Fri·Dec 29, 2017Friday·December 29, 2017

1. 01*

   Neutrino non-standard interactions and dark matter searches with multi-ton scale detectors

   D. Aristizabal Sierra🇨🇱 · N. Rojas🇨🇱 · M.H.G. Tytgat🇧🇪

   Future dark matter (DM) direct detection searches will be subject to irreducible neutrino backgrounds that will challenge the identification of an actual WIMP signal in experiments without directionality sensitivity. We study the impact of neutrino-quark non-standard interactions (NSI) on this background, assuming the constraints from neutrino oscillations and the recent COHERENT experiment data, which are relevant for NSI mediated by light mediators, $m_{\mathrm{med}}\lesssim \mathcal{O}$(GeV). We calculate the expected number of neutrino-nucleus elastic scattering events in a Xe-based ton-size dark matter detector, including solar neutrino fluxes from the $pp$ chain and CNO cycle as well as sub-GeV atmospheric fluxes and taking into account NSI effects in both propagation and detection. We find that sizable deviations from the standard model expectation are possible, but are more pronounced for flavor-diagonal couplings, in particular for electron neutrinos. We show that neutrino NSI can enhance or deplete the neutrino-nucleus event rate, which may impact DM searches in multi-ton detectors.

   hep-phJHEP(2018)·75 citations
2. 02*

   Rapidity Gap Survival in Enhanced Pomeron Scheme

   Sergey Ostapchenko🇩🇪 · Marcus Bleicher🇩🇪

   We apply the phenomenological Reggeon field theory framework to investigate rapidity gap survival (RGS) probability for diffractive dijet production in proton-proton collisions. In particular, we study in some detail rapidity gap suppression due to elastic rescatterings of intermediate partons in the underlying parton cascades, described by enhanced (Pomeron-Pomeron interaction) diagrams. We demonstrate that such contributions play a subdominant role, compared to the usual, so-called "eikonal", rapidity gap suppression due to elastic rescatterings of constituent partons of the colliding protons. On the other hand, the overall RGS factor proves to be sensitive to color fluctuations in the proton. Hence, experimental data on diffractive dijet production can be used to constrain the respective model approaches.

   hep-phEPJC(2018)·8 citations
3. 03*

   Mirror fermions and the strong CP problem: A new axionless solution and experimental implications

   P. Q. Hung🇺🇸

   A new solution to the strong CP problem with distinct experimental signatures (long-lived particles) at the LHC is proposed. It is based on the Yukawa interactions between mirror quarks, Standard Model (SM) quarks and Higgs singlets. (Mirror quarks and leptons which include non-sterile right-handed neutrinos whose Majorana masses are proportional to the electroweak scale, form the basis of the EW-${\nu }_R$ model.) The aforementioned Yukawa couplings can in general be complex and can contribute to $ArgDetM$ ($\bar{\theta }={\theta }_{QCD}+ArgDetM$) at tree-level. The model contains a Peccei-Quinn-type global symmetry which allows it to rotate away ${\theta }_{QCD}$.The crux of matter in this manuscript is the fact that {\em no matter how large} the CP-violating phases in the Yukawa couplings might be, $ArgDetM$ can remain small i.e. $\bar{\theta }<10^{-10}$ for reasonable values of the Yukawa couplings and, in fact, vanishes when the VEV of the Higgs singlet (responsible for the Dirac part of the neutrino mass in the seesaw mechanism) vanishes. The smallness of the contribution to $\bar{\theta }$ is {\em principally due} to the smallness of the ratio of the two mass scales in the seesaw mechanism: the Dirac and Majorana mass scales.

   hep-phhep-ex8 citations
4. 04*

   High-energy ${\mu }^{+}{\mu }^{-}$ electroproduction

   P. A. Krachkov🇷🇺 · A. I. Milstein🇷🇺

   The cross sections of high-energy ${\mu }^{+}{\mu }^{-}$ pair production and paradimuonium production by a relativistic electron in the atomic field are discussed. The calculation is performed exactly in the parameters of the atomic field. Though the Coulomb corrections to the cross sections, related to the multiple Coulomb exchange of ${\mu }^{+},{\mu }^{-}$ and an atom, are negligible, the Coulomb corrections to the differential cross sections, related to the electron interaction with an atom, are large. However, the latter Coulomb corrections to the cross sections integrated over the final electron momentum are small. Apparently, this effect can easily be observed experimentally. Furthermore, it is shown that the asymmetry of the cross section with respect to the permutation of the momenta of ${\mu }^{-}$ and ${\mu }^{+}$ is large.

