Tue·May 10, 2016Tuesday·May 10, 2016

1. 01*

   Reactor Neutrino Spectra

   A. C. Hayes🇺🇸 · Petr Vogel🇺🇸

   We present a review of the antineutrino spectra emitted from reactors. Knowledge of these and their associated uncertainties are crucial for neutrino oscillation studies. The spectra used to-date have been determined by either conversion of measured electron spectra to antineutrino spectra or by summing over all of the thousands of transitions that makeup the spectra using modern databases as input. The uncertainties in the subdominant corrections to beta-decay plague both methods, and we provide estimates of these uncertainties. Improving on current knowledge of the antineutrino spectra from reactors will require new experiments. Such experiments would also address the so-called reactor neutrino anomaly and the possible origin of the shoulder observed in the antineutrino spectra measured in recent high-statistics reactor neutrino experiments.

   hep-phnucl-thAnn.Rev.Nucl.Part.Sci.(2016)·176 citations
2. 02*

   Resummation of Goldstone boson contributions to the MSSM effective potential

   Nilanjana Kumar🇺🇸 · Stephen P. Martin🇺🇸

   We discuss the resummation of the Goldstone boson contributions to the effective potential of the Minimal Supersymmetric Standard Model (MSSM). This eliminates the formal problems of spurious imaginary parts and logarithmic singularities in the minimization conditions when the tree-level Goldstone boson squared masses are negative or approach zero. The numerical impact of the resummation is shown to be almost always very small. We also show how to write the two-loop minimization conditions so that Goldstone boson squared masses do not appear at all, and so that they can be solved without iteration.

   hep-phPRD(2016)·25 citations
3. 03*

   APFELgrid: a high performance tool for parton density determinations

   Valerio Bertone🇬🇧 · Stefano Carrazza🇨🇭 · Nathan P. Hartland🇬🇧

   We present a new software package designed to reduce the computational burden of hadron collider measurements in Parton Distribution Function (PDF) fits. The APFELgrid package converts interpolated weight tables provided by APPLgrid files into a more efficient format for PDF fitting by the combination with PDF and ${\alpha }_s$ evolution factors provided by APFEL. This combination significantly reduces the number of operations required to perform the calculation of hadronic observables in PDF fits and simplifies the structure of the calculation into a readily optimised scalar product. We demonstrate that our technique can lead to a substantial speed improvement when compared to existing methods without any reduction in numerical accuracy.

   hep-phhep-exComput.Phys.Commun.(2017)·76 citations
4. 04*

   A to Z of the Muon Anomalous Magnetic Moment in the MSSM with Pati-Salam at the GUT scale

   Alexander S. Belyaev🇬🇧 · José E. Camargo-Molina🇸🇪 · Steve F. King🇬🇧 · David J. Miller🇬🇧 · António P. Morais🇵🇹 · Patrick B. Schaefers🇬🇧

   We analyse the low energy predictions of the minimal supersymmetric standard model (MSSM) arising from a GUT scale Pati-Salam gauge group further constrained by an $A_4\times Z_5$ family symmetry, resulting in four soft scalar masses at the GUT scale: one left-handed soft mass $m_0$ and three right-handed soft masses $m_1,m_2,m_3$, one for each generation. We demonstrate that this model, which was initially developed to describe the neutrino sector, can explain collider and non-collider measurements such as the dark matter relic density, the Higgs boson mass and, in particular, the anomalous magnetic moment of the muon $(g-2{)}_{\mu }$. Since about two decades, $(g-2{)}_{\mu }$ suffers a puzzling about 3$\sigma$ excess of the experimentally measured value over the theoretical prediction, which our model is able to fully resolve. As the consequence of this resolution, our model predicts specific regions of the parameter space with the specific properties including light smuons and neutralinos, which could also potentially explain di-lepton excesses observed by CMS and ATLAS.

