Fri·Mar 2, 2018Friday·March 2, 2018

1. 01*

   Mesons and diquarks in a color superconducting regime

   Eric Blanquier🇫🇷

   The behavior of the mesons and diquarks is studied at finite temperatures, chemical potentials and densities, notably when the color superconductivity is taken into account. The Nambu and Jona-Lasinio model complemented by a Polyakov loop (PNJL description) has been adapted in order to model these composite particles in this regime. This paper focuses on the scalar and pseudo-scalar mesons and diquarks, in a three-flavor and three-color description, with the isospin symmetry and at null strangeness. A finality of this work is to underline the modifications carried out by the color superconducting regime on the used equations and on the obtained results. It has been observed that the two-flavor color-superconducting (2SC) phase affects the masses of the mesons and diquarks in a non-negligible way. This observation is particularly true at high densities and low temperatures for the pions, $\eta$ and the diquarks [ud] whose color is rg. This reveals that the inclusion of the color superconductivity is relevant to describe the mesons and diquarks near the first order chiral phase transition.

   hep-phInt.J.Mod.Phys.A(2022)·1 citation
2. 02*

   Proton decay and light sterile neutrinos

   Juan C. Helo🇨🇱 · Martin Hirsch🇪🇸 · Toshihiko Ota🇺🇸

   Within the standard model, non-renormalizable operators at dimension six ($d=6$) violate baryon and lepton number by one unit and thus lead to proton decay. Here, we point out that the proton decay mode with a charged pion and missing energy can be a characteristic signature of $d=6$ operators containing a light sterile neutrino, if it is not accompanied by the standard ${\pi }^0{e}^{+}$ final state. We discuss this effect first at the level of effective operators and then provide a concrete model with new physics at the TeV scale, in which the lightness of the active neutrinos and the stability of the proton are related.

   hep-phJHEP(2018)·32 citations
3. 03*

   Neutrino-Electron Scattering: General Constraints on Z' and Dark Photon Models

   Manfred Lindner🇩🇪 · Farinaldo S. Queiroz🇧🇷 · Werner Rodejohann🇩🇪 · Xun-Jie Xu🇩🇪

   We study the framework of $U(1{)}_X$ models with kinetic mixing and/or mass mixing terms. We give general and exact analytic formulas and derive limits on a variety of $U(1{)}_X$ models that induce new physics contributions to neutrino-electron scattering, taking into account interference between the new physics and Standard Model contributions. Data from TEXONO, CHARM-II and GEMMA are analyzed and shown to be complementary to each other to provide the most restrictive bounds on masses of the new vector bosons. In particular, we demonstrate the validity of our results to dark photon-like as well as light $Z^{\prime }$ models.

   hep-phastro-ph.HEhep-exJHEP(2018)·124 citations
4. 04*

   Pulling Out All the Tops with Computer Vision and Deep Learning

   Sebastian Macaluso🇺🇸 · David Shih🇺🇸

   We apply computer vision with deep learning -- in the form of a convolutional neural network (CNN) -- to build a highly effective boosted top tagger. Previous work (the "DeepTop" tagger of Kasieczka et al) has shown that a CNN-based top tagger can achieve comparable performance to state-of-the-art conventional top taggers based on high-level inputs. Here, we introduce a number of improvements to the DeepTop tagger, including architecture, training, image preprocessing, sample size and color pixels. Our final CNN top tagger outperforms BDTs based on high-level inputs by a factor of $\sim 2$--3 or more in background rejection, over a wide range of tagging efficiencies and fiducial jet selections. As reference points, we achieve a QCD background rejection factor of 500 (60) at 50\% top tagging efficiency for fully-merged (non-merged) top jets with $p_T$ in the 800--900 GeV (350--450 GeV) range. Our CNN can also be straightforwardly extended to the classification of other types of jets, and the lessons learned here may be useful to others designing their own deep NNs for LHC applications.

