Mon·Nov 18, 2019Monday·November 18, 2019

1. 01*

   Fermion Traces Without Evanescence

   Nikolai Zerf🇩🇪

   We outline the evaluation of $n$-dimensional fermion traces ($n\in \mathbb{N}$) built by products of Dirac-$\gamma$ matrices suitable for a uniform dimensional continuation. Such a continuation is needed for calculations employing a dimensional regulator whenever intrinsically integer dimensional tensors yield non-vanishing contributions. A prime example for such a tensor is given by ${\gamma }_5$ for $n=4$. The main difference between Dimensional Regularization (DREG) and a Dimensionally Continued Regularization (DCREG) is that DCREG does not attempt to lift the algebra to continuous $d$ dimensions ($d\in \mathbb{R}$). As a consequence one has to properly deal with evanescent structures in order to ensure the uniform application of the regulator. In basic steps we identify evanescent structures in fermion traces and show that their proper treatment is crucial for example when calculating the $VVA$ anomaly in four dimensions. We checked that the performed considerations enable the evaluation of Standard Model (SM) $Z$-factors within DCREG up to including three loops.

   hep-phPRD(2020)·21 citations
2. 02*

   Transversity and heavy quark production on hadron colliders

   G.P. Zhang🇨🇳

   The azimuthal asymmetry of heavy quarks production on double polarized proton-proton and proton-antiproton colliders are studied in this work at next-to-leading order in ${\alpha }_s$, with some details included. The purpose is to see whether the effect of extracted transversity distribution functions can be seen on present and near future colliders. All analytic one-loop hard coefficients are given. Numerical results for the asymmetry on proton-(anti)proton colliders are presented.

   hep-phEPJC(2020)·1 citation
3. 03*

   Constraints on the Parameter Space in an Inert Doublet Model with two Active Doublets

   Marco Merchand🇺🇸 · Marc Sher🇺🇸

   We study a three Higgs doublet model where one doublet is inert and the other two doublets are active. Flavor changing neutral currents are avoided at tree-level by imposing a softly broken $Z_2^{\prime }$ symmetry and we consider type I and type II Yukawa structures. The lightest inert scalar is a viable Dark Matter (DM) candidate. A numerical scan of the free parameters is performed taking into account theoretical constraints such as positivity of the scalar potential and unitarity of $2\to 2$ scattering amplitudes. The model is further constrained by experimental results such as $B$ physics lower limits on charged Higgs masses, Electroweak Precision Observables, LEP II, LHC Higgs measurements, Planck measurement of the DM relic abundance and WIMP direct searches by the LUX and XENON1T experiments. The model predictions for mono-jet, mono Z and mono Higgs final states are studied and tested against current LHC data and we find the model to be allowed. We also discuss the effects of abandoning the "dark democracy" assumption common in studies of inert models. Projected sensitivities of direct detection experiments will leave only a tiny window in the DM mass versus coupling plane that is compliant with relic density bounds.

   hep-phJHEP(2020)·20 citations
4. 04*

   Mass matrix parametrization for pseudo-Dirac neutrinos

   A. Gorin🇷🇺

   An overview of pseudo-Dirac neutrino framework is given starting from general spinor phenomenology. The framework is then tested by simulation of oscillations for T2K experiment parameters. Two possible derivations of oscillation parameters are indicated to have the same result.

   hep-ph0 citations
5. 05*

   Role of the $\Lambda (1600)$ in the $K^{-}p\to \Lambda {\pi }^0{\pi }^0$ reaction