   hep-phJHEP(2016)·15 citations
5. 05*

   Automating QCD amplitudes with on-shell methods

   Simon Badger🇬🇧

   We review some of the modern approaches to scattering amplitude computations in QCD and their application to precision LHC phenomenology. We emphasise the usefulness of momentum twistor variables in parameterising general amplitudes.

   hep-phhep-thJ.Phys.Conf.Ser.(2016)·42 citations
6. 06*

   Revisiting T2KK and T2KO physics potential and ${\nu }_{\mu }$ - ${\bar{\nu }}_{\mu }$ beam ratio

   Kaoru Hagiwara🇯🇵 · Pyungwon Ko🇰🇷 · Naotoshi Okamura🇯🇵 · Yoshitaro Takaesu🇯🇵

   We revisit the sensitivity study of the Tokai-to-Kamioka-and-Korea (T2KK) and Tokai-to-Kamioka-and-Oki (T2KO) proposals where a water Cerenkov detector with the 100 kton fiducial volume is placed in Korea ($L=1000$ km) and Oki island ($L=653$ km) in Japan, respectively, in addition to the Super-Kamiokande for determination of the neutrino mass hierarchy and leptonic CP phase (${\delta }_{CP}$). We systematically study the running ratio of the ${\nu }_{\mu }$ and ${\bar{\nu }}_{\mu }$ focusing beams with dedicated background estimation for the ${\nu }_e$ appearance and ${\nu }_{\mu }$ disappearance signals, especially improving treatment of the neutral current ${\pi }^0$ backgrounds. Using a ${\nu }_{\mu }$ - ${\bar{\nu }}_{\mu }$ beam ratio between 3 : 2 and 2.5 : 2.5 (in unit of $10^{21}$POT with the proton energy of 40 GeV), the mass hierarchy determination with the median sensitivity of 3 - 5 $\sigma$ by the T2KK and 1 - 4 $\sigma$ by the T2KO experiment are expected when ${\sin }^2{\theta }_{23}=0.5$, depending on the mass hierarchy pattern and CP phase. These sensitivities are enhanced (reduced) by $30\%$ - $40\%$ in $\Delta {\chi }^2$ when ${\sin }^2{\theta }_{23}=0.6(0.4)$. The CP phase is measured with the uncertainty of $20^{\circ }$ - $50^{\circ }$ by the T2KK and T2KO using the ${\nu }_{\mu }$ - ${\bar{\nu }}_{\mu }$ focusing beam ratio between 3.5 : 1.5 and 1.5 : 3.5. These findings indicate that inclusion of the ${\bar{\nu }}_{\mu }$ focusing beam improves the sensitivities of the T2KK and T2KO experiments to both the mass hierarchy determination and leptonic CP phase measurement simultaneously with the preferred beam ratio being between 3 : 2 - 2.5 : 2.5 ($\times 10^{21}$POT).

   hep-phEPJC(2017)·8 citations
7. 07*

   A dynamical quasiparticle approach for the Quark-Gluon-Plasma bulk and transport properties

   Hamza Berrehrah🇩🇪 · Elena Bratkovskaya🇩🇪 · Thorsten Steinert🇩🇪 · Wolfgang Cassing🇩🇪