   hep-phnucl-thphysics.atom-phNPA(2018)·8 citations
5. 05*

   On the Hadronic light-by-light contribution to the muon $g-2$

   Johan Bijnens (Lund)🇸🇪

   This talk is about the hadronic light-by-light contribution to the muon anomalous magnetic moment, mainly our old work but including some newer results as well. It concentrates on the model calculations. Most attention is paid to pseudo-scalar exchange and the pion loop contribution. Scalar, $a_1$-exchange and other contributions are shortly discussed as well. For the ${\pi }^0$-exchange a possible large cancellation between connected and disconnected diagrams is expected.

   hep-phEPJ Web Conf.(2018)·4 citations
6. 06*

   Reggeon cuts in QCD amplitudes with negative signature

   V.S. Fadin🇷🇺 · L.N. Lipatov🇷🇺

   Reggeon cuts in QCD amplitudes with negative signature are discussed. These cuts appear in the next-to-next-to-leading logarithmic approximation (NNLLA) and greatly complicate the derivation of the BFKL equation. Feynman diagrams responsible for appearance of these cuts are indicated and the cut contributions are calculated in the two- and three-loop approximation.

   hep-phEPJC(2018)·40 citations
7. 07*

   Higgs Portals for Thermal Dark Matter - EFT Perspectives and the NMSSM -

   Sebastian Baum🇸🇪 · Marcela Carena🇺🇸 · Nausheen R. Shah🇺🇸 · Carlos E. M. Wagner🇺🇸

   We analyze a low energy effective model of Dark Matter in which the thermal relic density is provided by a singlet Majorana fermion which interacts with the Higgs fields via higher dimensional operators. Direct detection signatures may be reduced if blind spot solutions exist, which naturally appear in models with extended Higgs sectors. Explicit mass terms for the Majorana fermion can be forbidden by a $Z_3$ symmetry, which in addition leads to a reduction of the number of higher dimensional operators. Moreover, a weak scale mass for the Majorana fermion is naturally obtained from the vacuum expectation value of a scalar singlet field. The proper relic density may be obtained by the $s$-channel interchange of Higgs and gauge bosons, with the longitudinal mode of the $Z$ boson (the neutral Goldstone mode) playing a relevant role in the annihilation process. This model shares many properties with the Next-to-Minimal Supersymmetric extension of the Standard Model (NMSSM) with light singlinos and heavy scalar and gauge superpartners. In order to test the validity of the low energy effective field theory, we compare its predictions with those of the ultraviolet complete NMSSM. Extending our framework to include $Z_3$ neutral Majorana fermions, analogous to the bino in the NMSSM, we find the appearance of a new bino-singlino well tempered Dark Matter region.

   hep-phastro-ph.COJHEP(2018)·78 citations
8. 08*

   The Heavy Quark Form Factors at Two Loops

   J. Ablinger🇦🇹 · A. Behring🇩🇪 · J. Blümlein🇩🇪 · G. Falcioni🇳🇱 · A. De Freitas🇩🇪 · P. Marquard🇩🇪 · N. Rana🇩🇪 · C. Schneider🇦🇹

   We compute the two-loop QCD corrections to the heavy quark form factors in case of the vector, axial-vector, scalar and pseudo-scalar currents up to second order in the dimensional parameter $ϵ=(4-D)/2$. These terms are required in the renormalization of the higher order corrections to these form factors.

   hep-phPRD(2018)·56 citations
9. 09*

   Dynamical Dark Matter from Thermal Freeze-Out

   Keith R. Dienes🇺🇸 · Jacob Fennick🇺🇸 · Jason Kumar🇺🇸 · Brooks Thomas🇺🇸

   In the Dynamical Dark Matter (DDM) framework, the dark sector comprises a large number of constituent dark particles whose individual masses, lifetimes, and cosmological abundances obey specific scaling relations with respect to each other. In particular, the most natural versions of this framework tend to require a spectrum of cosmological abundances which scale inversely with mass, so that dark-sector states with larger masses have smaller abundances. Thus far, DDM model-building has primarily relied on non-thermal mechanisms for abundance generation such as misalignment production, since these mechanisms give rise to abundances that have this property. By contrast, the simplest versions of thermal freeze-out tend to produce abundances that increase, rather than decrease, with the mass of the dark-matter component. In this paper, we demonstrate that there exist relatively simple modifications of the traditional thermal freeze-out mechanism which "flip" the resulting abundance spectrum, producing abundances that scale inversely with mass. Moreover, we demonstrate that a far broader variety of scaling relations between lifetimes, abundances, and masses can emerge through thermal freeze-out than through the non-thermal mechanisms previously considered for DDM ensembles. The results of this paper thus extend the DDM framework into the thermal domain and essentially allow us to "design" our resulting DDM ensembles at will in order to realize a rich array of resulting dark-matter phenomenologies.

