Mon·Feb 19, 2018Monday·February 19, 2018

1. 01*

   Ghosts- and Tachyon-Free Regions of the Randall-Sundrum Model Parameter Space

   George N. Wojcik🇺🇸 · JoAnne L. Hewett🇺🇸 · Thomas G. Rizzo🇺🇸

   Model building within the Randall-Sundrum (RS) framework generally involves placing the Standard Model fields in the bulk. Such fields may possess non-zero values for their associated brane-localized kinetic terms (BLKTs) in addition to possible bulk mass parameters. In this paper we clearly identify the regions of the RS model parameter space where the presence of bulk mass terms and BLKTs yield a setup which is free from both ghost and tachyon instabilities. Such physically acceptable parameter space regions can then be used to construct realistic and phenomenologically viable RS models.

   hep-phJHEP(2018)·1 citation
2. 02*

   The formalism of neutrino oscillations: an introduction

   Guido Fantini🇮🇹 · Andrea Gallo Rosso🇮🇹 · Francesco Vissani🇮🇹 · Vanessa Zema🇮🇹

   The recent wide recognition of the existence of neutrino oscillations concludes the pioneer stage of these studies and poses the problem of how to communicate effectively the basic aspects of this branch of science. In fact, the phenomenon of neutrino oscillations has peculiar features and requires to master some specific idea and some amount of formalism. The main aim of these introductory notes is exactly to cover these aspects, in order to allow the interested students to appreciate the modern developments and possibly to begin to do research in neutrino oscillations.

   hep-phAdv.Ser.Direct.High Energy Phys.(2018)·65 citations
3. 03*

   Hadronic decays of the (pseudo-)scalar charmonium states ${\eta }_c$ and ${\chi }_{c0}$ in the extended Linear Sigma Model

   Walaa I. Eshraim🇩🇪 · Christian S. Fischer🇩🇪

   We study the phenomenology of the ground-state (pseudo-)scalar charmonia ${\eta }_c$ and ${\chi }_{c0}$ in the framework of a $U(4{)}_r\times U(4{)}_l$ symmetric linear sigma model with (pseudo-)scalar and (axial-) vector mesons. Based on previous results for the spectrum of charmonia and the spectrum and (OZI-dominant) strong decays of open charmed mesons, we extend the study of this model to OZI-suppressed charmonia decays. This includes decays into 'ordinary' mesons but also particularly interesting channels with scalar-isoscalar resonances $f_0(1370),f_0(1500),f_0(1710)$ that may include sizeable contributions from a scalar glueball. We study the variation of the corresponding decay widths assuming different mixings between glueball and quark-antiquark states. We also compute the decay width of the pseudoscalar ${\eta }_c$ into a pseudoscalar glueball. In general, our results for decay widths are in reasonable agreement with experimental data where available. Order of magnitude predictions for as yet unmeasured states and channels are potentially interesting for BESIII, Belle II, LHCb as well as the future PANDA experiment at the FAIR facility.

   hep-phEPJA(2018)·13 citations
4. 04*

   Ising-QCD phenomenology close to the critical point

   Nikolaos G. Antoniou🇬🇷 · Fotios K. Diakonos🇬🇷

   We employ the recently introduced Ising-QCD partition function (N.~G. Antoniou {\it et al.}, Phys. Rev. D 97, 034015 (2018)) to explore in detail the behaviour of the moments of the baryon-number, within the critical region around the critical endpoint. Our analysis is based on the relation of finite-size scaling in real space with intermittency in transverse momentum space. It demonstrates in practice the recent observation (N.~G. Antoniou {\it et al.}, Phys. Rev. D 97, 034015 (2018)) that combined measurements of the intermittency index ${\varphi }_2$ and the freeze-out parameters ${\mu }_b$ (baryochemical potential), $T$ (temperature), provide us with a powerful tool to detect the critical point. We also show that the finite-size scaling (FSS) region, as a part of the critical region, is very narrow in both the chemical potential and the temperature direction, even for light nuclei. Furthermore, using published experimental results for $({\mu }_b,T,{\varphi }_2)$ in A+A collisions at $\sqrt{s_{NN}}=17.2$ GeV (NA49 experiment, CERN-SPS), we are able to make a set of predictions for the freeze-out states of Ar + Sc and Xe + La collisions at the same energy in the NA61/SHINE experiment (CERN-SPS). In particular, we find that the Ar + Sc system freezes out outside the FSS region but very close to its boundary, a property which may leave characteristic traces in intermittency analysis.