   The properties of quantum-chromo dynamics (QCD) nowadays are accessable by lattice QCD calculations at vanishing quark chemical potential ${\mu }_q$=0 but often lack a transparent physical interpretation. In this review we report about results from an extended dynamical quasiparticle model (DQPM${}^{\ast }$) in which the effective parton propagators have a complex selfenergy that depends on the temperature $T$ of the medium as well as on the chemical potential ${\mu }_q$ and the parton three-momentum $\mathbf{p}$ with respect to the medium at rest. It is demonstrated that this approach allows for a good description of QCD thermodynamics with respect to the entropy density, pressure etc. above the critical temperature $T_c\approx$ 158 MeV. Furthermore, the quark susceptibility ${\chi }_q$ and the quark number density $n_q$ are found to be reproduced simultaneously at zero and finite quark chemical potential. The shear and bulk viscosities $\eta ,\zeta$, and the electric conductivity ${\sigma }_e$ from the DQPM${}^{\ast }$ also turn out in close agreement with lattice results for ${\mu }_q$ =0. The DQPM${}^{\ast }$, furthermore, allows to evaluate the momentum $p$, $T$ and ${\mu }_q$ dependencies of the partonic degrees of freedom also for larger ${\mu }_q$ which are mandatory for transport studies of heavy-ion collisions in the regime 5 GeV $<\sqrt{s_{NN}}<$ 10 GeV. We finally calculate the charm quark diffusion coefficient $D_s$ -- evaluated from the differential cross sections of partons in the medium for light and heavy quarks by employing the propagators and couplings from the DQPM -- and compare to the available lattice data. It is argued that the complete set of observables allows for a transparent interpretation of the properties of hot QCD.

   hep-phnucl-thIJMPE(2016)·68 citations
8. 08*

   Production of $Y(4260)$ as a hadronic molecule state of $\bar{D}{D}_1+c.c.$ in $e^{+}{e}^{-}$ annihilations

   Wen Qin🇨🇳 · Si-Run Xue🇨🇳 · Qiang Zhao🇨🇳

   We study the $Y(4260)$ production mechanism in $e^{+}{e}^{-}$ annihilations in the framework of hadronic molecules and investigate the consequence of such a picture in different decay channels. In the hadronic molecule picture the $Y(4260)$ is described as a mixture state composed of a long-ranged $\bar{D}{D}_1(2420)+c.c.$ molecule state and a compact $c\bar{c}$ component. We show that the compositeness relation can still provide a reasonable constraint on the wavefunction renormalization parameter due to the dominance of the molecular component. Such a mechanism can be regarded as a natural consequence of the heavy quark spin symmetry (HQSS) breaking. This study elaborates the molecular picture for the $Y(4260)$ in the $e^{+}{e}^{-}$ annihilations and affirms that the cross section lineshape of $e^{+}{e}^{-}\to \bar{D}{D}^{\ast }\pi +c.c.$ in the vicinity of the $Y(4260)$ should have a nontrivial behavior. In this framework we predict that the upper limit of the $Y(4260)$ leptonic decay width is about 500 eV. We also investigate the coupling for $D_1(2420)\to D^{\ast }\pi$ in the ${}^3{P}_0$ quark model and examine the possible HQSS breaking effects due to the deviation from the ${|}^1{P}_1⟩$ and ${|}^3{P}_1⟩$ ideal mixing. This will in turn provide a constraint on the HQSS breaking coupling for the $Y(4260)$ to $\bar{D}{D}_1(2420)+c.c.$ via its $c\bar{c}$ component.

   hep-phhep-exnucl-exnucl-thPRD(2016)·53 citations
9. 09*

   Application of the QCD light cone sum rule to tetraquarks: the strong vertices $X_b{X}_b\rho$ and $X_c{X}_c\rho$

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

   The full version of QCD light-cone sum rule method is applied to tetraquarks containing a single heavy $b$ or $c$ quark. To this end, investigations of the strong vertices $X_b{X}_b\rho$ and $X_c{X}_c\rho$ are performed, where $X_b=[su][\bar{b}\bar{d}]$ and $X_c=[su][\bar{c}\bar{d}]$ are the exotic states built of four quarks of different flavors. The strong coupling constants $G_{X_b{X}_b\rho }$ and $G_{X_c{X}_c\rho }$ corresponding to these vertices are found using the $\rho$-meson leading and higher-twist distribution amplitudes. In the calculations $X_b$ and $X_c$ are treated as scalar bound states of a diquark and antidiquark.

