Tue·May 8, 2018Tuesday·May 8, 2018

1. 01*

   Dark Matter in Anomaly-Free Gauge Extensions

   Martin Bauer🇩🇪 · Sascha Diefenbacher🇩🇪 · Tilman Plehn🇩🇪 · Michael Russell🇩🇪 · Daniel A. Camargo🇧🇷

   A consistent model for vector mediators to dark matter needs to be anomaly-free and include a scalar mode from mass generation. For the leading U(1) extensions we review the structure and constraints, including kinetic mixing at loop level. The thermal relic density suggests that the vector and scalar masses are similar. For the LHC we combine a $Z^{\prime }$ shape analysis with mono-jets. For the latter, we find that a shape analysis offers significant improvement over existing cut-and-count approaches. Direct detection limits strongly constrain the kinetic mixing angle and we propose a ${\ell }^{+}{\ell }^{-}{E}_T$ search strategy based on the scalar mediator.

   hep-phSciPost Phys.(2018)·44 citations
2. 02*

   The Muon $(g-2)$ Spin Equations, the Magic $\gamma$, What's small and what's not

   James P. Miller🇺🇸 · B. Lee Roberts🇺🇸

   We review the spin equations for the muon in the 1.45~T muon storage ring at Brookhaven National Laboratory, which has subsequently been relocated to Fermilab. Muons are stored in a uniform 1.45~T magnetic field, and vertical focusing is provided by four sets of electrostatic quadrupoles placed symmetrically around the storage ring. The storage ring is operated at the "magic $\gamma =29.3$" so that the effect of the motional magnetic field cancels for muons at the magic momentum. We point out the relative sizes of the various terms in the spin equations, and show that for experiments that use the magic $\gamma$ and electric quadrupole focusing to store the muon beam, any proposed effect that multiplies either the motional magnetic field $\vec{\beta }\times \vec{E}$ or the muon pitching motion $\vec{\beta }\cdot \vec{B}$ term, will be smaller by three or more orders of magnitude, relative to the spin precession from the storage ring magnetic field. We use a recently proposed General Relativity correction as an example, to demonstrate the smallness of any such contribution, and point out that the revised preprint from these authors still contains a conceptual error, that significantly overestimates the magnitude of their proposed correction. We have prepared this document in the hope that future authors will find it useful, should they wish to propose corrections from some additional term added to the Thomas equation, Eq. 13, below. Our goal is to clarify how the experiment is done, and how the small corrections due to the presence of the radial electric field and the vertical pitching motion of themuons (betatron motion) in the storage ring are taken into account.

   hep-phhep-ex6 citations
3. 03*

   Light (and darkness) from a light hidden Higgs

   Roberto Vega🇺🇸 · Roberto Vega-Morales🇪🇸 · Keping Xie🇺🇸

   We examine light diphoton signals from extended Higgs sectors possessing (approximate) fermiophobia with Standard Model (SM) fermions as well as custodial symmetry. This class of Higgs sectors can be realized in various beyond the SM scenarios and is able to evade many experimental limits, even at light masses, which are otherwise strongly constraining. Below the $WW$ threshold, the most robust probes of the neutral component are di and multi-photon searches. Utilizing the dominant Drell-Yan Higgs pair production mechanism and combining it with updated LHC diphoton data, we derive robust upper bounds on the allowed branching ratio for masses between $45-160$ GeV. Furthermore, masses $\lesssim 110$ GeV are ruled out if the coupling to photons is dominated by $W$ boson loops. We then examine two simple ways to evade these bounds via cancellations between different loop contributions or by introducing decays into an invisible sector. This also opens up the possibility of future LHC diphoton signals from a light hidden Higgs sector. As explicit realizations, we consider the Georgi-Machacek (GM) and Supersymmetric GM (SGM) models which contain custodial (degenerate) Higgs bosons with suppressed couplings to SM fermions and, in the SGM model, a (neutralino) LSP. We also breifly examine the recent $\sim 3\sigma$ CMS diphoton excess at $\sim 95$ GeV.

   hep-phhep-exJHEP(2018)·19 citations
4. 04*

   Pseudo-Dirac neutrinos from flavour dependent CP symmetry

   Anjan S. Joshipura🇮🇳 · Ketan M. Patel🇮🇳

   Discrete residual symmetries and flavour dependent CP symmetries consistent with them have been used to constrain neutrino mixing angles and CP violating phases. We discuss here role of such CP symmetries in obtaining a pseudo-Dirac neutrino which can provide a pair of neutrinos responsible for the solar splitting. It is shown that if (a) $3\times 3$ Majorana neutrino matrix $M_{\nu }$ is invariant under a discrete $Z_2\times Z_2$ symmetry generated by $S_{1,2}$, (b) CP symmetry $X$ transform $M_{\nu }$ as $X^T{M}_{\nu }X=M_{\nu }^{\ast }$, and (c) $X$ and $S_{1,2}$ obey consistency conditions $X{S}_{1,2}^{\ast }{X}^{†}=S_{2,1}$, then two of the neutrino masses are degenerate independent of specific forms of $X$, $S_1$ and $S_2$. Explicit examples of this result are discussed in the context of $\Delta (6n^2)$ groups which can also be used to constrain neutrino mixing matrix $U$. Degeneracy in two of the masses does not allow complete determination of $U$ but it can also be fixed once the perturbations are introduced. We consider explicit perturbations which break $Z_2\times Z_2$ symmetries but respect CP. These are shown to remove the degeneracy and provide a predictive description of neutrino spectrum. In particular, a correlation $\sin 2{\theta }_{23}\sin {\delta }_{CP}=\pm \mathrm{Im}[p]$ is obtained between the atmospheric mixing angle ${\theta }_{23}$ and the CP violating phase ${\delta }_{CP}$ in terms of a group theoretically determined phase factor $p$. Experimentally interesting case ${\theta }_{23}=\frac{\pi }{4}$, ${\delta }_{CP}=\pm \frac{\pi }{2}$ emerges for groups which predict purely imaginary $p$. We present detailed predictions of the allowed ranges of neutrino mixing angles, phases and the lightest neutrino mass for three of the lowest $\Delta (6n^2)$ groups with $n=2,4,6$.

