Mon·Apr 1, 2019Monday·April 1, 2019

1. 01*

   QED radiative corrections for Polarized Lepton-Proton Scattering

   Razvan-Daniel Bucoveanu🇩🇪 · Hubert Spiesberger🇩🇪

   We discuss QED radiative corrections at first and second order for the parity violating asymmetry $A_{\text{PV}}$ in elastic electron proton scattering. A measurement of $A_{\text{PV}}$ is planned at low energies and with high precision by the forthcoming P2 experiment at the new MESA facility in Mainz. Bremsstrahlung leads to a shift of the momentum transfer $Q^2$ which affects the determination of the weak charge of the proton.

   hep-phnucl-thPoS(2019)·5 citations
2. 02*

   Theoretical study on \eta'--> 4 pions

   Ehsan Jafari🇺🇸 · Bing An Li🇺🇸

   The ${\eta }^{\prime }$ meson is associated with the U(1) anomaly. In this paper, a successful effective chiral theory of mesons has been applied to study the anomalous decay of ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}{\pi }^{+(0)}{\pi }^{-(0)}$. In this study, the contributions of triangle and box anomalies are calculated. It is shown that the contribution of box diagrams is important in this process. We predict branching ratios of $Br({\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-})=\frac{1}{2}Br({\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0)=(8.3\pm 1.2)\times 10^{-5}$, which is in good agreement with BESIII measurement.

   hep-phnucl-thNPB(2021)·0 citations
3. 03*

   Perturbative unitarity bounds for effective composite models

   S. Biondini🇳🇱 · R. Leonardi🇮🇹 · O. Panella🇮🇹 · M. Presilla🇮🇹

   In this paper we present the partial wave unitarity bound in the parameter space of dimension-5 and dimension-6 effective operators that arise in a compositeness scenario. These are routinely used in experimental searches at the LHC to constraint contact and gauge interactions between ordinary Standard Model fermions and excited (composite) states of mass $M$. After deducing the unitarity bound for the production process of a composite neutrino, we implement such bound and compare it with the recent experimental exclusion curves for Run 2, the High-Luminosity and High-Energy configurations of the LHC. Our results also applies to the searches where a generic single excited state is produced via contact interactions. We find that the unitarity bound, so far overlooked, is quite complelling and significant portions of the parameter space ($M,\Lambda$) become excluded in addition to the standard request $M\le \Lambda$.

   hep-phPLB(2019)·14 citations
4. 04*

   Determining Hadron-Quark Phase Transition Chemical Potential via Astronomical Observations

   Zhan Bai🇨🇳 · Yu-xin Liu🇨🇳

   We propose a scheme to determine the chemical potential and baryon number density of the hadron-quark phase transition in cold dense strong interaction matter (compact star matter). The hadron matter is described with the relativistic mean field theory, and the quark matter is described with the Dyson-Schwinger equation approach of QCD. To study the first-order phase transition, we take the sound speed as the interpolation objective to construct the equation of state in the middle density region. With the maximum mass, the tidal deformability and the radius of neutron stars being taken as calibration quantities, the phase transition chemical potential is constrained to a quite small range. And the most probable value of the phase transition chemical potential is found.

   hep-phastro-ph.HEPRD(2023)·8 citations
5. 05*

   Renormalization of Unitarized Weinberg-Tomozawa Interaction without On-shell Factorization and $I=0$ $\bar{K}N$ - $\pi \Sigma$ Coupled Channels

