Wed·Jan 22, 2020Wednesday·January 22, 2020

1. 01*

   Randomness-Assisted Exponential Hierarchies

   Adam Tropper🇺🇸 · JiJi Fan🇺🇸

   Inspired by the localization phenomenon in condensed matter systems, we explore constructions in the theory space of multiple scalar fields, in which exponentially suppressed couplings could originate from random parameters. In particular, we find a new class of non-local theory space models, in which scalar fields at non-adjacent sites interact with each other but with strengths decaying exponentially with the site separation. Such a model could have very different localization properties, compared to the local theory space scenarios with only nearest-site interactions, based on the original Anderson localization model. More specifically, we find that a particular non-local interaction pattern leads to bi-localization of the two lightest eigenstates. Exponential localization (and thus exponentially suppressed couplings) then emerges only and immediately when randomness is introduced, no matter how tiny it is. We discuss variants of the model and possible UV completions as well.

   hep-phcond-mat.dis-nnhep-thPRD(2021)·10 citations
2. 02*

   Measuring the top energy asymmetry at the LHC: QCD and SMEFT interpretations

   Alexander Basan🇩🇪 · Peter Berta🇩🇪 · Lucia Masetti🇩🇪 · Eleni Vryonidou🇨🇭 · Susanne Westhoff🇩🇪

   The energy asymmetry in top-antitop-jet production is an observable of the top charge asymmetry designed for the LHC. We perform a realistic analysis in the boosted kinematic regime, including effects of the parton shower, hadronization and expected experimental uncertainties. Our predictions at particle level show that the energy asymmetry in the Standard Model can be measured with a significance of $3\sigma$ during Run 3, and with more than $5\sigma$ significance at the HL-LHC. Beyond the Standard Model the energy asymmetry is a sensitive probe of new physics with couplings to top quarks. In the framework of the Standard Model Effective Field Theory, we show that the sensitivity of the energy asymmetry to effective four-quark interactions is higher or comparable to other top observables and resolves blind directions in current LHC fits. We suggest to include the energy asymmetry as an important observable in global searches for new physics in the top sector.

   hep-phhep-exJHEP(2020)·17 citations
3. 03*

   Pion Parton Distribution Function in Light-Front Holographic QCD

   Lei Chang🇨🇳 · Khépani Raya🇨🇳 · Xiaobin Wang🇨🇳

   The valence-quark distribution function of the pion has been of interest for decades; particularly, the profile it should adopt when $x\to 1$ (the large-$x$ behavior) is subject of a long-standing debate. In the light-front holographic QCD (LFHQCD) approach, this behavior is controlled by the so called reparametrization function, $w_{\tau }(x)$, which is not fully determined from first principles. We show that, owing to the flexibility of $w_{\tau }(x)$, the large-$x$ profile $u^{\pi }(x)\sim (1-x{)}^2$ can be contained within the LFHQCD formalism. This is in contrast with a previous LFHQCD study~(Guy F. de Teramond et al., Phys. Rev. Lett., 120(18), 2018) in which $u^{\pi }(x)\sim (1-x{)}^1$ is found instead. Given our observations, augmented by perturbative QCD and recent lattice QCD results, we state that the large-$x$ exponent of "2" cannot be excluded.

   hep-phCPC(2020)·30 citations
4. 04*

   Effective field theory approach to lepton number violating decays $K^{\pm }\to {\pi }^{\mp }{l}_{\alpha }^{\pm }{l}_{\beta }^{\pm }$: long-distance contribution

   Yi Liao (Nankai U., CHEP Peking U.)🇨🇳 · Xiao-Dong Ma (Taiwan U.)🇹🇼 · Hao-Lin Wang (Nankai U.)🇨🇳

   This is a sequel to our recent work [1] in which we calculated the lepton number violating (LNV) $K^{\pm }$ decays due to contact dimension-9 (dim-9) quark-lepton effective interactions that are induced at a high energy scale. In this work we investigate the long-distance contribution to the decays arising from the exchange of a neutrino. These decays can probe LNV interactions involving the second generation of fermions that are not reachable in nuclear neutrinoless double-$\beta$ decays. Our study is completely formulated in the framework of effective field theories (EFTs), from the standard model effective field theory (SMEFT) through the low energy effective field theory (LEFT) to chiral perturbation theory. We work to the first nontrivial orders in each effective field theory, collect along the way the matching conditions and renormalization group effects, and express the decay branching ratios in terms of the Wilson coefficients associated with the dim-5 and dim-7 operators in SMEFT. Our result is general in that it does not depend on dynamical details of physics at a high scale that induce the effective interactions in SMEFT and in that it does not appeal to any hadronic models. We find that the long-distance contribution overwhelmingly dominates over the contact or short-distance one. Assuming the new physics scale to be around a TeV, the branching ratios are predicted to be below the current experimental upper bounds by several orders of magnitude.