   hep-phPRD(2016)·30 citations
10. 10*

    Right-right-left extension of the standard model

    Gauhar Abbas🇪🇸

    A right-right-left extension of the standard model is proposed. In this model, the standard model gauge group $SU(2{)}_L\otimes U(1{)}_Y$ is extended to $SU(2{)}_L\otimes SU(2{)}_R\otimes SU(2{)}_R^{\prime }\otimes SU(2{)}_L^{\prime }\otimes U(1{)}_Y$. The gauge symmetries $SU(2{)}_R^{\prime }$, $SU(2{)}_L^{\prime }$ are the mirror counter-parts of the $SU(2{)}_L$ and $SU(2{)}_R$ respectively. Parity is spontaneously broken when the scalar Higgs fields acquire vacuum-expectation values in a certain pattern. Parity is restored at the scale of $SU(2{)}_L^{\prime }$. The gauge sector has a unique pattern. The scalar sector of the model is optimum, elegant and unique.

    hep-phMod.Phys.Lett.A(2016)·12 citations
11. 11*

    Electroweak production of light scalar-pseudoscalar pairs from extended Higgs sectors

    Rikard Enberg🇸🇪 · William Klemm🇸🇪 · Stefano Moretti🇬🇧 · Shoaib Munir🇰🇷

    In models with extended Higgs sectors, it is possible that the Higgs boson discovered at the LHC is not the lightest one. We show that in a realistic model (the Type I 2-Higgs Doublet Model), when the sum of the masses of a light scalar and a pseudoscalar ($h$ and $A$) is smaller than the $Z$ boson mass, the Electroweak (EW) production of an $hA$ pair can dominate over QCD production by orders of magnitude, a fact not previously highlighted. This is because in the $gg$-initiated process, $hA$ production via a resonant $Z$ in the $s$-channel is prohibited according to the Landau-Yang theorem, which is not the case for the $q\bar{q}$-initiated process. We explore the parameter space of the model to highlight regions giving such $hA$ solutions while being consistent with all constraints from collider searches, $b$-physics and EW precision data. We also single out a few benchmark points to discuss their salient features, including the $hA$ search channels that can be exploited at Run II of the LHC.

    hep-phPLB(2017)·17 citations
12. 12*

    A Study of deuteron electromagnetic form factors with light-front approach

    Bao-dong Sun🇨🇳 · Yu-bing Dong🇨🇳

    The electromagnetic form factors and low-energy observables of deuteron are studied with the help of the light-front approach, where the deuteron is regarded as a weekly bound state of a proton and a neutron. Both the $S-$ and $D-$wave interacting vertexes among deuteron, proton, and neutron are taken into account. Moreover, the regularization functions are also introduced. In our calculations, the vertex and the regularization functions are employed to simulate the momentum distribution inside the deuteron. Our numerical results show that the light-front approach can roughly reproduce the deuteron electromagnetic form factors, like charge $G_0$, magnetic $G_1$, and quadrupole $G_2$, in the low $Q^2$ region. The important role of the $D-$wave vertex on $G_2$ is also addressed.

    hep-phCPC(2017)·13 citations
13. 13*

    Application of the Principle of Maximum Conformality to the Hadroproduction of the Higgs Boson at the LHC

