Fri·Jul 31, 2015Friday·July 31, 2015

1. 01*

   Some Predictions of Diquark Model for Hidden Charm Pentaquark Discovered at the LHCb

   Guan-Nan Li🇹🇼 · Min He🇨🇳 · Xiao-Gang He🇨🇳

   The LHCb has discovered two new states with preferred $J^P$ quantum numbers $3/2^{-}$ and $5/2^{+}$ from ${\Lambda }_b$ decays. These new states can be interpreted as hidden charm pentaquarks. It has been argued that the main features of these pentaquarks can be described by diquark model. The diquark model predicts that the $3/2^{-}$ and $5/2^{+}$ are in two separate octet multiplets of flavor $SU(3)$ and there is also an additional decuplet pentaquark multiplet. Finding the states in these multiplets can provide crucial evidence for this model. The weak decays of b-baryon to a light meson and a pentaquark can have Cabibbo allowed and suppressed decay channels. We find that in the $SU(3)$ limit, for $U$-spin related decay modes the ratio of the decay rates of Cabibbo suppressed to Cabibbo allowed decay channels is given by $|V_{cd}{|}^2/|V_{cs}{|}^2$. There are also other testable relations for b-baryon weak decays into a pentaquark and a light pseudoscalar. These relations can be used as tests for the diquark model for pentaquark.

   hep-phJHEP(2015)·152 citations
2. 02*

   Testing ATLAS Diboson Excess with Dark Matter Searches at LHC

   Seng Pei Liew🇯🇵 · Satoshi Shirai🇩🇪

   The ATLAS collaboration has recently reported a 2.6 sigma excess in the search for a heavy resonance decaying into a pair of weak gauge bosons. Only fully hadronic final states are being looked for in the analysis. If the observed excess really originates from the gauge bosons' decays, other decay modes of the gauge bosons would inevitably leave a trace on other exotic searches. In this paper, we propose the use of the Z boson decay into a pair of neutrinos to test the excess. This decay leads to a very large missing energy and can be probed with conventional dark matter searches at the LHC. We discuss the current constraints from the dark matter searches and the prospects. We find that optimizing these searches may give a very robust probe of the resonance, even with the currently available data of the 8 TeV LHC.

   hep-phhep-exJHEP(2015)·17 citations
3. 03*

   Searches for Dark Matter at the LHC: A Multivariate Analysis in the Mono-$Z$ Channel

   Alexandre Alves🇧🇷 · Kuver Sinha🇺🇸

   We study dark matter (DM) production in the mono-Z channel at the 13 TeV LHC both in an effective field theory framework as well as in simplified models with vector mediators, using a multivariate analysis. For DM-quark effective operators with scalar, vector, and tensor couplings and DM mass of 100 GeV, the 5$\sigma$ reach in the DM interaction scale $\Lambda$ is around 2, 1, and 3 TeV, respectively, for 3 ab${}^{-1}$ and assuming a 5\% systematic uncertainty on the total background normalization. For simplified models with leptophobic vector mediators, the 5$\sigma$ reach for the mass of the mediator is 1.7 TeV also assuming a 5\% systematics and 3 ab${}^{-1}$ of integrated luminosity. The reach for the dark matter interaction scale obtained with the multivariate analysis using a likelihood function discriminant is at least twice as high as that obtained from a simple cut and count analysis, once systematics on the background normalization larger than a few percent are taken into account. Moreover, the reach is much more stable against degradation due these systematic uncertainties.

   hep-phhep-exPRD(2015)·28 citations
4. 04*

   Dark Matter, Shared Asymmetries, and Galactic Gamma Ray Signals

   Nayara Fonseca🇧🇷 · Lina Necib🇺🇸 · Jesse Thaler🇺🇸

   We introduce a novel dark matter scenario where the visible sector and the dark sector share a common asymmetry. The two sectors are connected through an unstable mediator with baryon number one, allowing the standard model baryon asymmetry to be shared with dark matter via semi-annihilation. The present-day abundance of dark matter is then set by thermal freeze-out of this semi-annihilation process, yielding an asymmetric version of the WIMP miracle as well as promising signals for indirect detection experiments. As a proof of concept, we find a viable region of parameter space consistent with the observed Fermi excess of GeV gamma rays from the galactic center.

