Fri·Apr 13, 2018Friday·April 13, 2018

1. 01*

   The interpolating formula for the $0\nu \beta \beta$-decay half-life in the case of light and heavy neutrino mass mechanisms

   A. Babič🇨🇿 · S. Kovalenko🇨🇱 · M.I. Krivoruchenko🇷🇺 · F. Šimkovic🇸🇰

   We revisit the "interpolating formula" proposed in our previous publication. It allows one to calculate the neutrinoless double beta decay ($0\nu \beta \beta$-decay) half-life for arbitrary neutrino mass without involvement of the complicated results for nuclear matrix elements (NME) obtained within specific nuclear structure models. The formula derives from the finding that the value of a properly normalized ratio of the NMEs for the light and heavy neutrino mass mechanisms weakly depends on isotope. From this fact it follows, in particular, that the light and heavy neutrino mass mechanisms can hardly be distinguished in a model independent way searching for $0\nu \beta \beta$-decay of different nuclei. Here we show that this formula holds for all the known nuclear structure approaches. We give a mathematical justification of our results examining analytical properties of the NMEs. We also consider several simplified benchmark scenarios within left-right symmetric models and analyze the conditions for the dominance of the light or heavy neutrino mass mechanisms in $0\nu \beta \beta$-decay.

   hep-phPRD(2018)·19 citations
2. 02*

   The $\lambda$ mechanism of the $0\nu \beta \beta$-decay

   Fedor Šimkovic · Dušan Štefánik · Rastislav Dvornický · Amand Faessler

   The $\lambda$ mechanism ($W_L$-$W_R$ exchange) of the neutrinoless double beta decay ($0\nu \beta \beta$-decay), which has origin in left-right symmetric model with right-handed gauge boson at TeV scale, is investigated. The revisited formalism of the $0\nu \beta \beta$-decay, which includes higher order terms of nucleon current, is exploited. The corresponding nuclear matrix elements are calculated within quasiparticle random phase approximation with partial restoration of the isospin symmetry for nuclei of experimental interest. A possibility to distinguish between the conventional light neutrino mass ($W_L$-$W_L$ exchange) and $\lambda$ mechanisms by observation of the $0\nu \beta \beta$-decay in several nuclei is discussed. A qualitative comparison of effective lepton number violating couplings associated with these two mechanisms is performed. By making viable assumption about the seesaw type mixing of light and heavy neutrinos with the value of Dirac mass $m_D$ within the range $1\text{MeV}<m_D<1\text{GeV}$, it is concluded that there is a dominance of the conventional light neutrino mass mechanism in the decay rate.

   hep-phFron.in Phys.(2017)·11 citations
3. 03*

   Quark gap equation with non-abelian Ball-Chiu vertex

   A. C. Aguilar🇧🇷 · J. C. Cardona🇧🇷 · M. N. Ferreira🇧🇷 · J. Papavassiliou🇪🇸

   The full quark-gluon vertex is a crucial ingredient for the dynamical generation of a constituent quark mass from the standard quark gap equation, and its non-transverse part may be determined exactly from the nonlinear Slavnov-Taylor identity that it satisfies. The resulting expression involves not only the quark propagator, but also the ghost dressing function and the quark-ghost kernel, and constitutes the non-abelian extension of the so-called "Ball-Chiu vertex", known from QED. In the present work we carry out a detailed study of the impact of this vertex on the gap equation and the quark masses generated from it, putting particular emphasis on the contributions directly related with the ghost sector of the theory, and especially the quark-ghost kernel. In particular, we set up and solve the coupled system of six equations that determine the four form factors of the latter kernel and the two typical Dirac structures composing the quark propagator. Due to the incomplete implementation of the multiplicative renormalizability at the level of the gap equation, the correct anomalous dimension of the quark mass is recovered through the inclusion of a certain function, whose ultraviolet behavior is fixed, but its infrared completion is unknown; three particular Ansätze for this function are considered, and their effect on the quark mass and the pion decay constant is explored. The main results of this study indicate that the numerical impact of the quark-ghost kernel is considerable; the transition from a tree-level kernel to the one computed here leads to a $20\%$ increase in the value of the quark mass at the origin. Particularly interesting is the contribution of the fourth Ball-Chiu form factor, which, contrary to the abelian case, is nonvanishing, and accounts for $10\%$ of the total constituent quark mass.

