Mon·Sep 14, 2015Monday·September 14, 2015

1. 01*

   A left-right symmetric flavor symmetry model

   Werner Rodejohann🇩🇪 · Xun-Jie Xu🇩🇪

   We discuss flavor symmetries in left-right symmetric theories. We show that such frameworks are a different environment for flavor symmetry model building compared to the usually considered cases. This does not only concern the need to obey the enlarged gauge structure, but also more subtle issues with respect to residual symmetries. Furthermore, if the discrete left-right symmetry is charge conjugation, potential inconsistencies between the flavor and charge conjugation symmetries should be taken care of. In our predictive model based on $A_4$ we analyze the correlations between the smallest neutrino mass, the atmospheric mixing angle and the Dirac CP phase, the latter prefers to lie around maximal values. There is no lepton flavor violation from the Higgs bi-doublet.

   hep-phEPJC(2016)·24 citations
2. 02*

   Proof of a new colour decomposition for QCD amplitudes

   Tom Melia (UC Berkeley & LBL Berkeley)🇺🇸

   Recently, Johansson and Ochirov conjectured the form of a new colour decomposition for QCD tree-level amplitudes. This note provides a proof of that conjecture. The proof is based on "Mario World" Feynman diagrams, which exhibit the hierarchical Dyck structure previously found to be very useful when dealing with multi-quark amplitudes.

   hep-phJHEP(2015)·40 citations
3. 03*

   Integration by parts identities in integer numbers of dimensions. A criterion for decoupling systems of differential equations

   Lorenzo Tancredi🇩🇪

   Integration by parts identities (IBPs) can be used to express large numbers of apparently different d-dimensional Feynman Integrals in terms of a small subset of so-called master integrals (MIs). Using the IBPs one can moreover show that the MIs fulfil linear systems of coupled differential equations in the external invariants. With the increase in number of loops and external legs, one is left in general with an increasing number of MIs and consequently also with an increasing number of coupled differential equations, which can turn out to be very difficult to solve. In this paper we show how studying the IBPs in fixed integer numbers of dimension d=n with $n\in \mathbb{N}$ one can extract the information useful to determine a new basis of MIs, whose differential equations decouple as $d\to n$ and can therefore be more easily solved as Laurent expansion in (d-n).

   hep-phNPB(2015)·38 citations
4. 04*

   The magnetized effective QCD phase diagram

   Alejandro Ayala🇲🇽 · C. A. Dominguez🇿🇦 · L. A. Hernandez🇿🇦 · M. Loewe🇿🇦 · R. Zamora🇨🇱

   The QCD phase diagram in the temperature versus quark chemical potential plane is studied in the presence of a magnetic field, using the linear sigma model coupled to quarks. It is shown that the decrease of the couplings with increasing field strength obtained in this model leads to the critical temperature for the phase transition to decrease with increasing field intensity (inverse magnetic catalysis). This happens provided that plasma screening is properly accounted for. It is also found that with increasing field strength the location of the critical end point (CEP) in the phase diagram moves toward lower values of the critical quark chemical potential and larger values of the critical temperature. In addition, the CEP approaches the temperature axis for large values of the magnetic field. We argue that a similar behavior is to be expected in QCD, since the physical impact of the magnetic field, regardless of strength, is to produce a spatial dimension reduction, whereby virtual quark-antiquark pairs are closer on average and thus, the strength of their interaction decreases due to asymptotic freedom.

   hep-phhep-latnucl-thPRD(2015)·87 citations
5. 05*

   ${\chi }_{c0}(1P)$ decay into $\bar{\Sigma }\Sigma \pi$ in search of an $I=1$, $1/2^{-}$ baryon state around $\bar{K}N$ threshold

   En Wang🇨🇳 · Ju-Jun Xie🇨🇳 · Eulogio Oset🇪🇸

   We present the theoretical study of the process ${\chi }_{c0}(1P)\to \bar{\Sigma }\Sigma \pi$ decay, by taking into account the $\pi \Sigma$ and $\pi \bar{\Sigma }$ final state interactions of the final meson-baryon pair based on the chiral unitary approach. We show that the process filters the isospin $I=1$ in the $\pi \Sigma$ channel and offers a reaction to test the existence of an $I=1$ state with strangeness $S=-1$ and spin-parity $J^p=1/2^{-}$ around the $\bar{K}N$ threshold predicted by some theories and supported by some experiments.

   hep-phPLB(2016)·24 citations
6. 06*

   Studies of two-solar-mass hybrid stars within the framework of Dyson-Schwinger equations