   hep-phastro-ph.COJCAP(2016)·26 citations
5. 05*

   Explaining the CMS excesses, baryogenesis and neutrino masses in $E_6$ motivated $U(1{)}_N$ model

   Mansi Dhuria🇮🇳 · Chandan Hati🇮🇳 · Utpal Sarkar🇮🇳

   We study the superstring inspired $E_6$ model motivated $U(1{)}_N$ extension of the supersymmetric standard model to explore the possibility of explaining the recent excess CMS events and the baryon asymmetry of the universe in eight possible variants of the model. In light of the hints from short-baseline neutrino experiments at the existence of one or more light sterile neutrinos, we also study the neutrino mass matrices dictated by the field assignments and the discrete symmetries in these variants. We find that all the variants can explain the excess CMS events via the exotic slepton decay, while for a standard choice of the discrete symmetry four of the variants have the feature of allowing high scale baryogenesis (leptogenesis). For one other variant three body decay induced soft baryogenesis mechanism is possible which can induce baryon number violating neutron-antineutron oscillation. We also point out a new discrete symmetry which has the feature of ensuring proton stability and forbidding tree level flavor changing neutral current processes while allowing for the possibility of high scale leptogenesis for two of the variants. On the other hand, neutrino mass matrix of the $U(1{)}_N$ model variants naturally accommodates three active and two sterile neutrinos which acquire masses through their mixing with extra neutral fermions giving rise to interesting textures for neutrino masses.

   hep-phastro-ph.COhep-thPRD(2016)·18 citations
6. 06*

   Flavour-changing Higgs decays into bottom and strange quarks in supersymmetry

   G. Barenboim🇪🇸 · C. Bosch🇪🇸 · J.S. Lee🇰🇷 · M.L. López-Ibáñez🇪🇸 · O. Vives🇪🇸

   In this work, we explore the flavour changing decays $H_i\to bs$ in a general supersymmetric scenario. In these models, the flavour changing decays arise at loop-level but, originating from a dimension-four operator, do not decouple and may provide a first sign of new physics for heavy masses beyond collider reach. In the framework of the minimal supersymmetric extension of the Standard Model (MSSM), we find that the largest branching ratio of the lightest Higgs ($H_1$) is $\mathcal{O}(10^{-6})$ after imposing present experimental constraints. While heavy Higgs states may still present branching ratios $\mathcal{O}(10^{-3})$. In a more general supersymmetric scenario, where additional Higgs states may modify the Higgs mixings, the branching ratio BR($H_1\to bs$) can reach values $\mathcal{O}(10^{-4})$ , while heavy Higgses still remain at $\mathcal{O}(10^{-3})$. Although these values are clearly out of reach for the LHC, a full study in a linear collider environment could be worth pursuing.

   hep-phhep-exPRD(2015)·11 citations
7. 07*

   Heavy-Light Mesons In A Relativistic Model

   Jing-Bin Liu🇨🇳 · Mao-Zhi Yang🇨🇳

   We study the heavy-light mesons in a relativistic model, which is derived from the instantaneous Bethe-Salpeter equation by applying the Foldy-Wouthuysen transformation on the heavy quark. The kernel we choose is based on scalar confining and vector Coulomb potentials, the transverse interaction of the gluon exchange is also taken into account in this model. The spectra and wave functions of $D$, $D_s$, $B$, $B_s$ meson states are obtained. The spectra are calculated up to the order of $1/m_Q$, and wave functions are treated to leading order.

   hep-phCPC(2016)·15 citations
8. 08*

   Inhomogeneous chiral condensates and non-analyticity under an external magnetic field

   Kouji Kashiwa🇯🇵 · Tong-Gyu Lee🇯🇵 · Kazuya Nishiyama🇯🇵 · Ryo Yoshiike🇯🇵

   We investigate inhomogeneous chiral condensates, such as the so-called dual chiral density wave of dense quark matter, under an external magnetic field at finite real and imaginary chemical potentials. In a model-independent manner, we find that analytic continuation from imaginary to real chemical potential is not possible due to the singularity induced by inhomogeneous chiral condensates at zero chemical potential. From the discussion on the non-analyticity and methods used in lattice QCD simulations, e.g., Taylor expansion, and the analytic continuation with an imaginary chemical potential, it turns out that information on an inhomogeneous chiral condensed phase is missed in the lattice simulations at finite baryon chemical potentials unless the non-analyticity at zero chemical potential is correctly considered. We also discuss an exceptional case without such non-analyticity at zero chemical potential.