   Osamu Morimatsu🇯🇵 · Kazuki Yamada🇯🇵

   We calculate the scattering $T$-matrix of $I=0$ $\bar{K}N-\pi \Sigma$ coupled channels taking a ladder sum of the Weinberg-Tomozawa interaction without on-shell factorization, regularizing three types of divergent meson-baryon loop functions by dimensional regularization and renormalizing them by introducing counter terms. We show that not only infinite but also finite renormalization is important in order for the renormalized physical scattering $T$-matrix to have the form of the Weinberg-Tomozawa interaction. The results with and without on-shell factorization are compared. The difference of the scattering $T$-matrix is small near the renormalization point, close to the observed $\Lambda$(1405). The difference, however, increases with the distance from the renormalization point. The scattering $T$-matrix without on-shell factorization has two poles in the complex center-of-mass energy plane as with on-shell factorization, the real part of which is close to the observed $\Lambda$(1405). While the difference is small with and without on-shell factorization in the position of the first pole, closer to the observed $\Lambda$(1405), the difference is considerably large in the position of the second pole: the imaginary part of the center-of-mass energy of the second pole without on-shell factorization is as large as or even larger than twice that with on-shell factorization. Also, we discuss the origin of the contradiction about the second pole between two approaches, the chiral unitary approach with on-shell factorization and the phenomenological approach without on-shell factorization.

   hep-phnucl-thPRC(2019)·12 citations
6. 06*

   Muon $g-2$ in Split-Family SUSY in light of LHC Run II

   Masahiro Ibe🇯🇵 · Motoo Suzuki🇯🇵 · Tsutomu T. Yanagida🇯🇵 · Norimi Yokozaki🇯🇵

   The Split-Family supersymmetry is a model in which the sfermion masses of the first two generations are in $\mathcal{O}(100\text{-}1000)$ GeV while that of the third one is in $\mathcal{O}(10)$TeV. With such a hierarchical spectrum, the deviation of the muon $g-2$ and the observed Higgs boson mass are explained simultaneously. In this paper, we revisit the Split-Family SUSY model in light of the updated LHC constraints. We also study the flavor changing neutral current problems in the model. As we will show, the problems do not lead to stringent constraints when the Cabibbo-Kobayashi-Maskawa matrix is the only source of the flavor mixing. We also study how large flavor mixing in the supersymmetry breaking parameters is allowed.

   hep-phEPJC(2019)·11 citations
7. 07*

   The dispersion method and dimensional regularization applied to the decay $H\to Z\gamma$

   I. Boradjiev🇧🇬 · E. Christova🇧🇬 · H. Eberl🇦🇹

   We have calculated the $W$-loop contribution to the amplitude of the decay $H\to Z\gamma$ in the unitary gauge through the dispersion method and in the $R_{\xi }$ gauge using dimensional regularization (DimReg). We show that the results of the calculations with DimReg and the dispersion method, adopting the boundary condition at the limit $M_W\to 0$ defined by the Goldstone boson equivalence theorem (GBET), completely coincide. This implies that the dispersion method obeying the GBET is compatible with DimReg. The advantage of the applied dispersion method is that we work with finite quantities and no regularization is required.

   hep-phJ.Phys.Conf.Ser.(2020)·0 citations
8. 08*

   KeV scale new fermion from a hidden sector

   We-Fu Chang🇹🇼 · John N. Ng🇨🇦

   We studied a simple model of hidden sector consists of a Dirac fermion $\chi$ and a spontaneously broken $U(1{)}_s$ symmetry. The dark sector is connected to the Standard Model(SM) via three righthanded SM singlet neutrinos, $N_R$'s, and the kinetic mixing between $U(1{)}_s$ and $U(1{)}_Y$. A mixing between the scalar $\varphi$ that breaks $U(1{)}_s$ and the SM Higgs boson, $H$, is implemented via the term ${\varphi }^{†}\varphi H^{†}H$ and this provides a third connection to the SM. Integrating out the $N_R$ at a high scale not only gives the active neutrinos, $\nu$, masses but generates effective Dirac type of couplings between $\nu$ and $\chi$. This changes the usual Type-I seesaw results for active neutrino masses and makes $\chi$ behave like a sterile neutrino even though its origin is in the hidden sector. $\chi$ is also split into a pair of Majorana fermions. The amount of splitting depends on the parameters. If the lighter of the pair has a mass around keV, its lifetime is longer than the age of the universe and it can be a warm dark matter candidate. Signatures of $\chi$ in high precision Kurie plots of nuclei $\beta$ decays and low energy neutrino nuclei coherent scatterings are discussed. The model also induces new invisible $Z$ decay modes that can be searched for in future Z factories.