   hep-phhep-latPRD(2018)·73 citations
4. 04*

   Pocket Formulae for Non-Abelian Discrete Anomaly Freedom

   Jim Talbert🇩🇪

   We show that the discrete anomaly constraints governing popular non-Abelian symmetries of use in (e.g.) flavoured, supersymmetric, and dark matter model building typically subdivide into two classes differentiated by the simple restrictions they impose on the number of fields transforming under certain irreducible representations of the relevant groups. These constraints lead us both to generic conclusions for common Beyond-the-Standard-Model constructions (including rather powerful statements for Grand Unified theories) as well as to simplified formulae that can be rapidly applied to determine whether a given field and symmetry content suffers from gauge and gravitational anomalies.

   hep-phhep-thPLB(2018)·9 citations
5. 05*

   Majorana neutrino masses in the scenario of gauge-Higgs unification

   K. Hasegawa🇯🇵 · C. S. Lim🇯🇵

   In this paper we consider possible mechanisms to generate small Majorana neutrino masses for active neutrinos in the scenario of gauge-Higgs unification, a candidate for physics beyond the standard model. We stress that it is non-trivial to find a gauge-invariant operator, responsible for the Majorana masses, which is the counterpart of the well-known SU(2)${}_L\times$ U(1)${}_Y$ invariant higher-mass-dimensional ($d=5$) operator. As the first possibility we discuss the seesaw mechanism by assigning leptonic fields to the adjoint representation of the gauge group, so that a $d=5$ gauge-invariant operator can be formed. It turns out that the mechanism leading to the small Majorana masses is the admixture of the Type I and Type III seesaw mechanisms. As the second possibility, we consider the case where the relevant operator has $d=7$, by introducing a matter scalar belonging to the fundamental representation of the gauge group. Reflecting the fact that the mass dimension of the operator is higher than usually expected, the Majorana masses are generated by a "double seesaw mechanism."

   hep-phPTEP(2018)·10 citations
6. 06*

   Heavy baryons in a pion mean-field approach: A brief review

   Hyun-Chul Kim🇰🇷

   We review in this paper a series of recent works on properties of singly heavy baryons, based on a pion mean-field approach. In the limit of an infinitely heavy-quark mass, the heavy quark inside a heavy baryon can be regarded as a static color source. In this limit, a heavy baryon can be viewed as $N_c-1$ valence quarks bound by the pion mean fields which are created self-consistently by the presence of the $N_c$ valence quarks. We show that this mean-field approach can successfully describe the masses and the magnetic moments of the lowest-lying singly heavy baryons, using all the parameters fixed in the light-baryon sector except for the hyperfine spin-spin interactions. We also review a recent work on identifying the newly found excited ${\Omega }_c$ baryons reported by the LHCb Collaboration. We discuss possible scenarios to identify them. Finally, we give a future perspective on this pion mean-field approach.

   hep-phhep-exhep-latnucl-thJ.Korean Phys.Soc.(2018)·20 citations
7. 07*

   Is bottomonium suppression in proton-nucleus and nucleus-nucleus collisions at LHC energies due to the same effects?

   Elena G. Ferreiro🇪🇸 · Jean-Philippe Lansberg🇫🇷

   We show that we can reproduce all the features of bottomonium suppression in both proton-nucleus and nucleus-nucleus collisions at LHC energies in a comover-interaction picture. For each collisions system, we use the measured {\it relative} suppression of the excited ${\rm Y}$(2S) and ${\rm Y}$(3S) states to ${\rm Y}$(1S) by ATLAS and CMS to parametrise the scattering cross sections of all $S$- and $P$-wave bottomonia with the comoving particles created during the collisions. In addition to a single nonpertubative parameter, these cross sections depend on the momentum distribution of these comovers which we found to be the same for proton-nucleus and nucleus-nucleus collisions as well as for partonic and hadronic comovers. Moreover, we can also reproduce the {\it absolute} suppresion rates measured by ALICE, ATLAS, CMS and LHCb when the nuclear modifications of the parton densities are taken into account.

