses largely exceeding the inflationary Hubble rate $H_{infl}$, up to $(afew)\times \xi H_{infl}$, even if they are conformally coupled to gravity. We discuss two scenarios involving these gravitationally produced particles $\chi$. In the first scenario, the inflaton has only gravitational interactions with the matter sector and the particles $\chi$ reheat the Universe. In this picture, the inflaton decays only due to the cosmic expansion, and effectively contributes to dark radiation, which can be of the observable size. The existing limits on dark radiation lead to an upper bound on the reheating temperature. In the second scenario, the particles $\chi$ constitute Dark Matter, if substantially stable. In this case, their typical masses should be in the ballpark of the Grand Unification scale.

   hep-phastro-ph.COhep-thJCAP(2020)·28 citations
8. 08*

   Pion observables calculated in Minkowski and Euclidean spaces with Ansätze for quark propagators

   Dalibor Kekez🇭🇷 · Dubravko Klabučar🇭🇷

   We study two quark--propagator meromorphic Ansätze that admit clear connection between calculations in Euclidean space and Minkowski spacetime. The connection is established through a modified Wick rotation in momentum space, where the integration contour along the imaginary axis is adequately deformed. The Ansätze were previously proposed in the literature and fitted to Euclidean lattice QCD data. The generalized impulse approximation is used to calculate the pion transition form factor and electromagnetic form factor, correcting an earlier result. The pion decay constant and distribution amplitude are also calculated. The latter is used to deduce the asymptotic behavior of the form factors. Such an asymptotic behavior is compared with those obtained directly from the generalized impulse approximation and the causes of differences are pointed out.

   hep-phnucl-thPRD(2023)·5 citations
9. 09*

   The strange critical endpoint and isentropic trajectories in an Extended PNJL Model with Eight Quark Interactions

   Renan Câmara Pereira🇵🇹 · João Moreira🇵🇹 · Pedro Costa🇵🇹

   In this work, we explore the possible existence of several critical endpoints in the phase diagram of strongly interacting matter using an extended PNJL model with 't Hooft determinant and eight quark interactions in the up, down and strange sectors. Besides, we also study the isentropic trajectories crossing both (light and strange) chiral phase transitions and around the critical endpoint in both the crossover and first-order transition regions.

   hep-phEPJA(2020)·12 citations
10. 10*

    Transverse-Energy-Energy Correlations in Deep Inelastic Scattering

    Hai Tao Li🇺🇸 · Ivan Vitev🇺🇸 · Yu Jiao Zhu🇨🇳

    Event shape observables have been widely used for precision QCD studies at various lepton and hadron colliders. We present the most accurate calculation of the transverse-energy-energy correlation event shape variable in deep-inelastic scattering. In the framework of soft-collinear effective theory the cross section is factorized as the convolution of the hard function, beam function, jet function and soft function in the back-to-back limit. A close connection to TMD factorization is established, as the beam function when combined with part of the soft function is identical to the conventional TMD parton distribution function, and the jet function is the second moment of the TMD fragmentation function matching coefficient. We validate our framework by comparing the obtained LO and NLO leading singular distributions to the full QCD calculations in the back-to-back limit. We report the resummed transverse-energy-energy correlation distributions up to N${}^3$LL accuracy matched with the NLO cross section for the production of a lepton and two jets. Our work provides a new way to precisely study TMD physics at the future Electron-Ion Collider.

    hep-phhep-exJHEP(2020)·63 citations
11. 11*

    UV Freeze-in in Starobinsky Inflation

    Nicolás Bernal🇨🇴 · Javier Rubio🇫🇮 · Hardi Veermäe🇪🇪

    In the Starobinsky model of inflation, the observed dark matter abundance can be produced from the direct decay of the inflaton field only in a very narrow spectrum of close-to-conformal scalar fields and spinors of mass $\sim 10^7$ GeV. This spectrum can be, however, significantly broadened in the presence of effective non-renormalizable interactions between the dark and the visible sectors. In particular, we show that UV freeze-in can efficiently generate the right dark matter abundance for a large range of masses spanning from the keV to the PeV scale and arbitrary spin, without significantly altering the heating dynamics. We also consider the contribution of effective interactions to the inflaton decay into dark matter.

    hep-phastro-ph.COgr-qcJCAP(2020)·68 citations
12. 12*

    Thermal, Trapped and Chromo-Natural Inflation in light of the Swampland Criteria and the Trans-Planckian Censorship Conjecture

    Arjun Berera🇬🇧 · Robert Brandenberger🇨🇦 · Vahid Kamali🇨🇦 · Rudnei Ramos🇧🇷

    We consider thermal, trapped and chromo-natural inflation in light of the swampland criteria and the Trans-Planckian Censorship Conjecture (TCC). Since thermal inflation occurs at energies low compared to those of Grand Unification, it is consistent with the TCC, and it is also consistent with the refined swampland conditions. Trapped and chromo-natural inflation are candidates for primordial (high energy scale) inflation. Since in both of these scenarios there are effective damping terms in the scalar field equation of motion, the models can easily be consistent with the swampland criteria. The TCC, on the other hand, constrains these scenarios to only take place at low energies.