   hep-phPRD(2020)·2 citations
9. 09*

   Radiative Dirac Neutrino Mass with Dark Matter and it's implication to $0\nu 4\beta$ in the $U(1{)}_{B-L}$ extension of the Standard Model

   Arnab Dasgupta🇰🇷 · Sin Kyu Kang🇰🇷 · Oleg Popov🇰🇷

   The Standard Model gauge symmetry is extended by $U(1{)}_{B-L}$ which when spontaneously broken leads to residual ${\mathbb{Z}}_4$ symmetry. $U(1{)}_{B-L}$ gauge symmetry made anomaly free by introducing exotic SM singlets with corresponding $U(1{)}_{B-L}$ charges of $13$, $-14$, and $15$. ${\mathbb{Z}}_4$ symmetry ensures the Dirac nature of neutrinos, simultaneously stabilizing dark matter. Dirac neutrino mass is generated through scotogenic scenario. Dark matter, direct detection, cosmological constraints, and collider constraints analysis is performed. ${\mathbb{Z}}_4$ symmetry predicts the exact absence of neutrinoless double beta decay ($0\nu 2\beta$) and gives a prediction for an enhanced neutrinoless quadruple beta decay ($0\nu 4\beta$) via which this model can be tested. Model allows for Majorana dark matter as well as for long-lived dark matter candidates.

   hep-phPRD(2019)·37 citations
10. 10*

    Axions are blind to anomalies

    Jérémie Quevillon🇫🇷 · Christopher Smith🇫🇷

    The axion couplings to SM gauge bosons are derived in various models, and shown to always arise entirely from non-anomalous fermion loops. They are thus independent of the anomaly structure of the model. This fact is without consequence for vector gauge interactions like QCD and QED, but has a major impact for chiral gauge theories. For example, in the DFSZ axion model, the couplings of axions to electroweak gauge bosons do not follow the pattern expected from chiral anomalies, as we prove by an explicit calculation. The reason for this mismatch is traced back to triangle Feynman diagrams sensitive to the anomalous breaking of the vector Ward identity, and is ultimately related to the conservation of baryon and lepton numbers. Though our analyses are entirely done for true axion models, this observation could have important consequences for axion-like particle searches.

    hep-phhep-thEPJC(2019)·55 citations
11. 11*

    Jet cross sections at the LHC and the quest for higher precision

    Johannes Bellm🇸🇪 · Andy Buckley🇬🇧 · Xuan Chen🇨🇭 · Aude Gehrmann-De Ridder🇨🇭 · Thomas Gehrmann🇨🇭 · Nigel Glover🇬🇧 · Alexander Huss🇨🇭 · Joao Pires🇵🇹 · Stefan Höche🇺🇸 · Joey Huston🇺🇸 · Silvan Kuttimalai🇺🇸 · Simon Plätzer🇦🇹 · Emanuele Re🇨🇭

    We perform a phenomenological study of $Z$ plus jet, Higgs plus jet and di-jet production at the Large Hadron Collider. We investigate in particular the dependence of the leading jet cross section on the jet radius as a function of the jet transverse momentum. Theoretical predictions are obtained using perturbative QCD calculations at the next-to and next-to-next-to-leading order, using a range of renormalization and factorization scales. The fixed order predictions are compared to results obtained from matching next-to-leading order calculations to parton showers. A study of the scale dependence as a function of the jet radius is used to provide a better estimate of the scale uncertainty for small jet sizes. The non-perturbative corrections as a function of jet radius are estimated from different generators.

    hep-phhep-exEPJC(2020)·44 citations
12. 12*

    Neutrino Mass and Mixing with $A_5$ Modular Symmetry

    Gui-Jun Ding🇨🇳 · Stephen F.King🇬🇧 · Xiang-Gan Liu🇨🇳

    We present a comprehensive analysis of neutrino mass and lepton mixing in theories with $A_5$ modular symmetry. We construct the weight 2, weight 4 and weight 6 modular forms of level 5 in terms of Dedekind eta-functions and Klein forms, and their decomposition into irreducible representation of $A_5$. We construct all the simplest models based on $A_5$ modular symmetry, including scenarios of models with and without flavons in the charged lepton sectors. For each case, the neutrino masses can be generated through either the Weinberg operator or the type I seesaw mechanism. We perform an exhaustive numerical analysis, organising our results in an extensive set of figures and tables.