   Tong Zhao🇨🇳 · Shu-Sheng Xu🇨🇳 · Yan Yan🇨🇳 · Xin-Lian Luo🇨🇳 · Xiao-Jun Liu🇨🇳 · Hong-Shi Zong🇨🇳

   In this paper we introduce an equation of state (EOS) of quark matter within the framework of Dyson-Schwinger equations (DSEs) to study the structure of compact stars. The smooth crossover from hadronic matter to quark matter in the hybrid star is studied. We compare different strategies to obtain crossover EOSs and find a new way to construct two-solar-mass hybrid stars with even a relatively soft quark EOS, while earlier works show that the quark EOS should be stiff enough to support a massive hybrid star.

   hep-phnucl-thPRD(2015)·33 citations
7. 07*

   Quasi-localized wavefunctions on magnetized tori and tiny neutrino Yukawa couplings

   Keigo Sumita🇯🇵

   This paper shows that, a quasi-localization of wavefunctions in toroidal compactifications with magnetic fluxes can lead to a strong suppression for relevant Yukawa couplings, and it is applicable to obtain tiny neutrino masses. Although it is known that magnetic fluxes lead to a Gaussian profile of zero-modes on a torus and that can yield a suppressed coupling in higher-dimensional supersymmetric Yang-Mills (SYM) theories, the largest (diagonal) entry of Yukawa matrices is always of $\mathcal{O}(1)$. In this paper, we propose a way to induce an absolutely tiny global factor of Yukawa matrices. In two SYM theories defined in different dimensional spacetime, their bifundamental representations must be localized as a point in some directions. Overlaps of such point-like localized wavefunctions and Gaussian zero-modes give a global factor of Yukawa matrices, and it can be a strong suppression factor or a usual $\mathcal{O}(1)$ factor, corresponding to their distance. Our numerical analysis shows that it is possible to obtain a suppression strong enough to realize the tiny neutrino masses without a hard fine-tuning. Furthermore, we propose a concrete model of the tiny neutrino Yukawa couplings in a magnetized SYM system.

   hep-phhep-thJHEP(2016)·1 citation
8. 08*

   Constraints on gauge-Higgs unification models at the LHC

   Noriaki Kitazawa🇯🇵 · Yuki Sakai🇯🇵

   We examine the possibility of observing the Kaluza-Klein gluons in gauge-Higgs unification models at the LHC with the energy sqrt{s}=14 TeV. We consider a benchmark model with the gauge symmetry SU(3)_C x SU(3)_W in five-dimensional space-time, where SU(3)_C is the gauge symmetry of the strong interaction and SU(3)_W is that for the electroweak interaction and a Higgs doublet field. It is natural in general to introduce SU(3)_C gauge symmetry in five-dimensional space-time as well as SU(3)_W gauge symmetry in gauge-Higgs unification models. Since the fifth dimension is compactified to S1/Z2 orbifold, there are Kaluza-Klein modes of gluons in low-energy effective theory in four-dimensional space-time. We investigate the resonance contribution of the first Kaluza-Klein gluon to dijet invariant mass distribution at the LHC, and provide signal-to-noise ratios in various cases of Kaluza-Klein gluon masses and kinematical cuts. Although the results are given in a specific benchmark model, we discuss their application to general gauge-Higgs unification models with Kaluza-Klein gluons. Gauge-Higgs unification models can be verified or constrained through the physics of the strong interaction, though they are proposed to solve the naturalness problem in electroweak symmetry breaking.

   hep-phMod.Phys.Lett.A(2016)·7 citations
9. 09*

   Neutrino Physics with Accelerator Driven Subcritical Reactors

   Emilio Ciuffoli🇨🇳 · Jarah Evslin🇨🇳 · Fengyi Zhao🇨🇳

   Accelerator driven system (ADS) subcritical nuclear reactors are under development around the world. They will be intense sources of free, 30-50 MeV antimuon decay at rest antimuon neutrinos. These ADS reactor neutrinos can provide a robust test of the LSND anomaly and a precise measurement of the leptonic CP-violating phase delta, including sign(cos(delta)). The first phase of many ADS programs includes the construction of a low energy, high intensity proton or deuteron accelerator, which can yield competitive bounds on sterile neutrinos.