   hep-phJ.Phys.G(2019)·12 citations
5. 05*

   Nuclear parton distribution functions

   Petja Paakkinen🇫🇮

   I review recent developments in the extraction of nuclear parton distribution functions. First describing the global analysis framework, I then present a comparison of the latest analyses in terms of included data and theoretical details, pointing out a few general trends.

   hep-phFrascati Phys.Ser.(2017)·14 citations
6. 06*

   Gamma rays from Dark Matter Annihilation in Three-loop Radiative Neutrino Mass Generation Models

   Talal Ahmed Chowdhury🇧🇩 · Salah Nasri🇦🇪

   We present the Sommerfeld enhanced Dark Matter (DM) annihilation into gamma ray for a class of three-loop radiative neutrino mass models with large electroweak multiplets where the DM mass is in O(TeV) range. We show that in this model, the DM annihilation rate becomes more prominent for larger multiplets and it is already within the reach of currently operating Imaging Atmospheric Cherenkov telescopes (IACTs), High Energy Stereoscopic System (H.E.S.S.). Furthermore, Cherenkov Telescope Array (CTA), which will begin operating in 2030, will improve this sensitivity by a factor of $\mathcal{O}(10)$ and may exclude a large portion of parameter space of this radiative neutrino mass model with larger electroweak multiplet. This implies that the only viable option is the model with lowest electroweak multiplets i.e. singlets of $SU(2{)}_L$ where the DM annihilation rate is not Sommerfeld enhanced and hence it is not yet constrained by the indirect detection limits from H.E.S.S. or future CTA.

   hep-phastro-ph.HEPLB(2018)·4 citations
7. 07*

   Studies of Lepton Flavor Violation at the LHC

   Bhubanjyoti Bhattacharya🇺🇸 · Robert Morgan🇺🇸 · James Osborne🇺🇸 · Alexey A. Petrov🇺🇸

   We examine the charged lepton flavor violating process $gg\to {\mu }^{\pm }{\tau }^{\mp }$ at the $\sqrt{s}=13$ TeV LHC. Operators generating this process can be induced by new physics (NP) at dimension 8. Despite the power suppression associated with dimension 8 operators, we show that the LHC's large gluon luminosity makes it possible to probe this channel. For an integrated luminosity of 100 fb${}^{-1}$ at the LHC, we predict a constraint on the NP scale $\Lambda \gtrsim 3$ TeV. In addition, we point out that such operators can be induced through top quark loops in models that generate dimension 6 operators of the form $\overline{t}t\mu \tau$. We find that the NP scale of these dimension 6 operators can be constrained to be $\Lambda \gtrsim 3.4-4.1$ TeV with 100 fb${}^{-1}$ of data.