    hep-phPRD(2019)·181 citations
13. 13*

    Hot-medium effects on ${\rm Y}$ yields in pPb collisions at $\sqrt{s_{\text{NN}}}=8.16$ TeV

    V. H. Dinh🇩🇪 · J. Hoelck🇩🇪 · G. Wolschin🇩🇪

    The respective contributions of cold-matter and hot-medium effects to the suppression of ${\rm Y}(1S)$ and ${\rm Y}(2S)$ mesons in pPb collisions at energies reached at the Large Hadron Collider (LHC) are investigated. Whereas known alterations of the parton density functions in the lead nucleus and coherent parton energy loss account for the leading fraction of the modifications in cold nuclear matter (CNM), the hot-medium (quark-gluon plasma, QGP) effects turn out to be relevant in spite of the small initial spatial extent of the fireball. We compare our transverse-momentum-, rapidity-, and centrality-dependent theoretical results for the ${\rm Y}$ suppression in pPb collisions at a center-of-mass energy of $\sqrt{s_{\text{NN}}}=8.16$ TeV with recent LHCb and preliminary ALICE data from the Large Hadron Collider (LHC). Both cold-matter and hot-medium effects are needed to account for the data. The initial central temperature of the fireball is found to be $T_0\simeq 460$ MeV.

    hep-phPRC(2019)·8 citations
14. 14*

    Update on decaying and annihilating heavy dark matter with the 6-year IceCube HESE data

    Atri Bhattacharya🇧🇪 · Arman Esmaili🇧🇷 · Sergio Palomares-Ruiz🇪🇸 · Ina Sarcevic🇺🇸

    In view of the IceCube's 6-year high-energy starting events (HESE) sample, we revisit the possibility that the updated data may be better explained by a combination of neutrino fluxes from dark matter decay and an isotropic astrophysical power-law than purely by the latter. We find that the combined two-component flux qualitatively improves the fit to the observed data over a purely astrophysical one, and discuss how these updated fits compare against a similar analysis done with the 4-year HESE data. We also update fits involving dark matter decay via multiple channels, without any contribution from the astrophysical flux. We find that a DM-only explanation is not excluded by neutrino data alone. Finally, we also consider the possibility of a signal from dark matter annihilations and perform analogous analyses to the case of decays, commenting on its implications.

    hep-phastro-ph.HEhep-exJCAP(2019)·66 citations
15. 15*

    $W$ radiative decay to heavy-light mesons in HQET factorization through $\mathcal{O}({\alpha }_s)$

    Saadi Ishaq🇨🇳 · Yu Jia🇨🇳 · Xiaonu Xiong🇨🇳 · De-Shan Yang🇨🇳

    Analogous to NRQCD factorization for heavy quarkonium exclusive production, in this work we propose to employ the heavy-quark-effective-theory (HQET) factorization, which has been predominantly applied to account for exclusive $B$ decays, to study the exclusive production of the heavy-flavored mesons. We take $W\to B(D_s)+\gamma$ as a prototype process. The validity of the HQET factorization rests upon the presumed scale hierarchy: $m_W\sim m_b\gg {\Lambda }_{\mathrm{QCD}}$. Through an explicit analysis at next-to-leading order in ${\alpha }_s$ yet at leading order in $1/m_b$, we verify that the decay form factors can indeed be expressed as the convolution between perturbatively calculable hard-scattering kernel and the $B$ meson light-cone distribution amplitude (LCDA) defined in HQET. It is observed that the factorization scale dependence becomes reduced after incorporating the NLO perturbative correction. An interesting future investigation is to identify and resum large collinear logarithms of $m_W/m_b$ that arise ubiquitously in the fixed-order expressions of the hard-scattering kernel in HQET factorization.

