Mon·Oct 18, 2021Monday·October 18, 2021

1. 01*

   Machine learning the Higgs boson-top quark CP phase

   Rahool Kumar Barman🇺🇸 · Dorival Gonçalves🇺🇸 · Felix Kling🇩🇪

   We explore the direct Higgs-top CP measurement via the $pp\to t\bar{t}h$ channel at the high-luminosity LHC. We show that a combination of machine learning techniques and efficient kinematic reconstruction methods can boost new physics sensitivity, effectively probing the complex $t\bar{t}h$ multi-particle phase space. Special attention is devoted to top quark polarization observables, uplifting the analysis from a raw rate to a polarization study. Through a combination of hadronic, semi-leptonic, and di-leptonic top pair final states in association with $h\to \gamma \gamma$, we obtain that the HL-LHC can probe the Higgs-top coupling modifier and CP-phase, respectively, up to $|{\kappa }_t|\lesssim 8\%$ and $|\alpha |\lesssim 13^{\circ }$ at $68\%$~CL.

   hep-phhep-exPRD(2022)·53 citations
2. 02*

   Precise LHC limits on the ${\mathrm{U}}_1$ leptoquark parameter space

   Arvind Bhaskar🇮🇳 · Diganta Das🇮🇳 · Tanumoy Mandal🇮🇳 · Subhadip Mitra🇮🇳 · Cyrin Neeraj🇮🇳

   A TeV scale leptoquark (LQ) is one of the promising explanations of the recent anomalies in the semileptonic decays of $B$ mesons. Among the various LQs, the vector ${\mathrm{U}}_1$ is capable of explaining the anomalies in both $R_{D^{(\ast )}}$ and $R_{K^{(\ast )}}$ observables. We use the current LHC data to put bounds on the parameter space of ${\mathrm{U}}_1$ relevant for the anomalies. Precise bounds are drawn by recasting the latest $\tau \tau$ and $\mu \mu$ searches by the ATLAS and CMS collaborations. We find that it is imperative to include the resonant production modes for obtaining limits in the low mass regions. For higher mass points, the non-resonant production modes play a dominant role.

   hep-phPoS(2022)·0 citations
3. 03*

   A generalization of the Scotogenic model

   Pablo Escribano🇪🇸

   The Scotogenic model is a radiative neutrino mass model able to induce Majorana neutrino masses at the 1-loop level and simultaneously include a dark matter candidate. In this work, we generalize the original Scotogenic model to arbitrary numbers of generations of the Scotogenic states. After that, we present the light neutrino mass matrix, with some details of its derivation, and provide a useful approximate expression as well. Finally, we numerically solve the Renormalization Group Equations to explore the high-energy behavior of the model.

   hep-phJ.Phys.Conf.Ser.(2021)·2 citations
4. 04*

   EFT description of the muon magnetic dipole moment

   Jason Aebischer🇨🇭

   An Effective Field Theory (EFT) analysis of the magnetic moment of the muon is discussed. The expression for the dipole moment is given in terms of operator coefficients of the low-energy effective field theory (LEFT) and the Standard Model effective field theory (SMEFT), where one-loop renormalization group improved perturbation theory, the one-loop matching from SMEFT onto LEFT as well as one-loop lepton matrix elements of the effective-theory operators were taken into account. Interestingly only a very limited set of the SMEFT operators is able to explain the current deviation of the magnetic moment of the muon from its Standard Model expectation.

   hep-phPoS(2022)·2 citations
5. 05*

   Multiscale pentagon integrals to all orders

   Dhimiter D. Canko🇬🇷 · Costas G. Papadopoulos🇬🇷 · Nikolaos Syrrakos🇬🇷

   We present analytical results for one-loop five-point master integrals with up to three off-shell legs. The method of canonical differential equations along with the Simplified Differential Equations approach is employed. All necessary boundary terms are given in closed form, resulting to solutions in terms of Goncharov Polylogarithms of arbitrary weight. Explicit results up to weight six will be presented.

   hep-phSciPost Phys.Proc.(2022)·0 citations
6. 06*

   Logarithmic corrections for jet production at the LHC

   Emmet P. Byrne🇬🇧

   Several important processes and analyses at the LHC are sensitive to higher-order perturbative corrections beyond what can currently be calculated at fixed order. One important class of logarithmic corrections are those which appear when the centre-of-mass energy of a QCD collision is much larger than the transverse momenta of the observed jets. We describe the High Energy Jets (HEJ) framework, which includes the dominant high-energy logarithms to provide all-order predictions for several LHC processes including Higgs, $W$, or $Z$ boson production in association with jets. We will summarise some recent developments, in particular the first matching of HEJ to a NLO calculation.