   hep-phnucl-thJHEP(2018)·89 citations
8. 08*

   Probing an axial-vector tetraquark $Z_s$ via its semileptonic decay $Z_s\to X(4274)\overline{l}{\nu }_l$

   H. Sundu🇹🇷 · B. Barsbay🇹🇷 · S. S. Agaev🇦🇿 · K. Azizi🇹🇷

   The semileptonic decays of the open charm-bottom axial-vector tetraquark $Z_s=[cs][\overline{b}\overline{s}]$ to $X(4274)\overline{l}{\nu }_l$, $l=e,\mu ,\tau$ are explored by means of the QCD three-point sum rule method. Both $Z_s$ and $X(4274)=[cs][\overline{c}\overline{s}]$ are treated as color sextet diquark-antidiquark states. The full width of the decays $Z_s\to X(4274)\overline{l}{\nu }_l$ is found. Obtained predictions for $\Gamma (Z_s\to X(4274)\overline{l}{\nu }_l)$ demonstrate that, as in the case of the conventional hadrons, the semileptonic transitions form a very small part of its full width.

   hep-phhep-exhep-latEPJA(2018)·10 citations
9. 09*

   Running of Fermion Observables in Non-Supersymmetric SO(10) Models

   Tommy Ohlsson🇸🇪 · Marcus Pernow🇸🇪

   We investigate the complete renormalization group running of fermion observables in two different realistic non-supersymmetric models based on the gauge group $\text{SO}(10)$ with intermediate symmetry breaking for both normal and inverted neutrino mass orderings. Contrary to results of previous works, we find that the model with the more minimal Yukawa sector of the Lagrangian fails to reproduce the measured values of observables at the electroweak scale, whereas the model with the more extended Yukawa sector can do so if the neutrino masses have normal ordering. The difficulty in finding acceptable fits to measured data is a result of the added complexity from the effect of an intermediate symmetry breaking as well as tension in the value of the leptonic mixing angle ${\theta }_{23}^{\ell }$.

   hep-phJHEP(2018)·36 citations
10. 10*

    The mass ratios parametrization

    Ulises J. Saldana-Salazar🇩🇪 · Karla M. Tame-Narvaez🇩🇪

    The observed hierarchy in the fermion masses, which imply a set of small mass ratios, is not naturally small regarding 't Hooft's criteria. In this work, in a model independent approach, we introduce a set of conditions by which fermion mass ratios become natural. Interestingly, these conditions demand that fermion mixing should be described by the four independent mass ratios of each fermion sector. Application of this set of conditions to the standard theory enables one to understand the mains aspects in quark and lepton mixing. This feature can be taken as a strong evidence for the existence in Nature of a flavour symmetry. Also, for this analysis to work in the lepton sector, neutrino masses should have normal ordering with the lightest neutrino mass satisfying the lower bound, $m_{\nu 1}⩾(5.0\pm 0.1)\text{ meV}$, making the approach testable.

    hep-phInt.J.Mod.Phys.A(2019)·4 citations
11. 11*

    $R(D^{(\ast )})$ from $W^{\prime }$ and right-handed neutrinos

    Admir Greljo🇩🇪 · Dean J. Robinson🇺🇸 · Bibhushan Shakya🇺🇸 · Jure Zupan🇺🇸

    We provide an ultraviolet (UV) complete model for the $R(D^{(\ast )})$ anomalies, in which the additional contribution to semi-tauonic $b\to c$ transitions arises from decay to a right-handed sterile neutrino via exchange of a TeV-scale $SU(2{)}_L$ singlet $W^{\prime }$. The model is based on an extension of the Standard Model (SM) hypercharge group, $U(1{)}_Y$, to the $SU(2{)}_V\times U(1{)}^{\prime }$ gauge group, containing several pairs of heavy vector-like fermions. We present a comprehensive phenomenological survey of the model, ranging from the low-energy flavor physics, direct searches at the LHC, to neutrino physics and cosmology. We show that, while the $W^{\prime }$ and $Z^{\prime }$-induced constraints are important, it is possible to find parameter space naturally consistent with all the available data. The sterile neutrino sector also offers rich phenomenology, including possibilities for measurable dark radiation, gamma ray signals, and displaced decays at colliders.

