Wed·Feb 17, 2016Wednesday·February 17, 2016

1. 01*

   The $\text{Fermi}$-LAT gamma-ray excess at the Galactic Center in the singlet-doublet fermion dark matter model

   Shunsaku Horiuchi🇺🇸 · Oscar Macias🇺🇸 · Diego Restrepo🇨🇴 · Andres Rivera🇨🇴 · Hamish Silverwood🇳🇱 · Oscar Zapata🇨🇴

   The singlet-doublet fermion dark matter model (SDFDM) provides a good DM candidate as well as the possibility of generating neutrino masses radiatively. The search and identification of DM requires the combined effort of both indirect and direct DM detection experiments in addition to the LHC. Remarkably, an excess of GeV gamma rays from the Galactic Center (GCE) has been measured with the \textit{Fermi} Large Area Telescope (LAT) which appears to be robust with respect to changes in the diffuse galactic background modeling. Although several astrophysical explanations have been proposed, DM remains a simple and well motivated alternative. In this work, we examine the sensitivities of dark matter searches in the SDFDM scenario using $\text{Fermi}$-LAT, CTA, IceCube/DeepCore, LUX, PICO and LHC with an emphasis on exploring the regions of the parameter space that can account for the GCE. We find that DM particles present in this model with masses close to $\sim 99$ GeV and $\sim (173-190)$ GeV annihilating predominantly into the $W^{+}{W}^{-}$ channel and $t\bar{t}$ channel respectively, provide an acceptable fit to the GCE while being consistent with different current experimental bounds. We also find that much of the obtained parameter space can be ruled out by future direct search experiments like LZ and XENON-1T, in case of null results by these detectors. Interestingly, we show that the most recent data by LUX is starting to probe the best fit region in the SDFDM model.

   hep-phastro-ph.HEJCAP(2016)·43 citations
2. 02*

   Color-superconductivity and inhomogeneous chiral symmetry breaking in isospin-asymmetric quark matter

   Daniel Nowakowski🇩🇪 · Stefano Carignano🇮🇹

   We investigate the effects of isospin asymmetry on the competition between color-superconductivity and inhomogeneous chiral symmetry breaking in dense two-flavor quark matter using an extended Nambu--Jona-Lasinio model. We confirm the appearance of a coexistence window where chiral symmetry is inhomogeneously broken and a nonzero spatially homogeneous diquark gap is present, consistently with previous works, and show that such a phase survives at nonzero isospin chemical potentials. We also discuss how the model phase structure becomes modified as large isospin asymmetries are considered.

   hep-phPoS(2016)·8 citations
3. 03*

   Precision Drell-Yan Measurements at the LHC and Implications for the Diphoton Excess

   Florian Goertz🇨🇭 · Andrey Katz🇨🇭 · Minho Son🇰🇷 · Alfredo Urbano🇨🇭

   Precision measurements of the Drell-Yan (DY) cross section at the LHC constrain new physics scenarios that involve new states with electroweak (EW) charges. We analyze these constraints and apply them to models that can address the LHC diphoton excess at 750 GeV. We confront these findings with LEP EW precision tests and show that DY provides stronger constraints than the LEP data. While 8 TeV data can already probe some parts of the interesting region of parameter space, LHC14 results are expected to cover a substantial part of the relevant terrain. We derive the bounds from the existing data, estimate LHC14 reach and compare them to the bounds one gets from LEP and future FCC-ee precision measurements.

   hep-phhep-exJHEP(2016)·24 citations
4. 04*

   Naturalizing Supersymmetry with a Two-Field Relaxion Mechanism

   Jason L. Evans🇰🇷 · Tony Gherghetta🇺🇸 · Natsumi Nagata🇺🇸 · Zoe Thomas🇺🇸

   We present a supersymmetric version of a two-field relaxion model that naturalizes tuned versions of supersymmetry. This arises from a relaxion mechanism that does not depend on QCD dynamics and where the relaxion potential barrier height is controlled by a second axion-like field. During the cosmological evolution, the relaxion rolls with a nonzero value that breaks supersymmetry and scans the soft supersymmetric mass terms. Electroweak symmetry is broken after the soft masses become of order the supersymmetric Higgs mass term and causes the relaxion to stop rolling for superpartner masses up to $\sim 10^9$ GeV. This can explain the tuning in supersymmetric models, including split-SUSY models, while preserving the QCD axion solution to the strong CP problem. Besides predicting two very weakly-coupled axion-like particles, the supersymmetric spectrum may contain an extra Goldstino, which could be a viable dark matter candidate.