   hep-phphysics.acc-phphysics.ins-detJHEP(2016)·18 citations
10. 10*

    Tracing the origin of azimuthal gluon correlations in the color glass condensate

    T. Lappi🇫🇮 · B. Schenke🇺🇸 · S. Schlichting🇺🇸 · R. Venugopalan🇺🇸

    We examine the origins of azimuthal correlations observed in high energy proton-nucleus collisions by considering the simple example of the scattering of uncorrelated partons off color fields in a large nucleus. We demonstrate how the physics of fluctuating color fields in the color glass condensate (CGC) effective theory generates these azimuthal multiparticle correlations and compute the corresponding Fourier coefficients v_n within different CGC approximation schemes. We discuss in detail the qualitative and quantitative differences between the different schemes. We will show how a recently introduced color field domain model that captures key features of the observed azimuthal correlations can be understood in the CGC effective theory as a model of non-Gaussian correlations in the target nucleus.

    hep-phnucl-thJHEP(2016)·119 citations
11. 11*

    Exploring Flavor-Dependent Long-Range Forces in Long-Baseline Neutrino Oscillation Experiments

    Sabya Sachi Chatterjee🇮🇳 · Arnab Dasgupta🇮🇳 · Sanjib Kumar Agarwalla🇮🇳

    The Standard Model gauge group can be extended with minimal matter content by introducing anomaly free U(1) symmetry, such as $L_e-L_{\mu }$ or $L_e-L_{\tau }$. If the neutral gauge boson corresponding to this abelian symmetry is ultra-light, then it will give rise to flavor-dependent long-range leptonic force, which can have significant impact on neutrino oscillations. For an instance, the electrons inside the Sun can generate a flavor-dependent long-range potential at the Earth surface, which can suppress the ${\nu }_{\mu }\to {\nu }_e$ appearance probability in terrestrial experiments. The sign of this potential is opposite for anti-neutrinos, and affects the oscillations of (anti-)neutrinos in different fashion. This feature invokes fake CP-asymmetry like the SM matter effect and can severely affect the leptonic CP-violation searches in long-baseline experiments. In this paper, we study in detail the possible impacts of these long-range flavor-diagonal neutral current interactions due to $L_e-L_{\mu }$ symmetry, when (anti-)neutrinos travel from Fermilab to Homestake (1300 km) and CERN to Pyhäsalmi (2290 km) in the context of future high-precision superbeam facilities, DUNE and LBNO respectively. If there is no signal of long-range force, DUNE (LBNO) can place stringent constraint on the effective gauge coupling ${\alpha }_{e\mu }<1.9\times 10^{-53}(7.8\times 10^{-54})$ at 90% C.L., which is almost 30 (70) times better than the existing bound from the Super-Kamiokande experiment. We also observe that if ${\alpha }_{e\mu }\ge 2\times 10^{-52}$, the CP-violation discovery reach of these future facilities vanishes completely. The mass hierarchy measurement remains robust in DUNE (LBNO) if ${\alpha }_{e\mu }<5\times 10^{-52}(10^{-52})$.

    hep-phhep-exphysics.ins-detJHEP(2015)·24 citations
12. 12*

    Production of strange and charmed baryons in pion induced reactions

    Sang-Ho Kim🇯🇵 · Atsushi Hosaka🇯🇵 · Hyun-Chul Kim🇰🇷 · Hiroyuki Noumi🇯🇵

    We study the strangeness and charm productions induced by the pion beam, i.e. the ${\pi }^{-}$p $\to$ $K^{\ast 0}\Lambda$ and ${\pi }^{-}$p $\to$ $D^{\ast -}{\Lambda }_c^{+}$ reactions, based on two different theoretical frameworks: an effective Lagrangian method and a Regge approach. In order to estimate the magnitude of the charm production relative to that of the strangeness production, we assume that the coupling constants for the charmed meson and baryon vertices are the same as those for the strangeness channel. We found that the total cross section for the charm production was about $10^3-10^6$ times smaller than that for the strangeness production, depending on theoretical approaches and kinematical regions. We also discuss each contribution to observables for both reactions. In general, the Regge approach explains the experimental data very well over the whole energy region.

    hep-phhep-exnucl-exnucl-thPRD(2015)·33 citations
13. 13*

    Mirror Cosmological Relaxation of the Electroweak Scale

    Oleksii Matsedonskyi🇮🇹

    The cosmological relaxation mechanism proposed in [1] allows for a dynamically generated large separation between the weak scale and a theory cutoff, using a sharp change of theory behaviour upon crossing the limit between unbroken and broken symmetry phases. In this note we present a variation of this scenario, in which stabilization of the electroweak scale in the right place is ensured by the $Z_2$ symmetry exchanging the Standard Model (SM) with its mirror copy. We sketch the possible ways to produce viable thermal evolution of the Universe and discuss experimental accessibility of the new physics effects. We show that in this scenario the mirror SM can either have sizeable couplings with the ordinary one, or, conversely, can interact with it with a negligible strength. The overall cutoff allowed by such a construction can reach $10^9$ GeV.