   hep-phJHEP(2018)·5 citations
5. 05*

   Application of the light-front holographic wavefunction for heavy-light pseudoscalar meson in $B_{d,s}\to D_{d,s}P$ decays

   Qin Chang🇨🇳 · Shuai Xu🇨🇳 · Lingxin Chen🇨🇳

   In this paper we extend our analyses of the decay constant and distribution amplitude with an improved holographic wavefunction to the heavy-light pseudoscalar mesons. In the evaluations, the helicity-dependence of the holographic wavefunction is considered; and an independent mass scale parameter is employed to moderate the strong suppression induced by the heavy quark. Under the constraints from decay constants and masses of pseudoscalar mesons, the ${\chi }^2$-analyses for the holographic parameters exhibit a rough consistence with the results obtained by fitting the Regge trajectory. With the fitted parameters, the results for the decay constants and distribution amplitudes are presented. We then show their application in evaluating the $B_{d,s}\to D_{d,s}P$ decays, in which the power-suppressed spectator scattering and weak annihilation corrections are first estimated. Numerically, the spectator scattering and weak annihilation corrections present a negative shift of about $0.7\%$ on the branching fractions; while, the predictions are still larger than the experimental data. Such small negative shift confirms the estimation based on the power counting rules.

   hep-phhep-exNPB(2017)·12 citations
6. 06*

   Black Hole Spin Constraints on the Mass Spectrum and Number of Axion-like Fields

   Matthew J. Stott🇬🇧 · David J. E. Marsh🇩🇪

   Astrophysical observations of spinning BHs, which span $5M_{\odot }\lesssim M_{\mathrm{BH}}\lesssim 5\times 10^8{M}_{\odot }$, can be used to exclude the existence of certain massive bosons via the superradiance phenomenon. In this work, we explore for the first time how these measurements can be used to constrain properties of statistical distributions for the masses of multiple bosonic fields. Quite generally, our methodology excludes $N_{\mathrm{ax}}\gtrsim 30$ scalar fields with a range of mass distribution widths and central values spanning many orders of magnitude. We demonstrate this for the specific example of axions in string theory and M-theory, where the mass distributions in certain cases take universal forms. We place upper bounds on $N_{\mathrm{ax}}$ for certain scenarios of interest realised approximately as mass distributions in M-theory, including the QCD axion, grand unified theories, and fuzzy dark matter.

   hep-phastro-ph.HEgr-qchep-thPRD(2018)·154 citations
7. 07*

   $Z^{\prime }$ Portal Dark Matter in $B-L$ Scotogenic Dirac Model

   Zhi-Long Han🇨🇳 · Weijian Wang🇨🇳

   In this paper, we perform a detail analysis on the phenomenology of $Z^{\prime }$ portal scalar and Dirac fermion dark matter in $B-L$ scotogenic Dirac model. Unconventional $B-L$ charge $Q$ is assigned to the right-handed neutrino ${\nu }_R$ in order to realise scotogenic Dirac neutrino mass at one-loop level, where three typical value $Q=-\frac{1}{4},-4,\frac{3}{2}$ are chosen to illustrate. Observational properties involving dilepton signature at LHC, relativistic degrees of freedom $N_{\text{eff}}$, dark matter relic density, direct and indirect detections are comprehensively studied. Combined results of these observables for the benchmark scenarios imply that the resonance region $M_{\text{DM}}\sim M_{Z^{\prime }}/2$ is the viable parameter space. Focusing on the resonance region, a scanning for TeV-scale dark matter is also performed to obtain current allowed and future prospective parameter space.

   hep-phEPJC(2018)·59 citations
8. 08*

   Theory of Radiative Electron Polarization in Strong Laser Fields

   D. Seipt🇬🇧 · D. Del Sorbo🇬🇧 · C. P. Ridgers🇬🇧 · A. G. R. Thomas🇺🇸

   Radiative polarization of electrons and positrons through the Sokolov-Ternov effect is important for applications in high-energy physics. Radiative spin-polarization is a manifestation of quantum radiation reaction affecting the spin-dynamics of electrons. We recently proposed that an analogue of the Sokolov-Ternov effect could occur in the strong electromagnetic fields of ultra-high-intensity lasers, which would result in a build-up of spin-polarization in femtoseconds. In this paper we develop a density matrix formalism for describing beam polarization in strong electromagnetic fields. We start by using the density matrix formalism to study spin-flips in non-linear Compton scattering and its dependence on the initial polarization state of the electrons. Numerical calculations show a radial polarization of the scattered electron beam in a circularly polarized laser, and we find azimuthal asymmetries in the polarization patterns for ultra-short laser pulses. A degree of polarization approaching 9 % is achieved after emitting just a single photon. We develop the theory by deriving a local constant crossed field approximation (LCFA) for the polarization density matrix, which is a generalization of the well known LCFA scattering rates. We find spin-dependent expressions that may be included in electromagnetic charged-particle simulation codes, such as particle-in-cell plasma simulation codes, using Monte-Carlo modules. In particular, these expressions include the spin-flip rates for arbitrary initial polarization of the electrons. The validity of the LCFA is confirmed by explicit comparison with an exact QED calculation of electron polarization in an ultrashort laser pulse.