   hep-phastro-ph.COPRD(2018)·20 citations
10. 10*

    Low-Scale Seesaw and the CP Violation in Neutrino Oscillations

    J. T. Penedo🇮🇹 · S. T. Petcov🇮🇹 · Tsutomu T. Yanagida🇯🇵

    We consider a version of the low-scale type I seesaw mechanism for generating small neutrino masses, as an alternative to the standard seesaw scenario. It involves two right-handed (RH) neutrinos ${\nu }_{1R}$ and ${\nu }_{2R}$ having a Majorana mass term with mass $M$, which conserves the lepton charge $L$. The RH neutrino ${\nu }_{2R}$ has lepton-charge conserving Yukawa couplings $g_{\ell 2}$ to the lepton and Higgs doublet fields, while small lepton-charge breaking effects are assumed to induce tiny lepton-charge violating Yukawa couplings $g_{\ell 1}$ for ${\nu }_{1R}$, $l=e,\mu ,\tau$. In this approach the smallness of neutrino masses is related to the smallness of the Yukawa coupling of ${\nu }_{1R}$ and not to the large value of $M$: the RH neutrinos can have masses in the few GeV to a few TeV range. The Yukawa couplings $|g_{\ell 2}|$ can be much larger than $|g_{\ell 1}|$, of the order $|g_{\ell 2}|\sim 10^{-4}-10^{-2}$, leading to interesting low-energy phenomenology. We consider a specific realisation of this scenario within the Froggatt-Nielsen approach to fermion masses. In this model the Dirac CP violation phase $\delta$ is predicted to have approximately one of the values $\delta \simeq \pi /4,3\pi /4$, or $5\pi /4,7\pi /4$, or to lie in a narrow interval around one of these values. The low-energy phenomenology of the considered low-scale seesaw scenario of neutrino mass generation is also briefly discussed.

    hep-phNPB(2018)·24 citations
11. 11*

    Top and Higgs: Recent Theory developments

    Eleni Vryonidou🇨🇭

    I review recent theory developments in the computation of Higgs production in association with top quarks, as well as the modelling of the corresponding backgrounds. In addition to progress within the Standard model I discuss higher-order corrections for the $t\bar{t}H$ process in the presence of new interactions.

    hep-ph0 citations
12. 12*

    Probing the CP properties of top Yukawa coupling at an $e^{+}{e}^{-}$ collider

    Kaoru Hagiwara🇯🇵 · Hiroshi Yokoya🇰🇷 · Ya-Juan Zheng🇯🇵

    We study consequences of CP violation in the $ht\bar{t}$ Yukawa coupling through the process $e^{+}{e}^{-}\to$ $h(125)t\bar{t}$. The helicity amplitudes are calculated in the $t\bar{t}$ rest frame, where the initial $e^{+}{e}^{-}$ current and the final Higgs boson have the same three-momentum. CP-violating asymmetries appear not only in the azimuthal angle between the $e^{+}{e}^{-}$ plane and the $t\bar{t}$ plane about the Higgs momentum direction, but also in the correlated decay angular distributions of $t$ and $\bar{t}$. Complete description of the production and decay angular distributions are obtained analytically, including both leptonic and hadronic decays of $t$ and $\bar{t}$. We study the ultimate sensitivity to the CP-violating $ht\bar{t}$ coupling at a few center-of-mass energies. Our analysis shows that the possibility of discovering CP violating $ht\bar{t}$ coupling improves significantly by studying $t\bar{t}$ decay angular correlations, and more importantly, by increasing its energy upgrade target from $\sqrt{s}=500$ GeV to 550 GeV.

    hep-phJHEP(2018)·29 citations
13. 13*

    Multifield Reheating after Modular $j$-Inflation

    Rolf Schimmrigk🇺🇸

    In the inflationary framework of cosmology the initial phase of rapid expansion has to be followed by a reheating stage, which is envisioned to end in a radiation dominated big bang. Key parameters that characterize this big bang state are the temperature at the end of the reheating stage and the baryon asymmetry. For general interacting theories these parameters are difficult to obtain analytically because of the involved structure of the potential. In this paper multifield reheating is considered for interacting theories in which the inflaton trajectory is weakly curved. This scenario is realized in the model of $j$-inflation, a particular example of modular inflation, allowing an estimate of the reheat temperature.