   hep-phhep-exJHEP(2018)·175 citations
5. 05*

   Prospects for Detecting light bosons at the FCC-ee and CEPC

   We-Fu Chang🇹🇼 · John N. Ng🇨🇦 · Graham White🇨🇦

   We look at the prospects for detecting light bosons, $X$, at proposed Z factories assuming a production of $10^{12}$ Z bosons. Such a large yield is within the design goals of future FCC-ee and CEPC colliders. Specifically we look at the cases where $X$ is either a singlet scalar which mixes with the standard model Higgs or a vector boson with mass $1\lesssim M_X\lesssim 80$ GeV. We find that several channels are particularly promising for discovery prospects. In particular $Z\to f\bar{f}X$ and $Z\to V_{Q}X$ gives a promising signal above a very clean standard model background. We also discuss several channels that have too large a background to be useful.

   hep-phhep-exPRD(2018)·11 citations
6. 06*

   Charged Higgs boson contribution to $B_q^{-}\to \ell \bar{\nu }$ and $\bar{B}\to (P,V)\ell \bar{\nu }$ in a generic two-Higgs doublet model

   Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇰🇷

   We comprehensively study the charged-Higgs contributions to the leptonic $B_q^{-}\to \ell \bar{\nu }$ ($q=u,c$) and semileptonic $\bar{B}\to X_q\ell \bar{\nu }$ ($X_u=\pi ,\rho ;X_c=D,D^{\ast }$) decays in the type-III two-Higgs-doublet model (2HDM). We employ the Cheng-Sher ansatz to suppress the tree-level flavor-changing neutral currents (FCNCs) in the quark sector. When the strict constraints from the $\Delta B=2$ and $b\to s\gamma$ processes are considered, parameters ${\chi }_{tq}^u$ from the quark couplings and ${\chi }_{\ell }^{\ell }$ from the lepton couplings dictate the leptonic and semileptonic $B$ decays. It is found that when the measured $B_u^{-}\to \tau \bar{\nu }$ and indirect bound of $B_c^{-}\to \tau \bar{\nu }$ obtained by LEP1 data are taken into account, $R(D)$ and $R(\pi )$ can have broadly allowed ranges; however, the values of $R(\rho )$ and $R(D^{\ast })$ are limited to approximately the standard model (SM) results. We also find that the same behaviors also occur in the $\tau$-lepton polarizations and forward-backward asymmetries ($A_{FB}^{X_q,\tau }$) of the semileptonic decays, with the exception of $A_{FB}^{D^{\ast },\tau }$, for which the deviation from the SM due to the charged-Higgs effect is still sizable. In addition, the $q^2$-dependent $A_{FB}^{\pi ,\tau }$ and $A_{FB}^{D,\tau }$ can be very sensitive to the charged-Higgs effects and have completely different shapes from the SM.

   hep-phhep-exPRD(2018)·29 citations
7. 07*

   Magnetic moments of the spin-$\frac{1}{2}$ singly charmed baryons in chiral perturbation theory

   Guang-Juan Wang🇨🇳 · Lu Meng🇨🇳 · Hao-Song Li🇨🇳 · Zhan-Wei Liu🇨🇳 · Shi-Lin Zhu🇨🇳

   We systematically derive the analytical expressions of the magnetic moments of the spin-$\frac{1}{2}$ singly charmed baryons to the next-to-next-to-leading order in the heavy baryon chiral perturbation theory (HBChPT). We discuss the analytical relations between the magnetic moments. We estimate the-low energy constants (LECs) in two scenarios. In the first scenario, we use the quark model and Lattice QCD simulation results as input. In the second scenario, the heavy quark symmetry is adopted to reduce the number of the independent LECs, which are then fitted using the data from the Lattice QCD simulations. We give the numerical results to the next-to-leading order for the antitriplet charmed baryons and to the next-to-next-to-leading order for the sextet states.

   hep-phhep-exhep-latPRD(2018)·39 citations
8. 08*

   Searching for Metastable Particles with Sub-Millimeter Displaced Vertices at Hadron Colliders

   Hayato Ito🇯🇵 · Osamu Jinnouchi🇯🇵 · Takeo Moroi🇯🇵 · Natsumi Nagata🇯🇵 · Hidetoshi Otono🇯🇵