   hep-phphysics.atom-phphysics.plasm-phPRA(2018)·89 citations
9. 09*

   Diffusion-model analysis of pPb and PbPb collisions at LHC energies

   P. Schulz🇩🇪 · G. Wolschin🇩🇪

   We present an analysis of centrality-dependent pseudorapidity distributions of produced charged hadrons in pPb and PbPb collisions at the LHC energy of sqrt{s_NN}=5.02 TeV, and of minimum-bias pPb collisions at 8.16 TeV within the nonequilibrium-statistical relativistic diffusion model (RDM). In a three-source approach, the role of the fragmentation sources is emphasized. Together with the Jacobian transformation from rapidity to pseudorapidity and the limiting fragmentation conjecture, these are essential for modeling the centrality dependence. For central PbPb collisions, a prediction at the projected FCC energy of sqrt{s_NN}=39 TeV is made.

   hep-phnucl-thMod.Phys.Lett.A(2018)·2 citations
10. 10*

    Split fermionic WIMPs evade direct detection

    Karim Ghorbani🇮🇷

    We consider a model with two gauge singlet fermionic WIMPs communicating with the SM particles by a singlet scalar mediator via a Higgs portal. While the light WIMP is stable and plays the role of the dark matter (DM) candidate, the heavy partner is a short-lived WIMP without contribution to the current DM relic density. Along with the coannihilation effects the heavy WIMP, acting as a mediator in $t$- and $u$-channel DM annihilation cross sections, has a significant effect in finding the viable parameter space against the direct detection constraints provided by XENON1t and LUX experiments. This is an extension to the minimal singlet fermionic DM model whose entire parameter space (except a resonance region) excluded by the latest direct detection experiments. It is found out that there are viable regions in the parameter space which evade direct detection upper bounds and respect the observed DM relic density by WMAP/Planck. We also found that the Fermi-LAT upper limits on the DM annihilation cross section into $b\bar{b}$ can exclude small regions of the viable parameter space which elude direct detection experiments. This model exemplifies a case within the WIMP paradigm whose DM candidate can escape direct detection experiments nontrivially. Such models are interesting to be studied in collider experiments like the LHC.

    hep-phhep-exJHEP(2018)·3 citations
11. 11*

    What is the right formalism to search for resonances? II. The pentaquark chain

    JPAC Collaboration: A. Pilloni🇺🇸 · J. Nys🇧🇪 · M. Mikhasenko🇩🇪 · M. Albaladejo🇪🇸 · C. Fernandez-Ramirez🇲🇽 · A. Jackura🇺🇸 · V. Mathieu🇺🇸 · N. Sherrill🇺🇸 · T. Skwarnicki🇺🇸 · A. P. Szczepaniak🇺🇸

    We discuss the differences between several partial-wave analysis formalisms used in the construction of three-body decay amplitudes involving fermions. Specifically, we consider the decay Lambda_b -> psi p K- , where the hidden charm pentaquark signal has been reported. We analyze the analytical properties of the amplitudes and separate kinematical and dynamical singularities. The result is an amplitude with the minimal energy dependence compatible with the S-matrix principles.

    hep-phhep-exnucl-thEPJC(2018)·16 citations
12. 12*

    Ruling out Critical Higgs Inflation?

    Isabella Masina🇮🇹

    We consider critical Higgs inflation, namely Higgs inflation with a rising inflection point at smaller field values than those of the plateau induced by the non-minimal coupling to gravity. It has been proposed that such configuration is compatible with the present CMB observational constraints on inflation, and also with primordial black hole production accounting for the totality or a fraction of the observed dark matter. We study the model taking into account the NNLO corrections to the Higgs effective potential: such corrections are extremely important to reduce the theoretical error associated to the calculation. We find that, in the 3 sigma window for the relevant low energy parameters, which are the strong coupling and the Higgs mass (the top mass follows by requiring an inflection point), the potential at the inflection point is so large (and so is the Hubble constant during inflation) that the present bound on the tensor-to-scalar ratio is violated. The model is viable only allowing the strong coupling to take its upper 3-4 sigma value. In our opinion, this tension shows that the model of critical Higgs inflation is likely to be not viable: neither inflation nor black holes as dark matter can be originated in this version of the model.

    hep-phastro-ph.COPRD(2018)·36 citations
13. 13*

    New physics effects in radiative leptonic $B_s$ decay

    Gauhar Abbas🇮🇳 · Ashutosh Kumar Alok🇮🇳 · Shireen Gangal🇺🇸

    There are several anomalous measurements in the decays induced by the quark level transition $b\to s{\mu }^{+}{\mu }^{-}$, which do not agree with the predictions of the Standard Model. These measurements could be considered as signatures of physics beyond the Standard Model. Working within the framework of effective field theory, several groups have performed global fits to all $b\to s{\mu }^{+}{\mu }^{-}$ data to identify the Lorentz structure of possible new physics. Many new physics scenarios have been suggested to explain the anomalies in the $b\to s{\mu }^{+}{\mu }^{-}$ sector. In this work, we investigate the impact of these new physics scenarios on the radiative leptonic decay of $B_s$ meson. We consider the branching ratio of this decay along with the ratio $R_{\gamma }$ of the differential distribution $B_s\to {\mu }^{+}{\mu }^{-}\gamma$ \& $B_s\to e^{+}{e}^{-}\gamma$ and the muon forward-backward asymmetry $A_{FB}$. We find that the predicted values of the branching ratio and $A_{FB}$ are close to the SM results for all allowed new physics solutions whereas some of the solutions allow large deviation in $R_{\gamma }$ from its SM prediction.