   hep-phhep-thJHEP(2016)·54 citations
5. 05*

   A White Paper on keV Sterile Neutrino Dark Matter

   R. Adhikari🇮🇳 · M. Agostini🇮🇹 · N. Anh Ky🇻🇳 · T. Araki🇯🇵 · M. Archidiacono🇩🇰 · M. Bahr🇺🇸 · J. Baur🇫🇷 · J. Behrens🇩🇪 · F. Bezrukov🇺🇸 · P.S. Bhupal Dev🇬🇧 · D. Borah🇮🇳 · A. Boyarsky🇳🇱 and 124 other authors

   We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved - cosmology, astrophysics, nuclear, and particle physics - in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.

   hep-phastro-ph.COastro-ph.GAhep-exJCAP(2017)·728 citations
6. 06*

   Axion String Dynamics I: 2+1D

   Leesa M. Fleury🇨🇦 · Guy D. Moore🇩🇪

   If the axion exists and if the initial axion field value is uncorrelated at causally disconnected points, then it should be possible to predict the efficiency of cosmological axion production, relating the axionic dark matter density to the axion mass. The main obstacle to making this prediction is correctly treating the axion string cores. We develop a new algorithm for treating the axionic string cores correctly in 2+1 dimensions. When the axionic string cores are given their full physical string tension, axion production is about twice as efficient as in previous simulations. We argue that the string network in 2+1 dimensions should behave very differently than in 3+1 dimensions, so this result cannot be simply carried over to the physical case. We outline how to extend our method to 3+1D axion string dynamics.

   hep-phJCAP(2016)·43 citations
7. 07*

   Baryon number violation in supersymmetry: Neutron-antineutron oscillations as a probe beyond the LHC

   Lorenzo Calibbi🇨🇳 · Gabriele Ferretti🇸🇪 · David Milstead🇸🇪 · Christoffer Petersson🇧🇪 · Ruth Pöttgen🇸🇪

   We summarize the current status of baryon number violation in supersymmetry and provide prospects for going beyond the present reach by means of a new search for neutron-antineutron oscillations. The main motivation is the recently proposed neutron-antineutron oscillation experiment at the European Spallation Source in Lund, Sweden, which is projected to be able to improve the current bound on the transition probability in the quasi-free regime by three orders of magnitude. We consider various processes involving superpartners that give rise to neutron-antineutron oscillations and extract the corresponding simplified models, including only the most relevant superpartners and couplings. In terms of these models we recast and determine the exclusion limits from LHC searches as well as from searches for flavor transitions, CP violation and di-nucleon decays. We find that, for certain regions of the parameter space, the proposed neutron-antineutron experiment has a reach that goes beyond all other experiments, as it can probe gluino and squark masses in the multi-TeV range.

   hep-phhep-exJHEP(2016)·30 citations
8. 08*

   Constraining New Physics Models with Isotope Shift Spectroscopy

   Claudia Frugiuele🇮🇱 · Elina Fuchs🇮🇱 · Gilad Perez🇮🇱 · Matthias Schlaffer🇮🇱

   Isotope shifts of transition frequencies in atoms constrain generic long- and intermediate-range interactions. We focus on new physics scenarios that can be most strongly constrained by King Linearity Violation such as models with B-L vector bosons, Higgs portal and chameleon. With the anticipated precision, King Linearity Violation has the potential to set the strongest laboratory bounds on these models in some regions of parameter space. Furthermore, we show that this method can probe the couplings relevant for the protophobic interpretation of the recently reported Be anomaly. We extend the formalism to include an arbitrary number of transitions and isotope pairs and fit the new physics coupling to the currently available isotope shift measurements.