   hep-phhep-lathep-th6 citations
9. 09*

   Polarization of top quark as a probe of its chromomagnetic and chromoelectric couplings in $tW$ production at the Large Hadron Collider

   Saurabh D. Rindani🇮🇳 · Pankaj Sharma🇦🇺 · Anthony W. Thomas🇦🇺

   We study the sensitivity of the Large Hadron Collider (LHC) to top quark chromomagnetic (CMDM) and chromoelectric (CEDM) dipole moments and $Wtb$ effective couplings in single-top production in association with a $W^{-}$ boson, followed by semileptonic decay of the top. The $Wt$ single-top production mode helps to isolate the anomalous $ttg$ and $Wtb$ couplings, in contrast to top-pair production and other single-top production modes, where other new-physics effects can also contribute. We calculate the top polarization and the effects of these anomalous couplings on it at two centre-of-mass (cm) energies, 8 TeV and 14 TeV. As a measure of top polarization, we look at decay-lepton angular distributions in the laboratory frame, without requiring reconstruction of the rest frame of the top, and study the effect of the anomalous couplings on these distributions. We construct certain asymmetries to study the sensitivity of these distributions to top-quark couplings. We determine individual limits on the dominant couplings, viz., the real part of the CMDM $\mathrm{Re}{\rho }_2$, the imaginary part of the CEDM $\mathrm{Im}{\rho }_3$, and the real part of the tensor $Wtb$ coupling $\mathrm{Re}{\mathrm{f}}_{2R}$, which may be obtained by utilizing these asymmetries at the LHC. We also obtain simultaneous limits on pairs of these couplings taking two couplings to be non-zero at a time.

   hep-phJHEP(2015)·27 citations
10. 10*

    Basis invariant description of chemical equilibrium with implications for a recent axionic leptogenesis model

    Bowen Shi🇺🇸 · Stuart Raby🇺🇸

    We provide a systematic treatment of chemical equilibrium in the presence of a specific type of time dependent background. The type of time dependent background we consider appears, for example, in recently proposed axion/Majoron leptogenesis models [1,2]. In describing the chemical equilibrium we use quantities which are invariant under redefinition of fermion phases (we refer to this redefinition as a change of basis for short), and therefore it is a basis invariant treatment. The change of the anomaly terms due to the change of the path integral measure [3,4] under a basis change is taken into account. We find it is useful to go back and forth between different bases, and there are insights which can be more easily obtained in one basis rather than another. A toy model is provided to illustrate the ideas. For the axion leptogenesis model [1], our result suggests that at $T>10^{13}$ GeV , when sphaleron processes decouple, and ${\Gamma }_{B+L}<<H<{\Gamma }_L$ (where $H$ is the Hubble parameter at temperature $T$ and ${\Gamma }_L$ is the $\Delta L=2$ lepton number violating interaction rate), the amount of $B-L$ created is controlled by the smallness of the sphaleron interaction rate, ${\Gamma }_{B+L}$. Therefore it is not as efficient as described. In addition, we notice an interesting modification of gauge boson dispersion relations at subleading order.

    hep-phastro-ph.COhep-thPRD(2015)·8 citations
11. 11*

    Description of Heavy Quark $\overline{MS}$ Mass by Lippmann Schwinger Equation

    N. Tazimi🇮🇷 · M. Monemzadeh🇮🇷 · M. R. Hadizadeh🇧🇷

    Quark masses are of great prominence in high-energy physics. In this paper, we have studied the heavy meson systems via solving the Lippmann-Schwinger equation by using the Martin potential for heavy quark masses. We have also attempted to use Martin potential to find an acceptable mass spectrum for heavy quarkonia. We obtained this spectrum via minimal phenomenological model (M. Melles, Phys. Rev. D \textbf{62}: 074019 2000). The mass spectra for $b\bar{b}$ and $c\bar{c}$ are calculated without taking into account the relativistic corrections and spin-dependent effects. The obtained mass spectra turn out to fit the experimental findings. By using the conventional spectrum, we extract the pole mass of heavy quarks and use it along with the relation between $\overline{MS}$ mass (modified minimal subtraction scheme) and the on-shell quark mass to find $\overline{MS}$ mass for these quarks. The obtained results for $\overline{MS}$ mass are in good agreement with corresponding values reported in the literature.

