Thu·Apr 14, 2016Thursday·April 14, 2016

1. 01*

   Classifying CP transformations according to their texture zeros: theory and implications

   Peng Chen🇨🇳 · Gui-Jun Ding🇨🇳 · Felix Gonzalez-Canales🇪🇸 · J. W. F. Valle🇪🇸

   We provide a classification of generalized CP symmetries preserved by the neutrino mass matrix according to the number of zero entries in the associated transformation matrix. We determine the corresponding constrained form of the lepton mixing matrix, characterized by correlations between the mixing angles and the CP violating phases. We compare with the corresponding restrictions from current neutrino oscillation global fits and show that, in some cases, the Dirac CP phase characterizing oscillations is highly constrained. Implications for current and upcoming long baseline neutrino oscillation experiments T2K, NO$\nu$A and DUNE, as well as neutrinoless double beta decay experiments are discussed. We also study the cosmological implications of such schemes for leptogenesis.

   hep-phPRD(2016)·38 citations
2. 02*

   The $\pi \pi \to \pi {\gamma }^{\star }$ amplitude and the resonant $\rho \to \pi {\gamma }^{\star }$ transition from lattice QCD

   Raúl A. Briceño🇺🇸 · Jozef J. Dudek🇺🇸 · Robert G. Edwards🇺🇸 · Christian J. Shultz🇺🇸 · Christopher E. Thomas🇬🇧 · David J. Wilson🇬🇧

   We present a determination of the $P$-wave $\pi \pi \to \pi {\gamma }^{\star }$ transition amplitude from lattice quantum chromodynamics. Matrix elements of the vector current in a finite-volume are extracted from three-point correlation functions, and from these we determine the infinite-volume amplitude using a generalization of the Lellouch-Lüscher formalism. We determine the amplitude for a range of discrete values of the $\pi \pi$ energy and virtuality of the photon, and observe the expected dynamical enhancement due to the $\rho$ resonance. Describing the energy dependence of the amplitude, we are able to analytically continue into the complex energy plane and from the residue at the $\rho$ pole extract the $\rho \to \pi {\gamma }^{\star }$ transition form factor. This calculation, at $m_{\pi }\approx 400$ MeV, is the first to determine the form factor of an unstable hadron within a first principles approach to QCD.

   hep-phhep-latPRD(2016)·121 citations
3. 03*

   Mapping the genuine bosonic quartic couplings

   O. J. P. Eboli🇧🇷 · M. C. Gonzalez-Garcia🇪🇸

   The larger center-of-mass energy of the Large Hadron Collider Run 2 opens up the possibility of a more detailed study of the quartic vertices of the electroweak gauge bosons. Our goal in this work is to classify all operators possessing quartic interactions among the electroweak gauge bosons that do not exhibit triple gauge-boson vertices associated to them. We obtain all relevant operators in the non-linear and linear realizations of the $SU(2{)}_L\otimes U(1{)}_Y$ gauge symmetry.

   hep-phhep-exPRD(2016)·125 citations
4. 04*

   General CPT-even dimension-five nonminimal couplings between fermions and photons yielding EDM and MDM

   Jonas B. Araujo🇧🇷 · Rodolfo Casana🇧🇷 · Manoel M. Ferreira Jr🇧🇷

   In this letter, we examine a new class of CPT-even nonminimal interactions, between fermions and photons, deprived of higher order derivatives, that yields electric dipole moment (EDM) and magnetic dipole moment (MDM) in the context of the Dirac equation. The couplings are dimension-five CPT-even and Lorentz-violating nonminimal structures, composed of a rank-2 tensor, $T_{\mu \nu }$, the electromagnetic tensor, and gamma matrices, being addressed in its axial and non-axial Hermitian versions, and also comprising general possibilities. We then use the electron's anomalous magnetic dipole moment and electron electric dipole moment measurements to reach upper bounds of $1$ part in $10^{20}$ and $10^{25}$ (eV )${}^{-1}$.

   hep-phhep-thPLB(2016)·41 citations
5. 05*

   A model for the LHC diboson excess

   Manuel Buen-Abad🇺🇸 · Andrew G. Cohen🇺🇸 · Martin Schmaltz🇺🇸

   The first run of the LHC showed hints of a new resonance with mass near $1.9$ TeV decaying into electroweak gauge boson pairs as well as into dijets. While Run 2 has neither confirmed nor ruled out such a resonance, it has yielded new constraints on models attempting to explain these decays. Additionally in $W^{\prime }$ models where this new resonance is a charged vector boson that is a weak isospin singlet there is the potential for conflict with the electroweak precision $T$ parameter. We construct variants of a $W^{\prime }$ resonance model that provide an excellent fit to both Run 1 and Run 2 data, as well as electroweak precision measurements. The model also predicts a neutral vector boson, a $Z^{\prime }$, with mass close to $3$ TeV. This $Z^{\prime }$ is compatible with the intriguing Run 2 observation of a dielectron pair with invariant mass of $2.9$ TeV at CMS.