    hep-phhep-exPRD(2019)·7 citations
16. 16*

    Monopole production via photon fusion at the LHC

    Vasiliki A. Mitsou🇪🇸

    The existence of magnetic monopoles, also predicted in some GUT theories, would symmetrise Maxwell equations and explain the charge quantisation. Searches for them are being performed in cosmic telescopes as well as in collider experiments, such as MoEDAL and ATLAS. In this report, we focus on the, least explored, photon-fusion mechanism, yet Drell-Yan results are discussed, too. Cross sections for monopoles of spin 0, 1/2 and 1 for an effective monopole-velocity-dependent magnetic charge are presented. For spin-1/2 and spin-1 monopoles, a magnetic-moment term is included, which is treated as a new phenomenological parameter and, together with the velocity-dependent coupling, allows for a perturbative treatment of the cross-section calculation. We present an appropriate implementation of photon-fusion and Drell-Yan processes into MadGraph UFO models, aimed to serve as a useful tool in monopole searches at LHC, especially for photon fusion, given that it has not been considered by experimental collaborations recently. Moreover, the experimental implications of such perturbatively reliable monopole searches are discussed.

    hep-phPoS(2019)·2 citations
17. 17*

    Nuclear Parton Distributions from Lepton-Nucleus Scattering and the Impact of an Electron-Ion Collider

    Rabah Abdul Khalek🇳🇱 · Jacob J. Ethier🇳🇱 · Juan Rojo🇳🇱

    We present a first determination of the nuclear parton distribution functions (nPDF) based on the NNPDF methodology: nNNPDF1.0. This analysis is based on neutral-current deep-inelastic structure function data and is performed up to NNLO in QCD calculations with heavy quark mass effects. For the first time in the NNPDF fits, the ${\chi }^2$ minimization is achieved using stochastic gradient descent with reverse-mode automatic differentiation (backpropagation). We validate the robustness of the fitting methodology through closure tests, assess the perturbative stability of the resulting nPDFs, and compare them with other recent analyses. The nNNPDF1.0 distributions satisfy the boundary condition whereby the NNPDF3.1 proton PDF central values and uncertainties are reproduced at $A=1$, which introduces important constraints particularly for low-$A$ nuclei. We also investigate the information that would be provided by an Electron-Ion Collider (EIC), finding that EIC measurements would significantly constrain the nPDFs down to $x\simeq 5\times 10^{-4}$. Our results represent the first-ever nPDF determination obtained using a Monte Carlo methodology consistent with that of state-of-the-art proton PDF fits, and provide the foundation for a subsequent global nPDF analyses including also proton-nucleus data.

    hep-phhep-exnucl-exnucl-thEPJC(2019)·147 citations
18. 18*

    Searches for other vacua I: bubbles in our universe

    Anson Hook🇺🇸 · Junwu Huang🇨🇦

    We discuss models in which vacua other than our own can be directly observed in the present universe. Models with density-dependent vacuum structure can give rise to `non-lethal'-vacua: vacua with lower energy-density than our vacuum, but only in regions with finite Standard Model densities. These models provide an explicit example of a bubble which is confined to a finite region of space and produces potentially detectable signatures, unlike standard Coleman tunneling events where bubbles expand at the speed of light and are never directly observable. We study the expansion and contraction of a confined bubble created after a core-collapse supernova, focusing on energy deposition that may be observable in the vicinity of a supernova remnant due to the formation and evolution of a confined bubble.

    hep-phastro-ph.HEhep-thJHEP(2019)·17 citations
19. 19*

    Charting the coming synergy between lattice QCD and high-energy phenomenology

    T. J. Hobbs🇺🇸 · Bo-Ting Wang🇺🇸 · Pavel M. Nadolsky🇺🇸 · Fredrick I. Olness🇺🇸

    Building upon the PDFSense framework developed in Ref. [1], we perform a comprehensive analysis of the sensitivity of present and future high-energy data to a number of quantities commonly evaluated in lattice gauge theory, with a particular focus on the integrated Mellin moments of nucleon parton distribution functions (PDFs), such as $⟨x{⟩}_{u^{+}-d^{+}}$ and $⟨x{⟩}_g$, as well as $x$-dependent quark quasi-distributions -- in particular, that of the isovector combination. Our results demonstrate the potential for lattice calculations and phenomenological quark distributions informed by high-energy experimental data to cooperatively improve the picture of the nucleon's collinear structure. This will increasingly be the case as computational resources for lattice calculations further expand, and QCD global analyses continue to grow in sophistication. Our sensitivity analysis suggests that a future lepton-hadron collider would be especially instrumental in providing phenomenological constraints to lattice observables.