   hep-phphysics.atom-phPRD(2017)·109 citations
9. 09*

   Probing New Physics with Isotope Shift Spectroscopy

   Cédric Delaunay🇫🇷 · Yotam Soreq🇺🇸

   We investigate the potential to probe physics beyond the Standard Model with isotope shift measurements of optical atomic clock transitions. We first derive the reach for generic new physics above the GeV scale at the effective field theory level, as well as estimate the limits on possible new spin-independent forces mediated by sub-GeV states coupled to electrons and neutrons. We also study the weak force and show that isotope shifts could provide strong constraints on the $Z^0$ couplings to valence quarks, which complement precision observables at LEP and atomic parity violation experiments. Finally, motivated by recent experimental hints of a new 750 GeV resonance in diphotons, we also consider the potential to probe its parity-preserving couplings to electrons, quarks and gluons with this method. In particular, combining the diphoton signal with indirect constraints from $g_e-2$ and isotope shifts in Ytterbium allows to probe the resonance coupling to electrons with unprecedented precision.

   hep-phphysics.atom-phquant-ph23 citations
10. 10*

    Reheating the Universe at Criticality

    Hyun Min Lee🇰🇷

    We present the general discussion on the inflection point inflation with small or large inflaton fields and show the effects of reheating dynamics on the inflationary predictions. In order to compare the model predictions with precisely measured CMB anisotropies and constrain the inflation models, the knowledge of the reheating dynamics is required. Inflection point inflation extended to the trans-Planckian regime can accommodate a sizable tensor-to-scalar ratio at the detectable level in the future CMB experiments.

    hep-phastro-ph.COInt.J.Mod.Phys.Conf.Ser.(2016)·0 citations
11. 11*

    Long Range Azimuthal Correlations of Multiple Gluons in Gluon Saturation Limit

    Sener Ozonder🇺🇸

    We calculate the inclusive gluon correlation function for arbitrary number of gluons with full rapidity and transverse momentum dependence for the initial glasma state of the p-p, p-A and A-A collisions. The formula we derive via superdiagrams generates cumulants for any number of gluons. Higher order cumulants contain information on correlations between multiple gluons, and they are necessary for calculations of higher dimensional ridges as well as flow coefficients from multi-particle correlations.

    hep-phhep-thnucl-thPRD(2016)·6 citations
12. 12*

    The Spectroscopy and Form Factors of Nucleon Resonances from Superconformal Quantum Mechanics and Holographic QCD

    Guy F. de Teramond🇨🇷

    The superconformal algebraic approach to hadronic physics is used to construct a semiclassical effective theory for nucleons which incorporates essential nonperturbative dynamical features, such as the emergence of a confining scale and the Regge resonance spectrum. Relativistic bound-state equations for nucleons follow from the extension of superconformal quantum mechanics to the light front and its holographic embedding in a higher dimensional gravity theory. Superconformal algebra has been used elsewhere to describe the connections between the light mesons and baryons, but in the present context it relates the fermion positive and negative chirality states and uniquely determines the confinement potential of nucleons. The holographic mapping of multi-quark bound states also leads to a light-front cluster decomposition of form factors for an arbitrary number of constituents. The remarkable analytical structure which follows incorporates the correct scaling behavior at high photon virtualities and also vector dominance at low energies.

    hep-phFew Body Syst.(2016)·6 citations
13. 13*

    The decays $\tau \to (\eta ,{\eta }^{\prime })K^{-}{\nu }_{\tau }$ in the extended Nambu-Jona-Lasinio model

    M.K. Volkov🇷🇺 · A.A. Pivovarov🇷🇺

    The decays $\tau \to (\eta ,{\eta }^{\prime })K^{-}{\nu }_{\tau }$ are described in the framework of the extended Nambu-Jona-Lasinio model. Both full and differential widths of these decays are calculated. The vector and scalar channels are considered. In the vector channels, the subprocesses with intermediate $K^{\ast }(892)$ and $K^{\ast }(1410)$ mesons play the main role. In the scalar channels, the subprocesses with intermediate $K_0^{\ast }(800)$ and $K_0^{\ast }(1430)$ mesons are taken into account. Scalar channels play a less important role in calculation of the full width of the decay $\tau \to (\eta ,{\eta }^{\prime })K^{-}{\nu }_{\tau }$. The obtained results are in satisfactory agreement with the experimental data.

    hep-phJETP Lett.(2016)·10 citations
14. 14*

    Effects of a dressed quark-gluon vertex in vector heavy-light mesons and theory average of B(c)* meson mass