   A variety of new-physics models predict metastable particles whose decay length is $\lesssim 1$ mm. Conventional displaced-vertex searches are less sensitive to this sub-millimeter decay range, and thus such metastable particles have been looked for only in usual prompt decay searches. In this paper, we show that an additional event-selection cut based on the vertex reconstruction using charged tracks considerably improves the sensitivity of ordinary searches which rely only on kinematic selection criteria, for particles with a decay length of $\gtrsim 100$ $\mu \text{m}$. To that end, we consider a metastable gluino as an example, and study the impact of this new event-selection cut on gluino searches at the LHC by simulating both the signal and Standard Model background processes. Uncertainty of the displaced-vertex reconstruction due to the limited resolution of track reconstruction is taken into account. We also discuss possibilities for optimization of the kinematic selection criteria, which takes advantage of significant reduction of background through the requirement of displaced vertices. In addition, we demonstrate that using the method discussed in this paper it is possible to measure the lifetime of metastable particles with an $\mathcal{O}(1)$ accuracy at the high-luminosity LHC. Implications for a future 100 TeV collider are also studied, where produced particles tend to be more boosted and thus it is easier to detect the longevity of metastable particles.

   hep-phhep-exJHEP(2018)·13 citations
9. 09*

   Dimension-seven operator contribution to the top quark anomalous interactions

   V.V. Denisov🇷🇺 · S.R. Slabospitskii🇷🇺

   The contribution of dimension-seven operators to anomalous FCNC-interactions of the t-quarks with a photon and a gluon is considered. The phenomenological Lagrangian and Feynman rules are derived. There are evaluated the expressions for the widths FCNC-decays of the t-quark into light quark and two photons, two gluons, a photon and a gluon, and three quarks.

   hep-ph0 citations
10. 10*

    Induced-Gravity GUT-Scale Higgs Inflation in Supergravity

    Constantinos Pallis🇬🇷 · Qaisar Shafi🇺🇸

    Models of induced-gravity inflation are formulated within Supergravity employing as inflaton the Higgs field which leads to a spontaneous breaking of a U(1)B-L symmetry at Mgut=2x10^16 GeV. We use a renormalizable superpotential, fixed by a U(1) R symmetry, and Kahler potentials which exhibit a quadratic non-minimal coupling to gravity with or without an independent kinetic mixing in the inflaton sector. In both cases we find inflationary solutions of Starobinsky type whereas in the latter case, others (more marginal) which resemble those of linear inflation arise too. In all cases the inflaton mass is predicted to be of the order of 10^13~GeV. Extending the superpotential of the model with suitable terms, we show how the MSSM mu parameter can be generated. Also, non-thermal leptogenesis can be successfully realized, provided that the gravitino is heavier than about 10 TeV.

    hep-phastro-ph.COhep-thEPJC(2018)·20 citations
11. 11*

    Strong and radiative decays of the low-lying $D$-wave singly heavy baryons

    Ya-Xiong Yao🇨🇳 · Kai-Lei Wang🇨🇳 · Xian-Hui Zhong🇨🇳

    The strong and radiative decays of the low-lying $\lambda$-mode $D$-wave ${\Lambda }_{c(b)}$, ${\Sigma }_{c(b)}$, ${\Xi }_{c(b)}$, ${\Xi }_{c(b)}^{\prime }$, and ${\Omega }_{c(b)}$ baryons are studied in a constituent quark model. Our calculation shows the following: (i) The missing $\lambda$-mode $D$-wave ${\Omega }_{c(b)}$, ${\Lambda }_b$, and ${\Xi }_b$ baryons have a relatively narrow decay width of a few MeV or a few tens of MeV and their dominant strong and radiative decay channels can be ideal for searching for their signals in future experiments. (ii) The $\lambda$-mode $1D$-wave excitations in the ${\Sigma }_{c(b)}$ and ${\Xi }_{c(b)}^{\prime }$ families appear to have a relatively broad width of $\sim 50-200$ MeV.Most of the $1D$-wave states have large decay rates into the $1P$-wave heavy baryons via the pionic or kaonic strong decay processes, which should be taken seriously in future observations. (iii) Both ${\Lambda }_c(2860)$ and ${\Xi }_c(3050)$ seem to favor the $J^P=3/2^{+}$ excitation ${|}^2{D}_{\lambda \lambda }{\frac{3}{2}}^{+}⟩$ of ${\bar{3}}_F$, while both ${\Lambda }_c(2880)$ and ${\Xi }_c(3080)$ may be assigned as the $J^P=5/2^{+}$ excitation ${|}^2{D}_{\lambda \lambda }{\frac{5}{2}}^{+}⟩$ of ${\bar{3}}_F$. The nature of ${\Xi }_c(3050)$ and ${\Xi }_c(3080)$ could be tested by the radiative transitions ${\Xi }_c(3055{)}^0\to {\Xi }_c(2790{)}^0\gamma$ and ${\Xi }_c(3080{)}^0\to {\Xi }_c(2815{)}^0\gamma$, respectively.