   He Zhou🇨🇳 · Ju-Jun Xie🇨🇳

   Role of the $\Lambda (1600)$ is studied in the $K^{-}p\to \Lambda {\pi }^0{\pi }^0$ reaction by using the effective Lagrangian approach near the threshold. We perform a calculation for the total and differential cross sections by considering the contributions from the $\Lambda (1600)$ and $\Lambda (1670)$ intermediate resonances decaying into ${\pi }^0{\Sigma }^{\ast 0}(1385)$ with ${\Sigma }^{\ast 0}(1385)$ decaying into ${\pi }^0\Lambda$. Besides, the non-resonance process from $u$-channel nucleon pole is also taken into account. With our model parameters, the current experimental data on the total cross sections of the $K^{-}p\to \Lambda {\pi }^0{\pi }^0$ reaction can be well reproduced. It is shown that we really need the contribution from the $\Lambda (1600)$ with spin-parity $J^P=1/2^{+}$, and that these measurements can be used to determine some of the properties of the $\Lambda (1600)$ resonance. Furthermore, we also plot the ${\pi }^0\Lambda$ invariant mass distributions which could be tested by the future experimental measurements.

   hep-phhep-exnucl-exnucl-thCommun.Theor.Phys.(2020)·2 citations
6. 06*

   Color Dressed Unitarity and Recursion for Yang-Mills Two-Loop All-Plus Amplitudes

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

   We present a direct computation of the full color two-loop five-point all-plus Yang-Mills amplitude using four dimensional unitarity and recursion. We present the $SU(N_c)$ amplitudes in compact analytic forms. Our results match the explicit expressions previously computed but do not require full two-loop integral methods.

   hep-phPRD(2020)·32 citations
7. 07*

   A complete update of ${\epsilon }^{\prime }/\epsilon$ in the Standard Model

   V. Cirigliano🇺🇸 · H. Gisbert🇩🇪 · A. Pich🇪🇸 · A. Rodríguez-Sánchez🇸🇪

   The recent release of improved lattice data has revived again the interest on precise theoretical calculations of the direct CP-violation ratio ${\epsilon }^{\prime }/\epsilon$. We present a complete update of the Standard Model prediction [1,2], including a new re-analysis of isospin-breaking corrections which are of vital importance in the theoretical determination of this observable. The Standard Model prediction, $\mathrm{Re}({ϵ}^{\prime }/ϵ)=(14\pm 5)\cdot 10^{-4}$, turns out to be in good agreement with the experimental measurement.

   hep-phhep-exhep-latPoS(2020)·7 citations
8. 08*

   Physics with Far Detectors at Future Lepton Colliders

   Zeren Simon Wang🇰🇷 · Kechen Wang🇨🇳

   At the Large Hadron Collider (LHC), several far detectors such as FASER and MATHUSLA have been proposed to target the long-lived particles (LLPs) featured with displaced vertices. Naturally one question arises as to the feasibility of installing similar far detectors at future lepton colliders like the CEPC and FCC-ee. Because of the different kinematics of final state particles and the freedom to locate both the experiment hall and the detectors, the future lepton collider with an additional far detector may play a unique role in searching for LLPs. In this study, we consider various locations and designs of far detectors at future $e^{-}{e}^{+}$ colliders and investigate their potentials for discovering LLPs in the physics scenarios including exotic Higgs decays, heavy neutral leptons, and the lightest neutralinos. Our analyses show that the kinematical distinctions between the lepton and hadron colliders render the optimal positions of far detectors lying at the direction perpendicular to the collider beams at future $e^{-}{e}^{+}$ colliders, in contrast to the LHC where a boost in the forward direction can be exploited. We also find that when searching for LLPs, such new experiments with far detectors at future lepton colliders may extend and complement the sensitivity reaches of the experiments at the future lepton colliders with usual near detectors, and the present and future experiments at the LHC. In particular, we find that, for the theory models considered in this study, a MATHUSLA-sized far detector would give a modest improvement compared to the case with a near detector only at future lepton colliders.

   hep-phhep-exPRD(2020)·46 citations
9. 09*

   Modeling Double Parton Scattering at LHC

   Giulia Pancheri🇮🇹 · Agnes Grau🇪🇸 · Simone Pacetti🇮🇹 · Yogendra N. Srivastava🇮🇹

   We examine present data for double parton scattering at LHC and discuss their energy dependence from its earliest measurements at the ISR. Different models for the effective cross-section are considered and their behavior studied for a variety of selected final states. We point out that data for pp ->4 jets or pp -> quarkonium pair indicate the effective cross-section to increase with energy. We compare this set of data with different models, including one inspired by our soft gluon resummation model for the impact parameter distribution of partons.