    Sheng-Quan Wang🇨🇳 · Xing-Gang Wu🇨🇳 · Stanley J. Brodsky🇺🇸 · Matin Mojaza🇸🇪

    We present improved pQCD predictions for Higgs boson hadroproduction at the Large Hadronic Collider (LHC) by applying the Principle of Maximum Conformality (PMC), a procedure which resums the pQCD series using the renormalization group (RG), thereby eliminating the dependence of the predictions on the choice of the renormalization scheme while minimizing sensitivity to the initial choice of the renormalization scale. In previous pQCD predictions for Higgs boson hadroproduction, it has been conventional to assume that the renormalization scale ${\mu }_r$ of the QCD coupling ${\alpha }_s({\mu }_r)$ is the Higgs mass, and then to vary this choice over the range $1/2m_H<{\mu }_r<2m_H$ in order to estimate the theory uncertainty. However, this error estimate is only sensitive to the non-conformal $\beta$ terms in the pQCD series, and thus it fails to correctly estimate the theory uncertainty in cases where pQCD series has large higher order contributions, as is the case for Higgs boson hadroproduction. Furthermore, this \mbox{\it ad hoc} choice of scale and range gives pQCD predictions which depend on the renormalization scheme being used, in contradiction to basic RG principles. In contrast, after applying the PMC, we obtain next-to-next-to-leading order RG resummed pQCD predictions for Higgs boson hadroproduction which are renormalization-scheme independent and have minimal sensitivity to the choice of the initial renormalization scale. Taking $m_H=125$ GeV, the PMC predictions for the $pp\to HX$ Higgs inclusive hadroproduction cross-sections for various LHC center-of-mass energies and the fiducial cross section ${\sigma }_{\mathrm{fid}}(pp\to H\to \gamma \gamma )$ are presented...... The PMC predictions show better agreement with the ATLAS measurements than the LHC-XS predictions which are based on conventional renormalization scale-setting.

    hep-phhep-exPRD(2016)·14 citations
14. 14*

    An $SU(2{)}_L$ Septet Scalar Linking to Radiative Neutrino Model

    Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼 · Yuta Orikasa🇰🇷

    We study a radiative neutrino model with a SU(2) septet scalar with hypercharge $Y=2$ where active neutrino mass is induced at a one-loop level. Calculating a one-loop diagram, mass matrices for active neutrino is derived. We also analyze lepton flavor violations, anomalous magnetic moment of muon and the flavor violating Higgs decay $h\to \mu \tau$. Then sizable muon $g-2$ and $\sim 1\%$ of $BR(h\to \mu \tau )$ could be obtained in our set up. Furthermore, the collider signature of the septet is discussed where we focus on quadratically charged scalar at the LHC 14 TeV. We find that it could be discovered up to $1.5$ TeV mass by searching multi charged lepton signal events.

    hep-phhep-exPRD(2016)·33 citations
15. 15*

    Effective field theory for large logarithms in radiative corrections to electron proton scattering

    Richard J. Hill🇺🇸

    Radiative corrections to elastic electron-proton scattering are analyzed in effective field theory. A new factorization formula identifies all sources of large logarithms in the limit of large momentum transfer, $Q^2\gg m_e^2$. Explicit matching calculations are performed through two-loop order. A renormalization analysis in soft-collinear effective theory is performed to systematically compute and resum large logarithms. Implications for the extraction of charge radii and other observables from scattering data are discussed. The formalism may be applied to other lepton-nucleon scattering and $e^{+}{e}^{-}$ annihilation processes.

    hep-phhep-exnucl-exnucl-th+1PRD(2017)·47 citations
16. 16*

    Drell-Yan lepton angular distributions in perturbative QCD

    Martin Lambertsen🇩🇪 · Werner Vogelsang🇩🇪

    We present a comprehensive comparison of the available experimental data for the Drell-Yan lepton angular coefficients $\lambda$ and $\nu$ to calculations at leading and next-to-leading order of perturbative QCD. To obtain the next-to-leading order corrections, we make use of publicly available numerical codes that allow us to compute the Drell-Yan cross section at second order in perturbation theory and from which the contributions we need can be extracted. Our comparisons reveal that perturbative QCD is able to describe the experimental data overall rather well, especially at colliders, but also in the fixed-target regime. On the basis of the angular coefficients alone, there appears to be little (if any) convincing evidence for effects that go beyond fixed-order collinear factorized perturbation theory, although the presence of such effects is not ruled out.

    hep-phhep-exPRD(2016)·51 citations
17. 17*

    Unitarity and microscopic acausality in a nonlocal theory

    Christopher D. Carone🇺🇸

    We consider unitarity and causality in a higher-derivative theory of infinite order, where propagators fall off more quickly in the ultraviolet due to the presence of a transcendental entire function of the momentum. Like Lee-Wick theories, these field theories might provide new avenues for addressing the hierarchy problem; unlike Lee-Wick theories, tree-level propagators do not have additional poles corresponding to unobserved particles with unusual properties. We consider microscopic acausality in these nonlocal theories. The acausal ordering of production and decay vertices for ordinary resonant particles may provide a phenomenologically distinct signature for these models.