    hep-phJHEP(2018)·113 citations
12. 12*

    First Subleading Power Resummation for Event Shapes

    Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Gherardo Vita🇺🇸 · Hua Xing Zhu🇨🇳

    We derive and analytically solve renormalization group (RG) equations of gauge invariant non-local Wilson line operators which resum logarithms for event shape observables $\tau$ at subleading power in the $\tau \ll 1$ expansion. These equations involve a class of universal jet and soft functions arising through operator mixing, which we call $\theta$-jet and $\theta$-soft functions. An illustrative example involving these operators is introduced which captures the generic features of subleading power resummation, allowing us to derive the structure of the RG to all orders in ${\alpha }_s$, and provide field theory definitions of all ingredients. As a simple application, we use this to obtain an analytic leading logarithmic result for the subleading power resummed thrust spectrum for $H\to gg$ in pure glue QCD. This resummation determines the nature of the double logarithmic series at subleading power, which we find is still governed by the cusp anomalous dimension. We check our result by performing an analytic calculation up to $\mathcal{O}({\alpha }_s^3)$. Consistency of the subleading power RG relates subleading power anomalous dimensions, constrains the form of the $\theta$-soft and $\theta$-jet functions, and implies an exponentiation of higher order loop corrections in the subleading power collinear limit. Our results provide a path for carrying out systematic resummation at subleading power for collider observables.

    hep-phhep-thnucl-thJHEP(2018)·121 citations
13. 13*

    Probing Planck Scale Spacetime By Cavity Opto-Atomic ${}^{87}$Rb Interferometry

    M. Khodadi🇮🇷 · K. Nozari🇮🇷 · A. Bhat🇮🇳 · S. Mohsenian🇺🇸

    The project of \emph{"quantum spacetime phenomenology"} focuses on searching pragmatically for the Planck scale quantum features of spacetime. Among these features is the existence of a characteristic length scale addressed commonly by effective approaches to quantum gravity (QG). This characteristic length scale could be realized, for instance and simply, by generalizing the standard Heisenberg uncertainty principle (HUP) to a \emph{"generalized uncertainty principle"} (GUP). While usually it is expected that phenomena belonging to the realm of QG are essentially probable solely at the so-called Planck energy, here we show how a GUP proposal containing the most general modification of coordinate representation of the momentum operator could be probed by a \emph{"cold atomic ensemble recoil experiment"} (CARE) as a low energy quantum system. This proposed atomic interferometer setup has advantages over the conventional architectures owing to the enclosure in a high finesse optical cavity which is supported by a new class of low power consumption integrated devices known as \emph{"micro-electro-opto-mechanical systems"} (MEOMS). The proposed system comprises of a micro mechanical oscillator instead of spherical confocal mirrors as one of the components of high finesse optical cavity. In the framework of a bottom-up QG phenomenological viewpoint and by taking into account the measurement accuracy realized for the fine structure constant (FSC) from the Rubidium (${}^{87}$Rb) CARE, we set some constraints as upper bounds on the characteristic parameters of the underlying GUP. In the case of superposition of the possible GUP modification terms, we managed to set a tight constraint as $0.999978<{\lambda }_0<1.00002$ for the dimensionless characteristic parameter.

    hep-phgr-qchep-thphysics.ins-detPTEP(2019)·15 citations
14. 14*

    MOND and the dynamics of NGC1052-DF2

    B. Famaey🇫🇷 · S. McGaugh🇺🇸 · M. Milgrom🇮🇱

    The dwarf galaxy NGC1052-DF2 has recently been identified as potentially lacking dark matter. If correct, this could be a challenge for MOND, which predicts that low surface brightness galaxies should evince large mass discrepancies. However, the correct prediction of MOND depends on both the internal field of the dwarf and the external field caused by its proximity to the giant elliptical NGC1052. Taking both into consideration under plausible assumptions, we find ${\sigma }_{\mathrm{MOND}}=13.4_{-3.7}^{+4.8}\mathrm{km}{\mathrm{s}}^{-1}$. This is only marginally higher than the claimed 90\% upper limit on the velocity dispersion ($\sigma <10.5\mathrm{km}{\mathrm{s}}^{-1}$), and compares well with the observed root mean square velocity dispersion ($\sigma =14.3\mathrm{km}{\mathrm{s}}^{-1}$). We also discuss a few caveats on both the observational and theoretical side. On the theory side, the internal virialization time in this dwarf may be longer that the time scale of variation of the external field. On the observational side, the paucity of data and their large uncertainties call for further analysis of the velocity dispersion of NGC1052-DF2, to check whether it poses a challenge to MOND or is a success thereof.