    hep-ph5 citations
14. 14*

    A quark-gluon plasma inspired model of the universe: Introduction and Inflation

    Melissa Mendes🇩🇪 · Giorgio Torrieri🇧🇷

    We explain how a $SU(N_c)$ gauge theory, decoupled from the standard model and with a high-lying strong coupling scale, can incorporate apparently unrelated cosmological features, such as Inflation and dark matter, using well-understood dynamics from Quark-Gluon Plasma Physics. In our scenario, the evolution of the universe is throughoutly hot: Inflation occurs due to the bulk viscosity peak during the mixed phase to deconfinement, while dark matter is composed of weakly interacting glueballs formed in the same phase. We parametrize the temperature dependence of the EoS and the viscosity expected from gauge theory, solve the Friedmann-Robertson-Walker (FRW) equations and compute the number of efoldings as a function of the free parameters of the model.

    hep-ph2 citations
15. 15*

    Spectroscopy and Decay properties of the charmonium

    Virendrasinh Kher🇮🇳 · Ajay Kumar Rai🇮🇳

    The mass spectra of charmonium are investigated using a Coulomb plus linear (Cornell) potential. Gaussian wave function in position space as well as in momentum space are employed to calculate the expectation value of potential and kinetic energy respectively. Various experimental states ($X(4660)(5^3{S}_1)$, $X(3872)(2^3{P}_1)$, $X(3900)(2^1{P}_1)$, $X(3915)(2^3{P}_0)$ and $X(4274)(3^3{P}_1)$ etc.) are assigned as charmonium states. We also study the Regge trajectories, pseudoscalar and vector decay constants, the Electric and Magnetic dipole transition rates and the annihilation decay width for charmonium states.

    hep-phCPC(2018)·64 citations
16. 16*

    Prospects of discovering stable double-heavy tetraquarks at a Tera-$Z$ factory

    Ahmed Ali🇩🇪 · Alexander Ya. Parkhomenko🇷🇺 · Qin Qin🇩🇪 · Wei Wang🇨🇳

    Motivated by a number of theoretical considerations, predicting the deeply bound double-heavy tetraquarks $T_{[\bar{u}\bar{d}]}^{\{bb\}}$, $T_{[\bar{u}\bar{s}]}^{\{bb\}}$ and $T_{[\bar{d}\bar{s}]}^{\{bb\}}$, we explore the potential of their discovery at Tera-$Z$ factories. Using the process $Z\to b\bar{b}b\bar{b}$, we calculate, employing the Monte Carlo generators MadGraph5$\_$aMC@NLO and Pythia6, the phase space configuration in which the~$bb$ pair is likely to fragment as a diquark. In a jet-cone, defined by an invariant mass interval $m_{bb}<M_{T_{[\bar{q}{\bar{q}}^{\prime }]}^{\{bb\}}}+\Delta M$, the sought-after tetraquarks $T_{[\bar{q}{\bar{q}}^{\prime }]}^{\{bb\}}$ as well as the double-bottom baryons,~${\Xi }_{bb}^{0,-}$, and ${\Omega }_{bb}^{-}$, can be produced. Using the heavy quark--diquark symmetry, we estimate $\mathcal{B}(Z\to T_{[\bar{u}\bar{d}]}^{\{bb\}}+\bar{b}\bar{b})=(1.4_{-0.5}^{+1.1})\times 10^{-6}$, and about a half of this for the $T_{[\bar{u}\bar{s}]}^{\{bb\}}$ and $T_{[\bar{d}\bar{s}]}^{\{bb\}}$. We also present an estimate of their lifetimes using the heavy quark expansion, yielding $\tau (T_{[\bar{q}{\bar{q}}^{\prime }]}^{\{bb\}})\simeq 800$~fs. Measuring the tetraquark masses would require decays, such as $T_{[\bar{u}\bar{d}]}^{\{bb\}-}\to B^{-}{D}^{-}{\pi }^{+}$, $T_{[\bar{u}\bar{d}]}^{\{bb\}-}\to J/\psi {\overline{K}}^0{B}^{-}$, $T_{[\bar{u}\bar{d}]}^{\{bb\}-}\to J/\psi K^{-}{\overline{B}}^0$, $T_{[\bar{u}\bar{s}]}^{\{bb\}-}\to {\Xi }_{bc}^0{\Sigma }^{-}$, and $T_{[\bar{d}\bar{s}]}^{\{bb\}0}\to {\Xi }_{bc}^0{\bar{\Sigma }}^0$, with subsequent decay chains in exclusive non-leptonic final states. We estimate a couple of the decay widths and find that the product branching ratios do not exceed~$10^{-5}$. Hence, a good fraction of these modes will be required for a discovery of $T_{[\bar{q}{\bar{q}}^{\prime }]}^{\{bb\}}$ at a Tera-$Z$ factory.

    hep-phhep-exPLB(2018)·68 citations
17. 17*

    Large-$N_c$ masses of light mesons from QCD sum rules for non-linear radial Regge trajectories

    S. S. Afonin🇷🇺 · T. D. Solomko🇷🇺

    The large-$N_c$ masses of light vector, axial, scalar and pseudoscalar mesons are calculated from QCD spectral sum rules for a particular ansatz interpolating the radial Regge trajectories. The ansatz includes a linear part plus exponentially degreasing corrections to the meson masses and residues. The form of corrections was proposed some time ago from consistency with analytical structure of Operator Product Expansion of the two-point correlation functions. Two solutions are found and compared with the experimental data.