    ↳ hep-thhep-phPRD(2017)·35 citations
18. 18*

    Q-balls in the Wick-Cutkosky model

    E.Ya. Nugaev🇷🇺 · M.N. Smolyakov🇷🇺

    In the present paper Q-ball solutions in the Wick--Cutkosky model are examined in detail. A remarkable feature of the Wick--Cutkosky model is that it admits analytical treatment for the most part of the analysis of Q-balls, which allows one to use this simple model to demonstrate some peculiar properties of Q-balls. In particular, a method for estimating the binding energy of a Q-ball is proposed. This method is tested on the Wick--Cutkosky model taking into account the well-known results obtained for this model earlier.

    ↳ hep-thhep-phEPJC(2017)·9 citations
19. 19*

    Quasiparticle anisotropic hydrodynamics for central collisions

    Mubarak Alqahtani🇺🇸 · Mohammad Nopoush🇺🇸 · Michael Strickland🇺🇸

    We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state. We compare results obtained using the quasiparticle method with the standard method of imposing the equation of state in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio eta/s. We find that the three methods agree well for small shear viscosity to entropy density ratio, eta/s, but differ at large eta/s. We find, in particular, that when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative at large p_T which is clearly unphysical. Such a behavior is not seen in either anisotropic hydrodynamics approach, irrespective of the value of eta/s.

    ↳ nucl-thhep-phPRC(2017)·56 citations
20. 20*

    Primordial features and Planck polarization

    Dhiraj Kumar Hazra🇫🇷 · Arman Shafieloo🇰🇷 · George F. Smoot🇫🇷 · Alexei A. Starobinsky🇷🇺

    With the Planck 2015 Cosmic Microwave Background (CMB) temperature and polarization data, we search for possible features in the primordial power spectrum (PPS). We revisit the Wiggly Whipped Inflation (WWI) framework and demonstrate how generation of some particular primordial features can improve the fit to Planck data. WWI potential allows the scalar field to transit from a steeper potential to a nearly flat potential through a discontinuity either in potential or in its derivatives. WWI offers the inflaton potential parametrizations that generate a wide variety of features in the primordial power spectra incorporating most of the localized and non-local inflationary features that are obtained upon reconstruction from temperature and polarization angular power spectrum. At the same time, in a single framework it allows us to have a background parameter estimation with a nearly free-form primordial spectrum. Using Planck 2015 data, we constrain the primordial features in the context of Wiggly Whipped Inflation and present the features that are supported both by temperature and polarization. WWI model provides more than $13$ improvement in ${\chi }^2$ fit to the data with respect to the best fit power law model considering combined temperature and polarization data from Planck and B-mode polarization data from BICEP and Planck dust map. We use 2-4 extra parameters in the WWI model compared to the featureless strict slow roll inflaton potential. We find that the differences between the temperature and polarization data in constraining background cosmological parameters such as baryon density, cold dark matter density are reduced to a good extent if we use primordial power spectra from WWI. We also discuss the extent of bispectra obtained from the best potentials in arbitrary triangular configurations using the BI-spectra and Non-Gaussianity Operator (BINGO).