    ↳ astro-ph.GAastro-ph.COgr-qchep-phMNRAS(2018)·47 citations
15. 15*

    S-matrix bootstrap for resonances

    N. Doroud🇮🇹 · J. Elias Miró🇮🇹

    We study the $2\to 2$ $S$-matrix element of a generic, gapped and Lorentz invariant QFT in $d=1+1$ space time dimensions. We derive an analytical bound on the coupling of the asymptotic states to unstable particles (a.k.a. resonances) and its physical implications. This is achieved by exploiting the connection between the S-matrix phase-shift and the roots of the S-matrix in the physical sheet. We also develop a numerical framework to recover the analytical bound as a solution to a numerical optimization problem. This later approach can be generalized to $d=3+1$ spacetime dimensions.

    ↳ hep-thhep-phJHEP(2018)·36 citations
16. 16*

    Probing the nature of dark matter particles with stellar streams

    Nilanjan Banik🇳🇱 · Gianfranco Bertone🇳🇱 · Jo Bovy🇨🇦 · Nassim Bozorgnia🇬🇧

    A key prediction of the standard cosmological model -- which relies on the assumption that dark matter is cold, i.e. non-relativistic at the epoch of structure formation -- is the existence of a large number of dark matter substructures on sub-galactic scales. This assumption can be tested by studying the perturbations induced by dark matter substructures on cold stellar streams. Here, we study the prospects for discriminating cold from warm dark matter by generating mock data for upcoming astronomical surveys such as the Large Synoptic Survey Telescope (LSST), and reconstructing the properties of the dark matter particle from the perturbations induced on the stellar density profile of a stream. We discuss the statistical and systematic uncertainties, and show that the method should allow to set stringent constraints on the mass of thermal dark matter relics, and possibly to yield an actual measurement of the dark matter particle mass if it is in the $\mathcal{O}(1)$ keV range.

    ↳ astro-ph.COastro-ph.GAhep-phJCAP(2018)·66 citations
17. 17*

    The spectrum of an SU(3) gauge theory with a fundamental Higgs field

    Axel Maas🇦🇹 · Pascal Törek🇦🇹

    In gauge theories, the physical, experimentally observable spectrum consists only of gauge-invariant states. This spectrum can be different from the elementary spectrum even at weak coupling and in the presence of the Brout-Englert-Higgs effect. We demonstrate this for an SU(3) gauge theory with a single fundamental Higgs, a toy theory for grand-unified theories. The manifestly gauge-invariant approach of lattice gauge theory is used to determine the spectrum in four different channels. It is found to be qualitatively different from the elementary one, and especially from the one predicted by standard perturbation theory. The result can be understood in terms of the Froehlich-Morchio-Strocchi mechanism. In fact, we find that analytic methods based on this mechanism, a gauge-invariant extension of perturbation theory, correctly determines the spectrum, and gives already at leading order a reasonably good quantitative description. Together with previous results this supports that this approach is the analytic method of choice for theories with a Brout-Englert-Higgs effect.

    ↳ hep-lathep-phAnnals Phys.(2018)·29 citations
18. 18*

    Large proton cumulants from the superposition of ordinary multiplicity distributions

    Adam Bzdak🇵🇱 · Volker Koch🇺🇸 · Dmytro Oliinychenko🇺🇸 · Jan Steinheimer🇩🇪

    We construct a multiplicity distribution characterized by large factorial cumulants (integrated correlation functions) from a simple combination of two ordinary multiplicity distributions characterized by small factorial cumulants. We find that such a model, which could be interpreted as representing two event classes, reproduces the preliminary data for the proton cumulants measured by the STAR collaboration at $7.7$ GeV very well. This model then predicts very large values for the fifth and sixth order factorial cumulants, which can be tested in experiment.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·32 citations
19. 19*

    Branching ratios for deexcitation processes of daughter nuclei following invisible dinucleon decays in ${}^{16}$O