    hep-phInt.J.Mod.Phys.A(2018)·5 citations
18. 18*

    Impact of recent COMPASS data on polarized parton distributions and structure functions

    M. Salimi-Amiri🇮🇷 · A. Khorramian🇮🇷 · H. Abdolmaleki🇮🇷 · F. I. Olness🇺🇸

    We perform a new extraction of polarized parton distribution functions (PPDFs) from the spin structure function experimental data in the fixed-flavor number scheme (FFNS). In this analysis, we include recent proton and deuteron spin structure functions obtained by the \texttt{COMPASS} collaboration. We examine the impact of the \texttt{new COMPASS} proton and deuteron data on the polarized parton densities and compare with results from our previous study (KATAO PPDFs), which used the Jacobi polynomial approach. We find the extracted PPDFs of the proton, neutron, and deuteron structure functions are in very good agreement with the experimental data. The results for extracted PPDFs are also compared with available theoretical models from the literature.

    hep-phhep-exPRD(2018)·12 citations
19. 19*

    First Results with HIJING++ on High-energy Heavy Ion Collisions

    Gábor Papp🇭🇺 · Gergely Gábor Barnaföldi🇭🇺 · Gábor Biró🇭🇺 · Miklos Gyulassy🇺🇸 · Szilveszter Harangozó🇭🇺 · Guoyang Ma🇨🇳 · Péter Lévai🇭🇺 · Xin-Nian Wang🇨🇳 · Ben-Wei Zhang🇨🇳

    We present preliminary results with HIJING++ (3.1.1) for identified hadron production in high-energy heavy ion collisions at LHC energies. The recently developed HIJING++ version is based on the latest version of PYTHIA8 and contains all the nuclear effects that have been included in the HIJING2.552, which will be improved by a new version of the shadowing parametrization and jet quenching module. Here, we summarize the structure and the speed gain due to parallelization of the new program code, also presenting some comparison between experimental data.

    hep-ph7 citations
20. 20*

    Gluon jet function at three loops in QCD

    Pulak Banerjee🇮🇳 · Prasanna K. Dhani🇮🇳 · V. Ravindran🇮🇳

    We present here the first result on the three-loop gluon jet function in perturbative QCD. Using the three-loop coefficient functions [1,2] for deep-inelastic scattering via the exchange of a virtual photon that couples to quarks or a scalar that couples to gluons and employing the KG equation, renormalization group invariance and factorization theorem, we obtain both the quark and the gluon jet functions up to the three-loop level. The former agrees with the recent result [3]. These jet functions being universal ingredients for many collider and decay processes, will play an important role in the phenomenological studies at the Large Hadron Collider.

    hep-phhep-exPRD(2018)·54 citations
21. 21*

    Neutrino Signatures in Primordial Non-Gaussianities

    Xingang Chen🇺🇸 · Yi Wang🇨🇳 · Zhong-Zhi Xianyu🇺🇸

    We study the cosmological collider phenomenology of neutrinos in an effective field theory. The mass spectrum of neutrinos and their characteristic oscillatory signatures in the squeezed limit bispectrum are computed. Both dS-covariant and slow-roll corrections are considered, so is the scenario of electroweak symmetry breaking during inflation. Interestingly, we show that the slow-roll background of the inflaton provides a chemical potential for the neutrino production. The chemical potential greatly amplifies the oscillatory signal and makes the signal observably large for heavy neutrinos without the need of fine tuning.

    hep-phastro-ph.COhep-thJHEP(2018)·110 citations
22. 22*

    Second-order Hydrodynamics in Next-to-Leading-Order QCD

    Jacopo Ghiglieri🇨🇭 · Guy D. Moore🇩🇪 · Derek Teaney🇺🇸

    We compute the hydrodynamic relaxation times ${\tau }_{\pi }$ and ${\tau }_j$ for hot QCD at next-to-leading order in the coupling with kinetic theory. We show that certain dimensionless ratios of second-order to first-order transport coefficients obey bounds which apply whenever a kinetic theory description is possible; the computed values lie somewhat above these bounds. Strongly coupled theories with holographic duals strongly violate these bounds, highlighting their distance from a quasiparticle description.

    hep-phnucl-thPRL(2018)·36 citations
23. 23*

    Anomaly Detection for Resonant New Physics with Machine Learning

    Jack H. Collins🇺🇸 · Kiel Howe🇺🇸 · Benjamin Nachman🇺🇸

    Despite extensive theoretical motivation for physics beyond the Standard Model (BSM) of particle physics, searches at the Large Hadron Collider (LHC) have found no significant evidence for BSM physics. Therefore, it is essential to broaden the sensitivity of the search program to include unexpected scenarios. We present a new model-agnostic anomaly detection technique that naturally benefits from modern machine learning algorithms. The only requirement on the signal for this new procedure is that it is localized in at least one known direction in phase space. Any other directions of phase space that are uncorrelated with the localized one can be used to search for unexpected features. This new method is applied to the dijet resonance search to show that it can turn a modest 2 sigma excess into a 7 sigma excess for a model with an intermediate BSM particle that is not currently targeted by a dedicated search.

    hep-phhep-exPRL(2018)·240 citations
24. 24*

    Median Statistics Estimate of the Galactic Rotational Velocity

    Tia Camarillo🇺🇸 · Pauline Dredger🇺🇸 · Bharat Ratra🇺🇸

    We compile a complete collection of 19 recent (since 2000) measurements of ${\Theta }_0$, the rotational velocity of the Milky Way at $R_0$ (the radial distance of the Sun from the Galactic center). These measurements use tracers that are believed to more accurately reflect the systematic rotation of the Milky Way. Unlike other recent compilations of ${\Theta }_0$, our collection includes only independent measurements. We find that these 19 measurements are distributed in a mildly non-Gaussian fashion and a median statistics estimate indicates ${\Theta }_0=220\pm 10$ km\,s${}^{-1}$ (2$\sigma$ error) as the most reliable summary, at $R_0=8.0\pm 0.3$ kpc (2$\sigma$ error).