    ↳ astro-ph.COhep-phhep-thJCAP(2016)·66 citations
21. 21*

    Time-Sliced Perturbation Theory II: Baryon Acoustic Oscillations and Infrared Resummation

    Diego Blas🇨🇭 · Mathias Garny🇨🇭 · Mikhail M. Ivanov🇨🇭 · Sergey Sibiryakov🇨🇭

    We use time-sliced perturbation theory (TSPT) to give an accurate description of the infrared non-linear effects affecting the baryonic acoustic oscillations (BAO) present in the distribution of matter at very large scales. In TSPT this can be done via a systematic resummation that has a simple diagrammatic representation and does not involve uncontrollable approximations. We discuss the power counting rules and derive explicit expressions for the resummed matter power spectrum up to next-to leading order and the bispectrum at the leading order. The two-point correlation function agrees well with N-body data at BAO scales. The systematic approach also allows to reliably assess the shift of the baryon acoustic peak due to non-linear effects.

    ↳ astro-ph.COhep-phhep-thJCAP(2016)·242 citations
22. 22*

    Cutoff regulators in chiral nuclear effective field theory

    Bingwei Long🇨🇳 · Ying Mei🇺🇸

    Three-dimensional cutoff regulators are frequently employed in multi-nucleon calculations, but they violate chiral symmetry and Lorentz invariance. A cutoff regularization scheme is proposed to compensate systematically at subleading orders for these symmetry violations caused by regulator artifacts. This is especially helpful when a soft momentum cutoff has to be used for technical reasons. It is also shown that dimensional regularization can still be used for some Feynman (sub)diagrams while cutoff regulators are used for the rest.

    ↳ nucl-thhep-phPRC(2016)·13 citations
23. 23*

    From strong to weak coupling in holographic models of thermalization

    Sašo Grozdanov🇳🇱 · Nikolaos Kaplis🇳🇱 · Andrei O. Starinets🇬🇧

    We investigate the analytic structure of thermal energy-momentum tensor correlators at large but finite coupling in quantum field theories with gravity duals. We compute corrections to the quasinormal spectra of black branes due to the presence of higher derivative $R^2$ and $R^4$ terms in the action, focusing on the dual to $\mathcal{N}=4$ SYM theory and Gauss-Bonnet gravity. We observe the appearance of new poles in the complex frequency plane at finite coupling. The new poles interfere with hydrodynamic poles of the correlators leading to the breakdown of hydrodynamic description at a coupling-dependent critical value of the wave-vector. The dependence of the critical wave vector on the coupling implies that the range of validity of the hydrodynamic description increases monotonically with the coupling. The behavior of the quasinormal spectrum at large but finite coupling may be contrasted with the known properties of the hierarchy of relaxation times determined by the spectrum of a linearized kinetic operator at weak coupling. We find that the ratio of a transport coefficient such as viscosity to the relaxation time determined by the fundamental non-hydrodynamic quasinormal frequency changes rapidly in the vicinity of infinite coupling but flattens out for weaker coupling, suggesting an extrapolation from strong coupling to the kinetic theory result. We note that the behavior of the quasinormal spectrum is qualitatively different depending on whether the ratio of shear viscosity to entropy density is greater or less than the universal, infinite coupling value of $\hslash /4\pi k_B$. In the former case, the density of poles increases, indicating a formation of branch cuts in the weak coupling limit, and the spectral function shows the appearance of narrow peaks. We also discuss the relation of the viscosity-entropy ratio to conjectured bounds on relaxation time in quantum systems.

    ↳ hep-thcond-mat.str-elhep-phnucl-th+1JHEP(2016)·122 citations
24. 24*

    Detection of Supernova Neutrinos

    Inés Gil-Botella🇪🇸

    The neutrino burst from a core-collapse supernova can provide information about the star explosion mechanism and the mechanisms of proto neutron star cooling but also about the intrinsic properties of the neutrino such as flavor oscillations. One important question is to understand to which extent can the supernova and the neutrino physics be decoupled in the observation of a single supernova. The capabilities of present and future large underground neutrino detectors to yield information about the time and flavor dependent neutrino signal from a future galactic supernova are described in this paper. Neutrinos from past cosmic supernovae are also observable and their detection will improve our knowledge of the core-collapse rates and average neutrino emission. A comparison between the different experimental techniques is included.