    ↳ hep-thastro-ph.COgr-qchep-phEPJC(2021)·14 citations
13. 13*

    The High-Temperature Expansion of the Thermal Sunset

    Andreas Ekstedt🇨🇿 · Johan Löfgren🇸🇪

    We give a prescription for calculating the high-temperature expansion of the thermal sunset integral to arbitrary order. We derive all terms odd in $T$, and rederive previous results up to $\mathcal{O}(T^0)$ for both bosonic and fermionic thermal sunsets in dimensional regularisation. We perform analytical and numerical cross-checks. Intermediate steps involve integrals over three Bessel functions.

    ↳ hep-thhep-phSciPost Phys. Core 3, 008 (2020)·6 citations
14. 14*

    Pre-hydrodynamic evolution and its signatures in final-state heavy-ion observables

    Tiago Nunes da Silva🇧🇷 · David Chinellato🇧🇷 · Mauricio Hippert🇧🇷 · Willian Serenone🇧🇷 · Jun Takahashi🇧🇷 · Gabriel S. Denicol🇧🇷 · Matthew Luzum🇧🇷 · Jorge Noronha🇺🇸

    We investigate the effects of pre-hydrodynamic evolution on final-state observables in heavy-ion collisions using state-of-the art event simulations coupled to different pre-hydrodynamic scenarios, which include the recently-developed effective kinetic transport theory evolution model KoMPoST. Flow observables are found to be insensitive to the details of pre-hydrodynamic evolution. The main effect we observe is in the $p_T$ spectra, particularly the mean transverse momentum. However, at least part of this effect is a consequence of the underlying conformal invariance assumption currently present in such approaches, which is known to be violated in the temperature regime probed in heavy-ion collisions. This assumption of early time conformal invariance leads to an artificially large out-of-equilibrium bulk pressure when switching from (conformal) pre-hydrodynamic evolution to hydrodynamics (using the non-conformal QCD equation of state), which in turn increases the transverse momentum. Our study indicates that a consistent treatment of pre-hydrodynamic evolution in heavy-ion collisions requires the use of non-conformal models of early time dynamics.

    ↳ nucl-thhep-phnucl-exPRC(2021)·45 citations
15. 15*

    Density Matrix Formalism for PT-Symmetric Non-Hermitian Hamiltonians with the Lindblad Equation

    Tommy Ohlsson🇸🇪 · Shun Zhou🇨🇳

    In the presence of Lindblad decoherence, i.e. dissipative effects in an open quantum system due to interaction with an environment, we examine the transition probabilities between the eigenstates in the two-level quantum system described by non-Hermitian Hamiltonians with the Lindblad equation, for which the parity-time-reversal (PT) symmetry is conserved. First, the density matrix formalism for PT-symmetric non-Hermitian Hamiltonian systems is developed. It is shown that the Lindblad operators $L_j^{}$ are pseudo-Hermitian, namely, $\eta L_j^{}{\eta }^{-1}=L_j^{†}$ with $\eta$ being a linear and positive-definite metric, and respect the PT symmetry as well. We demonstrate that the generalized density matrix ${\rho }_{\mathrm{G}}^{}(t)\equiv \rho (t)\eta$, instead of the normalized density matrix ${\rho }_{\mathrm{N}}^{}(t)\equiv \rho (t)/\mathrm{tr}\left[\rho (t)\right]$, should be implemented for the calculation of the transition probabilities in accordance with the linearity requirement. Second, the density matrix formalism is used to derive the transition probabilities in general cases of PT-symmetric non-Hermitian Hamiltonians. In some concrete examples, we calculate compact analytical formulas for the transition probabilities and explore their main features with numerical illustrations. We also make a comparison between our present results and our previous ones using state vectors in the absence of Lindblad decoherence.

    ↳ quant-phhep-phhep-thmath-ph+1PRA(2021)·34 citations
16. 16*

    Upper bounds on the compactness at the innermost light ring of anisotropic horizonless spheres

    Yan Peng🇨🇳

    In the background of isotropic horizonless spheres, Hod recently provided an analytical proof of a bound on the compactness at the innermost light ring with the dominant energy and non-negative trace conditions. In this work, we extend the discussion of isotropic spheres to anisotropic spheres. With the same dominant energy and non-negative trace conditions, we prove that Hod's bound also holds in the case of anisotropic horizonless spheres.

    ↳ gr-qchep-phhep-thEPJC(2020)·8 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.