   hep-phJHEP(2020)·23 citations
5. 05*

   Realization of the minimal extended seesaw mechanism and the $T{M}_2$ type neutrino mixing

   R. Krishnan🇮🇳 · Ananya Mukherjee🇮🇳 · Srubabati Goswami🇮🇳

   We construct a neutrino mass model based on the flavour symmetry group $A_4\times C_4\times C_6\times C_2$ which accommodates a light sterile neutrino in the minimal extended seesaw (MES) scheme. Besides the flavour symmetry, we introduce a $U(1)$ gauge symmetry in the sterile sector and also impose CP symmetry. The vacuum alignments of the scalar fields in the model spontaneously break these symmetries and lead to the construction of the fermion mass matrices. With the help of the MES formulas, we extract the light neutrino masses and the mixing observables. In the active neutrino sector, we obtain the ${\text{TM}}_2$ mixing pattern with non-zero reactor angle and broken $\mu$-$\tau$ reflection symmetry. We express all the active and the sterile oscillation observables in terms of only four real model parameters. Using this highly constrained scenario we predict ${\sin }^2{\theta }_{23}=0.545_{-0.004}^{+0.003}$, $\sin \delta =-0.911_{-0.005}^{+0.006}$, $|U_{e4}{|}^2=0.029_{-0.008}^{+0.009}$, $|U_{\mu 4}{|}^2=0.010_{-0.003}^{+0.003}$ and $|U_{\tau 4}{|}^2=0.006_{-0.002}^{+0.002}$ which are consistent with the current data.

   hep-phJHEP(2020)·18 citations
6. 06*

   Revamped Bi-Large neutrino mixing with Gatto-Sartori-Tonin like relation

   Subhankar Roy🇮🇳 · K. Sashikanta Singh🇮🇳 · Jyotirmoi Borah🇮🇳

   The Gatto Sartori Tonin (GST) relation which establishes the Cabibbo angle in terms of the quark mass ratio: ${\theta }_C=\sqrt{m_d/m_s}$, is instituted as ${\theta }_{13}=\sqrt{m_1/m_3}$ to a Bi-large motivated lepton mixing framework that relies on the unification of mixing parameters: ${\theta }_{13}={\theta }_C$ and ${\theta }_{12}={\theta }_{23}$. This modification in addition to ruling out the possibility of vanishing ${\theta }_{13}$, advocates for a nonzero lowest neutrino mass and underlines the normal ordering of the neutrino masses. The framework is further enhanced by the inclusion of a charged lepton diagonalizing matrix $U_{lL}$ with $({\theta }_{12}^l\sim {\theta }_C,\delta =0)$. The model being architected at the Grand unification theory (GUT) scale is further run down upto the $Z$ boson scale to understand the universality of the GST relation and the Cabibbo angle.

   hep-phNPB(2020)·4 citations
7. 07*

   Off-shell renormalization in the presence of dimension 6 derivative operators. III. Operator mixing and $\beta$ functions

   D. Binosi🇮🇹 · A. Quadri🇮🇹

   We evaluate the one-loop $\beta$ functions of all dimension 6 parity-preserving operators in the Abelian Higgs-Kibble model. No on-shell restrictions are imposed; and the (generalized) non-polynomial field redefinitions arising at one-loop order are fully taken into account. The operator mixing matrix is also computed, and its cancellation patterns explained as a consequence of the functional identities of the theory and power-counting conditions.

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

   Two-loop radiative seesaw, muon $g-2$, and $\tau$-lepton-flavor violation with DM constraints

   Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇰🇷

   The quartic scalar coupling ${\lambda }_5$ term, which violates the lepton-number by two units in the Ma-model, is phenomenologically small when the model is applied to the lepton-flavor violation (LFV) processes. In order to dynamically generate the ${\lambda }_5$ parameter through quantum loop effects and retain the dark matter (DM) candidate, we extend the Ma-model by adding a $Z_2$-odd vector-like lepton doublet and a $Z_2$-even Majorana singlet. With the new couplings to the Higgs and gauge bosons, the observed DM relic density can be explained when the upper limits from the DM-nucleon scattering cross sections are satisfied. In addition to the neutrino data and LFV constraints, it is found that the DM relic density can significantly exclude the free parameter space. Nevertheless, the resulting muon $g-2$ mediated by the inert charged-Higgs can fit the $4.2\sigma$ deviation between the experimental measurement and the SM result, and the branching ratio for $\tau \to \mu \gamma$ can be as large as the current upper limit when the rare $\mu \to (e\gamma ,3e)$ decays are suppressed. In addition, it is found that the resulting $BR(\tau \to \mu \rho )$ can reach the sensitivity of Belle II with an integrated luminosity of 50 $a{b}^{-1}$.