   hep-phSciPost Phys.Proc.(2022)·0 citations
7. 07*

   $N^{3}LO$ calculations for $2\to 2$ processes using Simplified Differential Equations

   Dhimiter D. Canko🇬🇷 · Federico Gasparotto🇮🇹 · Luca Mattiazzi🇮🇹 · Costas G. Papadopoulos🇬🇷 · Nikolaos Syrrakos🇬🇷

   We present the computation of the massless three-loop ladder-box family with one external off-shell leg using the Simplified Differential Equations (SDE) approach. We also discuss the methods we used for finding a canonical differential equation for the two tennis-court families with one off-shell leg, and the application of the SDE approach on these two families.

   hep-phhep-thSciPost Phys.Proc.(2022)·8 citations
8. 08*

   Rescaling the isospin triangle argument for constraining ${\varphi }_2$ ($\alpha$): consolidating Belle II and a potential path forward for LHCb

   J. Dalseno🇪🇸

   A rescaling of the SU(2) isospin triangles constraining ${\varphi }_2$ ($\alpha$) that relies on measurements of the experimentally cleaner relative branching fractions, as opposed to those absolute, is proposed. Paving the way towards more systematically sustainable analysis, this method promises to eliminate a dominant systematic at Belle II amongst others, namely the uncertainty on the number of $B\bar{B}$ pairs in data. Furthermore, a ${\varphi }_2$ constraint in the $B\to \rho \rho$ system at LHCb that is more independent of Belle II input is shown to become viable even without a measurement of $CP$ violation in $B^0\to {\rho }^{+}{\rho }^{-}$.

   hep-phhep-exEur.Phys.J.Plus(2022)·1 citation
9. 09*

   Top-quark production at approximate N${}^3$LO

   Nikolaos Kidonakis🇺🇸

   I discuss recent theoretical results with soft-gluon corrections for various top-quark production processes through approximate N${}^3$LO, including soft anomalous dimensions through three loops. I present numerical results for total cross sections and differential distributions for top-pair and $tW$ production as well as for three-particle final states with a top quark and a Higgs boson. I show that soft-gluon corrections are dominant for a large range of collider energies.

   hep-phPoS(2022)·2 citations
10. 10*

    Comment on "Flavor invariants and renormalization-group equations in the leptonic sector with massive Majorana neutrinos"

    Jianlong Lu🇸🇬

    Recently in [JHEP 09 (2021) 053], Wang et al. discussed the polynomial ring formed by flavor invariants in the leptonic sector with massive Majorana neutrinos. They have explicitly constructed the finite generating sets of the polynomial rings for both two-generation scenario and three-generation scenario. However, Wang et al.'s claim of the finiteness of the generating sets of the polynomial rings and their calculation by the approach of Hilbert series with generalized Molien-Weyl formula are both based on their assertion that the unitary group $\mathrm{U}(n,\mathbb{C})$ is reductive, which is unfortunately incorrect. The property of being reductive is only applicable to linear algebraic groups. And it is well-known that the unitary group $\mathrm{U}(n,\mathbb{C})$ is not even a linear algebraic group. In this paper, we point out the above issue and provide a solution to fill in the accompanying logical gaps in [JHEP 09 (2021) 053]. Some important results from the theory of linear algebraic group, the invariant theory of square matrices and group theory are needed in the analysis. We also clarify some somewhat misleading or vague statements in [JHEP 09 (2021) 053] about the scope of flavor invariants. Note that, although built from incorrect assertion, Wang et al.'s calculation results in [JHEP 09 (2021) 053] are nonetheless correct, which is ultimately because the ring of invariants of $\mathrm{U}(n,\mathbb{C})$ is isomorphic to that of $\mathrm{GL}(n,\mathbb{C})$ which is itself reductive.

    hep-phJHEP(2022)·14 citations
11. 11*

    Holographic QCD model for $N_f=4$

    Yidian Chen🇨🇳 · Mei Huang🇨🇳

    We establish a holographic QCD model for four flavors, where a light scalar field $X$ and a heavy scalar field $H$ are introduced, separately. The $H$ field is responsible for the breaking of $SU(N_f=4)$ to $SU(N_f=3)$. The ground state and its Regge excitation of meson spectra in the light flavor sector and heavy flavor sector as well as the ligh-heavy mesons are well in agreement with the Particle data group (PDG). Due to the additional introduction of the $H$ field in the model, different Regge slopes for light and heavy mesons can be achieved.