   hep-phJHEP(2016)·2 citations
6. 06*

   750 GeV Diphotons and Supersymmetric Grand Unification

   Hans Peter Nilles🇩🇪 · Martin Wolfgang Winkler🇩🇪

   We investigate the 750 GeV diphoton excess in terms of supersymmetric models which preserve grand unification in the ultraviolet. We show that minimal extensions of the MSSM by a singlet and a vector-like 5-plet or 10-plet of SU(5) can explain the observed signal while remaining perturbative up to the GUT scale. Different from previous analyses we rely on light sfermions in the loops which - compared to the analog non-supersymmetric models - enhance the diphoton cross section by up to a factor of seven. While the resonance decay width is narrow, mass splitting of the scalar and pseudoscalar components may result in a double resonance. We perform a likelihood analysis on the ATLAS and CMS data to show that the significance of the diphoton excess increases from 3.3 sigma (single narrow resonance) to 3.9 sigma for the double resonance. We also provide signal predictions in other diboson channels to be tested at LHC-13.

   hep-phJHEP(2016)·25 citations
7. 07*

   An explanation of one loop induced $h\to \mu \tau$ decay

   Seungwon Baek🇰🇷 · Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼

   We discuss a possibility to explain the excess of $h\to \mu \tau$ at one-loop level. We introduce three generation of vector-like lepton doublet $L^{\prime }$ and two singlet scalars $S_{1,2}$ which are odd under $Z_2$, while all the standard model fields are even under this discrete symmetry. We show that $S_1$ can be a good dark matter candidate. We show that we can explain the dark matter relic abundance, large part of the discrepancy of muon $g-2$ between experiments and the standard model predictions, as well as the $h\to \mu \tau$ excess of $\sim 1$ %, while evading constraints from experiments of dark matter direct detection and charged lepton flavor violating processes. We also consider prospects of production of $S_2$ at LHC with energy $\sqrt{s}=14$ TeV.

   hep-phhep-exPLB(2016)·54 citations
8. 08*

   A global analysis of two-body D to VP decays within the framework of flavor symmetry

   Hai-Yang Cheng🇹🇼 · Cheng-Wei Chiang🇹🇼 · An-Li Kuo🇹🇼

   Two-body charmed meson decays $D\to VP$ are studied within the framework of the diagrammatic approach. Under flavor SU(3) symmetry, all the flavor amplitude sizes and their associated strong phases are extracted by performing a ${\chi }^2$ fit. Thanks to the recent measurement of $D_s^{+}\to {\pi }^{+}{\rho }^0$, the magnitudes and the strong phases of the $W$-annihilation amplitudes $A_{P,V}$ have been extracted for the first time. As a consequence, the branching fractions of all the $D\to VP$ decays are predicted, especially those modes that could not be predicted previously due to the unknown $A_{P,V}$. Our working assumption, the flavor SU(3) symmetry, is tested by comparing our predictions with experiment for the singly and doubly Cabibbo-suppressed decay modes based on the flavor amplitudes extracted from the Cabibbo-favored decays using the current data. The predictions for the doubly Cabibbo-suppressed channels are in good agreement with the data, while those for the singly Cabibbo-suppressed decay modes are seen to have flavor SU(3) symmetry breaking effects. We find that the inclusion of SU(3) symmetry breaking in color-allowed and color-suppressed tree amplitudes is needed in general in order to have a better agreement with experiment. Nevertheless, the exact flavor SU(3)-symmetric approach alone is adequate to provide an overall explanation for the current data.

   hep-phhep-exPRD(2016)·65 citations
9. 09*

   Compact pentaquark structures

   Elena Santopinto🇮🇹 · Alessandro Giachino🇮🇹

   We study the possibility that at least one of the two pentaquark structures recently reported by LHCb can be described as a compact pentaquark state, and we give predictions for new channels that can be studied by the experimentalists if this hypothesis is correct. We use very general arguments dictated by symmetry considerations, in order to describe the pentaquark states within a group theory approach. A complete classification of all possible states and quantum numbers, that can be useful both to the experimentalists, for new finding, or to theoretical model builders, are given, without the introduction of any particular dynamical model. Some prediction are finally given using a Guersey-Radicati inspired mass formula. We reproduce the mass and the quantum numbers of the lightest pentaquark state reported by LHCb ( 3/2^-), with a parameter free mass formula, fixed on the well established baryons. We predict others pentaquark resonances (giving their masses, and suggesting possible decay channels) which belong to the same multiplet of the lightest one.Finally, we compute the partial decay widths for all the predicted pentaquark resonances.