    hep-phhep-exhep-latnucl-thPRD(2019)·45 citations
20. 20*

    Structure of resonances in a square well potential

    Peter C. Bruns🇨🇿

    We study the structure of resonances as derived from the exactly solvable Lippmann-Schwinger equation for a one-dimensional square well potential. Within this framework, we discuss the concept of resonance form factors, and the relation of the corresponding spatial densities to ``resonance wave functions''.

    hep-ph1 citation
21. 21*

    Quantum non-linear evolution of inflationary tensor perturbations

    Jinn-Ouk Gong🇰🇷 · Min-Seok Seo🇰🇷

    We study the quantum mechanical evolution of the tensor perturbations during inflation with non-linear tensor interactions. We first obtain the Lindblad terms generated by non-linear interactions by tracing out unobservable sub-horizon modes. Then we calculate explicitly the reduced density matrix for the super-horizon modes, and show that the probability of maintaining the unitarity of the squeezed state decreases in time. The decreased probability is transferred to other elements of the reduced density matrix including off-diagonal ones, so the evolution of the reduced density matrix describes the quantum-to-classical transition of the tensor perturbations. This is different from the classicality accomplished by the squeezed state, the suppression of the non-commutative effect, which is originated from the quadratic, linear interaction, and also maintains the unitarity. The quantum-to-classical transition occurs within 5 - 10 e-folds, faster than the curvature perturbation.

    ↳ hep-thastro-ph.COgr-qchep-ph+1JHEP(2019)·37 citations
22. 22*

    Higgs to $\tau \tau$ analysis in the future $e^{+}{e}^{-}$ Higgs factories

    Dan Yu🇨🇳 · Manqi Ruan🇨🇳 · Vincent Boudry🇫🇷 · Henri Videau🇫🇷 · Jean-Claude Brient🇫🇷

    The Circular Electron Positron Collider and International Linear Collider are two electron positron Higgs factories. They are designed to operate at center-of-mass energy of 240 and 250 GeV and accumulate 5.6 and 2 $a{b}^{-1}$ of integrated luminosity. Using CEPC official samples, the signal strength for Higgs to $\tau \tau$ events are analyzed. The combined accuracy of the signal strength for $H\to \tau \tau$ at CEPC achieves 0.8\%. Extrapolating this analysis to the ILC setup, we conclude the ILC can reach a relative accuracy of 1.1\% or 1.2\%, corresponding to two benchmark settings of the beam polarization.

    ↳ hep-exhep-ph4 citations
23. 23*

    Geometry of ultraperipheral nuclear collisions

    I.M. Dremin🇷🇺

    It is advocated that geometry of the interaction region of two heavy nuclei colliding at large impact parameters is important for the relative role of light-by-light scattering and QCD-initiated processes. Exclusive production of resonances is possible by dense electromagnetic fields in the interior space between the nuclei. The cross section of these processes is evaluated and some examples are considered. It is speculated that the exclusive production of ${\rho }^0$-mesons by two-photon processes forbidden by the Landau-Yang rule may become allowed within strong magnetic fields.