   hep-phhep-exJHEP(2021)·10 citations
9. 09*

   Revealing neutrino nature and $CPT$ violation with decoherence effects

   Luca Buoninfante🇯🇵 · Antonio Capolupo🇮🇹 · Salvatore M. Giampaolo🇭🇷 · Gaetano Lambiase🇮🇹

   We study decoherence effects on mixing among three generations of neutrinos. We show that in presence of a non--diagonal dissipation matrix, both Dirac and Majorana neutrinos can violate the $CPT$ symmetry and the oscillation formulae depend on the parametrization of the mixing matrix. We reveal the $CP$ violation in the transitions preserving the flavor, for a certain form of the dissipator. In particular, the $CP$ violation affects all the transitions in the case of Majorana neutrinos, unlike Dirac neutrinos which still preserve the $CP$ symmetry in one of the transitions flavor preserving. This theoretical result shows that decoherence effects, if exist for neutrinos, could allow to determine the neutrino nature and to test fundamental symmetries of physics. Next long baseline experiments could allow such an analysis. We relate our study with experiments by using the characteristic parameters and the constraints on the elements of the dissipation matrix of current experiments.

   hep-phhep-thEPJC(2020)·40 citations
10. 10*

    Probing Jet Medium Interactions via $Z$($H$)+jet Momentum Imbalances

    Lin Chen🇨🇳 · Shu-Yi Wei🇮🇹 · Han-Zhong Zhang🇨🇳

    Different types of high energy hard probes are used to extract the jet transport properties of the Quark-Gluon Plasma created in heavy-ion collisions, of which the heavy boson tagged jets are undoubtedly the most sophisticated due to its clean decay signature and production mechanism. In this study, we used the resummation improved pQCD approach with high order correction in the hard factor to calculate the momentum ratio $x_J$ distributions of $Z$ and Higgs($H$) tagged jets. We found that the formalism can provide a good description of the 5.02 TeV $pp$ data. Using the BDMPS energy loss formalism, along with the OSU 2+1D hydro to simulate the effect of the medium, we extracted the value of the jet transport coefficient to be around ${\hat{q}}_0=4\sim 8Ge{V}^2/fm$ by comparing with the $Z$+jet $PbPb$ experimental data. The $H$+jet $x_J$ distribution were calculated in a similar manner in contrast and found to have a stronger Sudakov effect as compared with the $Z$+jet distribution. This study uses a clean color-neutral boson as trigger to study the jet quenching effect and serves as a complimentary method in the extraction of the QGP's transport coefficient in high energy nuclear collisions.

    hep-phEPJC(2020)·9 citations
11. 11*

    Gravitational waves from neutrino mass and dark matter genesis

    Pasquale Di Bari🇬🇧 · Danny Marfatia🇺🇸 · Ye-Ling Zhou🇬🇧

    We introduce a model in which the genesis of dark matter (DM) and neutrino masses is associated with a first order phase transition of a scalar singlet field. During the phase transition a source right-handed neutrino (RHN) acquires a spacetime-dependent mass dynamically, a small fraction of which is converted via resonant oscillations into a very weakly mixed dark RHN which decays to a dark matter RHN with the observed relic abundance. Neutrino masses are generated via a traditional two RHN type-I seesaw between a fourth RHN and the source neutrino. The gravitational waves produced during the phase transition have a peak frequency that increases with the DM mass, and are detectable at future gravitational wave interferometers for DM masses above ~ 1 MeV. Since the source RHNs are heavier than the electroweak scale, successful leptogenesis is also attainable.

    hep-phastro-ph.COhep-exhep-thPRD(2020)·26 citations
12. 12*

    The Drell-Yan cross section to third order in the strong coupling constant

    Claude Duhr🇨🇭 · Falko Dulat🇺🇸 · Bernhard Mistlberger🇺🇸

    We present phenomenological results for the inclusive cross section for the production of a lepton-pair via virtual photon exchange at next-to-next-to-next-to-leading order (N${}^3$LO) in perturbative QCD. In line with the case of Higgs production, we find that the hadronic cross section receives corrections at the percent level, and the residual dependence on the perturbative scales is reduced. However, unlike in the Higgs case, we observe that the uncertainty band derived from scale variation is no longer contained in the band of the previous order.