    hep-phInt.J.Theor.Phys.(2012)·3 citations
12. 12*

    Searches for Beyond the Standard Model Physics at the LHC: Run1 Summary and Run2 Prospects

    Altan Cakir (for the CMS and ATLAS Collaborations)🇹🇷

    The search for new physics is a major goal of the LHC physics program. As excitement grows for the upcoming start of Run 2, I review the CMS and ATLAS searches for physics beyond the Standard Model from Run 1 and present recent analyses. These searches have covered a wide range of new physics scenarios including Supersymmetry, new resonances, additional Higgs bosons, new hidden sectors, other Dark Matter, and multi-charged particles. In addition to reviewing some of the techniques that made the analyses possible, I will summarize what we have learned from the results and briefly discuss prospects for Run 2.

    hep-phhep-exPoS(2015)·11 citations
13. 13*

    Observable Heavy Higgs Dark Matter

    Venus Keus🇫🇮 · Stephen F. King🇬🇧 · Stefano Moretti🇬🇧 · Dorota Sokolowska🇵🇱

    Dark Matter (DM), arising from an Inert Higgs Doublet, may either be light, below the $W$ mass, or heavy, above about 525 GeV. While the light region may soon be excluded, the heavy region is known to be very difficult to probe with either Direct Detection (DD) experiments or the Large Hadron Collider (LHC). We show that adding a second Inert Higgs Doublet helps to make the heavy DM region accessible to both DD and the LHC, by either increasing its couplings to the observed Higgs boson, or lowering its mass to $360\text{gev}\lesssim m_{DM}$, or both.

    hep-phJHEP(2015)·40 citations
14. 14*

    Radial Flow in Non-Extensive Thermodynamics and Study of Particle Spectra at LHC in the Limit of Small $(q-1)$

    Trambak Bhattacharyya🇮🇳 · Jean Cleymans🇿🇦 · Arvind Khuntia🇮🇳 · Pooja Pareek🇮🇳 · Raghunath Sahoo🇮🇳

    We expand the Tsallis distribution in a Taylor series of powers of (q-1), where q is the Tsallis parameter, assuming q is very close to 1. This helps in studying the degree of deviation of transverse momentum spectra and other thermodynamic quantities from a thermalized Boltzmann distribution. After checking thermodynamic consistency, we provide analytical results for the Tsallis distribution in the presence of collective flow up to the first order of (q-1). The formulae are compared with the experimental data.

    hep-phhep-exnucl-exnucl-thEPJA(2016)·90 citations
15. 15*

    Explanation of the ATLAS Z-peaked excess by squark pair production in the NMSSM

    Junjie Cao🇨🇳 · Liangliang Shang🇨🇳 · Jin Min Yang🇨🇳 · Yang Zhang🇨🇳

    The ATLAS collaboration recently reported a $3\sigma$ excess in the leptonic-$Z+jets+E_T^{miss}$ channel. We intend to interpret this excess by squark pair production in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The decay chain we employ is $\tilde{q}\to q{\tilde{\chi }}_2^0\to q{\tilde{\chi }}_1^{0}Z$, where ${\tilde{\chi }}_1^0$ and ${\tilde{\chi }}_2^0$ denote the lightest and the next-to-lightest neutralinos with singlino and bino as their dominant components respectively. Our simulations indicate that after considering the constraints from the ATLAS searches for $jets+E_T^{miss}$ signal the central value of the excess can be obtained for $m_{\tilde{q}}\lesssim 1.2\mathrm{TeV}$, and if the constraint from the CMS on-$Z$ search is further considered, more than 10 signal events are still attainable for $m_{\tilde{q}}\lesssim 750\mathrm{GeV}$. Compared with the interpretation by gluino pair production, the squark explanation allows for a significantly wider range of $m_{\tilde{q}}$ as well as a less compressed SUSY mass spectrum. We also show that the squark explanation will be readily tested at the initial stage of the 14 TeV LHC.

    hep-phJHEP(2015)·10 citations
16. 16*

    Comparison of the calorimetric and kinematic methods of neutrino energy reconstruction in disappearance experiments