    hep-phastro-ph.COhep-thPLB(2018)·16 citations
14. 14*

    Fragmentation function of gluon into spin-singlet $P$-wave quarkonium

    Feng Feng🇨🇳 · Saadi Ishaq🇨🇳 · Yu Jia🇨🇳 · Jia-Yue Zhang🇨🇳

    Following the operator definition of the fragmentation function developed by Collins and Soper, we compute the gluon-to-$h_c$ fragmentation function at the lowest order in the velocity expansion in NRQCD factorization approach. Utilizing some modern technique developed in the area of multi-loop calculation, we are able to analytically deduce the infrared-finite color-singlet short-distance coefficient associated with the fragmentation function. The fragmentation probability for gluon into $h_c$ is estimated to be order $10^{-6}$.

    hep-phPRD(2020)·10 citations
15. 15*

    Flavor-specific scalar mediators

    Brian Batell🇺🇸 · Ayres Freitas🇺🇸 · Ahmed Ismail🇺🇸 · David McKeen🇺🇸

    New singlet scalar bosons have broad phenomenological utility and feature prominently in many extensions of the Standard Model. Such scalars are often taken to have Higgs-like couplings to SM fermions in order to evade stringent flavor bounds, e.g. by assuming Minimal Flavor Violation (MFV), which leads to a rather characteristic phenomenology. Here we describe an alternative approach, based on an effective field theory framework for a new scalar that dominantly couples to one specific SM fermion mass eigenstate. A simple flavor hypothesis ensures adequate suppression of new flavor changing neutral currents. We consider radiatively generated flavor changing neutral currents and scalar potential terms in such theories, demonstrating that they are often suppressed by small Yukawa couplings, and also describe the role of $CP$ symmetry. We further demonstrate that such scalars can have masses that are significantly below the electroweak scale while still being natural, provided they are sufficiently weakly coupled to ordinary matter. In comparison to other flavor scenarios, our framework is rather versatile since a single (or a few) desired scalar couplings may be investigated in isolation. We illustrate this by discussing in detail the examples of an up-specific scalar mediator to dark matter and a muon-specific scalar that may address the $\sim 3\sigma$ muon anomalous magnetic moment discrepancy.

    hep-phhep-exPRD(2018)·127 citations
16. 16*

    Dark energy, $\alpha$-attractors, and large-scale structure surveys

    Yashar Akrami🇳🇱 · Renata Kallosh🇺🇸 · Andrei Linde🇺🇸 · Valeri Vardanyan🇳🇱

    Over the last few years, a large family of cosmological attractor models has been discovered, which can successfully match the latest inflation-related observational data. Many of these models can also describe a small cosmological constant $\Lambda$, which provides the most natural description of the present stage of the cosmological acceleration. In this paper, we study $\alpha$-attractor models with dynamical dark energy, including the cosmological constant $\Lambda$ as a free parameter. Predominantly, the models with $\Lambda >0$ converge to the asymptotic regime with the equation of state $w=-1$. However, there are some models with $w\ne -1$, which are compatible with the current observations. In the simplest models with $\Lambda =0$, one has the tensor to scalar ratio $r=\frac{12\alpha }{N^2}$ and the asymptotic equation of state $w=-1+\frac{2}{9\alpha }$ (which in general differs from its present value). For example, in the seven disk M-theory related model with $\alpha =7/3$ one finds $r\sim 10^{-2}$ and the asymptotic equation of state is $w\sim -0.9$. Future observations, including large-scale structure surveys as well as B-mode detectors will test these, as well as more general models presented here. We also discuss gravitational reheating in models of quintessential inflation and argue that its investigation may be interesting from the point of view of inflationary cosmology. Such models require a much greater number of $e$-folds, and therefore predict a spectral index $n_s$ that can exceed the value in more conventional models by about $0.006$. This suggests a way to distinguish the conventional inflationary models from the models of quintessential inflation, even if they predict $w=-1$.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2018)·164 citations
17. 17*

    Primordial Black Holes from Polynomial Potentials in Single Field Inflation

    Mark P. Hertzberg🇺🇸 · Masaki Yamada🇺🇸

    Within canonical single field inflation models, we provide a method to reverse engineer and reconstruct the inflaton potential from a given power spectrum. This is not only a useful tool to find a potential from observational constraints, but also gives insight into how to generate a large amplitude spike in density perturbations, especially those that may lead to primordial black holes (PBHs). In accord with other works, we find that the usual slow-roll conditions need to be violated in order to generate a significant spike in the spectrum. We find that a way to achieve a very large amplitude spike in single field models is for the classical roll of the inflaton to over-shoot a local minimum during inflation. We provide an example of a quintic polynomial potential that implements this idea and leads to the observed spectral index, observed amplitude of fluctuations on large scales, significant PBH formation on small scales, and is compatible with other observational constraints. We quantify how much fine-tuning is required to achieve this in a family of random polynomial potentials, which may be useful to estimate the probability of PBH formation in the string landscape.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2018)·194 citations
18. 18*