   hep-ph0 citations
10. 10*

    High energy asymptotic behavior of the $S$-matrix in the saturation region with the smallest dipole running coupling prescription

    Wenchang Xiang🇨🇳 · Yanbing Cai🇨🇳 · Mengliang Wang🇨🇳 · Daicui Zhou🇨🇳

    We present results from analytic solutions to the running coupling, full next-to-leading order, and collinearly improved next-to-leading order Balitsky-Kovchegov equations in the saturation region with the smallest dipole size QCD running coupling prescription. The analytic results of the $S$-matrix of the latter two equations show that the $\exp (-\mathcal{O}(Y^{3/2}))$ rapidity dependence of the solutions are replaced by $\exp (-\mathcal{O}(Y))$ dependence once the running coupling prescription is switched from parent dipole to the smallest dipole prescription, which indicate that the $S$-matrix has a strong dependence on the choice of running coupling prescription. We compute the numerical solutions of these Balitsky-Kovchegov equations with the smallest and parent dipole running coupling prescriptions, the numerical results confirm the analytic outcomes. The rare fluctuations of the $S$-matrix on top of next-to-leading order corrections are also studied under the smallest dipole running coupling prescription in the center of mass frame. It shows that the rare fluctuations are strongly suppressed and less important in the smallest dipole running coupling prescription case as compared to the parent dipole running coupling prescription case.

    hep-phPRD(2020)·15 citations
11. 11*

    Cross-correlators of conserved charges in QCD

    Rene Bellwied🇺🇸 · Szabolcs Borsanyi🇩🇪 · Zoltan Fodor🇩🇪 · Jana N. Guenther🇩🇪 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇺🇸 · Attila Pasztor🇭🇺 · Claudia Ratti🇺🇸 · Jamie M. Stafford🇺🇸

    We present cross-correlators of QCD conserved charges at ${\mu }_B=0$ from lattice simulations and perform a Hadron Resonance Gas (HRG) model analysis to break down the hadronic contributions to these correlators. We construct a suitable hadronic proxy for the ratio $-{\chi }_{11}^{BS}/{\chi }_2^S$ and discuss the dependence on the chemical potential and experimental cuts. We then perform a comparison to preliminary STAR results and comment on a possible direct comparison of lattice and experiment.

    hep-phhep-latnucl-thSpringer Proc.Phys.(2020)·0 citations
12. 12*

    Heavy quark transport in a viscous semi QGP

    Balbeer Singh🇮🇳 · Hiranmaya Mishra🇮🇳

    We study the effect of shear and bulk viscosities on the heavy quark transport coefficient within the matrix model of semi QGP. Dissipative effects are incorporated through the first-order viscous correction in the quark/antiquark and gluon distribution function. It is observed that while the shear viscosity effects reduces the drag of heavy quark the bulk viscosity effects increase the drag and the diffusion coefficients of heavy quark. For finite values of {\eta}/s and {\xi}/s, Polyakov loop further decreases the drag and the diffusion coefficients as compared to perturbative QCD.

    hep-phPRD(2020)·18 citations
13. 13*

    Two-component asymmetric dark matter via bound states and freeze-in decay

    Mathias Becker🇩🇪 · Wei-Chih Huang🇩🇰

    We propose a novel mechanism to realize two-component asymmetric dark matter of very different mass scales through bound state formation and late freeze-in decay. Assuming a particle-antiparticle asymmetry is initially shared by SM baryons and two dark matter components, we demonstrate that the existence of bound states formed by the heavy component can efficiently transfer the asymmetry from the heavy to the light component via late decay. In this case, the energy densities of the two components can be comparable, and the correct relic density is reproduced.

    hep-phastro-ph.CO4 citations
14. 14*

    Radiative corrections for Dalitz decays of ${\pi }^0$, ${\eta }^{(\prime )}$ and ${\Sigma }^0$