    M. Gomez-Rocha🇮🇹 · T. Hilger🇦🇹 · A. Krassnigg🇦🇹

    We extend earlier investigations of heavy-light pseudoscalar mesons to the vector case, using a simple model in the context of the Dyson-Schwinger-Bethe-Salpeter approach. We investigate the effects of a dressed-quark-gluon vertex in a systematic fashion and illustrate and attempt to quantify corrections beyond the phenomenologically very useful and successful rainbow-ladder truncation. In particular we investigate dressed quark photon vertex in such a setup and make a prediction for the experimentally as yet unknown mass of the B_c*, which we obtain at 6.334 GeV well in line with predictions from other approaches. Furthermore, we combine a comprehensive set of results from the theory literature. The theory average for the mass of the B_c* meson is 6.336 +- 0.002 GeV.

    hep-phhep-exPRD(2016)·45 citations
15. 15*

    Pomeron Interactions from the Einstein-Hilbert Action

    Ioannis Iatrakis🇺🇸 · Adith Ramamurti🇺🇸 · Edward Shuryak🇺🇸

    Holographic models of QCD, collectively known as AdS/QCD, have been proven useful in deriving several properties of hadrons. One particular feature well reproduced by such models is the Regge trajectories, both for mesons and glueballs. We focus on scalar and tensor glueballs, and derive an effective theory for the Pomeron by analytic continuation along the leading trajectory from the tensor glueball. It then follows that the Pomeron, as the tensor glueball itself, should possess a two-index polarization tensor, inherited from the graviton. The three-graviton interaction is deduced from the Einstein-Hilbert action. Using this structure in the cross section of double-Pomeron production of the tensor glueball, we calculate certain angular distributions of production and compare them with those from the CERN WA102 experiment. We find that the agreement is very good for the $f_2(2300)$ tensor glueball candidate. At the same time, other tensor states -- such as $f_2(1270)$ and $f_2^{\prime }(1520)$ -- have completely different distributions, which we interpret as consequence of the fact that they are not glueballs and thus, in our model, unrelated to the gravitational excitations, which are dual to spin-2 glueballs.

    hep-phhep-thPRD(2016)·23 citations
16. 16*

    Dibaryons with two strange quarks and total spin zero in a constituent quark model

    Woosung Park🇰🇷 · Aaron Park🇰🇷 · Su Houng Lee🇰🇷

    We investigate the symmetry property and construct the wave function of the dibaryon states containing two strange quarks with S=0 in both the flavor SU(3) symmetric and breaking cases. We discuss how the color $\otimes$ isospin $\otimes$ spin states of dibaryon in the symmetry broking case of flavor SU(3) can be extracted from the fully antisymmetric states in flavor SU(3). The stability of the dibaryon against the strong decay into two baryons are then discussed, by using the variational method within a constituent quark model with a confining and color-spin interactions. To compare our results with that from lattice QCD in flavor SU(3) limit, we search for the stable H-dibaryon in a wide range of $\pi$ meson mass. We find that with the given potential, there is no compact six quark dibaryon state in the SU(3) flavor symmetry broken case with realistic quark masses as well as in flavor SU(3) symmetric case in a wide range of quark masses.

    hep-phnucl-thPRD(2016)·25 citations
17. 17*

    A Relativistic Model for the Electromagnetic Structure of Baryons from the 3rd Resonance Region

    G. Ramalho🇧🇷

    We present some predictions for the ${\gamma }^{\ast }N\to N^{\ast }$ transition amplitudes, where $N$ is the nucleon, and $N^{\ast }$ is a nucleon excitation from the third resonance region. First we estimate the transition amplitudes associated with the second radial excitation of the nucleon, interpreted as the $N(1710)$ state, using the covariant spectator quark model. After that, we combine some results from the covariant spectator quark model with the framework of the single quark transition model, to make predictions for the ${\gamma }^{\ast }N\to N^{\ast }$ transition amplitudes, where $N^{\ast }$ is a member of the $SU(6)$-multiplet $[70,1^{-}]$. The results for the ${\gamma }^{\ast }N\to N(1520)$ and ${\gamma }^{\ast }N\to N(1535)$ transition amplitudes are used as input to the calculation of the amplitudes $A_{1/2}$, $A_{3/2}$, associated with the ${\gamma }^{\ast }N\to N(1650)$, ${\gamma }^{\ast }N\to N(1700)$, ${\gamma }^{\ast }N\to \Delta (1620)$, and ${\gamma }^{\ast }N\to \Delta (1700)$ transitions. Our estimates are compared with the available data. In order to facilitate the comparison with future experimental data at high $Q^2$, we derived also simple parametrizations for the amplitudes, compatible with the expected falloff at high $Q^2$.