   hep-phhep-exPLB(2018)·12 citations
8. 08*

   Landau Damping in a strong magnetic field: Dissociation of Quarkonia

   Mujeeb Hasan🇮🇳 · Binoy Krishna Patra🇮🇳 · Bhaswar Chatterjee🇮🇳 · Partha Bagchi🇮🇳

   We have investigated the effects of strong magnetic field on the properties of quarkonia immersed in a thermal medium of quarks and gluons and studied its quasi-free dissociation due to the Landau-damping. Thermalizing the Schwinger propagator in the lowest Landau levels for quarks and the Feynman propagator for gluons in real-time formalism, we have calculated the resummed retarded and symmetric propagators, which in turn give the real and imaginary components of dielectric permittivity, respectively. The magnetic field affects the large-distance interaction more than the short-distance interaction, as a result, the real part of potential becomes more attractive and the magnitude of imaginary part too becomes larger, compared to the thermal medium in absence of strong magnetic field. As a consequence the average size of $J/\psi$'s and ${\psi }^{\prime }$'s are increased but ${\chi }_c$'s get shrunk. Similarly the magnetic field affects the binding of $J/\psi$'s and ${\chi }_c$'s discriminately, i.e. it decreases the binding of $J/\psi$ and increases for ${\chi }_c$. However, the further increase in magnetic field results in the decrease of binding energies. On contrary the magnetic field increases the width of the resonances, unless the temperature is sufficiently high. We have finally studied how the presence of magnetic field affects the dissolution of quarkonia in a thermal medium due to the Landau damping, where the dissociation temperatures are found to increase compared to the thermal medium in absence of magnetic field. However, further increase of magnetic field decreases the dissociation temperatures. For example, $J/\psi$'s and ${\chi }_c$'s are dissociated at higher temperatures at 2 $T_c$ and 1.1 $T_c$ at a magnetic field $eB\approx 6\mathrm{and}4m_{\pi }^2$, respectively, compared to the values 1.60 $T_c$ and 0.8 $T_c$ in the absence of magnetic field, respectively.

   hep-phhep-thnucl-thNPA(2020)·25 citations
9. 09*

   Exclusive and diffractive ${\mu }^{+}{\mu }^{-}$ production in $pp$ collisions at the LHC

   V. P. Goncalves🇧🇷 · M. M. Jaime🇧🇷 · D. E. Martins🇧🇷 · M. S. Rangel🇧🇷

   In this paper we estimate the production of dimuons (${\mu }^{+}{\mu }^{-}$) in exclusive photon -- photon ($\gamma \gamma$) and diffractive Pomeron - Pomeron $(IPIP)$, Pomeron - Reggeon $(IPIR)$ and Reggeon - Reggeon $(IRIR)$ interactions in $pp$ collisions at the LHC energy. The invariant mass, rapidity and tranverse momentum distributions are calculated using the Forward Physics Monte Carlo (FPMC), which allows to obtain realistic predictions for the dimuon production with two leading intact hadrons. In particular, predictions taking into account the CMS and LHCb acceptances are presented. Moreover, the contribution of the single diffraction for the dimuon production also is estimated. Our results demonstrate that the experimental separation of these different mechanisms is feasible. In particular, the events characterized by pairs with large squared transverse momentum are dominated by diffractive interactions, which allows to investigate the underlying assumptions present in the description of these processes.

   hep-phhep-exPRD(2018)·12 citations
10. 10*

    Strong thermal $SO(10)$-inspired leptogenesis in the light of recent results from long-baseline neutrino experiments

    Marco Chianese🇬🇧 · Pasquale Di Bari🇬🇧

    We confront recent experimental results on neutrino mixing parameters with the requirements from strong thermal $SO(10)$-inspired leptogenesis, where the asymmetry is produced from next-to-lightest right-handed neutrinos $N_2$ independently of the initial conditions. There is a nice agreement with latest global analyses supporting $\sin \delta <0$ and normal ordering at $\sim 95\%$ C.L. On the other hand, the more stringent experimental lower bound on the atmospheric mixing angle starts to corner strong thermal $SO(10)$-inspired leptogenesis. Prompted and encouraged by this rapid experimental advance, we obtain a precise determination of the allowed region in the plane $\delta$ versus ${\theta }_{23}$. We confirm that for the benchmark case ${\alpha }_2\equiv m_{D2}/m_{\mathrm{charm}}=5$, where $m_{D2}$ is the intermediate neutrino Dirac mass setting the $N_2$ mass, and initial pre-existing asymmetry $N_{B-L}^{\mathrm{p},\mathrm{i}}=10^{-3}$, the bulk of solutions lies in the first octant. Though most of the solutions are found outside the $95\%$ C.L. experimental region, there is still a big allowed fraction that does not require a too fine-tuned choice of the Majorana phases so that the neutrinoless double beta decay effective neutrino mass allowed range is still $m_{ee}\simeq [10,30]\mathrm{meV}$. We also show how the constraints depend on $N_{B-L}^{\mathrm{p},\mathrm{i}}$ and ${\alpha }_2$. In particular, we show that the current best fit, (${\theta }_{23},\delta )\simeq (47^{\circ },-130^{\circ })$, can be reproduced for $N_{B-L}^{\mathrm{p},\mathrm{i}}=10^{-3}$ and ${\alpha }_2=6$. Such large values for ${\alpha }_2$ have been recently obtained in a few realistic fits within $SO(10)$-inspired models. Finally, we also obtain that current neutrino data rule out $N_{B-L}^{\mathrm{p},\mathrm{i}}\gtrsim 0.1$ for ${\alpha }_2\lesssim 4.7$.