   hep-phPRD(2017)·112 citations
10. 10*

    Meson electro-/photo-production from QCD

    Raúl A. Briceño🇺🇸

    I present the calculation of the ${\pi }^{+}{\gamma }^{\star }\to {\pi }^{+}{\pi }^0$ transition amplitude from quantum chromodynamics performed by the Hadron Spectrum Collaboration. The amplitude is determined for a range of values of the photon virtuality and the final state energy. One observes a clear dynamical enhancement due to the presence of the $\rho$ resonance. By fitting the transition amplitude and analytically continuing it onto the $\rho$-pole, the $\rho \to \pi {\gamma }^{\star }$ form factor is obtained. This exploratory calculation, performed using lattice quantum chromodynamics, constitutes the very first determination of an electroweak decay of a hadronic resonance directly from the fundamental theory of quarks and gluons. In this talk, I highlight some of the necessary steps that made this calculation possible, placing emphasis on recently developed formalism. Finally, I discuss the status and outlook of the field for the study of $N{\gamma }^{\star }\to N^{\star }\to N\pi$ transitions.

    hep-phhep-latFew Body Syst.(2016)·0 citations
11. 11*

    Exclusive Jet Measurement in Special LHC Runs - Feasibility Studies

    M. Trzebinski🇵🇱

    The feasibility studies of the central exclusive jet production at the LHC using the proton tagging technique are presented. Three classes of data taking scenarios are considered: double tag at high pile-up, single tag at low pile-up and double tag at low pile-up. Analyses were performed at the c.m. energy of 14 TeV for the ATLAS experiment, but are also valid for the CMS/TOTEM detectors.

    hep-phhep-exActa Phys.Polon.B(2016)·4 citations
12. 12*

    Landau-Khalatnikov-Fradkin transformations in Reduced Quantum Electrodynamics

    A. Ahmad🇲🇽 · J. J. Cobos-Martínez🇲🇽 · Y. Concha-Sánchez🇲🇽 · A. Raya🇲🇽

    We derive the Landau-Khalatnikov-Frandkin transformation (LKFT) for the fermion propagator in quantum electrodynamics (QED) described within a brane-world inspired framework where photons are allowed to move in $d_{\gamma }$ space-time (bulk) dimensions, while electrons remain confined to a $d_e$-dimensional brane, with $d_e<d_{\gamma }$, referred to in the literature as reduced quantum electrodynamics, RQED${}_{d_{\gamma },d_e}$. Specializing to the case of graphene, namely, RQED${}_{4,3}$ with massless fermions, we derive the nonperturbative form of the fermion propagator starting from its bare counterpart and then compare its weak coupling expansion to known one- and two-loop perturbative results. The agreement of the gauge-dependent terms of order $\alpha$ and ${\alpha }^2$ is reminiscent from the structure of LKFT in ordinary QED in arbitrary space-time dimensions and provides strong constraints for the multiplicative renormalizability of RQED${}_{d_{\gamma },d_e}$.

    hep-phhep-thPRD(2016)·27 citations
13. 13*

    Theoretical study of photoproduction of ${\eta }^{\prime }N$ bound state on deuteron target with forward proton emission

    Takayasu Sekihara (Osaka U., Res. Ctr. Nucl. Phys.)🇯🇵 · Shuntaro Sakai (Kyoto U.)🇯🇵 · Daisuke Jido (Tokyo Metropolitan U.)🇯🇵

    Possibilities of observing a signal of an ${\eta }^{\prime }n$ bound state are investigated by considering photoproductions of the $\eta$ and ${\eta }^{\prime }$ mesons on a deuteron target with forward proton emission. For this purpose, we take the ${\eta }^{\prime }n$ interaction from the linear sigma model with a coupling to $\eta n$, in which an $s$-wave ${\eta }^{\prime }n$ bound state can be dynamically generated, and we fix the $\gamma p\to \eta p$ and ${\eta }^{\prime }p$ scattering amplitudes so as to reproduce the experimental cross sections with forward proton emission. By using these $\gamma p\to {\eta }^{(\prime )}p$ and ${\eta }^{(\prime )}n\to {\eta }^{(\prime )}n$ amplitudes, we calculate cross sections of the $\gamma d\to \eta np$ and ${\eta }^{\prime }np$ reactions with forward proton emission in single and ${\eta }^{(\prime )}$-exchange double scattering processes. As a result, we find that the signal of the ${\eta }^{\prime }n$ bound state can be seen below the ${\eta }^{\prime }n$ threshold in the $\eta n$ invariant mass spectrum of the $\gamma d\to \eta np$ reaction and is comparable with the contribution from the quasifree ${\eta }^{\prime }$ production above the ${\eta }^{\prime }n$ threshold. We also discuss the behavior of the signal of the ${\eta }^{\prime }n$ bound state in several experimental conditions and model parameters.