    hep-phhep-exnucl-exnucl-thFew Body Syst.(2016)·1 citation
18. 18*

    ATLAS on-Z Excess Through Vector-Like Quarks

    Motoi Endo🇯🇵 · Yoshitaro Takaesu🇯🇵

    We investigate the possibility that the excess observed in the leptonic-$Z+$jets $+\text{slashed}{E}_T$ ATLAS SUSY search is due to pair productions of a vector-like quark $U$ decaying to the first-generation quarks and $Z$ boson. We find that the excess can be explained within the 2$\sigma$ (up to 1.4$\sigma$) level while evading the constraints from the other LHC searches. The preferred range of the mass and branching ratio are $610<m_U<760$ GeV and $\mathrm{Br}(U\to Zq)>0.3$-$0.45$, respectively.

    hep-phPLB(2016)·8 citations
19. 19*

    The different energy loss mechanisms of inclusive and b-tagged reconstructed jets within ultra-relativistic heavy-ion collisions

    Florian Senzel🇩🇪 · Jan Uphoff🇩🇪 · Zhe Xu🇨🇳 · Carsten Greiner🇩🇪

    The phenomenon of jet quenching provides essential information about the properties of hot and dense matter created in ultra-relativistic heavy-ion collisions. Recent results from experiments at the Large Hadron Collider (LHC) show evidence for an unexpectedly similar suppression of both light and heavy flavor jets. Furthermore, the role of radiative energy loss of heavy quarks is still under active discussion within the theoretical community. By employing the parton cascade Boltzmann Approach to Multi-Parton Scatterings (BAMPS), which numerically solves the 3+1D Boltzmann equation both for light and heavy flavor partons, we calculate the nuclear modification factor of inclusive and b-tagged reconstructed jets in 0-10% central $\sqrt{s_{\mathrm{LHC}}}$ = 2.76 ATeV Pb+Pb collisions. Based on perturbative QCD cross sections we find a suppression of both light and heavy flavor jets. While the inclusive jets are slightly too strong suppressed within BAMPS in comparison with data, both elastic+radiative and only elastic interactions lead to a realistic b-tagged jet suppression. To further investigate light and heavy flavor energy loss we predict the R dependence of inclusive and b-tagged jet suppression. Furthermore, we propose the medium modification of b-tagged jet shapes as an observable for discriminating between different heavy quark energy loss scenarios.

    hep-phnucl-thPLB(2017)·12 citations
20. 20*

    An $a_0$ resonance in strongly coupled $\pi \eta$, $K\overline{K}$ scattering from lattice QCD

    Jozef J. Dudek🇺🇸 · Robert G. Edwards🇺🇸 · David J. Wilson🇬🇧

    We present the first calculation of coupled-channel meson-meson scattering in the isospin $=1$, $G$-parity negative sector, with channels $\pi \eta$, $K\overline{K}$ and $\pi {\eta }^{\prime }$, in a first-principles approach to QCD. From the discrete spectrum of eigenstates in three volumes extracted from lattice QCD correlation functions we determine the energy dependence of the $S$-matrix, and find that the $S$-wave features a prominent cusp-like structure in $\pi \eta \to \pi \eta$ close to $K\overline{K}$ threshold coupled with a rapid turn on of amplitudes leading to the $K\overline{K}$ final-state. This behavior is traced to an $a_0(980)$-like resonance, strongly coupled to both $\pi \eta$ and $K\overline{K}$, which is identified with a pole in the complex energy plane, appearing on only a single unphysical Riemann sheet. Consideration of $D$-wave scattering suggests a narrow tensor resonance at higher energy.

    hep-phhep-latPRD(2016)·203 citations
21. 21*

    Lepton flavor violation and scalar dark matter in a radiative model of neutrino masses