    ↳ astro-ph.GAgr-qchep-phhep-thAstrophys.Space Sci.(2018)·15 citations
25. 25*

    Lagrangian formulation of the Palatini action

    SangChul Yoon🇰🇷

    We work on the Lagrangian formulation of the Palatini action. We find that we must assume the metric compatibility condition for the Palatini action to describe General Relativity, which condition should hold in quantization. We find that we must also assume one of the torsion zero condition or the tetrad compatibility condition. Our results will hold for any action in terms of the tetrad and the internal connection which describes General Relativity.

    ↳ gr-qchep-ph2 citations
26. 26*

    Gravitational wave echoes from strange stars

    Massimo Mannarelli🇮🇹 · Francesco Tonelli🇮🇹

    It has recently been claimed, with a $4.2\sigma$ significance level, that gravitational wave echoes at a frequency of about $72$ Hz have been produced in the GW170817 event. The merging of compact stars can lead to the emission of gravitational waves echoes if the post-merger object features a photon-sphere capable of partially trapping the gravitational waves. If the post-merger source is a black hole, a second internal reflection surface, associated to quantum effects near the black hole horizon, must be present to avoid the gravitational wave capture. Alternatively, gravitational wave echoes can be produced by ultracompact stars crossing the photon-sphere line in the mass-radius diagram during the neutron star merging. In this case, the second reflection surface is not needed. A recently proposed preliminary analysis using an incompressible (and so unphysical) equation of state suggests that gravitational wave echoes at a frequency of tens of Hz can be produced by an ultracompact star. Since strange stars are extremely compact, we examine the possibility that strange stars emit gravitational wave echoes at such a frequency. Using parameterized models of the equation of state of ultra-stiff quark matter we find that a strange star can emit gravitational wave echoes, but the corresponding frequencies are of the order of tens of kHz, thus not compatible with the $72$ Hz signal.

    ↳ gr-qchep-phPRD(2018)·41 citations
27. 27*

    Search for ${\rm Y}(1S,2S)\to Z_c^{+}{Z}_c^{(\prime )-}$ and $e^{+}{e}^{-}\to Z_c^{+}{Z}_c^{(\prime )-}$ at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV

    Belle Collaboration: S.Jia · C. P. Shen · C. Z. Yuan · I. Adachi · H. Aihara · S. Al Said · D. M. Asner · V. Aulchenko · T. Aushev · R. Ayad · V. Babu · I. Badhrees and 167 other authors

    The first search for $Z_c$ pair production in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays and in $e^{+}{e}^{-}$ annihilation at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV is conducted using data collected with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant signals are observed in any of the studied modes, and the 90\% credibility level upper limits on their product branching fractions in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays ($\mathcal{B}({\rm Y}(1S,2S)\to Z_c^{+}{Z}_c^{(\prime )-})\times \mathcal{B}(Z_c^{+}\to {\pi }^{+}+c\bar{c})$ ($c\bar{c}=J/\psi$, ${\chi }_{c1}(1P)$, $\psi (2S)$)) and the product of Born cross section and branching fraction for $e^{+}{e}^{-}\to Z_c^{+}{Z}_c^{(\prime )-}$ ($\sigma (e^{+}{e}^{-}\to Z_c^{+}{Z}_c^{(\prime )-})\times \mathcal{B}(Z_c^{+}\to {\pi }^{+}+c\bar{c})$) at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV are determined. Here, $Z_c$ refers to the $Z_c(3900)$ and $Z_c(4200)$ observed in the $\pi J/\psi$ final state, the $Z_{c1}(4050)$ and $Z_{c2}(4250)$ in the $\pi {\chi }_{c1}(1P)$ state, and the $Z_c(4050)$ and $Z_c(4430)$ in the $\pi \psi (2S)$ state.

    ↳ hep-exhep-phPRD(2018)·7 citations
28. 28*

    Systematics of the HAL QCD Potential at Low Energies in Lattice QCD

    Takumi Iritani🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵

    The $\Xi \Xi$ interaction in the ${}^1$S${}_0$ channel is studied to examine the convergence of the derivative expansion of the non-local HAL QCD potential at the next-to-next-to-leading order (N${}^2$LO). We find that (i) the leading order potential from the N${}^2$LO analysis gives the scattering phase shifts accurately at low energies, (ii) the full N${}^2$LO potential gives only small correction to the phase shifts even at higher energies below the inelastic threshold, and (iii) the potential determined from the wall quark source at the leading order analysis agrees with the one at the N${}^2$LO analysis except at short distances, and thus, it gives correct phase shifts at low energies. We also study the possible systematic uncertainties in the HAL QCD potential such as the inelastic state contaminations and the finite volume artifact for the potential and find that they are well under control for this particular system.