    ↳ nucl-thhep-exhep-phnucl-exInt.J.Mod.Phys.A(2019)·9 citations
24. 24*

    Maxwell electrodynamics modified by a CPT-odd dimension-five higher-derivative term

    Manoel M. Ferreira Jr.🇧🇷 · Letícia Lisboa-Santos🇧🇷 · Roberto V. Maluf🇧🇷 · Marco Schreck🇧🇷

    In this paper, we consider an electrodynamics of higher derivatives coupled to a Lorentz-violating background tensor. Specifically, we are interested in a dimension-five term of the CPT-odd sector of the nonminimal Standard-Model Extension. By a particular choice of the operator ${\hat{k}}_{AF}$, we obtain a higher-derivative version of the Carroll-Field-Jackiw (CFJ) term, $\frac{1}{2}{ϵ}^{\kappa \lambda \mu \nu }{A}_{\lambda }{D}_{\kappa }\square F_{\mu \nu }$, with a Lorentz-violating background vector $D_{\kappa }$. This modification is subject to being investigated. We calculate the propagator of the theory and from its poles, we analyze the dispersion relations of the isotropic and anisotropic sectors. We verify that classical causality is valid for all parameter choices, but that unitarity of the theory is generally not assured. The latter is found to break down for certain configurations of the background field and momentum. In an analog way, we also study a dimension-five anisotropic higher-derivative CFJ term, which is written as ${ϵ}^{\kappa \lambda \mu \nu }{A}_{\lambda }{T}_{\kappa }(T\cdot \partial {)}^2{F}_{\mu \nu }$ and is directly linked to the photon sector of Myers-Pospelov theory. Within the second model, purely timelike and spacelike $T_{\kappa }$ are considered. For the timelike choice, one mode is causal, whereas the other is noncausal. Unitarity is conserved, in general, as long as the energy stays real - even for the noncausal mode. For the spacelike scenario, causality is violated when the propagation direction lies within certain regimes. However, there are particular configurations preserving unitarity and strong numerical indications exist that unitarity is guaranteed for all purely spacelike configurations. The results improve our understanding of nonminimal CPT-odd extensions of the electromagnetic sector.

    ↳ hep-thhep-phPRD(2019)·36 citations
25. 25*

    Strange electromagnetic form factors of the nucleon with $N_f=2+1$ $\mathcal{O}(a)$-improved Wilson fermions

    Dalibor Djukanovic🇩🇪 · Konstantin Ottnad🇩🇪 · Jonas Wilhelm🇩🇪 · Hartmut Wittig🇩🇪

    We present results for the strange contribution to the electromagnetic form factors of the nucleon computed on the CLS ensembles with $N_f=2+1$ flavors of $\mathcal{O}(a)$-improved Wilson fermions and an $\mathcal{O}(a)$-improved vector current. Several source-sink separations are investigated in order to estimate the excited-state contamination. We calculate the form factors on six ensembles with lattice spacings in the range of $a=0.049-0.086\text{fm}$ and pion masses in the range of $m_{\pi }=200-360\text{MeV}$, which allows for a controlled chiral and continuum extrapolation. In the computation of the quark-disconnected contributions we employ hierarchical probing as a variance reduction technique.

    ↳ hep-lathep-phnucl-thPRL(2019)·34 citations
26. 26*

    Light-cone distribution amplitudes of octet baryons from lattice QCD

    Gunnar S. Bali🇩🇪 · Vladimir M. Braun🇩🇪 · Simon Bürger🇩🇪 · Sara Collins🇩🇪 · Meinulf Göckeler🇩🇪 · Michael Gruber🇩🇪 · Fabian Hutzler🇩🇪 · Piotr Korcyl🇵🇱 · Andreas Schäfer🇩🇪 · Wolfgang Söldner🇩🇪 · André Sternbeck🇩🇪 · Philipp Wein🇩🇪

    We present lattice QCD results for the wave function normalization constants and the first moments of the distribution amplitudes for the lowest-lying baryon octet. The analysis is based on a large number of $N_f=2+1$ ensembles comprising multiple trajectories in the quark mass plane including physical pion (and kaon) masses, large volumes, and, most importantly, five different lattice spacings down to $a=0.039\mathrm{fm}$. This allows us to perform a controlled extrapolation to the continuum and infinite volume limits by a simultaneous fit to all available data. We demonstrate that the formerly observed violation of flavor symmetry breaking constraints can, indeed, be attributed to discretization effects that vanish in the continuum limit.

    ↳ hep-lathep-phEPJA(2019)·80 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.