    Michael Klasen · David R. Lamprea · Carlos E. Yaguna

    We consider a simple extension of the Standard Model that can account for the dark matter and explain the existence of neutrino masses. The model includes a vector-like doublet of SU(2), a singlet fermion, and two scalar singlets, all of them odd under a new Z${}_2$ symmetry. Neutrino masses are generated radiatively by one-loop processes involving the new fields, while the dark matter candidate is the lightest neutral particle among them. We focus specifically on the case where the dark matter particle is one of the scalars and its relic density is determined by its Yukawa interactions. The phenomenology of this setup, including neutrino masses, dark matter and lepton flavor violation, is analyzed in some detail. We find that the dark matter mass must be below $500$ GeV to satisfy the relic density constraint. Lepton flavor violating processes are shown to provide the most promising way to test this scenario. Future $\mu \to 3e$ and $\mu$-$e$ conversion experiments, in particular, have the potential to probe the entire viable parameter space of this model.

    hep-phEPJC(2018)·24 citations
22. 22*

    Testing local Lorentz invariance with gravitational waves

    Alan Kostelecky🇺🇸 · Matthew Mewes🇺🇸

    The effects of local Lorentz violation on dispersion and birefringence of gravitational waves are investigated. The covariant dispersion relation for gravitational waves involving gauge-invariant Lorentz-violating operators of arbitrary mass dimension is constructed. The chirp signal from the gravitational-wave event GW150914 is used to place numerous first constraints on gravitational Lorentz violation.

    ↳ gr-qcastro-ph.HEhep-phPLB(2016)·257 citations
23. 23*

    Natural Inflation with Hidden Scale Invariance

    Neil D. Barrie🇦🇺 · Archil Kobakhidze🇦🇺 · Shelley Liang🇦🇺

    We propose a new class of natural inflation models based on a hidden scale invariance. In a very generic Wilsonian effective field theory with an arbitrary number of scalar fields, which exhibits scale invariance via the dilaton, the potential necessarily contains a flat direction in the classical limit. This flat direction is lifted by small quantum corrections and inflation is realised without need for an unnatural fine-tuning. In the conformal limit, the effective potential becomes linear in the inflaton field, yielding to specific predictions for the spectral index and the tensor-to-scalar ratio, being respectively: $n_s-1\approx -0.025{\left(\frac{N_{\star }}{60}\right)}^{-1}$ and $r\approx 0.0667{\left(\frac{N_{\star }}{60}\right)}^{-1}$, where $N_{\star }\approx 30-65$ is a number of efolds during observable inflation. This predictions are in reasonable agreement with cosmological measurements. Further improvement of the accuracy of these measurements may turn out to be critical in falsifying our scenario.

    ↳ gr-qchep-phhep-thPLB(2016)·49 citations
24. 24*

    Bjorken flow in one-dimensional relativistic magnetohydrodynamics with magnetization

    Shi Pu🇩🇪 · Victor Roy🇩🇪 · Luciano Rezzolla🇩🇪 · Dirk H. Rischke🇩🇪

    We study the one-dimensional, longitudinally boost-invariant motion of an ideal fluid with infinite conductivity in the presence of a transverse magnetic field, i.e., in the ideal transverse magnetohydrodynamical limit. In an extension of our previous work Roy et al., [Phys. Lett. B 750, 45 (2015)], we consider the fluid to have a non-zero magnetization. First, we assume a constant magnetic susceptibility ${\chi }_m$ and consider an ultrarelativistic ideal gas equation of state. For a paramagnetic fluid (i.e., with ${\chi }_m>0$), the decay of the energy density slows down since the fluid gains energy from the magnetic field. For a diamagnetic fluid (i.e., with ${\chi }_m<0$), the energy density decays faster because it feeds energy into the magnetic field. Furthermore, when the magnetic field is taken to be external and to decay in proper time $\tau$ with a power law $\sim {\tau }^{-a}$, two distinct solutions can be found depending on the values of $a$ and ${\chi }_m$. Finally, we also solve the ideal magnetohydrodynamical equations for one-dimensional Bjorken flow with a temperature-dependent magnetic susceptibility and a realistic equation of state given by lattice-QCD data. We find that the temperature and energy density decay more slowly because of the non-vanishing magnetization. For values of the magnetic field typical for heavy-ion collisions, this effect is, however, rather small. Only for magnetic fields which are about an order of magnitude larger than expected for heavy-ion collisions, the system is substantially reheated and the lifetime of the quark phase might be extended.