    Artur M. Ankowski🇺🇸 · Omar Benhar🇮🇹 · Pilar Coloma🇺🇸 · Patrick Huber🇺🇸 · Chun-Min Jen🇺🇸 · Camillo Mariani🇺🇸 · Davide Meloni🇮🇹 · Erica Vagnoni🇮🇹

    To be able to achieve their physics goals, future neutrino-oscillation experiments will need to reconstruct the neutrino energy with very high accuracy. In this work, we analyze how the energy reconstruction may be affected by realistic detection capabilities, such as energy resolutions, efficiencies, and thresholds. This allows us to estimate how well the detector performance needs to be determined a priori in order to avoid a sizable bias in the measurement of the relevant oscillation parameters. We compare the kinematic and calorimetric methods of energy reconstruction in the context of two muon-neutrino disappearance experiments operating in different energy regimes. For the calorimetric reconstruction method, we find that the detector performance has to be estimated with a ~10% accuracy to avoid a significant bias in the extracted oscillation parameters. On the other hand, in the case of kinematic energy reconstruction, we observe that the results exhibit less sensitivity to an overestimation of the detector capabilities.

    hep-phhep-exPRD(2015)·46 citations
17. 17*

    Missing energy and the measurement of the CP-violating phase in neutrino oscillations

    Artur M. Ankowski🇺🇸 · Pilar Coloma🇺🇸 · Patrick Huber🇺🇸 · Camillo Mariani🇺🇸 · Erica Vagnoni🇮🇹

    In the next generation of long-baseline neutrino oscillation experiments, aiming to determine the charge-parity violating phase ${\delta }_{CP}$ in the appearance channel, fine-grained time-projection chambers are expected to play an important role. In this Letter, we analyze an influence of realistic detector capabilities on the ${\delta }_{CP}$ sensitivity for a setup similar to that of the Deep Underground Neutrino Experiment. We find that the effect of the missing energy, carried out by undetected particles, is sizable. Although the reconstructed neutrino energy can be corrected for the missing energy, the accuracy of such procedure has to exceed 20\%, to avoid a sizable bias in the extracted ${\delta }_{CP}$ value.

    hep-phhep-exPRD(2015)·48 citations
18. 18*

    $\theta$-dependence of the lightest meson resonances in QCD

    Neramballi Ripunjay Acharya🇩🇪 · Feng-Kun Guo🇩🇪 · Maxim Mai🇩🇪 · Ulf-G. Meißner🇩🇪

    We derive the pion mass and the elastic pion-pion scattering amplitude in the QCD theta-vacuum up to next-to-leading order in chiral perturbation theory. Using the modified inverse amplitude method, we study the theta-dependence of the mass and width of the light scalar meson sigma(500) and the vector meson rho(770).

    hep-phhep-lathep-thnucl-thPRD(2015)·19 citations
19. 19*

    Automation of electroweak corrections for LHC processes

    Mauro Chiesa🇮🇹 · Nicolas Greiner🇩🇪 · Francesco Tramontano🇮🇹

    For the Run 2 of the LHC next-to-leading order electroweak corrections will play an important role. Even though they are typically moderate at the level of total cross sections they can lead to substantial deviations in the shapes of distributions. In particular for new physics searches but also for a precise determination of Standard Model observables their inclusion in the theoretical predictions is mandatory for a reliable estimation of the Standard Model contribution. In this article we review the status and recent developments in electroweak calculations and their automation for LHC processes. We discuss general issues and properties of NLO electroweak corrections and present some examples, including the full calculation of the NLO corrections to the production of a W boson in association with two jets computed using GoSaM interfaced to MadDipole.

    hep-phhep-exJ.Phys.G(2016)·48 citations
20. 20*

    Constraining the double gluon distribution by the single gluon distribution

    Krzysztof Golec-Biernat🇵🇱 · Emilia Lewandowska🇵🇱 · Mirko Serino🇵🇱 · Zachary Snyder🇺🇸 · Anna M. Stasto🇺🇸

    We show how to consistently construct initial conditions for the QCD evolution equations for double parton distribution functions in the pure gluon case. We use to momentum sum rule for this purpose and a specific form of the known single gluon distribution function in the MSTW parameterization. The resulting double gluon distribution satisfies exactly the momentum sum rule and is parameter free. We also study numerically its evolution with a hard scale and show the approximate factorization into product of two single gluon distributions at small values of x, whereas at large values of x the factorization is always violated in agreement with the sum rule.