    Sensitivity to anomalous $ZZH$ couplings at the International Linear Collider

    Tomohisa Ogawa🇯🇵 · Junping Tian🇯🇵 · Keisuke Fujii🇯🇵

    This presentation gives the prospects of measuring the general Lorentz structures of $VVH$ ($V=Z$, $\gamma$ and $W$) couplings at the International Linear Collider (ILC). Sensitivities to Higgs CP-even and CP-odd structures are evaluated by using various Higgs production channels and employing measurements of kinematical distributions. The evaluation is performed based on full detector simulation of the International Large Detector (ILD) at center-of-mass energies $\sqrt{s}=$ 250 and 500 GeV. Combined sensitivities on the anomalous $ZZH$ couplings are provided for a realistic operating scenario of the ILC.

    ↳ hep-exhep-phPoS(2017)·7 citations
19. 19*

    $K\to \pi$ matrix elements of the chromomagnetic operator on the lattice

    M. Constantinou🇺🇸 · M. Costa🇨🇾 · R. Frezzotti🇮🇹 · V. Lubicz🇮🇹 · G. Martinelli🇮🇹 · D. Meloni🇮🇹 · H. Panagopoulos🇨🇾 · S. Simula🇮🇹

    We present the results of the first lattice QCD calculation of the $K\to \pi$ matrix elements of the chromomagnetic operator $O_{CM}=g\bar{s}{\sigma }_{\mu \nu }{G}_{\mu \nu }d$, which appears in the effective Hamiltonian describing $\Delta S=1$ transitions in and beyond the Standard Model. Having dimension 5, the chromomagnetic operator is characterized by a rich pattern of mixing with operators of equal and lower dimensionality. The multiplicative renormalization factor as well as the mixing coefficients with the operators of equal dimension have been computed at one loop in perturbation theory. The power divergent coefficients controlling the mixing with operators of lower dimension have been determined non-perturbatively, by imposing suitable subtraction conditions. The numerical simulations have been carried out using the gauge field configurations produced by the European Twisted Mass Collaboration with $N_f=2+1+1$ dynamical quarks at three values of the lattice spacing. Our result for the B-parameter of the chromomagnetic operator at the physical pion and kaon point is $B_{CMO}^{K\pi }=0.273(70)$, while in the SU(3) chiral limit we obtain $B_{CMO}=0.072(22)$. Our findings are significantly smaller than the model-dependent estimate $B_{CMO}\sim 1-4$, currently used in phenomenological analyses, and improve the uncertainty on this important phenomenological quantity.

    ↳ hep-lathep-phPRD(2018)·26 citations
20. 20*

    Resurrecting Quartic and Quadratic inflaton potentials in two-field inflationary model

    Suratna Das🇮🇳 · Girish Kumar Chakravarty🇮🇳 · Gaetano Lambiase🇮🇹 · Subhendra Mohanty🇮🇳

    After the release of the PLANCK data, it is evident that inflationary paradigm has stood the test of time. Even though, it is difficult to realise inflationary paradigm in a particle physics model as the present observations have ruled out the simplest quartic and quadratic inflationary potentials, which generically arise in particle physics. We would show that such simplest inflationary potentials can evade discrepancies with observations, if the inflaton field is assisted by another scalar during inflation. Moreover, unlike other multifield models, our model yields no isocurvature perturbations and negligible non-Gaussianity, making it more compatible with the present data. Above all, our model can also be realised in the framework of SUGRA.

    ↳ astro-ph.COhep-phAIP Conf.Proc.(2019)·0 citations
21. 21*

    Localization of $U(1)$ gauge vector field on flat branes with five-dimension (asymptotic) AdS${}_5$ spacetime

    Zhen-Hua Zhao🇨🇳 · Qun-Ying Xie🇨🇳

    In order to localize $U(1)$ gauge vector field on Randall-Sundrum-like braneworld model with infinite extra dimension, we propose a new kind of non-minimal coupling between the $U(1)$ gauge field and the gravity. We propose three kinds of coupling methods and they all support the localization of zero mode. In addition, one of them can support the localization of massive modes. Moreover, the massive tachyonic modes can be excluded. And our method can be used not only in the thin braneword models but also in the thick ones.