    hep-phhep-exPRD(2018)·76 citations
12. 12*

    Search for the Electric Dipole Moment and anomalous magnetic moment of the tau lepton at tau factories

    Xin Chen🇨🇳 · Yongcheng Wu🇨🇦

    Precise measurement of the Electric Dipole Moment (EDM) and anomalous magnetic moment ($g$-2) of particles are important tests of Beyond Standard Model (BSM) physics. It is generally believed that the tau lepton couples more strongly to BSM due to its large mass, and can be searched for at collider experiments. A new method to approximately reconstruct the neutrinos from the hadronic decays of ${\tau }^{-}{\tau }^{+}$ pairs produced at $e^{-}{e}^{+}$ tau factories is proposed. With all final state particle momenta available, observables based on matrix elements and sensitive to BSM are calculated. It is estimated that with 50 ab${}^{-1}$ of data to be delivered by the $Belle$-II experiment, a tau EDM search with a 1-$\sigma$ level precision of $|d_{\tau }^{NP}|<2.04\times 10^{-19}$ e$\cdot$cm, and $g$-2 search with $|a_{\tau }^{NP}|<1.75\times 10^{-5}$ ($1.5\%$ of the SM prediction), can be expected when systematics are not considered. The new precision can effectively constrain BSM models with heavy mirror neutrinos. It can also constrain models containing a light scalar with mass at $O$(1 GeV), which can explain the current muon $g$-2 anomaly as well. The method in this work offers a new opportunity to search for BSM at current and future tau factories with high precision.

    hep-phJHEP(2019)·54 citations
13. 13*

    Heavy and heavy-light mesons in the Covariant Spectator Theory

    Alfred Stadler🇵🇹 · Sofia Leitão🇵🇹 · M. T. Peña🇵🇹 · Elmar P. Biernat🇵🇹

    The masses and vertex functions of heavy and heavy-light mesons, described as quark-antiquark bound states, are calculated with the Covariant Spectator Theory (CST). We use a kernel with an adjustable mixture of Lorentz scalar, pseudoscalar, and vector linear confining interaction, together with a one-gluon-exchange kernel. A series of fits to the heavy and heavy-light meson spectrum were calculated, and we discuss what conclusions can be drawn from it, especially about the Lorentz structure of the kernel. We also apply the Brodsky-Huang-Lepage prescription to express the CST wave functions for heavy quarkonia in terms of light-front variables. They agree remarkably well with light-front wave functions obtained in the Hamiltonian basis light-front quantization (BLFQ) approach, even in excited states.

    hep-phFew Body Syst.(2018)·9 citations
14. 14*

    Reconstruction of primordial tensor power spectra from B-mode polarization of the cosmic microwave background

    Takashi Hiramatsu🇯🇵 · Eiichiro Komatsu🇩🇪 · Masashi Hazumi🇯🇵 · Misao Sasaki🇯🇵

    Given observations of B-mode polarization power spectrum of the cosmic microwave background (CMB), we can reconstruct power spectra of primordial tensor modes from the early Universe without assuming their functional form such as a power-law spectrum. Shape of the reconstructed spectra can then be used to probe the origin of tensor modes in a model-independent manner. We use the Fisher matrix to calculate the covariance matrix of tensor power spectra reconstructed in bins. We find that the power spectra are best reconstructed at wavenumbers in the vicinity of $k\approx 6\times 10^{-4}$ and $5\times 10^{-3}{\mathrm{Mpc}}^{-1}$, which correspond to the "reionization bump" at $\ell \lesssim 6$ and "recombination bump" at $\ell \approx 80$ of the CMB B-mode power spectrum, respectively. The error bar between these two wavenumbers is larger because of lack of the signal between the reionization and recombination bumps. The error bars increase sharply towards smaller (larger) wavenumbers because of the cosmic variance (CMB lensing and instrumental noise). To demonstrate utility of the reconstructed power spectra we investigate whether we can distinguish between various sources of tensor modes including those from the vacuum metric fluctuation and SU(2) gauge fields during single-field slow-roll inflation, open inflation and massive gravity inflation. The results depend on the model parameters, but we find that future CMB experiments are sensitive to differences in these models. We make our calculation tool available on-line.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2018)·19 citations
15. 15*