    hep-phPRD(2022)·17 citations
12. 12*

    Correlation and Combination of Sets of Parton Distributions

    Richard D. Ball🇬🇧 · Stefano Forte🇮🇹 · Roy Stegeman🇮🇹

    We study the correlation between different sets of parton distributions (PDFs). Specifically, viewing different PDF sets as distinct determinations, generally correlated, of the same underlying physical quantity, we examine the extent to which the correlation between them is due to the underlying data. We do this both for pairs of PDF sets determined using a given fixed methodology, and between sets determined using different methodologies. We show that correlations have a sizable component that is not due to the underlying data, because the data do not determine the PDF uniquely. We show that the data-driven correlations can be used to assess the efficiency of methodologies used for PDF determination. We also show that the use of data-driven correlations for the combination of different PDFs into a joint set can lead to inconsistent results, and thus that the statistical combination used in constructing the widely used PDF4LHC15 PDF set remains the most reliable method.

    hep-phhep-exEPJC(2021)·20 citations
13. 13*

    Holographic modeling of nuclear matter and neutron stars

    Matti Jarvinen🇰🇷

    I review holographic models for (dense and cold) nuclear matter, neutron stars, and their mergers. I start by a brief general discussion on current knowledge of cold QCD matter and neutron stars, and go on discussing various approaches to model cold nuclear and quark matter by using gauge/gravity duality, pointing out their strengths and weaknesses. Then I focus on recent results for a complex bottom-up holographic framework (V-QCD), which also takes input from lattice QCD results, effective field theory, and perturbative QCD. Dense nuclear matter is modeled in V-QCD through a homogeneous non-Abelian bulk gauge field. Feasible "hybrid" equations of state for cold nuclear (and quark) matter can be constructed by using traditional methods (e.g., effective field theory) at low densities and the holographic V-QCD model at higher densities. I discuss the constraints from this approach to the properties of the nuclear to quark matter transition as well as to properties of neutron stars. Using such hybrid equations of state as an input for numerical simulations of neutron star mergers, I also derive predictions for the spectrum of produced gravitational waves.

    hep-phastro-ph.HEhep-thnucl-thEPJC(2022)·87 citations
14. 14*

    Boundedness from below of SU(n) potentials

    Renato M. Fonseca🇨🇿

    Vacuum stability requires that the scalar potential is bounded from below. Whether or not this is true depends on the scalar quartic interactions alone, but even so the analysis is arduous and has only been carried out for a limited set of models. Complementing the existing literature, this work contains the necessary and sufficient conditions for two SU(n) invariant potentials to be bounded from below. In particular, expressions are given for models with the fundamental and the 2-index (anti)symmetric representations of this group. A sufficient condition for vacuum stability is also provided for models with the fundamental and the adjoint representations. Finally, some considerations are made concerning the model with the gauge group SU(2) and the scalar representations $1$, $2$ and $3$; such a setup is particularly important for neutrino mass generation and lepton number violation.

    hep-phhep-thPRD(2022)·0 citations
15. 15*

    Finite-density QCD, $\mathcal{P}\mathcal{T}$ symmetry, and exotic phases

    Moses A. Schindler🇺🇸 · Stella T. Schindler🇺🇸 · Michael C. Ogilvie🇺🇸

    We study the phase structure of effective models of finite-density QCD using analytic and lattice simulation techniques developed for the study of non-Hermitian and $\mathcal{P}\mathcal{T}$-symmetric QFTs. Finite-density QCD is symmetric under the combined operation of the charge and complex conjugation operators $\mathcal{C}\mathcal{K}$, which falls into the class of so-called generalized $\mathcal{P}\mathcal{T}$ symmetries. We show that $\mathcal{P}\mathcal{T}$-symmetric quantum field theories can support patterned ground-state field configurations in the vicinity of a critical endpoint. We apply our methods to a lattice heavy quark model at nonzero chemical potential that displays patterning behavior for a range of parameters. We derive a simple approximate criterion for the formation of these patterns, which can be used with lattice results.

    ↳ hep-lathep-phnucl-thPoS(2022)·8 citations
16. 16*

    Dilaton chiral perturbation theory and applications

    Maarten Golterman🇺🇸 · Yigal Shamir🇮🇱

    We review dilaton chiral perturbation theory (dChPT), the effective low-energy theory for the light sector of near-conformal, confining theories. dChPT provides a systematic expansion in both the fermion mass and the distance to the conformal window. It accounts for the pions and the light scalar, the approximate Nambu-Goldstone bosons for chiral and scale symmetry, respectively. A unique feature of dChPT is the existence of a large-mass regime in which the theory exhibits approximate hyperscaling, while the expansion nevertheless remains systematic. We discuss applications to lattice data, presenting successes as well as directions for future work.