    Tomáš Husek (IFIC, Valencia)🇪🇸

    We briefly summarize current experimental and theoretical results on the ${\pi }^0$ Dalitz decay, including the new value for the ratio $R=\Gamma ({\pi }^0\to e^{+}{e}^{-}\gamma (\gamma ))/\Gamma ({\pi }^0\to \gamma \gamma )=11.978(6)\times 10^{-3}$, which is by two orders of magnitude more precise than the current PDG average. Furthermore, we discuss radiative corrections for the Dalitz decays ${\eta }^{(\prime )}\to {\ell }^{+}{\ell }^{-}\gamma$ beyond the soft-photon approximation. The corrections inevitably depend on the ${\eta }^{(\prime )}\to {\gamma }^{\ast }{\gamma }^{(\ast )}$ transition form factors. Finally, we present (inclusive) radiative corrections for the ${\Sigma }^0\to \Lambda e^{+}{e}^{-}$ decay, evaluated as well beyond the soft-photon approximation, i.e., over the whole range of the Dalitz plot and with no restrictions on the energy of the radiative photon. Here, we also calculate explicitly the 1$\gamma$IR contribution and the correction to the ${\Sigma }^0\Lambda \gamma$ vertex and confirm that these can be neglected.

    hep-phNucl.Part.Phys.Proc.(2020)·1 citation
15. 15*

    Standard-model prediction of ${ϵ}_K$ with manifest CKM unitarity

    Joachim Brod🇺🇸 · Martin Gorbahn🇬🇧 · Emmanuel Stamou🇨🇭

    The parameter ${ϵ}_K$ describes CP violation in the neutral kaon system and is one of the most sensitive probes of new physics. The large uncertainties related to the charm-quark contribution to ${ϵ}_K$ have so far prevented a reliable standard-model prediction. We show that CKM unitarity enforces a unique form of the $|\Delta S=2|$ weak effective Lagrangian in which the short-distance theory uncertainty of the imaginary part is dramatically reduced. The uncertainty related to the charm-quark contribution is now at the percent level. We present the updated standard-model prediction ${ϵ}_K=2.16(6)(8)(15)\times 10^{-3}$, where the errors in brackets correspond to QCD short-distance and long-distance, and parametric uncertainties, respectively.

    hep-phhep-latPRL(2020)·92 citations
16. 16*

    Two-Higgs-Doublet Models with a Flavored ${\mathbb{Z}}_2$

    S. Centelles Chuliá🇪🇸 · W. Rodejohann🇩🇪 · U. J. Saldaña-Salazar🇩🇪

    Two Higgs-doublet models usually consider an ad-hoc ${\mathbb{Z}}_2$ discrete symmetry to avoid flavor changing neutral currents. We consider a new class of two Higgs-doublet models where ${\mathbb{Z}}_2$ is enlarged to the symmetry group $\mathcal{F}⋊{\mathbb{Z}}_2$, i.e. an inner semi-direct product of a discrete symmetry group $\mathcal{F}$ and ${\mathbb{Z}}_2$. In such a scenario the symmetry constrains the Yukawa interactions but goes unnoticed by the scalar sector. In the most minimal scenario, ${\mathbb{Z}}_3⋊{\mathbb{Z}}_2=D_3$, flavor changing neutral currents mediated by scalars are absent at tree and one-loop level, while at the same time predictions to quark and lepton mixing are obtained, namely a trivial CKM matrix and a PMNS matrix (upon introduction of three heavy right-handed neutrinos) containing maximal atmospheric mixing. Small extensions allow to fully reproduce mixing parameters, including cobimaximal mixing in the lepton sector (maximal atmospheric mixing and a maximal $CP$ phase).

    hep-phPRD(2020)·6 citations
17. 17*

    Quantum Computing for Neutrino-nucleus Scattering

    Alessandro Roggero🇺🇸 · Andy C. Y. Li🇺🇸 · Joseph Carlson🇺🇸 · Rajan Gupta🇺🇸 · Gabriel N. Perdue🇺🇸