    ↳ physics.ins-detastro-ph.HEastro-ph.IMhep-ex+18 citations
25. 25*

    Higgs Starobinsky Inflation

    Xavier Calmet🇬🇧 · Iberê Kuntz🇬🇧

    In this paper we point out that Starobinky inflation could be induced by quantum effects due to a large non-minimal coupling of the Higgs boson to the Ricci scalar. The Higgs Starobinsky mechanism provides a solution to issues attached to large Higgs field values in the early universe which in a metastable universe would not be a viable option. We verify explicitly that these large quantum corrections do not destabilize Starobinsky's potential.

    ↳ hep-thastro-ph.COgr-qchep-phEPJC(2016)·105 citations
26. 26*

    Schwinger pair creation in Dirac semimetals in the presence of external magnetic and electric fields

    R.A. Abramchuk🇷🇺 · M.A.Zubkov🇷🇺

    We discuss the Schwinger pair creation process for the system of massless Dirac fermions in the presence of constant external magnetic and electric fields. The pair production rate remains finite unlike the vacuum decay rate. In the recently discovered Dirac semimetals, where the massless Dirac fermions emerge, this pair production may be observed experimentally through the transport properties. We estimate its contribution to the ordinary conductivity of the semimetals.

    ↳ cond-mat.mes-hallhep-phPRD(2016)·10 citations
27. 27*

    Entropy Production and Effective Viscosity in Heavy-Ion Collisions

    Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

    Entropy production and an effective viscosity in central Au+Au collisions are estimated in a wide range of incident energies 3.3 GeV $\le \sqrt{s_{NN}}\le$ 39 GeV. The simulations are performed within a three-fluid model employing three different equations of state with and without deconfinement transition, which are equally good in reproduction of the momentum-integrated elliptic flow of charged particles in the considered energy range. It is found that more that 80\% entropy is prodused during a short early collision stage which lasts $\sim$1 fm/c at highest considered energies $\sqrt{s_{NN}}\ge$ 20 GeV. The estimated values of the viscosity-to-entropy ratio ($\eta /s$) are approximately the same in all considered scenarios. At final stages of the system expansion they range from $\sim$0.05 at highest considered energies to $\sim$0.5 lowest ones. It is found that the $\eta /s$ ratio decreases with the temperature ($T$) rise approximately as $\sim 1/T^4$ and exhibits a rather weak dependence on the net-baryon density.

    ↳ nucl-thhep-phEPJA(2016)·22 citations
28. 28*

    A local and BRST-invariant Yang-Mills theory within the Gribov horizon

    M. A. L. Capri🇧🇷 · D. Dudal🇧🇪 · D. Fiorentini🇧🇷 · M. S. Guimaraes🇧🇷 · I. F. Justo🇧🇪 · A. D. Pereira🇧🇷 · B. W. Mintz🇧🇷 · L. F. Palhares🇧🇷 · R. F. Sobreiro🇧🇷 · S. P. Sorella🇧🇷

    We present a local setup for the recently introduced BRST-invariant formulation of Yang-Mills theories for linear covariant gauges that takes into account the existence of gauge copies à la Gribov and Zwanziger. Through the convenient use of auxiliary fields, including one of the Stueckelberg type, it is shown that both the action and the associated nilpotent BRST operator can be put in local form. Direct consequences of this fully local and BRST-symmetric framework are drawn from its Ward identities: (i) an exact prediction for the longitudinal part of the gluon propagator in linear covariant gauges that is compatible with recent lattice results and (ii) a proof of the gauge-parameter independence of all correlation functions of local BRST-invariant operators.

    ↳ hep-thhep-lathep-phPRD(2016)·91 citations

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