    K. Hagino🇯🇵 · M. Nirkko🇬🇧

    Various theories beyond the standard model of particle physics predict the existence of baryon number violating processes resulting in nucleon decay. When occurring within an atomic nucleus, such a decay will be followed by secondary decays of the daughter nucleus unless its ground state is directly populated. In this paper, we estimate branching ratios for processes associated with dinucleon decays of the ${}^{16}$O nucleus. To this end, we use a simple shell model for the ground state of ${}^{16}$O. For decays from the 1$s_{1/2}$ configuration, which result in highly excited states in the daughter nucleus, we employ a statistical model with the Hauser-Feshbach theory. Our analysis indicates that the branching ratio for gamma-ray emission in the energy range between 5 and 9 MeV, which is relevant to low-threshold water Cherenkov experiments such as SNO+, is 4.53%, 35.7%, and 20.2% for the $nn$, $pp$, and $pn$ decays in ${}^{16}$O, respectively. In particular, emission of 6.09 MeV and 7.01 MeV gamma-rays from ${}^{14}$C, and 6.45 MeV and 7.03 MeV gamma-rays from ${}^{14}$N, have branching ratios as large as 10.9%, 20.1%, 7.73% and 8.90%, respectively.

    ↳ nucl-thhep-exhep-phnucl-exJ.Phys.G(2018)·4 citations
20. 20*

    Partonic quasidistributions in two-dimensional QCD

    Yu Jia🇨🇳 · Shuangran Liang🇨🇳 · Xiaonu Xiong🇩🇪 · Rui Yu🇨🇳

    As a sequel of our preceding work [1] we carry out a comprehensive comparative study between the quasi parton distribution functions (PDFs), distribution amplitudes (DAs) and their light-cone counterparts for various flavor-neutral mesons, in the context of the 't Hooft model, that is, the two-dimensional QCD in the large $N$ limit. In contrast to the original derivation via diagrammatic techniques exemplified by Dyson-Schwinger and Bethe-Salpeter equations, here we employ the Hamiltonian operator approach to reconstruct the celebrated 't Hooft equation in light-front quantization, and Bars-Green equations in equal-time quantization. The novelty of our derivation is to employ the soft momentum cutoff as the IR regulator. As a virtue of this operator approach, the functional form of the quasi distributions can be transparently built out of the Bars-Green wave functions and the Bogoliubov angle with the aid of bosonization technique. Equipped with various bound-state wave functions numerically inferred in [1], we then investigate how rapidly the quasi distributions approach their light-cone counterparts with the increasing meson momentum. We observe that, light mesons' quasi distributions approach the light-cone distributions in a slower pace than the heavy quarkonia. Curiously, lattice simulations of quasi distributions in four-dimensional QCD also discover this feature. Furthermore, we also compute the partonic light-cone PDF and quasi-PDF to one-loop order in perturbation theory, again employing the momentum cutoff as the IR regulator. We explicitly verify one of the backbones underlying the large momentum effective field theory (LaMET), namely, both quasi-PDFs and light-cone PDFs in ${\mathrm{QCD}}_2$ indeed possess the same IR behavior at leading order in $1/P^z$

    ↳ hep-thhep-lathep-phnucl-thPRD(2018)·44 citations
21. 21*

    Analytic Two-Loop Higgs Amplitudes in Effective Field Theory and the Maximal Transcendentality Principle

    Qingjun Jin🇨🇳 · Gang Yang🇨🇳

    We obtain for the first time the two-loop amplitudes for Higgs plus three gluons in Higgs effective field theory including dimension-seven operators. This provides the S-matrix elements for the top mass corrections for Higgs plus a jet production at LHC. The computation is based on the on-shell unitarity method combined with integration by parts reduction. We work in conventional dimensional regularization and obtain analytic expressions renormalized in the MS-bar scheme. The two-loop anomalous dimensions present operator mixing behavior. The infrared divergences agree with that predicted by Catani and the finite remainders take remarkably simple forms, where the maximally transcendental parts are identical to the corresponding results in N=4 super-Yang-Mills theory. The parts of lower transcendentality turn out to be also largely determined by the N=4 results.

    ↳ hep-thhep-phPRL(2018)·36 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.