    hep-phPLB(2015)·49 citations
21. 21*

    The renormalization group step scaling function of the 2-flavor SU(3) sextet model

    Anna Hasenfratz🇺🇸 · Yuzhi Liu🇺🇸 · Cynthia Yu-Han Huang🇹🇼

    We investigate the discrete $\beta$ function of the 2-flavor SU(3) sextet model using the finite volume gradient flow scheme. Our results, using clover improved nHYP smeared Wilson fermions, follow the (non-universal) 4-loop $\overline{\text{MS}}$ perturbative predictions closely up to $g^2\approx 5.5$, the strongest coupling reached in our simulation. At strong couplings the results are in tension with a recently published work using the same gradient flow renormalization scheme with staggered fermions. Since these calculations define the discrete $\beta$ function in the same continuum renormalization scheme, they should lead to the same continuum predictions, irrespective of the lattice fermion action. In order to test systematic effects in our computation we compare two different lattice operators, three different flow definitions, and two volume extrapolations. We find agreement among these different approaches in the continuum limit when the gradient flow parameter $c\gtrsim 0.35$. Considering the potential phenomenological impact of this model, it is important to understand the origin of the disagreement between our work and the staggered fermion results.

    ↳ hep-lathep-ph31 citations
22. 22*

    Pure de Sitter Supergravity

    Eric A. Bergshoeff🇳🇱 · Daniel Z. Freedman🇺🇸 · Renata Kallosh🇺🇸 · Antoine Van Proeyen🇧🇪

    Using superconformal methods we derive an explicit de Sitter supergravity action invariant under spontaneously broken local $\mathcal{N}=1$ supersymmetry. The supergravity multiplet interacts with a nilpotent goldstino multiplet. We present a complete locally supersymmetric action including the graviton and the fermionic fields, gravitino and goldstino, no scalars. In the global limit when supergravity multiplet decouples, our action reproduces the Volkov-Akulov theory. In the unitary gauge where goldstino vanishes we recover pure supergravity with the positive cosmological constant. The classical equations of motion, with all fermions vanishing, have a maximally symmetric solution: de Sitter space.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2015)·166 citations
23. 23*

    Thomson scattering in high-intensity chirped laser pulses

    Amol R. Holkundkar🇮🇳 · Chris Harvey🇸🇪 · Mattias Marklund🇸🇪

    We consider the Thomson scattering of an electron in an ultra-intense chirped laser pulse. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the energy and intensity of the emitted radiation as compared to the case without chirping.

    ↳ physics.plasm-phhep-phPhys.Plasmas(2015)·9 citations
24. 24*

    A Test of Cosmological Models using high-z Measurements of H(z)

    Fulvio Melia🇺🇸 · Thomas M. McClintock🇺🇸

    The recently constructed Hubble diagram using a combined sample of SNLS and SDSS-II Type Ia SNe, and an application of the Alcock-Paczynski (AP) test using model-independent Baryon Acoustic Oscillation data, have suggested that the principal constraint underlying the cosmic expansion is the total equation-of-state of the cosmic fluid, rather than that of its dark energy. These studies have focused on the critical redshift range (0 < z < 2) within which the transition from decelerated to accelerated expansion is thought to have occurred, and they suggest that the cosmic fluid has zero active mass, consistent with a constant expansion rate. The evident impact of this conclusion on cosmological theory calls for an independent confirmation. In this paper, we carry out this crucial one-on-one comparison between the R_h=ct Universe (an FRW cosmology with zero active mass) and wCDM/LCDM, using the latest high-z measurements of H(z). Whereas the Type Ia SNe yield the integrated luminosity distance, while the AP diagnostic tests the geometry of the Universe, the Hubble parameter directly samples the expansion rate itself. We find that the model-independent cosmic chronometer data prefer R_h}=ct over wCDM/LCDM with a BIC likelihood of ~95% versus only ~5%, in strong support of the earlier SNeIa and AP results. This contrasts with a recent analysis of H(z) data based solely on BAO measurements which, however, strongly depend on the assumed cosmology. We discuss why the latter approach is inappropriate for model comparisons, and emphasize again the need for truly model-independent observations to be used in cosmological tests.