    hep-phJHEP(2016)·32 citations
14. 14*

    Background history and cosmic perturbations for a general system of self-conserved dynamical dark energy and matter

    Adria Gomez-Valent🇪🇸 · Elahe Karimkhani🇪🇸 · Joan Sola🇪🇸

    We determine the Hubble expansion and the general cosmic perturbations equations for a general system consisting of self-conserved matter and self-conserved dark energy (DE). While at the background level the two components are non-interacting, they do interact at the perturbations level. We show that the coupled system of matter and DE perturbations can be transformed into a single, third order, matter perturbation equation, which reduces to the (derivative of the) standard one in the case that the DE is just a cosmological constant. As a nontrivial application we analyze a class of dynamical models whose DE density ${\rho }_D$ consists of a constant term, $C_0$, and a series of powers of the Hubble rate. These models were previously analyzed from the point of view of dynamical vacuum models, but here we treat them as self-conserved DE models with a dynamical equation of state. We fit them to the wealth of expansion history and linear structure formation data and compare the obtained fit quality with that of the concordance $\Lambda$CDM model. Those with $C_0=0$ include the so-called "entropic-force" and "QCD-ghost" DE models, as well as the pure linear model ${\rho }_D\sim H$, all of which appear strongly disfavored. The models with $C_0\ne 0$, in contrast, emerge as promising dynamical DE candidates whose phenomenological performance is highly competitive with the rigid $\Lambda$-term inherent to the $\Lambda$CDM.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2015)·67 citations
15. 15*

    On-Shell Recursion Relations for Effective Field Theories

    Clifford Cheung🇺🇸 · Karol Kampf🇨🇿 · Jiri Novotny🇨🇿 · Chia-Hsien Shen🇺🇸 · Jaroslav Trnka🇺🇸

    We derive the first ever on-shell recursion relations for amplitudes in effective field theories. Based solely on factorization and the soft behavior of amplitudes, these recursion relations employ a new rescaling momentum shift to construct all tree-level scattering amplitudes in theories like the non- linear sigma model, Dirac-Born-Infeld theory, and the Galileon. Our results prove that all theories with enhanced soft behavior are on-shell constructible.

    ↳ hep-thhep-phPRL(2016)·216 citations
16. 16*

    Contact-interaction Faddeev equation and, inter alia, proton tensor charges

    Shu-Sheng Xu🇨🇳 · Chen Chen🇨🇳 · Ian C.Cloet🇺🇸 · Craig D. Roberts🇺🇸 · Jorge Segovia🇪🇸 · Hong-Shi Zong🇨🇳

    A confining, symmetry-preserving, Dyson-Schwinger equation treatment of a vector-vector contact interaction is used to formulate Faddeev equations for the nucleon and Delta-baryon in which the kernel involves dynamical dressed-quark exchange and whose solutions therefore provide momentum-dependent Faddeev amplitudes. These solutions are compared with those obtained in the static approximation and with a QCD-kindred formulation of the Faddeev kernel. They are also used to compute a range of nucleon properties, amongst them: the proton's sigma-term; the large Bjorken-x values of separate ratios of unpolarised and longitudinally-polarised valence u- and d-quark parton distribution functions; and the proton's tensor charges, which enable one to directly determine the effect of dressed-quark electric dipole moments (EDMs) on neutron and proton EDMs.

    ↳ nucl-thhep-lathep-phnucl-exPRD(2015)·60 citations
17. 17*

    The Top Quark

    E. Boos🇷🇺 · O. Brandt🇩🇪 · D. Denisov🇺🇸 · S. Denisov🇷🇺 · P. Grannis🇺🇸

    On the twentieth anniversary of the observation of the top quark, we trace our understanding of this heaviest of all known particles from the prediction of its existence, through the searches and discovery, to the current knowledge of its production mechanisms and properties. We also discuss the central role of the top quark in the Standard Model and the windows that it opens for seeking new physics beyond the Standard Model.