    ↳ nucl-thastro-ph.HEgr-qchep-phPRD(2016)·115 citations
25. 25*

    Transverse flow induced by inhomogeneous magnetic fields in the Bjorken expansion

    Shi Pu🇩🇪 · Di-Lun Yang🇯🇵

    We investigate the magnetohydrodynamics in the presence of an external magnetic field following the power-law decay in proper time and having spatial inhomogeneity characterized by a Gaussian distribution in one of transverse coordinates under the Bjorken expansion. The leading-order solution is obtained in the weak-field approximation, where both energy density and fluid velocity are modified. It is found that the spatial gradient of the magnetic field results in transverse flow, where the flow direction depends on the decay exponents of the magnetic field. We suggest that such a magnetic-field-induced effect might influence anisotropic flow in heavy ion collisions.

    ↳ nucl-thhep-phPRD(2016)·55 citations
26. 26*

    Physics at the FCC-ee

    David d'Enterria🇨🇭

    The physics program accessible in $e^{+}{e}^{-}$ collisions at the Future Circular Collider (FCC-ee) is summarized. The FCC-ee aims at collecting multi-ab${}^{-1}$ integrated luminosities in $e^{+}{e}^{-}$ at $\sqrt{s}$ = 90, 160, 240, and 350 GeV, yielding 10${}^{12}$ Z bosons, 10${}^8$ W${}^{+}$W${}^{-}$ pairs, 10${}^6$ Higgs bosons and $4\cdot 10^5$ top-quark pairs per year. Such huge data samples combined with a $\mathcal{O}(100\mathrm{keV})$ c.m. energy uncertainty will allow for Standard Model measurements with unparalleled precision and searches for new physics in regions not probed so far. The FCC-ee will be able to (i) indirectly discover new particles coupling to the Higgs and electroweak bosons up to scales $\Lambda \approx$ 7 and 100 TeV; (ii) perform competitive SUSY tests at the loop level in regions beyond the LHC reach; and (iii) achieve the best potential in direct collider searches for dark matter and sterile neutrinos with masses below 60 GeV.

    ↳ hep-exhep-ph112 citations
27. 27*

    Collinearity constraints for on-shell massless particle three-point functions, and implications for allowed-forbidden $n+1$-point functions

    Stephen L. Adler🇺🇸

    A simple collinearity argument implies that the massless particle three-point function of helicities $h_1,h_2,h_3$ with corresponding real-valued four-momenta $k_1,k_2,k_3$ taken as all incoming or all outgoing (i.e., $k_1+k_2+k_3=0$), vanishes by helicity conservation unless $h_1+h_2+h_3=0$. When any one particle with four-momentum $k$ is off mass shell, this constraint no longer applies; a forbidden amplitude with $h_1+h_2+h_3\ne 0$ on-shell can be nonzero off-shell, but vanishes proportionally to $k^2$ as $k$ approaches mass shell. When an on-shell forbidden amplitude is coupled to an allowed $n$-point amplitude to form an $n+1$ point function, this $k^2$ factor in the forbidden amplitude cancels the $k^2$ in the propagator, leading to a $n+1$-point function that has no pole at $k^2=0$. We relate our results for real-valued four-momenta to the corresponding selection rules that have been derived in the on-shell literature for complexified four-momenta.

    ↳ hep-thhep-phPRD(2016)·4 citations
28. 28*

    Quantum calculation of the Vavilov-Cherenkov radiation by twisted electrons

    I. P. Ivanov🇵🇹 · V. G. Serbo🇷🇺 · V. A. Zaytsev🇷🇺

    We present the detailed quantum electrodynamical description of Vavilov-Cherenkov radiation emitted by a relativistic twisted electron in the transparent medium. Simple expressions for the spectral and spectral-angular distributions as well as for the polarization properties of the emitted radiation are obtained. Unlike the plane-wave case, the twisted electron produces radiation within the annular angular region, with enhancement towards its boundaries. Additionally, the emitted photons can have linear polarization not only in the scattering plane but also in the orthogonal direction. We find that the Vavilov-Cherenkov radiation emitted by an electron in a superposition of two vortex states exhibits a strong azimuthal asymmetry. Thus, the Vavilov-Cherenkov radiation offers itself as a convenient diagnostic tool of such electrons and complements the traditional microscopic imaging.

    ↳ quant-phhep-phphysics.opticsPRA(2016)·42 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.