    ↳ hep-thgr-qchep-phJHEP(2018)·17 citations
22. 22*

    Search for magnetic monopoles with the MoEDAL forward trapping detector in 2.11 fb${}^{-1}$ of 13 TeV proton-proton collisions at the LHC

    MoEDAL Collaboration: B. Acharya🇬🇧 · J. Alexandre🇬🇧 · S. Baines🇬🇧 · P. Benes🇨🇿 · B. Bergmann🇨🇿 · J. Bernabéu🇪🇸 · A. Bevan🇬🇧 · H. Branzas🇷🇴 · M. Campbell🇨🇭 · L. Caramete🇷🇴 · S. Cecchini🇮🇹 · M. de Montigny🇨🇦 and 58 other authors

    We update our previous search for trapped magnetic monopoles in LHC Run 2 using nearly six times more integrated luminosity and including additional models for the interpretation of the data. The MoEDAL forward trapping detector, comprising 222~kg of aluminium samples, was exposed to 2.11~fb${}^{-1}$ of 13 TeV proton-proton collisions near the LHCb interaction point and analysed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to the Dirac charge or above are excluded in all samples. The results are interpreted in Drell-Yan production models for monopoles with spins 0, 1/2 and 1: in addition to standard point-like couplings, we also consider couplings with momentum-dependent form factors. The search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge.

    ↳ hep-exhep-phPLB(2018)·86 citations
23. 23*

    Exact Solutions to Non-Linear Symmetron Theory: One and Two Mirror Systems

    Philippe Brax🇫🇷 · Mario Pitschmann🇦🇹

    We derive the exact analytical solutions to the symmetron field theory equations in the presence of a one or two mirror system. The one dimensional equations of motion are integrated exactly for both systems and their solutions can be expressed in terms of Jacobi elliptic functions. Surprisingly, in the case of two parallel mirrors the equations of motion generically provide not a unique solution but a discrete set of solutions with increasing number of nodes and energies. The solutions obtained herein can be applied to qBOUNCE experiments, neutron interferometry and for the calculation of the symmetron field induced "Casimir force" in the CANNEX experiment.

    ↳ gr-qcastro-ph.COhep-phPRD(2018)·45 citations
24. 24*

    Cosmic Microwave Background Dipole Asymmetry could be explained by Axion Monodromy Cosmic Strings

    Qiaoli Yang🇨🇳 · Hongbiao Yu🇨🇳 · Haoran Di🇨🇳

    Observations by the Wilkinson Microwave Anisotropy Probe and the Planck mission suggest a hemispherical power amplitude asymmetry in the cosmic microwave background, with a correlation length on the order of the size of the observable Universe. We find that this anomaly can be naturally explained by an axion-like particle (ALP) cosmic string formed near our visible Universe. The field variation associated to this cosmic string creates particle density fluctuations after inflation, which consequently decay into radiation before the Big Bang Nucleosynthesis (BBN) era and resulted in the observed power asymmetry. We find in this scenario that the hemispherical power amplitude asymmetry is strongly scale dependent: $A(k)\propto \exp (-kl)/k$. Admittedly, typical inflation models predict a relic number density of topological defects of order one per observable Universe and so in our model the cosmic string must be tuned to have an impact factor of order $1/H_0$. Interestingly, the constraints based on purely cosmological considerations also give rise to a Peccei-Quinn scale $F_a$ of order $10^3$ larger then the Hubble scale of inflation $H_I$. Assuming $H_I\sim 10^{13}$GeV, we then have an ALP with $F_a\sim 10^{16}$GeV, which coincides with the presumed scale of grand unification. As we require ALP decays occur before the BBN era, which implies a relatively heavy mass or strong self-coupling, and considering that the associated potential should break the shift symmetry softly in order to protect the system from radiative corrections, we also conclude that the required ALP potential should be monodromic in nature.

    ↳ astro-ph.COgr-qchep-phhep-thPhys.Dark Univ.(2019)·6 citations
25. 25*

    Holographic CBK Relation

    Gregory Gabadadze🇺🇸 · Giorgi Tukhashvili🇺🇸

    The Crewther-Broadhurst-Kataev (CBK) relation connects the Bjorken function for deep-inelastic sum rules (or the Gross - Llewellyn Smith function) with the Adler function for electron-positron annihilation in QCD; it has been checked to hold up to four loops in perturbation theory. Here we study non-perturbative terms in the CBK relation using a holographic dual theory that is believed to capture properties of QCD. We show that for the large invariant momenta the perturbative CBK relation is exactly satisfied. For the small momenta non-perturbative corrections enter the relation and we calculate their significant effects. We also give an exact holographic expression for the Bjorken function, as well as for the entire three-point axial-vector-vector correlation function, and check their consistency in the conformal limit.