    hep-phJHEP(2018)·18 citations
11. 11*

    Colour Confinement: a Dynamical Phenomenon of QCD

    Fei Gao🇨🇳 · Chong-yao Chen🇨🇳 · Yu-xin Liu🇨🇳

    We study in this Letter the origin of the confinement in QCD by analyzing the colour charge of physics states. We derive the colour charge operator in QCD and compare it with the electromagnetic charge operator in QED. It shows that the two charges have very similar structure, but the dynamical properties of the gauge fields are different. The difference between the behaviours of the gauge boson propagator at zero momentum for QCD and that for QED guarantees that there occurs colour confinement in QCD but there is no confinement in QED. We give then a universal relation between the confinement and the dynamical property of QCD and reveals the origin of the colour confinement, which can be demonstrated as the dynamical effect of QCD or more explicitly the dynamical mass generation of the gluon.

    hep-phhep-th2 citations
12. 12*

    The spin of the second-born black hole in coalescing binary black holes

    Y. Qin🇨🇭 · T. Fragos🇩🇰 · G. Meynet🇨🇭 · J. Andrews🇬🇷 · M. Sørensen🇨🇭 · H.F. Song🇨🇳

    Various binary black hole formation channels have been proposed since the first gravitational event GW150914 was discovered by the Advanced Laser Interferometer Gravitational-Wave Observatory (AdLIGO). For all evolutionary channels based on the evolution of isolated binaries, the immediate progenitor of the binary black hole is a close binary system composed of a black hole and a helium star. We perform detailed binary evolution and systematically explore the parameter space of initial binary properties, including initial black hole and helium star masses, initial rotation of the helium star as well as metallicity. We argue that the spin of the first-born black hole at its birth is negligible ($\lesssim 0.1$), hence the second-born black hole's spin dominates the measured effective spin, ${\chi }_{\mathrm{eff}}$, from gravitational wave events of double black hole mergers. We find that tides can be important only when orbital periods are shorter than 2 days. Upon core collapse, the helium star produces a black hole (the second-born black hole in the system) with a spin that can span the entire range from zero to maximally spinning. We show that the bimodal distribution of the spin of the second-born black hole obtained in recent papers is mainly due to oversimplifying assumptions. We find an anti-correlation between the merging timescale of the two black holes, T${}_{\mathrm{merger}}$, and the effective spin ${\chi }_{\mathrm{eff}}$. Finally, we provide new prescriptions for the tidal coefficient E${}_2$ for both H-rich and the helium-rich stars. We predict that, with future improvements to AdLIGO's sensitivity, the sample of merging binary black hole systems will show an overdensity of sources with positive but small ${\chi }_{\mathrm{eff}}$. originating from lower mass black hole mergers born at low redshift.

    ↳ astro-ph.SRhep-phAstron.Astrophys.(2018)·256 citations
13. 13*

    Light isovector resonances in ${\pi }^{-}p\to {\pi }^{-}{\pi }^{-}{\pi }^{+}p$ at 190 GeV/$c$

    M. Aghasyan · M.G. Alexeev · G.D. Alexeev · A. Amoroso · V. Andrieux · N.V. Anfimov · V. Anosov · A. Antoshkin · K. Augsten · W. Augustyniak · A. Austregesilo · C.D.R. Azevedo and 213 other authors