    Neutrino-nucleus cross section uncertainties are expected to be a dominant systematic in future accelerator neutrino experiments. The cross sections are determined by the linear response of the nucleus to the weak interactions of the neutrino, and are dominated by energy and distance scales of the order of the separation between nucleons in the nucleus. These response functions are potentially an important early physics application of quantum computers. Here we present an analysis of the resources required and their expected scaling for scattering cross section calculations. We also examine simple small-scale neutrino-nucleus models on modern quantum hardware. In this paper, we use variational methods to obtain the ground state of a three nucleon system (the triton) and then implement the relevant time evolution. In order to tame the errors in present-day NISQ devices, we explore the use of different error-mitigation techniques to increase the fidelity of the calculations.

    ↳ quant-phhep-lathep-phnucl-thPRD(2020)·112 citations
18. 18*

    Information Theoretic Bounds on Cosmic String Detection in CMB Maps with Noise

    Razvan Ciuca🇨🇦 · Oscar F. Hernández🇨🇦

    We use a convolutional neural network (CNN) to study cosmic string detection in cosmic microwave background (CMB) flat sky maps with Nambu-Goto strings. On noiseless maps we can measure string tensions down to order $10^{-9}$, however when noise is included we are unable to measure string tensions below $10^{-7}$. Motivated by this impasse, we derive an information theoretic bound on the detection of the cosmic string tension $G\mu$ from CMB maps. In particular we bound the information entropy of the posterior distribution of $G\mu$ in terms of the resolution, noise level and total survey area of the CMB map. We evaluate these bounds for the ACT, SPT-3G, Simons Observatory, Cosmic Origins Explorer, and CMB-S4 experiments. These bounds cannot be saturated by any method.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2020)·10 citations
19. 19*

    Equation of state of QCD matter within the Hagedorn bag-like model

    Volodymyr Vovchenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Carsten Greiner🇩🇪 · Horst Stoecker🇩🇪

    The QCD equation of state at finite temperature and densities of conserved charges is considered in the framework of a Hagedorn bag-like model, incorporating both the finite sizes of hadrons as well as their exponential mass spectrum. Augmented with non-zero masses of quarks and gluons in the bag spectrum, the model yields a fair quantitative description of lattice data on thermodynamic functions, the conserved charges susceptibilities, and Fourier coefficients of net-baryon density. Both at zero and finite baryon densities a broad crossover transition between hadronic and quark-gluon matter is observed. The model thus provides a thermodynamically consistent construction of a crossover equation of state for finite baryon number, electric charge and strangeness chemical potentials, which can be used in fluid dynamical simulations of heavy-ion collisions.

    ↳ nucl-thhep-phSpringer Proc.Phys.(2020)·2 citations
20. 20*

    Longitudinal dependence of open heavy flavor $R_{\text{AA}}$ in relativistic heavy-ion collisions

    Caio A. G. Prado🇨🇳 · Wen-Jing Xing🇨🇳 · Shanshan Cao🇺🇸 · Guang-You Qin🇨🇳 · Xin-Nian Wang🇨🇳

    Heavy flavor probes are sensitive to the properties of the quark gluon plasma (QGP) produced in relativistic heavy-ion collisions. A huge amount of effort has been devoted to studying different aspects of the heavy-ion collisions using heavy flavor particles. In this work, we study the dynamics of heavy quark transport in the QGP medium using the rapidity dependence of heavy flavor observables. We calculate the nuclear modification of $\text{B}$ and $\text{D}$ meson spectra as well as spectra of leptons from heavy flavor decays in the rapidity range $[-4.0,4.0]$. We use an implementation of the improved Langevin equation with gluon radiation on top of a (3+1)-dimensional relativistic viscous hydrodynamical background for several collision setups. We find that the rapidity dependence of the heavy quark modification is determined by the interplay between the smaller size of the medium, which affects the path length of the heavy quarks, and the softer heavy quark initial production spectrum. We compare our results with available experimental data and present predictions for open heavy flavor meson $R_{\text{AA}}$ at finite rapidity.