    ↳ astro-ph.COastro-ph.GAhep-phAstron.J.(2015)·33 citations
25. 25*

    Power spectrum oscillations from Planck-suppressed operators in effective field theory motivated monodromy inflation

    Layne C. Price🇳🇿

    We consider a phenomenological model of inflation where the inflaton is the phase of a complex scalar field $\Phi$. Planck-suppressed operators of $\mathcal{O}(f^5/M_{\mathrm{pl}})$ modify the geometry of the vev $⟨\Phi ⟩$ at first order in the decay constant $f$, which adds a first order periodic term to the definition of the canonically normalized inflaton $\varphi$. This correction to the inflaton induces a fixed number of extra oscillatory terms in the potential $V\sim {\theta }^p$. We derive the same result in a toy scenario where the vacuum $⟨\Phi ⟩$ is an ellipse with an arbitrarily large eccentricity. These extra oscillations change the form of the power spectrum as a function of scale $k$ and provide a possible mechanism for differentiating EFT-motivated inflation from models where the angular shift symmetry is a gauge symmetry.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2015)·6 citations
26. 26*

    Dynamical Mechanism of Two-Dimensional Plasmon Launching by Swift Electrons

    Xiao Lin · Xihang Shi · Fei Gao · Ido Kaminer · Zhaoju Yang · Zhen Gao · Hrvoje Buljan · John D. Joannopoulos · Marin Soljačić · Hongsheng Chen🇨🇳 · Baile Zhang

    Launching of surface plasmons by swift electrons has long been utilized in electron-energy-loss spectroscopy (EELS) to investigate plasmonic properties of ultrathin, or two-dimensional (2D), electron systems. However, its spatio-temporal process has never been revealed. This is because the impact of an electron will generate not only plasmons, but also photons, whose emission cannot be achieved at a single space-time point, as fundamentally determined from the uncertainty principle. Here, we propose that such a space-time limitation also applies to surface plasmon generation in EELS experiment. On the platform of graphene, we demonstrate within the framework of classical electrodynamics that the launching of 2D plasmons by an electron's impact is delayed after a hydrodynamic splashing-like process, which occurs during the plasmonic "formation time" when the electron traverses the "formation zone." Considering this newly revealed process, we show that previous estimates on the yields of graphene plasmons in EELS have been overestimated.

    ↳ physics.opticscond-mat.mtrl-scihep-ph0 citations
27. 27*

    N=1 superfield description of six-dimensional supergravity

    Hiroyuki Abe🇯🇵 · Yutaka Sakamura🇯🇵 · Yusuke Yamada🇯🇵

    We express the action of six-dimensional supergravity in terms of four-dimensional N=1 superfields, focusing on the moduli dependence of the action. The gauge invariance of the action in the tensor-vector sector is realized in a quite nontrivial manner, and it determines the moduli dependence of the action. The resultant moduli dependence is intricate, especially on the shape modulus. Our result is reduced to the known superfield actions of six-dimensional global SUSY theories and of five-dimensional supergravity by replacing the moduli superfields with their background values and by performing the dimensional reduction, respectively.

    ↳ hep-thhep-phJHEP(2015)·6 citations
28. 28*

    Consistency relations for sharp features in the primordial spectra

    Sander Mooij🇨🇱 · Gonzalo A. Palma🇨🇱 · Grigoris Panotopoulos🇨🇱 · Alex Soto🇨🇱

    We study the generation of sharp features in the primordial spectra within the framework of effective field theory of inflation, wherein curvature perturbations are the consequence of the dynamics of a single scalar degree of freedom. We identify two sources in the generation of features: rapid variations of the sound speed c_s (at which curvature fluctuations propagate) and rapid variations of the expansion rate H during inflation. With this in mind, we propose a non-trivial relation linking these two quantities that allows us to study the generation of sharp features in realistic scenarios where features are the result of the simultaneous occurrence of these two sources. This relation depends on a single parameter with a value determined by the particular model (and its numerical input) responsible for the rapidly varying background. As a consequence, we find a one-parameter consistency relation between the shape and size of features in the bispectrum and features in the power spectrum. To substantiate this result, we discuss several examples of models for which this one-parameter relation (between c_s and H) holds, including models in which features in the spectra are both sudden and resonant.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2015)·32 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.