    hep-phhep-exPRL(2020)·208 citations
13. 13*

    Parton Distributions in Nucleons and Nuclei

    Jacob J. Ethier🇳🇱 · Emanuele R. Nocera🇳🇱

    We review the current status of Parton Distribution Function (PDF) determinations for unpolarized and longitudinally polarized protons and for unpolarized nuclei, which are probed by high-energy hadronic scattering in perturbative Quantum Chromodynamics (QCD). We present the established theoretical framework, the experimental information, and the methodological aspects inherent to any modern PDF extraction. Furthermore, we summarize the present knowledge of PDFs and discuss their limitations in both accuracy and precision relevant to advance our understanding of QCD proton substructure and pursue our quest for precision in the Standard Model and beyond. In this respect, we highlight various achievements, discuss contemporary issues in PDF analyses, and outline future directions of progress.

    hep-phhep-exAnn.Rev.Nucl.Part.Sci.(2020)·221 citations
14. 14*

    One-loop matching in the SMEFT extended with a sterile neutrino

    Mikael Chala🇪🇸 · Arsenii Titov🇮🇹

    We study the phenomenology of the simplest renormalisable model that, at low energy, leads to the effective field theory of the Standard Model extended with right-handed neutrinos ($\nu$SMEFT). Our aim is twofold. First, to contextualise new collider signatures in models with sterile neutrinos so far studied only using the bottom-up approach. And second and more important, to provide a thorough example of one-loop matching in the diagrammatic approach, of which other matching techniques and automatic tools can benefit for cross-checks. As byproducts of this work, we provide for the first time: (i) a complete off-shell basis for the $\nu$SMEFT and explicit relations between operators linked by equations of motion; (ii) a complete basis for the low-energy effective field theory ($\nu$LEFT) and the tree-level matching onto the $\nu$SMEFT; (iii) partial one-loop anomalous dimensions in the $\nu$LEFT. This way, our work comprises a new step forward towards the systematisation of one-loop computations in effective field theories, especially if the SM neutrinos are Dirac.

    hep-phJHEP(2020)·69 citations
15. 15*

    Non-relativistic neutrinos and the weak equivalence principle apparent violation

    Massimo Blasone🇮🇹 · Petr Jizba🇨🇿 · Gaetano Lambiase🇮🇹 · Luciano Petruzziello🇮🇹

    We study the non-relativistic limit of Dirac equation for mixed neutrinos. We demonstrate that such a procedure inevitably leads to a redefinition of the inertial mass. This happens because, in contrast to the case when mixing is absent, the antiparticle sector contribution cannot be neglected for neutrinos with definite flavor. We then show that, when a gravitational interaction is switched on, in the weak-field approximation the mass parameter which couples to gravity (gravitational mass) does not undergo the same reformulation as the inertial mass, thus leading to an apparent breakdown of the weak equivalence principle.

    hep-phhep-thPLB(2020)·18 citations
16. 16*

    Vacuum energy of the supersymmetric $\mathbb{C}{P}^{N-1}$ model on $\mathbb{R}\times S^1$ in the $1/N$ expansion

    Kosuke Ishikawa🇯🇵 · Okuto Morikawa🇯🇵 · Kazuya Shibata🇯🇵 · Hiroshi Suzuki🇯🇵

    By employing the $1/N$ expansion, we compute the vacuum energy~$E(\delta ϵ)$ of the two-dimensional supersymmetric (SUSY) $\mathbb{C}{P}^{N-1}$ model on~$\mathbb{R}\times S^1$ with ${\mathbb{Z}}_N$ twisted boundary conditions to the second order in a SUSY-breaking parameter~$\delta ϵ$. This quantity was vigorously studied recently by Fujimori et\ al.\ using a semi-classical approximation based on the bion, motivated by a possible semi-classical picture on the infrared renormalon. In our calculation, we find that the parameter~$\delta ϵ$ receives renormalization and, after this renormalization, the vacuum energy becomes ultraviolet finite. To the next-to-leading order of the $1/N$ expansion, we find that the vacuum energy normalized by the radius of the~$S^1$, $R$, $RE(\delta ϵ)$ behaves as inverse powers of~$\Lambda R$ for~$\Lambda R$ small, where $\Lambda$ is the dynamical scale. Since $\Lambda$ is related to the renormalized 't~Hooft coupling~${\lambda }_R$ as~$\Lambda \sim e^{-2\pi /{\lambda }_R}$, to the order of the $1/N$ expansion we work out, the vacuum energy is a purely non-perturbative quantity and has no well-defined weak coupling expansion in~${\lambda }_R$.