    ↳ hep-exhep-phPhys.Usp.(2015)·29 citations
18. 18*

    Minding the MeV Gap: the Indirect Detection of Low Mass Dark Matter

    Kimberly K. Boddy🇺🇸 · Jason Kumar🇺🇸

    We consider the prospects for the indirect detection of low mass dark matter which couples dominantly to quarks. If the center of mass energy is below about 280 MeV, the kinematically allowed final states will be dominated by photons and neutral pions, producing striking signatures at gamma ray telescopes. In fact, an array of new instruments have been proposed, which would greatly improve sensitivity to photons in this energy range. We find that planned instruments can improve on current sensitivity to dark matter models of this type by up to a few orders of magnitude.

    ↳ astro-ph.COastro-ph.HEhep-phAIP Conf.Proc.(2016)·13 citations
19. 19*

    Worldline Numerics for Energy-Momentum Tensors in Casimir Geometries

    Marco Schafer🇩🇪 · Idrish Huet🇩🇪 · Holger Gies🇩🇪

    We develop the worldline formalism for computations of composite operators such as the fluctuation induced energy-momentum tensor. As an example, we use a fluctuating real scalar field subject to Dirichlet boundary conditions. The resulting worldline representation can be evaluated by worldline Monte-Carlo methods in continuous spacetime. We benchmark this worldline numerical algorithm with the aid of analytically accessible single-plate and parallel-plate Casimir configurations, providing a detailed analysis of statistical and systematic errors. The method generalizes straightforwardly to arbitrary Casimir geometries and general background potentials.

    ↳ hep-thhep-phquant-phJ.Phys.A(2016)·11 citations
20. 20*

    Evidence for the Galactic contribution to the IceCube astrophysical neutrino flux

    A. Neronov🇨🇭 · D. V. Semikoz🇫🇷

    We show that the Galactic latitude distribution of IceCube astrophysical neutrino events with energies above 100~TeV is inconsistent with the isotropic model of the astrophysical neutrino flux. Namely, the Galactic latitude distribution of the events shows an excess at low latitudes |b|<10 degrees and a deficit at high Galactic latitude |b|> 50 degrees. We use Monte-Carlo simulations to show that the inconsistency of the isotropic signal model with the data is at > 3 sigma level, after the account of trial factors related to the choice of the low-energy threshold and Galactic latitude binning in our analysis.

    ↳ astro-ph.HEastro-ph.GAhep-phAstropart.Phys.(2016)·86 citations
21. 21*

    Longitudinal double spin asymmetries in single hadron quasi-real photoproduction at high $p_T$

    COMPASS Collaboration: C. Adolph🇩🇪 · R. Akhunzyanov🇷🇺 · M.G. Alexeev🇮🇹 · G.D. Alexeev🇷🇺 · A. Amoroso🇮🇹 · V. Andrieux🇫🇷 · V. Anosov🇷🇺 · W. Augustyniak🇵🇱 · A. Austregesilo🇩🇪 · C.D.R. Azevedo🇵🇹 · B. Badełek🇵🇱 · F. Balestra🇮🇹 and 198 other authors

    We measured the longitudinal double spin asymmetries $A_{LL}$ for single hadron muo-production off protons and deuterons at photon virtuality $Q^2$ < 1(GeV/$c$)${}^2$ for transverse hadron momenta $p_T$ in the range 0.7 GeV/$c$ to 4 GeV/$c$ . They were determined using COMPASS data taken with a polarised muon beam of 160 GeV/$c$ or 200 GeV/$c$ impinging on polarised ${}^6\mathrm{LiD}$ or $\mathrm{N}{\mathrm{H}}_3$ targets. The experimental asymmetries are compared to next-to-leading order pQCD calculations, and are sensitive to the gluon polarisation $\Delta G$ inside the nucleon in the range of the nucleon momentum fraction carried by gluons $0.05<x_g<0.2$.

    ↳ hep-exhep-phPLB(2016)·14 citations
22. 22*

    Non-Perturbative Gauge-Higgs Unification in Five Dimensions

    Graham Moir🇩🇪 · Maurizio Alberti🇩🇪 · Francesco Knechtli🇩🇪 · Nikos Irges🇬🇷

    We study the phase diagram and mass spectrum of an $SU(2)$ Gauge-Higgs Unification scenario on a five-dimensional orbifold.We observe spontaneous symmetry breaking within the Higgs phase of the theory and, in the vicinity of a newly discovered phase, we find that the ratio of Higgs to gauge boson masses takes a Standard Model-like value. Precisely in this region of the phase diagram, we observe dimensional reduction via localisation.

    ↳ hep-lathep-phPoS(2016)·0 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.