    We have performed the most comprehensive resonance-model fit of ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction ${\pi }^{-}+p\to {\pi }^{-}{\pi }^{-}{\pi }^{+}+p_{\text{recoil}}$ with a 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5<m_{3\pi }<2.5$ GeV/$c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1<t^{\prime }<1.0$ $($GeV$/c{)}^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC}=0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. The model contains the well-known resonances $\pi (1800)$, $a_1(1260)$, $a_2(1320)$, ${\pi }_2(1670)$, ${\pi }_2(1880)$, and $a_4(2040)$. In addition, it includes the disputed ${\pi }_1(1600)$, the excited states $a_1(1640)$, $a_2(1700)$, and ${\pi }_2(2005)$, as well as the resonancelike $a_1(1420)$. We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 $t^{\prime }$ bins. We extract the relative branching fractions of the $\rho (770)\pi$ and $f_2(1270)\pi$ decays of $a_2(1320)$ and $a_4(2040)$, where the former one is measured for the first time. In a novel approach, we extract the $t^{\prime }$ dependence of the intensity of the resonances and of their phases. The $t^{\prime }$ dependence of the intensities of most resonances differs distinctly from the $t^{\prime }$ dependence of the nonresonant components. For the first time, we determine the $t^{\prime }$ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances.

    ↳ hep-exhep-phPRD(2018)·126 citations
14. 14*

    Mode truncations and scattering in strong fields

    Tom Heinzl🇬🇧 · Anton Ilderton🇬🇧 · Daniel Seipt🇬🇧

    Truncating quantum field theories to a dominant mode offers a non-perturbative approach to their solution. We consider here the interaction of charged scalar matter with a single mode of the electromagnetic field. The implied breaking of explicit Lorentz invariance prompts us to compare instant-form quantisation and front-form, with the latter yielding significant simplifications when light-front zero modes are included. Using these field theory results we reassess the validity of existing first-quantised approaches to depletion effects in strong laser fields, and propose an alternative interpretation based on the dressing approach to QED and its infra-red structure.

    ↳ hep-thhep-phPRD(2018)·9 citations
15. 15*

    Infrared limit of quantum gravity

    C. Wetterich🇩🇪

    We explore the infrared limit of quantum gravity in presence of a cosmological constant or effective potential for scalar fields. For a positive effective scalar potential, one-loop perturbation theory around flat space is divergent due to an instability of the graviton propagator. Functional renormalization solves this problem by a flow of couplings avoiding instabilities. This leads to a graviton barrier limiting the maximal growth of the effective potential for large values of scalar fields. In the presence of this barrier, variable gravity with a field dependent Planck mass can solve the cosmological constant problem by a cosmological runaway solution. We discuss the naturalness of tiny values of the cosmological constant and cosmon mass due to a strong attraction towards an infrared fixed point.

    ↳ gr-qchep-phhep-thPRD(2018)·24 citations
16. 16*

    Resummation and renormalons in a general Quantum Field Theory

    Alessio Maiezza🇭🇷 · Juan Carlos Vasquez🇨🇱

    We generalize the concept of Borel resummability and renormalons to a quantum field theory with an arbitrary number of fields and couplings, starting from the known notion based on the running coupling constants. An approach to identify the renormalons is provided by exploiting an analytic solution of the generic one-loop renormalization group equations in multi-field theories. Methods to evaluate the regions in coupling space where the theory is resummable are described. The generalization is then illustrated in a toy model with two coupled scalar fields, representing the simplest extension of the one-field analysis presented in the seminal works of the subject. Furthermore, possible links to realistic theories are briefly discussed.

    ↳ hep-thhep-phAnnals Phys.(2018)·17 citations
17. 17*

    Inflation in a scale invariant universe

    Pedro G. Ferreira🇬🇧 · Christopher T. Hill🇺🇸 · Johannes Noller🇨🇭 · Graham G. Ross🇬🇧

    A scale-invariant universe can have a period of accelerated expansion at early times: inflation. We use a frame-invariant approach to calculate inflationary observables in a scale invariant theory of gravity involving two scalar fields - the spectral indices, the tensor to scalar ratio, the level of isocurvature modes and non-Gaussianity. We show that scale symmetry leads to an exact cancellation of isocurvature modes and that, in the scale-symmetry broken phase, this theory is well described by a single scalar field theory. We find the predictions of this theory strongly compatible with current observations.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2018)·80 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.