    ↳ hep-lathep-phPoS(2024)·8 citations
17. 17*

    Renormalized ${\rho }_{\mathrm{vac}}$ without $m^4$ terms

    Cristian Moreno-Pulido🇪🇸 · Joan Sola Peracaula🇪🇸

    The cosmological constant term, $\Lambda$, in Einstein's equations has been for three decades a building block of the concordance or standard $\Lambda$CDM model of cosmology. Although the latter is not free of fundamental problems, it provides a good phenomenological description of the overall cosmological observations. However, an interesting improvement in such a phenomenological description and also a change in the theoretical status of the $\Lambda$-term occurs upon realizing that the vacuum energy density, ${\rho }_{\text{vac}}$, is actually a "running quantity" in quantum field theory in curved spacetime. Several works have shown that this option can compete with the $\Lambda$CDM with a rigid $\Lambda$term. The so-called, "running vacuum models" (RVM) are characterized indeed by a ${\rho }_{\text{vac}}$ which is evolving with time as a series of even powers of the Hubble parameter and its time derivatives. This form has been motivated by renormalization group arguments in previous works. Here we review a recent detailed computation by the authors of the renormalized energy-momentum tensor of a non-minimally coupled scalar field with the help of adiabatic regularization. The final result is noteworthy: ${\rho }_{\text{vac}}(H)$ takes the precise structure of the RVM, namely a constant term plus a dynamical component $\sim H^2$ (which may be detectable in the present universe) including also higher order effects $\mathcal{O}(H^4)$ which can be of interest during the early stages of the cosmological evolution. Besides, it is most remarkable that such renormalized form of ${\rho }_{\text{vac}}$ does not carry dangerous terms proportional to $m^4$, the quartic powers of the masses of the fields, which are a well-known source of exceedingly large contributions to the vacuum energy density and are directly responsible for fine tuning in the context of the CC problem.

    ↳ gr-qchep-ph7 citations
18. 18*

    Hamiltonian Truncation Effective Theory

    Timothy Cohen🇺🇸 · Kara Farnsworth🇺🇸 · Rachel Houtz🇬🇧 · Markus A. Luty🇺🇸

    Hamiltonian truncation is a non-perturbative numerical method for calculating observables of a quantum field theory. The starting point for this method is to truncate the interacting Hamiltonian to a finite-dimensional space of states spanned by the eigenvectors of the free Hamiltonian $H_0$ with eigenvalues below some energy cutoff $E_{\text{max}}$. In this work, we show how to treat Hamiltonian truncation systematically using effective field theory methodology. We define the finite-dimensional effective Hamiltonian by integrating out the states above $E_{\text{max}}$. The effective Hamiltonian can be computed by matching a transition amplitude to the full theory, and gives corrections order by order as an expansion in powers of $1/E_{\text{max}}$. The effective Hamiltonian is non-local, with the non-locality controlled in an expansion in powers of $H_0/E_{\text{max}}$. The effective Hamiltonian is also non-Hermitian, and we discuss whether this is a necessary feature or an artifact of our definition. We apply our formalism to 2D $\lambda {\varphi }^4$ theory, and compute the the leading $1/E_{\text{max}}^2$ corrections to the effective Hamiltonian. We show that these corrections non-trivially satisfy the crucial property of separation of scales. Numerical diagonalization of the effective Hamiltonian gives residual errors of order $1/E_{\text{max}}^3$, as expected by our power counting. We also present the power counting for 3D $\lambda {\varphi }^4$ theory and perform calculations that demonstrate the separation of scales in this theory.

    ↳ hep-thcond-mat.str-elhep-lathep-phSciPost Phys.(2022)·25 citations
19. 19*

    Kink-antikink scattering in a quantum vacuum

    Mainak Mukhopadhyay🇺🇸 · Evangelos I. Sfakianakis🇪🇸 · Tanmay Vachaspati🇺🇸 · George Zahariade🇪🇸

    We study kink-antikink scattering in the sine-Gordon model in the presence of interactions with an additional scalar field, $\psi$, that is in its quantum vacuum. In contrast to the classical scattering, now there is quantum radiation of $\psi$ quanta and the kink-antikink may form bound states that resemble breathers of the sine-Gordon model. We quantify the rate of radiation and map the parameters for which bound states are formed. Even these bound states radiate and decay, and eventually there is a transition into long-lived oscillons.

    ↳ hep-thcond-mat.otherhep-phJHEP(2022)·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.