    ↳ nucl-thhep-phnucl-exPRC(2016)·4 citations
14. 14*

    Tests of gravitational symmetries with radio pulsars

    Lijing Shao🇩🇪 · Norbert Wex🇩🇪

    Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies, time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle (SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.

    ↳ gr-qcastro-ph.HEhep-phSCPMA(2016)·55 citations
15. 15*

    A Rotation/Magnetism Analogy for the Quark-Gluon Plasma

    Brett McInnes🇸🇬

    In peripheral heavy ion collisions, the Quark-Gluon Plasma that may be formed often has a large angular momentum per unit energy. This angular momentum may take the form of (local) rotation. In many physical systems, rotation can have effects analogous to those produced by a magnetic field; thus, there is a risk that the effects of local rotation in the QGP might be mistaken for those of the large genuine magnetic fields which are also known to arise in these systems. Here we use the gauge-gravity duality to investigate this, and we find indeed that, with realistic parameter values, local rotation has effects on the QGP (at high values of the baryonic chemical potential) which are not only of the same kind as those produced by magnetic fields, but which can in fact be substantially larger. Furthermore, the combined effect of rotation and magnetism is to change the shape of the main quark matter phase transition line in an interesting way, reducing the magnitude of its curvature; again, local rotation contributes to this phenomenon at least as strongly as magnetism.

    ↳ hep-thhep-phnucl-thNPB(2016)·43 citations
16. 16*

    Nondiffractive feature of $\gamma N\to {\rho }^{\pm }N$ with $\rho$-meson electromagnetic multipole moments

    Byung-Geel Yu🇰🇷 · Kook-Jin Kong🇰🇷

    We investigate photoproduction of charged $\rho$ off the nucleon using $\rho (770)+\pi (140)$ Regge pole exchanges by considering the $\rho$-meson electromagnetic multipole moments. The significance of the Ward identity at the $\gamma \rho \rho$ vertex is emphasized for current conservation in the process. Given $\pi$ exchange with the well-known coupling constants for $\gamma \pi \rho$ and $\pi NN$, we analyze the role of the $\rho$ exchange in the $\gamma p\to {\rho }^{+}n$ and $\gamma n\to {\rho }^{-}p$ processes without model-dependences except for the magnetic moment ${\mu }_{{\rho }^{\pm }}=\pm 2.01$ and electric quadrupole moment ${\mathcal{Q}}_{{\rho }^{\pm }}=\pm 0.027$ fm${}^2$ taken from theoretical estimates. The nondiffractive feature of both cross sections is reproduced with a rapid decrease beyond the resonance region by the dominance of $\pi$ exchange over the $\rho$\,. % Cross sections for differential and density matrix elements are presented to compare with existing data. The parity and photon polarization asymmetries are predicted to demonstrate the apparent roles of the $\rho$-meson electromagnetic multipole moments.

    ↳ nucl-thhep-phPLB(2017)·6 citations
17. 17*

    Dark matter astrophysical uncertainties and the neutrino floor

    Ciaran A. J. O'Hare🇬🇧

    The search for weakly interacting massive particles (WIMPs) by direct detection faces an encroaching background due to coherent neutrino-nucleus scattering. For a given WIMP mass the cross section at which neutrinos constitute a dominant background is dependent on the uncertainty on the flux of each neutrino source from either the Sun, supernovae or atmospheric cosmic ray collisions. However there are also considerable uncertainties with regard to the astrophysical ingredients to the predicted WIMP signal. Uncertainties in the velocity of the Sun with respect to the Milky Way dark matter halo, the local density of WIMPs, and the shape of the local WIMP speed distribution all have an effect on the expected event rate in direct detection experiments and hence will change the region of the WIMP parameter space for which neutrinos are a significant background. In this work we extend the WIMP+neutrino analysis to account for the uncertainty in the astrophysics dependence of the WIMP signal. We show the effect of uncertainties on projected discovery limits with an emphasis on low WIMP masses (less than 10 GeV) when Solar neutrino backgrounds are most important. We find that accounting for astrophysical uncertainties changes the shape of the neutrino floor as a function of WIMP mass but also causes it to appear at cross sections up to an order of magnitude larger, extremely close to existing experimental limits - indicating that neutrino backgrounds will become an issue sooner than previously thought. We also explore how neutrinos hinder the estimation of WIMP parameters and how astrophysical uncertainties impact the discrimination of WIMPs and neutrinos with the use of their respective time dependencies.

    ↳ astro-ph.COhep-phPRD(2016)·88 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.