    ↳ hep-thhep-phPLB(2018)·3 citations
26. 26*

    Improving the theoretical prediction for the $B_s-{\bar{B}}_s$ width difference: matrix elements of next-to-leading order $\Delta B=2$ operators

    Christine Davies🇬🇧 · Judd Harrison🇬🇧 · G Peter Lepage🇺🇸 · Christopher Monahan🇺🇸 · Junko Shigemitsu🇺🇸 · Matthew Wingate🇬🇧

    We present lattice QCD results for the matrix elements of $R_2$ and other dimension-7, $\Delta B=2$ operators relevant for calculations of $\Delta {\Gamma }_s$, the $B_s-{\bar{B}}_s$ width difference. We have computed correlation functions using 5 ensembles of the MILC Collaboration's 2+1+1-flavour gauge field configurations, spanning 3 lattice spacings and light sea quarks masses down to the physical point. The HISQ action is used for the valence strange quarks, and the NRQCD action is used for the bottom quarks. Once our analysis is complete, the theoretical uncertainty in the Standard Model prediction for $\Delta {\Gamma }_s$ will be substantially reduced.

    ↳ hep-lathep-phEPJ Web Conf.(2018)·7 citations
27. 27*

    Low-Energy Effective Field Theory of Lepton-Proton Bremsstrahlung

    P. Talukdar🇮🇳 · F. Myhrer🇺🇸 · U. Raha🇮🇳

    We calculate the cross section for the lepton-proton bremsstrahlung process $l+p\to l^{\prime }+p+\gamma$ in effective field theory. This process corresponds to an undetected background signal for the proposed MUSE experiment at PSI. MUSE is designed to measure elastic scattering of low-energy electrons and muons off a proton target in order to extract a precise value for the proton's r.m.s. radius. We show that the commonly used {\it peaking approximation}, which is used to evaluate the {\it radiative tail} for the elastic cross section, is not applicable for muon proton scattering at the low-energy MUSE kinematics. We also correct a misprint in a commonly cited review article.

    ↳ nucl-thhep-ph5 citations
28. 28*

    Cannonball model diagnosis of the short gamma ray burst 170817A

    Shlomo Dado🇮🇱 · Arnon Dar🇮🇱 · Alvaro De Rujula🇪🇸

    The rich and complex data obtained from multi-wavelength observations of SHB170817A, the short hard gamma ray burst (SHB) associated with GW170817 --the first neutron stars merger event detected in gravitational waves (GWs)-- are analyzed in the framework of the cannonball model of SHBs. In this model a highly relativistic jet is launched by fall back matter on the nascent neutron star (or black hole) into a surrounding glory (light from the surrounding wind nebula of the binary neutron stars) which was present already before the merger. The SHB was produced by inverse Compton scattering of glory photons by the jet, which was viewed far off-axis. The fading glory, which produced the initial UVOIR afterglow, was powered by a neutron star remnant. It was overtaken by a late time X-ray, UVOIR and radio afterglow produced by synchrotron radiation from the decelerating jet in the interstellar medium of the host galaxy. If the radio afterglow of SHB170817A was indeed produced by the jet, it should display a superluminal motion relative to the SHB location, still detectable in VLA and VLBI radio observations.

    ↳ astro-ph.HEhep-phhep-th7 citations
29. 29*

    Low-luminosity gamma-ray bursts as the sources of ultrahigh-energy cosmic ray nuclei

    B. Theodore Zhang🇨🇳 · Kohta Murase🇺🇸 · Shigeo S. Kimura🇺🇸 · Shunsaku Horiuchi🇺🇸 · Peter Mészáros🇺🇸

    Recent results from the Pierre Auger Collaboration have shown that the composition of ultrahigh-energy cosmic rays (UHECRs) becomes gradually heavier with increasing energy. Although gamma-ray bursts (GRBs) have been promising sources of UHECRs, it is still unclear whether they can account for the Auger results because of their unknown nuclear composition of ejected UHECRs. In this work, we revisit the possibility that low-luminosity GRBs (LL GRBs) act as the sources of UHECR nuclei, and give new predictions based on the intrajet nuclear composition models considering progenitor dependencies. We find that the nuclear component in the jet can be divided into two groups according to the mass fraction of silicon nuclei, Si-free and Si-rich. Motivated by the connection between LL GRBs and transrelativistic supernovae, we also consider the hypernova ejecta composition. Then, we discuss the survivability of UHECR nuclei in the jet base and internal shocks of the jets, and show that it is easier for nuclei to survive for typical LL GRBs. Finally, we numerically propagate UHECR nuclei ejected from LL GRBs with different composition models and compare the resulting spectra and composition to Auger data. Our results show that both the Si-rich progenitor and hypernova ejecta models match the Auger data well, while the Si-free progenitor models have more difficulty in fitting the spectrum. We argue that our model is consistent with the newly reported cross correlation between the UHECRs and starburst galaxies, since both LL GRBs and hypernovae are expected to be tracers of the star-formation activity. LL GRBs have also been suggested as the dominant origin of IceCube neutrinos in the PeV range, and the LL GRB origin of UHECRs can be critically tested by near-future multimessenger observations.