    ↳ hep-thhep-lathep-phPTEP(2020)·8 citations
17. 17*

    Dark bubbles: decorating the wall

    Souvik Banerjee🇩🇪 · Ulf Danielsson🇸🇪 · Suvendu Giri🇸🇪

    Motivated by the difficulty of constructing de Sitter vacua in string theory, a new approach was proposed in arXiv:1807.01570 and arXiv:1907.04268, where four dimensional de Sitter space was realized as the effective cosmology, with matter and radiation, on an expanding spherical bubble that mediates the decay of non supersymmetric $Ad{S}_5$ to a more stable $Ad{S}_5$ in string theory. In this third installment, we further expand on this scenario by considering the backreaction of matter in the bulk and on the brane in terms of how the brane bends. We compute the back reacted metric on the bent brane as well as in the five dimensional bulk. To further illuminate the effect of brane-bending, we compare our results with an explicit computation of the five dimensional graviton propagator using a holographic prescription. Finally we comment on a possible localization of four dimensional gravity in our model using two colliding branes.

    ↳ hep-thgr-qchep-phJHEP(2020)·37 citations
18. 18*

    Axion Star Nucleation in Dark Minihalos around Primordial Black Holes

    Mark P. Hertzberg🇺🇸 · Enrico D. Schiappacasse🇫🇮 · Tsutomu T. Yanagida🇨🇳

    We consider a general class of axion models, including the QCD and string axion, in which the PQ symmetry is broken before or during inflation. Assuming the axion is the dominant component of the dark matter, we discuss axion star formation in virialized dark minihalos around primordial black holes through gravitational Bose-Einstein condensation. We determine the conditions for minihalos to kinetically produce axion stars before galaxy formation. Today, we expect up to $\sim 10^{17}$ ($\sim 10^9$) axion stars in a radius of 100 parsecs around the Sun for the case of the QCD (string) axion.

    ↳ astro-ph.COgr-qchep-phPRD(2020)·47 citations
19. 19*

    Exact solutions of domain wall junctions in arbitrary dimensions

    Minoru Eto🇯🇵 · Masaki Kawaguchi🇯🇵 · Muneto Nitta🇯🇵 · Ryotaro Sasaki🇯🇵

    Exact analytic solutions of static, stable, non-planar BPS domain wall junctions are obtained in extended Abelian-Higgs models in $(D+1)$-dimensional spacetime. For specific choice of mass parameters, the Lagrangian is invariant under the symmetric group ${\mathcal{S}}_{D+1}$ of degree $D+1$ spontaneously broken down to ${\mathcal{S}}_D$ in vacua, admitting ${\mathcal{S}}_{D+1}/{\mathcal{S}}_D$ domain wall junctions. In $D=2$, there are three vacua and three domain walls meeting at a junction point, in which the conventional topological charges $Y$ and $Z$ exist for the BPS domain wall junctions and the BPS domain walls, respectively as known before. In $D=3$, there are four vacua, six domain walls, four junction lines on which three domain walls meet, and one junction point on which all the six domain walls meet. We define a new topological charge $X$ for the junction point in addition to the conventional topological charges $Y$ and $Z$. In general dimensions, we find that the configuration expressed in the $D$-dimensional real space is dual to a regular $D$-simplex in the $D$-dimensional internal space and that a $d$-dimensional subsimplex of the regular $D$-simplex corresponds to a $(D-d)$-dimensional intersection. Topological charges are generalized to the level-$d$ wall charge $W_d$ for the $d$-dimensional subsimplexes.

    ↳ hep-thastro-ph.COhep-phPRD(2020)·7 citations
20. 20*

    Tensor supercurrent in QCD

    Alexander S. Gorsky🇷🇺 · Dmitri E. Kharzeev🇺🇸

    An external Abelian magnetic field excites in the QCD vacuum a tensor supercurrent that represents the tensor polarization of the chiral condensate. This tensor supercurrent can be deduced from the chiral lagrangian in the presence of anomalies; a similar tensor supercurrent emerges in rotating systems at finite chemical potential. We discuss the microscopic origin of this supercurrent and argue that it screens the instanton--anti-instanton $I\bar{I}$ molecules in the QCD vacuum, similarly to the vector supercurrent screening Abrikosov vortices in a superconductor. A number of possible experimental manifestations of the tensor supercurrent are discussed: {\it i}) spin alignment of axial-vector and vector mesons in heavy ion collisions; {\it ii}) tensor charge of the nucleon; {\it iii}) transversity of quark distributions in polarized nucleons.

    ↳ hep-thhep-phnucl-thPRD(2020)·1 citation

* 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.