    ↳ hep-lathep-phnucl-thPRD(2019)·70 citations
29. 29*

    Anatomy of Eddington-like inversion methods in the context of dark matter searches

    Thomas Lacroix🇫🇷 · Martin Stref🇫🇷 · Julien Lavalle🇫🇷

    Irrespective of the dark matter (DM) candidate, several potentially observable signatures derive from the velocity distribution of DM in halos, in particular in the Milky Way (MW) halo. Examples include direct searches for weakly-interacting massive particles (WIMPs), $p$-wave suppressed or Sommerfeld-enhanced annihilation signals, microlensing events of primordial black holes (PBHs), {\em etc}. Most current predictions are based on the Maxwellian approximation which is not only theoretically inconsistent in bounded systems, but also not supported by cosmological simulations. A more consistent method sometimes used in calculations for direct WIMP searches relies on the so-called Eddington inversion method, which relates the DM phase-space distribution function (DF) to its mass density profile and the total gravitational potential of the system. Originally built upon the isotropy assumption, this method can be extended to anisotropic systems. We investigate these inversion methods in the context of Galactic DM searches, motivated by the fact that the MW is a strongly constrained system, and should be even more so with the ongoing Gaia survey. We still draw conclusions that apply to the general case. In particular, we illustrate how neglecting the radial boundary of the DM halo leads to theoretical inconsistencies. We also show that several realistic configurations of the DM halo and the MW baryonic content entail ill-defined DFs, significantly restricting the configuration space over which these inversion methods can apply. We propose consistent solutions to these issues. Finally, we compute several observables inferred from constrained Galactic mass models relevant to DM searches (WIMPs or PBHs), {\em e.g.} moments and inverse moments of the DM speed and relative speed distributions.

    ↳ astro-ph.GAastro-ph.COhep-phJCAP(2018)·68 citations
30. 30*

    Back-Reaction of Gravitational Waves Revisited

    Robert Brandenberger🇨🇦 · Tomo Takahashi🇯🇵

    We study the back-reaction of gravitational waves in early universe cosmology, focusing both on super-Hubble and sub-Hubble modes. Sub-Hubble modes lead to an effective energy density which scales as radiation. Hence, the relative contribution of such gravitational waves to the total energy density is constrained by big bang nucleosynthesis. This leads to an upper bound on the tensor spectral slope n_T which also depends on the tensor to scalar ratio r. Super-Hubble modes, on the other hand, lead to a negative contribution to the effective energy density, and to an equation of state of curvature. Demanding that the early universe is not dominated by the back-reaction leads to constraints on the gravitational wave spectral parameters which are derived.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2018)·10 citations
31. 31*

    Anisotropy of dark matter velocity distribution

    Keiko I. Nagao🇯🇵

    Direct detection of dark matter with directional sensitivity has the potential to discriminate the dark matter velocity distribution. Especially, it will be suitable to discriminate isotropic distribution from anisotropic one. Analyzing data produced with Monte-Carlo simulation, required conditions for the discrimination is estimated. If energy threshold of detector is optimized, $O(10^3-10^4)$ event number is required to discriminate the anisotropy.

    ↳ astro-ph.IMastro-ph.COhep-ph0 citations
32. 32*

    Can pion spectra in Pb+Pb collisions at CERN SPS energies be described by those in p+p reactions and energy-momentum conservation ? Rapidity distributions of pions in p+p and Pb+Pb collisions at CERN SPS energies

    Andrzej Rybicki🇵🇱 · Antoni Szczurek🇵🇱 · Miroslaw Kielbowicz🇵🇱 · Antoni Marcinek🇵🇱 · Vitalii Ozvenchuk🇵🇱 · Łukasz Rozpłochowski🇵🇱

    The centrality dependence of rapidity distributions of pions in Pb+Pb reactions can be understood by imposing local energy-momentum conservation in the longitudinal "fire-streaks" of excited matter. With no tuning nor adjustment to the experimental data, the rapidity distribution of pions produced by the fire-streak which we obtained from Pb+Pb collisions reproduces the shape of the experimental pion rapidity distribution in p+p interactions, measured by the NA49 Collaboration at the same energy. The observed difference in the absolute normalization of this distribution can be explained by the difference in the overall energy balance, induced by baryon stopping and strangeness enhancement phenomena occurring in heavy ion collisions. We estimate the latter effects using a collection of SPS experimental data on ${\pi }^{\pm }$, $K^{\pm }$, net $p$, and $n$ production in p+p and Pb+Pb reactions. Implications of the above findings are discussed.

    ↳ nucl-thhep-exhep-phPRC(2019)·6 citations
33. 33*

    Heavy physics contributions to neutrinoless double beta decay from QCD

    A. Nicholson🇺🇸 · E. Berkowitz🇩🇪 · H. Monge-Camacho🇺🇸 · D. Brantley🇺🇸 · N. Garron🇬🇧 · C.C. Chang🇺🇸 · E. Rinaldi🇺🇸 · M.A. Clark🇺🇸 · B. Joo🇺🇸 · T. Kurth🇺🇸 · B. Tiburzi🇺🇸 · P. Vranas🇺🇸 · A. Walker-Loud🇺🇸

    Observation of neutrinoless double beta decay, a lepton number violating process that has been proposed to clarify the nature of neutrino masses, has spawned an enormous world-wide experimental effort. Relating nuclear decay rates to high-energy, beyond the Standard Model (BSM) physics requires detailed knowledge of non-perturbative QCD effects. Using lattice QCD, we compute the necessary matrix elements of short-range operators, which arise due to heavy BSM mediators, that contribute to this decay via the leading order ${\pi }^{-}\to {\pi }^{+}$ exchange diagrams. Utilizing our result and taking advantage of effective field theory methods will allow for model-independent calculations of the relevant two-nucleon decay, which may then be used as input for nuclear many-body calculations of the relevant experimental decays. Contributions from short-range operators may prove to be equally important to, or even more important than, those from long-range Majorana neutrino exchange.