    ↳ astro-ph.HEastro-ph.SRhep-phnucl-thPRD(2018)·114 citations
30. 30*

    One-Loop Integrals from Spherical Projections of Planes and Quadrics

    Nima Arkani-Hamed🇺🇸 · Ellis Ye Yuan🇺🇸

    We initiate a systematic study of one-loop integrals by investigating the connection between their singularity structures and geometric configurations in the projective space associated to their Feynman parametrization. We analyze these integrals by two recursive methods, which leads to two independent algebraic algorithms that determine the symbols of any one-loop integrals in arbitrary spacetime dimensions. The discontinuities of Feynman diagrams are shown to arise from taking certain "spherical contour" residues in Feynman parameter space, which is geometrically interpreted as a projection of the quadric surface (associated to the Symanzik polynomial at one loop) through faces of the integration region (which is a simplex). This geometry also leads to a manifestly Lorentz-invariant understanding for perturbative unitarity at one loop.

    ↳ hep-thhep-ph61 citations
31. 31*

    AdS backgrounds and induced gravity

    Hai Lin🇨🇳 · Gaurav Narain🇨🇳

    In this paper we look for AdS solutions to generalised gravity theories in the bulk in various spacetime dimensions. The bulk gravity action includes the action of a non-minimally coupled scalar field with gravity, and a higher-derivative action of gravity. The usual Einstein-Hilbert gravity is induced when the scalar acquires a non-zero vacuum expectation value. The equation of motion in the bulk shows scenarios where AdS geometry emerges on-shell. We further obtain the action of the fluctuation fields on the background at quadratic and cubic orders.

    ↳ hep-thgr-qchep-phMod.Phys.Lett.A(2019)·5 citations
32. 32*

    Gauge-invariant screening masses and static quark free energies in $N_f=2+1$ QCD at non-zero baryon density

    Michele Andreoli🇮🇹 · Claudio Bonati🇮🇹 · Massimo D'Elia🇮🇹 · Michele Mesiti🇬🇧 · Francesco Negro🇮🇹 · Andrea Rucci🇮🇹 · Francesco Sanfilippo🇮🇹

    We discuss the extension of gauge-invariant electric and magnetic screening masses in the Quark-Gluon Plasma to the case of a finite baryon density, defining them in terms of a matrix of Polyakov loop correlators. We present lattice results for $N_f=2+1$ QCD with physical quark masses, obtained using the imaginary chemical potential approach, which indicate that the screening masses increase as a function of ${\mu }_B$. A separate analysis is carried out for the theoretically interesting case ${\mu }_B/T=3i\pi$, where charge conjugation is not explicitly broken and the usual definition of the screening masses can be used for temperatures below the Roberge-Weiss transition. Finally, we investigate the dependence of the static quark free energy on the baryon chemical potential, showing that it is a decreasing function of ${\mu }_B$ which displays a peculiar behavior as the pseudocritical transition temperature at ${\mu }_B=0$ is approached.

    ↳ hep-lathep-phhep-thPRD(2018)·15 citations
33. 33*

    Revisiting non-Gaussianity from non-attractor inflation models

    Yi-Fu Cai🇨🇳 · Xingang Chen🇺🇸 · Mohammad Hossein Namjoo🇺🇸 · Misao Sasaki🇯🇵 · Dong-Gang Wang🇳🇱 · Ziwei Wang🇨🇳

    Non-attractor inflation is known as the only single field inflationary scenario that can violate non-Gaussianity consistency relation with the Bunch-Davies vacuum state and generate large local non-Gaussianity. However, it is also known that the non-attractor inflation by itself is incomplete and should be followed by a phase of slow-roll attractor. Moreover, there is a transition process between these two phases. In the past literature, this transition was approximated as instant and the evolution of non-Gaussianity in this phase was not fully studied. In this paper, we follow the detailed evolution of the non-Gaussianity through the transition phase into the slow-roll attractor phase, considering different types of transition. We find that the transition process has important effect on the size of the local non-Gaussianity. We first compute the net contribution of the non-Gaussianities at the end of inflation in canonical non-attractor models. If the curvature perturbations keep evolving during the transition - such as in the case of smooth transition or some sharp transition scenarios - the $\mathcal{O}(1)$ local non-Gaussianity generated in the non-attractor phase can be completely erased by the subsequent evolution, although the consistency relation remains violated. In extremal cases of sharp transition where the super-horizon modes freeze immediately right after the end of the non-attractor phase, the original non-attractor result can be recovered. We also study models with non-canonical kinetic terms, and find that the transition can typically contribute a suppression factor in the squeezed bispectrum, but the final local non-Gaussianity can still be made parametrically large.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2018)·184 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.