    ↳ nucl-thhep-exhep-phPRC(2020)·9 citations
21. 21*

    An $S$-Matrix for Massless Particles

    Holmfridur Hannesdottir🇺🇸 · Matthew D. Schwartz🇺🇸

    The traditional $S$-matrix does not exist for theories with massless particles, such as quantum electrodynamics. The difficulty in isolating asymptotic states manifests itself as infrared divergences at each order in perturbation theory. Building on insights from the literature on coherent states and factorization, we construct an $S$-matrix that is free of singularities order-by-order in perturbation theory. Factorization guarantees that the asymptotic evolution in gauge theories is universal, i.e. independent of the hard process. Although the hard $S$-matrix element is computed between well-defined few particle Fock states, dressed/coherent states can be seen to form as intermediate states in the calculation of hard $S$-matrix elements. We present a framework for the perturbative calculation of hard $S$-matrix elements combining Lorentz-covariant Feynman rules for the dressed-state scattering with time-ordered perturbation theory for the asymptotic evolution. With hard cutoffs on the asymptotic Hamiltonian, the cancellation of divergences can be seen explicitly. In dimensional regularization, where the hard cutoffs are replaced by a renormalization scale, the contribution from the asymptotic evolution produces scaleless integrals that vanish. A number of illustrative examples are given in QED, QCD, and $\mathcal{N}=4$ super Yang-Mills theory.

    ↳ hep-thhep-phPRD(2020)·84 citations
22. 22*

    GFiRe: a Gauge Field integrator for Reheating

    Kaloian D. Lozanov🇩🇪 · Mustafa A. Amin🇺🇸

    We present a new numerical algorithm and code, $\mathsf{GFiRe}$, for solving the non-linear evolution of Abelian gauge fields coupled to complex scalar fields in homogeneous and isotropic spacetimes. We adopt a hybrid approach to solving the system: the spatial derivatives are discretized using standard Lattice Gauge Field Theory techniques, whereas the time evolution of the fields and scale factor is implemented with explicit, composite, symplectic integrators. An important property of our compound algorithm is that the discretized Gauss constraint is respected exactly, regardless of the order of the symplectic integrator. This remains true even when the background expansion is computed "self-consistently"; that is, when the expansion history is computed using spatial averaged components of the energy momentum tensor in the simulation volume. Hence, our code can also be used in cases where the fields dominate the energy density of the universe, for example, during reheating after inflation. We test the algorithm in scenarios of reheating where the inflaton is a complex scalar field with a potential $\propto (2|\phi {|}^2-v^2{)}^2$ and is coupled to an Abelian gauge field. Tracing the evolution of the system through complex dynamics (including resonant excitation of fields, backreaction, formation of solitons, and changes in the equation of state) in a self-consistently expanding universe, we find the energy conservation violation ($<10^{-4}$) to be very stable and the Gauss constraint violation ($<10^{-6}$) to be dominated by differencing noise.

    ↳ astro-ph.COgr-qchep-lathep-phJCAP(2020)·31 citations
23. 23*

    Horizon thermodynamics in holographic cosmological models with a power-law term

    Nobuyoshi Komatsu🇯🇵

    Thermodynamics on the horizon of a flat universe at late times is studied in holographic cosmological models that assume an associated entropy on the horizon. In such models, a $\Lambda (t)$ model similar to a time-varying $\Lambda (t)$ cosmology is favored because of the consistency of energy flows across the horizon. Based on this consistency, a $\Lambda (t)$ model with a power-law term proportional to $H^{\alpha }$ is formulated to systematically examine the evolution of the Bekenstein--Hawking entropy. Here, $H$ is the Hubble parameter and $\alpha$ is a free parameter whose value is a real number. The present model always satisfies the second law of thermodynamics on the horizon. In particular, the universe for $\alpha <2$ tends to approach thermodynamic equilibrium-like states. Consequently, when $\alpha <2$, the maximization of the entropy should be satisfied as well, at least in the last stage of the evolution of an expanding universe. A relaxation-like process before the last stage is also examined from a thermodynamics viewpoint.

    ↳ gr-qchep-phPRD(2019)·17 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.