    Nonlinear coupling of flow harmonics: Hexagonal flow and beyond

    Giuliano Giacalone🇫🇷 · Li Yan🇨🇦 · Jean-Yves Ollitrault🇫🇷

    Higher Fourier harmonics of anisotropic flow ($v_4$ and beyond) get large contributions induced by elliptic and triangular flow through nonlinear response. We present a general framework of nonlinear hydrodynamic response which encompasses the existing one, and allows to take into account the mutual correlation between the nonlinear couplings affecting Fourier harmonics of any order. Using Large Hadron Collider data on Pb+Pb collisions at ~$\sqrt[]{s}=2.76$ TeV, we perform an application of our formalism to hexagonal flow, $v_6$, a coefficient affected by several nonlinear contributions which are of the same order of magnitude. We obtain the first experimental measure of the coefficient ${\chi }_{624}$, which couples $v_6$ to $v_2$ and $v_4$. This is achieved by putting together the information from several analyses: event-plane correlations, symmetric cumulants, as well as new higher-order moments recently analyzed by the ALICE collaboration. The value of ${\chi }_{624}$ extracted from data is in fair agreement with hydrodynamic calculations, although with large error bars, which would be dramatically reduced by a dedicated analysis. We argue that within our formalism the nonlinear structure of a given higher harmonic can be determined more accurately than the harmonic itself, and we emphasize potential applications to future measurements of $v_7$ and $v_8$.

    ↳ nucl-thhep-phnucl-exPRC(2018)·14 citations
16. 16*

    Finite Density Two Color Chiral Perturbation Theory Revisited

    Prabal Adhikari🇺🇸 · Soma B. Beleznay🇺🇸 · Massimo Mannarelli🇮🇹

    We revisit two-color, two-flavor chiral perturbation theory at finite isospin and baryon density. We investigate the phase diagram obtained varying the isospin and the baryon chemical potentials, focusing on the phase transition occurring when the two chemical potentials are equal and exceed the pion mass (which is degenerate with the diquark mass). In this case, there is a change in the order parameter of the theory that does not lend itself to the standard picture of first order transitions. We explore this phase transition both within a Ginzburg-Landau framework valid in a limited parameter space and then by inspecting the full chiral Lagrangian in all the accessible parameter space. Across the phase transition between the two broken phases the order parameter becomes an $SU(2)$ doublet, with the ground state fixing the expectation value of the sum of the magnitude squared of the pion and the diquark fields. Furthermore, we find that the Lagrangian at equal chemical potentials is invariant under global $SU(2)$ transformations and construct the effective Lagrangian of the three Goldstone degrees of freedom by integrating out the radial fluctuations.

    ↳ hep-thhep-phEPJC(2018)·16 citations
17. 17*

    A Simple Worldsheet Black Hole

    Sergei Dubovsky🇺🇸

    We study worldsheet theory of confining strings in two-dimensional massive adjoint QCD. Similarly to confining strings in higher dimensions this theory exhibits a non-trivial $S$-matrix surviving even in the strict planar limit. In the process of two-particle scattering a zigzag is formed on the worldsheet. It leads to an interesting non-locality and exhibits some properties of a quantum black hole. Ordinarily, identical quantum particles do not carry identity. On the worldsheet they acquire off-shell identity due to strings attached. Identity implies complementarity. We discuss similarities and differences of the worldsheet scattering with the $T\bar{T}$ deformation. We also propose a promising candidate for a supersymmetric model with integrable confining strings.

    ↳ hep-thgr-qchep-lathep-phJHEP(2018)·30 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.