    ↳ nucl-thhep-lathep-phnucl-exPRL(2018)·102 citations
34. 34*

    Search for a Non-Relativistic Component in the Spectrum of Cosmic Rays at Earth

    J.I. Collar🇺🇸

    Dark matter particles gravitationally bound to our galaxy should exhibit a characteristic speed distribution limited by their escape velocity at the position of the Earth ($v_{esc}\simeq$ 550 km/s). An ongoing search for anomalous cosmic rays at Earth, kinematically similar to cold dark matter, is described. The technique can discriminate between these and known slow-moving particles such as neutrons, would be sensitive to telltale signatures from presently unexplored candidates, and offers the possibility of identifying the mediating type of interaction (nuclear vs. electron recoils). Studies of background identification and abatement in a shallow underground site are presented. The expected reach of the method is discussed, and illustrated by obtaining the first limits for dark matter particles lighter than 100 MeV/c${}^2$ interacting via nuclear recoils.

    ↳ astro-ph.COastro-ph.IMhep-exhep-phPRD(2018)·93 citations
35. 35*

    Pole N-flation

    Mafalda Dias🇩🇪 · Jonathan Frazer🇩🇪 · Ander Retolaza🇩🇪 · Marco Scalisi🇧🇪 · Alexander Westphal🇩🇪

    A second order pole in the scalar kinetic term can lead to a class of inflation models with universal predictions referred to as pole inflation or $\alpha$-attractors. While this kinetic structure is ubiquitous in supergravity effective field theories, realising a consistent UV complete model in e.g. string theory is a non-trivial task. For one, one expects quantum corrections arising in the vicinity of the pole which may spoil the typical attractor dynamics. As a conservative estimate of the range of validity of supergravity models of pole inflation we employ the weak gravity conjecture (WGC). We find that this constrains the accessible part of the inflationary plateau by limiting the decay constant of the axion partner. For the original single complex field models, the WGC does not even allow the inflaton to reach the inflationary plateau region. We analyze if evoking the assistance of $N$ scalar fields from the open string moduli helps addressing these problems. Pole $N$-flation could improve radiative control by reducing the required range of each individual field. However, the WGC bound prohibiting pole inflation for a single such field persists even for a collective motion of $N$ such scalars if we impose the sublattice WGC. Finally, we outline steps towards an embedding of pole N-flation in type IIB string theory on fibred Calabi-Yau manifolds.

    ↳ hep-thastro-ph.COhep-phJHEP(2019)·39 citations
36. 36*

    Quintessential Affleck-Dine baryogenesis with non-minimal couplings

    Dario Bettoni🇩🇪 · Javier Rubio🇩🇪

    We present a novel Affleck-Dine scenario for the generation of the observed baryon asymmetry of the Universe based on the non-trivial interplay between quintessential inflationary models containing a kinetic dominated post-inflationary era and a non-minimally coupled $U(1)$ field with a weakly broken $B-L$ symmetry. The non-minimal coupling to gravity renders heavy the Affleck-Dine field during inflation and avoids the generation of isocurvature fluctuations. During the subsequent kinetic era the Ricci scalar changes sign and the effective mass term of the Affleck-Dine field becomes tachyonic. This allows the field to dynamically acquire a large expectation value. The symmetry of the Affleck-Dine potential is automatically restored at the onset of radiation domination, when the Ricci scalar approximately equals zero. This inverse phase transition results in the coherent oscillation of the scalar field around the origin of its effective potential. The rotation of the displaced Affleck-Dine field in the complex plane generates a non-zero $B-L$ asymmetry which can be eventually converted into a baryon asymmetry via the usual transfer mechanisms.

    ↳ astro-ph.COgr-qchep-phPLB(2018)·49 citations
37. 37*

    Vibrational modes of Q-balls

    A. Kovtun🇷🇺 · E. Nugaev🇷🇺 · A. Shkerin🇨🇭

    We study linear perturbations of classically stable Q-balls in theories admitting analytic solutions. Although the corresponding boundary value problem is non-Hermitian, the analysis of perturbations can also be performed analytically in certain regimes. We show that in theories with the flat potential, large Q-balls possess soft excitations. We also find a specific vibrational mode for Q-balls with a near-critical charge, where the perturbation theory for excitations can be developed. Comparing with the results on stability of Q-balls provides additional checks of our analysis.

    ↳ hep-thhep-phPRD(2018)·23 citations
38. 38*

    Gamma-Ray Burst Optical Afterglows with Two-Component Jets: Polarization Evolution Revisited

    Mi-Xiang Lan🇨🇳 · Xue-Feng Wu🇨🇳 · Zi-Gao Dai🇨🇳

    Gamma-ray bursts (GRBs) have been widely argued to originate from binary compact object mergers or core collapses of massive stars. Jets from these systems may have two components, an inner, narrow sub-jet and an outer, wider sub-jet. Such a jet subsequently interacts with its ambient gas, leading to a reverse shock (RS) and a forward shock (FS). The magnetic field in the narrow sub-jet is very likely to be mixed by an ordered component and a random component during the afterglow phase. In this paper, we calculate light curves and polarization evolution of optical afterglows with this mixed magnetic field in the RS region of the narrow sub-jet in a two-component jet model. The resultant light curve has two peaks: an early peak arises from the narrow sub-jet and a late-time rebrightening is due to the wider sub-jet. We find the polarization degree (PD) evolution under such a mixed magnetic field confined in the shock plane is very similar to that under the purely ordered magnetic field condition. The two-dimensional `mixed' magnetic fields confined in the shock plane are essentially the ordered magnetic fields only with different configurations. The position angle (PA) of the two-component jet can change gradually or abruptly by $90^{\circ }$. In particular, an abrupt $90^{\circ }$ change of the PA occurs when the PD changes from its decline phase to rise phase.

    ↳ astro-ph.HEhep-phApJ(2018)·21 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.